Elements responsible for hormonal control and tissue specificity of L-type pyruvate kinase gene expression in transgenic mice. L-type pyruvate kinase (L-PK) is a key enzyme of the glycolytic pathway specifically expressed in the liver and, to a lesser degree, in the small intestine and kidney. One important characteristic of L-PK gene expression is its strong activation by glucose and insulin and its complete inhibition by fasting or glucagon treatment. Having previously established that the entire rat L-PK gene plus 3.2 kbp of 5'-flanking region functions in mice in a tissue-specific and hormonally regulated manner, various deletions of these 3.2 kbp of 5'-flanking regions were tested in transgenic animals to map the cis-acting elements involved in transcriptional gene regulation. Our experiments indicate that the proximal region between -183 and +11 confers tissue specificity and contains all the information necessary for dietary and hormonal control of L-PK gene expression in vivo. We found, however, that the transcriptional activity generated by this proximal promoter fragment can be modulated by distal sequences in a tissue-specific manner. (i) Sequences between bp -183 and -392 seem to play a dual role in the liver and small intestine; they induce L-PK expression in the liver but repress it in the small intestine. (ii) Sequences from bp -392 up to -1170 do not seem to have any additional effect on promoter activity. (iii) Between bp -1170 and -2080, we found a putative extinguisher whose transcriptional inhibitory effect is much more marked in the small intestine than in the liver. (iv) Finally, between bp -2080 and -3200, we identified an activating sequence required for full expression of the gene in the liver.


The osmotic integrity of the yeast cell requires a functional PKC1 gene product. Seven temperature-sensitive cell lysis (cly) mutant strains of Saccharomyces cerevisiae were isolated which lyse at the restrictive temperature on hypotonic but not on osmotically supported medium. The seven mutants fell into four complementation groups, CLY12 to CLY15. The wild-type CLY15 gene was isolated by complementation of the cly15 temperature-sensitive growth defect. Sequence analysis revealed that the complementing DNA fragment encoded a partial PKC1 gene, which has previously been isolated as an S. cerevisiae homolog of mammalian protein kinase C genes (D. E. Levin, F. O. Fields, R. Kunisawa, J. M. Bishop, and J. Thorner, Cell 62:213-224, 1990). Subsequent genetic analysis showed that CLY15 and PKC1 represent identical loci in the yeast genome. A truncated PKC1 gene encoding only the predicted catalytic domain of Pkc1p was able to complement pkc1 mutant strains. Similar to what has been reported recently (D. E. Levin and E. Bartlett-Heubusch, J. Cell Biol. 116:1221-1229, 1992), we observed that cells deleted for the PKC1 gene are viable when grown on osmotically stabilized medium but are osmotically fragile and lyse rapidly after a shift to hypotonic medium. As shown by light and electron microscopic examinations, the delta pkc1 strain exhibits many cells with a strongly elongated bud or chains of incompletely budded cells when grown on solid medium.


Phylogenetic footprinting reveals a nuclear protein which binds to silencer sequences in the human gamma and epsilon globin genes. Tissue- and developmental stage-specific expression of the human beta-like globin genes is regulated by a combination of ubiquitous and erythroid-restricted trans factors that bind to cis elements near each of the five active genes. Additional interactions of these cis and trans factors with sequences located in the far 5' end of the cluster occur by as yet obscure mechanisms. Because of the complexity of this regulatory puzzle, precise identification of the determinants that control hemoglobin switching has proven difficult. Phylogenetic footprinting is an evolutionary approach to this problem which is based on the supposition that the basic mechanisms of switching are conserved throughout mammalian phylogeny. Alignment of the 5' flanking regions of the gamma genes of several species allows the identification of footprints of 100% conserved sequence. We have now tested oligomers spanning 13 such phylogenetic footprints and find that 12 are bound by nuclear proteins. One conserved element located at -1086 from the gamma genes exhibits repressor activity in transient transfection studies. The protein that binds this element, CSBP-1 (conserved sequence-binding protein 1), also binds at three sites within a silencer element upstream from the epsilon globin gene. Further analysis reveals that the CSBP-1 binding activity is identical to that of a recently cloned zinc finger protein that has been shown to act as a repressor in other systems. The binding of CSPB-1 to silencer sequences in the epsilon and gamma globin genes may be important in the stage-specific silencing of these genes.


The EBNA2-related resistance towards alpha interferon (IFN-alpha) in Burkitt's lymphoma cells effects induction of IFN-induced genes but not the activation of transcription factor ISGF-3. Transfection of a plasmid encoding the Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2) gene confers resistance to the antiproliferative effect of alpha interferon (IFN-alpha) in EBV-negative U968 cells (P. Aman and A. von Gabain, EMBO J. 9:147-152, 1990). We studied the expression of IFN-stimulated genes (ISGs) in two pairs of Burkitt's lymphoma cell lines, differing in the expression of the putative immortalizing gene of EBV, EBNA2. In EBNA2-expressing cells, the induction of four ISGs by IFN-alpha was strongly reduced or, in some cases, abolished. Chloramphenicol acetyltransferase reporter gene constructs containing different IFN-stimulated response elements were transfected into EBNA2-negative and EBNA2-positive cells. Induction of chloramphenicol acetyltransferase activity by IFN was impaired in EBNA2-positive cells. Also, a reporter gene construct driven by an IFN-gamma-sensitive promoter element was affected. However, as revealed by gel shift assays, EBNA2-positive and EBNA2-negative cells exhibited a nearly identical pattern of IFN-stimulated response element-binding proteins. Most important, activation of the factor ISGF-3, which previously has been shown to be required and sufficient for transcriptional activation of IFN-induced genes, was not inhibited in IFN-resistant cells expressing EBNA2. The mechanism of the EBNA2-related IFN resistance seems to be distinct both from the resistance mediated by hepatitis virus and adenovirus gene products and from the IFN resistance in Daudi cell variants. In these three cases, the transcriptional block of IFN-induced genes is due to inhibition of ISGF-3 activation and binding. Our data suggest that the EBNA2-related IFN resistance in Burkitt's lymphoma cells acts downstream of the activation of ISGF-3.


The 70-kilodalton adenylyl cyclase-associated protein is not essential for interaction of Saccharomyces cerevisiae adenylyl cyclase with RAS proteins. In the yeast Saccharomyces cerevisiae, adenylyl cyclase is regulated by RAS proteins. We show here that the yeast adenylyl cyclase forms at least two high-molecular-weight complexes, one with the RAS protein-dependent adenylyl cyclase activity and the other with the Mn(2+)-dependent activity, which are separable by their size difference. The 70-kDa adenylyl cyclase-associated protein (CAP) existed in the former complex but not in the latter. Missense mutations in conserved motifs of the leucine-rich repeats of the catalytic subunit of adenylyl cyclase abolished the RAS-dependent activity, which was accompanied by formation of a very high molecular weight complex having the Mn(2+)-dependent activity. Contrary to previous results, disruption of the gene encoding CAP did not alter the extent of RAS protein-dependent activation of adenylyl cyclase, while a concomitant decrease in the size of the RAS-responsive complex was observed. These results indicate that CAP is not essential for interaction of the yeast adenylyl cyclase with RAS proteins even though it is an inherent component of the RAS-responsive adenylyl cyclase complex.


Functional interference between the ubiquitous and constitutive octamer transcription factor 1 (OTF-1) and the glucocorticoid receptor by direct protein-protein interaction involving the homeo subdomain of OTF-1. The ubiquitous and constitutive octamer transcription factor OTF-1 (Oct 1) is the target of positive regulation by the potent herpes simplex virus trans-activator VP16, which forms a complex with the homeodomain of OTF-1. Here we present evidence that the glucocorticoid receptor can negatively regulate OTF-1 function by a mechanism that is independent of DNA binding. In vivo-expressed glucocorticoid receptor inhibited in a hormone-dependent manner activation of a minimal promoter construct carrying a functional octamer site. Moreover, expression of the receptor in vivo resulted in hormone-dependent repression of OTF-1-dependent DNA-binding activity in nuclear extract. In vitro, the DNA-binding activity of partially purified OTF-1 was repressed following incubation with purified glucocorticoid receptor. Cross-linking and immunoprecipitation experiments indicated that the functional interference may be due to a strong association between these two proteins in solution. Finally, preliminary evidence indicates that the homeo subdomain of OTF-1 that directs formation of a complex with VP16 may also be critical for interaction with the glucocorticoid receptor. Thus, OTF-1 is a target for both positive and negative regulation by protein-protein interaction. Moreover, the functional interference between OTF-1 and the glucocorticoid receptor represents a novel regulatory mechanism in the cross-coupling of signal transduction pathways of nuclear receptors and constitutive transcription factors.


Cooperative binding of the Xenopus RNA polymerase I transcription factor xUBF to repetitive ribosomal gene enhancers. Upstream binding factor (UBF) is a DNA-binding transcription factor implicated in ribosomal gene promoter and enhancer function in vertebrates. UBF is unusual in that it has multiple DNA-binding domains with homology to high-mobility-group (HMG) nonhistone chromosomal proteins 1 and 2. However, a recognizable DNA consensus sequence for UBF binding is lacking. In this study, we have used gel retardation and DNase I footprinting to examine Xenopus UBF (xUBF) binding to Xenopus laevis ribosomal gene enhancers. We show that UBF has a minimum requirement for about 60 bp of DNA, the size of the short enhancer variant in X. laevis. Stronger UBF binding occurs on the longer enhancer variant (81 bp) and on multiple enhancers linked head to tail. In vivo, Xenopus ribosomal gene enhancers exist in blocks of 10 alternating 60- and 81-bp repeats within the intergenic spacer. In vitro, UBF binds cooperatively to probes with 10 enhancers, with five intermediate complexes observed in titration experiments. This suggests that, on average, one UBF dimer binds every two enhancers. A single UBF dimer can produce a DNase I footprint ranging in size from approximately 30 to about 115 bp on enhancer probes of different lengths. This observation is consistent with the hypothesis that multiple DNA-binding domains or subdomains within UBF bind independently, forming more-stable interactions on longer probes.


A transcriptionally active form of GAL4 is phosphorylated and associated with GAL80. The GAL4 activator and GAL80 repressor proteins regulate the expression of yeast genes in response to galactose. A complex of the two proteins isolated from glucose-grown cells is inactive in an in vitro transcription reaction but binds DNA and blocks activation by the GAL4-VP16 chimeric activator. The complex purified from galactose-grown cells contains a mixture of phosphorylated and unphosphorylated forms of GAL4. The galactose-induced form of GAL4 activates in vitro transcription to levels similar to those seen with GAL4-VP16. The induced GAL4 complex is indistinguishable in size and apparent shape from the uninduced complex, consistent with a continued association with GAL80. These results confirm in vivo analyses that correlate GAL4 phosphorylation with galactose induction and support a model of transcriptional activation that does not require GAL80 dissociation.


Existence of different Fos/Jun complexes during the G0-to-G1 transition and during exponential growth in mouse fibroblasts: differential role of Fos proteins. We have determined the different Fos/Jun complexes present in Swiss 3T3 cells either following serum stimulation of quiescent cells or during exponential growth by immunoprecipitation analyses. We have shown that while c-Fos is the major Fos protein associated with the Jun proteins (c-Jun, JunB, and JunD) soon after serum stimulation, at later times Fra-1 and Fra-2 are the predominant Fos proteins associated with the different Jun proteins. During exponential growth, the synthesis of Fra-1 and Fra-2 is maintained at a significant level, in contrast to c-Fos and FosB, which are expressed at very low or undetectable levels. Consequently, Fra-1 and Fra-2 are the main Fos proteins complexed with the Jun proteins in asynchronously growing cells. To determine whether the Fos proteins are differentially required during the G0-to-G1 transition and exponential growth for the entrance into S phase, we microinjected affinity-purified antibodies directed against c-Fos, FosB, Fra-1, and Fra-2. We have found that while the activities of c-Fos and FosB are required mostly during the G0-to-G1 transition, Fra-1 and Fra-2 are involved both in the G0-to-G1 transition and in asynchronous growth.


Effects of histone acetylation on chromatin topology in vivo. Recently a model for eukaryotic transcriptional activation has been proposed in which histone hyperacetylation causes release of nucleosomal supercoils, and this unconstrained tension in turn stimulates transcription (V. G. Norton, B. S. Imai, P. Yau, and E. M. Bradbury, Cell 57:449-457, 1989; V. G. Norton, K. W. Marvin, P. Yau, and E. M. Bradbury, J. Biol. Chem. 265:19848-19852, 1990). These studies analyzed the effect of histone hyperacetylation on the change in topological linking number which occurs during nucleosome assembly in vitro. We have tested this model by determining the effect of histone hyperacetylation on the linking number change which occurs during assembly in vivo. We find that butyrate treatment of cells infected with simian virus 40 results in hyperacetylation of the histones of the extracted viral minichromosome as expected. However, the change in constrained supercoils of the minichromosome DNA is minimal, a result which is inconsistent with the proposed model. These results indicate that the proposed mechanism of transcriptional activation is unlikely to take place in the cell.


A 40-kilodalton protein binds specifically to an upstream sequence element essential for muscle-specific transcription of the human myoglobin promoter. To define transcriptional control elements responsible for muscle-specific expression of the human myoglobin gene, we performed mutational analysis of upstream sequences (nucleotide positions -373 to +7 relative to the transcriptional start site) linked to a firefly luciferase gene. Transient expression assays in avian and mammalian cells indicated that a CCCACCCCC (CCAC box) sequence (-223 to -204) is necessary for muscle-specific transcription directed either by the native myoglobin promoter or by a heterologous minimal promoter linked to the myoglobin upstream enhancer region. A putative MEF2-like site (-160 to -169) was likewise necessary for full transcriptional activity in myotubes. Mutations within either of two CANNTG (E-box) motifs (-176 to -148) had only minimal effects on promoter function. We identified and partially purified from nuclear extracts a 40-kDa protein (CBF40) that binds specifically to oligonucleotides containing the CCAC box sequence. A mutation of the CCAC box that disrupted promoter function in vivo also impaired binding of CBF40 in vitro. These data suggest that cooperative interactions between CBF40 and other factors including MEF-2 are required for expression of the human myoglobin gene in skeletal muscle.


Identification of a human cDNA encoding a protein that is structurally and functionally related to the yeast adenylyl cyclase-associated CAP proteins. The adenylyl cyclases of both Saccharomyces cerevisiae and Schizosaccharomyces pombe are associated with related proteins named CAP. In S. cerevisiae, CAP is required for cellular responses mediated by the RAS/cyclic AMP pathway. Both yeast CAPs appear to be bifunctional proteins: the N-terminal domains are required for the proper function of adenylyl cyclase, while loss of the C-terminal domains results in morphological and nutritional defects that appear to be unrelated to the cAMP pathways. Expression of either yeast CAP in the heterologous yeast suppresses phenotypes associated with loss of the C-terminal domain of the endogenous CAP but does not suppress loss of the N-terminal domain. On the basis of the homology between the two yeast CAP proteins, we have designed degenerate oligonucleotides that we used to detect, by the polymerase chain reaction method, a human cDNA fragment encoding a CAP-related peptide. Using the polymerase chain reaction fragment as a probe, we isolated a human cDNA clone encoding a 475-amino-acid protein that is homologous to the yeast CAP proteins. Expression of the human CAP protein in S. cerevisiae suppresses the phenotypes associated with loss of the C-terminal domain of CAP but does not suppress phenotypes associated with loss of the N-terminal domain. Thus, CAP proteins have been structurally and, to some extent, functionally conserved in evolution between yeasts and mammals.


Human DNA-activated protein kinase phosphorylates serines 15 and 37 in the amino-terminal transactivation domain of human p53. Human DNA-PK is a nuclear, serine/threonine protein kinase that, when activated by DNA, phosphorylates several DNA-binding substrates, including the tumor suppressor protein p53. To identify which p53 residues are phosphorylated, we examined DNA-PK's ability to phosphorylate synthetic peptides corresponding to human p53 sequences. Serines 15 and 37 in the amino-terminal transactivation domain of human p53, and serines 7 and 18 of mouse p53, were phosphorylated by DNA-PK in the context of synthetic peptides. Other serines in these p53 peptides, and serines in other p53 peptides, including peptides containing the serine 315 p34cdc2 site and the serine 392 casein kinase II site, were not recognized by DNA-PK or were phosphorylated less efficiently. Phosphorylation of the conserved serine 15 in human p53 peptides depended on the presence of an adjacent glutamine, and phosphorylation was inhibited by the presence of a nearby lysine. Phosphorylation of recombinant wild-type mouse p53 was inhibited at high DNA concentrations, suggesting that DNA-PK may phosphorylate p53 only when both are bound to DNA at nearby sites. Our study suggests that DNA-PK may have a role in regulating cell growth and indicates how phosphorylation of serine 15 in DNA-bound p53 could alter p53 function.


Functional asymmetry of the regions juxtaposed to the membrane-binding sequence of polyomavirus middle T antigen. The functional importance of the two clusters of positively charged amino acids which flank the hydrophobic membrane-anchoring sequence of polyomavirus middle T (mT) protein has been investigated by using site-directed mutagenesis. A clear asymmetry was apparent. No effect on transformation was seen following multiple alterations or complete removal of the cluster at the carboxyl end of the protein. In contrast, a single substitution replacing the first arginine amino terminal to the hydrophobic stretch with glutamic acid, but not with lysine, histidine, or methionine, produced a partially transformation-defective mutant with a novel phenotype. This mutant failed to confer anchorage-independent growth on F111 established rat embryo fibroblasts but induced foci with altered morphology compared with wild-type mT. Biochemical studies on this mutant revealed that F111 clones expressing levels of mutant mT equivalent to those of wild-type controls showed a 65% reduction in pp60c-src activation and an 87% reduction in mT-associated phosphatidylinositol 3-kinase activity. However, F111 clones expressing seven times more mutant mT than did wild-type controls showed equal or greater levels of kinase activities yet remained incompletely transformed. Possible mechanisms involving this transformation-sensitive region of mT are discussed.


Conformational activation of a basic helix-loop-helix protein (MyoD1) by the C-terminal region of murine HSP90 (HSP84). A murine cardiac lambda gt11 expression library was screened with an amphipathic helix antibody, and a recombinant representing the C-terminal 194 residues of murine HSP90 (HSP84) was cloned. Both recombinant and native HSP90s were then found to rapidly convert a basic helix-loop-helix protein (MyoD1) from an inactive to an active conformation, as assayed by sequence-specific DNA binding. The conversion process involves a transient interaction between HSP90 and MyoD1 and does not result in the formation of a stable tertiary complex. Conversion does not require ATP and occurs stoichiometrically in a dose-dependent fashion. HSP90 is an abundant, ubiquitous, and highly conserved protein present in most eukaryotic cells. These results provide direct evidence that HSP90 can affect the conformational structure of a DNA-binding protein.


The growth-stimulatory effect of simian virus 40 T antigen requires the interaction of insulinlike growth factor 1 with its receptor. We have used a plasmid expressing a temperature-sensitive (ts) mutant of simian virus 40 (SV40) T antigen, stably transfected into 3T3 cells, to study the role of insulinlike growth factor 1 (IGF-1) and its receptor in T-antigen-mediated growth. While 3T3 cells do not grow in serum-free medium, in 1% serum, or with the sole addition of either platelet-derived growth factor (PDGF) or IGF-1, cells expressing the tsA T antigen (BALB 58 cells) grow at 34 degrees C in either PDGF or 1% serum but not in IGF-1. At the restrictive temperature (39.6 degrees C), these cells can only grow in 10% serum. We show that BALB 58 cells, at 34 degrees C, have a markedly increased expression of IGF-1 and IGF-1 mRNA and that their growth in 1% serum (at 34 degrees C) is inhibited by an antisense oligodeoxynucleotide to the IGF-1 receptor RNA. When this tsA plasmid is stably transfected into cells constitutively overexpressing the human IGF-1 receptor cDNA, the resulting cell lines show a constitutively phosphorylated IGF-1 receptor and grow in serum-free medium at 34 degrees C (but not at 39.6 degrees C). A functional SV40 T antigen also increases the expression of a plasmid in which the reporter luciferase gene is under the control of a rat IGF-1 promoter. We conclude (i) that the SV40 T antigen induces the expression of IGF-1 and IGF-1 mRNA, at least in part by a transcriptional mechanism, thus altering the growth factors requirements, and (ii) that, in BALB/c3t3 cells, the SV40 T antigen necessitates a functional IGF-1 receptor for its growth-stimulating effect in low serum (or PDGF).


Raf-1 protein kinase is an integral component of the oncogenic signal cascade shared by epidermal growth factor and platelet-derived growth factor. Our recent studies with cell mutants indicate that a cascade shared by the epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) signals exists in NRK cells and mediates oncogenic signals induced by many oncogenes (A. Masuda, S. Kizaka-Kondoh, H. Miwatani, Y. Terada, H. Nojima, and H. Okayama, New Biol. 4:489-503, 1992). We have employed the antisense RNA technique to investigate possible involvement of Raf-1 kinase in this signal transduction cascade. NRK cell clones highly reduced in the Raf-1 production are generated by the expression of a c-raf-1 antisense RNA. They have no apparent growth defects and retain proper mitotic responses to growth factors but are refractory to transformation by EGF or PDGF plus transforming growth factor beta, v-erbB, v-fms, v-K-ras, v-mos, v-fos, v-src, simian virus 40 large T, and polyomavirus middle T but not by v-raf or adenovirus E1A. These results not only support our model for the oncogenic signal cascade but also lead to the conclusion that Raf-1 protein kinase is a downstream component of this oncogenic signal cascade shared by EGF and PDGF.


Definition of the transcriptional activation domain of recombinant 43-kilodalton USF. The cellular transcription factor USF is involved in the regulation of both cellular and viral genes and consists of 43- and 44-kDa polypeptides which independently show site-specific DNA binding. Cloning of the corresponding cDNA revealed that the 43-kDa polypeptide (USF43) is a member of the basic (B)-helix-loop-helix (HLH)-leucine zipper (LZ) family of proteins and provided a means for its functional dissection. Initial structure-function studies revealed that the HLH and LZ regions are both important for USF43 oligomerization and DNA binding. The studies presented here have focused on the determination of domains that contribute to transcriptional activation in vitro and show that (i) both a small region close to the N terminus and a region between residues 93 and 156 contribute strongly to transcriptional activation, (ii) full activation depends on the presence of both domains, (iii) the B-HLH-LZ region has no intrinsic activation potential but DNA binding is absolutely required for transcriptional activation, and (iv) the B-HLH-LZ region can be replaced by the Gal4 DNA binding domain without loss of activation potential.


A Drosophila rotund transcript expressed during spermatogenesis and imaginal disc morphogenesis encodes a protein which is similar to human Rac GTPase-activating (racGAP) proteins. The rotund (rn) locus of Drosophila melanogaster at cytogenetic position 84D3,4 has been isolated and cloned on the basis of the mutant phenotype: an absence of structures in the subdistal regions of the appendages. The shortened appendages are the consequence of a localized cell death in the imaginal discs, precursors of the adult appendages. Physical characterization of the rn locus has demonstrated that it is relatively large, occupying a minimum of 50 kb. There are two major transcripts of 1.7 kb (m1.7) and 5.3 kb (m5.3). We present here the sequence analysis of m1.7 and its putative product, rnprot1.7, and show that rnprot1.7 is similar to the product of the human n-chimaerin gene, which is expressed in brain and testes. Recently, the GAP activity of n-chimaerin was demonstrated and shown to be specific for the Rac subfamily of the Ras oncoproteins. The Rac proteins have been implicated in the regulation of secretory processes. In addition to being expressed in the imaginal discs, the m1.7 racGAP transcript was detected in developmentally specific germ line cells of the testes, the primary spermatocytes.


p53 is covalently linked to 5.8S rRNA.

p53 is covalently linked to 5.8S rRNA. We report here the isolation and identification of the RNA specifically immunoprecipitated and covalently linked to the tumor suppressor gene product p53. After treatment with proteinase K, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) band of p53 yields a single, discrete 157-nucleotide RNA, which was cloned, sequenced, and identified as 5.8S rRNA. 5.8S rRNA was obtained only after proteolysis of the p53 SDS-PAGE band. Free 5.8S rRNA did not comigrate with p53 in SDS-PAGE. This RNA was only immunoprecipitated from cells containing p53. Protein-free RNA obtained by proteolysis of the p53 band hybridized to the single-stranded DNA vector containing the antisense sequence of 5.8S rRNA. The covalence of the p53-5.8S rRNA linkage was demonstrated by the following findings: (i) p53 and the linked 5.8S rRNA comigrated in SDS-PAGE; (ii) only after treatment of the p53-RNA complex with proteinase K did the 5.8S rRNA migrate differently from p53-linked 5.8S rRNA; and (iii) this isolated RNA was found linked to phosphoserine, presumably at the 5' end. Covalent linkage to the single, specific RNA suggests that p53 may be involved in regulating the expression or function of 5.8S rRNA.


Tumorigenicity of the met proto-oncogene and the gene for hepatocyte growth factor. The met proto-oncogene is the tyrosine kinase growth factor receptor for hepatocyte growth factor/scatter factor (HGF/SF). It was previously shown that, like the oncogenic tpr-met, the mouse met proto-oncogene transforms NIH 3T3 cells. We have established NIH 3T3 cells stably expressing both human (Methu) and mouse (Metmu) met proto-oncogene products. The protein products are properly processed and appear on the cell surface. NIH 3T3 cells express endogenous mouse HGF/SF mRNA, suggesting an autocrine activation mechanism for transformation by Metmu. However, the tumor-forming activity of Methu in NIH 3T3 cells is very low compared with that of Metmu, but efficient tumorigenesis occurs when Methu and HGF/SFhu are coexpressed. These results are consistent with an autocrine transformation mechanism and suggest further that the endogenous murine factor inefficiently activates the tumorigenic potential of Methu. The tumorigenicity observed with reciprocal chimeric human and mouse receptors that exchange external ligand-binding domains supports this conclusion. We also show that HGF/SFhu expressed in NIH 3T3 cells produces tumors in nude mice.


C-terminal truncation of RAP1 results in the deregulation of telomere size, stability, and function in Saccharomyces cerevisiae. The Saccharomyces cerevisiae DNA-binding protein RAP1 is capable of binding in vitro to sequences from a wide variety of genomic loci, including upstream activating sequence elements, the HML and HMR silencer regions, and the poly(G1-3T) tracts of telomeres. Recent biochemical and genetic studies have suggested that RAP1 physically and functionally interacts with the yeast telomere. To further investigate the role of RAP1 at the telomere, we have identified and characterized three intragenic suppressors of a temperature-sensitive allele of RAP1, rap1-5. These telomere deficiency (rap1t) alleles confer several novel phenotypes. First, telomere tract size elongates to up to 4 kb greater than sizes of wild-type or rap1-5 telomeres. Second, telomeres are highly unstable and are subject to rapid, but reversible, deletion of part or all of the increase in telomeric tract length. Telomeric deletion does not require the RAD52 or RAD1 gene product. Third, chromosome loss and nondisjunction rates are elevated 15- to 30-fold above wild-type levels. Sequencing analysis has shown that each rap1t allele contains a nonsense mutation within a discrete region between amino acids 663 and 684. Mobility shift and Western immunoblot analyses indicate that each allele produces a truncated RAP1 protein, lacking the C-terminal 144 to 165 amino acids but capable of efficient DNA binding. These data suggest that RAP1 is a central regulator of both telomere and chromosome stability and define a C-terminal domain that, while dispensable for viability, is required for these telomeric functions.


Temporal order of DNA replication in the H-2 major histocompatibility complex of the mouse. As an approach to mapping replicons in an extended chromosomal region, the temporal order of DNA replication was analyzed in the murine major histocompatibility gene complex (MHC). Replicating DNA from T-lymphoma and myelomonocyte cell lines was density labeled with bromodeoxyuridine and extracted from cells which had been fractionated into different stages of S phase by centrifugal elutriation. The replicating DNA from each fraction of S phase was separated from nonreplicating DNA on density gradients, blotted, and hybridized with 34 specific MHC probes. The earliest replication occurred in the vicinity of transcribed genes K, HAM1 and HAM2, RD, B144, D, L, T18, and T3. The temporal order of replication of groups of DNA segments suggests the location of five or six replicons within the H-2 complex, some of which appear to be either unidirectional or markedly asymmetric. The rates of replication through each of these apparent replicons appear to be similar. The TL region of the S49.1 T-lymphoma cells, which contains at least three transcribed genes, replicates earlier than the inactive TL region of WEHI-3 myelomonocytic cells. These results provide further evidence of a relationship between transcription and the initiation of DNA replication in mammalian cells. The mouse MHC examined in this study is the largest chromosomal region (> 2,000 kb) measured for timing of replication to date.


TFIIA induces conformational changes in TFIID via interactions with the basic repeat. DNA-binding studies with Saccharomyces cerevisiae TFIID point mutants indicated that TFIIA interacts with the basic repeat region of TFIID and induces structural changes. The latter was shown by the ability of TFIIA to compensate for TFIID point mutants defective for DNA binding. Interaction with TFIIA also rendered TFIID binding temperature independent, thus mimicking the effect of removing the nonconserved N terminus of TFIID. In addition, N-terminal truncation of the TFIID point mutants defective for DNA binding mimicked the ability of TFIIA to restore DNA binding of those mutants. Taken together, these results suggest that TFIIA enhances TFIID binding to DNA by eliminating an otherwise inhibitory effect of the nonconserved N terminus of TFIID. Furthermore, analyses of TFIID contact points on DNA and binding studies with TATA-containing oligonucleotide probes showed that TFIIA decreases the effect of sequences flanking the adenovirus major late TATA element on TFIID binding to DNA, suggesting a possible role of TFIIA in allowing TFIID to recognize a wider variety of promoters.


Synthetic lethal mutations suggest interactions between U5 small nuclear RNA and four proteins required for the second step of splicing. To investigate the function of the U5 small nuclear ribonucleoprotein (snRNP) in pre-mRNA splicing, we have screened for factors that genetically interact with Saccharomyces cerevisiae U5 snRNA. We isolated trans-acting mutations that exacerbate the phenotypes of conditional alleles of the U5 snRNA and named these genes SLU, for synergistically lethal with U5 snRNA. SLU1 and SLU2 are essential for the first catalytic step of splicing, while SLU7 and SLU4 (an allele of PRP17 [U. Vijayraghavan, M. Company, and J. Abelson, Genes Dev. 3:1206-1216, 1989]) are required only for the second step of splicing. Furthermore, slu4-1 and slu7-1 are lethal in combination with mutations in PRP16 and PRP18, which also function in the second step, but not with mutations in factors required for the first catalytic step, such as PRP8 and PRP4. We infer from these data that SLU4, SLU7, PRP18, PRP16, and the U5 snRNA interact functionally and that a major role of the U5 snRNP is to coordinate a set of factors that are required for the completion of the second catalytic step of splicing.


Characterization of the human immunoglobulin kappa gene 3' enhancer: functional importance of three motifs that demonstrate B-cell-specific in vivo footprints. Using a combination of in vivo footprinting and site-directed mutagenesis, we have functionally characterized an enhancer located 12 kb downstream of the human immunoglobulin kappa constant-region gene. The core enhancer region is highly homologous to the murine 3' kappa enhancer. However, in addition to two regulatory elements homologous to the functional motifs of the murine enhancer, we find a third positive regulatory element in the human enhancer. This element is associated with an 11/12-bp direct repeat (DR) that is well conserved in the murine locus but was not recognized as functionally important in the murine enhancer. Mutation of any of the three motifs of the human enhancer decreases its activity to 3 to 20% of the wild-type level, indicating cooperative interaction between these elements. The DR motif does not resemble any known enhancer element and does not appear to function as a transcriptional activator on its own when present in multiple copies. Interestingly, nuclear extracts from both B- and T-cell lines contain factors binding to DR in vitro, but in vivo footprinting shows no evidence of protein-DNA binding in the T-cell line. This finding suggests that an additional regulatory mechanism, such as the effect of chromatin configuration on accessibility, may be involved in the B-cell-restricted activity of the human 3' kappa enhancer.


Purified cofactors and histone H1 mediate transcriptional regulation by CTF/NF-I. The initiation of RNA polymerase II transcription is controlled by DNA sequence-specific activator proteins, in combination with cofactor polypeptides whose function is poorly understood. Transcriptional cofactors of the CTF-1 activator were purified on the basis of their affinity for the regulatory protein. These purified cofactors were found to be required for CTF-1-regulated transcription, and they counteracted squelching by an excess of activator in in vitro reconstitution experiments. Interestingly, the cofactors possessed an inhibitory activity for basal transcription, which was relieved by the further addition of the activator. Histone H1 also contributes to the regulation of transcription by CTF-1, whereby the activator prevents repression of the basal transcription machinery by the histone. However, histone H1 could not replace the cofactors for CTF-1-regulated transcription, indicating that they possess distinct transcriptional properties. Furthermore, the purified cofactors were found to be required, together with the activator, in order to antagonize the histone-mediated repression of transcription. These results suggest that CTF-1 and its cofactors function by regulating the assembly of the basal transcription machinery onto the promoter when the latter is in competition with DNA-binding inhibitory proteins such as histone H1.


Identification of a new set of cell cycle-regulatory genes that regulate S-phase transcription of histone genes in Saccharomyces cerevisiae. Histone mRNA synthesis is tightly regulated to S phase of the yeast Saccharomyces cerevisiae cell cycle as a result of transcriptional and posttranscriptional controls. Moreover, histone gene transcription decreases rapidly if DNA replication is inhibited by hydroxyurea or if cells are arrested in G1 by the mating pheromone alpha-factor. To identify the transcriptional controls responsible for cycle-specific histone mRNA synthesis, we have developed a selection for mutations which disrupt this process. Using this approach, we have isolated five mutants (hpc1, hpc2, hpc3, hpc4, and hpc5) in which cell cycle regulation of histone gene transcription is altered. All of these mutations are recessive and belong to separate complementation groups. Of these, only one (hpc1) falls in one of the three complementation groups identified previously by other means (M. A. Osley and D. Lycan, Mol. Cell. Biol. 7:4204-4210, 1987), indicating that at least seven different genes are involved in the cell cycle-specific regulation of histone gene transcription. hpc4 is unique in that derepression occurs only in the presence of hydroxyurea but not alpha-factor, suggesting that at least one of the regulatory factors is specific to histone gene transcription after DNA replication is blocked. One of the hpc mutations (hpc2) suppresses delta insertion mutations in the HIS4 and LYS2 loci. This effect allowed the cloning and sequence analysis of HPC2, which encodes a 67.5-kDa, highly charged basic protein.


A Raf-1-related p110 polypeptide associates with the CD4-p56lck complex in T cells. The CD4 and CD8 antigens on T cells have been shown to associate with the Src family member p56lck and a GTP-binding protein, p32. The identification of receptor interactions with intracellular mediators is essential in the elucidation of downstream signals mediated by engagement of these receptor complexes. In this study, we report the detection of an additional 110-kDa polypeptide (p110) associated with the CD4-p56lck complex in human peripheral blood T lymphocytes and leukemic T-cell lines. p110 bound preferentially to CD4-p56lck as an assembled complex and poorly, if at all, to the individual components. p110 was recognized directly by an antiserum to the C-terminal region of the serine/threonine kinase Raf-1 and is related to a p110 polypeptide detected in anti-Raf-1 immunoprecipitates. Despite its association with the CD4-p56lck complex, p110 was found to be phosphorylated predominantly on serine residues. Furthermore, phorbol ester treatment of cells resulted in a transient increase in the detection of p110 associated with CD4-p56lck, concomitant with the modulation of CD4-p56lck from the cell surface. This Raf-1-related p110 is therefore likely to play a role in signals generated from the CD4-p56lck complex. p110 may serve as a bridge between the CD4-p56lck complex and the serine/threonine kinase pathways of T-cell activation.


Expression of chimeric genes by the light-regulated cabII-1 promoter in Chlamydomonas reinhardtii: a cabII-1/nit1 gene functions as a dominant selectable marker in a nit1- nit2- strain. In Chlamydomonas reinhardtii, expression of the cabII-1 gene increases dramatically in response to light (cabII-1 encodes one of the light-harvesting chlorophyll a/b-binding proteins of photosystem II). We have used a region upstream of the cabII-1 gene in translational fusions to the bacterial uidA gene (encodes beta-glucuronidase) and transcriptional fusions to the Chlamydomonas nitrate reductase gene (nit1). Chlamydomonas transformants carrying intact copies of the chimeric uidA gene do not express beta-glucuronidase at the level of enzyme activity or mRNA accumulation. Methylation in the cabII-1 promoter region of the introduced gene is extensive in these strains, suggesting that newly introduced foreign genes may be recognized and silenced by a cellular mechanism that is correlated with increased methylation. Transformants that express the chimeric cabII-1/nit1 gene have been recovered. In contrast to the endogenous nit1 gene, the chimeric cabII-1/nit1 gene is expressed in ammonium-containing medium. Moreover, nit1 mRNA accumulation is dramatically stimulated by light, with a time course that is indistinguishable from that of the endogenous cabII-1 gene. The cabII-1/nit1 gene has been used to select transformants in a nit1- nit2- Chlamydomonas strain (CC400G) and should be useful for transformation of the large number of mutants in the Ebersold-Levine lineage, which carry the same mutations.


3,5,3'-Triiodothyronine positively regulates both MyoD1 gene transcription and terminal differentiation in C2 myoblasts. Thyroid hormones are among the positive regulators of muscle development in vivo, but little is known about the way they work. We demonstrate here that MyoD1, one of the master genes controlling myogenesis, is a target of T3. After proliferating C2 myoblasts have been treated with T3 for 15 h, we observed a rise in MyoD1 expression at both the mRNA and protein levels. This is the first positive hormonal control of MyoD1 gene expression reported so far. We also provide data which suggest that T3 nuclear receptor(s) have a direct role on MyoD1 gene transcription: 1) C2 cells express the alpha 1 form of T3 nuclear receptors; 2) T3 up-regulates MyoD1 gene transcription and does not affect MyoD1 mRNA stability, as demonstrated by run-on and actinomycin D chase experiments, respectively; and 3) this transcriptional activation does not need the synthesis of intermediate protein(s) since it is not abolished by simultaneous treatment with cycloheximide. Moreover, in presence of T3, the increase of MyoD1 transcripts is associated with a faster terminal differentiation. Indeed we observed an earlier expression of various markers of myogenesis including myogenin (a regulatory gene of the MyoD1 family mainly involved in the triggering of terminal differentiation), myosin light chain 1A, and troponin T in T3-treated cells vs. untreated cells. We suggest that the regulation of a pivotal myogenic gene could be an important step in the control exerted by T3 on muscle development in vivo.


Nucleotide sequence and tissue distribution of three insulin-like growth factor I prohormones in salmon. Tissue distribution and potential alternative splicing of insulin-like growth factor I (IGF-I) messenger RNA were studied using reverse transcriptase-polymerase chain reaction (RT-PCR) on RNA from several tissues at various stages of the life cycle of coho salmon (Oncorhynchus kisutch). DNA sequence analysis of RT-PCR products revealed three IGF-I mRNA transcripts, designated Ea-1, Ea-2, and Ea-3, which code for three distinct prohormones, IGF-IA-1, IGF-IA-2, and IGF-IA-3, respectively. The E-domain of proIGF-IA-1 is 35 amino acids long and shares 77% sequence identity with the E-domain of human proIGF-IA, which is also 35 amino acids long. The proIGF-IA-2 and proIGF-IA-3 E-domains are homologous to the proIGF-IA-1 E-domain but contain 27 and 39 amino acid inserts, respectively, between Lys86 and Glu87. In the human IGF-I gene Lys86 is coded by exon 4 and Glu87 is coded by exon 6. This suggests that Ea-2 and Ea-3 transcripts may be the result of alternative splicing during pre-mRNA processing. All three transcripts were readily detectable using a solution hybridization/RNase protection assay. Furthermore, RT-PCR and DNA sequencing analysis indicate the presence of three IGF-I prohormones in another member of the Salmonidae family, the Atlantic salmon (Salmo salar). An analysis of IGF-I and -II E-domains from several vertebrates suggests that certain chemical and physical properties of the molecule are well conserved despite wide variations in primary structure. Ea-1, Ea-2, and Ea-3 transcripts were found in whole embryos, and liver, muscle, and brain of juvenile and adult salmon. At least one IGF-I transcript was found in heart, kidney, testes, ovary, adipose tissue, and spleen of juvenile salmon. These results indicate that IGF-I is expressed during embryonic development of fish, and that most tissues are capable of IGF-I mRNA production. These data also indicate that pre-mRNA transcripts can be alternatively spliced to yield at least three prohormones.


Pro-453 to Ser mutation in CYP21 is associated with nonclassic steroid 21-hydroxylase deficiency. Steroid 21-hydroxylase deficiency is the leading cause of impaired cortisol synthesis in congenital adrenal hyperplasia (CAH), with the nonclassic form (NC) comprising approximately 1% of the Caucasian population. The structure of the CYP21 gene was studied in 13 unrelated NC-CAH patients, three affected siblings, and 55 blood donors using polymerase chain reaction. In addition to the Leu-281 and Leu-30 mutations previously associated with NC-CAH, the finding of a Pro-453 to Ser mutation in exon-10 of CYP21 in the NC-CAH patients is reported. Ser-453 was found in 46.2% of unrelated NC-CAH patients, but only 7.7% and 3.6% of salt-wasting CAH patients and blood donors, respectively. In contrast to the Leu-281 and Leu-30 mutations, Ser-453 has not been previously detected in the CYP21 pseudogene (CYP21P) and, therefore, has not likely arisen by gene conversion.


Molecular cloning and expression of a full-length complementary DNA encoding the guinea pig adrenocortical estrogen sulfotransferase. Complementary DNA for the guinea pig adrenocortical estrogen sulfotransferase (EST) has been cloned and expressed. Oligonucleotides, based on amino acid sequences of the purified 34-kilodalton protein, were synthesized and used to generate a specific probe by polymerase chain reaction for screening a guinea pig adrenal cDNA library. The polymerase chain reaction rapid amplification of cDNA ends procedure was employed to obtain the 3' and 5' cDNA ends, and a full-length cDNA was constructed. The cloned cDNA consists of 1192 base pairs and encodes a protein of 296 amino acids with a calculated molecular mass of 35,161 daltons. A computer search of the protein data banks revealed significant homology with several sulfotransferases: 71% with bovine placental estrogen sulfotransferase, 52% with rat liver phenol sulfotransferase, 35% with rat liver hydroxysteroid sulfotransferase, and 36% with rat liver senescence marker protein 2. The EST cDNA was inserted into the pcDNA I eukaryotic expression vector and transfected into COS-7 cells. The successful expression of EST cDNA in COS-7 cells was ascertained by Western blot analysis using antibody generated against the protein used to obtain the original amino acid sequence. Additionally, the expressed protein was clearly functional. Only after transfection with EST cDNA was there detectable estradiol sulfotransferase activity in COS-7 cell cytosol. The expressed EST had a single pI of 6.4, whereas native guinea pig adrenocortical EST exhibits four primary charge isoforms. The majority of adrenocortical EST activity focuses as a broad bimodal band in the pH range of 6.6-6.2; additionally, three other discrete immunocross-reactive isoforms are present with pIs of 5.5, 5.4, and 5.2. Antibodies generated against each individual isoform cross-react with all the other isoforms and with the expressed protein. These isoforms were previously reported to be isomers of a pregnenolone-binding protein; however it is now evident that the isoforms and antibodies raised against them are EST specific. Under high stringency hybridization conditions, EST mRNA was only detected in the adrenal gland, where two mRNA species of 1.4 and 1.8 kilobases were evident; when low stringency conditions were used, a faint 1.4-kilobase band was also detected in the liver. Primer extension analysis revealed that the multiple mRNAs do not arise from differential transcription initiation sites, and genomic Southern blot analysis indicated that the multiple mRNAs arise from a single gene.


Activation of insulin-like growth factor II expression during skeletal muscle regeneration in the rat: correlation with myotube formation. Insulin-like growth factors (IGFs) are important stimulators of proliferation and differentiation of cultured myoblasts. It has previously been shown that IGF-I is induced during muscle regeneration in rodents, however, little is known about the expression of IGF-II. Therefore, two in vivo models were used to analyze IGF-II mRNA expression during skeletal muscle regeneration in the rat: injection of the snake venom notexin and induction of ischemia. During the regeneration process the levels of both IGF-I and IGF-II mRNA were transiently induced, as analyzed by solution hybridization. Both IGF-I-like immunoreactivity and IGF-II-like immunoreactivity were found to be present during muscle regeneration. In a time course study, induction of IGF-II was preceded by IGF-I, both at the mRNA and protein levels. Using alpha- and beta-actin as markers for different stages of skeletal muscle differentiation, together with the immunohistochemistry data, it is concluded that the expression of IGF-I and IGF-II occurs at different differentiation stages, and that IGF-II appears concomitant to the formation of myotubes. These results suggest that each IGF has a distinct role during the differentiation of muscle cells.


The Nb2 form of prolactin receptor is able to activate a milk protein gene promoter. We have recently cloned a cDNA encoding a mutant form of PRL receptor (PRL-R) from Nb2 cells, a PRL-dependent T lymphocyte-derived cell line. This cDNA is identical to the long form of the rat PRL-R, except for a deletion of 594 base pairs in the cytoplasmic domain, resulting in a mature receptor protein of 393 amino acids. Although a segment containing three cytoplasmic regions of moderate to high amino acid sequence identity with members of the PRL/GH receptor family is missing in this receptor form, the region of highest (70%) identity is retained. In the following studies, a homologous functional assay was developed to test the activity of three forms of receptor with respect to their ability to transmit a lactogenic signal. In this system, CHO cells were transiently transfected with a construct containing 2300 base pairs of the 5'-flanking sequence of the rat beta-casein gene fused to the chloramphenicol acetyltransferase (CAT) gene and an expression vector containing the various forms of rat PRL-R cDNA. The transfected cells were grown in serum-free medium in the absence or presence of PRL. In cells transfected with the long form of the PRL-R and beta-casein/CAT construct, a 7.2- +/- 0.9-fold induction (n = 3) of CAT activity was seen when cells were cultured in the presence of 400 ng/ml PRL and 1 micrograms/ml hydrocortisone. This level of stimulation was similar to that observed for the ovine beta-lactoglobulin/CAT construct in which a 5.7- +/- 1.2-fold (n = 3) effect was found.(ABSTRACT TRUNCATED AT 250 WORDS)


Steroidogenic factor I, a key regulator of steroidogenic enzyme expression, is the mouse homolog of fushi tarazu-factor I. We proposed that a cell-selective regulatory protein coordinately regulates the expression of three enzymes that are required for the biosynthesis of corticosteroids: cholesterol side chain cleavage enzyme, steroid 21-hydroxylase, and the aldosterone synthase isozyme of steroid 11 beta-hydroxylase. In this report, we identify a 53-kilodalton protein, termed steroidogenic factor 1 (SF-1), that interacts with the related promoter elements from these steroidogenic enzymes, and we isolate and characterize a cDNA that very likely encodes this protein. We first showed that nuclear extracts from bovine adrenal glands interact with the mouse steroidogenic regulatory elements, forming complexes indistinguishable from those produced by nuclear extracts from mouse Y1 adrenocortical cells. These bovine adrenal extracts were subjected to sequential ion exchange and affinity chromatography to yield a highly enriched preparation of SF-1. The predominant protein in the affinity-purified preparation comigrated with shift activity and had a mol wt of 53,000; UV cross-linking experiments demonstrated directly that this 53-kilodalton protein interacted with the steroidogenic regulatory element. Even with this marked enrichment, affinity-purified SF-1 bound six steroidogenic regulatory elements. These results support strongly the model that a steroidogenic cell-selective protein interacts with related promoter elements from three steroidogenic enzymes to regulate their coordinate expression. The recognition sequence of SF-1 closely resembles those of nuclear hormone receptor family members, suggesting that SF-1 may belong to this supergene family. By screening a Y1 cell cDNA library with the DNA-binding region of the H-2RIIBP nuclear hormone receptor cDNA, we isolated a cDNA that is selectively expressed in steroidogenic cells. When expressed as a glutathione S-transferase fusion protein in Escherichia. coli, the protein encoded by this cDNA interacts with all six related steroidogenic regulatory elements with a binding specificity indistinguishable from that of SF-1. Surprisingly, the sequence of the putative DNA-binding domain of this cDNA matches exactly the corresponding sequence of the mouse homolog of the Drosophila transcription factor fushi tarazu-factor I. The demonstration that a member of the nuclear hormone receptor family interacts with the steroidogenic regulatory elements provides intriguing insights into possible mechanisms by which these essential genes are regulated.


Effects of calcium and calcium ionophores on prolactin gene expression in GH3 and 235-1 rat pituitary tumor cells. Previous observations that extracellular calcium (Ca2+) enhanced PRL mRNA levels posttranscriptionally in GH3 rat pituitary tumor cells were made using double-stranded transcription probes. The effects of Ca2+ and the Ca2+ ionophore, ionomycin, on PRL gene expression in GH3 and 235-1 cells were investigated using site- and strand-specific probes. Treatment of GH3 and 235-1 cells with 0.5 mM Ca2+ in serum-free medium specifically increased PRL mRNA levels by severalfold. In 235-1 but not GH3 cells PRL gene transcription was comparably induced by Ca2+. Use of single-stranded 5' and 3' probes revealed no antisense transcription, nor any Ca2+ effect on transcriptional elongation. Treatment with Ca2+ plus ionomycin inhibited PRL mRNA levels and gene transcription in both cell lines. Although their PRL gene transcription rates are similar, several basic differences were noted between the cell lines. The 235-1 cells exhibit a different profile of nuclear PRL pre-RNAs than GH3 cells. Also, mRNA levels for a Ca(2+)-regulated gene (GRP78) did not change in Ca(2+)-treated GH3 cells but decreased in Ca(2+)-treated 235-1 cells. Ionomycin treatment increased GRP78 mRNA levels in both cell lines. Thus, addition of extracellular Ca2+ appears to affect [Ca2+]i in 235-1 but not GH3 cells, while ionomycin affects [Ca2+]i in both cell lines. These data suggest that changing [Ca2+]i modulates PRL gene transcription. The comparative data suggest that posttranscriptional PRL regulation is Ca(2+)-regulated in GH3 cells, but is constitutive in 235-1 cells.


Posttranscriptional regulation of prolactin (PRL) gene expression in PRL-deficient pituitary tumor cells. Rat pituitary acidophils consist of somatotropes (GH+/PRL-), lactotropes (GH-/PRL+), and lactosomatotropes (GH+/PRL+). Studies have indicated interconversion of these cell types in response to changing hormonal status. Representative tumor cell lines have been obtained for each acidophil cell type, and some display spontaneous interconversions. We examined whether the switch from GH3 cells (GH+/PRL+) to GH3LP and GC cells (both GH+/PRL-) involves repression of PRL gene expression at a transcriptional vs. posttranscriptional level. PRL mRNA is undetectable or barely detectable in GH3LP and GC cells. In contrast, nuclear extracts from these cells transcribe the PRL promoter in vitro, and their Pit-1 mRNA levels are comparable to those in GH3 cells. Nuclear run-on transcription assays demonstrated that the PRL gene is transcribed in GH3LP and GC cells at a rate of about 60% of that observed in GH3 cells. No evidence was obtained for a block to transcriptional elongation or for transcription in the antisense direction across the PRL gene. Northern blot analysis of nuclear RNA revealed partially degraded and undetectable PRL gene transcripts in GH3LP cells and GC cells, respectively. These findings indicate that PRL gene transcripts are specifically degraded in tumor cells which display a pure somatotrope phenotype and raise the possibility that the trans-differentiation of lactosomatotropes to somatotropes involves posttranscriptional regulation of PRL gene expression.


Identification and characterization of the chicken transforming growth factor-beta 3 promoter. The promoter regions of the three mammalian transforming growth factor-beta genes (TGF-beta s 1, 2, and 3) have been recently cloned and characterized. The sequences show little similarity, suggesting different mechanisms of transcriptional control of these genes. To study differences in transcriptional regulation of mammalian and avian TGF-beta, we have cloned and sequenced the 5'-flanking region of chicken TGF-beta 3. Characterization of this region showed a TATA box and cAMP-responsive element (CRE) and AP-2 binding site consensus sequences starting at 12 and 28 base pairs, respectively, upstream from the TATA box. Moreover, four additional AP-2-like sites, 10 binding sites for the transcription factor Sp1, as well as two AP-1-like sites were also identified. Except for 32 base pairs of identity centered around the TATA box and CRE site and four other relatively small regions of identity, the chicken TGF-beta 3 promoter was found to be structurally very different from the human TGF-beta 3 promoter. Promoter fragments were cloned into a chloramphenicol acetyltransferase reporter plasmid to study functional activity. Basal transcriptional activity of the promoter was regulated in quail fibrosarcoma QM7 cells and in human adenocarcinoma A375 cells by multiple upstream elements including the TATA, CRE, and AP-2 sites. As in the human TGF-beta 3 promoter, the CRE site showed activation by forskolin, an effect which could be shown by expression of TGF-beta 3 mRNA in cultured chicken and quail cells as well. Our results indicate a complex pattern of transcriptional regulation of the chicken TGF-beta 3 gene and suggest that differences in the regulation of expression of the genes for mammalian and avian TGF-beta 3 may result in part from the unique structure of their 5'-flanking regions.


Homodimer formation is rate-limiting for high affinity DNA binding by glucocorticoid receptor. The glucocorticoid receptor (GR) is a hormone-inducible transcription factor which activates transcription of specific genes by binding to a DNA sequence present in the promoters of inducible genes. These glucocorticoid response elements (GREs) have a conserved palindromic sequence. Each half-GRE palindrome binds one subunit of GR. We have assessed the relative affinity of GR monomers and homodimers for GRE and determined whether homodimer formation is rate-limiting for high affinity GRE binding. The in vitro affinity of GRE binding by GR homodimers was approximately 2 x 10(-10) M, whereas it was approximately 1 nM for GR monomers. While homodimer:GRE complexes were very stable, monomer:GRE complexes appeared less stable in vitro. At low receptor concentration, GR preferentially bound GRE as a homodimer. Prior dilution of GR (equilibrium shifted to monomers) before addition to a GRE binding reaction resulted in slower kinetics of binding by comparison to parallel reactions in which concentrated (largely homodimeric) GR was added first. Taken together, these experiments suggest that homodimer formation is rate-limiting for high affinity GRE binding. A GRE mutant which contained only a half-binding site and which was unable to bind GR homodimers was also unable to confer glucocorticoid-inducible transcription. Taken together with previous work, these experiments support the model that GR homodimers are required for hormone-dependent activation of transcription and that receptor homodimer formation is rate-limiting for GRE binding.


Insulin and insulin-like growth factor I regulate a thyroid-specific nuclear protein that binds to the thyroglobulin promoter. The mechanism responsible for the stimulation of thyroglobulin (Tg) gene expression by insulin and insulin-like growth factor I (IGF-I) in rat thyroid FRTL-5 cells has been investigated. Both insulin and IGF-I stimulate transcription from the Tg promoter in a transient transfection assay demonstrating that the promoter used contains the DNA signals necessary for insulin and IGF-I regulation. Promoter mutations that interfere with the binding of thyroid transcription factor 1 (TTF-1), TTF-2, and the ubiquitous transcription factor abolish the insulin/IGF-I response, indicating that the three factors may be involved in the observed transcriptional control. Protein-DNA binding studies did not reveal any effect of insulin/IGF-I on the ubiquitous transcription factor and the TTF-1 binding capacity. Instead, TTF-2 is absent in nuclear extracts from cells depleted of serum and insulin. Addition of insulin or IGF-I restores the TTF-2 concentration to normal levels and requires ongoing protein synthesis. The insulin effect was maximal at 24 h and at a concentration of 1 microgram/ml. The same effect was observed with a 10-fold lower concentration of IGF-I. These results suggest that insulin (probably through the IGF-I receptor) and IGF-I modulate the levels of TTF-2, which results in an increased expression of the Tg gene.


R339H and P453S: CYP21 mutations associated with nonclassic steroid 21-hydroxylase deficiency that are not apparent gene conversions. Steroid 21-hydroxylase deficiency is the most common enzymatic defect causing congenital adrenal hyperplasia, an inherited disorder of cortisol biosynthesis. All mutations thus far characterized that cause this disorder appear to result from recombinations between the gene encoding the enzyme, CYP21B (CYP21), and the adjacent pseudogene, CYP21A (CYP21P). These are either deletions caused by unequal crossing-over during meiosis or apparent transfers of deleterious sequences from CYP21A to CYP21B, a phenomenon termed gene conversion. However, a small percentage of alleles do not carry such a mutation. We analyzed DNA from a patient with the mild, nonclassic form of 21-hydroxylase deficiency, who carried one allele that had no gene conversions detectable by hybridization with oligonucleotide probes. Sequence analysis revealed that this allele carried two missense mutations, R339H and P453S, neither of which has been previously observed in CYP21A or CYP21B. Each of these mutations was introduced into CYP21 cDNA which was then expressed in COS1 cells using a vaccinia virus system. Each mutation reduced the ability of the enzyme to 21-hydroxylate 17-hydroxyprogesterone to 50% of normal and the ability to metabolize progesterone to 20% of normal. Thus, each of these mutations represents a potential nonclassic 21-hydroxylase deficiency allele that is not the result of an apparent gene conversion.


Differential expression of neural cell adhesion molecule and cadherins in pancreatic islets, glucagonomas, and insulinomas. The endocrine cells of the pancreas develop from the endoderm and yet display several characteristics of a neuronal phenotype. During embryonic life, ductal epithelial cells give rise to first the glugagon-producing cells (alpha-cells) and then cells that express insulin (beta-cells), somatostatin (delta-cells), and pancreatic polypeptide (PP-cells) in a sequential order. The endocrine cells are believed to arise from a stem cell with neuronal traits. The developmental lineage from a common neuron-like progenitor is evidenced by: transient coexpression of more than one cell type-specific hormone in immature cells, expression of neuronal markers during islet cell development, and the pluripotentiality of clones of insulinoma cells to develop into cells expressing other islet cell hormones. The four mature endocrine cell types assume a particular organization within the islets of Langerhans in a process where cell adhesion molecules are involved. In this study we have analyzed the expression of neural cell adhesion molecule (NCAM) and cadherin molecules in neonatal, young, and adult rat islet cells as well as in glucagonomas and insulinomas derived from a pluripotent rat islet cell tumor. Whereas primary islet cells at all ages express unsialylated NCAM and E-cadherin, as do insulinomas, the glucagonomas express the polysialylated NCAM, which is characteristic for developing neurons. The glucagonomas also lose E-cadherin expression and instead express a cadherin which is similar to N-cadherin in brain. Insulinoma cells express E-cadherin but differ from primary islet cells by expressing a second cadherin molecule, which is similar to N-cadherin. The expression of NCAM and cadherin isoforms in the glucagonoma suggest that this transformed alpha-cell type has converted to an immature phenotype with strong neuronal traits, reflecting the early palce of glucagon-producing cells in the islet cell lineage. In contrast, insulinoma cells are more islet-like in their phenotype and show less neuronal traits.


CD32A (Fc gamma RIIa) mRNA expression and regulation in blood monocytes and cell lines. The cell surface expression of the CD32 receptors for the Fc portion of immunoglobulin G (Fc gamma RII) is highly regulated by agents such as phorbol ester (PMA) and cytokines. In this study we investigated the regulatory effects of PMA, aggregated IgG (AIgG) and KuFc79 anti-CD32 monoclonal antibodies (mAb) on the expression of the CD32A isomer mRNA. When U937 (CD32+ cells) are incubated with PMA a significant enhancement of the CD32A isomer mRNA is observed. The CD32A mRNA is also markedly enhanced when the CD32+ K562 cells are incubated with AIgG and anti-CD32 mAb but not with control MOPC-195 mAb. The addition of actinomycin D (ActD), a transcriptional inhibitor together with PMA, AIgG or KuFc79 mAb diminishes the enhanced levels of CD32A mRNA to the basal, constitutively expressed levels, implicating transcriptional regulation in this modulatory process. The PMA induced mRNA is rapidly degraded while the constitutively expressed CD32A mRNA is not, suggesting differential regulation of the stimulated vs the unstimulated CD32A mRNA. Inhibition of protein synthesis does not significantly affect the upregulation of CD32 mRNA by PMA, AIgG or KuFc79 in U937 and K562 cells. The upregulation of CD32A mRNA observed in the cell lines U937 and K562 is also detected when normal blood monocytes are used. Similarly to the cell lines the enhancement of CD32A mRNA in monocytes is blocked by ActD.


Specificity of anti-P25 antibodies produced against whole HIV-1 particles or soluble forms of the protein. Specificity of anti-p25 antibodies produced against either whole Human Immunodeficiency Virus type 1 (HIV-1) particles in humans and chimpanzees, or against soluble forms of the protein in chimpanzees and rabbits was analyzed by ELISA using a panel of 37 long (> or = 30 residues) or shorter (9-21 residues) overlapping peptides covering the entire p25 sequence. Antibodies elicited by intact virions presented similar reactivity patterns in HIV-1-infected humans and in HIV-1-infected or immunized chimpanzees and recognized only a limited region mostly the C-terminus of the molecule. Moreover, 8 of the human sera (36%), which nonetheless reacted with high titers and avidity with native p25, did not bind to any long or short peptide. These results suggest that the majority of antibodies elicited by viral particles are presumably directed to conformational epitopes. In contrast, antibodies raised against soluble forms of p25 could react against all long peptides but one (residues 211-245) and against some short peptides, indicating that most of p25 sequence may be immunogenic under these conditions. These results suggest that the reactivity spectrum of anti p25 antibodies is rather different if they are produced against intact HIV-1 particles or the soluble protein. They also indicate that it may be possible to manipulate the specificity of the humoral immune response by using either intact virions or purified proteins.


Characterization of the binding of Bolton-Hunter labeled [125I]C5a to human neutrophil, monocyte and U-937 cell membranes. The fifth component of the complement cascade, C5a, was iodinated using the Bolton-Hunter reagent. Results from the present study, using the high affinity ligand, [125I]Bolton-Hunter-labeled C5a ([125I]BH-C5a), revealed a single binding site on membranes prepared from human neutrophils, U-937 cells and human monocytes. Saturation studies demonstrated Bmax values in these cells of 11.5, 47.3 and 16.6 fmol/10(6) cells, respectively. The C5a receptor demonstrated a very high affinity for [125I]BH-C5a of approximately 4 pM in each cell type. Competition studies using analogs of C5a generated a similar order of potency in each of the cell types of C5a > or = C5a(1-74), Ser66Ala > C5a(1-73) > C5a(1-69). These studies indicate that [125I]BH-C5a labels a similar receptor in neutrophil, U-937 cell and monocyte membranes. Furthermore, C5a(1-73) produced shallow inhibition curves in competition experiments in each cell type. Computer analysis of the binding data revealed two components of binding. When 10 nM unlabeled C5a was used to initiate dissociation of [125I]BH-C5a binding in neutrophil membranes, two binding components were observed. In addition, dissociation of [125I]BH-C5a binding by 10 nM unlabeled C5a in the presence of 1 mM GppNHp decreased the percentage of binding to the slowly dissociating, high affinity binding component from 84 to 58%. These results suggest that multiple states of the C5a receptor exist.


Cold target competition analysis of the classical activation pathway of complement-mediated cytotoxicity: a non-interaction model for competing lysis. A mathematical analysis of cold target competition experiments of complement-mediated lysis is presented, aimed at developing a minimal model of lysis where no interaction between the competing populations of sensitized blood group A and B erythrocytes is presumed. The model is able to predict the extent of lysis from the input values with remarkable accuracy suggesting that under the conditions used no stimulation and/or inhibition of the lysis of the sensitized erythrocytes occurs. The distribution of complement between the competing A and B erythrocyte populations is approximated by the model and found to be proportional to the 5th and 4th power of the ratios of the antibody and target cell concentrations, respectively. In accordance with earlier observations, suggesting that the interaction between the antibody and the C1q molecules is based on polar electrostatic charges, we propose that the sensitizing antibody provides an electrostatic field around the erythrocytes which attracts C1q molecules towards their membranes.


The same few V genes account for a majority of oxazolone antibodies in most mouse strains. The early primary anti-phenyloxazolone antibodies of 12 mouse strains were studied by determining proportions of two defined subsets id495 (the classical phOx idiotype) and id350. Id495-positive antibodies bear an H chain encoded by VHOx1 gene (family Q52) and an L chain usually coded for by VKOx1 but occasionally by other VK genes. Id350-positive antibodies are encoded by a VK gene VK45.1, and usually by a VH gene of the S107 family. All 12 strains (representing nine H-chain and four kappa-chain haplotypes) produced id350-positive anti-phOx antibodies. While id495 is the predominant major subset in the BALB/c response (originally studied), id350 seems to be the predominant subset of early anti-phOx antibodies in the mouse species. The combined proportion of the two subsets varied from ca. 50 to almost 100% of the total in all strains except C57BL.


Monoclonal antibodies to a CD4 peptide derivative which includes the region corresponding to an immunoglobulin CDR3: evidence of the involvement of pre-CDR3-related region in HIV-1 and host cell interaction. A CD4 peptide of amino acid residues 68-130 [CD4(68-130)], which had the capacities to inhibit HIV-1 replication and HIV-1-induced syncytium formation, was used as an immunogen for the preparation of mAb. The mAbs prepared were classified into at least five types (I-V) in terms of their recognition sites by ELISA using various kinds of smaller CD4 peptides. Among them, the type I mAb no. 35 recognizing amino acid residues 72-84, which lies just before the region corresponding to an immunoglobulin third complementarity-determining region (CDR3), showed the strongest effects in reducing both HIV-1 infection and HIV-1-induced syncytium formation, although a large amount of no. 35 mAb was necessary to reduce such HIV-1 activities compared with those of anti-Leu-3a and OKT4A mAbs which recognize CD4 epitopes near a portion corresponding to an immunoglobulin CDR2. Western blot analysis showed that the reactivities of CD4 molecule in CD4-positive cells or sCD4 molecule with types I-V mAbs were stronger than that with anti-Leu-3a mAb. Flow cytometry showed that no. 35 mAb was faintly reactive with native CD4 molecule on cell surface at the concn showing the inhibitory effects on HIV-1 infection and syncytium formation. In addition, a smaller peptide CD4(66-92), one of the good epitope peptides for no. 35 mAb, also showed strong inhibitory effect on HIV-1 infection as well as a weaker inhibitory effect on syncytium formation. These results suggest that, in addition to the CD4 CDR2-related region, the pre-CDR3-related region is also involved in the early events of the interactions between the host cell and HIV-1.


Distribution of allergens and allergen-coding mRNAs in various tissues of white birch. The distribution of allergenic proteins was investigated in various tissues of white birch, Betula verrucosa (pollen, leaves and male inflorescences containing immature pollen). In addition, callus and suspension culture cells were investigated for expression of IgE-binding proteins. Furthermore, RNA was extracted from all these tissues and subjected to in vitro translation in a cell-free wheat germ system. Bet v I, the major birch pollen allergen, could be extracted easily from pollen, and in low amounts from callus and leaves. No Bet v I could be extracted from immature male inflorescences. Minor allergens were expressed in high concentrations in pollen and in low concentrations in immature male inflorescences. No minor allergens could be detected in callus and leaves. In contrast to these observations, RNA from all the tissues as well as from callus could be translated in vitro into Bet v I as well as into minor allergens, in particular birch profilin (Bet v II), an important minor allergen. These data suggest that IgE-binding proteins of B. verrucosa, especially Bet v I, under certain circumstances can readily be synthesized in tissues other than pollen. This concept is corroborated by the recent observation that Bet v I reveals high homology with disease resistance response gene products from other plants, suggesting a similar function of Bet v I for the birch.


Genomic organisation and sequence of the extracellular domain exons of the bovine Fc gamma RI receptor, and evidence for restricted binding of ruminant IgG to U937 cells. Southern blotting of bovine genomic DNA and hybridization with a human Fc gamma RI cDNA probe, p135, has identified a single copy of the bovine Fc gamma RI gene. A bovine genomic lymphocyte library in lambda EMBL3 was screened with probe p135. A positive lambda clone, 15.5.4, containing the three extracellular domain exons of Fc gamma RI, has been cloned, mapped and sequenced. Each extracellular domain is encoded within a single exon. All three domains are assigned to the C-2 set of the Ig superfamily with 58% identity between amino acid residues of bovine, human and mouse Fc gamma RI. Pairs of cysteine residues are conserved in each domain as potential sites for intra-chain disulphide bonding. Human monocytoid U937 cells were used as a model to test binding homology within the Fc gamma RI family. The binding of IgG isotypes to IFN-gamma stimulated U937 cells was determined by FACScan flow cytometry. U937 cell Fc gamma RI receptor does not bind bovine or ovine IgG isotypes. On the basis of these studies and by comparison of the Fc determinant region sequences of IgG, the introduction of species specificity in Fc gamma RI/IgG interaction by evolutionary drift is proposed.


Sensitive non-radioactive detection of HIV-1: use of nested primers for the amplification of HIV DNA. This report describes the use of the polymerase chain reaction (PCR) for the non-radioactive detection of HIV-1 proviral genomic sequences in HIV-1 infected cells. We have developed a sensitive assay, using three different sets of nested primers and our results show that this method is superior to standard PCR for the detection of HIV-1 DNA. The assay described features the use of a simple and inexpensive sample preparation technique and a non-radioactive hybridization procedure for confirmation of results. To test the suitability of the assay for clinical purposes, we tested cell samples from 76 anti-HIV-1 positive patients. All were positive for at least one primer set: 88% were positive for all three sets of primers; 9% were positive for two sets of primers and 3% were positive for only one set of primers. It provides a useful approach to the study of HIV-1 infection in patient samples where genomic copies often are present at such low numbers that they are otherwise undetectable.


Generation of digoxigenin-labelled double-stranded and single-stranded probes using the polymerase chain reaction. As the polymerase chain reaction (PCR) can be used for the generation of vector-free probes, the optimum conditions for incorporation of digoxigenin-11-dUTP into hepatitis B virus (HBV) probes have been investigated. High yields of double-stranded or single-stranded probes can be obtained by utilizing a pair of primers or one primer alone. The probes were tested by dot-blot hybridization on HBV plasmid DNA, slot-blot hybridization on total cellular RNA of Alexander cells and Southern blot hybridization on cellular DNA of Alexander cells and HBV plasmid DNA. They were also tested by in situ hybridization (ISH) on HBV-positive biopsy liver tissue. A ratio of dig-dUTP:dTTP of 1:3 gave highest sensitivity in DNA hybridization. No loss of amplification efficiency and sensitivity was observed when the final concentration of dig-11-dUTP and dTTP was reduced to 20 microM and 60 microM respectively, compared to 200 microM each of dATP, dCTP, dGTP. Several different sizes of double-strand probes were compared by dot-blot hybridization. Longer probes were more sensitive. Strong signal could also be obtained by combination of two or three small probes, which have overlapping sequences. Single-stranded DNA probes had advantages of simplicity of use, high sensitivity and strand specificity.


Colorimetric detection of Plasmodium falciparum and direct sequencing of amplified gene fragments using a solid phase method. A rapid colorimetric assay for the detection of DNA from Plasmodium falciparum malaria is described, allowing direct sequencing of amplified fragments in the positive samples. The method is based on amplification by the polymerase chain reaction (PCR), with incorporation of biotin and a lac operator sequence in the amplified target DNA. The PCR product was immobilized on streptavidin-coupled magnetic beads, and detected by the specific binding of an Escherichia coli lac repressor beta-galactosidase fusion protein. Positive samples were subsequently treated with alkali to generate single stranded templates, which were used for solid phase genomic sequencing. As targets for amplification and sequencing we selected a region of the gene for the antigen Pf155/RESA and a region of the parasite dihydrofolate reductase gene (PfDHFR/TS). We show here that both of these gene targets can be used for specific detection of P. falciparum in patient blood samples. Genomic sequencing of five patient isolates revealed no variation in the Pf155/RESA gene fragment. In a comparison of this sequence with conserved protein domains, a marked similarity to the src homology region 3 was detected. A point mutation was found in the PfDHFR/TS gene fragment of one of the clinical samples, replacing Ser108 with Asn. This mutation has earlier been described in pyrimethamine and cycloguanile-resistant strains of P. falciparum.


Identification of Shiga-like toxin type II producing Escherichia coli using the polymerase chain reaction and a digoxigenin labelled DNA probe. Epidemiological studies have demonstrated that enterohaemorrhagic strains of Escherichia coli which cause the haemolytic uremic syndrome in humans and the oedema disease in pigs more frequently produce Shiga-like toxin type II (SLT-II) than any other member of the Shiga-like toxin family. A technique has been developed for the identification of SLT-II producing E. coli using the polymerase chain reaction (PCR) and a digoxigenin (DIG)-labelled DNA probe to facilitate the early detection and epidemiological analysis of these pathogens. Whole cell DNA liberated from isolated colonies during the denaturation step of PCR was amplified using a primer pair which is homologous to the slt-II gene sequences. The amplification products were transferred directly to a nitrocellulose membrane or following agarose gel electrophoresis and DNA denaturation. A chemically labelled DNA probe, prepared using PCR with the incorporation of DIG, was used to identify the PCR products of strains which produced SLT-II or a variant of SLT-II.


Quantification of sensitive non-isotopic filter hybridizations using the peroxidase catalyzed luminol reaction. The development of a sensitive, non-isotopic filter hybridization method based on the peroxidase catalyzed luminol reaction is described. High sensitivity was achieved by optimizing the conditions of the hybridization procedure, the immunochemical detection and the peroxidase/luminol reaction. This resulted in the reproducible detection of 10-30 femtogram of target DNA on blots within minutes when a cooled charge coupled device (CCD) camera was used to record the luminescence signal. After optimalization, the system was successfully applied for the qualitative and quantitative analysis of small amounts of DNA in dot-blots as well as in Southern blot analysis.


Effects of post-mortem autolysis on the detection of rabies virus genomic RNA and mRNA in mouse brain by using in situ hybridization. The effects of post-mortem autolysis were studied on the detection of rabies virus RNA in the brains of mice with experimental rabies by using in situ hybridization (ISH). The brains of CVS-infected mice were subjected to autolytic periods in situ of up to 72 h. ISH was performed with 3H-labelled RNA probes for rabies virus glycoprotein gene genomic RNA and mRNA. During the post-mortem period there was progressive loss of signals for genomic RNA and mRNA, which was greater for mRNA. ISH signals in perikarya also changed for genomic RNA from a multifocal to a diffuse distribution during the post-mortem period. Rabies virus antigen was better preserved during the autolytic period. Effects of the agonal state, degradation of RNA by ribonucleases, and diffusion of RNA out of cells prior to fixation could explain the loss of ISH signals in post-mortem tissues.


PCR amplification of mini-exon genes differentiates Trypanosoma cruzi from Trypanosoma rangeli. Synthetic oligonucleotides corresponding to a conserved 22 nucleotide sequence within the tandemly repeated mini-exon gene have been used to amplify a single gene-containing repeat from Trypanosoma cruzi and Trypanosoma rangeli, two morphologically similar organisms with overlapping hosts and geographical distribution but different pathogenicity in humans. The T. cruzi repeat is 582 nucleotides long and the T. rangeli repeat is 858 nucleotides. The two organisms may therefore be distinguished primarily by the electrophoretic mobilities of their respective amplification products. Confirmation of the diagnosis can be obtained by Southern blot analysis using species-specific DNA probes from the unique intergenic regions. We also present a diagnostic assay in which the unique intergenic regions are immobilized on nylon membranes and differentiation is based on hybridization with a digoxigenin-labelled PCR product.


Comparison of spot-blot and microtitre plate methods for the detection of HIV-1 PCR products. We have compared spot-blot methodology with a recently developed rapid microtitre plate assay for the specific detection of HIV-1 PCR products. We have studied blood specimens isolated from HIV-1 infected individuals (48 asymptomatic and 56 symptomatic patients). Mononuclear cells were isolated, lysed and processed for PCR. Both PCR product detection methods were carried out in parallel on all amplified samples. HIV-1 sequences were detected by spot-blot or microtitre plate hybridization in samples taken from 42/48 asymptomatic and 53/56 symptomatic subjects. Concordant results between the two detection methods were observed for 90 samples, with 81 positive and nine negative assays. On repeat evaluation of the 14 discordant samples, nine showed concordant positive results, near the limit of detection of the assay. Serial dilutions of ACH-2 cells were amplified, and the PCR products were detected using the microtitre plate assay, yielding semi-quantitative results. The sensitivity of this simple, rapid assay compares with that of more laborious DNA detection systems. This may become a useful tool in HIV-1 research and in the clinical care of seropositive individuals.


Use of modified nucleotides and uracil-DNA glycosylase (UNG) for the control of contamination in the PCR-based amplification of RNA. The inadvertent carryover of amplified fragments of nucleic acids (amplicons) is a potential source of contamination in the polymerase chain reaction. Recently, a method has been developed to generate amplicons with deoxyuracil triphosphate (dUTP) and to specifically hydrolyze these amplicons with uracil-DNA glycosylase (UNG) following the completion of the assay. We evaluated this system for the specific amplification of RNA from coxsackievirus A3 and B3. We found that RNA from both viruses could be amplified with dUTP, although the use of this triphosphate in place of TTP resulted in some loss of assay sensitivity. We also found that the dUTP-containing amplicons could be efficiently hydrolyzed by UNG, resulting in a 10,000,000-fold reduction in amplicon concentration with little effect on the native nucleic acid. The dUTP-UNG method has a great deal of potential for reducing amplicon contamination during the routine performance of nucleic acid amplification reactions.


Arrangement of DYZ1 and DYZ2 repeats on the human Y-chromosome: a case with presence of DYZ1 and absence of DYZ2. The composition of Yq-heterochromatin is dominated by the two repetitive sequences DYZ1 (4000 copies) and DYZ2 (2000 copies). Probes derived from these sequences can be used for sex determination and the structural analysis of aberrant Y-chromosomes. Using such probes Schmid et al., have recently proposed a regular interspersion of the two sequences in a ratio of 2:1 over the entire Yq12 chromosome region. By Southern analysis we investigated the DNA of a normal male, cytogenetically negative for Yq-heterochromatin. Applying the same probes as used by Schmid et al., only a small amount of DYZ1 material could be detected. The case presented indicates the presence of DYZ1 only in the Yq11-Yq12 junction region and excludes DYZ2 from any function relevant for normal male development.


Controversies in prostate pathology: dysplasia and carcinoma in situ. In recent years we have made great strides in our understanding of various atypical lesions within the prostate. This clarity originated with the recognition that lesions of atypical hyperplasia of the prostate are diverse both in their histology and in their potential relationship to adenocarcinoma. While the possible relationship of adenosis to carcinoma is still somewhat controversial, there has been a growing body of histological, histochemical, and immunohistological evidence demonstrating that intraductal dysplasia (PIN) is closely linked to some forms of adenocarcinoma of the prostate. Whether there are significant differences in the relationship of intraductal dysplasia to clinically detectable peripherally located adenocarcinoma and centrally located incidentally found carcinomas needs additional clarification. Further studies on all forms of atypical hyperplasia are still required to determine their relative risk of developing carcinoma, similar to those that have been recently published on various atypical hyperplastic lesions within the breast. In order for these studies to be successful, better imaging techniques of the prostate must become available to rule out invasive carcinoma already being present when one of the forms of atypical hyperplasia is identified on biopsy. Additional directions of research in the future will also undoubtedly probe the molecular biology of various forms of atypical hyperplasia, in particular intraductal dysplasia and its relationship to carcinoma, although at this time the molecular characteristics of adenocarcinoma of the prostate is still in its infancy.


Diagnostic correlations with whole mounts of radical prostatectomy specimens. While probably not necessary in routine diagnosis, whole-mount sections of radical prostatectomy specimens can provide valuable information that is difficult to obtain by other means. Contrary to popular belief, the technique can be carried out in the routine histology laboratory with only minor modifications of existing methods. The use of this technique has provided valuable insight into the tumor biology of early stage prostatic cancer pointing to a multifocal origin for this disease. Likewise, the study of tumor volume, histological grade, and capsular penetration has provided a basis for the use of such prognostic markers in clinical management. The continuing development of new screening tools such as TRUS and MRI requires careful correlation with histopathology to assure a fundamental understanding of their abilities and limitations to detect and stage early-stage tumors. Only with such continued effort will diagnosis and clinical intervention allow us to make a meaningful impact on the natural history of this common malignancy.


The biology of prostate cancer: new and future directions in predicting tumor behavior. Because the present ability to treat and cure patients with prostate cancer is limited to those patients with pathologically organ-confined disease, it has become increasingly important to diagnose this disease at an early stage when cure is most likely. Recent advances in imaging may allow the urologist and pathologist to make the diagnosis of prostate cancer much earlier in the natural course of the disease. It therefore becomes imperative to have methods available to predict which patients have a high probability of progressing so that treatment can be assigned logically and appropriately. Our current methods of prognosis determination (stage and grade) do not allow accurate assessment of tumor behavior in the majority of individual patients with prostate cancer. Therefore, more accurate quantification of nuclear and cellular changes that take place as a tumor progresses to take on the aggressive (metastatic) phenotype are urgently needed. Experimental techniques have proven useful in answering these questions in animal models and now seem ready for large-scale testing in clinical studies.


Urothelial neoplasia.

Urothelial neoplasia. Urothelial neoplasia is a complex subject that can be only partially understood by careful study of the light microscopic features of individual lesions. Despite decades of study, our knowledge concerning the interaction of neoplastic events and host responses remains rudimentary. Most information has been collected by observing cases (usually in retrospect) that have been grouped according to relatively arbitrary criteria based on the phenotypic appearances of lesions as they are viewed through the light microscope. When evaluating human disease, we are always forced to reason backwards to determine the most likely histogenesis and to project forward to assess the most likely prognosis. Both types of reasoning must be filled with conjecture since direct observations from the initial events to the end results are not possible. Under these constricting circumstances, a conceptual framework into which our often anecdotal observations can be placed is more important than we would like to admit. With this in mind, I have taken advantage of the monograph format to risk a speculative approach to the subject, at least as it applies to the significance of the pathological features. In the past, we have accepted the view that all human hosts are essentially the same and that variations in cancer type and behavior are related almost entirely to the genetic ingenuity of the cancer cells themselves. Perhaps we should now entertain the opposite view, that carcinogenic events are ubiquitous and that cancer in any individual patient represents only what that patient will allow to grow in his or her body. We have devoted almost all of our collective research energy to examining the tumor. I believe that the pace of future progress can be significantly increased if we can think of more ways to examine the patient.


Graves' disease and its retroorbital aspects. Graves' disease is a common, familial, but easily treated condition caused by unique autoantibodies which act as TSH agonists. Patients with the diagnostic eye signs of Graves' disease, however, require more careful treatment than those patients with principally thyroidal involvement because destructive therapy to the thyroid gland may exacerbate the eye disease. The cause of ophthalmic eye disease appears to be "crossover specificity" by the immune system for a recurrent antigen in extraocular muscles, fibroblasts, and the thyroid gland. Treatment directed at the autoimmune response may offer the most appropriate therapy in the years to come.


Established and new uses of intravenous immunoglobulin. We know much about the biologic activities of the immunoglobulin molecule. We know its structure, and much about its function. However, I think that surprises are still ahead of us. As we become more familiar with what the immunomodulation doses of IVGG can do, I think we will find other uses of IVGG relying on antiidiotypic antibodies and possibly other cell-mediated functions.


Clinical and genetic associations in Marfan syndrome and related disorders. Although Marfan syndrome has been a recognized clinical entity for nearly a century, only in the early 1950s were its manifestations and genetic features firmly and fully established. Similarly, although the identification of the basic defect in Marfan syndrome had been vigorously pursued for several decades, it was only in 1991 that two independent reports implicated fibrillin as the defective gene product. Surprisingly and serendipitously, these studies also revealed genetic heterogeneity of the fibrillin proteins and established linkage between one of these loci and a Marfan-related disorder, congenital contractural arachnodactyly. Like Marfan syndrome, this condition is accompanied by skeletal abnormalities; however, flexion joint contractures replace the loose-jointedness of Marfan syndrome and, more importantly, neither the eye nor the aorta are affected. More recently, a similar association with the fibrillin gene has also been established in the dominantly inherited form of ectopia lentis. These associations of structurally related gene products with Marfan and related syndromes may conceivably imply that other connective tissue disorders are caused by mutations in these or other yet undiscovered fibrillin genes.