Meng, Zheng and Capalbo, Luisa and Glover, David M. and Dunphy, William G. (2011) Role for casein kinase 1 in the phosphorylation of Claspin on critical residues necessary for the activation of Chk1. Molecular Biology of the Cell, 22 (16). pp. 2834-2847. ISSN 1059-1524 http://resolver.caltech.edu/CaltechAUTHORS:20110829-104551403
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The mediator protein Claspin is critical for the activation of the checkpoint kinase Chk1 during checkpoint responses to stalled replication forks. This function involves the Chk1-activating domain (CKAD) of Claspin, which undergoes phosphorylation on multiple conserved sites. These phosphorylations promote binding of Chk1 to Claspin and ensuing activation of Chk1 by ATR. However, despite the importance of this regulatory process, the kinase responsible for these phosphorylations has remained unknown. By using a multifaceted approach, we have found that casein kinase 1 gamma 1 (CK1γ1) carries out this function. CK1γ1 phosphorylates the CKAD of Claspin efficiently in vitro, and depletion of CK1γ1 from human cells by small interfering RNA (siRNA) results in dramatically diminished phosphorylation of Claspin. Consequently, the siRNA-treated cells display impaired activation of Chk1 and resultant checkpoint defects. These results indicate that CK1γ1 is a novel component of checkpoint responses that controls the interaction of a key checkpoint effector kinase with its cognate mediator protein.
|Additional Information:||© 2011 The American Society of Cell Biology. Submitted January 18, 2011. Revised May 3, 2011. Accepted June 7, 2011. This article was published online ahead of print in MBoC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E11-01-0048) on June 16, 2011. We are grateful to laboratory members for helpful advice and comments on the manuscript. We also thank Rochelle Diamond for assistance with flow cytometry and J. Jiang (University of Texas Southwestern Medical School, Dallas, TX) for Drosophila casein kinase expression vectors. This work was supported by National Institutes of Health grants GM-043974 and GM-070891 and an Ellison Senior Scholar in Aging award to W.G.D. Work in the laboratory of D.M.G. was supported by Cancer Research UK and the Biotechnology and Biological Sciences Research Council (United Kingdom).|
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|Deposited By:||Tony Diaz|
|Deposited On:||07 Sep 2011 15:53|
|Last Modified:||26 Dec 2012 13:38|
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