CHARACTERIZATION OF THE HERPES-SIMPLEX VIRUS TYPE-2 (HSV-2) US2 GENE-PRODUCT AND A US2-DEFICIENT HSV-2 MUTANT

The herpes simplex virus type 2 (HSV-2) US2 gene product was identifie d by using a rabbit polyclonal antiserum raised against a recombinant 6 x His-US2 fusion protein expressed in Escherichia coli. The antiseru m reacted specifically with a 39 kDa protein in HSV-2 strain 186-infec ted cell lysates. The protein was not detectable in the presence of th e virus DNA synthesis inhibitor phosphonoacetic acid. Indirect immunof luorescence studies localized the US2 protein in the cytoplasm and as discrete granules at late times post-infection within and at the perip hery of the nucleus, and nuclear fractionation studies showed that the protein was partially associated with the nuclear matrix of infected cells. The protein was easily detected in purified virions. Also, a US 2 insertion mutant was constructed which contained an ICP6-lacZ insert ion in the US2 gene. This mutant was as virulent as wild-type virus in mice when inoculated by the footpad route. The importance of the US2 protein of HSV-2 in the virus life-cycle may be apparent only in the n atural human host.