Stimulation of RNA polymerase I and II activities by 17 beta -estradiol receptor on chick liver chromatin.

The endogenous transcriptional capacity (RNA polymerase I and II activity) of liver chromatin from chicks treated with 17 beta-estradiol for 24 h (E 24) was double that of the controls. E 24 chromatin contained estradiol receptor activity while control chromatin did not. Its presence suggested an implication in the enhanced activities of RNA polymerases of E 24 chromatin. When semi-purified estradiol receptor was added to control chromatin, the endogenous transcriptional capacity of this chromatin was greatly increased. Studies with alpha-amanitin showed that both RNA polymerase I and II were stimulated by the estradiol receptor. This stimulation was observed as long as homology of the system was maintained. Solubilized homologous RNA polymerases were stimulated much less by the hormone complex in the presence of heterologous DNA than with homologous chromatin. Prokaryotic RNA polymerase could not be stimulated by chick liver estradiol receptor in the presence of heterologous DNA.