1,25-Dihydroxyvitamin D(3) [1,25(OH)(2) D(3)] exerts its biological effects by binding to the vitamin D receptor (VDR), which binds in turn to the vitamin D response elements located in the target gene's promoter. We have previously demonstrated that VDR binds in vitro with high affinity to the 5'-flanking sequence of the human growth hormone (hGH) gene. In this study, we analyzed the response to 1,25(OH)(2) D(3) of hGH-promoter constructs introduced by transfection into the MCF-7 human adenocarcinoma cell line. We found that the transcriptional activity of some of these constructs was markedly reduced by 1,25(OH)(2) D(3). Deletion analyses revealed that a 34-bp sequence located between positions -62 and -29 upstream of the transcription start site is sufficient for this repressive response. This conclusion was also confirmed by gel mobility shift assays. Our results indicate that vitamin D inhibits hGH gene transcription, directly or by interference with other transcription factors.
(C)2002 Elsevier Science (USA).