Actin Contributes to the Hyperexpression of Baculovirus Polyhedrin () and as a Component of Transcription Initiation Complex (TIC).

Hyperexpression of and , two very late genes, is one of the remarkable characteristics in the baculovirus life cycle. However, the mechanisms underlying the hyperexpression of these two genes are still incompletely understood. In this study, actin was identified as a highly potential binding partner of and promoters by conducting DNA pull-down and LC-MS/MS analyses. Inhibiting actin dynamics delayed and decreased the transcription of and . Actin interacted with viral RNA polymerase and transcription regulators, and the nuclear import of viral polymerase was inhibited with the disruption of actin dynamics. Simultaneously, the high enrichment of actin in and promoters discovered via a chromatin immunoprecipitation (ChIP) assay indicated that actin was a component of the viral polymerase TIC. Moreover, overexpression of actin surprisingly upregulated the expression of luciferase (Luc) under the control of and promoters. Taken together, actin participated in the hyperexpression of and as a component of TIC. These results facilitate the promotion of the expression efficiency of foreign genes in the baculovirus expression vector system (BEVS).