tial subunit of the RNA polymerase complex encoded by AcMNPV. Mutations in the conserved RNA polymerase motif showed the requirement of conserved asparagine residues (44) LEF-9 and LEF-8 interact directly (44) (see also ac40).
Ac63: ac63, unknown function
The Ac63 protein has a predicted mass of 18.5 kDa (155 aa) and does not contain any known conserved domains. Homologs are present in several Alphabaculoviruses (Table 2).
Ac64: gp37, spindle body protein or GP37
ORF ac63 encodes a glycoprotein with a predicted molecular mass of 34.8 kDa (P34.8, 302 aa) and is a homolog of the OpMNPV spindlin, which in that virus is a component of OBs (80). Baculovirus GP37 proteins are homologous to entomopoxvirus fusolins (221). Disrupting the gene in AcMNPV showed that the gene is not essential for virus replication nor affects virulence or speed of kill (34).
Ac65: dnapol, DNA polymerase
The ac65 gene codes for DNA polymerase (114.3 kDa, 984 aa) and is conserved among all baculoviruses. It is disputable whether it is essential for DNA replication in transient replication assays (133) or only stimulatory (169). Vanarsdall et al. (269) have shown using quantitative PCR (qPCR) that an AcMNPV-bacmid lacking dnapol cannot replicate its DNA in Sf9 cells.
Ac66: ac66, desmoplakin-like (ODV protein of unknown function)
The gene ac66 encodes a protein of 94.0 kDa (808 aa) and contains two conserved domains: a viral desmoplakin N-terminal domain and a CorA-like Mg2+-transporter region, respectively. Desmoplakin is the major component of desmosomes (253), which have a strong adhesive nature. They are involved in intercellular adhesion and participate in cell proliferation, differentiation and morphology (69). The CorA family consists of a group of membrane transporters of metal ions, abundant in prokaryotes, which can also be found in humans and yeast (196). The protein has been found in ODV nucleocapsids, but the exact localization is unknown (20). An ac66-null mutation resulted in depleted BV production due to inefficient transport of nucleocapsids from the nucleus to the cytoplasm. However, ac66 is not required for the formation of the nucleocapsids, but appears to be involved in pre-occluded virion and occlusion body formation (126).
Ac67: lef-3, late expression factor 3
The lef-3 gene is essential for DNA replication in transient replication assays (133). The 44.6 kDa (385 aa) LEF-3 protein binds to ssDNA (90). LEF-3 forms, together with P143 (helicase; see ac95) and IE-1 (see ac147), complexes with viral chromatin in infected cells (112). It has been proposed that LEF-3 interacts with P143 to stabilize the formed ssDNA after unwinding by the P143 helicase (112). LEF-3 also mediates nuclear localization of P143 (284) due to a nuclear localization signal domain which is required for interaction between LEF-3 and P143 (8).
Ac68: ac68, unknown function
All baculovirus genomes sequenced to date carry a homolog of the AcMNPV ac68 gene (Table 2 and Table 3), suggesting that it performs an important role in baculovirus biology. The conserved sequence is assigned as DUF708 domain, with unknown function (176). Ac68 is transcribed from 3 to 96 h p.i. and the gene product (22.3 kDa, 192 aa) was detected from 36 to 96 h p.i. (148). Deletion of ac68 did not affect production of infectious BVs, nucleocapsid or OB formation, nor did deletion of ac68 change the time to kill in vivo (148).
Ac69: mtase1, MTase1
Ac69 is a late gene (283) and its 30.4 kDa (262 aa) product stimulates late gene expression in vitro (149). The protein is homologous to E. coli FtsJ (148), an RNA methyltransferase and also has an S-adenosylmethionine (AdoMet)-methyltransferase domain. The protein binds AdoMet in vitro and has (nucleoside 2′-O)-methyltransferase activity, allowing coupling of methyl groups to RNA (283). Disruption of the ac69 gene does not affect virus replication in single-step growth curves (283), but the effect in vivo has not been analyzed.
Ac70: hcf-1, host cell-specific factor 1
The gene hcf-1 encodes a 34.4 kDa (290 aa) protein involved in the expression of la