Effects of nucleoside analogs on transcription of simian virus 40

Brief incubation of BSC-1 cells with 5-fluorouridine (FUrd) produces an irreversible inhibition of RNA synthesis. The drug has no effect on the appearance of nuclear T-antigen or on the rate of viral DNA synthesis during lytic infection of BSC-1 cells. The ultimate yield of infectious virus is inversely related to the length of exposure to FUrd before infection. We have also followed the synthesis of virus-specific RNA in 3T3 cells transformed by SV40. The relative amount of hybridizable, virus-specific RNA in the cytoplasm of 3T3 cells transformed by SV40 and treated with FUrd is at least equal to or greater than in control, untreated cells. A strong inhibition of virus-specific RNA is found in cells treated with 5-bromotubercidin. These findings are consistent with previous conclusions that FUrd selectively inhibits rRNA but not mRNA synthesis, whereas 5-bromotubercidin reversibly inhibits both mRNA and rRNA.