Pseudorabies virus early protein 0 transactivates the viral gene promoters

Pseudorabies virus (PRV) early protein 0 (EP0) contains the RING finger domain with homology to the immediate-early (IE) protein ICP0 of herpes simplex virus type 1 (HSV-1). EP0 was detected by indirect immunofluorescence in the nuclei of the cells transfected with EP0 expression plasmid as is the case in cells infected with PRV. In transient expression assays, EP0 trans-activated the PRV IE, thymidine kinase (TK) and glycoprotein X (gX) promoters, indicating that EP0, like ICP0 of HSV-1, is a transactivating protein.