(Ld)MNPV some natural variants lack p24 sequences (251).
Ac130: gp16, unknown function
Ac130 has the potential to encode a protein of 12.1 kDa (106 aa). In OpMNPV, the homologous protein GP16 was detected at 24 h p.i. and its levels increased through 120 h p.i. OpMNPV GP16 is N-glycosylated and not associated with purified BVs and ODVs. It localizes to cytoplasmic lamellar-like structures close to the nuclear membrane and to envelopes of viruses on their way from the nucleus to the cell surface (81). In AcMNPV, transcription of the gene ac130 could not be detected by microarray analysis (287).
Ac131: pp34, major polyhedral calyx protein
The phosphoprotein PP34 (38 kDa, predicted 29.1 kDa, 252 aa) is detected from 15 h p.i. and continues to be phosphorylated until 60-70 h p.i. inside infected insect cells. It is involved in the morphogenesis of the polyhedral envelope of baculoviruses and is part of the carbohydrate envelope of occlusion bodies called the calyx (278, 294). Electron-dense "spacers" present in wild-type AcMNPV-infected cells, are absent in pp34-null mutants (294).
Ac132: ac132, unknown function
The ac132 gene with a predicted product of 25.1 kDa (219 aa) is transcribed (287) and homologs are present in genomes of several other members of the genus Alphabaculovirus (Table 2), but no function has been associated with it.
Ac133: an, alkaline nuclease
All sequenced baculovirus genomes encode a homolog of alkaline nuclease (AN) (Table 2 and Table 3). The predicted molecular mass of the AcMNPV AN is 48.3 kDa (419 aa). AN protein is present in two forms, one full length (53 kDa) and a shorter form (43 kDa). Both forms are found at low levels from 12 h p.i., with maximal abundance at 24 h p.i. (150). AN associates with LEF-3, the baculovirus ssDNA-binding protein (185). AN has 5' to 3'exonuclease and 5' to 3' endonuclease activity. Both these enzyme functions are involved in DNA recombination and replication (185, 186). The first attempt to produce an AcMNPV an-null virus was not successful, suggesting that an is an essential gene (150). Transfection with an AcMNPV an-null bacmid shows no BV production and a reduced number of normal-appearing nucleo-capsids. Instead, numerous aberrant capsid-like structures are formed, indicating a defect in nucleocapsid maturation or in a DNA-processing step, that is necessary for encapsidation (206, 207).
Ac134: 94k, unknown function
The 94k gene encodes a protein of 94.5 kDa (803 aa). The function of the 94K is still unknown, but homologs can be found in several other baculoviruses (Table 2 and 3). In the closely related BmNPV only 151 bps correspond to ac134 suggesting the gene might not be essential and was lost by a deletion (76). Random transposon insertions into the 94k gene have confirmed that it is not essential for virus replication (32). The 94k gene harbors the non-hr origin of replication, which is characterized by palindromes-and AT-rich regions. These motifs are essential for its ability to act as origin of DNA replication and are conserved in BmNPV (134).
Ac135: 35k/p35, apoptosis inhibitor
The gene p35 encodes the 34.8 kDa (299 aa) protein P35, which is a strong inhibitor of apoptosis The function of P35 and IAP proteins is extensively reviewed e.g. (36). Mutations in the p35 gene result in apoptosis of infected Sf21 cells and abort infection (37, 146), but have a wild type appearance in Tn368 cells (38). P35 blocks apoptosis by inhibiting the activity of Sf-caspase-1 and as such works at a different point in the caspase cascade as IAPs, which block apoptosis further upstream in the pathway (5, 140). Crystal structures of the interaction between P35 and Sf-caspase-1 have been determined (56). P35 gene expression is transactivated by IE-1 the protein, which is also responsible for inducing apoptosis (243).
Ac136: p26, unknown function
The gene p26 encodes a dimeric protein (monomeric 27.2 kDa, 240 aa) with unknown function, which is located primarily in the cytoplasm. Transcripts accumulate between 2-12 h p.i. (73, 248). Although conserved in most Alphabaculoviruse