wn function
The ac11 gene encodes a hypothetical protein with a predicted mass of 40.1 kDa (340 aa). Homologs found in many Alphabaculoviruses (Table 2) together form the DUF1386 family (176), but no particular motifs point towards a specific function.
Ac12: ac12, unknown function
This ORF encodes a hypothetical protein of 25.4 kDa (217 aa) with unknown function (9). The gene is not conserved among the Alphabaculoviruses; only in the related virus Rachoplusia ou (Ro)MNPV and in Lymantria dispar (Ld)MNPV homologous genes can be found. In the former the homologous gene is 25 codons shorter than in AcMNPV (92). Microarray analysis revealed transcripts of the gene, but its function remains unknown (287).
Ac13: ac13, unknown function
Ac13 codes for a hypothetical protein with a predicted mass of 38.7 kDa (327 aa). Homologs are conserved among all Alphabaculoviruses and are present in a few granuloviruses (Table 2 and Table 3). Transcripts were found by microarray analysis (287), but no function was assigned.
Ac14: lef-1, late expression factor 1
The gene product LEF-1 with a calculated mass of a 30.8 kDa (266 aa) is essential for DNA replication (133) and forms a complex with LEF-2 (ac6) (61). This interaction is required as non-interacting mutants of LEF-1 and LEF-2 do not promote transient DNA replication (61). LEF-1 contains a primase-like motif (61) and its primase activity was confirmed (187) based on the oligonucleotide synthesis on a poly (dT) template, which then allowed initiation of DNA synthesis by an exogenous DNA polymerase (Klenow enzyme). Lef-1 is a baculovirus core gene.
Ac15: egt, ecdysteroid UDP-glucosyl transferase
The egt gene encodes the enzyme ecdysteroid UDP-glucosyl transferase (EGT) (23.6 kDa, 201 aa). The gene is lost in some baculovirus lineages (100). This enzyme prevents insect molting by inactivating ecdysteroid hormones through transfer of glucosyl groups to these hormones (199). The presence of EGT during infection leads the development of larger insects, a longer time to death and a higher yield of progeny virus (41). Deletion of the egt gene makes baculovirus-based insecticides more effective by an early reduction of the feeding damage (200).
Ac16: bv/odv-e26; structural protein
The ORF ac16 encodes a structural protein (25.9 kDa, 225 aa) present in the envelopes of BVs and ODVs, named BV/ODV-E26 or briefly E26 (14). Ac16 is an early gene and transcripts accumulate rapidly after infection (213). Ac16 transcription initiates from a cryptic promoter sequence (87). When the ac16 locus (previously called DA26) was disrupted-maintaining the N-terminus -a virus with a few polyhedra (FP) phenotype was produced, which was still infectious and showed no difference in protein synthesis when mutant and wild type virus were compared (201). However, deletion of the ac16 homolog in BmNPV (Bm8) was not successful, indicating that this ORF may be essential (24). Multiple isoforms of E26 are present in infected cells, one isoform associates with viral DNA or DNA-binding proteins, a second one associates with intracellular membranes, likely due to palmityolation (24).
More recently, it has been shown that Ac16 contains a subdomain within the acidic transcriptional activation domain for binding with IE0 and IE1. Deletion of the ac16 gene results in an increased ratio of IE0 to IE1, but there was no effect on temporal production of these proteins nor on BV production nor on DNA replication (195).
Ac17: ac17, unknown function
Ac17 gene transcripts are present from the early to the very late phases and the encoded protein (18.5 kDa, 164 aa) localized in the cytoplasm of infected cells from 6 h p.i. (7). The gene ac17, together with pe38 (ac153), he65 (ac105), gp64 (ac128), ie2 (ac151), ac16, ac25 and pcna (ac49), is activated by the transactivator IE1 in the mammalian cell line Vero E6 (161). The function of the gene remains unknown, although transcriptional control is most likely. Deletion mutants of ac17 are infectious (139).
Ac18: da41, unknown function
The ac18 gene (da41) is expressed as a 40.9 kDa (353 aa) p