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 γ-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.

DNA double-strand break, Homologous recombination, Ku80, Nonhomologous end-joining, Rad54
dx.doi.org/10.1101/gad.1209204, hdl.handle.net/1765/67858
Genes & Development
Department of Molecular Genetics

Couëdel, C, Mills, K.D, Barchi, M, Shen, L, Olshen, A, Johnson, R.D, … Jasin, M. (2004). Collaboration of homologous recombination and nonhomologous end-joining factors for the survival and integrity of mice and cells. Genes & Development, 18(11), 1293–1304. doi:10.1101/gad.1209204