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Defects in XRCC4 and KU80 Differentially Affect the Joining of Distal Nonhomologous Ends
Josée Guirouilh-Barbat, Emilie Rass, Isabelle Plo, Pascale Bertrand and Bernard S. Lopez
Proceedings of the National Academy of Sciences of the United States of America
Vol. 104, No. 52 (Dec. 26, 2007), pp. 20902-20907
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25450999
Page Count: 6
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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.
Proceedings of the National Academy of Sciences of the United States of America © 2007 National Academy of Sciences