Collaboration of homologous recombination and nonhomologous end-joining factors for the survival and integrity of mice and cells

Genes Dev. 2004 Jun 1;18(11):1293-304. doi: 10.1101/gad.1209204.


Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are mechanistically distinct DNA repair pathways that contribute substantially to double-strand break (DSB) repair in mammalian cells. We have combined mutations in factors from both repair pathways, the HR protein Rad54 and the DNA-end-binding factor Ku80, which has a role in NHEJ. Rad54(-/-)Ku80(-/-) mice were severely compromised in their survival, such that fewer double mutants were born than expected, and only a small proportion of those born reached adulthood. However, double-mutant mice died at lower frequency from tumors than Ku80 single mutant mice, likely as a result of rapid demise at a young age from other causes. When challenged with an exogenous DNA damaging agent, ionizing radiation, double-mutant mice were exquisitely sensitive to low doses. Tissues and cells from double-mutant mice also showed indications of spontaneous DNA damage. Testes from some Rad54(-/-)Ku80(-/-) mice displayed enhanced apoptosis and reduced sperm production, and embryonic fibroblasts from Rad54(-/-)Ku80(-/-) animals accumulated foci of gamma-H2AX, a marker for DSBs. The substantially increased DNA damage response in the double mutants implies a cooperation of the two DSB repair pathways for survival and genomic integrity in the animal.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aging / genetics
  • Animals
  • Animals, Newborn
  • Antigens, Nuclear / genetics
  • Antigens, Nuclear / metabolism*
  • Brain / pathology
  • Cells, Cultured
  • DNA Damage / genetics
  • DNA Helicases
  • DNA Repair / physiology*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Female
  • Fetal Death / genetics
  • Fibroblasts / physiology
  • Fibroblasts / radiation effects
  • Histones / genetics
  • Histones / metabolism
  • Ku Autoantigen
  • Male
  • Mice
  • Mice, Mutant Strains
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Radiation, Ionizing
  • Recombination, Genetic*
  • Survival Rate
  • Testis / pathology


  • Antigens, Nuclear
  • DNA-Binding Proteins
  • Histones
  • Nuclear Proteins
  • gamma-H2AX protein, mouse
  • DNA Helicases
  • Rad54l protein, mouse
  • Xrcc6 protein, mouse
  • Ku Autoantigen