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)修复中的作用，特别是在同源重组(HR)介导的DSB修复中的作用，与其在维持基因组稳定和抑制肿瘤方面的作用密切相关。然而，BRCA1这种DSB修复功能的分子机制仍不清楚。我们的研究将集中于BRCA1和BRCA1相关蛋白CtIP如何参与DSB修复的研究，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与修复蛋白复合体Mre11/Rad50/Nbs1相互作用的重要桥梁，了解CtIP的细胞周期调节对于确定BRCA1在HR激活中的确切作用是重要的。其次，我们将检测CtIP和BRCA1/CtIP/MRN复合体对DNA的活性，从而揭示BRCA1在DSB修复中作用的生化基础。第三，我们将研究BRCA1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部位保护中的重要性。第四，我们将通过一种特定的蛋白质-蛋白质相互作用来分析CtIP在DSB上的募集，这可能促进DSB近端染色质上BRCA1/CtIP/MRN的复合形成，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关键功能的分子机制，并将为BRCA1作为肿瘤抑制因子的功能提供重要的见解。这些研究的发现还将为乳腺癌的预防和治疗开辟新的治疗措施。

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.