Characterization of Transcriptional Activation and DNA-Binding Functions in the Hinge Region of the Vitamin D Receptor

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• 作者：Paul L. Shaffer ; Donald P. McDonnell ; and Daniel T. Gewirth
• 刊名：Biochemistry
• 出版年：2005
• 出版时间：February 22, 2005
• 年：2005
• 卷：44
• 期：7
• 页码：2678 - 2685
• 全文大小：456K
• 年卷期：v.44,no.7(February 22, 2005)
• ISSN：1520-4995

文摘

The vitamin D receptor (VDR) is a ligand-responsive transcription factor that forms active,heterodimeric complexes with the 9-cis retinoic acid receptor (RXR) on vitamin D response elements(VDREs). Both proteins consist of an N-terminal DNA-binding domain, a C-terminal ligand-bindingdomain, and an intervening hinge region. The length requirements of the hinge for both transcriptionalregulation and DNA binding have not been studied to date for any member of the steroid hormonesuperfamily. We have generated a series of internal deletion mutants of the VDR hinge and found thatdeletion of as few as five amino acids from the C-terminus of the hinge significantly reduces transcriptionalactivation in vivo. Replacing deleted residues in the C-terminus of the hinge with alanines restored activity,indicating that this section of the hinge acts as a sequence-independent spacer. The hinge region of VDRforms a long helix, and the geometric consequences of this structure may explain the requirement of thehinge region for transcriptional activity. Interestingly, all of the deletion mutants, even those that do notactivate transcription, bind VDREs with equal and high affinity, indicating that the defect in these mutantsis not their ability to bind VDREs. In contrast to VDR, constructs of RXR containing deletions of up to14 amino acids in the hinge region exhibit near wild-type transcriptional activity. The ability to deletemore of the RXR hinge may be related to the additional plasticity required by its role as the commonheterodimer partner for nuclear receptors on differing DNA elements.