FIG. 6.

Models for transcriptional regulation on the vitamin D3-responsive gene with or without the CCAAT box. On CCAAT box-containing genes, in the absence of vitamin D3 induction the NF-Y complex is located on the CCAAT box and presets GTFs and RNAPII. When induced by vitamin D3, transcriptional coactivators such as SRC-1/p300 are recruited by VDR-RXR independently of NF-Y and stimulate histone acetylation (indicated as Ac) on the promoter, leading to transcriptional activation and gene expression. On genes lacking a CCAAT box, upon vitamin D3 induction VDR-RXR recruits coactivators (SRC-1/p300) and mediators (DRIP complex) and thereby causes recruitment of RNAPII and GTFs and acetylation of histones.