Effects of estradiol-receptor complexes on the template activity of human breast tumor chromatin

The interaction of estradiol-receptor complexes with isolated human breast tumor chromatin was studied under equilibrium conditions. Tumor samples were obtained from mastectomy specimens or biopsies. Chromatin was prepared from these samples and incubated with estradiolreceptor partially purified from cytosol rat uterus or from human hormone-dependent tumors. The two preparations gave similar results in the interactions with human chromatin. The in vitro transcription activity of chromatin from hormone-dependent tumors was dramatically increased by the addition of estradiol-receptor. Maximal enhancement was achieved with 70 fmoles of estradiol-receptor complex in the presence of 50 micrograms of chromatin. These changes in RNA synthesis were not detectable with chromatin isolated from autonomous breast tumors.