VARICELLA-ZOSTER VIRUS (VZV) ORF32 ENCODES A PHOSPHOPROTEIN THAT IS POSTTRANSLATIONALLY MODIFIED BY THE VZV ORF47 PROTEIN-KINASE

Varicella-zoster virus (VZV) encodes five gene products that do not ha ve homologs in herpes simplex virus. One of these genes, VZV open read ing frame 32 (ORF32), is predicted to encode a protein of 16 kDa, VZV ORF32 protein was shown to be phosphorylated and located in the cytoso l of virus-infected cells. Antibody to ORF32 protein immunoprecipitate d 16- and 18-kDa phosphoproteins from VZV-infected cells. Since VZV en codes two protein kinases that might phosphorylate ORF32 protein, immu noprecipitations were performed with cells infected with VZV mutants u nable to express either of the viral protein kinases, Cells infected w ith VZV unable to express the ORF66 protein kinase contained both the 16- and 18-kDa ORF32 phosphoproteins; however, cells infected with the VZV ORF47 protein kinase mutant showed only the 16-kDa ORF32 phosphop rotein. Treatment of [S-35] methionine-labeled proteins with calf inte stine alkaline phosphatase resulted in a decrease in size of the ORF32 proteins from 16 and 18 kDa to 15 and 17 kDa, respectively. VZV unabl e to express ORF32 protein replicated in human melanoma cells to titer s similar to those seen with parental virus; however, VZV unable to ex press ORF32 was impaired for replication in U20S osteosarcoma cells. T hus, VZV ORF32 protein is posttranslationally modified by the ORF47 pr otein kinase, Since the VZV ORF47 protein kinase has recently been sho wn to be critical for replication in human fetal skin and lymphocytes, its ability to modify the ORF32 protein suggests that the latter prot ein may have a role for VZV replication in human tissues.