Transcriptional activator of immediate-early (IE) gene products (alpha genes). Acts as a key activator of lytic infection by initiating the lytic program through the assembly of the transcriptional regulatory VP16-induced complex composed of VP16 and two cellular factors, HCFC1 and POU2F1. VP16-induced complex represents a regulatory switch: when it is on, it promotes IE-gene expression and thus lytic infection, and when it is off, it limits IE-gene transcription favoring latent infection (By similarity). May play a role in the aggregation of tegument proteins around nucleocapsids during virus morphogenesis. Associates with the VP16-induced complex; binding to host HCFC1 activates VP16 for association with the octamer motif-binding host protein POU2F1, to form a multiprotein-DNA complex responsible for activating transcription of the viral immediate early genes. Belongs to the herpesviridae tegument protein VP16 protein family.