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The end-joining factor Ku acts in the end-resection of double strand break-free arrested replication forks

1 Dec 2017Nature Communications

DOI : 10.1038/s41467-017-02144-5

Authors

Ana Teixeira-Silva, Anissia Ait Saada, Julien Hardy, Ismail Iraqui, Marina Charlotte Nocente, Karine Fréon, Sarah A. E. Lambert

Abstract

Abstract

Replication requires homologous recombination (HR) to stabilize and restart terminally arrested forks. HR-mediated fork processing requires single stranded DNA (ssDNA) gaps and not necessarily double strand breaks. We used genetic and molecular assays to investigate fork-resection and restart at dysfunctional, unbroken forks in Schizosaccharomyces pombe. Here, we report that fork-resection is a two-step process regulated by the non-homologous end joining factor Ku. An initial resection mediated by MRN-Ctp1 removes Ku from terminally arrested forks, generating ~110 bp sized gaps obligatory for subsequent Exo1-mediated long-range resection and replication restart. The mere lack of Ku impacts the processing of arrested forks, leading to an extensive resection, a reduced recruitment of RPA and Rad51 and a slower fork-restart process. We propose that terminally arrested forks undergo fork reversal, providing a single DNA end for Ku binding. We uncover a role for Ku in regulating end-resection of unbroken forks and in fine-tuning HR-mediated replication restart.

Members

SARAH LAMBERT

Directeur de recherche CNRS