Defects in XRCC4 and KU80 differentially affect the joining of distal nonhomologous ends.
XRCC4-null mice have a more severe phenotype than KU80-null mice. Here, we address whether this difference in phenotype is connected to nonhomologous end-joining (NHEJ). We used intrachromosomal substrates to monitor NHEJ of two distal double-strand breaks (DSBs) targeted by I-SceI, in living cells. In xrcc4-defective XR-1 cells, a residual but significant end-joining process exists, which primarily uses microhomologies distal from the DSB. However, NHEJ efficiency was strongly reduced in xrcc4-defective XR-1 cells versus complemented cells, contrasting with KU-deficient xrs6 cells, which showed levels of end-joining similar to those of complemented cells. Nevertheless, sequence analysis of the repair junctions indicated that the accuracy of end-joining was strongly affected in both xrcc4-deficient and KU-deficient cells. More specifically, these data showed that the KU80/XRCC4 pathway is conservative and not intrinsically error-prone but can accommodate non-fully complementary ends at the cost of limited mutagenesis.
Guirouilh-Barbat
Josée
J
Commissariat à l'Energie Atomique, Unité Mixte de Recherche 217, Centre National de la Recherche Scientifique/Commissariat à l'Energie Atomique, Institut de Radiobiologie Cellulaire et Moléculaire, Fontenay aux Roses, France.
Rass
Emilie
E
Plo
Isabelle
I
Bertrand
Pascale
P
Lopez
Bernard S
BS
D000818:Animals; D034961:Antigens, Nuclear / Q000235:genetics* / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D005816:Genetic Complementation Test; D000072200:Ku Autoantigen; D051379:Mice; D008822:Mice, Transgenic; D008957:Models, Genetic; D010641:Phenotype
D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C511788:XRCC4 protein, mouse; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen