title: A Smad3 and TTF-1/NKX2-1 complex regulates Smad4-independent gene expression.
abstract: Thyroid transcription factor-1 (TTF-1, also known as NKX2-1) is a tissue-specific transcription factor in lung epithelial cells. Although TTF-1 inhibits the epithelial-to-mesenchymal transition induced by transforming growth factor-β (TGF-β) in lung adenocarcinoma cells, the mechanism through which TTF-1 inhibits the functions of TGF-β is unknown. Here we show that TTF-1 disrupts the nuclear Smad3-Smad4 complex without affecting the nuclear localization of phospho-Smad3. Genome-wide analysis by chromatin immunoprecipitation followed by sequencing revealed that TTF-1 colocalizes with Smad3 on chromatin and alters Smad3-binding patterns throughout the genome, while TTF-1 generally inhibits Smad4 binding to chromatin. Moreover, Smad3 binds to chromatin together with TTF-1, but not with Smad4, at some Smad3-binding regions when TGF-β signaling is absent, and knockdown of Smad4 expression does not attenuate Smad3 binding in these regions. Thus, TTF-1 may compete with Smad4 for interaction with Smad3, and in the presence of TTF-1, Smad3 regulates the transcription of certain genes independently of Smad4. These findings provide a new model of regulation of TGF-β-Smad signaling by TTF-1.
authors: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Kazunobu
authors: K
authors: Isogaya
authors: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Daizo
authors: D
authors: Koinuma
authors: Genome Science Division, Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku 153-8904, Japan.
authors: Shuichi
authors: S
authors: Tsutsumi
authors: 1] Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan [2] Department of Respiratory Medicine, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Roy-Akira
authors: RA
authors: Saito
authors: 1] Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan [2] Department of Biochemistry, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan.
authors: Keiji
authors: K
authors: Miyazawa
authors: Genome Science Division, Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Meguro-ku 153-8904, Japan.
authors: Hiroyuki
authors: H
authors: Aburatani
authors: Department of Molecular Pathology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Kohei
authors: K
authors: Miyazono
mesh_terms: D045744:Cell Line, Tumor; D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051900:Smad3 Protein / Q000378:metabolism*; D051901:Smad4 Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D034741:RNA, Small Interfering; D051900:Smad3 Protein; D051901:Smad4 Protein; C504003:TTF1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta