Differences in heavy-ion-induced DNA double-strand breaks in a mouse DNA repair-deficient mutant cell line (SL3-147) before and after chromatin proteolysis

DNA double-strand breaks induced by X- or neon beam-irradiation in a DNA double-strand break-repair-deficient mutant cell line (SL3-147) were examined. The increase in the number of DNA double-strand breaks was dose depend after irradiation with X-rays and neon beams and was enhanced by chromatin-proteolysis treatment before irradiation. These results suggest that the induction of DNA double-strand breaks by ionizing radiation, including heavy-ions, is influenced by the chromatin structure. The chief biological effects of heavy-ion radiation are thought to be mediated by DNA damage. The extent of cell death after charged-particle irradiation may depend on unrepairable DNA double-strand breaks1). Recently, pulsed-field gel electrophoretic analysis has been used to study radiation-induced DNA double strand breaks in several mammalian species2-6). The number of DNA double-strand breaks induced by ionizin2 radiation is 2reater in vroteolvzed than in intact chromatin7).