title: Ligand-triggered stabilization of vitamin D receptor/retinoid X receptor heterodimer conformations on DR4-type response elements.
abstract: Nuclear receptors integrate an incoming signal in the form of a nuclear hormone by undergoing a conformational change that results via co-activator proteins in an activation of the basal transcriptional machinery. The vitamin D(3) receptor is the nuclear receptor for 1alpha,25-dihydroxyvitamin D(3 )(1alpha,25(OH)(2)D(3)) and is known to function as a heterodimer with the retinoid X receptor on DR3-type 1alpha,25(OH)(2)D(3) response elements. Here, it could be demonstrated that DR4-type response elements are at least as effective as DR3-type 1alpha,25(OH)(2)D(3) response elements. Gel shift clipping analysis showed that vitamin D(3) receptor-retinoid X receptor heterodimers form in response to 1alpha, 25(OH)(2)D(3) and retinoid X receptor ligands, the pan-agonist 9-cis retinoic acid (9cRA) and the retinoid X receptor-selective retinoid CD2425, different conformations on the DR4-type element of the rat Pit-1 gene. Interestingly, on this response element the heterodimeric complexes of retinoid X receptor with the thyroid hormone receptor, the retinoic acid receptor and the benzoate ester receptor also displayed characteristic individual ligand-dependent complex formation. On the level of complex formation, utilizing DNA affinity and functional assays, only vitamin D(3) receptor-retinoid X receptor heterodimers showed a synergistic interaction of both ligands. However, the sensitivity of vitamin D(3) receptor-retinoid X receptor heterodimers to 1alpha,25(OH)(2)D(3) was found to be much higher than to retinoid X receptor ligands. Taken together, this study demonstrates a unique interaction potential of vitamin D(3) receptor and retinoid X receptor but also establishes DR4-type response elements as multi-functional DNA binding sites with a potential to integrate various hormone signalling pathways.
authors.affiliation: Institut für Physiologische Chemie I and Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, Düsseldorf, D-40001, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Quack
authors.forename: C
authors.initials: C
authors.lastname: Carlberg
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000819:agonists / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D004357:Drug Synergism; D006801:Humans; D008024:Ligands; D011487:Protein Conformation; D051381:Rats; D018167:Receptors, Calcitriol / Q000819:agonists / Q000737:chemistry* / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000819:agonists / Q000737:chemistry* / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000819:agonists / Q000737:chemistry / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D047488:Retinoid X Receptors; D017384:Sequence Deletion / Q000235:genetics; D013379:Substrate Specificity; D013816:Thermodynamics; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000819:agonists / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D008024:Ligands; C494187:POU1F1 protein, human; C494186:Pou1f1 protein, rat; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D047488:Retinoid X Receptors; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; D004247:DNA