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Identification of the GATA factor TRPS1 as a repressor of the osteocalcin promoter

Denise M Piscopo1, Eric B Johansen, Rik Derynck

  • 1Department of Cell and Tissue Biology, Programs in Cell Biology and Developmental Biology, University of California, San Francisco, California 94143, USA.

The Journal of Biological Chemistry
|September 18, 2009
PubMed

Insights

The transcription factor TRPS1 binds the osteocalcin promoter, regulating osteocalcin gene expression and bone matrix formation. This identifies a novel role for TRPS1 in osteoblast differentiation.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • TRPS1 is a known repressor of chondrocyte differentiation and its mutations cause tricho-rhino-phalangeal syndrome with skeletal abnormalities.
  • TRPS1 binds GATA consensus sequences in regulatory promoter regions.
  • Osteocalcin is a key marker of bone formation and osteoblast differentiation.

Purpose of the Study:

  • To investigate the role of TRPS1 in osteocalcin gene regulation and osteoblast differentiation.
  • To determine if TRPS1 directly binds the osteocalcin promoter.

Main Methods:

  • Proteomic analysis to identify proteins binding the osteocalcin promoter OSE2 sequence.
  • Electrophoretic mobility shift assays (EMSAs) to confirm TRPS1 binding to the osteocalcin promoter.
  • Mutation analysis of the GATA binding site in the osteocalcin promoter.
  • Quantitative analysis of TRPS1 and osteocalcin expression during osteoblast differentiation.
  • Assessment of mineralized bone matrix formation.

Main Results:

  • TRPS1 was identified as a protein bound to the osteocalcin promoter.
  • TRPS1 directly binds the osteocalcin promoter via a conserved GATA binding sequence, independent of Runx2.
  • TRPS1 expression is detected in osteosarcoma cells and during osteoblast differentiation of bone marrow stromal cells.
  • TRPS1 regulates osteocalcin expression and modulates mineralized bone matrix formation in differentiating osteoblasts.

Conclusions:

  • TRPS1 directly regulates osteocalcin transcription through a GATA binding site in the promoter.
  • TRPS1 plays a significant role in osteoblast differentiation and bone matrix formation.
  • These findings reveal a novel function for TRPS1 in osteogenesis, expanding on its known role in chondrogenesis.

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