DNA Lesions as Endogenous Topoisomerase Poisons

DNA 损伤作为内源性拓扑异构酶毒物

• 批准号: 7050934
• 负责人: NEIL OSHEROFF
• 金额: $ 28.78万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-05-01 至 2009-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7050934
• 关键词: DNA binding protein; DNA damage; DNA repair; DNA replication; DNA topoisomerases; Drosophilidae; Saccharomyces cerevisiae; adduct; antineoplastics; cell death; chemical binding; chemical cleavage; cytotoxicity; enzyme activity; enzyme induction /repression; enzyme mechanism; genetic recombination; mutant; pharmacokinetics; tissue /cell culture

DESCRIPTION (provided by applicant): Topoisomerase II is an essential enzyme that relaxes DNA and removes knots and tangles from the genetic material by passing an intact double helix through a transient double-stranded break that it generates in a separate DNA segment. However, since topoisomerase II must create double-stranded DNA breaks in order to carry out its catalytic functions, the enzyme also poses an intrinsic threat to genomic integrity. Beyond its critical cellular functions, topoisomerase II is the primary target for some of the most active anticancer drugs currently in clinical use. These drugs act by increasing levels of covalent topoisomerase ll-cleaved DNA complexes that are normal, but fleeting, intermediates in the catalytic cycle of the enzyme. When the resulting enzyme-associated DNA breaks are present in high concentrations, they generate mutations, chromosomal translocations, and trigger cell death pathways. Anticancer drugs targeted to the type II enzyme are referred to as topoisomerase II poisons because they convert this essential enzyme to a potent physiological toxin that fragments the genome. Although topoisomerase II is one of the most important targets for cancer treatment, there is compelling evidence that DNA breaks created by the enzyme also trigger specific types of leukemia. This suggests that topoisomerase ll-targeted drugs may represent exogenous counterparts of cellular components that induce DNA recombination, mutagenesis, or cell death pathways. Previous studies (many from the applicant's lab) indicate that a basic sites, the most commonly formed lesion in DNA, and other physiological DNA lesions stimulate topoisomerase ll-mediated DNA cleavage with a potency that is considerably higher than that of the widely prescribed anticancer drug etoposide. Thus, the ultimate goals of this proposal are to further define interactions between topoisomerase II and DNA damage and to determine whether DNA lesions function in cells as endogenous topoisomerase II poisons. The models for this study will be human topoisomerase ll alpha and beta, and cultured mammalian cell lines. RELEVANCE: Topoisomerase II is the target for some of the most important anticancer drugs in clinical use. However, there is also evidence that the enzyme triggers chromosomal breaks that trigger leukemia. The current proposal tests the hypothesis that DNA lesions act as endogenous counterparts of anticancer drugs and may be involved in initiating topoisomerase ll-mediated leukemic chromosomal translocations.

描述（由申请人提供）：拓扑异构酶 II 是一种必需的酶，它可以使完整的双螺旋穿过在单独的 DNA 片段中产生的瞬时双链断裂，从而松弛 DNA 并消除遗传物质中的结和缠结。然而，由于拓扑异构酶 II 必须产生双链 DNA 断裂才能发挥其催化功能，因此该酶也对基因组完整性构成了内在威胁。除了其关键的细胞功能之外，拓扑异构酶 II 是目前临床使用的一些最活跃的抗癌药物的主要靶点。这些药物通过增加共价拓扑异构酶 II 切割的 DNA 复合物的水平来发挥作用，这些 DNA 复合物是酶催化循环中正常但短暂的中间体。当产生的酶相关 DNA 断裂以高浓度存在时，它们会产生突变、染色体易位并触发细胞死亡途径。针对 II 型酶的抗癌药物被称为拓扑异构酶 II 毒物，因为它们会将这种必需酶转化为强效生理毒素，使基因组片段化。尽管拓扑异构酶 II 是癌症治疗最重要的靶标之一，但有令人信服的证据表明，该酶产生的 DNA 断裂也会引发特定类型的白血病。这表明拓扑异构酶 II 靶向药物可能代表诱导 DNA 重组、诱变或细胞死亡途径的细胞成分的外源对应物。先前的研究（许多来自申请人的实验室）表明，DNA中最常见的损伤和其他生理性DNA损伤的基本位点刺激拓扑异构酶II介导的DNA切割，其效力远远高于广泛使用的抗癌药物依托泊苷。因此，该提案的最终目标是进一步定义拓扑异构酶 II 和 DNA 损伤之间的相互作用，并确定 DNA 损伤是否作为内源性拓扑异构酶 II 毒物在细胞中发挥作用。本研究的模型将是人类拓扑异构酶 II α 和 β 以及培养的哺乳动物细胞系。相关性：拓扑异构酶 II 是临床使用中一些最重要的抗癌药物的靶点。然而，也有证据表明这种酶会引发染色体断裂，从而引发白血病。目前的提议测试了这样的假设：DNA 损伤充当抗癌药物的内源性对应物，并且可能参与启动拓扑异构酶 II 介导的白血病染色体易位。