DIRECT BINDING OF PROGESTERONE-RECEPTOR TO NONCONSENSUS DNA-SEQUENCESREPRESSES RAT GNRH

The mechanisms by which steroid receptors repress gene expression are not well understood. In this report, we show that progesterone recepto r (PR), in the presence of progesterone (P) directly represses rat gon adotropin releasing hormone (rGnRH) gene transcription. Deletion analy sis studies using transient transfection assays in GT1-7 neuronal cell s mapped the effects of P to sequences in the proximal rGnRH promoter between -171 and -73. This DNA sequence lacks any consensus steroid re sponse element binding sites. Cotransfection of a mutant progesterone receptor that lacks a functional DNA binding region (hPRcys) abolished repression of the rGnRH promoter by P. Gel mobility shift assays conf irmed that PR directly binds to the DNA fragments -171/-126, -126/-73, and -111/-73, which encompass the negative progesterone response elem ent (nPRE) of the rGnRH promoter. Mutagenesis of the rGnRH nPRE -171/- 126 DNA fragment resulted in a loss of PR binding. Thus, direct DNA bi nding of PR to nonconsensus elements in the proximal rGnRH promoter in hibits rGnRH gene expression.