A STEROIDOGENIC FACTOR-I BINDING-ELEMENT IS ESSENTIAL FOR BASAL HUMANACTH RECEPTOR GENE-TRANSCRIPTION

We have previously shown that the promoter of the human ACTH receptor (ACTH-R) contains, at -35 bp, a binding site for the steroidogenic fac tor 1 (SF-1), an orphan nuclear receptor which could be responsible fo r the transcriptional activity of this promoter. In the presence study , electrophoretic mobility shift assays demonstrated that the sequence -43/-19 bound the SF-1 protein present in the nuclear extracts of adr enocortical cells. Mutation of the SF-I binding site markedly reduced (40%) the basal transcription of the reporter gene in Y-1 cells transf ected with the mutated p(-56/+22)GN construct compared to the wild-typ e construct. These results demonstrate that the SF-I binding element p resent in this fragment is required for the basal promoter activity of the human ACTH-R gene, In addition, other binding elements located up stream from this characterized SF-l binding site are involved ire the full basal promoter activity of the human ACTH-R since transfection st udies with a longer p(-1017/+22)GH construct resulted in a higher GN r elease than with the p(-56/+22)GIP construct. (C) 1998 Academic Press.