Regulation of herpes simplex virus type 1 DNA synthesis: temperature-shift studies with DNA-negative temperature-sensitive mutants.

The regulation of expression of viral genes involved in the synthesis of herpes simplex virus type 1 DNA was studied using three DNA- temperature-sensitive (ts) mutants (B, C, and D). These mutants were examined for their ability to synthesized viral DNA and polypeptides following temperature shift-down in the presence or absence of the transcription inhibitor actinomycin D. The results demonstrated that the B gene product is required transiently early in infection and apparently controls a transciptional step required for HSV DNA synthesis. The C gene product is required continuously during infection and also controls a transcriptional step needed for viral DNA synthesis. In contrast, the product of the D gene does not directly control a transcriptional step, is required continuously, appears to be directly involved in HSV DNA synthesis, and is probably the gene for viral DNA polymerase. The results further showed that recovery of viral DNA and polypeptide synthesis following temperature shift-down in the absence of inhibitor was greater for the D mutant than for the mutants blocked in viral DNA synthesis at the level of transcription.