Role of CACC-box in the regulation of ovine follicle-stimulating hormone receptor expression

Tissue-specific and stage-specific expression of follicle-stimulating hormone receptor (FSH-R) in granulosa and Sertoli cells is required for normal development of ovarian follicles and germ cells. However, little is known of the transcription factors that regulate the FSH-R gene and its promoter. Using an ovine FSH-R promoter as a model system, we have identified a second DNase I footprinting 2 (FP2) region from -46 to -67 of the strongest ovine FSH-R promoter (-200 to +163) relative to the transcription start site. Electrophoretic mobility shift assay with a 22-base pair DNA probe (-46 to -67) and nuclear extracts from Sertoli (15P1) and granulosa (JC-410) cell lines demonstrated a sequence-specific DNA-protein complex. Further Southwestern and UV cross-linking analyses detected three predominant proteins of molecular weights 87, 60, and 50 kDa present in both Sertoli and granulosa cells bound to a P-32-labeled DNA probe as a complex. Gel competition experiments with DNA probes containing known Krupple-like factor binding sites revealed that the testis-specific zinc finger protein, ZNF202-like factor, Ras-responsive element binding protein-like factor, or both, may be among the potential candidate regulators. Mutation within the CACC box of the promoter abolished Krupple-like factor binding and significantly diminished promoter activity in both gonadal cells. These data suggest that Krupple-like transcription factors may play a role in the regulation of ovine FSH-R expression.