Measuring nucleotide excision repair in human populations

项目总结 核苷酸切除修复(NER)是一种dna修复机制，它识别并移除笨重的螺旋扭曲。 来自核基因组的损伤。NER的关键底物是紫外线(UV)辐射引起的损伤 环境暴露在阳光下和一系列氧化的DNA损伤是内源性的。这是 着色性干皮病(XP)患者戏剧性地说明了这一点，这种疾病是由遗传缺陷引起的 内尔。XP患者患皮肤癌和早发性神经变性的风险增加10,000倍。XP是 异质性，从轻微到严重的衰弱。XP严重性与以下程度成正比 内尔被打乱了。这表明NER的细微缺陷，例如由于NER基因的多态， 可能对患皮肤癌的风险有一定的影响，但影响很大。由于皮肤癌影响20%的美国人 而且是可以预防的(通过避免在环境中暴露在紫外线下)，识别那些处于危险之中的人可能会有巨大的 对美国人的健康和医疗成本的影响。识别风险人群的最大障碍是 缺乏一种快速、廉价、适用于安全和容易地采集样本的NER检测方法 从病人那里。NER发生在一系列步骤中，涉及识别DNA损伤的位置，解开 DNA局部切除，含有病变的单链寡核苷酸的切除，以及模板DNA合成 以填补剩余的空白。NER是从基因组中移除紫外线诱导的光刻的唯一方法 人类细胞。因此，通过检测和定量紫外光诱导的DNA合成来测量NER。 细胞周期的S期外，或非程序性DNA合成(UDS)。从历史上看，UDS测量 需要使用放射性标记的核苷和/或专门设备。我们开发了一种方法来 使用胸腺嘧啶核苷类似物5-乙炔-2‘-脱氧尿嘧啶核苷和Click-it化学进行荧光测量 用流式细胞仪检测UDS。此方法可应用于外周血细胞以快速测定NER 需要微创的样本采集。XP患者的UDS从10%到50%不等。什么都不知道 关于UDS在50%-100%之间对健康的影响，或者如何定义100%的NER容量。这 该项目旨在通过优化我们的功能分析和证据来纠正这些知识差距 概念先导人体研究。这项检测将应用于加州大学现有的患者队列 迈阿密皮肤癌诊所，NIH未诊断疾病计划或注册马里兰大学 Amish长寿研究，以询问NER能力与皮肤癌高风险之间的关系，早期 起病神经退行性变，分别在家系内。这个项目将产生一个NER分析 适用于更大的人群研究，旨在测试NER容量、环境 暴露和疾病风险，并开始定义“正常”的NER能力。化验结果可能具有重要的意义 对皮肤、黑色素瘤、肺或头颈部鳞状细胞癌或基底细胞癌风险的影响 癌症、神经退行性变和癌症化疗的耐药性被识别和处理。

PROJECT SUMMARY Nucleotide excision repair (NER) is a DNA repair mechanism that recognizes and removes bulky, helix-distorting lesions from the nuclear genome. Key substrates for NER are lesions induced by ultraviolet (UV) radiation upon environmental exposure to sunlight and a subset of oxidative DNA lesions produced endogenously. This is dramatically illustrated by patients with xeroderma pigmentosum (XP), a disease caused by inherited defects in NER. XP patients have a 10,000-fold increased risk of skin cancer and early onset neurodegeneration. XP is heterogeneous, ranging from mild to profoundly debilitating. XP severity is proportional to the extent to which NER is disrupted. This suggests that subtle defects in NER, due to, for example, polymorphisms in NER genes, might modestly but significantly impact one’s risk of skin cancer. Since skin cancer affects 20% of Americans and is preventable (by avoiding environmental exposure to UV), identifying those at risk could have a tremendous impact on the health of Americans and healthcare costs. The greatest barrier to identifying those at risk is the lack of an assay to measure NER that is rapid, inexpensive and applicable to samples safely and easily collected from patients. NER occurs in a series of steps involving the recognition of a site of DNA damage, unwinding the DNA locally, excision of a single-stranded oligonucleotide containing the lesion, and templated DNA synthesis to fill the residual gap. NER is the only way that UV-induced photolesions are removed from the genome in human cells. Therefore, NER is measured by the detection and quantification of UV-induced DNA synthesis outside of the S-phase of the cell cycle, or unscheduled DNA synthesis (UDS). Historically, UDS measurement required the use of radioactively-labeled nucleosides and/or specialized equipment. We developed a method to measure NER that employs the thymidine analog 5-ethynyl-2'-deoxyuridine and Click-iT chemistry for fluorescent detection of UDS by flow cytometry. This can be applied to peripheral blood cells for rapid measurement of NER requiring minimally invasive sample collection. UDS in XP patients ranges from <10% to 50%. Nothing is known about the health implications of having a UDS between 50-100%, or how to define 100% NER capacity. This project aims to correct these gaps in knowledge through optimization of our functional assay and proof-of- concept pilot human studies. The assay will be applied to existing cohorts of patients seen at the University of Miami Skin Cancer Clinics, the NIH Undiagnosed Diseases Program or enrolled in the University of Maryland Amish Longevity Study, to interrogate associations between NER capacity and high risk of skin cancer, early onset neurodegeneration, and within family pedigrees, respectively. This project will yield an NER assay applicable to larger population studies aimed at testing associations between NER capacity, environmental exposures and disease risk, and begin to define “normal” NER capacity. The assay could have a significant impact on how risk of squamous cell or basal cell carcinoma of the skin, melanoma, lung or head and neck cancer, neurodegeneration, and resistance to cancer chemotherapy is identified and managed.