HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 283, Issue 28, 19322-19328, July 11, 2008

This Article Full Text Full Text (PDF) All Versions of this Article: 283/28/19322    most recent M802474200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Jin, J. Articles by Harper, J. W. PubMed PubMed Citation Articles by Jin, J. Articles by Harper, J. W. Social Bookmarking                      What's this?

Differential Roles for Checkpoint Kinases in DNA Damage-dependent Degradation of the Cdc25A Protein Phosphatase^*

Jianping Jin¹, Xiaolu L. Ang², Xin Ye, Mark Livingstone³, and J. Wade Harper⁴

From the Department of Pathology, Harvard Medical School, Boston Massachusetts 02115 and Cell Signaling Technology, Danvers, Massachusetts 01923

In response to DNA damage, cells activate a signaling pathway that promotes cell cycle arrest and degradation of the cell cycle regulator Cdc25A. Cdc25A degradation occurs via the SCF^β-TRCP pathway and phosphorylation of Ser-76. Previous work indicates that the checkpoint kinase Checkpoint kinase 1 (Chk1) is capable of phosphorylating Ser-76 in Cdc25A, thereby promoting its degradation. In contrast, other experiments involving overexpression of dominant Chk2 mutant proteins point to a role for Chk2 in Cdc25A degradation. However, loss-of-function studies that implicate Chk2 in Cdc25A turnover are lacking, and there is no evidence that Chk2 is capable of phosphorylating Ser-76 in Cdc25A despite the finding that Chk1 and Chk2 sometimes share overlapping primary specificity. We find that although Chk2 can phosphorylate many of the same sites in Cdc25A that Chk1 phosphorylates, albeit with reduced efficiency, Chk2 is unable to efficiently phosphorylate Ser-76. Consistent with this, Chk2, unlike Chk1, is unable to support SCF^β-TRCP-mediated ubiquitination of Cdc25A in vitro. In CHK2^–/– HCT116 cells, the kinetics of Cdc25A degradation in response to ionizing radiation is comparable with that seen in HCT116 cells containing Chk2, indicating that Chk2 is not generally required for timely DNA damage-dependent Cdc25A turnover. In contrast, depletion of Chk1 by RNA interference in CHK2^–/– cells leads to Cdc25A stabilization in response to ionizing radiation. These data support the idea that Chk1 is the primary signal transducer linking activation of the ATM/ATR kinases to Cdc25A destruction in response to ionizing radiation.

Received for publication, March 31, 2008 , and in revised form, May 13, 2008.

^* This work was supported, in whole or in part, by National Institutes of Health Grants GM054137 and AG011085 (to J. W. H.). 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.

¹ Current address: Dept. of Biochemistry and Molecular Biology, University of Texas Health Science Center, Houston, Texas 77030.

² Supported by a predoctoral fellowship from the National Institutes of Health.

³ Current address: Dept. of Biochemistry, McGill University, Montreal, Quebec H3A 2T5, Canada.

⁴ To whom correspondence should be addressed: 77 Ave Louis Pasteur, NRB Rm. 940, Boston, MA 02115. Fax: 617-432-6591; E-mail: wade_harper{at}hms.harvard.edu.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?