[Changes in DNA supercoiling during differentiation, aging and malignant transformation].

The data on changes in DNA supercoiling during cell differentiation, in vitro aging and SV40 virus-induced or spontaneous malignant transformation are discussed. The observed correlation between the level of cell proliferation and the density of DNA topological ("titratable superhelical") turns in the closed nuclear DNA loops, as well as the data on the effect of DNA supercoiling on transcription allow to suggest that the selective and co-ordinated switch in the transcription of genes involved in the control of cell proliferation may operate through total changes in the level of supercoiling of the closed nuclear DNA loops.