[Regulation of gene expression and vitamin]

Action of 1,25-dihydroxyvitamin D, the most active metabolite of vitamin D, is exerted by the nuclear vitamin D receptor (VDR) mediated gene expression. Toward the expression of vitamin D function, several steps including 1,25-dihydroxyvitamin D production, tissue specific expression of VDR and transcription of target gene by VDR are involved. One of the important progress in vitamin D metabolism is the cloning of 25-hydroxyvitamin D-24-hydroxylase gene and 1 alpha-hydroxylase gene. Structural organization of the human VDR chromosomal gene and its promoter was also important to understand the amount of VDR expressed in tissues. A part of mechanism of tissue specific expression of VDR have recently been reported. Furthermore, VDR recruit several coactivators to achieve vitamin D-induced transactivation. Selective coactivator interaction with VDR may specify the array of biological actions of vitamin D.