title: Association of XRCC1 and tyrosyl DNA phosphodiesterase (Tdp1) for the repair of topoisomerase I-mediated DNA lesions.
abstract: 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.
mesh_terms: D000818:Animals; D016466:CHO Cells; D002166:Camptothecin / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000502:physiology*; D004261:DNA Replication; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005816:Genetic Complementation Test; D008968:Molecular Conformation; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism* / Q000502:physiology; D011116:Polynucleotide 5'-Hydroxyl-Kinase / Q000378:metabolism; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D000076105:X-ray Repair Cross Complementing Protein 1; D011116:Polynucleotide 5'-Hydroxyl-Kinase; D010727:Phosphoric Diester Hydrolases; C122147:tyrosyl-DNA phosphodiesterase; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin