Winding anomalies in nuclear DNA from malignant cells II. Functional implications.

A molecular mechanism is proposed by which physical, chemical and viral cancerogens together with DNA topoisomerases of type I effect an increase in the topological winding deficiency of nuclear DNA inside living cells. The resulting conformational changes of DNA, as monitored by an abnormally high negative superhelical density, could be of general relevance in the expression of the malignant cell phenotype.