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Poly(ADP-ribosyl)gycohydrolase (PARG) prevents the accumulation of unusual replication structures during unperturbed S phase


Ray Chaudhuri, Arnab; Ahuja, Akshay Kumar; Herrador, Raquel; Lopes, Massimo (2014). Poly(ADP-ribosyl)gycohydrolase (PARG) prevents the accumulation of unusual replication structures during unperturbed S phase. Molecular and Cellular Biology:1-33.

Abstract

Poly(ADP-ribosyl)ation (PAR) has been implicated in various aspects of the cellular response to DNA damage and genome stability. Although 17 human poly(ADP-ribose) polymerase (PARP) genes have been identified, a single poly(ADP-ribose) glycohydrolase (PARG) mediates PAR degradation. Here we investigated the role of PARG in the replication of human chromosomes. We show that PARG depletion affects cell proliferation and DNA synthesis, leading to replication-coupled H2AX phosphorylation. Furthermore, PARG depletion or inhibition per se slows down individual replication forks similarly to mild chemotherapeutic treatment. Electron microscopic analysis of replication intermediates reveals marked accumulation of reversed forks and ssDNA gaps in unperturbed PARG-defective cells. Intriguingly, while we found no physical evidence for chromosomal breakage, PARG defective cells displayed both ATM and ATR activation, as well as chromatin recruitment of standard double strand break repair factors, such as 53BP1 and RAD51. Overall, these data prove PAR degradation essential to promote resumption of replication at endogenous and exogenous lesions, preventing idle recruitment of repair factors to remodeled replication forks. Furthermore, they suggest that fork remodeling and restart are surprisingly frequent in unperturbed cells and provide a molecular rationale to explore PARG inhibition in cancer chemotherapy.

Poly(ADP-ribosyl)ation (PAR) has been implicated in various aspects of the cellular response to DNA damage and genome stability. Although 17 human poly(ADP-ribose) polymerase (PARP) genes have been identified, a single poly(ADP-ribose) glycohydrolase (PARG) mediates PAR degradation. Here we investigated the role of PARG in the replication of human chromosomes. We show that PARG depletion affects cell proliferation and DNA synthesis, leading to replication-coupled H2AX phosphorylation. Furthermore, PARG depletion or inhibition per se slows down individual replication forks similarly to mild chemotherapeutic treatment. Electron microscopic analysis of replication intermediates reveals marked accumulation of reversed forks and ssDNA gaps in unperturbed PARG-defective cells. Intriguingly, while we found no physical evidence for chromosomal breakage, PARG defective cells displayed both ATM and ATR activation, as well as chromatin recruitment of standard double strand break repair factors, such as 53BP1 and RAD51. Overall, these data prove PAR degradation essential to promote resumption of replication at endogenous and exogenous lesions, preventing idle recruitment of repair factors to remodeled replication forks. Furthermore, they suggest that fork remodeling and restart are surprisingly frequent in unperturbed cells and provide a molecular rationale to explore PARG inhibition in cancer chemotherapy.

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3 citations in Web of Science®
2 citations in Scopus®
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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
Dewey Decimal Classification:570 Life sciences; biology
Language:English
Date:22 December 2014
Deposited On:06 Feb 2015 15:27
Last Modified:05 Apr 2016 18:49
Publisher:American Society for Microbiology
ISSN:0270-7306
Publisher DOI:https://doi.org/10.1128/MCB.01077-14
PubMed ID:25535335
Permanent URL: https://doi.org/10.5167/uzh-104942

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