Role of DNA Replication Stress in Genome Instability and Cancer

项目总结 在癌症的发展过程中，早期肿瘤表现出复制压力的迹象，包括 解除对起始点火、停滞的叉子、DSB和P53的激活的管制。复制压力在多大程度上是一种 癌症的驱动力只能通过进一步表征稳定和 修复复制分叉，允许重新启动以完成复制，并诱导保护性衰老或 癌前细胞的凋亡状态。而HR(同源重组)蛋白参与修复 强调复制分叉，它们在分叉中的确切作用和调节与它们的 在DSB上发挥作用。我们将使用FA/BRCA(Fanconi贫血/乳腺癌)途径来解决这些问题 以复制叉子救援为重点。最近，我们证明了DNA2解旋酶/核酸酶在 FA/BRCA途径。DNA2与MRN复合体和BLM或WRN一起参与肿瘤切除 DSB，产生3‘突起，诱导DNA损伤应激反应。这些突出物也是 招募RAD51形成细丝，参与重组和细丝形成过程中的链入侵 在紧张的复制分叉保护期间。由于DNA2对DNA复制也是必不可少的，我们假设 其HR/切除相关功能的一个重要部分是在基因组上破坏SSDNA、GAP、DSB或 在复制应激过程中出现的反向分叉。DNA2缺失抑制FANCD2-细胞对化疗的敏感性 缺乏细胞，我们将研究这种拮抗的基础，我们认为这与调节 通过FA/BRCA通路组件切除DNA2。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FANCD2和DNA2在选择途径(HR、NHEJ和ALT-NHEJ)中的相互作用 这可能会竞争在FA/BRCA修复停滞的复制叉时出现的DNA末端或缺口。在目标2中， 我们将进一步定义复制分叉保护中的DNA2/FANCD2交互作用，并使用iPOND和 单DNA分子分析，突出了对FRA16D的新分析，FRA16D是一种常见的不稳定的脆性部位 在FANCD2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，基于染色体上的复制停滞。 特异性蛋白质/DNA复制阻断。我们研究的一个新工具将是我们开发的DNA2抑制剂， 它还可能通过使某些肿瘤对引起 复制压力。

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.