Identification of a new strategy for cancer therapy

 描述(申请人提供)：PARP-1抑制剂是最近开发的，用于靶向具有同源重组(HR)修复缺陷的癌症，如BRCA1或BRCA2突变。然而，BRCA1或BRCA2突变只发生在低比例的人类癌症中，这一事实严重限制了PARP抑制剂的使用。因此，识别控制HR修复的关键调控因子对于进一步了解DNA损伤反应具有重要意义，并可能为癌症治疗提供一个重要的治疗靶点。在这项提案中，我们的目标是在HR修复途径中寻找新的调控因子，这些调控因子可以作为可用药的靶点，并与PARP抑制剂一起用作潜在靶点，以触发癌症的合成致命性。我们的研究提供了令人信服的证据，证明Skp2 E3连接酶是一种新的调节因子，对ATM激活和HR修复至关重要，揭示了 DNA损伤反应是如何调控的，并进一步为癌症的合成致死策略提供了一个新的范例。该提案的目的是确定Skp2如何被招募到DNA损伤焦点来调节ATM的激活，Skp2介导的NBS1泛素化如何调节HR修复，并寻找一种新的癌症治疗策略。我们将通过实现以下具体目标来实现我们的目标。目的1)了解Skp2 E3连接酶在HR修复和基因组不稳定性中的新调控。目的2)研究MRN复合体中K63连接的泛素化在端粒维持和DNA损伤修复中的作用。目的3.了解Skp2调节激酶信号转导和肿瘤发生的新机制，用于癌症治疗。总之，我们的研究为MRN复合体如何调节ATM激活提供了分子方面的见解。我们发现，Skp2 E3连接酶是ATM募集到DNA损伤中心并随后激活ATM所必需的关键调节因子。到目前为止，所有在过去十年中发现的Skp2底物都经历了泛素依赖的蛋白酶体降解。然而，在这项研究中，我们首次发现了Skp2在DNA损伤反应中的一个新的非蛋白降解功能。Skp2触发非蛋白水解性K63连接的NBS1泛素化，促进ATM的激活和募集到DNA损伤中心。此外，我们首次开发了可用于癌症靶向的特定Skp2抑制剂。我们的研究提供了令人信服的证据，证明Skp2 E3连接酶是一种对ATM激活和HR修复至关重要的新调节因子，为如何调控DNA损伤反应提供了新的线索，并进一步为癌症治疗的合成致死策略提供了新的范式。

 DESCRIPTION (provided by applicant): PARP-1 inhibitors are recently developed and used to target cancers with a defect in homologous recombination (HR) repair, such as BRCA1 or BRCA2 mutations. However, the usage of the PARP inhibitors is profoundly limited by the fact that BRCA1 or BRCA2 mutations only occur in low percentages of human cancers. Thus, identifying critical regulators that control the HR repair is of significance in further understandng DNA damage response and may provide an important therapeutic target for cancer treatments. In this proposal, we set our goals to identify novel regulators in the HR repair pathway that can serve as druggable targets and be used as potential targets in combination with PARP inhibitor to trigger synthetic lethality in cancers. Our study provides the convincing evidence that Skp2 E3 ligase is a novel regulator critical for ATM activation and HR repair, revealing an insight into how DNA damage response is regulated and further providing a new paradigm for a synthetic lethal strategy for cancers. The objectives of this proposal are to determine how Skp2 is recruited to DNA damage foci to regulate ATM activation, how Skp2-medaited NBS1 ubiquitination regulates HR repair and to identify a novel therapeutic strategy for cancer treatment. We will pursue our goals by performing the following specific aims. Aim 1) Understanding the novel regulation of Skp2 E3 ligase in HR repair and genomic instability. Aim 2) To determine the role of K63-linked ubiquitination in the component of the MRN complex in telomere maintenance and DNA damage repair. Aim 3. Understanding novel mechanisms by which Skp2 regulates kinase signaling and tumorigenesis for cancer therapy. In sum, our study provides molecular insights into how MRN complex regulates ATM activation. We show that Skp2 E3 ligase is a critical regulator required for the recruitment of ATM to DNA damage foci and subsequent ATM activation. So far, all Skp2 substrates identified in the last decade are known to undergo ubiquitin- dependent proteasome degradation. However, in this study we identify for the first time a novel non-proteolytic function for Skp2 in DNA damage response. Skp2 triggers non-proteolytic K63-linked ubiquitination of NBS1 and facilitates activation and recruitment of ATM to DNA damage foci. Moreover, we have developed for the first time specific Skp2 inhibitors that can be used for cancer targeting. Our study provides convincing evidence that Skp2 E3 ligase is a novel regulator critical for ATM activation and HR repair, shedding new lights on how DNA damage response is regulated and further offering a new paradigm for a synthetic lethal strategy for cancer treatments.