Regulation of the ATR Checkpoint Kinase by DNA Damage

 描述（由申请人提供）：基因组不稳定性是癌症的标志。基因组稳定性的维持依赖于许多细胞过程的协同作用，如DNA复制、DNA修复和细胞周期转换。这些细胞过程的中心协调者是DNA损伤信号通路，通常被称为检查点。在人类细胞中，检查点由两种主要激酶ATM和ATR协调。虽然ATM对DNA双链断裂（DSB）的反应至关重要，但ATR对更广泛的DNA损伤和DNA复制问题作出反应。ATR如何被各种形式的DNA损伤和复制应激激活是基因组维持研究的一个基本问题。ATR在人体细胞中与ATRIP形成复合物。我们和其他人已经表明，RPA包被的单链DNA（ssDNA）是DNA损伤位点的关键结构，并强调了招募和激活ATR-ATRIP的复制叉。然而，ATR-ATRIP如何在RPA-ssDNA上被激活以及它如何调节DNA修复仍然知之甚少。在这项研究中，我们发现ATRIP是SUMO化的DNA损伤刺激的方式，ATRIP SUMO化在ATR激活中起着关键作用。此外，我们已经确定了ATR在同源重组（HR）中的新功能，为ATR在DNA修复中的作用提供了关键线索。最令人兴奋的是， 我们发现，具有特定遗传改变的癌细胞对HR途径上瘾，并且对ATR抑制剂高度敏感，这提出了在癌症治疗中靶向ATR的概念上的新方法。在本申请中，我们提出解决（1）ATRIP SUMO化如何驱动ATR激活，（2）ATR如何调节HR，以及（3）如何靶向癌症中的ATR。如果成功的话，我们的研究将大大推进我们对ATR激活机制、ATR在DNA修复中的作用以及ATR作为治疗靶点的潜力的理解。我们的研究可能最终将ATR的机制研究带入ATR抑制剂在肿瘤靶向治疗中的合理使用。

 DESCRIPTION (provided by applicant): Genomic instability is a hallmark of cancer. The maintenance of genomic stability relies on the concerted action of a number of cellular processes, such as DNA replication, DNA repair, and cell-cycle transitions. The central coordinator of these cellular processes is the DNA damage-signaling pathway, which is often referred to as the checkpoint. In human cells, the checkpoint is orchestrated by two master kinases, ATM and ATR. While ATM is critical for the response to DNA double-stranded breaks (DSBs), ATR responds to a much broader spectrum of DNA damage and DNA replication problems. How ATR is activated by various forms of DNA damage and replication stress is a fundamental question for the research of genome maintenance. ATR forms a complex with ATRIP in human cells. We and others have shown that single-stranded DNA (ssDNA) coated by RPA is the key structure at sites of DNA damage and stressed replication forks that recruits and activates ATR-ATRIP. Nevertheless, how exactly ATR-ATRIP is activated on RPA-ssDNA and how it regulates DNA repair is still poorly understood. In this study, we have found that ATRIP is SUMOylated in a DNA damage-stimulated manner, and that ATRIP SUMOylation plays a key role in ATR activation. Furthermore, we have identified a novel function of ATR in homologous recombination (HR), providing a critical clue to the role for ATR in DNA repair. Mostly excitingly, we found that cancer cells with specific genetic alterations are addicted to the HR pathway and highly sensitive to ATR inhibitors, presenting a conceptually new way to target ATR in cancer therapy. In this application, we propose to address (1) how ATRIP SUMOylation drives ATR activation, (2) how ATR regulates HR, and (3) how to target ATR in cancers. If successful, our studies will greatly advance our understanding of the mechanism of ATR activation, the role for ATR in DNA repair, and the potential of ATR as a therapeutic target. Our research may ultimately bring the mechanistic studies on ATR to the rational use of ATR inhibitors in targeted cancer therapy.