a protein, which is located in the ODV-envelope (ODV-E28) (286). The conserved region of Ac96 is indicated as the baculovirus 19 kDa protein superfamily domain. AcMNPV ac96 is found within a four-gene cluster comprising of helicase, lef-5, ac96, and 38K (ac98). The relative positions of these genes are conserved in all baculovirus genomes (100).
Ac97: ac97, unknown function
Ac97 is predicted to be an early gene encoding a 6.5 kDa (56 aa) protein. A transcript overlaps this ORF (287). Homologs of this gene with unknown function have not been found in other baculoviruses (Table 2 and Table 3).
Ac98: 38k, 38K protein
The gene ac98 encodes the protein 38K (38.0 kDa, 320 aa) which is synthesized in the late phase of infection. The 38K protein is localized and distributed over the cylindrical sheath of the nucleocapsid of both BVs and ODVs and is required for nucleocapsid assembly, but not for DNA replication (281, 282). Furthermore, it interacts with the nucleocapsid proteins VP1054 (ac54), VP39 (ac89), VP80 (ac104) and itself (281). The ac98 belongs to the baculovirus core genes (Table 2 and Table 3).
Ac99: lef-5, Late expression factor 5
The gene ac99 codes for the late expression factor LEF-5 (31.0 kDa, 265 aa), which has significant sequence similarity in a stretch of 32 C-terminal amino acids with a zinc ribbon domain in the eukaryotic transcription elongation factor TFIIS (95). Unlike the cellular TFIIS, LEF-5 functions most likely as a transcription initiation factor and stimulates transcription mediated by baculovirus RNA polymerase from late and very late viral promoters at least in in vitro transcription assays (83).. The N terminal 194 amino acids are involved in LEF-5:LEF-5 self interactions and the 32 C-terminal amino acids of LEF-5 contain a putative Zn2+-ribbon domain (95). The acidic dipeptide DE within this domain is crucial for LEF-5 activity (83). Lef-5 is a core gene (Table 2 and Table 3).
Ac100: p6.9, major DNA-binding protein
The most abundant protein in the nucleoprotein core is a small (6.9 kDa, 55 aa), very basic (pI=12), protamine-like protein named: Basic Protein or P6.9. The positively charged arginine residues of P6.9 interact with the viral DNA genome to mediate DNA condensation in the nucleocapsid (127). In infected cells P6.9 is phosphorylated, but in nucleocapsid assembly this phosphorylation is inhibited by the presence of Zn2+(68). A model for this packaging has been proposed: during packaging of viral DNA, P6.9 is dephosphorylated by cellular phosphatases followed by DNA condensation. Phosphorylation of P6.9 by a capsid-associated kinase results in unpackaging of the nucleocapsid upon entry into cells, allowing the onset of the infection cycle (68). P6.9 is a baculovirus core gene.
Ac101: p40, BV/ODV-C42
The gene ac101 is transcribed at the late stage of infection. It encodes a 42 kDa protein (41.5 kDa predicted molecular mass, 361 aa), which is a component of the nucleocapsid of both BVs and ODVs (18). There is strong evidence that ODV-C42 is capable of direct interaction with the WASP-like protein P78/ 83 (ac9) and ODV-EC27 (ac144) (18). ODV-C42 probably binds to the viral protein P78/83 in the cytoplasm to form a protein complex, which then migrates to the nucleus during AcMNPV infection due to the nuclear localization signal in ODV-C42 (274). A mutant virus lacking ac101 is not able to propagate in cell culture as no mature nucleocapsids are formed, however, viral genome replication was not affected (270). Direct interaction between BV/ODV-C42 and a leucine zipper domain of EXON0 (ac141) enables egress of nucleocapsids from the nucleus to cytoplasm during the late phase of infection (64). Homologs of the gene ac101 are present in all sequenced baculovi-ruses except CuniNPV (249) (Table 2 and Table 3).
Ac102: p12, transport of G-actin
The transcription of the gene coding for the 12-kDa protein (13.3 kDa predicted, 122 aa) initiates from the consensus baculovirus late transcription start site (ATAAG) (166). Attempts to prepare a p12-mutant were not successful, suggesting that the gene is 