Inhibition of Protein Synthesis by Vaccinia Virus. II. Studies on the Role of Virus-induced RNA Synthesis

Abstract

Cytoplasmic RNA synthesis can be detected in vaccinia virus-infected [human cervical carcinoma] HeLa cells in the presence of 2 .mu.g/ml, but not 20 .mu.g/ml, of actinomycin D. When RNA synthesis is observed protein synthesis is inhibited in infected, treated cells. Such a correlation may also be observed in infected, cycloheximide-treated cells. If actinomycin D (20 .mu.g/ml) is added to these cells at various times after infection and treatment, the inhibition of protein synthesis seen upon removal of cycloheximide does not continue beyond the point to which it developed before the actinomycin D was added. The inhibition of protein synthesis can be correlated with the amount of cytoplasmic RNA synthesized in infected cells and this RNA synthesis and the subsequent inhibition of protein synthesis can be prevented by sufficiently high concentrations of actinomycin D. The cytoplasmic RNA which is synthesized does not appear to consist of double-stranded RNA or of extensive self complementary regions. The cytoplasmic RNA synthesized in infected, cycloheximide treated cells appears to consist of early virus mRNA which can function as mRNA in vitro in a cell-free system derived from normal cells. An examination of the phosphorylation of ribosomal proteins shows 6 additional phosphoproteins in infected cells, 2 of which may be observed in infected cycloheximide-treated cells, suggesting that phosphorylation of ribosomal proteins cannot be directly correlated with the inhibition of overall protein synthesis seen in infected cycloheximide-treated cells.