Intranuclear androgen-receptor complex binding sites of mouse submandibular gland.

Nuclear androgen-receptor binding sites in chromatin regions of mouse submandibular gland were studied. Cytosol androgen receptors prelabeled with [3H]androgen interacted with the crude nuclei in mouse submandibular gland and activation of the receptor was a prerequisite for this interaction. After in vivo administration of [3H]androgen to female mice, radioactivities were found in the nuclei purified from submandibular gland tissues and the [3H]androgen-labeled purified nuclei were further digested with micrococcal nuclease. The androgen receptor was found in solubilized, active chromatin fractions which contained mono- and dinucleosomes. By an in vitro exchange assay, endogenous androgen-receptor complexes associated with chromatin binding sites in intact males were found in the solubilized fraction after micrococcal nuclear digestion, whereas such complexes were not found in females. These results suggest that the androgen receptors translocated to the nuclei and became associated with chromatin and that this association occurred in transcriptionally active chromatin regions that were preferentially sensitive to micrococcal nuclease.