Binding of chlorozotocin and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea to chromatin and nucleosomal fractions of HeLa cells (original) (raw)

Both chlorozotocin and 1-(2-chloroethyl)-3-cyclohexyl-1nitrosourea (CCNU) bind specifically to the extended euchromatin fraction of the HeLa cell genome. After a 2-hr incubation of log-phase cells with each radiolabeled drug at 30 /(M, both alkylation (chlorozotocin and CCNU) and carbamoylation (CCNU) of nuclear chromatin were shown to be confined to late-eluting fractions from an ECTHAMcellulose chromatography column. These data were con firmed by enzymatic digestion of drug-treated nuclei with pancreatic DNase I (preferentially cleaves transcriptionally active chromatin). By following the kinetics of diges tion, the alkylated chromatin was preferentially solubilized by the enzyme. In addition, when compared to micrococcal nuclease digestions, both chlorozotocin and CCNU were shown to alkylate the DNA associated with the nucleosome core particle.