title: Adaptation of a DNA replication checkpoint response depends upon inactivation of Claspin by the Polo-like kinase.
abstract: The checkpoint mediator protein Claspin is essential for the ATR-dependent activation of Chk1 in Xenopus egg extracts containing aphidicolin-induced DNA replication blocks. We show that, during this checkpoint response, Claspin becomes phosphorylated on threonine 906 (T906), which creates a docking site for Plx1, the Xenopus Polo-like kinase. This interaction promotes the phosphorylation of Claspin on a nearby serine (S934) by Plx1. After a prolonged interphase arrest, aphidicolin-treated egg extracts typically undergo adaptation and enter into mitosis despite the presence of incompletely replicated DNA. In this process, Claspin dissociates from chromatin, and Chk1 undergoes inactivation. By contrast, aphidicolin-treated extracts containing mutants of Claspin with alanine substitutions at positions 906 or 934 (T906A or S934A) are unable to undergo adaptation. Under such adaptation-defective conditions, Claspin accumulates on chromatin at high levels, and Chk1 does not decrease in activity. These results indicate that the Plx1-dependent inactivation of Claspin results in termination of a DNA replication checkpoint response.
authors.affiliation: Division of Biology 216-76, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Hae Yong
authors.initials: HY
authors.lastname: Yoo
authors.forename: Akiko
authors.initials: A
authors.lastname: Kumagai
authors.forename: Anna
authors.initials: A
authors.lastname: Shevchenko
authors.forename: Andrej
authors.initials: A
authors.lastname: Shevchenko
authors.forename: William G
authors.initials: WG
authors.lastname: Dunphy
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D004261:DNA Replication / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D010063:Ovum / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014981:Xenopus; D029867:Xenopus Proteins; D000097869:Polo-Like Kinase 1
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016590:Aphidicolin; D064007:Ataxia Telangiectasia Mutated Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D004791:Enzyme Inhibitors; D017346:Protein Serine-Threonine Kinases; D029867:Xenopus Proteins; C416368:CLSPN protein, Xenopus; C576898:Atr protein, Xenopus; C101085:Plk1 protein, Xenopus; D000097869:Polo-Like Kinase 1