Abstract
Background:
Bone morphogenetic protein-2 (BMP-2) stimulates osteoblast differentiation, but inhibits myogenic differentiation in C2C12 myoblasts. BMP-2 induces transcription of Id1, an inhibitor for myogenesis, within 1 h in the cells. To examine the molecular mechanism of the action of BMP-2, we analysed a BMP-2-responsive element (BRE) in the 5' flanking region of the human Id1 gene.
Results:
A GC-rich region between -985 bp and -957 bp of the human Id1 gene was identified as a BRE. The BRE containing promoter activity was stimulated by BMP-2 or by constitutively active BMP receptors (BMPR-IA and BMPR-IB). The stimulation was blocked by co-transfecting with dominant negative BMPR-IA or Smad7. A unique DNA-protein complex was induced in response to BMP-2 on the BRE. The complex induced by BMP-2 contained Smad1 and Smad4, possibly as a complex of both Smads. BMP-2 failed to stimulate the expression of Id1 mRNA in Smad4-deficient cells. Over-expression of Smad4, but not Smad1, stimulated the Id1 reporter activity and the expression of endogenous Id1 mRNA in Smad4-deficient cells.
Conclusion:
Signalling of BMP-2 to stimulate the expression of Id1 would be transduced by BMPR-IA and mediated by Smad1 and Smad4, both of which form a complex on the 29 bp GC-rich element.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Protein Receptors, Type I
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Bone Morphogenetic Proteins / metabolism*
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Cell Line
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DNA-Binding Proteins / metabolism
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Enzyme Inhibitors / metabolism
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Genes, Reporter
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Helix-Loop-Helix Motifs
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Humans
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Inhibitor of Differentiation Protein 1
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Mice
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Phosphoinositide-3 Kinase Inhibitors
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Promoter Regions, Genetic
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Protein Binding
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Receptors, Growth Factor / genetics
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Receptors, Growth Factor / metabolism
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Repressor Proteins*
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Response Elements / genetics*
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Signal Transduction / physiology*
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Smad Proteins
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Smad1 Protein
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Smad4 Protein
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Trans-Activators / metabolism
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Transcription Factors / genetics*
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Transcription Factors / metabolism
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Transforming Growth Factor beta*
Substances
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BMP2 protein, human
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Bmp2 protein, mouse
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Bone Morphogenetic Protein 2
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Bone Morphogenetic Proteins
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DNA-Binding Proteins
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Enzyme Inhibitors
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ID1 protein, human
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Idb1 protein, mouse
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Inhibitor of Differentiation Protein 1
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Phosphoinositide-3 Kinase Inhibitors
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Receptors, Growth Factor
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Repressor Proteins
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SMAD1 protein, human
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SMAD4 protein, human
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Smad Proteins
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Smad1 Protein
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Smad1 protein, mouse
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Smad4 Protein
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Smad4 protein, mouse
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Trans-Activators
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Transcription Factors
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Transforming Growth Factor beta
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Protein Serine-Threonine Kinases
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Mitogen-Activated Protein Kinases
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BMPR1A protein, human
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BMPR1B protein, human
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Bmpr1a protein, mouse
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Bmpr1b protein, mouse
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Bone Morphogenetic Protein Receptors, Type I