1
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Park J, Lee DH. Loss of protein phosphatase 4 inhibitory protein leads to genomic instability and heightens vulnerability to replication stress. Biochim Biophys Acta Gen Subj 2025; 1869:130797. [PMID: 40157551 DOI: 10.1016/j.bbagen.2025.130797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2024] [Revised: 03/09/2025] [Accepted: 03/22/2025] [Indexed: 04/01/2025]
Abstract
Protein phosphatase 4 inhibitory protein (PP4IP) has recently emerged as a key player in cellular processes, particularly in DNA double-strand break repair and telomere maintenance, although research on its functions remains limited. To further investigate the cellular pathways involving PP4IP, we conducted transcriptomic analysis via RNA sequencing in PP4IP-knockout cells and observed an upregulation of p21 expression. This upregulation was linked to an increased population of p21-positive G1-phase cells in the absence of PP4IP. Prior studies have suggested that unresolved under-replicated DNA in mother cells, transmitted to daughter cells, can trigger a quiescent G1 phase characterized by p21 expression and the formation of p53-binding protein 1 (53BP1) nuclear bodies. Consistent with this, we found a higher proportion of 53BP1 nuclear bodies-positive G1 cells in PP4IP-knockout cells compared to controls. Additionally, PP4IP-deficient cells displayed an increased occurrence of anaphase bridges-indicative of incomplete DNA replication-without a corresponding increase in lagging chromosomes. Furthermore, PP4IP-knockout cells exhibited a heightened susceptibility to replication stress, as evidenced by an elevated frequency of replication stress-induced chromatid breaks and increased sensitivity to such stress. Collectively, these results suggest that PP4IP plays a critical role in safeguarding cells from replication stress and ensuring genomic stability.
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Affiliation(s)
- Jaehong Park
- Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, Republic of Korea.
| | - Dong-Hyun Lee
- Department of Biological Sciences, College of Natural Sciences, Chonnam National University, Gwangju, Republic of Korea; Research Center of Ecomimetics, Chonnam National University, Gwangju, Republic of Korea; Institute of Sustainable Ecological Environment, Chonnam National Univesity, Gwangju, Republic of Korea.
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2
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Ngoi NYL, Gallo D, Torrado C, Nardo M, Durocher D, Yap TA. Synthetic lethal strategies for the development of cancer therapeutics. Nat Rev Clin Oncol 2025; 22:46-64. [PMID: 39627502 DOI: 10.1038/s41571-024-00966-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2024] [Indexed: 12/20/2024]
Abstract
Synthetic lethality is a genetic phenomenon whereby the simultaneous presence of two different genetic alterations impairs cellular viability. Importantly, targeting synthetic lethal interactions offers potential therapeutic strategies for cancers with alterations in pathways that might otherwise be considered undruggable. High-throughput screening methods based on modern CRISPR-Cas9 technologies have emerged and become crucial for identifying novel synthetic lethal interactions with the potential for translation into biologically rational cancer therapeutic strategies as well as associated predictive biomarkers of response capable of guiding patient selection. Spurred by the clinical success of PARP inhibitors in patients with BRCA-mutant cancers, novel agents targeting multiple synthetic lethal interactions within DNA damage response pathways are in clinical development, and rational strategies targeting synthetic lethal interactions spanning alterations in epigenetic, metabolic and proliferative pathways have also emerged and are in late preclinical and/or early clinical testing. In this Review, we provide a comprehensive overview of established and emerging technologies for synthetic lethal drug discovery and development and discuss promising therapeutic strategies targeting such interactions.
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Affiliation(s)
- Natalie Y L Ngoi
- Department of Investigational Cancer Therapeutics (Phase I Clinical Trials Program), Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Haematology-Oncology, National University Cancer Institute, Singapore, Singapore
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - David Gallo
- Repare Therapeutics, Inc., Montreal, Quebec, Canada
| | - Carlos Torrado
- Department of Investigational Cancer Therapeutics (Phase I Clinical Trials Program), Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Mirella Nardo
- Department of Investigational Cancer Therapeutics (Phase I Clinical Trials Program), Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Daniel Durocher
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Timothy A Yap
- Department of Investigational Cancer Therapeutics (Phase I Clinical Trials Program), Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- Therapeutics Discovery Division, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
- Khalifa Institute for Personalized Cancer Therapy, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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3
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Nusawardhana A, Pale LM, Nicolae CM, Moldovan GL. USP1-dependent nucleolytic expansion of PRIMPOL-generated nascent DNA strand discontinuities during replication stress. Nucleic Acids Res 2024; 52:2340-2354. [PMID: 38180818 PMCID: PMC10954467 DOI: 10.1093/nar/gkad1237] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 12/11/2023] [Accepted: 12/15/2023] [Indexed: 01/07/2024] Open
Abstract
DNA replication stress-induced fork arrest represents a significant threat to genomic integrity. One major mechanism of replication restart involves repriming downstream of the arrested fork by PRIMPOL, leaving behind a single-stranded DNA (ssDNA) gap. Accumulation of nascent strand ssDNA gaps has emerged as a possible determinant of the cellular hypersensitivity to genotoxic agents in certain genetic backgrounds such as BRCA deficiency, but how gaps are converted into cytotoxic structures is still unclear. Here, we investigate the processing of PRIMPOL-dependent ssDNA gaps upon replication stress induced by hydroxyurea and cisplatin. We show that gaps generated in PRIMPOL-overexpressing cells are expanded in the 3'-5' direction by the MRE11 exonuclease, and in the 5'-3' direction by the EXO1 exonuclease. This bidirectional exonucleolytic gap expansion ultimately promotes their conversion into DSBs. We moreover identify the de-ubiquitinating enzyme USP1 as a critical regulator of PRIMPOL-generated ssDNA gaps. USP1 promotes gap accumulation during S-phase, and their expansion by the MRE11 and EXO1 nucleases. This activity of USP1 is linked to its role in de-ubiquitinating PCNA, suggesting that PCNA ubiquitination prevents gap accumulation during replication. Finally, we show that USP1 depletion suppresses DSB formation in PRIMPOL-overexpressing cells, highlighting an unexpected role for USP1 in promoting genomic instability under these conditions.
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Affiliation(s)
- Alexandra Nusawardhana
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Lindsey M Pale
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Claudia M Nicolae
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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Yates M, Marois I, St-Hilaire E, Ronato DA, Djerir B, Brochu C, Morin T, Hammond-Martel I, Gezzar-Dandashi S, Casimir L, Drobetsky E, Cappadocia L, Masson JY, Wurtele H, Maréchal A. SMARCAL1 ubiquitylation controls its association with RPA-coated ssDNA and promotes replication fork stability. PLoS Biol 2024; 22:e3002552. [PMID: 38502677 PMCID: PMC10950228 DOI: 10.1371/journal.pbio.3002552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 02/19/2024] [Indexed: 03/21/2024] Open
Abstract
Impediments in replication fork progression cause genomic instability, mutagenesis, and severe pathologies. At stalled forks, RPA-coated single-stranded DNA (ssDNA) activates the ATR kinase and directs fork remodeling, 2 key early events of the replication stress response. RFWD3, a recently described Fanconi anemia (FA) ubiquitin ligase, associates with RPA and promotes its ubiquitylation, facilitating late steps of homologous recombination (HR). Intriguingly, RFWD3 also regulates fork progression, restart and stability via poorly understood mechanisms. Here, we used proteomics to identify putative RFWD3 substrates during replication stress in human cells. We show that RFWD3 interacts with and ubiquitylates the SMARCAL1 DNA translocase directly in vitro and following DNA damage in vivo. SMARCAL1 ubiquitylation does not trigger its subsequent proteasomal degradation but instead disengages it from RPA thereby regulating its function at replication forks. Proper regulation of SMARCAL1 by RFWD3 at stalled forks protects them from excessive MUS81-mediated cleavage in response to UV irradiation, thereby limiting DNA replication stress. Collectively, our results identify RFWD3-mediated SMARCAL1 ubiquitylation as a novel mechanism that modulates fork remodeling to avoid genome instability triggered by aberrant fork processing.
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Affiliation(s)
- Maïlyn Yates
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Isabelle Marois
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Edlie St-Hilaire
- Research Center, Maisonneuve-Rosemont Hospital, Montréal, Canada
| | - Daryl A. Ronato
- Genome Stability Laboratory, CHU de Québec Research Center, Oncology Division; Department of Molecular Biology, Medical Biochemistry and Pathology; Laval University Cancer Research Center, Québec City, Canada
| | - Billel Djerir
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Chloé Brochu
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Théo Morin
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | | | | | - Lisa Casimir
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Elliot Drobetsky
- Research Center, Maisonneuve-Rosemont Hospital, Montréal, Canada
- Medicine Department, Université de Montréal, Montréal, Canada
| | - Laurent Cappadocia
- Faculty of Sciences, Department of Chemistry, Université du Québec à Montréal, Montréal, Canada
| | - Jean-Yves Masson
- Genome Stability Laboratory, CHU de Québec Research Center, Oncology Division; Department of Molecular Biology, Medical Biochemistry and Pathology; Laval University Cancer Research Center, Québec City, Canada
| | - Hugo Wurtele
- Research Center, Maisonneuve-Rosemont Hospital, Montréal, Canada
- Medicine Department, Université de Montréal, Montréal, Canada
| | - Alexandre Maréchal
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
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Hale A, Dhoonmoon A, Straka J, Nicolae CM, Moldovan GL. Multi-step processing of replication stress-derived nascent strand DNA gaps by MRE11 and EXO1 nucleases. Nat Commun 2023; 14:6265. [PMID: 37805499 PMCID: PMC10560291 DOI: 10.1038/s41467-023-42011-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 09/27/2023] [Indexed: 10/09/2023] Open
Abstract
Accumulation of single stranded DNA (ssDNA) gaps in the nascent strand during DNA replication has been associated with cytotoxicity and hypersensitivity to genotoxic stress, particularly upon inactivation of the BRCA tumor suppressor pathway. However, how ssDNA gaps contribute to genotoxicity is not well understood. Here, we describe a multi-step nucleolytic processing of replication stress-induced ssDNA gaps which converts them into cytotoxic double stranded DNA breaks (DSBs). We show that ssDNA gaps are extended bidirectionally by MRE11 in the 3'-5' direction and by EXO1 in the 5'-3' direction, in a process which is suppressed by the BRCA pathway. Subsequently, the parental strand at the ssDNA gap is cleaved by the MRE11 endonuclease generating a double strand break. We also show that exposure to bisphenol A (BPA) and diethylhexyl phthalate (DEHP), which are widespread environmental contaminants due to their use in plastics manufacturing, causes nascent strand ssDNA gaps during replication. These gaps are processed through the same mechanism described above to generate DSBs. Our work sheds light on both the relevance of ssDNA gaps as major determinants of genomic instability, as well as the mechanism through which they are processed to generate genomic instability and cytotoxicity.
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Affiliation(s)
- Anastasia Hale
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Ashna Dhoonmoon
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Joshua Straka
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA
| | - Claudia M Nicolae
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA.
| | - George-Lucian Moldovan
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University College of Medicine, Hershey, PA, 17033, USA.
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Liu Q, Peng Q, Zhang B, Tan Y. X-ray cross-complementing family: the bridge linking DNA damage repair and cancer. J Transl Med 2023; 21:602. [PMID: 37679817 PMCID: PMC10483876 DOI: 10.1186/s12967-023-04447-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 08/17/2023] [Indexed: 09/09/2023] Open
Abstract
Genomic instability is a common hallmark of human tumours. As a carrier of genetic information, DNA is constantly threatened by various damaging factors that, if not repaired in time, can affect the transmission of genetic information and lead to cellular carcinogenesis. In response to these threats, cells have evolved a range of DNA damage response mechanisms, including DNA damage repair, to maintain genomic stability. The X-ray repair cross-complementary gene family (XRCC) comprises an important class of DNA damage repair genes that encode proteins that play important roles in DNA single-strand breakage and DNA base damage repair. The dysfunction of the XRCC gene family is associated with the development of various tumours. In the context of tumours, mutations in XRCC and its aberrant expression, result in abnormal DNA damage repair, thus contributing to the malignant progression of tumour cells. In this review, we summarise the significant roles played by XRCC in diverse tumour types. In addition, we discuss the correlation between the XRCC family members and tumour therapeutic sensitivity.
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Affiliation(s)
- Qiang Liu
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, 283 Tongzipo Road, Changsha, 410013, Hunan, China
- NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Sciences, Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha, 410078, Hunan, China
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410008, Hunan, China
| | - Qiu Peng
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, 283 Tongzipo Road, Changsha, 410013, Hunan, China
| | - Bin Zhang
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, 283 Tongzipo Road, Changsha, 410013, Hunan, China.
- Department of Histology and Embryology, Xiangya School of Medicine, Central South University, Changsha, 410013, Hunan, China.
| | - Yueqiu Tan
- Hunan Cancer Hospital and the Affiliated Cancer Hospital of Xiangya School of Medicine, Central South University, 283 Tongzipo Road, Changsha, 410013, Hunan, China.
- NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Sciences, Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha, 410078, Hunan, China.
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, 410008, Hunan, China.
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Casimir L, Zimmer S, Racine-Brassard F, Goudreau F, Jacques PÉ, Maréchal A. Chronic treatment with ATR and CHK1 inhibitors does not substantially increase the mutational burden of human cells. Mutat Res 2023; 827:111834. [PMID: 37531716 DOI: 10.1016/j.mrfmmm.2023.111834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/13/2023] [Accepted: 07/19/2023] [Indexed: 08/04/2023]
Abstract
DNA replication stress (RS) entails the frequent slow down and arrest of replication forks by a variety of conditions that hinder accurate and processive genome duplication. Elevated RS leads to genome instability, replication catastrophe and eventually cell death. RS is particularly prevalent in cancer cells and its exacerbation to unsustainable levels by chemotherapeutic agents remains a cornerstone of cancer treatments. The adverse consequences of RS are normally prevented by the ATR and CHK1 checkpoint kinases that stabilize stressed forks, suppress origin firing and promote cell cycle arrest when replication is perturbed. Specific inhibitors of these kinases have been developed and shown to potentiate RS and cell death in multiple in vitro cancer settings. Ongoing clinical trials are now probing their efficacy against various cancer types, either as single agents or in combination with mainstay chemotherapeutics. Despite their promise as valuable additions to the anti-cancer pharmacopoeia, we still lack a genome-wide view of the potential mutagenicity of these new drugs. To investigate this question, we performed chronic long-term treatments of TP53-depleted human cancer cells with ATR and CHK1 inhibitors (ATRi, AZD6738/ceralasertib and CHK1i, MK8776/SCH-900776). ATR or CHK1 inhibition did not significantly increase the mutational burden of cells, nor generate specific mutational signatures. Indeed, no notable changes in the numbers of base substitutions, short insertions/deletions and larger scale rearrangements were observed despite induction of replication-associated DNA breaks during treatments. Interestingly, ATR inhibition did induce a slight increase in closely-spaced mutations, a feature previously attributed to translesion synthesis DNA polymerases. The results suggest that ATRi and CHK1i do not have substantial mutagenic effects in vitro when used as standalone agents.
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Affiliation(s)
- Lisa Casimir
- Département de Biologie, Université de Sherbrooke, Sherbrooke J1K 2R1, QC, Canada; Institut de Recherche sur le Cancer de l'Université de Sherbrooke (IRCUS), Sherbrooke J1K 2R1, QC, Canada
| | - Samuel Zimmer
- Département de Biologie, Université de Sherbrooke, Sherbrooke J1K 2R1, QC, Canada; Institut de Recherche sur le Cancer de l'Université de Sherbrooke (IRCUS), Sherbrooke J1K 2R1, QC, Canada
| | - Félix Racine-Brassard
- Département de Biologie, Université de Sherbrooke, Sherbrooke J1K 2R1, QC, Canada; Institut de Recherche sur le Cancer de l'Université de Sherbrooke (IRCUS), Sherbrooke J1K 2R1, QC, Canada
| | - Félix Goudreau
- Département de Biologie, Université de Sherbrooke, Sherbrooke J1K 2R1, QC, Canada; Institut de Recherche sur le Cancer de l'Université de Sherbrooke (IRCUS), Sherbrooke J1K 2R1, QC, Canada
| | - Pierre-Étienne Jacques
- Département de Biologie, Université de Sherbrooke, Sherbrooke J1K 2R1, QC, Canada; Institut de Recherche sur le Cancer de l'Université de Sherbrooke (IRCUS), Sherbrooke J1K 2R1, QC, Canada; Centre de recherche du Centre hospitalier universitaire de Sherbrooke (CRCHUS), Sherbrooke J1H 5N3, QC, Canada.
| | - Alexandre Maréchal
- Département de Biologie, Université de Sherbrooke, Sherbrooke J1K 2R1, QC, Canada; Institut de Recherche sur le Cancer de l'Université de Sherbrooke (IRCUS), Sherbrooke J1K 2R1, QC, Canada; Centre de recherche du Centre hospitalier universitaire de Sherbrooke (CRCHUS), Sherbrooke J1H 5N3, QC, Canada.
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