Nuclear protein redistribution in heat-shocked cells.

An increase was observed in the total protein mass of nuclei isolated from Chinese hamster ovary cells heated at 45 degrees C or 45.5 degrees C. An increase in the fractional recovery of DNA polymerase alpha and beta, and of DNA topoisomerase activity coincided with this increase in the protein mass of nuclei from heated cells. Nuclear protein mass which was soluble in 2.0 M NaCl decreased 0.5 fold, while DNA-associated and nuclear matrix-associated protein mass increased 2.2 and 3.4 fold, respectively. The results indicate that the increase in nuclear protein mass observed in nuclei from heated cells is due in part to an increased binding, or precipitation, of nuclear proteins onto the cell's DNA and nuclear matrix.