Preferential binding of polycyclic hydrocarbons to matrix-bound DNA in rat-liver nuclei

The reactions of benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene metabolites and of r-7,t-8-dihydroxy-t-9,10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene with the DNA of matrix-bound and released chromatin fractions of rat-liver nuclei have been examined. Qualitatively there were no differences between the DNA-bound metabolites in each fraction but more binding to matrix-bound DNA occurred. Evidence was obtained that the increased binding of hydrocarbon to matrix-bound DNA was not dependent upon the proximity of hydrocarbon-metabolizing enzymes and Sephadex LH20 chromatography showed that the differences between the fractions were not due to contamination of DNA with residual proteins. The conformation of the matrix-bound chromatin may make its DNA more accessible to reactive metabolites than that of released chromatin.