Enhancement of S1 nuclease-susceptibility of negatively superhelical DNA by netropsin.

It was evidenced that the antibiotic netropsin enhances the single-strand-specific nuclease S1-susceptibility of negatively superhelical DNA. In contrast, an intercalating drug inhibited S1 action on the superhelical DNA. Negatively superhelical DNA is known to possess several (or a number of) unbasepaired sites sensitive to S1 cleavage. S1 cleaves generally the DNA once at these sites to result in production of the full-length linear form. However netropsin-bound DNA had a tendency to be cleaved by S1 simultaneously at plural sites producing several species of linear DNAs smaller than full-length size.