Gene regulation by vitamin D3.

The physiologically active form of vitamin D3, 1 alpha,25-dihydroxyvitamin D3 (VD), is a nuclear hormone with pleiotropic action on the control of calcium homeostasis and bone formation, induction of cellular differentiation and apoptosis, inhibition of cellular proliferation, and other cellular signaling processes. The actions of the hormone are mediated by the vitamin D receptor (VDR), a transcription factor that is a nuclear receptor for VD and a member of the nuclear receptor superfamily. The structural relationship between the members of this transcription factor family suggests similar function in DNA binding, transactivation, and contact to other nuclear proteins. However, each nuclear receptor also demonstrates individual properties that are characteristic and not shared by its respective relatives. In this review, both common as well as individual characteristics of VDR-mediated transcriptional regulation are critically discussed.