Two Chromatin Fractions with Different Metabolic Properties of Non‐histone Proteins and of Newly Synthesized RNA

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Abstract
Digestion of chromatin with micrococcal nuclease under mild conditions results in the release of a minor chromatin fraction showing an increased RNA and non‐histone protein content, a fast turnover of the non‐histone proteins and the presence of rapidly labelled heterogeneous nuclear RNA (hnRNA) with half‐life of about 20 min. Further digestion of the chromatin leads to the elimination of about 19% of the initial chromosomal DNA, thus leaving a second chromatin fraction relatively resistant to nuclease attack. This fraction has a low protein and RNA content and contains only metabolically stable non‐histone proteins. No differences in the histone complement of the two fractions was found except for a 40% deficiency of H1 in the minor fraction.