Pseudorabies virus (PRV) early protein 0 activates PRV gene transcription in combination with the immediate-early protein IE180 and enhances the infectivity of PRV genomic DNA.

Pseudorabies virus (PRV) early protein 0 (EP0) functions as a transactivator of the viral gene promoters. In transient expression assays employing chloramphenicol acetyl transferase (CAT) reporter constructs, EP0 and the immediate-early protein IE180 act in an additive manner to activate transcription from the thymidine kinase (TK) and glycoprotein G (gG) gene promoters. EP0 enhanced the synthesis of infectious virus in cotransfection experiments with the EP0-expression plasmid and PRV genomic DNA. EP0 was detected by Western blot analysis in the purified virions. These results may indicate that EP0 in the virions acts as an important transactivator to express the immediate-early gene efficiently in the first stage of infection, and IE180 and EP0 expressed after the infection cooperatively activate the early and late gene expression in the later stage of infection.