Hydrolytic and Free Radical Mediated DNA Damage

水解和自由基介导的 DNA 损伤

• 批准号: 7046891
• 负责人: Lawrence C Sowers
• 金额: $ 24.82万
• 依托单位: LOMA LINDA UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-01-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7046891
• 关键词: 5 methylcytosine; DNA binding protein; DNA damage; DNA methylation; DNA repair; N glycosidase; affinity chromatography; carcinogens; chemical kinetics; chromosome deletion; enzyme activity; free radicals; gene mutation; gene rearrangement; high performance liquid chromatography; human tissue; hydrolysis; mass spectrometry; mutagens; neoplastic cell; oxidation; pyrimidines; radiation related neoplasm /cancer; uracil analog

DESCRIPTION (provided by applicant): Life expectancy in the industrialized world has increased dramatically over the past century. A consequence of the increasing life expectancy is that diseases generally associated with aging, including cancer and neurodegeneration, will affect more individuals. The genetic basis of cancer is attributed to a series of DNA damage events that can include point mutations, chromosome rearrangements and loss, and epigenetic changes such as altered DNA cytosine methylation patterns. DNA is known to be damaged by exogenous chemicals and radiation. However, cellular DNA is continuously oxidized, hydrolyzed and methylated even in the absence of exogenous agents. It is estimated that the number of endogenous DNA lesions formed is on the order of tens of thousands per cell per day. In response to DNA damage, cells have a complex network of repair pathways that recognize, excise and rebuild the damaged sites. Defects in DNA repair pathways are known to increase substantially the incidence of cancer. An increase in human life span over which DNA can be damaged, coupled with an increase in age-associated diseases including cancer, highlight the need to understand how DNA can be damaged and how repair pathways function.The focus of our efforts on this project has been five pyrimidine oxidation products that can result from radiation, carcinogen exposure and endogenous DNA damage. These modified pyrimidines include 5-hydroxymethyluracil (HmU), 5-formyluracil (FoU), 5-hydroxymethylcytosine (HmC), 5-hydroxyuracil (HoU) and 5-hydroxycytosine (HoC). In the previous period of funding, we discovered several important chemical properties of these modified pyrimidines, and we have discovered several new and significant properties of damaged base recognition by cellular repair enzymes.In the current proposal, we describe a series of experiments to follow up on these findings. The specific aims of the current proposal are 1) to identify the proteins responsible for the repair of HmU and to further understand cellular responses to the repair of exogenous HmU, 2) to investigate biochemical consequences of the oxidation of 5- methylcytosine (5mC) including the impact of HmC on DNA-protein interactions and to further investigate a potential novel biochemical pathway through which methylation patterns might be altered, 3) to identify the general mechanisms by which damaged pyrimidines are recognized by DNA repair glycosylases, and 4) to develop a general strategy for the identification and characterization of as yet unidentified DNA repair proteins. The results of the proposed studies should shed significant new light on our understanding of DNA damage and its repair. With these added insights, we may learn how to reduce DNA damage that leads to human diseases including cancer, as well as understand how to exploit defects or alterations in DNA repair pathways for the development of more selective chemotherapy.

描述（由申请人提供）：在过去的一个世纪中，工业化世界的预期寿命急剧增加。预期寿命增加的结果是，通常与衰老有关的疾病（包括癌症和神经变性）会影响更多的人。癌症的遗传基础归因于一系列DNA损伤事件，这些事件可能包括点突变，染色体重排和丢失以及表观遗传变化，例如改变的DNA胞嘧啶甲基化模式。已知DNA被外源化学物质和辐射受损。然而，即使在没有外源性药物的情况下，细胞DNA也被连续氧化，水解和甲基化。据估计，形成的内源性DNA病变的数量是每个细胞每天数万个。为了应对DNA损伤，细胞具有复杂的修复途径网络，该网络识别，切除和重建受损部位。已知DNA修复途径中的缺陷大大增加了癌症的发生率。人类寿命跨度的增加可能会损害DNA，再加上包括癌症在内的年龄相关疾病的增加，突出了需要了解如何损坏DNA以及如何损害DNA的需要。我们对该项目的努力的重点是五种嘧啶氧化产物，这些产品可能是由于辐射，癌变，癌变，癌变和内源性DNA损害所致。这些修饰的嘧啶包括5-羟基甲基尿酸胺（HMU），5-甲基尿酸胺（FOU），5-羟基甲基胞嘧啶（HMC），5-羟基罗拉西尔（HO）（HO）和5-羟基胞丝（Hoc）。在上一期的资金阶段，我们发现了这些修饰的嘧啶的几种重要化学特性，并且我们发现了通过细胞修复酶受损的基础识别的几种新的且重要的特性。在当前的建议中，我们描述了一系列实验，以跟进这些发现。当前建议的具体目的是1）确定负责修复HMU的蛋白质，并进一步了解细胞对修复外源性HMU修复的反应，2）研究5-甲基胞嘧啶（5MC）氧化的生物化学后果，包括HMC对DNA互动的影响，以进一步研究途径，以进一步研究途径的途径。为了确定DNA修复糖基酶识别受损的嘧啶的一般机制，以及4）制定一般策略，以鉴定和表征AS尚未确定的DNA修复蛋白。拟议的研究的结果应为我们对DNA损伤及其修复的理解提供重大启示。借助这些增加的见解，我们可以学习如何减少导致包括癌症在内的人类疾病的DNA损伤，并了解如何利用DNA修复途径中的缺陷或改变，以开发更具选择性的化学疗法。