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Muñoz S, Blanco-Romero E, González-Acosta D, Rodriguez-Acebes S, Megías D, Lopes M, Méndez J. RAD51 restricts DNA over-replication from re-activated origins. EMBO J 2024; 43:1043-1064. [PMID: 38360996 PMCID: PMC10942984 DOI: 10.1038/s44318-024-00038-z] [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: 03/14/2023] [Revised: 01/11/2024] [Accepted: 01/12/2024] [Indexed: 02/17/2024] Open
Abstract
Eukaryotic cells rely on several mechanisms to ensure that the genome is duplicated precisely once in each cell division cycle, preventing DNA over-replication and genomic instability. Most of these mechanisms limit the activity of origin licensing proteins to prevent the reactivation of origins that have already been used. Here, we have investigated whether additional controls restrict the extension of re-replicated DNA in the event of origin re-activation. In a genetic screening in cells forced to re-activate origins, we found that re-replication is limited by RAD51 and enhanced by FBH1, a RAD51 antagonist. In the presence of chromatin-bound RAD51, forks stemming from re-fired origins are slowed down, leading to frequent events of fork reversal. Eventual re-initiation of DNA synthesis mediated by PRIMPOL creates ssDNA gaps that facilitate the partial elimination of re-duplicated DNA by MRE11 exonuclease. In the absence of RAD51, these controls are abrogated and re-replication forks progress much longer than in normal conditions. Our study uncovers a safeguard mechanism to protect genome stability in the event of origin reactivation.
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Affiliation(s)
- Sergio Muñoz
- DNA Replication Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029, Madrid, Spain
| | - Elena Blanco-Romero
- DNA Replication Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029, Madrid, Spain
| | - Daniel González-Acosta
- DNA Replication Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029, Madrid, Spain
- Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Sara Rodriguez-Acebes
- DNA Replication Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029, Madrid, Spain
| | - Diego Megías
- Confocal Microscopy Unit, Biotechnology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029, Madrid, Spain
- Advanced Optical Microscopy Unit, Central Core Facilities, Instituto de Salud Carlos III, Madrid, Spain
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Juan Méndez
- DNA Replication Group, Molecular Oncology Programme, Spanish National Cancer Research Centre (CNIO), Melchor Fernández Almagro 3, 28029, Madrid, Spain.
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2
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Berg C, Sieber M, Sun J. Finishing the egg. Genetics 2024; 226:iyad183. [PMID: 38000906 PMCID: PMC10763546 DOI: 10.1093/genetics/iyad183] [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: 07/05/2023] [Accepted: 09/27/2023] [Indexed: 11/26/2023] Open
Abstract
Gamete development is a fundamental process that is highly conserved from early eukaryotes to mammals. As germ cells develop, they must coordinate a dynamic series of cellular processes that support growth, cell specification, patterning, the loading of maternal factors (RNAs, proteins, and nutrients), differentiation of structures to enable fertilization and ensure embryonic survival, and other processes that make a functional oocyte. To achieve these goals, germ cells integrate a complex milieu of environmental and developmental signals to produce fertilizable eggs. Over the past 50 years, Drosophila oogenesis has risen to the forefront as a system to interrogate the sophisticated mechanisms that drive oocyte development. Studies in Drosophila have defined mechanisms in germ cells that control meiosis, protect genome integrity, facilitate mRNA trafficking, and support the maternal loading of nutrients. Work in this system has provided key insights into the mechanisms that establish egg chamber polarity and patterning as well as the mechanisms that drive ovulation and egg activation. Using the power of Drosophila genetics, the field has begun to define the molecular mechanisms that coordinate environmental stresses and nutrient availability with oocyte development. Importantly, the majority of these reproductive mechanisms are highly conserved throughout evolution, and many play critical roles in the development of somatic tissues as well. In this chapter, we summarize the recent progress in several key areas that impact egg chamber development and ovulation. First, we discuss the mechanisms that drive nutrient storage and trafficking during oocyte maturation and vitellogenesis. Second, we examine the processes that regulate follicle cell patterning and how that patterning impacts the construction of the egg shell and the establishment of embryonic polarity. Finally, we examine regulatory factors that control ovulation, egg activation, and successful fertilization.
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Affiliation(s)
- Celeste Berg
- Department of Genome Sciences, University of Washington, Seattle, WA 98195-5065USA
| | - Matthew Sieber
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390USA
| | - Jianjun Sun
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269USA
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3
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Lavudi K, Banerjee A, Li N, Yang Y, Cai S, Bai X, Zhang X, Li A, Wani E, Yang SM, Zhang J, Rai G, Backes F, Patnaik S, Guo P, Wang QE. ALDH1A1 promotes PARP inhibitor resistance by enhancing retinoic acid receptor-mediated DNA polymerase θ expression. NPJ Precis Oncol 2023; 7:66. [PMID: 37429899 DOI: 10.1038/s41698-023-00411-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 05/30/2023] [Indexed: 07/12/2023] Open
Abstract
Poly (ADP-ribose) Polymerase (PARP) inhibitors (PARPi) have been approved for both frontline and recurrent setting in ovarian cancer with homologous recombination (HR) repair deficiency. However, more than 40% of BRCA1/2-mutated ovarian cancer lack the initial response to PARPi treatment, and the majority of those that initially respond eventually develop resistance. Our previous study has demonstrated that increased expression of aldehyde dehydrogenase 1A1 (ALDH1A1) contributes to PARPi resistance in BRCA2-mutated ovarian cancer cells by enhancing microhomology-mediated end joining (MMEJ) but the mechanism remains unknown. Here, we find that ALDH1A1 enhances the expression of DNA polymerase θ (Polθ, encoded by the POLQ gene) in ovarian cancer cells. Furthermore, we demonstrate that the retinoic acid (RA) pathway is involved in the transcription activation of the POLQ gene. The RA receptor (RAR) can bind to the retinoic acid response element (RARE) located in the promoter of the POLQ gene, promoting transcription activation-related histone modification in the presence of RA. Given that ALDH1A1 catalyzes the biosynthesis of RA, we conclude that ALDH1A1 promotes POLQ expression via the activation of the RA signaling pathway. Finally, using a clinically-relevant patient-derived organoid (PDO) model, we find that ALDH1A1 inhibition by the pharmacological inhibitor NCT-505 in combination with the PARP inhibitor olaparib synergistically reduce the cell viability of PDOs carrying BRCA1/2 mutation and positive ALDH1A1 expression. In summary, our study elucidates a new mechanism contributing to PARPi resistance in HR-deficient ovarian cancer and shows the therapeutic potential of combining PARPi and ALDH1A1 inhibition in treating these patients.
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Affiliation(s)
- Kousalya Lavudi
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Ananya Banerjee
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Na Li
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Yajing Yang
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Shurui Cai
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Xuetao Bai
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Xiaoli Zhang
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - Aidan Li
- Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Elsa Wani
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - Shyh-Ming Yang
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, 20850, USA
| | - Junran Zhang
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA
| | - Ganesha Rai
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, 20850, USA
| | - Floor Backes
- Department of Obstetrics & Gynecology, Division of Gynecologic Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - Srinivas Patnaik
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Peixuan Guo
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
- Center for RNA Nanobiotechnology and Nanomedicine, Division of Pharmaceutics and Pharmacology, College of Pharmacy, The Ohio State University, Columbus, OH, 43210, USA
| | - Qi-En Wang
- Department of Radiation Oncology, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA.
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, 43210, USA.
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4
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Abstract
DNA polymerase θ (Pol θ) is a DNA repair enzyme widely conserved in animals and plants. Pol θ uses short DNA sequence homologies to initiate repair of double-strand breaks by theta-mediated end joining. The DNA polymerase domain of Pol θ is at the C terminus and is connected to an N-terminal DNA helicase-like domain by a central linker. Pol θ is crucial for maintenance of damaged genomes during development, protects DNA against extensive deletions, and limits loss of heterozygosity. The cost of using Pol θ for genome protection is that a few nucleotides are usually deleted or added at the repair site. Inactivation of Pol θ often enhances the sensitivity of cells to DNA strand-breaking chemicals and radiation. Since some homologous recombination-defective cancers depend on Pol θ for growth, inhibitors of Pol θ may be useful in treating such tumors.
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Affiliation(s)
- Richard D Wood
- Department of Epigenetics and Molecular Carcinogenesis, The University of Texas MD Anderson Center, Houston, Texas, USA;
| | - Sylvie Doublié
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont, USA;
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5
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Reusswig KU, Bittmann J, Peritore M, Courtes M, Pardo B, Wierer M, Mann M, Pfander B. Unscheduled DNA replication in G1 causes genome instability and damage signatures indicative of replication collisions. Nat Commun 2022; 13:7014. [PMID: 36400763 PMCID: PMC9674678 DOI: 10.1038/s41467-022-34379-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 10/24/2022] [Indexed: 11/19/2022] Open
Abstract
DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineer genetic systems in budding yeast to induce unscheduled replication in a G1-like cell cycle state. Unscheduled G1 replication initiates at canonical S-phase origins. We quantifiy the composition of replisomes in G1- and S-phase and identified firing factors, polymerase α, and histone supply as factors that limit replication outside S-phase. G1 replication per se does not trigger cellular checkpoints. Subsequent replication during S-phase, however, results in over-replication and leads to chromosome breaks and chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA, indicating head-to-tail replication collisions as a key mechanism generating genome instability upon G1 replication. Low-level, sporadic induction of G1 replication induces an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation.
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Affiliation(s)
- Karl-Uwe Reusswig
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.38142.3c000000041936754XPresent Address: Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115 USA ,grid.65499.370000 0001 2106 9910Present Address: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215 USA
| | - Julia Bittmann
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Martina Peritore
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany
| | - Mathilde Courtes
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Benjamin Pardo
- grid.433120.7Institut de Génétique Humaine (IGH), Université de Montpellier – Centre National de la Recherche Scientifique, 34396 Montpellier, France
| | - Michael Wierer
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.5254.60000 0001 0674 042XPresent Address: Proteomics Research Infrastructure, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Matthias Mann
- grid.418615.f0000 0004 0491 845XProteomics and Signal Transduction, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Boris Pfander
- grid.418615.f0000 0004 0491 845XDNA Replication and Genome Integrity, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany ,grid.7551.60000 0000 8983 7915Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Aerospace Medicine, German Aerospace Center (DLR), 51147 Cologne, Germany ,grid.6190.e0000 0000 8580 3777Present Address: Genome Maintenance Mechanisms in Health and Disease, Institute of Genome Stability in Ageing and Disease, CECAD Research Center, University of Cologne, 50931 Cologne, Germany
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6
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Jiang Y. Contribution of Microhomology to Genome Instability: Connection between DNA Repair and Replication Stress. Int J Mol Sci 2022; 23:12937. [PMID: 36361724 PMCID: PMC9657218 DOI: 10.3390/ijms232112937] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 10/23/2022] [Accepted: 10/23/2022] [Indexed: 11/23/2023] Open
Abstract
Microhomology-mediated end joining (MMEJ) is a highly mutagenic pathway to repair double-strand breaks (DSBs). MMEJ was thought to be a backup pathway of homologous recombination (HR) and canonical nonhomologous end joining (C-NHEJ). However, it attracts more attention in cancer research due to its special function of microhomology in many different aspects of cancer. In particular, it is initiated with DNA end resection and upregulated in homologous recombination-deficient cancers. In this review, I summarize the following: (1) the recent findings and contributions of MMEJ to genome instability, including phenotypes relevant to MMEJ; (2) the interaction between MMEJ and other DNA repair pathways; (3) the proposed mechanistic model of MMEJ in DNA DSB repair and a new connection with microhomology-mediated break-induced replication (MMBIR); and (4) the potential clinical application by targeting MMEJ based on synthetic lethality for cancer therapy.
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Affiliation(s)
- Yuning Jiang
- Department of Radiation Oncology, University of Virginia, Charlottesville, VA 22903, USA
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7
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Clay DE, Fox DT. DNA Damage Responses during the Cell Cycle: Insights from Model Organisms and Beyond. Genes (Basel) 2021; 12:1882. [PMID: 34946831 PMCID: PMC8701014 DOI: 10.3390/genes12121882] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 12/25/2022] Open
Abstract
Genome damage is a threat to all organisms. To respond to such damage, DNA damage responses (DDRs) lead to cell cycle arrest, DNA repair, and cell death. Many DDR components are highly conserved, whereas others have adapted to specific organismal needs. Immense progress in this field has been driven by model genetic organism research. This review has two main purposes. First, we provide a survey of model organism-based efforts to study DDRs. Second, we highlight how model organism study has contributed to understanding how specific DDRs are influenced by cell cycle stage. We also look forward, with a discussion of how future study can be expanded beyond typical model genetic organisms to further illuminate how the genome is protected.
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Affiliation(s)
- Delisa E. Clay
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA;
| | - Donald T. Fox
- Department of Cell Biology, Duke University School of Medicine, Durham, NC 27710, USA;
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA
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8
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Prodhomme MK, Péricart S, Pommier RM, Morel AP, Brunac AC, Franchet C, Moyret-Lalle C, Brousset P, Puisieux A, Hoffmann JS, Tissier A. Opposite Roles for ZEB1 and TMEJ in the Regulation of Breast Cancer Genome Stability. Front Cell Dev Biol 2021; 9:727429. [PMID: 34458275 PMCID: PMC8388841 DOI: 10.3389/fcell.2021.727429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 07/23/2021] [Indexed: 12/22/2022] Open
Abstract
Breast cancer cells frequently acquire mutations in faithful DNA repair genes, as exemplified by BRCA-deficiency. Moreover, overexpression of an inaccurate DNA repair pathway may also be at the origin of the genetic instability arising during the course of cancer progression. The specific gain in expression of POLQ, encoding the error-prone DNA polymerase Theta (POLθ) involved in theta-mediated end joining (TMEJ), is associated with a characteristic mutational signature. To gain insight into the mechanistic regulation of POLQ expression, this review briefly presents recent findings on the regulation of POLQ in the claudin-low breast tumor subtype, specifically expressing transcription factors involved in epithelial-to-mesenchymal transition (EMT) such as ZEB1 and displaying a paucity in genomic abnormality.
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Affiliation(s)
- Mélanie K Prodhomme
- INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Équipe Labellisée Ligue Contre le Cancer, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France.,LabEx DEVweCAN, Université de Lyon, Lyon, France
| | - Sarah Péricart
- Laboratoire d'Excellence Toulouse Cancer (TOUCAN), Laboratoire de Pathologie, Institut Universitaire du Cancer-Toulouse, Toulouse, France
| | - Roxane M Pommier
- Gilles Thomas Bioinformatics Platform, Centre Léon Bérard, Cancer Research Centre of Lyon, Lyon, France
| | - Anne-Pierre Morel
- INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Équipe Labellisée Ligue Contre le Cancer, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France.,LabEx DEVweCAN, Université de Lyon, Lyon, France
| | - Anne-Cécile Brunac
- Laboratoire d'Excellence Toulouse Cancer (TOUCAN), Laboratoire de Pathologie, Institut Universitaire du Cancer-Toulouse, Toulouse, France
| | - Camille Franchet
- Laboratoire d'Excellence Toulouse Cancer (TOUCAN), Laboratoire de Pathologie, Institut Universitaire du Cancer-Toulouse, Toulouse, France
| | - Caroline Moyret-Lalle
- INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Équipe Labellisée Ligue Contre le Cancer, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France.,LabEx DEVweCAN, Université de Lyon, Lyon, France
| | - Pierre Brousset
- Laboratoire d'Excellence Toulouse Cancer (TOUCAN), Laboratoire de Pathologie, Institut Universitaire du Cancer-Toulouse, Toulouse, France
| | - Alain Puisieux
- INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Équipe Labellisée Ligue Contre le Cancer, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France.,Institut Curie, Versailles Saint-Quentin-en-Yvelines University, PSL Research University, Paris, France
| | - Jean-Sébastien Hoffmann
- Laboratoire d'Excellence Toulouse Cancer (TOUCAN), Laboratoire de Pathologie, Institut Universitaire du Cancer-Toulouse, Toulouse, France
| | - Agnès Tissier
- INSERM 1052, CNRS 5286, Centre Léon Bérard, Cancer Research Centre of Lyon, Équipe Labellisée Ligue Contre le Cancer, Université de Lyon, Université Claude Bernard Lyon 1, Lyon, France.,LabEx DEVweCAN, Université de Lyon, Lyon, France
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9
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Nisa M, Bergis C, Pedroza-Garcia JA, Drouin-Wahbi J, Mazubert C, Bergounioux C, Benhamed M, Raynaud C. The plant DNA polymerase theta is essential for the repair of replication-associated DNA damage. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 106:1197-1207. [PMID: 33989439 DOI: 10.1111/tpj.15295] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 04/15/2021] [Accepted: 04/21/2021] [Indexed: 06/12/2023]
Abstract
Safeguarding of genome integrity is a key process in all living organisms. Due to their sessile lifestyle, plants are particularly exposed to all kinds of stress conditions that could induce DNA damage. However, very few genes involved in the maintenance of genome integrity are indispensable to plants' viability. One remarkable exception is the POLQ gene, which encodes DNA polymerase theta (Pol θ), a non-replicative polymerase involved in trans-lesion synthesis during DNA replication and double-strand break (DSB) repair. The Arabidopsis tebichi (teb) mutants, deficient in Pol θ, have been reported to display severe developmental defects, leading to the conclusion that Pol θ is required for normal plant development. However, this essential role of Pol θ in plants is challenged by contradictory reports regarding the phenotypic defects of teb mutants and the recent finding that rice (Oryza sativa) null mutants develop normally. Here we show that the phenotype of teb mutants is highly variable. Taking advantage of hypomorphic mutants for the replicative DNA polymerase epsilon, which display constitutive replicative stress, we show that Pol θ allows maintenance of meristem activity when DNA replication is partially compromised. Furthermore, we found that the phenotype of Pol θ mutants can be aggravated by modifying their growth conditions, suggesting that environmental conditions impact the basal level of replicative stress and providing evidence for a link between plants' responses to adverse conditions and mechanisms involved in the maintenance of genome integrity.
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Affiliation(s)
- Maherun Nisa
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
| | - Clara Bergis
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
| | - Jose-Antonio Pedroza-Garcia
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
| | - Jeannine Drouin-Wahbi
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
| | - Christelle Mazubert
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
| | - Catherine Bergounioux
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
| | - Moussa Benhamed
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
- Institut Universitaire de France (IUF), France
| | - Cécile Raynaud
- Institute of Plant Sciences Paris-Saclay (IPS2), Université Paris-Saclay, CNRS, INRAE, Univ Evry, Orsay, 91405, France
- Institute of Plant Sciences Paris Saclay, Université de Paris, CNRS, INRAE, Orsay, (IPS2) 91405, France
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10
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Schrempf A, Slyskova J, Loizou JI. Targeting the DNA Repair Enzyme Polymerase θ in Cancer Therapy. Trends Cancer 2021; 7:98-111. [PMID: 33109489 DOI: 10.1016/j.trecan.2020.09.007] [Citation(s) in RCA: 91] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/21/2020] [Accepted: 09/28/2020] [Indexed: 12/21/2022]
Abstract
Targeted cancer therapies represent a milestone towards personalized treatment as they function via inhibition of cancer-specific alterations. Polymerase θ (POLQ), an error-prone translesion polymerase, also involved in DNA double-strand break (DSB) repair, is often upregulated in cancer. POLQ is synthetic lethal with various DNA repair genes, including known cancer drivers such as BRCA1/2, making it essential in homologous recombination-deficient cancers. Thus, POLQ represents a promising target in cancer therapy and efforts for the development of POLQ inhibitors are actively underway with first clinical trials due to start in 2021. This review summarizes the journey of POLQ from a backup DNA repair enzyme to a promising therapeutic target for cancer treatment.
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Affiliation(s)
- Anna Schrempf
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH BT 25.3, 1090 Vienna, Austria; Institute of Cancer Research, Department of Medicine I, Comprehensive Cancer Center, Medical University of Vienna, 1090 Vienna, Austria
| | - Jana Slyskova
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH BT 25.3, 1090 Vienna, Austria; Institute of Cancer Research, Department of Medicine I, Comprehensive Cancer Center, Medical University of Vienna, 1090 Vienna, Austria.
| | - Joanna I Loizou
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Lazarettgasse 14, AKH BT 25.3, 1090 Vienna, Austria; Institute of Cancer Research, Department of Medicine I, Comprehensive Cancer Center, Medical University of Vienna, 1090 Vienna, Austria.
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11
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Mognato M, Burdak-Rothkamm S, Rothkamm K. Interplay between DNA replication stress, chromatin dynamics and DNA-damage response for the maintenance of genome stability. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2020; 787:108346. [PMID: 34083038 DOI: 10.1016/j.mrrev.2020.108346] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 10/02/2020] [Accepted: 11/09/2020] [Indexed: 12/17/2022]
Abstract
DNA replication stress is a major source of DNA damage, including double-stranded breaks that promote DNA damage response (DDR) signaling. Inefficient repair of such lesions can affect genome integrity. During DNA replication different factors act on chromatin remodeling in a coordinated way. While recent studies have highlighted individual molecular mechanisms of interaction, less is known about the orchestration of chromatin changes under replication stress. In this review we attempt to explore the complex relationship between DNA replication stress, DDR and genome integrity in mammalian cells, taking into account the role of chromatin disposition as an important modulator of DNA repair. Recent data on chromatin restoration and epigenetic re-establishment after DNA replication stress are reviewed.
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Affiliation(s)
| | - Susanne Burdak-Rothkamm
- University Medical Center Hamburg-Eppendorf, Department of Radiotherapy, Laboratory of Radiobiology & Experimental Radiation Oncology, Germany.
| | - Kai Rothkamm
- University Medical Center Hamburg-Eppendorf, Department of Radiotherapy, Laboratory of Radiobiology & Experimental Radiation Oncology, Germany.
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12
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Karageorgiou C, Tarrío R, Rodríguez-Trelles F. The Cyclically Seasonal Drosophila subobscura Inversion O 7 Originated From Fragile Genomic Sites and Relocated Immunity and Metabolic Genes. Front Genet 2020; 11:565836. [PMID: 33193649 PMCID: PMC7584159 DOI: 10.3389/fgene.2020.565836] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 09/09/2020] [Indexed: 11/28/2022] Open
Abstract
Chromosome inversions are important contributors to standing genetic variation in Drosophila subobscura. Presently, the species is experiencing a rapid replacement of high-latitude by low-latitude inversions associated with global warming. Yet not all low-latitude inversions are correlated with the ongoing warming trend. This is particularly unexpected in the case of O7 because it shows a regular seasonal cycle that peaks in summer and rose with a heatwave. The inconsistent behavior of O7 across components of the ambient temperature suggests that is causally more complex than simply due to temperature alone. In order to understand the dynamics of O7, high-quality genomic data are needed to determine both the breakpoints and the genetic content. To fill this gap, here we generated a PacBio long read-based chromosome-scale genome assembly, from a highly homozygous line made isogenic for an O3 + 4 + 7 chromosome. Then we isolated the complete continuous sequence of O7 by conserved synteny analysis with the available reference genome. Main findings include the following: (i) the assembled O7 inversion stretches 9.936 Mb, containing > 1,000 annotated genes; (ii) O7 had a complex origin, involving multiple breaks associated with non-B DNA-forming motifs, formation of a microinversion, and ectopic repair in trans with the two homologous chromosomes; (iii) the O7 breakpoints carry a pre-inversion record of fragility, including a sequence insertion, and transposition with later inverted duplication of an Attacin immunity gene; and (iv) the O7 inversion relocated the major insulin signaling forkhead box subgroup O (foxo) gene in tight linkage with its antagonistic regulatory partner serine/threonine-protein kinase B (Akt1) and disrupted concerted evolution of the two inverted Attacin duplicates, reattaching them to dFOXO metabolic enhancers. Our findings suggest that O7 exerts antagonistic pleiotropic effects on reproduction and immunity, setting a framework to understand its relationship with climate change. Furthermore, they are relevant for fragility in genome rearrangement evolution and for current views on the contribution of breakage versus repair in shaping inversion-breakpoint junctions.
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Affiliation(s)
- Charikleia Karageorgiou
- Grup de Genòmica, Bioinformàtica i Biologia Evolutiva (GGBE), Departament de Genètica i de Microbiologia, Universitat Autonòma de Barcelona, Barcelona, Spain
| | - Rosa Tarrío
- Grup de Genòmica, Bioinformàtica i Biologia Evolutiva (GGBE), Departament de Genètica i de Microbiologia, Universitat Autonòma de Barcelona, Barcelona, Spain
| | - Francisco Rodríguez-Trelles
- Grup de Genòmica, Bioinformàtica i Biologia Evolutiva (GGBE), Departament de Genètica i de Microbiologia, Universitat Autonòma de Barcelona, Barcelona, Spain
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13
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Marygold SJ, Attrill H, Speretta E, Warner K, Magrane M, Berloco M, Cotterill S, McVey M, Rong Y, Yamaguchi M. The DNA polymerases of Drosophila melanogaster. Fly (Austin) 2020; 14:49-61. [PMID: 31933406 PMCID: PMC7714529 DOI: 10.1080/19336934.2019.1710076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
DNA synthesis during replication or repair is a fundamental cellular process that is catalyzed by a set of evolutionary conserved polymerases. Despite a large body of research, the DNA polymerases of Drosophila melanogaster have not yet been systematically reviewed, leading to inconsistencies in their nomenclature, shortcomings in their functional (Gene Ontology, GO) annotations and an under-appreciation of the extent of their characterization. Here, we describe the complete set of DNA polymerases in D. melanogaster, applying nomenclature already in widespread use in other species, and improving their functional annotation. A total of 19 genes encode the proteins comprising three replicative polymerases (alpha-primase, delta, epsilon), five translesion/repair polymerases (zeta, eta, iota, Rev1, theta) and the mitochondrial polymerase (gamma). We also provide an overview of the biochemical and genetic characterization of these factors in D. melanogaster. This work, together with the incorporation of the improved nomenclature and GO annotation into key biological databases, including FlyBase and UniProtKB, will greatly facilitate access to information about these important proteins.
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Affiliation(s)
- Steven J Marygold
- FlyBase, Department of Physiology, Development and Neuroscience, University of Cambridge , Cambridge, UK
| | - Helen Attrill
- FlyBase, Department of Physiology, Development and Neuroscience, University of Cambridge , Cambridge, UK
| | - Elena Speretta
- UniProt, European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI) , Cambridgeshire, UK
| | - Kate Warner
- UniProt, European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI) , Cambridgeshire, UK
| | - Michele Magrane
- UniProt, European Molecular Biology Laboratory, European Bioinformatics Institute (EMBL-EBI) , Cambridgeshire, UK
| | - Maria Berloco
- Dipartimento di Biologia, Università degli Studi di Bari "Aldo Moro" , Bari, Italy
| | - Sue Cotterill
- Department Basic Medical Sciences, St Georges University London , London, UK
| | - Mitch McVey
- Department of Biology, Tufts University , Medford, MA, USA
| | - Yikang Rong
- School of Life Sciences, Sun Yat-sen University , Guangzhou, China
| | - Masamitsu Yamaguchi
- Department of Applied Biology and Advanced Insect Research Promotion Center, Kyoto Institute of Technology , Kyoto, Japan
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14
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Kocak E, Dykstra S, Nemeth A, Coughlin CG, Rodgers K, McVey M. The Drosophila melanogaster PIF1 Helicase Promotes Survival During Replication Stress and Processive DNA Synthesis During Double-Strand Gap Repair. Genetics 2019; 213:835-847. [PMID: 31537623 PMCID: PMC6827366 DOI: 10.1534/genetics.119.302665] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 09/18/2019] [Indexed: 11/18/2022] Open
Abstract
PIF1 is a 5' to 3' DNA helicase that can unwind double-stranded DNA and disrupt nucleic acid-protein complexes. In Saccharomyces cerevisiae, Pif1 plays important roles in mitochondrial and nuclear genome maintenance, telomere length regulation, unwinding of G-quadruplex structures, and DNA synthesis during break-induced replication. Some, but not all, of these functions are shared with other eukaryotes. To gain insight into the evolutionarily conserved functions of PIF1, we created pif1 null mutants in Drosophila melanogaster and assessed their phenotypes throughout development. We found that pif1 mutant larvae exposed to high concentrations of hydroxyurea, but not other DNA damaging agents, experience reduced survival to adulthood. Embryos lacking PIF1 fail to segregate their chromosomes efficiently during early nuclear divisions, consistent with a defect in DNA replication. Furthermore, loss of the BRCA2 protein, which is required for stabilization of stalled replication forks in metazoans, causes synthetic lethality in third instar larvae lacking either PIF1 or the polymerase delta subunit POL32. Interestingly, pif1 mutants have a reduced ability to synthesize DNA during repair of a double-stranded gap, but only in the absence of POL32. Together, these results support a model in which Drosophila PIF1 functions with POL32 during times of replication stress but acts independently of POL32 to promote synthesis during double-strand gap repair.
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Affiliation(s)
- Ece Kocak
- Department of Biology, Tufts University, Medford, Massachusetts 02155
| | - Sarah Dykstra
- Department of Biology, Tufts University, Medford, Massachusetts 02155
| | - Alexandra Nemeth
- Department of Biology, Tufts University, Medford, Massachusetts 02155
| | | | - Kasey Rodgers
- Department of Biology, Tufts University, Medford, Massachusetts 02155
| | - Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts 02155
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15
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Bhandari J, Karg T, Golic KG. Homolog-Dependent Repair Following Dicentric Chromosome Breakage in Drosophila melanogaster. Genetics 2019; 212:615-630. [PMID: 31053594 PMCID: PMC6614899 DOI: 10.1534/genetics.119.302247] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Accepted: 04/29/2019] [Indexed: 12/11/2022] Open
Abstract
Double-strand DNA breaks are repaired by one of several mechanisms that rejoin two broken ends. However, cells are challenged when asked to repair a single broken end and respond by: (1) inducing programmed cell death; (2) healing the broken end by constructing a new telomere; (3) adapting to the broken end and resuming the mitotic cycle without repair; and (4) using information from the sister chromatid or homologous chromosome to restore a normal chromosome terminus. During one form of homolog-dependent repair in yeast, termed break-induced replication (BIR), a template chromosome can be copied for hundreds of kilobases. BIR efficiency depends on Pif1 helicase and Pol32, a nonessential subunit of DNA polymerase δ. To date, there is little evidence that BIR can be used for extensive chromosome repair in higher eukaryotes. We report that a dicentric chromosome broken in mitosis in the male germline of Drosophila melanogaster is usually repaired by healing, but can also be repaired in a homolog-dependent fashion, restoring at least 1.3 Mb of terminal sequence information. This mode of repair is significantly reduced in pif1 and pol32 mutants. Formally, the repaired chromosomes are recombinants. However, the absence of reciprocal recombinants and the dependence on Pif1 and Pol32 strongly support the hypothesis that BIR is the mechanism for restoration of the chromosome terminus. In contrast to yeast, pif1 mutants in Drosophila exhibit a reduced rate of chromosome healing, likely owing to fundamental differences in telomeres between these organisms.
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Affiliation(s)
- Jayaram Bhandari
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Travis Karg
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
| | - Kent G Golic
- School of Biological Sciences, University of Utah, Salt Lake City, Utah 84112
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16
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Wang Z, Song Y, Li S, Kurian S, Xiang R, Chiba T, Wu X. DNA polymerase θ (POLQ) is important for repair of DNA double-strand breaks caused by fork collapse. J Biol Chem 2019; 294:3909-3919. [PMID: 30655289 PMCID: PMC6422074 DOI: 10.1074/jbc.ra118.005188] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 01/05/2019] [Indexed: 12/31/2022] Open
Abstract
DNA polymerase θ (POLQ) plays an important role in alternative nonhomologous end joining or microhomology-mediated end joining (alt-NHEJ/MMEJ). Here, we show that POLQ is not only required for MMEJ to repair DNA double-strand breaks (DSBs) generated by endonucleases such as I-SceI or Cas9, but is also needed for repair of DSBs derived from DNA nicks generated by Cas9 nickase. Consistently, we found that POLQ deficiency leads to sensitivity to topoisomerase inhibitors that cause DNA single-strand break (SSB) accumulation at replication forks and to ATR inhibitors that induce replication fork collapse. These studies support the function of POLQ in coping with replication stress and repairing DSBs upon fork collapse. POLQ overexpression is present in many cancer types and is associated with poor prognosis, including breast cancer regardless of BRCA1 status. We provide proof-of-concept evidence to support a novel cancer treatment strategy that combines POLQ inhibition with administration of topoisomerase or ATR inhibitors, which induces replication stress and fork collapse. Given the prevalence of POLQ overexpression in tumors, such strategy may have a significant impact on developing targeted cancer treatment.
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Affiliation(s)
- Zi Wang
- From the Department of Molecular Medicine, Scripps Research Institute, La Jolla, California 92037
- the Biomedical Gerontology Laboratory, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa 359-1192, Japan
| | - Yadong Song
- From the Department of Molecular Medicine, Scripps Research Institute, La Jolla, California 92037
- the School of Medicine, Nankai University, 94 Weijin Road, Tianjin 300071, China, and
| | - Shibo Li
- From the Department of Molecular Medicine, Scripps Research Institute, La Jolla, California 92037
| | - Sunil Kurian
- the Division of Organ Transplant, Scripps Health, La Jolla, California 92037
| | - Rong Xiang
- the School of Medicine, Nankai University, 94 Weijin Road, Tianjin 300071, China, and
| | - Takuya Chiba
- the Biomedical Gerontology Laboratory, Faculty of Human Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa 359-1192, Japan
| | - Xiaohua Wu
- From the Department of Molecular Medicine, Scripps Research Institute, La Jolla, California 92037,
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17
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Kramara J, Osia B, Malkova A. Break-Induced Replication: The Where, The Why, and The How. Trends Genet 2018; 34:518-531. [PMID: 29735283 DOI: 10.1016/j.tig.2018.04.002] [Citation(s) in RCA: 171] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2017] [Revised: 02/27/2018] [Accepted: 04/05/2018] [Indexed: 01/07/2023]
Abstract
Break-induced replication (BIR) is a pathway that repairs one-ended double-strand breaks (DSBs). For decades, yeast model systems offered the only opportunities to study eukaryotic BIR. These studies described an unusual mode of BIR synthesis that is carried out by a migrating bubble and shows conservative inheritance of newly synthesized DNA, leading to genomic instabilities like those associated with cancer in humans. Yet, evidence of BIR functioning in mammals or during repair of other DNA breaks has been missing. Recent studies have uncovered multiple examples of BIR working in replication restart and repair of eroded telomeres in yeast and mammals, as well as some unexpected findings, including the RAD51 independence of BIR. Strong interest remains in determining the variations in molecular mechanisms that drive and regulate BIR in different genetic backgrounds, across organisms, and particularly in the context of human disease.
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Affiliation(s)
- J Kramara
- These authors contributed equally to this work
| | - B Osia
- These authors contributed equally to this work
| | - A Malkova
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA.
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18
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DNA Replication Control During Drosophila Development: Insights into the Onset of S Phase, Replication Initiation, and Fork Progression. Genetics 2017; 207:29-47. [PMID: 28874453 PMCID: PMC5586379 DOI: 10.1534/genetics.115.186627] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 05/19/2017] [Indexed: 12/11/2022] Open
Abstract
Proper control of DNA replication is critical to ensure genomic integrity during cell proliferation. In addition, differential regulation of the DNA replication program during development can change gene copy number to influence cell size and gene expression. Drosophila melanogaster serves as a powerful organism to study the developmental control of DNA replication in various cell cycle contexts in a variety of differentiated cell and tissue types. Additionally, Drosophila has provided several developmentally regulated replication models to dissect the molecular mechanisms that underlie replication-based copy number changes in the genome, which include differential underreplication and gene amplification. Here, we review key findings and our current understanding of the developmental control of DNA replication in the contexts of the archetypal replication program as well as of underreplication and differential gene amplification. We focus on the use of these latter two replication systems to delineate many of the molecular mechanisms that underlie the developmental control of replication initiation and fork elongation.
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19
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Rapid DNA Synthesis During Early Drosophila Embryogenesis Is Sensitive to Maternal Humpty Dumpty Protein Function. Genetics 2017; 207:935-947. [PMID: 28942426 DOI: 10.1534/genetics.117.300318] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 09/20/2017] [Indexed: 12/29/2022] Open
Abstract
Problems with DNA replication cause cancer and developmental malformations. It is not fully understood how DNA replication is coordinated with development and perturbed in disease. We had previously identified the Drosophila gene humpty dumpty (hd), and showed that null alleles cause incomplete DNA replication, tissue undergrowth, and lethality. Animals homozygous for the missense allele, hd272-9 , were viable, but adult females had impaired amplification of eggshell protein genes in the ovary, resulting in the maternal effects of thin eggshells and embryonic lethality. Here, we show that expression of an hd transgene in somatic cells of the ovary rescues amplification and eggshell synthesis but not embryo viability. The germline of these mothers remain mutant for the hd272-9 allele, resulting in reduced maternal Hd protein and embryonic arrest during mitosis of the first few S/M nuclear cleavage cycles with chromosome instability and chromosome bridges. Epistasis analysis of hd with the rereplication mutation plutonium indicates that the chromosome bridges of hd embryos are the result of a failed attempt to segregate incompletely replicated sister chromatids. This study reveals that maternally encoded Humpty dumpty protein is essential for DNA replication and genome integrity during the little-understood embryonic S/M cycles. Moreover, the two hd272-9 maternal-effect phenotypes suggest that ovarian gene amplification and embryonic cleavage are two time periods in development that are particularly sensitive to mild deficits in DNA replication function. This last observation has broader relevance for interpreting why mild mutations in the human ortholog of humpty dumpty and other DNA replication genes cause tissue-specific malformations of microcephalic dwarfisms.
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20
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Abstract
Replication forks encounter obstacles that must be repaired or bypassed to complete chromosome duplication before cell division. Proteomic analysis of replication forks suggests that the checkpoint and repair machinery travels with unperturbed forks, implying that they are poised to respond to stalling and collapse. However, impaired fork progression still generates aberrations, including repeat copy number instability and chromosome rearrangements. Deregulated origin firing also causes fork instability if a newer fork collides with an older one, generating double-strand breaks (DSBs) and partially rereplicated DNA. Current evidence suggests that multiple mechanisms are used to repair rereplication damage, yet these can have deleterious consequences for genome integrity.
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21
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Beagan K, Armstrong RL, Witsell A, Roy U, Renedo N, Baker AE, Schärer OD, McVey M. Drosophila DNA polymerase theta utilizes both helicase-like and polymerase domains during microhomology-mediated end joining and interstrand crosslink repair. PLoS Genet 2017; 13:e1006813. [PMID: 28542210 PMCID: PMC5466332 DOI: 10.1371/journal.pgen.1006813] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 06/09/2017] [Accepted: 05/12/2017] [Indexed: 11/20/2022] Open
Abstract
Double strand breaks (DSBs) and interstrand crosslinks (ICLs) are toxic DNA lesions that can be repaired through multiple pathways, some of which involve shared proteins. One of these proteins, DNA Polymerase θ (Pol θ), coordinates a mutagenic DSB repair pathway named microhomology-mediated end joining (MMEJ) and is also a critical component for bypass or repair of ICLs in several organisms. Pol θ contains both polymerase and helicase-like domains that are tethered by an unstructured central region. While the role of the polymerase domain in promoting MMEJ has been studied extensively both in vitro and in vivo, a function for the helicase-like domain, which possesses DNA-dependent ATPase activity, remains unclear. Here, we utilize genetic and biochemical analyses to examine the roles of the helicase-like and polymerase domains of Drosophila Pol θ. We demonstrate an absolute requirement for both polymerase and ATPase activities during ICL repair in vivo. However, similar to mammalian systems, polymerase activity, but not ATPase activity, is required for ionizing radiation-induced DSB repair. Using a site-specific break repair assay, we show that overall end-joining efficiency is not affected in ATPase-dead mutants, but there is a significant decrease in templated insertion events. In vitro, Pol θ can efficiently bypass a model unhooked nitrogen mustard crosslink and promote DNA synthesis following microhomology annealing, although ATPase activity is not required for these functions. Together, our data illustrate the functional importance of the helicase-like domain of Pol θ and suggest that its tethering to the polymerase domain is important for its multiple functions in DNA repair and damage tolerance. Error-prone DNA Polymerase θ (Pol θ) plays a conserved role in a mutagenic DNA double-strand break repair mechanism called microhomology-mediated end joining (MMEJ). In many organisms, it also participates in a process crucial to the removal/repair of DNA interstrand crosslinks. The exact mechanism by which Pol θ promotes these processes is unclear, but a clue may lie in its dual-domain structure. While the role of its polymerase domain has been well-studied, the function of its helicase-like domain remains an open question. Here we report an absolute requirement for ATPase activity of the helicase-like domain during interstrand crosslink repair in Drosophila melanogaster. We also find that although end joining frequency does not decrease in ATPase-dead mutants, ATPase activity is critical for generating templated insertions. Using purified Pol θ protein, we show that it can bypass synthetic substrates mimicking interstrand crosslink intermediates and can promote MMEJ-like reactions with partial double-stranded and single-stranded DNA. Together, these data demonstrate a novel function for the helicase-like domain of Pol θ in both interstrand crosslink repair and MMEJ and provide insight into why the dual-domain structure has been conserved throughout evolution.
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Affiliation(s)
- Kelly Beagan
- Department of Biology, Tufts University, Medford, Massachusetts
| | | | - Alice Witsell
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Upasana Roy
- Department of Chemistry and Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York, United States of America
| | - Nikolai Renedo
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Amy E. Baker
- Department of Biology, Tufts University, Medford, Massachusetts
| | - Orlando D. Schärer
- Department of Chemistry and Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York, United States of America
- Center for Genomic Integrity, Institute for Basic Science, Ulsan, Korea and Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology, Ulsan, Korea
| | - Mitch McVey
- Department of Biology, Tufts University, Medford, Massachusetts
- * E-mail:
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