PERSISTENCE OF RIBOSOMAL-PROTEIN SYNTHESIS AFTER INFECTION OF HELA-CELLS BY HERPES-SIMPLEX VIRUS TYPE-1

Because synthesis of rRNA persists late during herpes simplex type 1 i nfection and because S6 phosphorylation is always correlated with effi cient translation of ribosomal protein mRNA, we tested the hypothesis that ribosomal protein synthesis and ribosome biogenesis could persist after infection. At different times after infection, proteins were la belled with S-35 for 1 h before harvesting and ribosomes were purified , Measurement of radioactivity incorporated into individual ribosomal proteins separated by two-dimensional PAGE demonstrated that ribosomal proteins are still synthesized and assembled into mature ribosomes up to late times during infection, while synthesis of beta-actin is seve rely inhibited, During expression of late genes, ribosome biogenesis w as estimated to be 58% of that of the control as judged by [H-3]uridin e incorporation into rRNA, As for beta-actin mRNA, the level of riboso mal protein mRNA decreased progressively from the beginning of infecti on, reaching about 30% of the control level during expression of late genes, Taken together, these results demonstrate that ribosomal protei ns are still synthesized up to the late time of infection and efficien tly assembled into mature ribosomes, while there is a severe shutoff o f the synthesis of other cellular proteins.