ISOLATION OF A HERPES-SIMPLEX VIRUS TYPE-1 MUTANT WITH A DELETION IN THE VIRION HOST SHUTOFF GENE AND IDENTIFICATION OF MULTIPLE FORMS OF THE VHS (UL41) POLYPEPTIDE

The virion host shutoff (vhs) gene (UL41) of herpes simplex virus type 1 (HSV-1) encodes a virion component that induces degradation of host mRNAs and the shutoff of most host protein synthesis. Subsequently, t he vhs protein accelerates the turnover of all kinetic classes of vira l mRNA. To identify the vhs (UL41) polypeptide within infected cells a nd virions, antisera raised against a UL41-lacZ fusion protein were us ed to characterize the polypeptides encoded by wild-type HSV-1 and two mutants: vhs1, a previously characterized mutant that lacks detectabl e virion host shutoff activity, and vhs-DELTASma, a newly constructed mutant containing a deletion of 196 codons from UL41. Two forms of the vhs (UL41) polypeptide were identified in cells infected with the wil d-type virus or vhs1. Wild-type HSV-1 produced a major 58-kDa polypept ide, as well as a less abundant 59.5-kDa form of the protein, while vh s1 produced 57- and 59-kDa polypeptides that were approximately equall y abundant. Although for either virus, both forms of the protein were phosphorylated, they differed in the extent of phosphorylation. While both vhs polypeptides were found in infected cells, only the faster mi grating, less phosphorylated form was incorporated into virions. vhs-D ELTASma encoded a smaller, 31-kDa polypeptide which, although present in infected cells, was not incorporated into virions. The results iden tify multiple forms of the vhs (UL41) polypeptide and suggest that pos ttranslational processing affects its packaging into virions, as well as its ability to induce mRNA degradation.