FUNCTIONAL-CHARACTERIZATION OF A 1.25-DIHYDROXYVITAMIN D-3 RECEPTOR-BINDING SITE FOUND IN THE RAT ATRIAL-NATRIURETIC-FACTOR PROMOTER

The classical action of the hormone 1.25-dihydroxyvitamin D-3 (VD) is the regulation of calcium metabolism. In contrast, the peptide hormone atrial natriuretic factor (ANF) is one of the few known nonclassical VD responding genes. We screened the promoter of the rat ANF gene and identified a typical VD receptor (VDR) binding site formed by a direct repeat of two hexameric core binding motifs spaced by three nucleotid es, between positions -907 and -891. Like most of the DR3-type VD resp onse elements this sequence is bound with high affinity (K-d = 0.53 nM ) by a heterodimer formed by VDR and retinoid X receptor. In a heterol ogous promoter context one copy of this sequence mediated an about fou rfold gene activation by VD and a half-maximal activation (EC(50)) val ue of 0.48 nM VD. This characterizes the identified sequence as one of the most potent VD response elements. (C) 1996 Academic Press, Inc.