Regulation of the ATR Checkpoint Kinase by DNA Damage

 描述(申请人提供)：基因组不稳定是癌症的一个标志。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，检查点由两个主激酶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DNA损伤和DNA复制问题的反应范围要广得多。ATR是如何被各种形式的DNA损伤和复制应激激活的，这是基因组维护研究的一个基本问题。ATR在人体细胞中与ATrip形成复合体。我们和其他人已经证明，RPA包被的单链DNA(SsDNA)是DNA损伤和应激复制叉处的关键结构，它招募并激活ATR-ATrip。然而，ATR-ATIP是如何在RPA-ssDNA上被激活的，以及它是如何调节DNA修复的，仍然知之甚少。在本研究中，我们发现，在DNA损伤刺激的方式下，ATAP被SUMO化，并且该SUMO化在ATR激活中起着关键作用。此外，我们还发现了ATR在同源重组(HR)中的一个新功能，为研究ATR在DNA修复中的作用提供了重要线索。最令人兴奋的是， 我们发现，具有特定基因改变的癌细胞对HR途径上瘾，并对ATR抑制剂高度敏感，这为在癌症治疗中靶向ATR提供了一种新的途径。在这个应用中，我们建议解决(1)ATAP SUMO化如何驱动ATR激活，(2)ATR如何调节HR，以及(3)如何在癌症中靶向ATR。如果成功，我们的研究将极大地促进我们对ATR激活机制的理解，ATR在DNA修复中的作用，以及ATR作为治疗靶点的潜力。我们的研究可能最终将ATR的机制研究带入ATR抑制剂的靶向治疗的合理使用中。

 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.