Kai Mihoko, Furuya Kanji, Paderi Francesca, Carr Antony M, Wang Teresa S F
Department of Pathology, Stanford University School of Medicine, Stanford, California 94305-5324, USA.
Nat Cell Biol. 2007 Jun;9(6):691-7. doi: 10.1038/ncb1600. Epub 2007 May 21.
When replication forks collapse, Rad3 phosphorylates the checkpoint-clamp protein Rad9 in a manner that depends on Thr 225, a residue within the PCNA-like domain. The physiological function of Thr 225-dependent Rad9 phosphorylation, however, remains elusive. Here, we show that Thr 225-dependent Rad9 phosphorylation by Rad3 regulates DNA repair pathways. A rad9(T225C) mutant induces a translesion synthesis (TLS)-dependent high spontaneous mutation rate and a hyper-recombination phenotype. Consistent with this, Rad9 coprecipitates with the post-replication repair protein Mms2. This interaction is dependent on Rad9 Thr 225 and is enhanced by DNA damage. Genetic analyses indicate that Thr 225-dependent Rad9 phosphorylation prevents inappropriate Rhp51-dependent recombination, potentially by redirecting the repair through a Pli1-mediated sumoylation pathway into the error-free branch of the Rhp6 repair pathway. Our findings reveal a new mechanism by which phosphorylation of Rad9 at Thr 225 regulates the choice of repair pathways for maintaining genomic integrity during the cell cycle.
当复制叉崩溃时，Rad3以一种依赖于苏氨酸225（PCNA样结构域内的一个残基）的方式使检查点钳蛋白Rad9磷酸化。然而，苏氨酸225依赖性Rad9磷酸化的生理功能仍然不清楚。在这里，我们表明Rad3对Rad9的苏氨酸225依赖性磷酸化调节DNA修复途径。rad9（T225C）突变体诱导一种依赖于跨损伤合成（TLS）的高自发突变率和高重组表型。与此一致的是，Rad9与复制后修复蛋白Mms2共沉淀。这种相互作用依赖于Rad9苏氨酸225，并因DNA损伤而增强。遗传分析表明，苏氨酸225依赖性Rad9磷酸化可能通过将修复通过Pli1介导的SUMO化途径重定向到Rhp6修复途径的无错误分支，从而防止不适当的Rhp51依赖性重组。我们的发现揭示了一种新机制，即Rad9在苏氨酸225处的磷酸化在细胞周期中调节修复途径的选择以维持基因组完整性。
