Plo Isabelle, Liao Zhi Yong, Barceló Juana M, Kohlhagen Glenda, Caldecott Keith W, Weinfeld Michael, Pommier Yves
Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institute of Health, Building 37, Room 5068, Bethesda, MD, USA.
DNA Repair (Amst). 2003 Oct 7;2(10):1087-100. doi: 10.1016/s1568-7864(03)00116-2.
DNA topoisomerase I (Top1) is converted into a cellular poison by camptothecin (CPT) and various endogenous and exogenous DNA lesions. In this study, we used X-ray repair complementation group 1 (XRCC1)-deficient and XRCC1-complemented EM9 cells to investigate the mechanism by which XRCC1 affects the cellular responses to Top1 cleavage complexes induced by CPT. XRCC1 complementation enhanced survival to CPT-induced DNA lesions produced independently of DNA replication. CPT-induced comparable levels of Top1 cleavage complexes (single-strand break (SSB) and DNA-protein cross-links (DPC)) in both XRCC1-deficient and XRCC1-complemented cells. However, XRCC1-complemented cells repaired Top1-induced DNA breaks faster than XRCC1-deficient cells, and exhibited enhanced tyrosyl DNA phosphodiesterase (Tdp1) and polynucleotide kinase phosphatase (PNKP) activities. XRCC1 immunoprecipitates contained Tdp1 polypeptide, and both Tdp1 and PNKP activities, indicating a functional connection between the XRCC1 single-strand break repair pathway and the repair of Top1 covalent complexes by Tdp1 and PNKP.
DNA拓扑异构酶I（Top1）会被喜树碱（CPT）以及各种内源性和外源性DNA损伤转化为一种细胞毒素。在本研究中，我们使用了X射线修复互补组1（XRCC1）缺陷型和XRCC1互补型EM9细胞，来研究XRCC1影响细胞对CPT诱导的Top1切割复合物反应的机制。XRCC1互补增强了细胞对CPT诱导的与DNA复制无关的DNA损伤的存活能力。CPT在XRCC1缺陷型细胞和XRCC1互补型细胞中诱导产生的Top1切割复合物（单链断裂（SSB）和DNA-蛋白质交联（DPC））水平相当。然而，XRCC1互补型细胞比XRCC1缺陷型细胞更快地修复Top1诱导的DNA断裂，并且表现出增强的酪氨酰DNA磷酸二酯酶（Tdp1）和多核苷酸激酶磷酸酶（PNKP）活性。XRCC1免疫沉淀物含有Tdp1多肽以及Tdp1和PNKP活性，这表明XRCC1单链断裂修复途径与Tdp1和PNKP对Top1共价复合物的修复之间存在功能联系。
