Autographa californica multiple nucleopolyhedrovirus PK1 is a factor that regulates high-level expression of very late genes in viral infection

Abstract

The remarkable ability of baculovirus is to hyperexpress very late genes, but the mechanisms remain unclear. Here we report the effect of PK1, a baculovirus-encoded serine/threonine kinase, on very late gene hyperexpression. PK1 knockout does not completely disrupt very late gene expression, but down regulates the hyperexpression. Those truncated PK1s that exhibit kinase activity in vitro rescue the decline of very late hyperexpression, while other truncated PK1s and a point mutant PK1 (D137A) without kinase activity fail to rescue the decline of very late hyperexpression, suggesting that PK1 regulates very late gene expression by its kinase activity. In addition, those PK1 mutants that can rescue the hyperexpression are able to interact with very late promoter containing 5' UTR. Based on the above data, we hypothesize that PK1 binds to very late promoter containing 5' UTR to regulate the hyperexpression of very late genes by its kinase activity.

Overexpression Bombyx mori HEXIM1 Facilitates Immune Escape of Bombyx mori Nucleopolyhedrovirus by Suppressing BmRelish-Driven Immune Responses

“…During transcriptional elongation, the phosphorylation of HEXIM1 by cAMP-PKA signaling results in the release of its inactive P-TEFb/HEXIM1/7SK snRNP complex for transcriptional elongation [32]. In addition, PK1, a protein kinase, is involved in the regulation of viral gene expression as a transcription factor in the very late phase [33] and it is also involved in the phosphorylation of viral RNA polymerase [34]. We, thus, hypothesized the potential role of BmHEXIM1 in regulating viral RNA polymerase phosphorylation.…”

Nucleocapsid Assembly of Baculoviruses

“…The main component of the preformed capsid is VP39, which is the richest protein in viral particles [26]. Interestingly, a lot of long empty tubular structures were detected within the matrix of the VS or accumulated at the edge of the nucleus in the insect cells when a variety of different individual viral genes were deleted from the viral genome, including ac53 [29], 38k [27], pk1 [1,35], vp1054 [36], bv/odv-c42 [31], p49 [31], bv/odv-ec27 [31], vlf-1 [37], and p6.9 [26], most of which are viral genes involved in nucleocapsid formation. It is unclear why the preformed capsid in cells transfected with these mutant viruses is not an empty capsid of suitable length, but an aberrant long tubular structure.…”

IE1 of Autographa californica Multiple Nucleopolyhedrovirus Activates Low Levels of Late Gene Expression in the Absence of Virus RNA Polymerase

“…Apart from the genes encoding the RNA polymerase subunits, an additional 15 genes have been identified from the AcMNPV genome to be involved in late gene expression, including ie1 , ie2 , lef1 to - 12 , p47 , dnapol , p143 , p35 , and pp3 1 ( 13 , 14 ). In addition, vlf1 , lef2 , and pk1 have been found to be involved in very late gene expression ( 15 – 17 ). Among these genes, dnapol , p143 , lef1 , lef2 , and lef3 , which encode a DNA polymerase, a helicase, a primase, a primase accessory factor, and a single-stranded DNA binding protein separately, as well as the immediate-early gene ie1 , are essential genes for viral DNA replication, while p35 , lef7 , lef11 , and ie2 are stimulatory ( 18 – 20 ).…”