Role of DNA Replication Stress in Genome Instability and Cancer

项目摘要 在癌症的发展过程中，初期肿瘤表现出复制应激的迹象，包括 起源放电的失调、停滞的分叉、DSB和p53的激活。复制压力在多大程度上 癌症的驱动力只能通过进一步表征稳定和 修复复制叉，允许重新启动以完成复制，并诱导保护性衰老或 癌前细胞凋亡状态。虽然HR（同源重组）蛋白参与修复， 强调复制叉，他们的确切作用和调控叉知之甚少，相比之下， 在DSBs上运行。我们将使用FA/BRCA（范可尼贫血/乳腺癌）途径来解决这些问题 复制叉救援作为一个重点。最近，我们证明了DNA 2解旋酶/核酸酶在 FA/BRCA通路。DNA 2与MRN复合体和BLM或WRN一起沿着参与切除肿瘤。 DSB，产生诱导DNA损伤应激反应的3'突出端。这些悬突还 招募Rad 51形成细丝，在重组和细丝形成过程中参与股侵入 在压力复制分叉保护期间。由于DNA 2对DNA复制也是必不可少的，我们假设 它的HR/切除相关功能的重要部分是在基因组不稳定的ssDNA，缺口，DSB或 在复制应力期间出现反向分叉。DNA 2的消耗抑制FANCD 2 - 1中的化学敏感性 缺陷细胞，我们将研究这种拮抗作用的基础，我们提出这与调节 通过FA/BRCA途径组分切除DNA 2。在目标1中，我们将使用细胞遗传学、基因组学和 生物化学研究FANCD 2和DNA 2在途径选择中的相互作用（HR、NHEJ和alt-NHEJ） 可能竞争DNA末端或在FA/BRCA修复停滞的复制叉过程中出现的缺口。在目标2中， 我们将进一步定义DNA 2/FANCD 2在复制分叉保护中的相互作用，并使用iPOND重新启动， 单DNA分子分析，突出了FRA 16 D的新分析，FRA 16 D是一个不稳定的常见脆性位点 在FANCD 2缺陷细胞中。在目标3中，我们描述了一种创新的，高分辨率的方法来研究 这些因素对复制动力学的贡献基于在染色体位点上停止复制， 特异性蛋白质/DNA复制阻断剂。我们研究的一个新工具将是我们开发的DNA 2抑制剂， 其也可能通过使某些肿瘤对化疗敏感而具有治疗潜力， 复制应力

PROJECT SUMMARY During the development of cancer, the incipient tumors exhibit signs of replication stress, including deregulation of origin firing, stalled forks, DSBs, and activation of p53. To what extent replication stress is a driving force in cancer can only be understood by further characterization of the pathways that stabilize and repair replication forks, allow restart for completion of replication, and induce a protective senescence or apoptotic state in precancerous cells. While HR (homologous recombination) proteins are involved in repair of stressed replication forks, their precise roles and regulation at forks are poorly understood compared to their function at DSBs. We will address these issues using the FA/BRCA (Fanconi anemia/Breast cancer) pathway of replication fork rescue as a focus. Recently, we demonstrated that DNA2 helicase/nuclease, plays a role in the FA/BRCA pathway. DNA2 is involved along with the MRN complex and BLM or WRN in resection of DSBs, giving rise to the 3’ overhangs that induce the DNA damage stress response. These overhangs also recruit Rad51 to form filaments that participate in strand invasion during recombination and filament formation during stressed replication fork protection. Since DNA2 is also essential for DNA replication, we hypothesize that an important part of its HR/resection-related function is at genome destabilizing ssDNAs, gaps, DSBs or reversed forks arising during replication stress. Depletion of DNA2 suppresses chemosensitivity in FANCD2- deficient cells, and we will study the basis of this antagonism, which we propose is related to regulation of DNA2 resection by FA/BRCA pathway components. In Aim 1, we will use cytogenetics, genomics, and biochemistry to study the interplay of FANCD2 and DNA2 in choice of pathways (HR, NHEJ, and alt-NHEJ) that may compete for DNA ends or gaps arising during FA/BRCA repair of stalled replication forks. In Aim 2, we will further define the DNA2/FANCD2 interplay in replication fork protection and restart using iPOND and single DNA molecule analysis, highlighting novel analysis of FRA16D, a common fragile site that is unstable in FANCD2 deficient cells. In Aim 3, we describe an innovative, high resolution approach to studying the contribution of these factors to replication dynamics based on stalling replication at a chromosomal, site- specific protein/DNA replication block. A novel tool for our studies will be the DNA2 inhibitor we developed, which may also have therapeutic potential by sensitizing certain tumors to chemotherapies that cause replication stress.