l capsid protein 91 and a chitin-binding peritrophin-A domain, respectively. The p95 gene belongs to the baculovirus core genes (Table 2 and Table 3). VP91 is associated with the capsid and envelope of ODVs (240). The second conserved domain belongs to the family of chitin peritrophic binding proteins and is able to bind chitin, which is present in a matrix lining the gut of most insects (58, 246).
Ac84: ac84, unknown function
The gene ac84 codes for a hypothetical protein (21.7 kDa, 188 aa) without any known conserved domain. The gene is transcribed (287).
Ac85: ac85, unknown function
Ac86: pnk/pnl polynucleotide kinase/ligase
The gene pnk/pnl is an immediate early gene encoding a protein (80.8 kDa, 694 aa) that contains two conserved domains: a kinase and a T4 RNA ligase domain (55). Deletion of pnk/pnl has no effect on virus replication in Sf21 cells or on protein production (55). The effect in pathogenesis in larvae is unknown.
Ac87: p15, unknown function
The gene p15 codes for a 15.0 kDa protein (126 aa) of unknown function. The protein does not contain known conserved domains, but homologs can be found in eight other Alphabaculoviruses (Table 2). For BmNPV P15 a function as a viral capsid protein was proposed due to high similarity with other viral capsid proteins. The transcription of the bm70 gene is regulated in time with a short early and a longer late transcript (171).
Ac88: cg30; unknown function
The ac88 gene product (30.1 kDa, 264 aa) harbors a zinc-finger-like and a leucine zipper motif, a characteristic found in proteins involved in gene regulation (215). cg30 is transcribed as an early monocistronicRNA and as the second cistron of an abundant late bicistronicRNA together with vp39 (259), but a CG30-beta-galactosidase fusion proteinwasmainly observed early in the infection process (215). cg30 is not essential for virus replication in vitro and in vivo, but the wild type virus accumulated to slightly higher titers over the cg30 deletion mutant after several passages in cell culture (215).
Ac89: vp39, major viral capsid protein VP39
The VP39 (39.0 kDa, 357 aa) is the most abundant structural protein of the nucleocapsid (260) with monomers arranged in stacked rings around the nucleoprotein core as reviewed in (249). VP39 is involved in the rearrangement and polymerization of host actin (28, 29). Recent results have shown that VP39 interacts with the 38K protein in infected insect cells (281). The vp39 gene is transcribed at late time points in infection from a promoter sequence containing three A/GTAAG consensus motifs (maximal transcription 12-24 h p.i.) as a bicistronic mRNA together with cg30 (259, 260). Vp39 is a core gene.
Ac90: lef-4, late expression factor 4
The lef-4 gene encodes the 55 kDa late expression factor 4 (predicted molecular mass 53.9 kDa, 464 aa) (54). LEF-4 is a subunit of the AcMNPV RNA polymerase (88) (see ac40) and is essential for late gene expression (132). LEF-4 has guanylyltransferase (84), RNA 5'-triphosphatase and ATPase activities (119), and appears to be a complete mRNA capping enzyme. The lef-4 gene is present in all baculoviruses (Table 2 and Table 3).
Ac91: ac91, unknown function
Ac91 potentially encodes a 24.1 kDa (224 aa) protein expressed in the late phase of infection and the gene is transcribed (287). The protein has an N-terminus rich in hydrophobic amino acids, including a stretch of 7 isoleucine residues, and a large central domain consisting of mainly proline, threonine and serine residues. The C-terminal domain, which is preceded by a methionine, is also present in some other baculovi-ruses, suggesting that the protein encoding region may be smaller than the entire ORF (not published).
Ac92: ac92/p33, unknown function, P33
Ac92 is a baculovirus core gene encoding a 33 kDa (predicted 30.9 kDa, 259 aa) protein (P33). Inactivation of this gene is lethal for the virus, indicating that ac93 is an essential baculovirus gene (230). P33 forms a complex with the mammalian tumor suppressor protein P53, when AcMNPV is used as a p53 gene expression vector, P33 also enhances P