Role of BRCA1 and its association protein CtlP in DNA double-strand break repair

描述（由申请人提供）：乳腺癌肿瘤抑制蛋白BRCA 1参与DNA损伤反应的多个方面。其在DNA双链断裂（DSB）修复中的功能，特别是在同源重组（HR）介导的DSB修复中的功能与其在维持基因组稳定性和肿瘤抑制中的作用高度相关。然而，BRCA 1的这种DSB修复功能的分子机制仍然不清楚。我们的研究将集中在BRCA 1和BRCA 1相关蛋白CtIP如何参与DSB修复的调查，这将有助于阐明BRCA 1在肿瘤抑制中的作用机制。 首先，我们将研究细胞周期依赖的CtIP磷酸化和探测这些磷酸化事件在HR介导的DSB修复的生物学意义。由于CtIP是BRCA 1与修复蛋白复合物Mre 11/Rad 50/Nbs 1相互作用的关键参与者，因此了解细胞周期介导的CtIP调节对于确定BRCA 1在HR激活中的确切作用非常重要。其次，我们将检查CtIP和BRCA 1/CtIP/MRN复合物对DNA的酶活性，这将揭示BRCA 1在DSB修复中功能的生化基础。第三，我们将研究BRCA 1和CtIP在复制叉崩溃引起的DSB修复中的作用，并探讨这种修复活动在脆弱位点保护中的重要性。第四，我们将分析CtIP通过特定的蛋白质-蛋白质相互作用募集到DSB，这可能促进BRCA 1/CtIP/MRN在DSB近端染色质处形成复合物，从而促进HR介导的DSB修复。 总之，这些研究将有助于阐明BRCA 1和CtIP在维持基因组稳定性方面关键功能的分子机制，并将为BRCA 1如何作为肿瘤抑制因子提供重要见解。这些研究的结果也将为乳腺癌的预防和治疗开辟新的治疗干预途径。 公共卫生相关性：BRCA 1是一种乳腺癌肿瘤抑制因子，BRCA 1的生殖系突变约占遗传性乳腺癌的40%。我们将研究BRCA 1及其相关蛋白CtIP在DNA双链断裂修复中的作用，这与BRCA 1的肿瘤抑制功能高度相关。这些研究将揭示BRCA 1如何参与乳腺癌的预防，并将有助于为开发乳腺癌预防和治疗的治疗策略开辟新的途径。

DESCRIPTION (provided by applicant): The breast cancer tumor suppressor protein BRCA1 participates in multiple aspects of DNA damage responses. Its function in DNA double-strand break (DSB) repair, especially in homologous recombination (HR)-mediated DSB repair is highly relevant to its role in the maintenance of genome stability and tumor suppression. However, the molecular mechanism underlying this DSB repair function of BRCA1 is still not clear. Our proposed studies will focus on the investigation of how BRCA1 and the BRCA1-association protein CtIP participate in DSB repair, which will help to elucidate the mechanisms underlying BRCA1 function in tumor suppression. First, we will study cell cycle-dependent phosphorylation of CtIP and probe the biological significance of these phosphorylation events in HR-mediated DSB repair. Since CtIP is a critical player to bridge the interaction of BRCA1 with the repair protein complex Mre11/Rad50/Nbs1, understanding cell cycle-mediated regulation of CtIP is important for determining the exact role of BRCA1 in the activation of HR. Second, we will examine the enzymatic activities of CtIP and the BRCA1/CtIP/MRN complex on DNA, which will reveal the biochemical basis for the function of BRCA1 in DSB repair. Third, we will investigate the role of BRCA1 and CtIP in the repair of DSBs caused by replication fork collapse, and probe the importance of this repair activity in fragile site protection. Fourth, we will analyze the recruitment of CtIP to DSBs through a specific protein-protein interaction, which may promote the complex formation of BRCA1/CtIP/MRN at chromatin proximal to DSBs, thus facilitating HR-mediated DSB repair. Together, these studies will help to elucidate the molecular mechanisms underlying the critical function of BRCA1 and CtIP in the maintenance of genome stability and will provide significant insights into how BRCA1 functions as a tumor suppressor. The findings from these studies will also open new avenues towards novel therapeutic interventions for breast cancer prevention and treatment. PUBLIC HEALTH RELEVANCE: BRCA1 is a breast cancer tumor suppressor, and germ line mutations in BRCA1 account for approximately 40% of hereditary breast cancers. We will investigate the role of BRCA1 and its association protein CtIP in DNA double-strand break repair, which is highly relevant to the tumor suppressor function of BRCA1. These studies will shed light on how BRCA1 is involved in the prevention of breast cancer and will help to open new avenues for developing therapeutic strategies for breast cancer prevention and treatment.