@article{711d4fdaa9bb417b8a8de15432c38016,
title = "Cyclin-dependent kinases regulate the antiproliferative function of Smads",
abstract = "Transforming growth factor-β (TGF-β) potently inhibits cell cycle progression at the G1 phase. Smad3 has a key function in mediating the TGF-β growth-inhibitory response. Here we show that Smad3 is a major physiological substrate of the G1 cyclin-dependent kinases CDK4 and CDK2. Except for the retinoblastoma protein family, Smad3 is the only CDK4 substrate demonstrated so far. We have mapped CDK4 and CDK2 phosphorylation sites to Thr 8, Thr 178 and Ser 212 in Smad3. Mutation of the CDK phosphorylation sites increases Smad3 transcriptional activity, leading to higher expression of the CDK inhibitor p15. Mutation of the CDK phosphorylation sites of Smad3 also increases its ability to downregulate the expression of c-myc. Using Smad3 -/- mouse embryonic fibroblasts and other epithelial cell lines, we further show that Smad3 inhibits cell cycle progression from G1 to S phase and that mutation of the CDK phosphorylation sites in Smad3 increases this ability. Taken together, these findings indicate that CDK phosphorylation of Smad3 inhibits its transcriptional activity and antiproliferative function. Because cancer cells often contain high levels of CDK activity, diminishing Smad3 activity by CDK phosphorylation may contribute to tumorigenesis and TGF-β resistance in cancers.",
author = "Isao Matsuura and Denissova, {Natalia G.} and Guannan Wang and Dongming He and Jianyin Long and Fang Liu",
note = "Funding Information: Acknowledgements We are very grateful to X.-F. Wang for Smad3 mutant mice; E. P. Reddy, R. V. Mettus and H. Kiyokawa for CDK4 mutant mice; J. Massagu{\'e} for reagents and continued support; C.-X. Deng for reagents and communications before publication; M. M. Shen and members of his laboratory for assistance with mouse work; C. Abate-Shen, M. Cobb, X.-F. Feng, J. Germino, G. J. Hannon, S.-J. Kim, M. Kretzschmar, H. Lee, M.-H. Lee, E. Lees, X. Liu, H. L. Moses, G. Nolan, A. Rabson, D. Reinberg, M. Reiss, Y. Shi, N. Walworth and W. Xie for reagents and/or suggestions; and numerous colleagues for discussions. This work was supported by the 1999 American Association for Cancer Research–National Foundation for Cancer Research Career Development Award, a Burroughs Wellcome Fund New Investigator Award, a Kimmel Scholar Award from the Sidney Kimmel Foundation for Cancer Research, the Emerald Foundation, the New Jersey Commission on Cancer Research, and the NIH (to F.L.). Funding Information: Acknowledgements Part of this work was performed at the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland. We thank C. Schulze-Briese and the staff of beamline X06SA for help; L. Jacquamet and J. McCarthy for help during data collection at the European Synchrotron Radiation Facility, Grenoble, France; G. Arnold for peptide synthesis; and K. Str{\"a}ber and members of the Cramer laboratory for careful reading of the manuscript. P.C. is supported by the Deutsche Forschungsgemeinschaft, the EMBO Young Investigator Programme and the Fonds der Chemischen Industrie. A.M. is supported by an EMBO long-term fellowship.",
year = "2004",
month = jul,
day = "8",
doi = "10.1038/nature02650",
language = "English (US)",
volume = "430",
pages = "226--231",
journal = "Nature",
issn = "0028-0836",
publisher = "Nature Publishing Group",
number = "6996",
}