Expression of gamma interferon-dependent genes is blocked independently by virion host shutoff RNase and by US3 protein kinase

Gamma interferon receptor a (IFN-gamma R alpha) is stable but posttranslationally modified in herpes simplex virus 1(F) [HSV-1(F)]-infected cells. Studies with antibody directed to the phosphorylation site indicate that IFN-gamma R alpha is phosphorylated by the U(S)3 kinase. The modification is abolished in cells infected with Delta U(S)3, Delta U(L)13, or Delta(U(S)3/U(L)13) mutant virus. Transcripts of the IFN-gamma-dependent genes do not accumulate in cells transduced with the U(S)3 protein kinase and treated with IFN-gamma. In contrast, the accumulation of IFN-gamma dependent gene transcripts is suppressed in cells infected with the wild-type virus, in cells infected with the Delta U(S)3 mutant virus, and to a lesser extent in the Delta U(L)41 virus-infected cells. The accumulation of IFN-gamma dependent gene transcripts in Delta U(L)41-infected cells could be due at least in part to a significant delay and reduction in the accumulation of the U(S)3 protein. The results suggest that the expression of IFN-gamma-dependent genes is blocked independently by the degradation of IFN-gamma-dependent gene transcripts-a function of the virion host shutoff RNase-and by posttranslational modification of the IFN-gamma R alpha protein.