Genomic Instability at DNA Nicks

描述(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缺口引发导致基因组不稳定的事件的机制。尼克斯是最常见的DNA损伤形式。人类细胞每天经历数以万计的缺口，来自活性氧物种、电离辐射，以及作为许多DNA修复途径的中间体。NICKs可以通过单链断裂修复途径有效而忠实地修复，并且它们并不被视为对基因组稳定性的威胁。我们实验室的最新结果挑战了这一观点。我们已经证明，NICS可以启动同源定向修复(HDR)，这是肿瘤中常见的两种形式的基因组不稳定的来源，拷贝数改变(CNA)和杂合性丢失(LOH)。NICKS的HDR与双链断裂的HDR不同。它与转录相关，优先修复转录的DNA链。NICKS的HDR可以通过一种非常有效的替代途径进行，这通常被典型性HDR抑制，这表明替代HDR在缺乏典型性HDR的肿瘤中是活跃的。我们建议通过实现以下三个具体目标来确定NICS启动HDR和基因组不稳定性的机制：目的1.确定执行和调节NICK启动的HDR的因素和途径。目的2.确定细胞周期是否调节NICS时交替的HDR。目的3.确定NICS的HDR是如何与转录结合的。这项拟议的研究将使我们能够识别存在NICK引发HDR风险的肿瘤，并将它们对NICK的暴露降至最低。它将确定减少尼克引发的基因组不稳定的治疗目标，以及激活基因组不稳定以造成DNA损伤从而杀死细胞的治疗目标。

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.