All natural DR3-type vitamin D response elements show a similar functionality in vitro.
The vitamin D(3) receptor (VDR), which is the nuclear receptor for 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)], acts primarily as a heterodimer with the retinoid X receptor (RXR) and binds preferentially to directly repeated arrangements of two hexameric binding sites with three spacing nucleotides [DR3-type vitamin D response elements (VDREs)]. In this study, all presently known natural DR3-type VDREs have been compared and classified on the basis of their complex-formation with VDR-RXR heterodimers and their ability to stabilize VDR-RXR heterodimer conformations. Based on the affinity of each VDRE for VDR-RXR heterodimers, the DR3-type VDREs were divided into three classes. The ligand sensitivity of this complex-formation and conformational stabilization was determined to be in the range of 0.1 nM. No significant differences in the 1alpha,25(OH)(2)D(3)-modulated interactions of the DR3-type VDRE-complexed VDR-RXR heterodimer with the co-activator SRC-1 (steroid receptor co-activator-1) or the co-repressor NCoR (nuclear receptor co-repressor) were found. Taken together, the affinity for VDR-RXR heterodimers appears to be the major discriminating parameter between natural DR3-type VDREs. This will not only facilitate further investigation of the principles of DR3-type-VDRE-mediated gene regulation, but also strongly suggests that DR3-type VDREs alone cannot explain the pleiotropic genomic action of 1alpha,25(OH)(2)D(3).
Toell
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A
Institut für Physiologische Chemie I and Biomedizinisches Forschungszentrum, Heinrich-Heine-Universität, Postfach 10 10 07, D-40001 Düsseldorf, Germany.
Polly
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P
Carlberg
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C
D001483:Base Sequence; D019281:Dimerization; D006801:Humans; D018167:Receptors, Calcitriol / Q000378:metabolism*; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D047488:Retinoid X Receptors; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism
D018167:Receptors, Calcitriol; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D014157:Transcription Factors