Measuring nucleotide excision repair in human populations

项目摘要 核苷酸切除修复（NER）是一种DNA修复机制，它识别并去除大体积的螺旋扭曲的DNA片段。 核基因组的损伤NER的关键底物是紫外线（UV）辐射诱导的损伤， 环境暴露于阳光和内源性产生的氧化DNA损伤的子集。这是 着色性干皮病（XP）的患者戏剧性地说明了这一点，XP是一种由遗传缺陷引起的疾病， NER。XP患者患皮肤癌和早发性神经退行性疾病的风险增加了10，000倍。XP是 异质性，从轻度到严重衰弱。XP严重性与以下程度成正比： Ner被打乱了。这表明，由于NER基因的多态性， 可能会适度但显著地影响一个人患皮肤癌的风险。因为20%的美国人患有皮肤癌 并且是可以预防的（通过避免环境暴露于紫外线），识别那些有风险的人可能会产生巨大的影响。 对美国人的健康和医疗费用的影响。识别风险人群的最大障碍是 缺乏一种快速、廉价且适用于安全和容易收集的样品的测定NER的方法 从病人身上。NER发生在一系列步骤中，包括识别DNA损伤位点，解旋DNA链， DNA局部，切除含有损伤的单链寡核苷酸，并模板化DNA合成 以填补剩余的空白。NER是从基因组中去除紫外线诱导的光损伤的唯一途径， 人体细胞因此，通过检测和定量UV诱导的DNA合成来测量NER 在细胞周期的S期之外，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/或专用设备。我们发明了一种方法 采用胸苷类似物5-乙炔基-2 '-脱氧尿苷和Click-iT化学进行荧光检测， 通过流式细胞术检测UDS。这可以应用于外周血细胞的NER的快速测量 需要最小侵入性的样本采集。XP患者的UDS范围为<10%至50%。一无所知 关于UDS在50- 100%之间的健康影响，或者如何定义100%的净入学率能力。这 该项目旨在通过优化我们的功能测定和证明来纠正这些知识差距， 概念试点人体研究。该试验将应用于在纽约大学就诊的现有患者队列。 迈阿密皮肤癌诊所、美国国立卫生研究院未诊断疾病项目或就读于马里兰州大学 Amish长寿研究，以询问NER能力与皮肤癌高风险之间的关联， 发病神经退行性变，并在家庭家系内，分别。该项目将产生NER测定 适用于旨在测试净入学率能力、环境 因此，我们必须评估暴露和疾病风险，并开始界定“正常”净减排能力。该测定可能具有显著的 对皮肤鳞状细胞癌或基底细胞癌、黑色素瘤、肺癌或头颈部癌风险的影响 癌症、神经变性和对癌症化疗的抗性被识别和管理。

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.