Additional protein factors play a role in the formation of VDR/RXR complexes on vitamin D response elements
✍ Scribed by Claudia Zierold; H. F. DeLuca
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 200 KB
- Volume
- 71
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
The vitamin D receptor (VDR) elicits a transcriptional response to 1,25-dihydroxyvitamin D 3 by binding to specific response elements (VDRE) in the promoter of target genes. Retinoic X receptor (RXR) is required for formation of the VDR-VDRE complex when VDR is supplied at physiologic concentrations. When porcine intestinal nuclear extract is used as a source of VDR, two distinct complexes are always observed with native gel electrophoresis. Both complexes contain VDR and RXR. We now show that the faster-migrating complex requires another heretofore unknown nuclear factor for its formation. In addition, we provide evidence that the formation of the slower-migrating complex is enhanced by transcription factor IIB (TFIIB). Using ligand binding assays, we determined that both complexes contain the same ratio of VDR to VDRE. Using RXR subtype-specific antibodies in gel shift assays, we show that the complexes contain more than one RXR subtype. Therefore, the present results demonstrate VDR-RXR-VDRE complexes formed with pig intestinal nuclear extracts contain other proteins and that the complexes formed between VDR and VDRE are not simply heterodimers of VDR and RXR.