Inhibitors of DNA synthesis: Their influence on replication and transcription of simian virus 40 DNA

Abstract

CV 1 cells infected with simian virus 40 were treated 27 hr after infection with inhibitors of DNA synthesis, and the fate of replicating viral DNA molecules was followed. Miracil D, chloroquine, cytosine arabinoside (ara-C) and hydroxyurea (HU) halted SV40 DNA replication within 20–30 min after addition. Miracil D and chloroquine act by preventing initiation of replication, while ara-C and HU prevent elongation of nascent DNA strands. This was demonstrated using the wild-type strain of SV40, as well as the thermosensitive tsA30 mutant of SV40; in the latter case the effect of the inhibitors was examined on the reinitiation of SV40 DNA synthesis after transfer of tsA30 infected cells from nonpermissive to permissive temperature. The inhibitory effect of fluorodeoxyuridine on SV40 DNA synthesis was partial, resulting in the accumulation of SV40 DNA component II molecules. Treatment with ara-C, HU, or fluorodeoxyuridine, had no effect on the rate of transcription of SV40 DNA, showing that continuous transcription of late SV40 genes does not require continuous replication of viral DNA. In contrast, treatment with miracil D or chloroquine resulted in inhibition (70–90%) of the overall rate of transcription of SV40 DNA.