Early and late changes in nonhistone chromatin proteins accompanying rat liver regeneration.

Chromatin was isolated from 0.025 M citric acid nuclei of regenerating rat liver at 1,5,18,24, and 48 hr posthepatectomy. The total protein to DNA ratios did not change significantly during this time period. However, 2-dimensional polyacrylamide gel electrophoresis of nonhistone proteins of "Chromatin Fraction II" revealed changes in the amounts of some protein spots. As early as 1 hr after hepatectomy, decreases in size and intensity were detected for protein spots Bp, B24, C18, and CQ, and increases were detected for protein spots CBL and C13. Late changes in size and intensity were found for protein spots BA and CN, which decreased in size and intensity 5 hr after hepatectomy. The spot densities and sizes for most of the nonhistone proteins underwent no significant changes in the course of liver regeneration. The increases and decreases observed in specific protein spots represent an ordered series of changes in a limited number of nonhistone proteins.