5,6-dichloro-1-beta-ribofuranosylbenzimidazole enhances premature termination of late transcription of simian virus 40 DNA.

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Abstract
Short RNA chains initiating at the major promoter sites for SV40 late transcription are elongated to approximately 450 nucleotides in a molar amount greater than that from any other region of the viral DNA. This conclusion is based on the following observations: Transcriptional complexes isolated by Sarkosyl and by hypotonic leaching (minichromosomes) from nuclei of [African green monkey kidney] cells infected with SV40 and intact nuclei were pulse-labeled in vitro with [.alpha.-32P]UTP and were observed to synthesize short RNA transcripts that hybridized predominantly to a SV40 DNA fragment spanning between 0.67-0.76 map units. In the presence of 5,6-dichloro-1-.beta.-D-ribofuranosylbenzimidazole (DRB), a drug known to accentuate premature transcriptional termination, accumulation of these short SV40 RNA chains was enhanced. When SV40-infected cells were pretreated with DRB and then labeled in vivo or in vitro, they synthesized short labeled viral RNA that hybridized almost exclusively with the DNA fragment spanning between 0.67-0.76 map units. These observations suggest a mechanism in the regulation of SV40 late transcription.