Evidence for variation of supercoil densities among simian virus 40 nucleoprotein complexes and for higher supercoil density in replicating complexes.

The distribution of DNA topoisomers in intracellular simian virus 40 DNA was analyzed by gel electrophoresis. The results suggested that DNA extracted from 70S chromatin had a different superhelical density distribution as compared with the DNA obtained from virions or virion assembly intermediates. The heterogeneity of simian virus 40 viral DNA superhelical density at a late time after infection was partly due to increased virion production and partly due to the intrinsic heterogeneity of the superhelical density of DNA extracted from virions. Using two-dimensional gel electrophoretic analysis we also showed that simian virus 40 DNA templates used for DNA replication have a higher average superhelical density than the bulk of intracellular viral DNA.