HYPOXIA REGULATES EXPRESSION OF THE ENDOTHELIN-1 GENE THROUGH A PROXIMAL HYPOXIA-INDUCIBLE FACTOR-I BINDING-SITE ON THE ANTISENSE STRAND

Endothelin-l (ET-1) is a peptide hormone with potent vasoconstrictor p roperties that is synthesized and secreted predominantly by vascular e ndothelial cells. Its production is regulated by numerous stimuli incl uding ischemia and hypoxia, and the enhanced levels that occur during myocardial ischemia may contribute to the progression of heart failure . We previously reported that ET-1 expression was induced by both hypo xia and transition metals in endothelial cells (ECs). Here we define a n element in the proximal promoter of the ET-1 gene that is responsibl e for this induction. By using deletions and site directed mutagenesis of the human ET-1 promoter, in combination with electrophoretic gel m obility shifts and transient expression assays in human ECs, we identi fied an active hypoxia-inducible factor 1 (HIF-1) binding site startin g at position -118 upstream of the transcription start site on the non -coding DNA strand. Mutation of this site eliminated induction by hypo xia without affecting basal (aerobic) expression, and the mutated sequ ence did not display hypoxia-specific binding of HIF-1. (C) 1998 Acade mic Press.