PRESENCE OF DISTINCT CIS-ACTING ELEMENTS ON GONADOTROPIN GENE PROMOTERS IN DIVERSE SPECIES DICTATES THE SELECTIVE RECRUITMENT OF DIFFERENT TRANSCRIPTION FACTORS BY STEROIDOGENIC FACTOR-I

The nuclear receptor steroidogenic factor-1 (SF-1) regulates the cell- specific expression of the pituitary gonadotropin subunit genes. Sever al potential DNA-binding sites for SF-1, estrogen receptor (ER) and th e immediate-early transcription factor NGFI-A are found in LH beta gen es from many species. In this study, we have examined the action and i nteraction of these transcription factors on LH beta gene promoters fr om two representative vertebrate species, i.e. rat and salmon. Cotrans fection studies in COS-1 cells have shown that the action of SF-1 on s almon gonadotropin II beta (sGTHII beta) gene promoter was dramaticall y enhanced when combined with ER. The rat LHP promoter was activated b y SF-1 or ER individually, but these two factors, however, were unable to act in synergism on this promoter. In contrast, NGFI-A, specifical ly in cooperation with SF-1, transactivated the rat LH beta gene expre ssion but was ineffective on the sGTHII beta gene. Gel shift experimen ts showed that this lack of activation was due to the low affinity of the salmon NGFI-A-responsive element for its binding protein. In concl usion, our studies demonstrate that differential recruitment of distin ct transcription factors by SF-1 might be a common mechanism to activa te the cell-specific gonadotropin gene expression in different species . (C) 1997 Elsevier Science Ireland Ltd.