Identification of a novel vitamin D response element from the rat genome

1 alpha,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], the active form of vitamin D3, has been thought to be a multifunctional agent. In order to discover novel roles of 1,25-(OH)2D3, we have been looking for new genes that are regulated by 1,25-(OH)2D3. Because the actions of 1,25-(OH)2D3 are mediated through the vitamin D receptor (VDR), that is a DNA binding transcription factor, vitamin D regulated genes should have VDR binding sites in their regulatory regions. In this paper, we describe a novel vitamin D response element (VDRE)-containing sequence, clone 3, which was isolated through binding to VDR. DNA sequence analysis of clone 3 did not reveal any significant similarity with sequences reported previously. Clone 3 had two regions consisting of a direct repeated sequence of AGTTCA motifs, both of which bound to VDR independently. Whereas each direct repeat sequence alone could not mediate transcriptional activation efficiently, with their co-existence there was a strong response to 1,25-(OH)2D3, indicating that these two direct repeated sequences act cooperatively.