Stimulation of uterine nonhistone protein phosphorylation and nuclear protein kinase activity by estradiol-17beta.

Changes in the phosphorylation of nonhistone chromosomal proteins have been followed in rat uterus stimulated by 17beta-estradiol. Isolated uteri were found to incorporate 32Pi into nonhistone proteins via an endogenous neclear protein kinase reactin. The rate of 32P labeling of nonhistone proteins and the activity of nuclear protein kinase(s) were found to be elevated over three- and two-fold respectively in uteri obtained from ovariectomized animals treated with estrogen. A dramatic change was observed in the radioactivity profile of 32P-labeled proteins fractionated via sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These observations are compatable with the hypothesis that phosphorylation of nonhistone proteins plays a role in the regulation of gene activity in the uterus.