The effect of elevated levels of herpes simplex virus alpha-gene products on the expression of model early and late genes in vivo.

The rate of synthesis in vivo and the steady-state level of mRNA of four "model" herpes simplex virus type 1 (HSV-1) genes were measured as a function of high levels of alpha-gene products. The genes studied were ICP4 (alpha), deoxy-UTPase (beta), VP5 (beta gamma), and glycoprotein C (gC, gamma). Accumulation of high levels of alpha proteins was accomplished either by infection with an HSV-1 mutant, temperature-sensitive in ICP4 (ts606) at the nonpermissive temperature then shift-down to permissive temperature, or by infection with wild-type virus under cycloheximide blockage of protein synthesis followed by release. Compared to RNA expression in normal infections, beta gamma and gamma transcription rates were both transiently stimulated under the experimental conditions employed. The greatest effect was seen with the gamma-gC mRNA transcription rates. In addition, at nonpermissive temperatures with ts 606, the amount of expression of gC mRNA was significantly increased over normal early levels, in contrast to the case with the VP5 transcript. The impact of such results on models of HSV gene expression in vivo are discussed.