es their phosphorylation activity is inhibited. Wild type AcMNPV shows a reduced eIF2α phosphorylation and increased translational activity, compared to a pk2 deletion mutant (51).
Ac124: ac124, unknown function
Ac125: lef-7, late expression factor 7
The lef-7 gene is transcribed early in infection from an initiation site 14 to 16 bp upstream of the putative translational start site and transcribed late in infection from a not determined initiation site more upstream (194). LEF-7 (26.6. kDa, 226 aa) is required for maximum late reporter gene expression (167). Deletion of lef-7 results in decreased BV and ODV production and DNA replication compared to the wild type virus infection (30). In BmNPV deletion of lef-7 also resulted in decreased levels of viral DNA replication (77). Furthermore, lef-7 is required for efficient homologous recombination in the presence of all other DNA replication genes (45).
Ac126: ac126, chitinase (ChiA)
The AcMNPV chitinase protein (ChiA) has a predicted molecular mass of 61.4 kDa (551 aa). ChiA accumulates in the endoplasmatic reticulum due to the presence of a signal peptide and a KDEL-retention signal (241, 261). Its release upon cell death is mediated by P10 (ac137) (261). ChiA is -together with the protease cathepsin (V-CATH; ac127) -required for disruption of the chitin skeleton of the host (96). The resulting liquefaction of the insect enables the efficient spread of viral occlusion bodies. ChiA is also prerequisite for processing of v-CATH from an inactive proenzyme (102). As a consequence deletion of chiA (+/-v-cath) from baculovirus expression vectors is used to reduce recombinant protein degradation (120). The chiA genes are present in many Alphabaculovi-ruses and some Betabaculoviruses and may have been picked up later in baculovirus evolution (Table 2 and Table 3).
Ac127: v-cath, cathepsin
The protease cathepsin (V-CATH) (predicted size 36.9 kDa, 323 aa) is activated from an inactive precursor by ChiA (ac126) and both proteins (V-CATH and ChiA) are required for the liquefaction of the insect host to allow efficient spread of OBs (96). V-CATH is also activated by chaotropic agents like SDS and its activity is inhibited by the protease inhibitor E64 (103). As, the chiA genes, the v-cath genes are also present in many Alphabaculoviruses and some Betabaculoviruses, but not all these viruses have both chiA and v-cath genes (Table 2 and Table 3).
Ac128: gp64, major budded virus envelope glycoprotein
In AcMNPV-infected Sf9 cells, the gene gp64 is transcribed both early and late in infection (116). GP64 (58.6 kDa predicted size, 512 aa) is absolutely essential for cell to cell spread of BVs. GP64 occurs as a covalently bonded trimer and is present on the surface of infected cells and is acquired by virions during budding through the plasma membrane, the final step in the release of BVs (212). GP64 is involved in host-receptor binding and is sufficient alone to mediate low-pH-triggered membrane fusion during intra-cellular trafficking (177). A domain in the N-terminal part (aa 21-159) is thought to be involved in host-receptor binding (292) and fusion and oligomerization domains have also been identified (192). The GP64 transmembrane region plays a crucial role in membrane fusion and is also required for GP64 trafficking and the budding process (154). The crystal structure of the GP64 post-fusion form revealed structural homology with the vesicular stomatitis virus G and herpes simplex virus type 1 gB proteins (121).
Ac129: p24, viral capsid protein
The gene ac129 is transcribed in the late phase of virus infection, initiated from a canonical late pro-moter sequence (GTAAG) situated immediately up-stream of the coding sequence (75). P24 (22.1 predicted molecular mass, 198 aa) is a capsid-associated protein, which is not N-glycosylated, but its precise function is unknown. Transposon-based interruption of the p24 gene did not affect viral propagation in cell culture (75, 242, 280). In SpltNPV, the homologous protein is associated with ODVs as a complex of 83 kDa (155). For Lymantria dispar 