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

描述（申请人提供）：乳腺癌肿瘤抑制蛋白BRCA1参与DNA损伤反应的多个方面。它在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，与其在维持基因组稳定性和抑制肿瘤中的作用高度相关。然而，BRCA1的DSB修复功能的分子机制尚不清楚。我们将重点研究BRCA1和BRCA1相关蛋白CtIP如何参与DSB修复，这将有助于阐明BRCA1在肿瘤抑制中的作用机制。首先，我们将研究细胞周期依赖性的CtIP磷酸化，并探讨这些磷酸化事件在hr介导的DSB修复中的生物学意义。由于CtIP是BRCA1与修复蛋白复合物Mre11/Rad50/Nbs1相互作用的桥梁，因此了解细胞周期介导的CtIP调控对于确定BRCA1在HR激活中的确切作用非常重要。其次，我们将检测CtIP和BRCA1/CtIP/MRN复合物在DNA上的酶活性，这将揭示BRCA1在DSB修复中的功能的生化基础。第三，我们将研究BRCA1和CtIP在修复由复制叉崩溃引起的dsb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-蛋白相互作用募集到DSB，这可能促进BRCA1/CtIP/MRN在DSB近端染色质上的复合体形成，从而促进hr介导的DSB修复。总之，这些研究将有助于阐明BRCA1和CtIP在维持基因组稳定性中的关键功能的分子机制，并将为BRCA1如何作为肿瘤抑制因子发挥作用提供重要见解。这些研究的发现也将为乳腺癌预防和治疗的新型治疗干预开辟新的途径。

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.