title: Vitamin D-dependent recruitment of corepressors to vitamin D/retinoid X receptor heterodimers.
abstract: Transcriptional regulation by nuclear receptors is mediated by recruitment of coactivators and corepressors. In the classical model, unliganded nonsteroidal receptors bind corepressors, such as the silencing mediator of thyroid and retinoid receptors (SMRT) or nuclear corepressor (NCoR), that are released upon ligand binding. We show here that, unlike other receptors, the heterodimer of the vitamin D receptor (VDR) with the retinoid X receptor (RXR) recruits NCoR and SMRT strictly in a VDR agonist-dependent manner. Binding of an agonist to VDR allows its partner receptor, RXR, to bind the corepressors. The RXR ligand has the opposite effect and induces corepressor release from the heterodimer. 1,25-Dihydroxy-vitamin D(3) (VD3) causes recruitment of SMRT and NCoR to a VDR target promoter. Down-regulation of corepressors by means of small interfering RNA enhances transcriptional responses to VD3. These data reveal a new paradigm of SMRT and NCoR binding to nuclear receptors and demonstrate that these corepressors can function as physiological negative regulators of VD3-mediated transcription.
authors: Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Cieníficas and Universidad Autónoma de Madrid, Madrid, Spain.
authors: Ruth
authors: R
authors: Sánchez-Martínez
authors: Alberto
authors: A
authors: Zambrano
authors: Ana I
authors: AI
authors: Castillo
authors: Ana
authors: A
authors: Aranda
mesh_terms: D002117:Calcitriol / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019281:Dimerization; D005786:Gene Expression Regulation; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; D011401:Promoter Regions, Genetic; D018167:Receptors, Calcitriol / Q000819:agonists / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D047488:Retinoid X Receptors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D004268:DNA-Binding Proteins; C539127:NCOR1 protein, human; C539130:NCOR2 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D056985:Nuclear Receptor Co-Repressor 2; D018167:Receptors, Calcitriol; D012097:Repressor Proteins; D047488:Retinoid X Receptors; D004247:DNA; D002117:Calcitriol