Hormonal control of RNA polymerases in rat bone marrow nuclei. The action of erythropoietin and testosterone.

The cytodifferentiation of stem cells to mature cells in bone marrow is an appropiate system to study biochemical aspects of hormonal action. We have used this system to analyze the way how erythropoietin and testosterone regulate erythropoiesis at the molecular level. Experiments designed to correlate the biochemical action of both hormones and to determine their differential action on rat bone marrow nuclei DNA-dependent RNA polymerases are reported. The effect of both hormones on the synthesis of RNA by isolated nuclei derived from normal rats was studied. Erythropoietin enhances the activity of RNA polymerase type II while testosterone stimulates polymerase type I activity. Gel-electrophoresis analysis of nuclear RNA shows that erythropoietin enhances the synthesis of RNA species with sedimentation coefficients of 30S, 22S, 15S, and 9S. Testosterone stimulates the synthesis of the 28 and 18S RNA as well as 4S RNA. A model is postulated to explain the action of erythropoietin and testosterone on RNA synthesis by isolated rat bone marrow nuclei.