PARTIAL FRACTIONATION OF OESTRADIOL-BINDING CHROMATIN FROM DIMETHYLBENZANTHRACENE-INDUCED RAT MAMMARY TUMOUR

Abstract

SUMMARY The distribution of [6,7-3H]oestradiol-17β binding in chromatin from dimethylbenzanthracene-induced rat mammary adenocarcinoma was studied by differential centrifugation of sonicated nuclei. The evidence suggests that more oestradiol-17β is associated with the 'light' chromatin sedimenting at a higher centrifugal force than with the 'heavy' chromatin. Electron microscopy showed that heterochromatin was present in intact tumour nuclei, but it dispersed during isolation of the nuclei, and probably did not account for the fractionation of chromatin that occurred. No heterochromatin was observed in the centrifuged fractions. The template activity appeared to be higher in the fractions that had bound oestradiol. These results are compatible with the view that oestradiol binds to restricted regions of the chromatin and stimulates local increases in transcription.