title: BMP signaling is responsible for serum-induced Id2 expression.
abstract: Ids function as negative regulators of basic helix-loop-helix transcription factors and their expression is rapidly induced by serum stimulation in various cell types. In this study, we investigated the molecular basis of serum-induced expression of the mouse Id2 gene in NIH3T3 cells. A small-molecule inhibitor of bone morphogenetic protein (BMP) type I receptor kinases blocked the serum induction of Id2 mRNA. The chemical compound and several inhibitory proteins specific for BMP signaling suppressed the serum-induced activation of the luciferase construct with the mouse Id2 4.6-kb promoter region. Importantly, serum stimulation evoked rapid phosphorylation of Smad1/5/8 and significant activation of the reporter plasmid containing the recently identified BMP-responsive element (BRE) of the mouse Id2. Mutation analysis demonstrated that the binding sites for Smad proteins in the Id2 BRE were critical for serum response of the 4.6-kb whole construct. Gel shift and chromatin immunoprecipitation (ChIP) assays confirmed the serum-inducible binding of Smad1/5/8 and Smad4 to the Id2 BRE in vitro and in vivo. Finally, a knockdown experiment revealed the functional importance of Smad1 in the serum induction of Id2 expression. Thus, we concluded that BMP signaling is primarily responsible for the serum-induced Id2 expression. Our results also suggest that some of the cellular effects caused by serum are mediated through BMP signaling.
authors.affiliation: Division of Molecular Genetics, Department of Biochemistry and Bioinformative Sciences, School of Medicine, Faculty of Medical Sciences, University of Fukui, Fukui, Japan. hkurooka@u-fukui.ac.jp
authors.forename: Hisanori
authors.initials: H
authors.lastname: Kurooka
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakahiro
authors.forename: Kentaro
authors.initials: K
authors.lastname: Mori
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sano
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Yokota
mesh_terms: D000818:Animals; D001483:Base Sequence; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D051797:Inhibitor of Differentiation Protein 2 / Q000037:antagonists & inhibitors / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D011720:Pyrazoles / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D044967:Serum / Q000378:metabolism; D027602:Serum Response Element; D051785:Smad Proteins / Q000097:blood / Q000235:genetics / Q000378:metabolism
chemical_list: D019485:Bone Morphogenetic Proteins; C497452:Idb2 protein, mouse; D051797:Inhibitor of Differentiation Protein 2; D011720:Pyrazoles; D011743:Pyrimidines; D051785:Smad Proteins; C516138:dorsomorphin; D052005:Bone Morphogenetic Protein Receptors, Type I