Define redundant functions of H2AX and NBS1 in DNA repair

项目概要 破译基因组不稳定性和肿瘤发生背后的分子机制是长期的任务 我实验室的目标。该提案的总体目标反映了我们对获得全面的 了解参与 DNA 修复的网络并确定这些蛋白质和途径如何 交叉、相互作用、沟通、协调和协作以进行基因组维护。短期目标是 对几种 DNA 损伤信号传导和修复途径进行详细的机制研究，这将 为实现我们利用 DNA 修复网络进行癌症治疗的长期目标奠定了基础。 该提案将定义两条重叠的 DNA 损伤信号通路，它们共同对于 细胞存活。我们和其他研究人员构建了一条作用于下游的精心设计的信号通路 H2AX 并调节 DNA 位点上许多 DNA 损伤修复蛋白的招募和积累 休息。该 H2AX 依赖性途径由 H2AX、MDC1、RNF8 和 RNF168 组成。不过，修复 在 H2AX、MDC1、RNF8 或 RNF168 缺陷细胞或小鼠中观察到的缺陷很轻微，这增加了可能性 存在一种独立于 H2AX 的机制参与这些下游修复的招募 蛋白质。我们认为这条 H2AX 独立途径受 NBS1 控制。 根据我们之前的研究和本提案中提供的初步数据，我们假设 H2AX 和 NBS1 依赖性途径参与 DNA 损伤反应，对细胞至关重要 生存。我们认为这两条途径具有冗余功能，特别是在促进同源性方面 重组修复。然而，它们并不是完全分开的，因为它们在多个点相交。这个 描述这两条冗余路径的功能对我们来说是相当具有挑战性的。它是 未知我们是否可以阐明单一路径对不断增长的网络的贡献，即 我们解开网络以了解不同路径交叉和贡献的机制 生物过程？我们将在本申请中解决这个问题，并进一步研究 H2AX 和 NBS1 依赖性途径共同作用以确保细胞存活和 完成DNA修复。我们提出以下具体目标：1）确定NBS1是否起作用 与已建立的H2AX-MDC1-RNF8-RNF168通路冗余，以确保细胞存活； 2) 划定 NBS1依赖途径； 3）探索NBS1和H2AX引起细胞致死的机制 共同耗尽。这些研究不仅能让我们了解 H2AX 和 NBS1 在 体内，还将揭示研究蛋白质功能和当今复杂信号传导途径的方法 网络。此外，这些研究的结果将为利用 DNA 修复缺陷和 将合成致死概念应用于癌症患者的精准医疗。

Project Summary Deciphering the molecular mechanisms underlying genomic instability and tumorigenesis is the long-term goal of my laboratory. The broad objective, of this proposal, reflects our pursuit to gain a comprehensive understanding of the network involved in DNA repair and to determine how these proteins and pathways intersect, interact, communicate, coordinate, and collaborate for genome maintenance. The short-term goal is to perform detailed mechanistic studies of several DNA damage signaling and repair pathways, which will provide the foundation to achieve our long-term goal of exploiting DNA repair network for cancer therapy. This proposal will define two overlapping DNA damage-signaling pathways that together are essential for cell survival. We and other researchers have constructed an elaborate signaling pathway that acts downstream of H2AX and regulates the recruitment and accumulation of many DNA damage repair proteins at sites of DNA breaks. This H2AX-dependent pathway is composed of H2AX, MDC1, RNF8, and RNF168. However, repair defects observed in H2AX-, MDC1-, RNF8-, or RNF168-deficient cells or mice are mild, raising the possibility that there is an H2AX-independent mechanism involved in the recruitment of these downstream repair proteins. We propose that this H2AX-independent pathway is controlled by NBS1. On the basis of our previous studies and preliminary data presented in this proposal, we hypothesize that the H2AX- and NBS1-dependent pathways are involved in the DNA damage response and are critical for cell survival. We believe that these two pathways have redundant functions, especially in promoting homologous recombination repair. However, they are not completely separate, since they intersect at multiple points. This makes it considerably challenging for us to delineate the functions of these two redundant pathways. It is unknown whether we can elucidate the contribution of a single pathway to the ever-growing network, i.e., can we untangle the network to understand the mechanisms by which different pathways intersect and contribute to biological processes? We will address this question in this application and we will further study the mechanisms by which the H2AX- and NBS1-dependent pathways act together to ensure cell survival and the completion of DNA repair. We propose the following specific aims: 1) determine whether NBS1 acts redundantly with the established H2AX-MDC1-RNF8-RNF168 pathway to ensure cell survival; 2) delineate the NBS1-dependent pathway; and 3) explore the mechanisms underlying cell lethality caused by NBS1 and H2AX co-depletion. These studies will not only allow us to understand the redundant functions of H2AX and NBS1 in vivo but will also reveal ways to investigate the functions of proteins and pathways in today’s complex signaling networks. Moreover, results from these studies will provide the rationale for exploiting DNA repair defect and applying synthetic lethality concept in precision medicine for cancer patients.