Transformed estrogen receptor in the regulation of RNA synthesis in uterine nuclei

Abstract

The interaction of estradiol with uterine tissue involves the association of the hormone with an extranuclear receptor protein, followed by temperature dependent translocation of the resulting complex to the nucleus. During this process, the receptor undergoes transformation that can be recognized by an increase in its sedimentation rate from 3.8S to 5.2S, as well as acquisition of the ability to bind to isolated uterine nuclei and to alleviate a tissue-specific deficiency in their RNA synthesizing capacity. Receptor transformation can be effected in the absence of nuclei by warming uterine cytosol with estradiol. This preparation of transformed complex resembles that extracted from nuclei in its sedimentation rate (5.3S) and its ability to bind to uterine nuclei and augment RNA synthesis. It is proposed that receptor transformation is an important step in estrogen action, and that a principal role of the hormone may be to induce conversion of the receptor protein to a biochemically functional form.