Document Detail


The polymorphic N terminus in human vitamin D receptor isoforms influences transcriptional activity by modulating interaction with transcription factor IIB.
MedLine Citation:
PMID:  10707958     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The human vitamin D receptor (hVDR) is a ligand-regulated transcription factor that mediates the actions of the 1,25-dihydroxyvitamin D3 hormone to effect bone mineral homeostasis. Employing mutational analysis, we characterized Arg-18/Arg-22, hVDR residues immediately N-terminal of the first DNA binding zinc finger, as vital for contact with human basal transcription factor IIB (TFIIB). Alteration of either of these basic amino acids to alanine also compromised hVDR transcriptional activity. In contrast, an artificial hVDR truncation devoid of the first 12 residues displayed both enhanced interaction with TFIIB and transactivation. Similarly, a natural polymorphic variant of hVDR, termed F/M4 (missing a FokI restriction site), which lacks only the first three amino acids (including Glu-2), interacted more efficiently with TFIIB and also possessed elevated transcriptional activity compared with the full-length (f/M1) receptor. It is concluded that the functioning of positively charged Arg-18/Arg-22 as part of an hVDR docking site for TFIIB is influenced by the composition of the adjacent polymorphic N terminus. Increased transactivation by the F/M4 neomorphic hVDR is hypothesized to result from its demonstrated enhanced association with TFIIB. This proposal is supported by the observed conversion of f/M1 hVDR activity to that of F/M4 hVDR, either by overexpression of TFIIB or neutralization of the acidic Glu-2 by replacement with alanine in f/M1 hVDR. Because the f VDR genotype has been associated with lower bone mineral density in diverse populations, one factor contributing to a genetic predisposition to osteoporosis may be the F/f polymorphism that dictates VDR isoforms with differential TFIIB interaction.
Authors:
P W Jurutka; L S Remus; G K Whitfield; P D Thompson; J C Hsieh; H Zitzer; P Tavakkoli; M A Galligan; H T Dang; C A Haussler; M R Haussler
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Molecular endocrinology (Baltimore, Md.)     Volume:  14     ISSN:  0888-8809     ISO Abbreviation:  Mol. Endocrinol.     Publication Date:  2000 Mar 
Date Detail:
Created Date:  2000-04-21     Completed Date:  2000-04-21     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8801431     Medline TA:  Mol Endocrinol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  401-20     Citation Subset:  IM    
Affiliation:
Department of Biochemistry, College of Medicine, University of Arizona, Tuscon 85724, USA.
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MeSH Terms
Descriptor/Qualifier:
Amino Acid Sequence
Amino Acid Substitution
Animals
Bone Density / genetics
COS Cells / drug effects
Calcitriol / pharmacology
Cercopithecus aethiops
DNA / metabolism
Fibroblasts / metabolism
Genetic Predisposition to Disease
Genotype
Humans
Molecular Sequence Data
Mutagenesis, Site-Directed
Osteoporosis / genetics
Polymorphism, Genetic
Protein Isoforms / chemistry,  genetics,  physiology*
Protein Structure, Tertiary
Receptors, Calcitriol / chemistry,  genetics,  physiology*
Transcription Factor TFIIB
Transcription Factors / metabolism*
Transcriptional Activation*
Zinc Fingers / physiology
Grant Support
ID/Acronym/Agency:
AR-15781/AR/NIAMS NIH HHS; DK-33351/DK/NIDDK NIH HHS
Chemical
Reg. No./Substance:
0/Protein Isoforms; 0/Receptors, Calcitriol; 0/Transcription Factor TFIIB; 0/Transcription Factors; 32222-06-3/Calcitriol; 9007-49-2/DNA

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