Simian virus 40 deoxyribonucleic acid transcription in vitro: binding and transcription patterns with a mammalian ribonucleic acid polymerase.

The in vitro transcription pattern of simian virus 40 (SV40) deoxyribonucleic acid (DNA) by a mammalian ribonucleic acid (RNA) polymerase, was studied by electron microscopy and velocity sedimentation techniques. It was found that (i) the majority of supercoiled SV40 DNA molecules displayed a single binding site for the enzyme, (ii) the supercoiled structure of SV40 DNA was frequently retained during transcription, and (iii) the majority of RNA molecules synthesized from the supercoiled SV40 DNA template showed no self-complementarity and sedimented relatively homogeneously in the 15S to 16S region of a sucrose gradient (in contrast, the RNA product synthesized from the nicked-circular SV40 DNA template showed self-complementarity and sedimented heterogeneously). RNA polymerase preparations isolated from SV40-infected monkey cells were more active than those isolated from uninfected monkey cells.