Association of XRCC1 and tyrosyl DNA phosphodiesterase (Tdp1) for the repair of topoisomerase I-mediated DNA lesions

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • CHO Cells
  • Camptothecin / pharmacology
  • Cell Survival / drug effects
  • Cricetinae
  • DNA Damage / genetics
  • DNA Repair / physiology*
  • DNA Replication
  • DNA Topoisomerases, Type I / metabolism*
  • DNA, Single-Stranded / genetics
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology*
  • Genetic Complementation Test
  • Molecular Conformation
  • Phosphoric Diester Hydrolases / metabolism*
  • Phosphoric Diester Hydrolases / physiology
  • Polynucleotide 5'-Hydroxyl-Kinase / metabolism
  • X-ray Repair Cross Complementing Protein 1


  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • X-ray Repair Cross Complementing Protein 1
  • Polynucleotide 5'-Hydroxyl-Kinase
  • Phosphoric Diester Hydrolases
  • tyrosyl-DNA phosphodiesterase
  • DNA Topoisomerases, Type I
  • Camptothecin