Fractionation of liver chromatin.

Rat liver chromatin has been fractionated into two fractions on the basis of precipitability in standard saline after mild treatment with DNase II. The major portion of liver chromatin contains little nonhistone protein and is enriched in histones, while a minor portion of such chromatin, with which RNA polymerase is associated, is highly enriched in proteins other than histone and impoverished in histones. Although the relative concentrations of the several histone species present in two chromatin fractions are identical, binding of histones to DNA in the minor fractions appears to be modified, presumably by the presence of proteins other than histones.