Mechanisms for Transcription-Coupled Repair in Human Cells

人类细胞转录偶联修复机制

• 批准号: 7317981
• 负责人: Priscilla K. Cooper
• 金额: $ 39.51万
• 依托单位: UNIVERSITY OF CALIF-LAWRENC BERKELEY LAB
• 依托单位国家: 美国
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-05-19 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7317981
• 关键词: Address; Affect; Appearance; Base Excision Repairs; Biochemical; Biological Testing; Carcinogens; Cells; Chemicals; Clinical; Cockayne Syndrome; Complex; Condition; Coupled; DNA Damage; DNA Excision Repair Protein ERCC-6; DNA Repair; DNA lesion; DNA repair protein; DNA-Directed RNA Polymerase; Defect; Dependence; Development; Disease; Disease Pathway; ERCC5 gene; Excision; Face; Figs - dietary; Genes; Genetic Transcription; Genome; Genomics; Growth; Health; Hereditary Disease; Human; In Vitro; Investigation; Ionizing radiation; Knock-out; Lesion; Life; Link; Maintenance; Malignant Neoplasms; Metabolism; Modeling; Molecular; Mus; Mutation; N-terminal; Neurologic; Nuclear Extract; Nuclear Matrix; Nucleotide Excision Repair; Pathway interactions; Patients; Phenotype; Play; Polymerase; Predisposition; Premature aging syndrome; Prevention; Process; Proteins; RNA Polymerase II; Radiation; Reactive Oxygen Species; Repair Complex; Reporting; Research; Role; Surgical incisions; Syndrome; System; Testing; Transcription-Coupled Repair; UV sensitive syndrome; Ultraviolet Rays; XPGC protein; Xeroderma Pigmentosum; base; carcinogenesis; developmental disease; disease phenotype; environmental agent; human disease; mutant; nervous system disorder; oxidative DNA damage; postnatal; programs; reconstitution; repair enzyme; repaired; response; transcription factor TFIIH; ultraviolet damage

DESCRIPTION (provided by applicant): DNA repair-defective genetic diseases result in marked cancer predisposition, and many also produce developmental, neurological, or immunological abnormalities, and/or premature aging. The implied requirements for DNA repair in avoidance of carcinogenesis and in normal development are proposed to be related to DNA damage from reactive oxygen species generated by the cellular metabolism as well as by environmental agents including ionizing radiation. The broad objective of this project is to elucidate both the molecular mechanisms for transcription-coupled repair (TCR) and the processing of oxidative DNA damage in human cells, in order to better understand the human health effects of genetic defects in these processes. The approach involves comprehensive characterization of the multiple critical functions of the highly pleiotropic human DNA repair protein XPG, which plays an integrating role in multiple DNA repair processes. The enzymatic activity of XPG is strictly required in nucleotide excision repair (NER) for making the first incision in removal of UV and bulky carcinogen damage. Defects in this function result in the highly cancer-prone disease xeroderma pigmentosum (XP). XPG also has important non-enzymatic roles in base excision repair (BER) of oxidative DNA damage through coordination and stimulation of early steps in lesion removal and in transcription-coupled repair (TCR) - the preferential repair of lesions of transcribed strands of active genes - through interaction with stalled RNA polymerase and other TCR proteins. Mutations in XPG that inactivate these non-enzymatic functions result in the profound developmental and neurological disorder Cockayne syndrome (CS). The hypotheses to be tested are that (a) XPG together with CSB has a critical role in the early steps of TCR that is important both for responses to environmental DNA damage and for maintenance of genome function under normal growth conditions, and that (b) XPG additionally has biologically important roles in global BER of oxidative damage. Both functions are hypothesized to be important in prevention of radiation- and chemical-induced carcinogenesis involving oxidative DNA damage as well as for normal postnatal development. It is proposed (1) to characterize the roles of XPG and CSB in repair of oxidative DNA damage and determine whether global or transcription-coupled mechanisms, or both, are involved; (2) to investigate the assembly of TCR complexes in cells in response to oxidative DNA damage; (3) to investigate the effect of a CS-related mutant fragment of the TCR protein CSB and its interaction with XPG on cellular responses to oxidative DNA damage and the CS phenotype; and (4) to define early steps in TCR and investigate a proposed remodeling of stalled RNA polymerase II by TCR proteins to enable repair. These studies address key mechanisms for maintaining genomic integrity and function in the face of cellular and environmental oxidative DNA damage.

描述（由申请人提供）：DNA 修复缺陷型遗传病会导致明显的癌症倾向，许多还会导致发育、神经或免疫异常和/或过早衰老。为避免致癌和正常发育，DNA 修复的隐含要求被认为与细胞代谢产生的活性氧以及包括电离辐射在内的环境因素造成的 DNA 损伤有关。该项目的总体目标是阐明人类细胞中转录偶联修复（TCR）和氧化DNA损伤处理的分子机制，以便更好地了解这些过程中遗传缺陷对人类健康的影响。该方法涉及高度多效性人类 DNA 修复蛋白 XPG 的多种关键功能的全面表征，XPG 在多种 DNA 修复过程中发挥着整合作用。 XPG 的酶活性在核苷酸切除修复 (NER) 中是严格要求的，以便在去除紫外线和大量致癌物损伤时进行第一个切口。该功能的缺陷会导致极易罹患癌症的着色性干皮病 (XP)。 XPG 还通过协调和刺激损伤去除和转录偶联修复 (TCR) 的早期步骤（活性基因转录链损伤的优先修复），在氧化 DNA 损伤的碱基切除修复 (BER) 中发挥重要的非酶作用。 - 通过与停滞的 RNA 聚合酶和其他 TCR 蛋白相互作用。 XPG 突变使这些非酶功能失活，导致严重的发育和神经系统疾病科凯恩综合征 (CS)。要测试的假设是 (a) XPG 与 CSB 一起在 TCR 的早期步骤中发挥关键作用，这对于响应环境 DNA 损伤和正常生长条件下维持基因组功能都很重要，并且 (b) XPG 在氧化损伤的全局 BER 中还具有重要的生物学作用。据推测，这两种功能对于预防辐射和化学诱发的涉及氧化 DNA 损伤的致癌作用以及正常的产后发育都很重要。建议 (1) 表征 XPG 和 CSB 在修复氧化 DNA 损伤中的作用，并确定是否涉及全局机制或转录偶联机制，或两者都参与； (2) 研究细胞内TCR复合物的组装以响应DNA氧化损伤； (3) 研究TCR蛋白CSB的CS相关突变片段及其与XPG的相互作用对细胞对氧化DNA损伤的反应和CS表型的影响； (4) 定义 TCR 的早期步骤，并研究通过 TCR 蛋白对停滞的 RNA 聚合酶 II 进行重构以实现修复的提议。这些研究探讨了在细胞和环境氧化 DNA 损伤时维持基因组完整性和功能的关键机制。