Additional protein factors play a role in the formation of VDR/RXR complexes on vitamin D response elements.
The vitamin D receptor (VDR) elicits a transcriptional response to 1,25-dihydroxyvitamin D3 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.
Zierold
C
C
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706, USA.
DeLuca
H F
HF
D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D047488:Retinoid X Receptors; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism; D035581:Transcription Factor TFIIB; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014807:Vitamin D / Q000378:metabolism* / Q000494:pharmacology; D065668:Vitamin D3 24-Hydroxylase
D011506:Proteins; D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D035581:Transcription Factor TFIIB; D014157:Transcription Factors; D014807:Vitamin D; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase