Mutations in the 1,25-dihydroxyvitamin D3 receptor identifying C- terminal amino acids required for transcriptional activation that are functionally dissociated from hormone binding, heterodimeric DNA binding, and interaction with basal transcription factor IIB, in vitro

Peter W. Jurutka, Jui Cheng Hsieh, Lenore S. Remus, G. Kerr Whitfield, Paul D. Thompson, Carol A. Haussler, Jorge C.G. Blanco, Keiko Ozato, Mark R. Haussler

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To investigate a potential ligand-dependent transcriptional activation domain (AF-2) in the C-terminal region of the human vitamin D receptor (hVDR), two conserved residues, Leu-417 and Glu-420, were replaced with alanines by site-directed mutagenesis (L417A and E420A). Transcriptional activation in response to 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) was virtually eliminated when either point mutant was transfected into several mammalian cell lines. Furthermore, both mutants exhibited a dominant negative phenotype when expressed in COS-7 cells. Scatchard analysis at 4 °C and a ligand-dependent DNA binding assay at 25 °C revealed essentially normal 1,25-(OH)2D3 binding for the mutant hVDRs, which were also equivalent to native receptor in associating with the rat osteocalcin vitamin D responsive element as a presumed heterodimer with retinoid X receptor. Glutathione S- transferase-human transcription factor IIB (TFIIB) fusion protein linked to Sepharose equally coprecipitated the wild-type hVDR and the AF-2 mutants. These data implicate amino acids Leu-417 and Glu-420, residing in a putative α-helical region at the extreme C terminus of hVDR, as critical in the mechanism of 1,25-(OH)2D3-stimulated transcription, likely mediating an interaction with a coactivator(s) or a component of the basal transcriptional machinery distinct from TFIIB.

Original languageEnglish (US)
Pages (from-to)14592-14599
Number of pages8
JournalJournal of Biological Chemistry
Issue number23
StatePublished - Jun 6 1997


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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