A novel cyclic adenosine 3',5'-monophosphate-responsive element involved in the transcriptional regulation of the lutropin receptor gene in granulosa cells.

The induction of the lutropin receptor (LHR) in granulosa cells by FSH is mediated, at least in part, by cAMP. However, the classic cAMP-responsive element (CRE) is not present in the 5'-flanking region of the rat LHR gene. Previous studies from our laboratory had shown that three Sp1 sites within the promoter region of the rat LHR (rLHR) bind Sp1 and Sp3 and are involved in the basal and cAMP-mediated transcription of the rLHR gene. In the present studies we show that the rLHR promoter region forms a complex (designated complex A) with nuclear extracts from rat granulosa cells, and the abundance of complex A is markedly increased when using cells that had been pretreated with 8-bromo (Br)-cAMP. We have localized the binding of the protein(s) in complex A to a DNA sequence immediately upstream and partially overlapping with the Sp1c binding site. The core site (designated SAS for Sp1c adjacent sequence) is localized to nucleotide (nt) -146 to -142 and contains the sequence GGGGG. The consensus sequence for the core portion of this element appears to be (G/T)GGGG. Mutations of the SAS site, but not SP1c site, abolish complex A formation. Experiments utilizing rat granulosa cells transfected with luciferase reporter genes driven by the 5'-flanking region of the rLHR gene demonstrate a functional role for the SAS site in the cAMP responsiveness of the rLHR gene.