Variations in vitamin D receptor transcription factor complexes associated with the osteocalcin gene vitamin D responsive element in osteoblasts and osteosarcoma cells

A. R. Shakoori, A. J. van Wijnen, R. Bortell, T. A. Owen, J. L. Stein, J. B. Lian, G. S. Stein

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

Vitamin D responsive transcription of the bone‐specific osteocalcin gene differs markedly in osteosarcoma cells and normal diploid osteoblasts. In osteoblasts the osteocalcin gene is transcribed, and upregulated by Vitamin D, only in post‐proliferative cells, but in osteosarcoma cells expression is constitutive. This distinction in transcriptional regulation of the osteocalcin gene correlates with striking differences in the relative representation of two principal Vitamin D‐dependent protein/DNA complexes designated V1 and V2 at the Vitamin D responsive element in the osteocalcin promoter. Formation of both complexes is Vitamin D dependent and they contain the Vitamin D receptor as well as an RXR related protein. Pore size exclusion and sedimentation velocity analyses suggest that the V1 and V2 complexes represent oligomeric protein assemblies (respectively, tetramers and trimers), and reflect primarily DNA‐directed association of the monomeric protein components at the osteocalcin Vitamin D responsive element. UV crosslinking and methylation interference analyses of the V1 and V2 complexes at the osteocalcin Vitamin D responsive element indicate differences in protein/DNA recognition. For example, the V1 complex interacts with both steroid half‐elements, whereas the V2 complex appears to recognize the proximal half‐element. Our findings suggest variations in protein/protein and protein/DNA interactions of the VDR and RXR related complexes V1 and V2 at the osteocalcin Vitamin D responsive element that reflect unique properties of the osteosarcoma and normal diploid osteoblast phenotype. © 1994 Wiley‐Liss, Inc.

Original languageEnglish (US)
Pages (from-to)218-229
Number of pages12
JournalJournal of cellular biochemistry
Volume55
Issue number2
DOIs
StatePublished - Jun 1994

Keywords

  • osteoblasts
  • osteocalcin gene
  • osteosarcoma cells
  • transcription factor complexes
  • vitamin D response element (VDRE)

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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