Functional analysis of transcriptional regulation of herpes simplex virus type 1 tegument protein VP22

The herpes simplex virus type 1 (HSV-1) tegument proteins have important functions in the viral replication process. In order to investigate the role of the HSV-1 tegument protein VP22 in viral replication, its transcriptional regulation of viral promoters was investigated using the chloramphenicol acetyltransferase (CAT) assay. The results indicate that VP22 exerts a dose-dependent transcriptional inhibitory effect on the HSV-1 alpha4, TK, and gC gene promoters. VP22 had the capacity to repress transcriptional activation of promoters via different viral transcription regulatory factors such as VP16 and ICP0, as evidenced by the specific repression of the TK and gC gene promoters by ICP0. In addition, VP22 was capable of inhibiting the promotion of ICP0 transcriptional activation in the presence of HAT PCAF, which is even more remarkable than the VP22 repression of ICP0 transcriptional activation. Finally, the transcriptional inhibitory effect of VP22 on other viral promoters was demonstrated by the analysis of beta-galactosidase activities in internal controls.