Genomic Instability at DNA Nicks

描述（由申请人提供）：DNA缺口的基因组不稳定性我们的目标是了解DNA缺口启动导致基因组不稳定事件的机制。刻痕是最常见的DNA损伤。人体细胞每天经历数以万计的损伤，这些损伤来自活性氧、电离辐射以及许多DNA修复途径中的中间产物。单链断裂修复途径可以有效而忠实地修复缺口，并且它们没有被视为对基因组稳定性的威胁。我们实验室最近的研究结果挑战了这一观点。我们已经证明，切口可以启动同源性定向修复（HDR），这是肿瘤中常见的两种形式的基因组不稳定性的来源，即拷贝数改变（CNA）和杂合性缺失（LOH）。裂口处的HDR不同于双链断裂处的HDR。它与转录有关，并优先修复转录的DNA链。缺口处的HDR可以通过一个非常有效的替代途径进行，该途径通常被规范HDR抑制，这表明替代HDR在缺乏规范HDR的肿瘤中是活跃的。我们建议通过以下三个具体目的来确定尼克斯启动HDR和基因组不稳定性的机制：目的1。定义执行和调节镍源性HDR的因素和途径。目标2。目的：探讨细胞周期是否调控细胞内的HDR变化。目标3。为了确定HDR位点是如何与转录结合的。拟议的研究将使我们能够识别有切口引发HDR风险的肿瘤，并将其暴露于切口的风险降至最低。它将确定减少镍引发的基因组不稳定性的治疗靶点，以及激活基因组不稳定性以产生杀死细胞的DNA损伤的治疗靶点。

DESCRIPTION (provided by applicant): Genomic Instability at DNA Nicks Our goal is to understand the mechanisms by which DNA nicks can initiate events that lead to genomic instability. Nicks are the most common form of DNA damage. Human cells experience tens of thousands of nicks each day, from reactive oxygen species, ionizing radiation, and as intermediates in many pathways of DNA repair. Nicks can be efficiently and faithfully repaired by the single strand break repair pathway, and they have not been viewed as a threat to genomic stability. Recent results from our laboratory challenge that view. We have shown that nicks can initiate homology-directed repair (HDR), a source of two forms of genomic instability common in tumors, copy number alteration (CNA) and loss of heterozygosity (LOH). HDR at nicks is distinct from HDR at double strand breaks. It is associated with transcription and preferentially repairs the transcribed DNA strand. HDR at nicks can proceed via a very efficient alternative pathway that is normally suppressed by canonical HDR, suggesting that alternative HDR is active in tumors that are deficient in canonical HDR. We propose to define the mechanisms by which nicks initiate HDR and genomic instability, by carrying out the following three specific Aims: Aim 1. To define the factors and pathways that carry out and regulate nick-initiated HDR. Aim 2. To establish whether the cell cycle regulates alternative HDR at nicks. Aim 3. To determine how HDR at nicks is coupled to transcription. The proposed research will enable us to identify tumors at risk for nick-initiated HDR, and minimize their exposure to nicks. It will identify targets for therapies that diminish nick-initiated genomic instability, as well as targets for therapies that activate genomic instability to create DNA damage that kills cells.