Defects in XRCC4 and KU80 differentially affect the joining of distal nonhomologous ends
- 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, Direction des Sciences du Vivant, 18 Route du Panorama, BP06, 92265 Fontenay aux Roses, Cedex, France
-
Edited by Frederick W. Alt, Harvard Medical School, Boston, MA, and approved November 6, 2007 (received for review September 9, 2007)
Abstract
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.
Footnotes
- *To whom correspondence may be addressed. E-mail: pascale.bertrand{at}cea.fr or bernard.lopez{at}cea.fr
-
Author contributions: J.G.-B. and E.R. contributed equally to this work; P.B. and B.S.L. designed research; J.G.-B., E.R., I.P., and P.B. performed research; J.G.-B., E.R., I.P., P.B., and B.S.L. analyzed data; and J.G.-B., E.R., P.B., and B.S.L. wrote the paper.
-
The authors declare no conflict of interest.
-
This article is a PNAS Direct Submission.
-
Freely available online through the PNAS open access option.
- © 2007 by The National Academy of Sciences of the USA
