Trans-activation of viral tk promoters by proteins encoded by varicella zoster virus open reading frames 61 and 62.

Plasmids containing the varicella zoster virus (VZV) open reading frames (ORFs) 61 and 62 were used in a transient co-transfection assay to test for trans-activation of the VZV and herpes simplex virus type 1 (HSV-1) thymidine kinase (tk) promoters. The trans-activating potential of the polypeptides encoded by these VZV ORFs, designated p51 and p140, was compared to that of their HSV-1 homologs ICP0 and ICP4, respectively. VZV p51 was functionally inactive in this system while p140 appeared to be a much stronger transcriptional activator than ICP4. Co-transfection of plasmids encoding VZV p140 and HSV-1 ICP0 resulted in a synergistic activation of the reporter gene as has been shown for the combination of ICP4 and ICP0.