Furumatsu, Takayuki Department of Orthopaedic Surgery, Science of Functional Recovery and Reconstruction, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences
Shukunami, Chisa Department of Cellular Differentiation, Institute for Frontier Medical Sciences, Kyoto University
Amemiya-Kudo, Michiyo Okinaka Memorial Institute for Medical Research, Toranomon Hospital
Shimano, Hitoshi Department of Internal Medicine, Endocrinology and Metabolism, Advanced Biomedical Applications, Graduate School of Comprehensive Human Sciences Center for Tsukuba Advanced Research Alliance, University of Tsukuba
Ozaki, Toshifumi Department of Orthopaedic Surgery, Science of Functional Recovery and Reconstruction, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences
During musculoskeletal development, Sry-type HMG box 9 (Sox9) has a crucial role in mesenchymal condensation and chondrogenesis. On the other hand, a tissue-specific basic helix-loop-helix (bHLH) transcription factor Scleraxis (Scx) regulates the differentiation of tendon and ligament progenitors. Whereas these two transcription factors cooperatively participate in the determination of cellular lineages, the precise interaction between Sox9 and Scx remains unclear. We have previously demonstrated that the Sox9-dependent transcription is synergistically activated by several Sox9-associating molecules, such as p300 and Smad3, on chromatin. In this study, we investigated the function of Scx in the Sox9-dependent transcription. The expression of α1(II) collagen (Col2a1) gene was stimulated by an appropriate transduction of Sox9 and Scx. Scx and its partner E47, which dimerizes with other bHLH proteins, cooperatively enhanced the Sox9-dependent transcription in luciferase reporter assays. Coactivator p300 synergistically increased the activity of Sox9-regulated reporter gene, which contains promoter and enhancer regions of Col2a1, in the presence of Scx and E47. Immunoprecipitation analyses revealed that Scx and E47 formed a transcriptional complex with Sox9 and p300. Scx/E47 heterodimer also associated with a conserved E-box sequence (CAGGTG) in the Col2a1 promoter on chromatin. These findings suggest that Scx and E47 might modulate the primary chondrogenesis by associating with the Sox9-related transcriptional complex, and by binding to the conserved E-box on Col2a1 promoter.
The International Journal of Biochemistry & Cell Biology
Pergamon-Elsevier Science Ltd.
© 2009 Elsevier Ltd. All rights reserved.
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