1α,25(OH)2D3-induced transrepression by vitamin D receptor through E-box-type elements in the human parathyroid hormone gene promoter

Although transactivation by the liganded vitamin D receptor (VDR) is well described at the molecular level, the precise molecular mechanism of negative regulation by the liganded VDR remains to be elucidated. We have previously reported a novel class of negative vitamin D response element (nVDRE) called 1 alpha nVDRE in the human 25(OH)D(3)1 alpha-hydroxylase[1 alpha(OH)ase] gene by 1 alpha,25(OH)(2)D-3-bound VDR. This element was composed of two E-box-type motifs that bound to VDIR for transactivation, which was attenuated by liganded VDR. Here, we explore the possible functions of VDIR and E-box motifs in the human (h) PTH and hPTHrP gene promoters. Functional mapping of the hPTH and hPTHrP promoters identified E-box-type elements acting as nVDREs in both the hPTH promoter (hPTHn-VDRE; - 87 to - 60 bp) and in the hPTHrP promoter (hPTHrPnVDRE; - 850 to - 600 bp; - 463 to - 104 bp) in a mouse renal tubule cell line. The hPTHnVDRE alone was enough to direct ligand-induced transrepression mediated through VDR/ retinoid X receptor and VDIR. Direct DNA binding of hPTHnVDRE to VDIR, but not VDR/ retinoid X receptor, was observed and ligand-induced transrepression was coupled with recruitment of VDR and histone deacetylase 2 (HDAC2) to the hPTH promoter. These results suggest that negative regulation of the hPTH gene by liganded VDR is mediated by VDIR directly binding to the E-box-type nVDRE at the promoter, together with recruitment of an HDAC corepressor for ligand-induced transrepression.