Role of the Mre11/Rad50/Nbs1 complex in DNA damage response pathways

描述（由申请人提供）：Mre11、Nbs1和Rad50形成一种保守的蛋白质复合物，是维持基因组稳定性所必需的。在人类中，Nbs1和Mre11分别与奈megen断裂综合征（NBS）和共济失调-毛细血管扩张样疾病（ATLD）有关，受影响的患者易患癌症。Mre11/Rad50/Nbs1复合体（MRN）在DNA双链断裂（DSB）修复和细胞周期检查点控制中起着关键作用，但这些功能在细胞周期和DNA损伤响应中如何调节的详细机制尚不清楚。整个基因组需要在s期被忠实地复制，在s期最容易发生基因毒性损伤的DNA代谢活跃时期。因此，在s期保持基因组完整性是最重要的。我们提出的研究将集中于了解Mre11/Rad50/Nbs1复合体（MRN）在保持基因组完整性，特别是介导s期相关损伤反应中的关键作用的机制。首先，我们将通过质谱分析确定DNA损伤诱导的Mre11磷酸化，并研究这些磷酸化事件在s期检查点控制和DNA DSB修复中的生物学意义。其次，我们将确定MRN在崩溃分叉处DSB修复和复制重启中的作用。由于复制叉在遇到复制障碍时可能会停滞和崩溃，MRN修复崩溃复制叉上的DSB的功能对于维持s期基因组完整性至关重要。第三，我们将研究MRN在s期相关损伤反应中作用的分子基础。我们将研究MRN与复制分叉的关联，并了解这种相互作用在s期相关事件中检查点激活和损伤修复中的作用。这些研究将为MRN在维持基因组稳定性中的关键功能的分子机制提供重要见解，并将阐明该复合物的功能障碍如何导致与癌症相关的人类疾病。公共卫生相关性：Nbs1和Mre11基因突变分别导致人类疾病奈梅根断裂综合征（NBS）和共济失调-毛细血管扩张样疾病（ATLD），受影响的患者易患癌症。了解Mre11/Rad50/Nbs1复合物在DNA损伤反应和DNA损伤修复中的作用，将有助于揭示防止基因组不稳定和癌症的细胞机制。这些研究最终将有助于开发与基因组不稳定性和癌症相关的人类疾病的治疗干预措施。

DESCRIPTION (provided by applicant): Mre11, Nbs1 and Rad50 form a conserved protein complex that is required for the maintenance of genome stability. In humans, Nbs1 and Mre11 are linked to the Nijmegen breakage syndrome (NBS) and ataxia-telangiectasia-like disorder (ATLD), respectively, and the affected patients are predisposed to cancer. The Mre11/Rad50/Nbs1 complex (MRN) plays a critical role in DNA double stranded break (DSB) repair and cell cycle checkpoint control, but the detailed mechanisms of how these functions are regulated during the cell cycle and in response to DNA damage are not clear. The entire genome needs to be faithfully replicated in S-phase, wherein genotoxic insults most easily occur during the period of active DNA metabolism. Thus, preserving genome integrity in S-phase is most demanding. Our proposed studies will focus on the investigation to understand the mechanisms underlying the critical roles of the Mre11/Rad50/Nbs1 complex (MRN) in preserving genome integrity, especially in mediating S-phase-associated damage responses. First, we will identify DNA damage-induced Mre11 phosphorylation by mass spectrometry analysis and investigate the biological significance of these phosphorylation events in intra-S- phase checkpoint control and DNA DSB repair. Second, we will determine the role of MRN in DSB repair and replication restart at collapsed forks. Since replication forks can stall and collapse when encountering replication obstacles, the function of MRN in repairing DSB at collapsed replication forks is critical for maintaining genome integrity in S-phase. Third, we will investigate the molecular basis underlying the role of MRN in the S-phase associated damage response. We will study the association of MRN with replication forks and understand the role of this interaction in checkpoint activation and damage repair in S-phase related events. These studies will provide significant insights into the molecular mechanisms underlying the critical function of MRN in the maintenance of genome stability and will shed light on how malfunction of this complex could lead to human diseases associated with cancer. PUBLIC HEALTH RELEVANCE: Mutations in Nbs1 and Mre11 genes lead to human diseases, Nijmegen breakage syndrome (NBS) and ataxia-telangiectasia-like disorder (ATLD), respectively, and the affected patients are predisposed to cancer. Understanding the role of the Mre11/Rad50/Nbs1 complex in DNA damage response and DNA damage repair will shed light on the cellular mechanisms that prevent genome instability and cancer. These studies will ultimately help develop therapeutic interventions for human diseases associated with genome instability and cancer.