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A short G1 phase imposes constitutive replication stress and fork remodelling in mouse embryonic stem cells


Ahuja, Akshay K; Jodkowska, Karolina; Teloni, Federico; Bizard, Anna H; Zellweger, Ralph; Herrador, Raquel; Ortega, Sagrario; Hickson, Ian D; Altmeyer, Matthias; Mendez, Juan; Lopes, Massimo (2016). A short G1 phase imposes constitutive replication stress and fork remodelling in mouse embryonic stem cells. Nature Communications, 7:10660-10671.

Abstract

Embryonic stem cells (ESCs) represent a transient biological state, where pluripotency is coupled with fast proliferation. ESCs display a constitutively active DNA damage response (DDR), but its molecular determinants have remained elusive. Here we show in cultured ESCs and mouse embryos that H2AX phosphorylation is dependent on Ataxia telangiectasia and Rad3 related (ATR) and is associated with chromatin loading of the ssDNA-binding proteins RPA and RAD51. Single-molecule analysis of replication intermediates reveals massive ssDNA gap accumulation, reduced fork speed and frequent fork reversal. All these marks of replication stress do not impair the mitotic process and are rapidly lost at differentiation onset. Delaying the G1/S transition in ESCs allows formation of 53BP1 nuclear bodies and suppresses ssDNA accumulation, fork slowing and reversal in the following S-phase. Genetic inactivation of fork slowing and reversal leads to chromosomal breakage in unperturbed ESCs. We propose that rapid cell cycle progression makes ESCs dependent on effective replication-coupled mechanisms to protect genome integrity.

Abstract

Embryonic stem cells (ESCs) represent a transient biological state, where pluripotency is coupled with fast proliferation. ESCs display a constitutively active DNA damage response (DDR), but its molecular determinants have remained elusive. Here we show in cultured ESCs and mouse embryos that H2AX phosphorylation is dependent on Ataxia telangiectasia and Rad3 related (ATR) and is associated with chromatin loading of the ssDNA-binding proteins RPA and RAD51. Single-molecule analysis of replication intermediates reveals massive ssDNA gap accumulation, reduced fork speed and frequent fork reversal. All these marks of replication stress do not impair the mitotic process and are rapidly lost at differentiation onset. Delaying the G1/S transition in ESCs allows formation of 53BP1 nuclear bodies and suppresses ssDNA accumulation, fork slowing and reversal in the following S-phase. Genetic inactivation of fork slowing and reversal leads to chromosomal breakage in unperturbed ESCs. We propose that rapid cell cycle progression makes ESCs dependent on effective replication-coupled mechanisms to protect genome integrity.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Institute of Molecular Cancer Research
07 Faculty of Science > Institute of Molecular Cancer Research

05 Vetsuisse Faculty > Department of Molecular Mechanisms of Disease
07 Faculty of Science > Department of Molecular Mechanisms of Disease
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2016
Deposited On:24 Feb 2016 14:45
Last Modified:03 Aug 2017 17:28
Publisher:Nature Publishing Group
ISSN:2041-1723
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1038/ncomms10660
PubMed ID:26876348

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Licence: Creative Commons: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

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