title: GATA- and Smad1-dependent enhancers in the Smad7 gene differentially interpret bone morphogenetic protein concentrations.
abstract: Smad7, an inhibitor of transforming growth factor beta superfamily signaling, is induced by bone morphogenetic protein (BMP) in an inhibitory feedback loop. Here, we identify multiple BMP response elements (BREs) in the Smad7 gene and demonstrate that they function differentially to interpret BMP signals in a cell type-specific manner. Two BREs (BRE-1 and -2) reside in the promoter region. One of these contains several conserved Smad1 and Smad4 binding sites that cooperate to mediate BMP-dependent induction, most likely in the absence of DNA binding partners. The third BRE (I-BRE) resides in the first intron and contains GATA factor binding sites. GATA-1, -5, or -6 is required for strong activation of I-BRE, and we show that they assemble with Smad1 on the I-BRE in living cells. Activation of the I-BRE is mediated by a specific region in GATA-5 and -6 but does not require direct physical interaction with Smad1. Comparison of I-BRE to BRE-1 showed that I-BRE is more responsive to low BMP concentrations. Moreover, analysis by chromatin immunoprecipitation experiments demonstrates that the endogenous I-BRE is occupied more robustly by endogenous Smad1 than is BRE-1. This correlates with regulation of the Smad7 gene, which is induced at lower BMP concentrations in GATA-expressing cell lines compared to non-GATA-expressing lines. These data thus define how cooperative and noncooperative Smad-dependent transcriptional regulation can function to interpret different BMP concentrations.
authors.affiliation: Programme in Molecular Biology and Cancer, Samuel Lunenfeld Research Institute, Room 1075, Mount Sinai Hospital, Toronto, Ontario M5G 1X5, Canada.
authors.forename: Hassina
authors.initials: H
authors.lastname: Benchabane
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Wrana
mesh_terms: D000818:Animals; D001665:Binding Sites; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000378:metabolism* / Q000494:pharmacology; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004742:Enhancer Elements, Genetic; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; D050992:GATA5 Transcription Factor; D050993:GATA6 Transcription Factor; D006801:Humans; D051379:Mice; D017434:Protein Structure, Tertiary; D020218:Response Elements; D051785:Smad Proteins; D051898:Smad1 Protein; D051901:Smad4 Protein; D051906:Smad7 Protein; D015534:Trans-Activators / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta
chemical_list: C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; C494688:GATA1 protein, human; D050992:GATA5 Transcription Factor; C494755:GATA5 protein, human; D050993:GATA6 Transcription Factor; C494759:GATA6 protein, human; C494689:Gata1 protein, mouse; C494756:Gata5 protein, mouse; C494760:Gata6 protein, mouse; C497399:SMAD1 protein, human; C497796:SMAD4 protein, human; C497806:SMAD7 protein, human; D051785:Smad Proteins; D051898:Smad1 Protein; C497401:Smad1 protein, mouse; D051901:Smad4 Protein; C490810:Smad4 protein, mouse; D051906:Smad7 Protein; C497807:Smad7 protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D016212:Transforming Growth Factor beta