Kumagai, Akiko and Guo, Zijian and Emami, Katayoon H. and Wang, Sophie X. and Dunphy, William G. (1998) The Xenopus Chk1 Protein Kinase Mediates a Caffeine-sensitive Pathway of Checkpoint Control in Cell-free Extracts. Journal of Cell Biology, 142 (6). pp. 1559-1569. ISSN 0021-9525 http://resolver.caltech.edu/CaltechAUTHORS:20090918-130239167
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We have analyzed the role of the protein kinase Chk1 in checkpoint control by using cell-free extracts from Xenopus eggs. Recombinant Xenopus Chk1 (Xchk1) phosphorylates the mitotic inducer Cdc25 in vitro on multiple sites including Ser-287. The Xchk1-catalyzed phosphorylation of Cdc25 on Ser-287 is sufficient to confer the binding of 14-3-3 proteins. Egg extracts from which Xchk1 has been removed by immunodepletion are strongly but not totally compromised in their ability to undergo a cell cycle delay in response to the presence of unreplicated DNA. Cdc25 in Xchk1-depleted extracts remains bound to 14-3-3 due to the action of a distinct Ser-287-specific kinase in addition to Xchk1. Xchk1 is highly phosphorylated in the presence of unreplicated or damaged DNA, and this phosphorylation is abolished by caffeine, an agent which attenuates checkpoint control. The checkpoint response to unreplicated DNA in this system involves both caffeine-sensitive and caffeine-insensitive steps. Our results indicate that caffeine disrupts the checkpoint pathway containing Xchk1.
|Additional Information:||RUP grants the public the nonexclusive right to copy, distribute, or display the Work under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/ and http://creativecommons.org/licenses/by-nc-sa/3.0/legalcode. Received for publication 15 May 1998 and in revised form 7 July 1998. We are very grateful to W. Sullivan (University of California, Santa Cruz, CA) for providing the sequence of Drosophila Grapes. We thank our colleagues for comments on the manuscript. This work was supported by a grant from the National Institutes of Health (GM-43974) and a postdoctoral fellowship from the Damon Runyon-Walter Winchell Cancer Research Fund to S.X. Wang. W.G. Dunphy is an investigator of the Howard Hughes Medical Institute.|
|Subject Keywords:||Cdc2; Chk1; 14-3-3 proteins; Cdc25; caffeine|
|Official Citation:||Akiko Kumagai, Zijian Guo, Katayoon H. Emami, Sophie X. Wang, and William G. Dunphy The Xenopus Chk1 Protein Kinase Mediates a Caffeine-sensitive Pathway of Checkpoint Control in Cell-free Extracts J. Cell Biol., Sep 1998; 142: 1559 - 1569.|
|Usage Policy:||RUP grants the public the nonexclusive right to copy, distribute, or display the Work under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/ and http://creativecommons.org/licenses/by-nc-sa/3.0/legalcode.|
|Deposited By:||George Porter|
|Deposited On:||05 Oct 2009 16:27|
|Last Modified:||26 Dec 2012 11:24|
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