The biologically active metabolite of vitamin D3, 1α,25-dihydroxyvitamin D3 (1,25D), is a primary regulator of calcium homeostasis. 1,25D also controls cell differentiation and proliferation through binding to the nuclear vitamin D receptor (VDR). It regulates histone acetylation, chromatin remodeling, and recruitment of RNA polymerase II and ancillary factors required...