Characterization of early simian virus 40 transcriptional complexes: late transcription in the absence of detectable DNA replication.

Isolation of early viral transcriptional complexes and incorporation in vitro of radiolabeled precursors into nascent RNA has permitted an analysis of early simian virus 40 (SV40) transcription. Under conditions such that viral DNA replication was undetectable, both early and late SV40 RNA were synthesized. This finding provides evidence that viral DNA replication is not an absolute requirement for late transcription and supports earlier observations that late viral RNA is synthesized in SV40-infected nonpermissive mouse cells. The majority of the early viral transcriptional activity can be solubilized, indicating that a substantial portion of this RNA is transcribed from free rather than integrated templates. Sedimentation analysis of the transcriptional complexes resulted in the detection of two separate peaks of activity, suggesting the possibility of two distinct types of early SV40 templates.