Nucleic Acids Research Advance Access published online on August 12, 2008
Nucleic Acids Research, doi:10.1093/nar/gkn503
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Genome integrity, repair and replication |
Dissecting the role of p53 phosphorylation in homologous recombination provides new clues for gain-of-function mutants
1Department of Obstetrics and Gynecology, University of Ulm, 89075 Ulm, 2Institute for Genetics, University of Bonn, 53113 Bonn and 3Department of Medicine, Hematology/Oncology, University of Münster, 48129 Münster, Germany
*To whom correspondence should be addressed. Tel: +49 731 500 58800; Fax: +49 731 500 58810; Email: lisa.wiesmueller{at}uni-ulm.de
Received June 19, 2008. Revised July 21, 2008. Accepted July 21, 2008.
Regulation of homologous recombination (HR) represents the best-characterized DNA repair function of p53. The role of p53 phosphorylation in DNA repair is largely unknown. Here, we show that wild-type p53 repressed repair of DNA double-strand breaks (DSBs) by HR in a manner partially requiring the ATM/ATR phosphorylation site, serine 15. Cdk-mediated phosphorylation of serine 315 was dispensable for this anti-recombinogenic effect. However, without targeted cleavage of the HR substrate, serine 315 phosphorylation was necessary for the activation of topoisomerase I-dependent HR by p53. Moreover, overexpression of cyclin A1, which mimics the situation in tumors, inappropriately stimulated DSB-induced HR in the presence of oncogenic p53 mutants (not Wtp53). This effect required cyclin A1/cdk-mediated phosphorylation for stable complex formation with topoisomerase I. We conclude that p53 mutants have lost the balance between activation and repression of HR, which results in a net increase of potentially mutagenic DNA rearrangements. Our data provide new insight into the mechanism underlying gain-of-function of mutant p53 in genomic instability.
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