Tissue-specific factors and glucocorticoid receptors present in nuclear extracts bind next to each other in the promoter region of mouse mammary tumor virus.

Nuclear extracts from different mouse tissues have been used to study the interaction of factors with the steroid-inducible promoter of mouse mammary tumor virus. In addition to the glucocorticoid receptor that interacts with the distal region of the promoter, several tissue-specific proteins were found to bind to the 5' flanking region of the receptor-binding site and to the basal promoter region. The differences in the pattern of protection observed suggest that tissue-specific factors might co-operate with steroid receptors and result in a cell-type-dependent modulation of hormone action.