Purification and some properties of a deoxyribonucleic acid endonuclease endogenous to rat liver chromatin

A deoxyribonucleic acid (DNA) endonucleolytic activity has been purified from a 0.3 M KCl extract of rat liver chromatin by a combination of selective precipitation and ion-exchange and gel filtration chromatography. The purified protein has a molecular weight of 35 000 as determined by Sephadex G-200 gel filtration and sodium dodecyl sulfate-acrylamide gel electrophoresis. The nuclease activity is stimulated by the addition of Mg2+ and thus may represent the Mg2+-activated DNase endogenous to chromatin. The purified enzyme has the ability to make both single-strand nicks and double-strand cuts in DNA.