Escherichia coli RNA polymerase in vitro mimics simian virus 40 in vivo transcription when the template is viral nucleoprotein.

We have used a low-salt detergent-free extraction procedure on cells infected with simian virus 40 to obtain viral nucleoprotein late after infection. Addition of EScherichia coli RNA polymerase and ribonucleotide triphosphates to the viral minichromosomes permitted transcription of RNA from viral templates. This synthesis was initiated predominantly within a fragment of DNA spanning 0.67 to 0.76 map unit on the genome. The synthesis from this region proceeded primarily along the "late" strand in a clockwise direction. These results were in contrast to the synthesis obtained with naked viral DNA in which initiation occurred on other regions of the genome and from which transcription proceeded counterclockwise along the early strand. These findings indicate that the nucleoprotein template or factors tightly associated with it may be responsible for site(s) and strand selection in transcription of simian virus 40.