BLEOMYCIN-INDUCED DNA LESIONS ARE DEPENDENT ON NUCLEOSOME REPEAT LENGTH

Treatment of cells or nuclei with bleomycin induces DNA lesions. We detect the presence of lesions as the release of fragments from bulk DNA when cells (or nuclei) are lysed in dilute alkali. To further characterize the lesions we have altered experimentally the average nucleosome repeat length and probed the lysate with nuclease S1 in order to remove single-stranded DNA. In salt-incubated nuclei with short average nucleosome repeat length (140-145 base pairs) (and also with long nucleosome-free stretches of DNA) one can induced fewer DNA lesions in the nucleosome-containing DNA as compared to nuclei with 190-195 base pairs average nucleosome repeat length. Hence the ability of bleomycin to induce DNA lesions is dependent on nucleosome repeat length. © 1989.