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The Rad9-Hus1-Rad1 Checkpoint Clamp Regulates Interaction of TopBP1 with ATR

Lee, Joon and Kumagai, Akiko and Dunphy, William G. (2007) The Rad9-Hus1-Rad1 Checkpoint Clamp Regulates Interaction of TopBP1 with ATR. Journal of Biological Chemistry, 282 (38). pp. 28036-28044. ISSN 0021-9258. doi:10.1074/jbc.M704635200.

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TopBP1 serves as an activator of the ATR-ATRIP complex in response to the presence of incompletely replicated or damaged DNA. This process involves binding of ATR to the ATR-activating domain of TopBP1, which is located between BRCT domains VI and VII. TopBP1 displays increased binding to ATR-ATRIP in Xenopus egg extracts containing checkpoint-inducing DNA templates. We show that an N-terminal region of TopBP1 containing BRCT repeats I-II is essential for this checkpoint-stimulated binding of TopBP1 to ATR-ATRIP. The BRCT I-II region of TopBP1 also binds specifically to the Rad9-Hus1-Rad1 (9-1-1) complex in Xenopus egg extracts. This binding occurs via the C-terminal domain of Rad9 and depends upon phosphorylation of its Ser-373 residue. Egg extracts containing either a mutant of TopBP1 lacking the BRCT I-II repeats or a mutant of Rad9 with an alanine substitution at Ser-373 are defective in checkpoint regulation. Furthermore, an isolated C-terminal fragment from Rad9 is an effective inhibitor of checkpoint signaling in egg extracts. These findings suggest that interaction of the 9-1-1 complex with the BRCT I-II region of TopBP1 is necessary for binding of ATR-ATRIP to the ATR-activating domain of TopBP1 and the ensuing activation of ATR.

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Kumagai, Akiko0000-0003-2422-8053
Dunphy, William G.0000-0001-7598-8939
Additional Information:© 2007 the American Society for Biochemistry and Molecular Biology. Received for publication, June 5, 2007 , and in revised form, July 17, 2007. Originally published In Press as doi:10.1074/jbc.M704635200 on July 18, 2007. We thank Howard Lindsay (University of Lancaster, United Kingdom) for providing antisera against Xrad1 and Xrad9 and a clone encoding Xrad9 and Karlene Cimprich (Stanford University) for providing the baculovirus constructs for the wild-type recombinant 9-1-1 complex. We are grateful to Larry Karnitz (Mayo Clinic) for sharing information. This work was supported by Grants GM070891 and GM043974 from the National Institutes of Health (to W.G.D.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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Issue or Number:38
Record Number:CaltechAUTHORS:LEEjbc07
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ID Code:8845
Deposited By: Archive Administrator
Deposited On:20 Sep 2007
Last Modified:08 Nov 2021 20:53

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