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ATR and Chk1 Suppress a Caspase-3–Dependent Apoptotic Response Following DNA Replication Stress

Myers, K., Gagou, M.E., Zuazua-Villar, P., Rodriguez, R., Meuth, M. and Cohen-Fix, O. (2009) ATR and Chk1 Suppress a Caspase-3–Dependent Apoptotic Response Following DNA Replication Stress. PLoS Genetics, 5 (1). e1000324. ISSN 1553-7404

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Abstract

The related PIK-like kinases Ataxia-Telangiectasia Mutated (ATM) and ATM- and Rad3-related (ATR) play major roles in the regulation of cellular responses to DNA damage or replication stress. The pro-apoptotic role of ATM and p53 in response to ionizing radiation (IR) has been widely investigated. Much less is known about the control of apoptosis following DNA replication stress. Recent work indicates that Chk1, the downstream phosphorylation target of ATR, protects cells from apoptosis induced by DNA replication inhibitors as well as IR. The aim of the work reported here was to determine the roles of ATM- and ATR-protein kinase cascades in the control of apoptosis following replication stress and the relationship between Chk1-suppressed apoptotic pathways responding to replication stress or IR. ATM and ATR/Chk1 signalling pathways were manipulated using siRNA-mediated depletions or specific inhibitors in two tumour cell lines or fibroblasts derived from patients with inherited mutations. We show that depletion of ATM or its downstream phosphorylation targets, NBS1 and BID, has relatively little effect on apoptosis induced by DNA replication inhibitors, while ATR or Chk1 depletion strongly enhances cell death induced by such agents in all cells tested. Furthermore, early events occurring after the disruption of DNA replication (accumulation of RPA foci and RPA34 hyperphosphorylation) in ATR- or Chk1-depleted cells committed to apoptosis are not detected in ATM-depleted cells. Unlike the Chk1-suppressed pathway responding to IR, the replication stress-triggered apoptotic pathway did not require ATM and is characterized by activation of caspase 3 in both p53-proficient and -deficient cells. Taken together, our results show that the ATR-Chk1 signalling pathway plays a major role in the regulation of death in response to DNA replication stress and that the Chk1-suppressed pathway protecting cells from replication stress is clearly distinguishable from that protecting cells from IR.

Item Type: Article
Copyright, Publisher and Additional Information: © 2009 Myers et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > School of Medicine (Sheffield)
Depositing User: Sheffield Import
Date Deposited: 30 Oct 2009 15:10
Last Modified: 15 Sep 2014 04:09
Published Version: http://dx.doi.org/10.1371/journal.pgen.1000324
Status: Published
Publisher: Public Library of Science
Refereed: Yes
Identification Number: doi: 10.1371/journal.pgen.1000324
URI: http://eprints.whiterose.ac.uk/id/eprint/10025

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