AD4BP SF-1 REGULATES CYCLIC AMP-INDUCED TRANSCRIPTION FROM THE PROXIMAL PROMOTER (PII) OF THE HUMAN AROMATASE P450 (CYP19) GENE IN THE OVARY/

Aromatase P450, which is responsible for the metabolism of C-19 steroi ds to estrogens, is expressed in the pre-ovulatory follicles and corpo ra lutea of ovulatory women by means of a promoter proximal to the sta rt of translation (PII). To understand how this transcription is contr olled by cAMP, we constructed chimeric constructs containing deletion mutations of the proximal promoter 5'-flanking DNA fused to the rabbit beta-globin reporter gene. Assay of reporter gene transcription in tr ansfected bovine granulosa and luteal cells revealed that cAMP-stimula ted transcription was lost upon deletion from -278 to -100 base pairs, indicating the presence of a functional cAMP-responsive element in th is region; however, no classical cAMP-responsive element was found. Mu tation of an AGGTCA motif located at -130 base pairs revealed that thi s element is crucial for cAMP-stimulated reporter gene transcription. When a single copy of this element was placed upstream of a heterologo us promoter, it could act as a weak cAMP-response element. Supershift electrophoretic mobility shift assay and UV cross-linking established that Ad4BP/SF-1 binds to this hexameric element. Ad4BP/SF-1 mRNA and p rotein levels and DNA binding activity are increased in forskolin-trea ted luteal cells. We conclude that cAMP-stimulated transcription of hu man aromatase P450 in the ovary is due, at least in part, to increased levels and DNA binding activity of Ad4BP/SF-1.