Cross-linking and repair of DNA in sensitive and resistant strains of E. coli treated with nitrogen mustard.

Abstract

Changes in DNA synthesis and cross-linking following nitrogen mustard (HN2) treatment were compared in E. coli B strains having different HN2 sensitivities. The abnormally sensitive mutant, Bs1, was found to have its DNA synthesis suppressed by exposure to relatively low HN2 concentrations, compared with the parent strain, B(Hill), or the relatively resistant strain, B/r (ORNL). Cross-linked DNA, produced in strains B and B/r by HN2 treatment, was found to become converted during further incubation to a normally denaturable form. This did not occur in the Bg1 cells. These findings parallel the effects of UV on these strains, and suggest the existence of a general mechanism of DNA repair.