Hypoxia blocks in vivo initiation of simian virus 40 replication at a stage preceding origin unwinding.

Simian virus 40 (SV40)-infected CV1 cells transiently exposed to hypoxia show a burst of viral replication immediately after reoxygenation. DNA precursor incorporation and analysis of growing daughter strands by alkaline sedimentation demonstrated that SV40 DNA synthesis began with a lag of about 3 to 5 min after reoxygenation followed by a largely synchronous viral replication round. Viral RNA-DNA primers complementary to the SV40 origin region were not detectable before 3 min upon reoxygenation.