Progesterone-dependent binding of a trans-acting factor to the uteroglobin promoter

A trans-acting factor that specifically binds to the uteroglobin (UG) gene promoter has been identified. Binding activity was absent in non-target tissues (lung, liver) in HeLa cell nuclear extracts, and in target tissue (endometrium) in the absence of progesterone. Mixing experiments revealed an inhibitor of promoter binding in the absence of progesterone and in nonspecific nuclear extracts. Inhibition of binding in the endometrium was reversed by the action of progesterone. The results suggest that binding of a transcription regulatory factor to the UG promoter switches from negative to positive with the action of progesterone. The binding activity corresponds to the expression of the UG gene and this protein may be, therefore, a coordinately regulated trans-acting factor which regulates UG in a tissue-specific manner.