ATM antagonizes NHEJ proteins assembly and DNA-ends synapsis at single-ended DNA double strand breaks

• Published in: Nucleic acids research Vol. 48; no. 17; pp. 9710 - 9723
• Main Authors: Britton, Sébastien, Chanut, Pauline, Delteil, Christine, Barboule, Nadia, Frit, Philippe, Calsou, Patrick
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 25.09.2020
• Subjects: Ataxia Telangiectasia Mutated Proteins - genetics; Ataxia Telangiectasia Mutated Proteins - metabolism; Camptothecin - pharmacology; Cell Line; DNA Breaks, Double-Stranded; DNA End-Joining Repair - drug effects; DNA End-Joining Repair - physiology; DNA Ligase ATP - genetics; DNA Ligase ATP - metabolism; DNA, Single-Stranded; DNA-Activated Protein Kinase - genetics; DNA-Activated Protein Kinase - metabolism; Genetics; Genome Integrity, Repair and; Humans; Ku Autoantigen - genetics; Ku Autoantigen - metabolism; Life Sciences; MRE11 Homologue Protein - genetics; MRE11 Homologue Protein - metabolism; Phosphorylation; Topoisomerase I Inhibitors - pharmacology
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkaa723

Abstract Two DNA repair pathways operate at DNA double strand breaks (DSBs): non-homologous end-joining (NHEJ), that requires two adjacent DNA ends for ligation, and homologous recombination (HR), that resects one DNA strand for invasion of a homologous duplex. Faithful repair of replicative single-ended DSBs (seDSBs) is mediated by HR, due to the lack of a second DNA end for end-joining. ATM stimulates resection at such breaks through multiple mechanisms including CtIP phosphorylation, which also promotes removal of the DNA-ends sensor and NHEJ protein Ku. Here, using a new method for imaging the recruitment of the Ku partner DNA-PKcs at DSBs, we uncover an unanticipated role of ATM in removing DNA-PKcs from seDSBs in human cells. Phosphorylation of DNA-PKcs on the ABCDE cluster is necessary not only for DNA-PKcs clearance but also for the subsequent MRE11/CtIP-dependent release of Ku from these breaks. We propose that at seDSBs, ATM activity is necessary for the release of both Ku and DNA-PKcs components of the NHEJ apparatus, and thereby prevents subsequent aberrant interactions between seDSBs accompanied by DNA-PKcs autophosphorylation and detrimental commitment to Lig4-dependent end-joining.