Interaction of androgen receptors with chromatin and DNA

Controlled digestion of rat ventral prostate nuclei by careful adjustment of conditions of temperature, divalent cation concentration, ionic strength and micrococcal nuclease:DNA ratios yielded oligonucleosome fractions corresponding to less than 10% of the total genome which contain the majority of RNA polymerase B activity and androgen-receptor complexes of the nucleus. These parameters were affected acutely by androgen withdrawal and administration: furthermore, such manipulations affected the susceptibility to micrococcal nuclease release of prostate binding protein gene sequences. This transcriptionally-active androgen-influenced fraction was considered ideal for studies of interaction of chromatin components with androgen receptor protein. Androgen receptor was purified approximately 20 000-fold from rat prostate cytosol. The purified protein retained its ability to stimulate RNA polymerase B activity in prostate nuclei and chromatin fractions, and its properties of binding to chromatin and to DNA. However, although purified receptor protein showed tissue-specific binding to prostate chromatin and enhanced binding to fractions released by low nuclease digestion, no such specificity was indicated by binding to total DNA, DNA from specific fractions or cloned prostatic binding protein cDNA.