Proteins and the functional properties of the chromatin fractions from the nuclei of the normal liver and of experimental hepatomas

: Chromatin fragments generated in normal liver and solid hepatoma nuclei due to the action of endogenous nucleases and in ascites hepatomas nuclei treated with micrococcal nuclease differ in the ability to be released from the nuclei into a medium of low ionic strength. It is suggested that such a fractionation is based on different solubility of DNP fragments attached to the nuclear skeleton and of those that are not bound with it. DNP fragments extracted in a low-salt buffer contain all five histones with a negligible admixture of nonhistone proteins having the protein/DNA ratio about 1.1. No endogenous RNA-polymerase activity could be detected in these DNP fragments. The bulk of the RNA-polymerase activity is found in the matrix-associated DNP fragments that appear to be enriched in nonhistone proteins (their protein/DNA ratio amounted to 2.5). The possibility that transcribable DNP fragments are associated with the matrix through low-salt-stable linkages like those in the DNA-(RNA-polymerase-RNA or RNP)-matrix seems to be confirmed by the data obtained.