Parp-1 protects homologous recombination from interference by Ku and Ligase IV in vertebrate cells

EMBO J. 2006 Mar 22;25(6):1305-14. doi: 10.1038/sj.emboj.7601015. Epub 2006 Feb 23.


Parp-1 and Parp-2 are activated by DNA breaks and have been implicated in the repair of DNA single-strand breaks (SSB). Their involvement in double-strand break (DSB) repair mediated by homologous recombination (HR) or nonhomologous end joining (NHEJ) remains unclear. We addressed this question using chicken DT40 cells, which have the advantage of carrying only a PARP-1 gene but not a PARP-2 gene. We found that PARP-1(-/-) DT40 mutants show reduced levels of HR and are sensitive to various DSB-inducing genotoxic agents. Surprisingly, this phenotype was strictly dependent on the presence of Ku, a DSB-binding factor that mediates NHEJ. PARP-1/KU70 double mutants were proficient in the execution of HR and displayed elevated resistance to DSB-inducing drugs. Moreover, we found deletion of Ligase IV, another NHEJ gene, suppressed the camptothecin of PARP-1(-/-) cells. Our results suggest a new critical function for Parp in minimizing the suppressive effects of Ku and the NHEJ pathway on HR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, Nuclear / pharmacology*
  • B-Lymphocytes / drug effects*
  • B-Lymphocytes / metabolism
  • Camptothecin / pharmacology
  • Cell Line
  • Chickens
  • DNA / chemistry
  • DNA / genetics
  • DNA / metabolism
  • DNA Damage / drug effects
  • DNA Ligase ATP
  • DNA Ligases / deficiency*
  • DNA-Binding Proteins / pharmacology*
  • Homozygote
  • Ku Autoantigen
  • Mutation
  • Phenotype
  • Poly(ADP-ribose) Polymerases / physiology*
  • Recombination, Genetic*
  • Transfection


  • Antigens, Nuclear
  • DNA-Binding Proteins
  • DNA
  • Poly(ADP-ribose) Polymerases
  • Ku Autoantigen
  • DNA Ligases
  • DNA Ligase ATP
  • Camptothecin