ACTION OF MITOCHONDRIAL DNAASE I IN DESTROYING THE CAPACITY OF ISOLATED CELL NUCLEI TO FORM GELS

Abstract

The enzymatic action of rat liver cell mitochondria in preventing the gelation of isolated rat liver nuclei under the influence of dilute alkali or molar sodium chloride solution is largely due to DNAase I action, although concomitant protease action has not been excluded. DNAase II apparently is not involved. DNAase I action from disrupted mitochondria accounts principally for the isolation by certain methods of rat liver nuclei that are incapable of gel formation. The action of the mitochondrial DNAase I in preventing gel formation by isolated nuclei is apparently due to its cleaving the DNA from the residual protein of the cell nuclei by attacking the DNA molecules close to points of attachment of the latter to the residual protein molecules. Crystallized DNAase I acts on isolated liver cell nuclei in a manner closely resembling the action of the mitochondrial enzyme. Sodium dodecyl sulfate will slowly cleave DNA from the residual protein of isolated liver cell nuclei at pH 6.0-6.3, but not at pH 7.0-7.5. Here DNAase I action is not involved.