Stepwise activation of the ATR signaling pathway upon increasing replication stress impacts fragile site integrity

Stéphane Koundrioukoff; Sandra Carignon; Hervé Técher; Anne Letessier; Olivier Brison; Michelle Debatisse

doi:10.1371/journal.pgen.1003643

Stepwise activation of the ATR signaling pathway upon increasing replication stress impacts fragile site integrity

PLoS Genet. 2013;9(7):e1003643. doi: 10.1371/journal.pgen.1003643. Epub 2013 Jul 18.

Authors

Stéphane Koundrioukoff¹, Sandra Carignon, Hervé Técher, Anne Letessier, Olivier Brison, Michelle Debatisse

Affiliation

¹ Institut Curie UMR 3244, Université Pierre et Marie Curie (Paris 06), CNRS Paris, France.

Abstract

Breaks at common fragile sites (CFS) are a recognized source of genome instability in pre-neoplastic lesions, but how such checkpoint-proficient cells escape surveillance and continue cycling is unknown. Here we show, in lymphocytes and fibroblasts, that moderate replication stresses like those inducing breaks at CFSs trigger chromatin loading of sensors and mediators of the ATR pathway but fail to activate Chk1 or p53. Consistently, we found that cells depleted of ATR, but not of Chk1, accumulate single-stranded DNA upon Mre11-dependent resection of collapsed forks. Partial activation of the pathway under moderate stress thus takes steps against fork disassembly but tolerates S-phase progression and mitotic onset. We show that fork protection by ATR is crucial to CFS integrity, specifically in the cell type where a given site displays paucity in backup replication origins. Tolerance to mitotic entry with under-replicated CFSs therefore results in chromosome breaks, providing a pool of cells committed to further instability.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Ataxia Telangiectasia Mutated Proteins / genetics
Ataxia Telangiectasia Mutated Proteins / metabolism
Cell Cycle Proteins / genetics
Cell Cycle Proteins / metabolism
Cell Line
Checkpoint Kinase 1
Chromatin / genetics*
Chromosome Fragile Sites / genetics*
DNA Replication / genetics
Fibroblasts / cytology
Fibroblasts / metabolism
Genomic Instability / genetics*
Humans
Lymphocytes / cytology
Lymphocytes / metabolism
Mitosis / genetics
Protein Kinases / genetics
Replication Origin / genetics
Signal Transduction
Tumor Suppressor Protein p53 / genetics

Substances

Cell Cycle Proteins
Chromatin
TP53 protein, human
Tumor Suppressor Protein p53
Protein Kinases
ATR protein, human
Ataxia Telangiectasia Mutated Proteins
CHEK1 protein, human
Checkpoint Kinase 1

Grants and funding

MD's team was supported by INCa (Institut National du Cancer) (2009-1-PLBIO-10-IC-1), the Agence Nationale de la Recherche (ANR-09-GENO-000/repinsCFS), and by the Association pour la Recherche sur le Cancer (ARC Subvention Libre n° SL220100601348; Equipements mi-lourds n° 8514). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.