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Ku70 Corrupts DNA Repair in the Absence of the Fanconi Anemia Pathway

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Science  09 Jul 2010:
Vol. 329, Issue 5988, pp. 219-223
DOI: 10.1126/science.1192277

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Righting Repair Pathways

The genetic disease Fanconi anemia (FA) results from mutations in a series of genes involved in a DNA repair pathway that helps process the damage caused by erroneous chemical cross-links between the two strands of the DNA double helix. The double-stranded breaks in DNA that arise from such cross-links can be repaired in an error-free manner or through an error-prone repair pathway. Pace et al. (p. 219, published online 10 June) show that the FA pathway can drive repair through the error-free pathway. The FA FANCC gene shows a genetic interaction with a component of the error-prone repair pathway, Ku70, inhibiting its action and thereby promoting the error-free pathway.

Abstract

A conserved DNA repair response is defective in the human genetic illness Fanconi anemia (FA). Mutation of some FA genes impairs homologous recombination and error-prone DNA repair, rendering FA cells sensitive to DNA cross-linking agents. We found a genetic interaction between the FA gene FANCC and the nonhomologous end joining (NHEJ) factor Ku70. Disruption of both FANCC and Ku70 suppresses sensitivity to cross-linking agents, diminishes chromosome breaks, and reverses defective homologous recombination. Ku70 binds directly to free DNA ends, committing them to NHEJ repair. We show that purified FANCD2, a downstream effector of the FA pathway, might antagonize Ku70 activity by modifying such DNA substrates. These results reveal a function for the FA pathway in processing DNA ends, thereby diverting double-strand break repair away from abortive NHEJ and toward homologous recombination.

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