In vitro studies on mild alkali induced lesions in DNA

S1 nuclease hydrolysis, benzoylated naphthoylated DEAE cellulose (BND-cellulose) chromatography as well as certain immunological and genetic techniques have been used to evaluate the effect of mild alkali (pH10.0) on the DNA molecule. Native calf thymus DNA after exposure to alkaline pH10.0 when subjected to S1 nuclease hydrolysis released significant amount of acid soluble nucleotides as compared to the untreated control. With pBR322 DNA, the population of linear DNA species increased on S1 digestion with concomitant reduction in the supercoiled form. BND cellulose chromatographic studies also suggested the formation of single strandedness and/or distortions in the alkali treated DNA molecule. Antisera raised against the alkali treated DNA exhibited high cross-reactivity with both single stranded and Z DNA. Moreover, a significant reduction in transformation frequency of the treated DNA molecule compared with the untreated control further ascertained the structural alterations in DNA as a result of exposure to mild alkali.