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Medina-Suárez S, Ayra-Plasencia J, Pérez-Martínez L, Butter F, Machín F. Msc1 is a nuclear envelope protein that reinforces DNA repair in late mitosis. iScience 2024; 27:110250. [PMID: 39021806 PMCID: PMC11253511 DOI: 10.1016/j.isci.2024.110250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 04/15/2024] [Accepted: 06/08/2024] [Indexed: 07/20/2024] Open
Abstract
Precise double-strand break (DSB) repair is a paramount for genome stability. Homologous recombination (HR) repairs DSBs when cyclin-dependent kinase (CDK) activity is high, which correlates with the availability of the sister chromatid as a template. However, anaphase and telophase are paradoxical scenarios since high CDK favors HR despite sister chromatids being no longer aligned. To identify factors specifically involved in DSB repair in late mitosis, we have undertaken comparative proteomics in Saccharomyces cerevisiae and found that meiotic sister chromatid 1 (Msc1), a poorly characterized nuclear envelope protein, is significantly enriched upon both random and guided DSBs. We further show that Δmsc1 is more sensitive to DSBs in late mitosis, and has a delayed repair of DBSs, as indicated by increased Rad53 hyperphosphorylation, a higher presence of RPA foci, fewer Rad52 repair factories, and slower HR completion. We propose that Msc1 favors the later stages of HR and the timely completion of DSB repair before cytokinesis.
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Affiliation(s)
- Sara Medina-Suárez
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, 38200 San Cristóbal de La Laguna, Spain
| | - Jessel Ayra-Plasencia
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, 38200 San Cristóbal de La Laguna, Spain
| | | | - Falk Butter
- Institute of Molecular Biology (IMB), 55128 Mainz, Germany
- Institute of Molecular Virology and Cell Biology, Friedrich Loeffler Institute, 17493 Greifswald, Germany
| | - Félix Machín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, 38010 Santa Cruz de Tenerife, Spain
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, 38200 San Cristóbal de La Laguna, Spain
- Facultad de Ciencias de la Salud, Universidad Fernando Pessoa Canarias, 35450 Las Palmas de Gran Canaria, Spain
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2
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Maclay T, Whalen J, Johnson M, Freudenreich CH. The DNA Replication Checkpoint Targets the Kinetochore for Relocation of Collapsed Forks to the Nuclear Periphery. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.17.599319. [PMID: 38948692 PMCID: PMC11212917 DOI: 10.1101/2024.06.17.599319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Hairpin forming expanded CAG/CTG repeats pose significant challenges to DNA replication which can lead to replication fork collapse. Long CAG/CTG repeat tracts relocate to the nuclear pore complex to maintain their integrity. Forks impeded by DNA structures are known to activate the DNA damage checkpoint, thus we asked whether checkpoint proteins play a role in relocation of collapsed forks to the nuclear periphery in S. cerevisiae . We show that relocation of a (CAG/CTG) 130 tract is dependent on activation of the Mrc1/Rad53 replication checkpoint. Further, checkpoint-mediated phosphorylation of the kinetochore protein Cep3 is required for relocation, implicating detachment of the centromere from the spindle pole body. Activation of this pathway leads to DNA damage-induced microtubule recruitment to the repeat. These data suggest a role for the DNA replication checkpoint in facilitating movement of collapsed replication forks to the nuclear periphery by centromere release and microtubule-directed motion. Highlights The DNA replication checkpoint initiates relocation of a structure-forming CAG repeat tract to the nuclear pore complex (NPC)The importance of Mrc1 (hClaspin) implicates fork uncoupling as the initial checkpoint signalPhosphorylation of the Cep3 kinetochore protein by Dun1 kinase allows for centromere release, which is critical for collapsed fork repositioningDamage-inducible nuclear microtubules (DIMs) colocalize with the repeat locus and are required for relocation to the NPCEstablishes a new role for the DNA replication and DNA damage checkpoint response to trigger repositioning of collapsed forks within the nucleus.
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3
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Shokrollahi M, Stanic M, Hundal A, Chan JNY, Urman D, Jordan CA, Hakem A, Espin R, Hao J, Krishnan R, Maass PG, Dickson BC, Hande MP, Pujana MA, Hakem R, Mekhail K. DNA double-strand break-capturing nuclear envelope tubules drive DNA repair. Nat Struct Mol Biol 2024:10.1038/s41594-024-01286-7. [PMID: 38632359 DOI: 10.1038/s41594-024-01286-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Accepted: 03/25/2024] [Indexed: 04/19/2024]
Abstract
Current models suggest that DNA double-strand breaks (DSBs) can move to the nuclear periphery for repair. It is unclear to what extent human DSBs display such repositioning. Here we show that the human nuclear envelope localizes to DSBs in a manner depending on DNA damage response (DDR) kinases and cytoplasmic microtubules acetylated by α-tubulin acetyltransferase-1 (ATAT1). These factors collaborate with the linker of nucleoskeleton and cytoskeleton complex (LINC), nuclear pore complex (NPC) protein NUP153, nuclear lamina and kinesins KIF5B and KIF13B to generate DSB-capturing nuclear envelope tubules (dsbNETs). dsbNETs are partly supported by nuclear actin filaments and the circadian factor PER1 and reversed by kinesin KIFC3. Although dsbNETs promote repair and survival, they are also co-opted during poly(ADP-ribose) polymerase (PARP) inhibition to restrain BRCA1-deficient breast cancer cells and are hyper-induced in cells expressing the aging-linked lamin A mutant progerin. In summary, our results advance understanding of nuclear structure-function relationships, uncover a nuclear-cytoplasmic DDR and identify dsbNETs as critical factors in genome organization and stability.
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Affiliation(s)
- Mitra Shokrollahi
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Mia Stanic
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Anisha Hundal
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Princess Margaret Cancer Research Centre, University Health Network, Toronto, Ontario, Canada
| | - Janet N Y Chan
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Defne Urman
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Chris A Jordan
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Anne Hakem
- Princess Margaret Cancer Research Centre, University Health Network, Toronto, Ontario, Canada
| | - Roderic Espin
- ProCURE, Catalan Institute of Oncology, Oncobell, Bellvitge Institute for Biomedical Research (IDIBELL), L'Hospitalet del Llobregat, Barcelona, Spain
- Biomedical Research Network Centre in Respiratory Diseases (CIBERES), Instituto de Salud Carlos III, Madrid, Spain
| | - Jun Hao
- Princess Margaret Cancer Research Centre, University Health Network, Toronto, Ontario, Canada
| | - Rehna Krishnan
- Princess Margaret Cancer Research Centre, University Health Network, Toronto, Ontario, Canada
| | - Philipp G Maass
- Department of Molecular Genetics, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Genetics and Genome Biology Program, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Brendan C Dickson
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
- Lunenfeld Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Manoor P Hande
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Miquel A Pujana
- ProCURE, Catalan Institute of Oncology, Oncobell, Bellvitge Institute for Biomedical Research (IDIBELL), L'Hospitalet del Llobregat, Barcelona, Spain
- Biomedical Research Network Centre in Respiratory Diseases (CIBERES), Instituto de Salud Carlos III, Madrid, Spain
| | - Razqallah Hakem
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
- Princess Margaret Cancer Research Centre, University Health Network, Toronto, Ontario, Canada.
- Department of Medical Biophysics, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
| | - Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
- Temerty Centre for AI Research and Education in Medicine, University of Toronto, Toronto, Ontario, Canada.
- College of New Scholars, Artists and Scientists, Royal Society of Canada, Ottawa, Ontario, Canada.
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4
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Simon MN, Dubrana K, Palancade B. On the edge: how nuclear pore complexes rule genome stability. Curr Opin Genet Dev 2024; 84:102150. [PMID: 38215626 DOI: 10.1016/j.gde.2023.102150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/10/2023] [Accepted: 12/18/2023] [Indexed: 01/14/2024]
Abstract
Nuclear organization has emerged as a critical layer in the coordination of DNA repair activities. Distinct types of DNA lesions have notably been shown to relocate at the vicinity of nuclear pore complexes (NPCs), where specific repair pathways are favored, ultimately safeguarding genome integrity. Here, we review the most recent progress in this field, notably highlighting the increasingly diverse types of DNA structures undergoing repositioning, and the signaling pathways involved. We further discuss our growing knowledge of the molecular mechanisms underlying the choice of repair pathways at NPCs, and their conservation - or divergences. Intriguingly, a series of recent findings suggest that DNA metabolism may be coupled to NPC biogenesis and specialization, challenging our initial vision of these processes.
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Affiliation(s)
- Marie-Noëlle Simon
- Marseille Cancer Research Center (CRCM), U1068 Inserm, UMR7258 CNRS, Institut Paoli-Calmettes, Equipe Labélisée Ligue, Aix Marseille University, Marseille, France. https://twitter.com/@IJMonod
| | - Karine Dubrana
- Université Paris Cité, Inserm, CEA, Stabilité Génétique Cellules Souches et Radiations, F-92260 Fontenay-aux-Roses, France; Université Paris-Saclay, Inserm, CEA, Stabilité Génétique Cellules Souches et Radiations, F-92260 Fontenay-aux-Roses, France. https://twitter.com/@DubranaLab
| | - Benoit Palancade
- Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France.
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5
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González-Acosta D, Lopes M. DNA replication and replication stress response in the context of nuclear architecture. Chromosoma 2024; 133:57-75. [PMID: 38055079 PMCID: PMC10904558 DOI: 10.1007/s00412-023-00813-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/23/2023] [Accepted: 10/24/2023] [Indexed: 12/07/2023]
Abstract
The DNA replication process needs to be coordinated with other DNA metabolism transactions and must eventually extend to the full genome, regardless of chromatin status, gene expression, secondary structures and DNA lesions. Completeness and accuracy of DNA replication are crucial to maintain genome integrity, limiting transformation in normal cells and offering targeting opportunities for proliferating cancer cells. DNA replication is thus tightly coordinated with chromatin dynamics and 3D genome architecture, and we are only beginning to understand the underlying molecular mechanisms. While much has recently been discovered on how DNA replication initiation is organised and modulated in different genomic regions and nuclear territories-the so-called "DNA replication program"-we know much less on how the elongation of ongoing replication forks and particularly the response to replication obstacles is affected by the local nuclear organisation. Also, it is still elusive how specific components of nuclear architecture participate in the replication stress response. Here, we review known mechanisms and factors orchestrating replication initiation, and replication fork progression upon stress, focusing on recent evidence linking genome organisation and nuclear architecture with the cellular responses to replication interference, and highlighting open questions and future challenges to explore this exciting new avenue of research.
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Affiliation(s)
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
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6
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García Fernández F, Fabre E. The Dynamic Behavior of Chromatin in Response to DNA Double-Strand Breaks. Genes (Basel) 2022; 13:genes13020215. [PMID: 35205260 PMCID: PMC8872016 DOI: 10.3390/genes13020215] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 01/18/2022] [Accepted: 01/19/2022] [Indexed: 02/05/2023] Open
Abstract
The primary functions of the eukaryotic nucleus as a site for the storage, retrieval, and replication of information require a highly dynamic chromatin organization, which can be affected by the presence of DNA damage. In response to double-strand breaks (DSBs), the mobility of chromatin at the break site is severely affected and, to a lesser extent, that of other chromosomes. The how and why of such movement has been widely studied over the last two decades, leading to different mechanistic models and proposed potential roles underlying both local and global mobility. Here, we review the state of the knowledge on current issues affecting chromatin mobility upon DSBs, and highlight its role as a crucial step in the DNA damage response (DDR).
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Affiliation(s)
- Fabiola García Fernández
- Institut Curie, CNRS UMR3664, Sorbonne Université, F-75005 Paris, France
- Correspondence: (F.G.F.); (E.F.)
| | - Emmanuelle Fabre
- Génomes Biologie Cellulaire et Thérapeutiques, CNRS UMR7212, INSERM U944, Université de Paris, F-75010 Paris, France
- Correspondence: (F.G.F.); (E.F.)
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7
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Liakopoulos D. Coupling DNA Replication and Spindle Function in Saccharomyces cerevisiae. Cells 2021; 10:cells10123359. [PMID: 34943867 PMCID: PMC8699587 DOI: 10.3390/cells10123359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/24/2021] [Accepted: 11/27/2021] [Indexed: 12/02/2022] Open
Abstract
In the yeast Saccharomyces cerevisiae DNA replication and spindle assembly can overlap. Therefore, signaling mechanisms modulate spindle dynamics in order to ensure correct timing of chromosome segregation relative to genome duplication, especially when replication is incomplete or the DNA becomes damaged. This review focuses on the molecular mechanisms that coordinate DNA replication and spindle dynamics, as well as on the role of spindle-dependent forces in DNA repair. Understanding the coupling between genome duplication and spindle function in yeast cells can provide important insights into similar processes operating in other eukaryotic organisms, including humans.
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Affiliation(s)
- Dimitris Liakopoulos
- CRBM, Université de Montpellier, CNRS, 1919 Route de Mende, 34293 Montpellier, France;
- Laboratory of Biology, Faculty of Medicine, University of Ioannina, 45110 Ioannina, Greece
- University Research Center of loannina, University of Ioannina, 45110 Ioannina, Greece
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8
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Sebastian R, Aladjem MI, Oberdoerffer P. Encounters in Three Dimensions: How Nuclear Topology Shapes Genome Integrity. Front Genet 2021; 12:746380. [PMID: 34745220 PMCID: PMC8566435 DOI: 10.3389/fgene.2021.746380] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/08/2021] [Indexed: 11/13/2022] Open
Abstract
Almost 25 years ago, the phosphorylation of a chromatin component, histone H2AX, was discovered as an integral part of the DNA damage response in eukaryotes. Much has been learned since then about the control of DNA repair in the context of chromatin. Recent technical and computational advances in imaging, biophysics and deep sequencing have led to unprecedented insight into nuclear organization, highlighting the impact of three-dimensional (3D) chromatin structure and nuclear topology on DNA repair. In this review, we will describe how DNA repair processes have adjusted to and in many cases adopted these organizational features to ensure accurate lesion repair. We focus on new findings that highlight the importance of chromatin context, topologically associated domains, phase separation and DNA break mobility for the establishment of repair-conducive nuclear environments. Finally, we address the consequences of aberrant 3D genome maintenance for genome instability and disease.
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Affiliation(s)
- Robin Sebastian
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, United States
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD, United States
| | - Philipp Oberdoerffer
- Division of Cancer Biology, National Cancer Institute, NIH, Rockville, MD, United States
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9
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STING protects breast cancer cells from intrinsic and genotoxic-induced DNA instability via a non-canonical, cell-autonomous pathway. Oncogene 2021; 40:6627-6640. [PMID: 34625708 DOI: 10.1038/s41388-021-02037-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 09/13/2021] [Accepted: 09/23/2021] [Indexed: 01/13/2023]
Abstract
STING (Stimulator of Interferon Genes) is an endoplasmic reticulum-anchored adaptor of the innate immunity best known to trigger pro-inflammatory cytokine expression in response to pathogen infection. In cancer, this canonical pathway can be activated by intrinsic or drug-induced genomic instability, potentiating antitumor immune responses. Here we report that STING downregulation decreases cell survival and increases sensitivity to genotoxic treatment in a panel of breast cancer cell lines in a cell-autonomous manner. STING silencing impaired DNA Damage Response (53BP1) foci formation and increased DNA break accumulation. These newly identified properties were found to be independent of STING partner cGAS and of its canonical pro-inflammatory pathway. STING was shown to partially localize at the inner nuclear membrane in a variety of breast cancer cell models and clinical tumor samples. Interactomics analysis of nuclear STING identified several proteins of the DNA Damage Response, including the three proteins of the DNA-PK complex, further supporting a role of STING in the regulation of genomic stability. In breast and ovarian cancer patients that received adjuvant chemotherapy, high STING expression is associated with increased risk of relapse. In summary, this study highlights an alternative, non-canonical tumor-promoting role of STING that opposes its well-documented function in tumor immunosurveillance.
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10
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Stanic M, Mekhail K. Integration of DNA damage responses with dynamic spatial genome organization. Trends Genet 2021; 38:290-304. [PMID: 34598804 DOI: 10.1016/j.tig.2021.08.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 08/26/2021] [Accepted: 08/31/2021] [Indexed: 11/28/2022]
Abstract
The maintenance of genome stability and cellular homeostasis depends on the temporal and spatial coordination of successive events constituting the classical DNA damage response (DDR). Recent findings suggest close integration and coordination of DDR signaling with specific cellular processes. The mechanisms underlying such coordination remain unclear. We review emerging crosstalk between DNA repair factors, chromatin remodeling, replication, transcription, spatial genome organization, cytoskeletal forces, and liquid-liquid phase separation (LLPS) in mediating DNA repair. We present an overarching DNA repair framework within which these dynamic processes intersect in nuclear space over time. Collectively, this interplay ensures the efficient assembly of DNA repair proteins onto shifting genome structures to preserve genome stability and cell survival.
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Affiliation(s)
- Mia Stanic
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, MaRS Centre, West Tower, 661 University Avenue, Toronto, ON M5G 1M1, Canada
| | - Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, Temerty Faculty of Medicine, University of Toronto, MaRS Centre, West Tower, 661 University Avenue, Toronto, ON M5G 1M1, Canada; Canada Research Chairs Program, Temerty Faculty of Medicine, University of Toronto, Medical Sciences Building, 1 King's College Circle, Toronto, ON M5S 1A8, Canada.
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11
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Saito Y, Kimura W. Roles of Phase Separation for Cellular Redox Maintenance. Front Genet 2021; 12:691946. [PMID: 34306032 PMCID: PMC8299301 DOI: 10.3389/fgene.2021.691946] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/04/2021] [Indexed: 12/12/2022] Open
Abstract
The oxidation reaction greatly alters characteristics of various cellular components. In exchange for efficient energy production, mitochondrial aerobic respiration substantially increases the risk of excess oxidation of cellular biomolecules such as lipids, proteins, nucleic acids, and numerous small molecules. To maintain a physiologically balanced cellular reduction-oxidation (redox) state, cells utilize a variety of molecular machineries including cellular antioxidants and protein degradation complexes such as the ubiquitin-proteasome system or autophagy. In the past decade, biomolecular liquid-liquid phase separation (LLPS) has emerged as a subject of great interest in the biomedical field, as it plays versatile roles in the maintenance of cellular homeostasis. With regard to redox homeostasis, LLPS arose as a major player in both well-characterized and newly emerging redox pathways. LLPS is involved in direct redox imbalance sensing, signal transduction, and transcriptional regulation. Also, LLPS is at play when cells resist redox imbalance through metabolic switching, translational remodeling, activating the DNA damage response, and segregation of vulnerable lipids and proteins. On the other hand, chronic accumulation of phase-separated molecular condensates such as lipid droplets and amyloid causes neurotoxic outcomes. In this review we enumerate recent progress on understanding how cells utilize LLPS to deal with oxidative stress, especially related to cell survival or pathogenesis, and we discuss future research directions for understanding biological phase separation in cellular redox regulation.
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Affiliation(s)
- Yuichi Saito
- Laboratory for Heart Regeneration, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Wataru Kimura
- Laboratory for Heart Regeneration, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
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12
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Lamm N, Rogers S, Cesare AJ. Chromatin mobility and relocation in DNA repair. Trends Cell Biol 2021; 31:843-855. [PMID: 34183232 DOI: 10.1016/j.tcb.2021.06.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 06/02/2021] [Accepted: 06/03/2021] [Indexed: 01/17/2023]
Abstract
The nucleus is a dynamic environment containing chromatin, membraneless organelles, and specialized molecular structures at the nuclear membrane. Within the spectrum of DNA repair activities are observations of increased mobility of damaged chromatin and the displacement of DNA lesions to specific nuclear environments. Here, we focus on the role that nuclear-specific filamentous actin plays in mobilizing damaged chromatin in response to DNA double-strand breaks and replication stress. We also examine nuclear pore complexes and promyelocytic leukemia-nuclear bodies as specialized platforms for homology-directed repair. The literature suggests an emerging model where specific types of DNA lesions are subjected to nuclear-derived forces that mobilize damaged chromatin and promote interaction with repair hubs to facilitate specialized repair reactions.
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Affiliation(s)
- Noa Lamm
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia
| | - Samuel Rogers
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia
| | - Anthony J Cesare
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia.
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13
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Impacts of chromatin dynamics and compartmentalization on DNA repair. DNA Repair (Amst) 2021; 105:103162. [PMID: 34182258 DOI: 10.1016/j.dnarep.2021.103162] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 06/10/2021] [Accepted: 06/17/2021] [Indexed: 11/22/2022]
Abstract
The proper spatial organization of DNA, RNA, and proteins is critical for a variety of cellular processes. The genome is organized into numerous functional units, such as topologically associating domains (TADs), the formation of which is regulated by both proteins and RNA. In addition, a group of chromatin-bound proteins with the ability to undergo liquid-liquid phase separation (LLPS) can affect the spatial organization and compartmentalization of chromatin, RNA, and proteins by forming condensates, conferring unique properties to specific chromosomal regions. Although the regulation of DNA repair by histone modifications and chromatin accessibility is well established, the impacts of higher-order chromatin and protein organization on the DNA damage response (DDR) have not been appreciated until recently. In this review, we will focus on the movement of chromatin during the DDR, the compartmentalization of DDR proteins via LLPS, and the roles of membraneless nuclear bodies and transcription in DNA repair. With this backdrop, we will discuss the importance of the spatial organization of chromatin and proteins for the maintenance of genome integrity.
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14
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The nuclear kinesin KIF18B promotes 53BP1-mediated DNA double-strand break repair. Cell Rep 2021; 35:109306. [PMID: 34192545 DOI: 10.1016/j.celrep.2021.109306] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 04/29/2021] [Accepted: 06/03/2021] [Indexed: 12/13/2022] Open
Abstract
53BP1 is recruited to chromatin in the vicinity of DNA double-strand breaks (DSBs). We identify the nuclear kinesin, KIF18B, as a 53BP1-interacting protein and define its role in 53BP1-mediated DSB repair. KIF18B is a molecular motor protein involved in destabilizing astral microtubules during mitosis. It is primarily nuclear throughout the interphase and is constitutively chromatin bound. Our observations indicate a nuclear function during the interphase for a kinesin previously implicated in mitosis. We identify a central motif in KIF18B, which we term the Tudor-interacting motif (TIM), because of its interaction with the Tudor domain of 53BP1. TIM enhances the interaction between the 53BP1 Tudor domain and dimethylated lysine 20 of histone H4. TIM and the motor function of KIF18B are both required for efficient 53BP1 focal recruitment in response to damage and for fusion of dysfunctional telomeres. Our data suggest a role for KIF18B in efficient 53BP1-mediated end-joining of DSBs.
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15
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Whalen JM, Dhingra N, Wei L, Zhao X, Freudenreich CH. Relocation of Collapsed Forks to the Nuclear Pore Complex Depends on Sumoylation of DNA Repair Proteins and Permits Rad51 Association. Cell Rep 2021; 31:107635. [PMID: 32402281 DOI: 10.1016/j.celrep.2020.107635] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 01/07/2020] [Accepted: 04/21/2020] [Indexed: 10/24/2022] Open
Abstract
Expanded CAG repeats form stem-loop secondary structures that lead to fork stalling and collapse. Previous work has shown that these collapsed forks relocalize to nuclear pore complexes (NPCs) in late S phase in a manner dependent on replication, the nucleoporin Nup84, and the Slx5 protein, which prevents repeat fragility and instability. Here, we show that binding of the Smc5/6 complex to the collapsed fork triggers Mms21-dependent sumoylation of fork-associated DNA repair proteins, and that RPA, Rad52, and Rad59 are the key sumoylation targets that mediate relocation. The SUMO interacting motifs of Slx5 target collapsed forks to the NPC. Notably, Rad51 foci only co-localize with the repeat after it is anchored to the nuclear periphery and Rad51 exclusion from the early collapsed fork is dependent on RPA sumoylation. This pathway may provide a mechanism to constrain recombination at stalled or collapsed forks until it is required for fork restart.
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Affiliation(s)
- Jenna M Whalen
- Department of Biology, Tufts University, Medford, MA 02155, USA
| | - Nalini Dhingra
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Lei Wei
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Xiaolan Zhao
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Catherine H Freudenreich
- Department of Biology, Tufts University, Medford, MA 02155, USA; Program in Genetics, Tufts University, Boston, MA 02111, USA.
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16
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Shokrollahi M, Mekhail K. Interphase microtubules in nuclear organization and genome maintenance. Trends Cell Biol 2021; 31:721-731. [PMID: 33902985 DOI: 10.1016/j.tcb.2021.03.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 03/10/2021] [Accepted: 03/23/2021] [Indexed: 12/11/2022]
Abstract
Microtubules are major cytoskeletal components mediating fundamental cellular processes, including cell division. Recent evidence suggests that microtubules also regulate the nucleus during the cell cycle's interphase stage. Deciphering such roles of microtubules should uncover direct crosstalk between the nucleus and cytoplasm, impacting genome function and organismal health. Here, we review emerging roles for microtubules in interphase genome regulation. We explore how microtubules exert cytoplasmic forces on the nucleus or transport molecular cargo, including DNA, into or within the nucleus. We also describe how microtubules perform these functions by establishing transient or stable connections with nuclear envelope elements. Lastly, we discuss how the regulation of the nucleus by microtubules impacts genome organization and repair. Together, the literature indicates that interphase microtubules are critical regulators of nuclear structure and genome stability.
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Affiliation(s)
- Mitra Shokrollahi
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Canada Research Chairs Program, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
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17
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Mackenroth B, Alani E. Collaborations between chromatin and nuclear architecture to optimize DNA repair fidelity. DNA Repair (Amst) 2021; 97:103018. [PMID: 33285474 PMCID: PMC8486310 DOI: 10.1016/j.dnarep.2020.103018] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 10/18/2020] [Accepted: 11/05/2020] [Indexed: 01/22/2023]
Abstract
Homologous recombination (HR), considered the highest fidelity DNA double-strand break (DSB) repair pathway that a cell possesses, is capable of repairing multiple DSBs without altering genetic information. However, in "last resort" scenarios, HR can be directed to low fidelity subpathways which often use non-allelic donor templates. Such repair mechanisms are often highly mutagenic and can also yield chromosomal rearrangements and/or deletions. While the choice between HR and its less precise counterpart, non-homologous end joining (NHEJ), has received much attention, less is known about how cells manage and prioritize HR subpathways. In this review, we describe work focused on how chromatin and nuclear architecture orchestrate subpathway choice and repair template usage to maintain genome integrity without sacrificing cell survival. Understanding the relationships between nuclear architecture and recombination mechanics will be critical to understand these cellular repair decisions.
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Affiliation(s)
- Beata Mackenroth
- Department of Molecular Biology and Genetics, Cornell University, 459 Biotechnology Building, Ithaca, NY, 14853-2703, United States
| | - Eric Alani
- Department of Molecular Biology and Genetics, Cornell University, 459 Biotechnology Building, Ithaca, NY, 14853-2703, United States.
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18
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Nuclear F-actin counteracts nuclear deformation and promotes fork repair during replication stress. Nat Cell Biol 2020; 22:1460-1470. [PMID: 33257806 DOI: 10.1038/s41556-020-00605-6] [Citation(s) in RCA: 72] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 10/26/2020] [Indexed: 12/25/2022]
Abstract
Filamentous actin (F-actin) provides cells with mechanical support and promotes the mobility of intracellular structures. Although F-actin is traditionally considered to be cytoplasmic, here we reveal that nuclear F-actin participates in the replication stress response. Using live and super-resolution imaging, we find that nuclear F-actin is polymerized in response to replication stress through a pathway regulated by ATR-dependent activation of mTORC1, and nucleation through IQGAP1, WASP and ARP2/3. During replication stress, nuclear F-actin increases the nuclear volume and sphericity to counteract nuclear deformation. Furthermore, F-actin and myosin II promote the mobility of stressed-replication foci to the nuclear periphery through increasingly diffusive motion and directed movements along the nuclear actin filaments. These actin functions promote replication stress repair and suppress chromosome and mitotic abnormalities. Moreover, we find that nuclear F-actin is polymerized in vivo in xenograft tumours after treatment with replication-stress-inducing chemotherapeutic agents, indicating that this pathway has a role in human disease.
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19
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The nuclear pore primes recombination-dependent DNA synthesis at arrested forks by promoting SUMO removal. Nat Commun 2020; 11:5643. [PMID: 33159083 PMCID: PMC7648084 DOI: 10.1038/s41467-020-19516-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 10/16/2020] [Indexed: 12/31/2022] Open
Abstract
Nuclear Pore complexes (NPCs) act as docking sites to anchor particular DNA lesions facilitating DNA repair by elusive mechanisms. Using replication fork barriers in fission yeast, we report that relocation of arrested forks to NPCs occurred after Rad51 loading and its enzymatic activity. The E3 SUMO ligase Pli1 acts at arrested forks to safeguard integrity of nascent strands and generates poly-SUMOylation which promote relocation to NPCs but impede the resumption of DNA synthesis by homologous recombination (HR). Anchorage to NPCs allows SUMO removal by the SENP SUMO protease Ulp1 and the proteasome, promoting timely resumption of DNA synthesis. Preventing Pli1-mediated SUMO chains was sufficient to bypass the need for anchorage to NPCs and the inhibitory effect of poly-SUMOylation on HR-mediated DNA synthesis. Our work establishes a novel spatial control of Recombination-Dependent Replication (RDR) at a unique sequence that is distinct from mechanisms engaged at collapsed-forks and breaks within repeated sequences. In yeast, collapsed forks shift to the nuclear periphery to associate with two distinct perinuclear anchorage sites such as the nuclear pore complex. Here, the authors reveal the mechanisms engaged at nuclear pore complex facilitating fork integrity and restart via SUMO regulation.
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20
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Cheblal A, Challa K, Seeber A, Shimada K, Yoshida H, Ferreira HC, Amitai A, Gasser SM. DNA Damage-Induced Nucleosome Depletion Enhances Homology Search Independently of Local Break Movement. Mol Cell 2020; 80:311-326.e4. [PMID: 32970994 DOI: 10.1016/j.molcel.2020.09.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 08/31/2020] [Accepted: 08/31/2020] [Indexed: 01/02/2023]
Abstract
To determine whether double-strand break (DSB) mobility enhances the physical search for an ectopic template during homology-directed repair (HDR), we tested the effects of factors that control chromatin dynamics, including cohesin loading and kinetochore anchoring. The former but not the latter is altered in response to DSBs. Loss of the nonhistone high-mobility group protein Nhp6 reduces histone occupancy and increases chromatin movement, decompaction, and ectopic HDR. The loss of nucleosome remodeler INO80-C did the opposite. To see whether enhanced HDR depends on DSB mobility or the global chromatin response, we tested the ubiquitin ligase mutant uls1Δ, which selectively impairs local but not global movement in response to a DSB. Strand invasion occurs in uls1Δ cells with wild-type kinetics, arguing that global histone depletion rather than DSB movement is rate limiting for HDR. Impaired break movement in uls1Δ correlates with elevated MRX and cohesin loading, despite normal resection and checkpoint activation.
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Affiliation(s)
- Anaïs Cheblal
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland; University of Basel, Faculty of Natural Sciences, 4056 Basel, Switzerland
| | - Kiran Challa
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Andrew Seeber
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland; Present address: Center for Advanced Imaging, Northwest Building, 52 Oxford St, Suite 147, Harvard University, Cambridge, MA 02138, USA
| | - Kenji Shimada
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Haruka Yoshida
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Helder C Ferreira
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland; Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - Assaf Amitai
- Department of Chemical Engineering, Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, USA; The Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA
| | - Susan M Gasser
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland; University of Basel, Faculty of Natural Sciences, 4056 Basel, Switzerland.
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21
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Sakuma S, Raices M, Borlido J, Guglielmi V, Zhu EYS, D'Angelo MA. Inhibition of Nuclear Pore Complex Formation Selectively Induces Cancer Cell Death. Cancer Discov 2020; 11:176-193. [PMID: 32988961 DOI: 10.1158/2159-8290.cd-20-0581] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 08/03/2020] [Accepted: 09/15/2020] [Indexed: 12/13/2022]
Abstract
Nuclear pore complexes (NPC) are the central mediators of nucleocytoplasmic transport. Increasing evidence shows that many cancer cells have increased numbers of NPCs and become addicted to the nuclear transport machinery. How reducing NPC numbers affects the physiology of normal and cancer cells and whether it could be exploited for cancer therapies has not been investigated. We report that inhibition of NPC formation, a process mostly restricted to proliferating cells, causes selective cancer cell death, prevents tumor growth, and induces tumor regression. Although cancer cells die in response to NPC assembly inhibition, normal cells undergo a reversible cell-cycle arrest that allows them to survive. Mechanistically, reducing NPC numbers results in multiple alterations contributing to cancer cell death, including abnormalities in nuclear transport, catastrophic alterations in gene expression, and the selective accumulation of DNA damage. Our findings uncover the NPC formation process as a novel targetable pathway in cancer cells. SIGNIFICANCE: Reducing NPC numbers in cancer cells induces death, prevents tumor growth, and results in tumor regression. Conversely, normal cells undergo a reversible cell-cycle arrest in response to inhibition of NPC assembly. These findings expose the potential of targeting NPC formation in cancer.This article is highlighted in the In This Issue feature, p. 1.
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Affiliation(s)
- Stephen Sakuma
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Marcela Raices
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Joana Borlido
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Valeria Guglielmi
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Ethan Y S Zhu
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California
| | - Maximiliano A D'Angelo
- Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California. NCI-Designated Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.
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22
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Miné-Hattab J, Chiolo I. Complex Chromatin Motions for DNA Repair. Front Genet 2020; 11:800. [PMID: 33061931 PMCID: PMC7481375 DOI: 10.3389/fgene.2020.00800] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/06/2020] [Indexed: 12/26/2022] Open
Abstract
A number of studies across different model systems revealed that chromatin undergoes significant changes in dynamics in response to DNA damage. These include local motion changes at damage sites, increased nuclear exploration of both damaged and undamaged loci, and directed motions to new nuclear locations associated with certain repair pathways. These studies also revealed the need for new analytical methods to identify directed motions in a context of mixed trajectories, and the importance of investigating nuclear dynamics over different time scales to identify diffusion regimes. Here we provide an overview of the current understanding of this field, including imaging and analytical methods developed to investigate nuclear dynamics in different contexts. These dynamics are essential for genome integrity. Identifying the molecular mechanisms responsible for these movements is key to understanding how their misregulation contributes to cancer and other genome instability disorders.
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Affiliation(s)
- Judith Miné-Hattab
- UMR 3664, CNRS, Institut Curie, PSL Research University, Paris, France
- UMR 3664, CNRS, Institut Curie, Sorbonne Université, Paris, France
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, United States
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23
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Whalen JM, Freudenreich CH. Location, Location, Location: The Role of Nuclear Positioning in the Repair of Collapsed Forks and Protection of Genome Stability. Genes (Basel) 2020; 11:E635. [PMID: 32526925 PMCID: PMC7348918 DOI: 10.3390/genes11060635] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 05/29/2020] [Accepted: 06/04/2020] [Indexed: 12/14/2022] Open
Abstract
Components of the nuclear pore complex (NPC) have been shown to play a crucial role in protecting against replication stress, and recovery from some types of stalled or collapsed replication forks requires movement of the DNA to the NPC in order to maintain genome stability. The role that nuclear positioning has on DNA repair has been investigated in several systems that inhibit normal replication. These include structure forming sequences (expanded CAG repeats), protein mediated stalls (replication fork barriers (RFBs)), stalls within the telomere sequence, and the use of drugs known to stall or collapse replication forks (HU + MMS or aphidicolin). Recently, the mechanism of relocation for collapsed replication forks to the NPC has been elucidated. Here, we will review the types of replication stress that relocate to the NPC, the current models for the mechanism of relocation, and the currently known protective effects of this movement.
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Affiliation(s)
- Jenna M. Whalen
- Department of Biology, Tufts University, Medford, MA 02155, USA;
| | - Catherine H. Freudenreich
- Department of Biology, Tufts University, Medford, MA 02155, USA;
- Program in Genetics, Tufts University, Boston, MA 02111, USA
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24
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Mladenov E, Staudt C, Soni A, Murmann-Konda T, Siemann-Loekes M, Iliakis G. Strong suppression of gene conversion with increasing DNA double-strand break load delimited by 53BP1 and RAD52. Nucleic Acids Res 2020; 48:1905-1924. [PMID: 31832684 PMCID: PMC7038941 DOI: 10.1093/nar/gkz1167] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 10/30/2019] [Accepted: 12/11/2019] [Indexed: 02/06/2023] Open
Abstract
In vertebrates, genomic DNA double-strand breaks (DSBs) are removed by non-homologous end-joining processes: classical non-homologous end-joining (c-NHEJ) and alternative end-joining (alt-EJ); or by homology-dependent processes: gene-conversion (GC) and single-strand annealing (SSA). Surprisingly, these repair pathways are not real alternative options restoring genome integrity with equal efficiency, but show instead striking differences in speed, accuracy and cell-cycle-phase dependence. As a consequence, engagement of one pathway may be associated with processing-risks for the genome absent from another pathway. Characterization of engagement-parameters and their consequences is, therefore, essential for understanding effects on the genome of DSB-inducing agents, such as ionizing-radiation (IR). Here, by addressing pathway selection in G2-phase, we discover regulatory confinements in GC with consequences for SSA- and c-NHEJ-engagement. We show pronounced suppression of GC with increasing DSB-load that is not due to RAD51 availability and which is delimited but not defined by 53BP1 and RAD52. Strikingly, at low DSB-loads, GC repairs ∼50% of DSBs, whereas at high DSB-loads its contribution is undetectable. Notably, with increasing DSB-load and the associated suppression of GC, SSA gains ground, while alt-EJ is suppressed. These observations explain earlier, apparently contradictory results and advance our understanding of logic and mechanisms underpinning the wiring between DSB repair pathways.
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Affiliation(s)
- Emil Mladenov
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Christian Staudt
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Aashish Soni
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Tamara Murmann-Konda
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - Maria Siemann-Loekes
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
| | - George Iliakis
- Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, Essen, Germany
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25
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Oshidari R, Mekhail K, Seeber A. Mobility and Repair of Damaged DNA: Random or Directed? Trends Cell Biol 2020; 30:144-156. [DOI: 10.1016/j.tcb.2019.11.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/14/2019] [Accepted: 11/15/2019] [Indexed: 12/24/2022]
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26
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Zhu S, Paydar M, Wang F, Li Y, Wang L, Barrette B, Bessho T, Kwok BH, Peng A. Kinesin Kif2C in regulation of DNA double strand break dynamics and repair. eLife 2020; 9:53402. [PMID: 31951198 PMCID: PMC7012618 DOI: 10.7554/elife.53402] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2019] [Accepted: 01/16/2020] [Indexed: 12/12/2022] Open
Abstract
DNA double strand breaks (DSBs) have detrimental effects on cell survival and genomic stability, and are related to cancer and other human diseases. In this study, we identified microtubule-depolymerizing kinesin Kif2C as a protein associated with DSB-mimicking DNA templates and known DSB repair proteins in Xenopus egg extracts and mammalian cells. The recruitment of Kif2C to DNA damage sites was dependent on both PARP and ATM activities. Kif2C knockdown or knockout led to accumulation of endogenous DNA damage, DNA damage hypersensitivity, and reduced DSB repair via both NHEJ and HR. Interestingly, Kif2C depletion, or inhibition of its microtubule depolymerase activity, reduced the mobility of DSBs, impaired the formation of DNA damage foci, and decreased the occurrence of foci fusion and resolution. Taken together, our study established Kif2C as a new player of the DNA damage response, and presented a new mechanism that governs DSB dynamics and repair.
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Affiliation(s)
- Songli Zhu
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Omaha, United States
| | - Mohammadjavad Paydar
- Institute for Research in Immunology and Cancer (IRIC), Département de médecine, Université de Montréal, Montréal, Canada
| | - Feifei Wang
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Omaha, United States.,Institute of Physical Science and Information Technology, Anhui University, Hefei, China
| | - Yanqiu Li
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Omaha, United States
| | - Ling Wang
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Omaha, United States
| | - Benoit Barrette
- Institute for Research in Immunology and Cancer (IRIC), Département de médecine, Université de Montréal, Montréal, Canada
| | - Tadayoshi Bessho
- Eppley Institute for Research in Cancer and Allied Diseases, Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center, Omaha, United States
| | - Benjamin H Kwok
- Institute for Research in Immunology and Cancer (IRIC), Département de médecine, Université de Montréal, Montréal, Canada
| | - Aimin Peng
- Department of Oral Biology, College of Dentistry, University of Nebraska Medical Center, Omaha, United States
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27
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Khosraviani N, Ostrowski LA, Mekhail K. Roles for Non-coding RNAs in Spatial Genome Organization. Front Cell Dev Biol 2019; 7:336. [PMID: 31921848 PMCID: PMC6930868 DOI: 10.3389/fcell.2019.00336] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 11/29/2019] [Indexed: 12/15/2022] Open
Abstract
Genetic loci are non-randomly arranged in the nucleus of the cell. This order, which is important to overall genome expression and stability, is maintained by a growing number of factors including the nuclear envelope, various genetic elements and dedicated protein complexes. Here, we review evidence supporting roles for non-coding RNAs (ncRNAs) in the regulation of spatial genome organization and its impact on gene expression and cell survival. Specifically, we discuss how ncRNAs from single-copy and repetitive DNA loci contribute to spatial genome organization by impacting perinuclear chromosome tethering, major nuclear compartments, chromatin looping, and various chromosomal structures. Overall, our analysis of the literature highlights central functions for ncRNAs and their transcription in the modulation of spatial genome organization with connections to human health and disease.
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Affiliation(s)
- Negin Khosraviani
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Lauren A. Ostrowski
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
- Canada Research Chairs Program, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
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28
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Gaillard H, Santos-Pereira JM, Aguilera A. The Nup84 complex coordinates the DNA damage response to warrant genome integrity. Nucleic Acids Res 2019; 47:4054-4067. [PMID: 30715474 PMCID: PMC6486642 DOI: 10.1093/nar/gkz066] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 01/24/2019] [Accepted: 01/25/2019] [Indexed: 02/07/2023] Open
Abstract
DNA lesions interfere with cellular processes such as transcription and replication and need to be adequately resolved to warrant genome integrity. Beyond their primary role in molecule transport, nuclear pore complexes (NPCs) function in other processes such as transcription, nuclear organization and DNA double strand break (DSB) repair. Here we found that the removal of UV-induced DNA lesions by nucleotide excision repair (NER) is compromised in the absence of the Nup84 nuclear pore component. Importantly, nup84Δ cells show an exacerbated sensitivity to UV in early S phase and delayed replication fork progression, suggesting that unrepaired spontaneous DNA lesions persist during S phase. In addition, nup84Δ cells are defective in the repair of replication-born DSBs by sister chromatid recombination (SCR) and rely on post-replicative repair functions for normal proliferation, indicating dysfunctions in the cellular pathways that enable replication on damaged DNA templates. Altogether, our data reveal a central role of the NPC in the DNA damage response to facilitate replication progression through damaged DNA templates by promoting efficient NER and SCR and preventing chromosomal rearrangements.
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Affiliation(s)
- Hélène Gaillard
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, 41092 Seville, Spain
| | - José M Santos-Pereira
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, 41092 Seville, Spain
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa-CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, 41092 Seville, Spain
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29
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Asymmetric Processing of DNA Ends at a Double-Strand Break Leads to Unconstrained Dynamics and Ectopic Translocation. Cell Rep 2019; 24:2614-2628.e4. [PMID: 30184497 DOI: 10.1016/j.celrep.2018.07.102] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 06/07/2018] [Accepted: 07/27/2018] [Indexed: 01/10/2023] Open
Abstract
Multiple pathways regulate the repair of double-strand breaks (DSBs) to suppress potentially dangerous ectopic recombination. Both sequence and chromatin context are thought to influence pathway choice between non-homologous end-joining (NHEJ) and homology-driven recombination. To test the effect of repetitive sequences on break processing, we have inserted TG-rich repeats on one side of an inducible DSB at the budding yeast MAT locus on chromosome III. Five clustered Rap1 sites within a break-proximal TG repeat are sufficient to block Mre11-Rad50-Xrs2 recruitment, impair resection, and favor elongation by telomerase. The two sides of the break lose end-to-end tethering and show enhanced, uncoordinated movement. Only the TG-free side is resected and shifts to the nuclear periphery. In contrast to persistent DSBs without TG repeats that are repaired by imprecise NHEJ, nearly all survivors of repeat-proximal DSBs repair the break by a homology-driven, non-reciprocal translocation from ChrIII-R to ChrVII-L. This suppression of imprecise NHEJ at TG-repeat-flanked DSBs requires the Uls1 translocase activity.
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30
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Morillo-Huesca M, Murillo-Pineda M, Barrientos-Moreno M, Gómez-Marín E, Clemente-Ruiz M, Prado F. Actin and Nuclear Envelope Components Influence Ectopic Recombination in the Absence of Swr1. Genetics 2019; 213:819-834. [PMID: 31533921 PMCID: PMC6827384 DOI: 10.1534/genetics.119.302580] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 09/17/2019] [Indexed: 12/11/2022] Open
Abstract
The accuracy of most DNA processes depends on chromatin integrity and dynamics. Our analyses in the yeast Saccharomyces cerevisiae show that an absence of Swr1 (the catalytic and scaffold subunit of the chromatin-remodeling complex SWR) leads to the formation of long-duration Rad52, but not RPA, foci and to an increase in intramolecular recombination. These phenotypes are further increased by MMS, zeocin, and ionizing radiation, but not by double-strand breaks, HU, or transcription/replication collisions, suggesting that they are associated with specific DNA lesions. Importantly, these phenotypes can be specifically suppressed by mutations in: (1) chromatin-anchorage internal nuclear membrane components (mps3∆75-150 and src1∆); (2) actin and actin regulators (act1-157, act1-159, crn1∆, and cdc42-6); or (3) the SWR subunit Swc5 and the SWR substrate Htz1 However, they are not suppressed by global disruption of actin filaments or by the absence of Csm4 (a component of the external nuclear membrane that forms a bridging complex with Mps3, thus connecting the actin cytoskeleton with chromatin). Moreover, swr1∆-induced Rad52 foci and intramolecular recombination are not associated with tethering recombinogenic DNA lesions to the nuclear periphery. In conclusion, the absence of Swr1 impairs efficient recombinational repair of specific DNA lesions by mechanisms that are influenced by SWR subunits, including actin, and nuclear envelope components. We suggest that these recombinational phenotypes might be associated with a pathological effect on homologous recombination of actin-containing complexes.
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Affiliation(s)
- Macarena Morillo-Huesca
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain
| | - Marina Murillo-Pineda
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain
| | - Marta Barrientos-Moreno
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain
| | - Elena Gómez-Marín
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain
| | - Marta Clemente-Ruiz
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain
| | - Félix Prado
- Department of Genome Biology, Andalusian Molecular Biology and Regenerative Medicine Center (CABIMER), Consejo Superior de Investigaciones Científicas-University of Seville-University Pablo de Olavide, Spain
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31
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Ayra-Plasencia J, Machín F. Yeast cells can partially revert chromosome segregation to repair late DNA double-strand breaks through homologous recombination. Mol Cell Oncol 2019; 6:e1648027. [PMID: 31528706 DOI: 10.1080/23723556.2019.1648027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 07/19/2019] [Accepted: 07/23/2019] [Indexed: 10/26/2022]
Abstract
DNA repair in late mitosis sets paradoxical scenarios. Cyclin-dependent kinase (CDK) activity is high, which favors homologous recombination (HR), despite a sister chromatid is not physically close to recombine with. We have found that DNA double-strand breaks partially revert chromosome segregation to find an intact template and repair through HR.
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Affiliation(s)
- Jessel Ayra-Plasencia
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Escuela de Doctorado y Estudios de Posgrado, Universidad de La Laguna, Santa Cruz de Tenerife, Spain
| | - Félix Machín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.,Instituto de Tecnologías Biomédicas, Universidad de La Laguna, Santa Cruz de Tenerife, Spain.,Facultad de Ciencias de la Salud, Universidad Fernando Pessoa Canarias, Las Palmas de Gran Canaria, Spain
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32
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Estrem C, Moore JK. Help or hindrance: how do microtubule-based forces contribute to genome damage and repair? Curr Genet 2019; 66:303-311. [PMID: 31501990 DOI: 10.1007/s00294-019-01033-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/27/2019] [Accepted: 08/27/2019] [Indexed: 10/26/2022]
Abstract
Forces generated by molecular motors and the cytoskeleton move the nucleus and genome during many cellular processes, including cell migration and division. How these forces impact the genome, and whether cells regulate cytoskeletal forces to preserve genome integrity is unclear. We recently demonstrated that, in budding yeast, mutants that stabilize the microtubule cytoskeleton cause excessive movement of the mitotic spindle and nucleus. We found that increased nuclear movement results in DNA damage and increased time to repair the damage through homology-directed repair. Our results indicate that nuclear movement impairs DNA repair through increased tension on chromosomes and nuclear deformation. However, the previous studies have shown genome mobility, driven by cytoskeleton-based forces, aids in homology-directed DNA repair. This sets up an apparent paradox, where genome mobility may prevent or promote DNA repair. Hence, this review explores how the genome is affected by nuclear movement and how genome mobility could aid or hinder homology-directed repair.
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Affiliation(s)
- Cassi Estrem
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO, USA.
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33
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Caridi CP, Plessner M, Grosse R, Chiolo I. Nuclear actin filaments in DNA repair dynamics. Nat Cell Biol 2019; 21:1068-1077. [PMID: 31481797 PMCID: PMC6736642 DOI: 10.1038/s41556-019-0379-1] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 07/24/2019] [Indexed: 02/06/2023]
Abstract
Recent development of innovative tools for live imaging of actin filaments (F-actin) enabled the detection of surprising nuclear structures responding to various stimuli, challenging previous models that actin is substantially monomeric in the nucleus. We review these discoveries, focusing on double-strand break (DSB) repair responses. These studies revealed a remarkable network of nuclear filaments and regulatory mechanisms coordinating chromatin dynamics with repair progression and led to a paradigm shift by uncovering the directed movement of repair sites.
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Affiliation(s)
| | - Matthias Plessner
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg im Breisgau, Germany
- CIBSS - Centre for Integrative Biological Signaling Studies, University of Freiburg, Freiburg im Breisgau, Germany
| | - Robert Grosse
- Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg im Breisgau, Germany
- CIBSS - Centre for Integrative Biological Signaling Studies, University of Freiburg, Freiburg im Breisgau, Germany
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA.
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34
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Hall AC, Ostrowski LA, Mekhail K. Phase Separation as a Melting Pot for DNA Repeats. Trends Genet 2019; 35:589-600. [DOI: 10.1016/j.tig.2019.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 05/03/2019] [Accepted: 05/07/2019] [Indexed: 12/23/2022]
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35
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Schrank B, Gautier J. Assembling nuclear domains: Lessons from DNA repair. J Cell Biol 2019; 218:2444-2455. [PMID: 31324649 PMCID: PMC6683749 DOI: 10.1083/jcb.201904202] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/24/2019] [Accepted: 06/27/2019] [Indexed: 12/14/2022] Open
Abstract
Schrank and Gautier discuss the generation and function of nuclear domains during DNA repair with a special focus on nuclear actin polymerization. Eukaryotic nuclei are organized into nuclear domains that unite loci sharing a common function. These domains are essential for diverse processes including (1) the formation of topologically associated domains (TADs) that coordinate replication and transcription, (2) the formation of specialized transcription and splicing factories, and (3) the clustering of DNA double-strand breaks (DSBs), which concentrates damaged DNA for repair. The generation of nuclear domains requires forces that are beginning to be identified. In the case of DNA DSBs, DNA movement and clustering are driven by actin filament nucleators. Furthermore, RNAs and low-complexity protein domains such as RNA-binding proteins also accumulate around sites of transcription and repair. The link between liquid–liquid phase separation and actin nucleation in the formation of nuclear domains is still unknown. This review discusses DSB repair domain formation as a model for functional nuclear domains in other genomic contexts.
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Affiliation(s)
- Benjamin Schrank
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY
| | - Jean Gautier
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY
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36
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Abstract
DNA double-strand breaks (DSBs) are particularly challenging to repair in pericentromeric heterochromatin because of the increased risk of aberrant recombination in highly repetitive sequences. Recent studies have identified specialized mechanisms enabling 'safe' homologous recombination (HR) repair in heterochromatin. These include striking nuclear actin filaments (F-actin) and myosins that drive the directed motion of repair sites to the nuclear periphery for 'safe' repair. Here, we summarize our current understanding of the mechanisms involved, and propose how they might operate in the context of a phase-separated environment.
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37
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Ayra-Plasencia J, Machín F. DNA double-strand breaks in telophase lead to coalescence between segregated sister chromatid loci. Nat Commun 2019; 10:2862. [PMID: 31253793 PMCID: PMC6598993 DOI: 10.1038/s41467-019-10742-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 05/30/2019] [Indexed: 12/24/2022] Open
Abstract
DNA double strand breaks (DSBs) pose a high risk for genome integrity. Cells repair DSBs through homologous recombination (HR) when a sister chromatid is available. HR is upregulated by the cycling dependent kinase (CDK) despite the paradox of telophase, where CDK is high but a sister chromatid is not nearby. Here we study in the budding yeast the response to DSBs in telophase, and find they activate the DNA damage checkpoint (DDC), leading to a telophase-to-G1 delay. Outstandingly, we observe a partial reversion of sister chromatid segregation, which includes approximation of segregated material, de novo formation of anaphase bridges, and coalescence between sister loci. We finally show that DSBs promote a massive change in the dynamics of telophase microtubules (MTs), together with dephosphorylation and relocalization of kinesin-5 Cin8. We propose that chromosome segregation is not irreversible and that DSB repair using the sister chromatid is possible in telophase.
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Affiliation(s)
- Jessel Ayra-Plasencia
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
- Escuela de Doctorado y Estudios de Posgrado, Universidad de La Laguna, Santa Cruz de Tenerife, Spain
| | - Félix Machín
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.
- Instituto de Tecnologías Biomédicas, Universidad de La Laguna, Santa Cruz de Tenerife, Spain.
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38
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Estrem C, Moore JK. Astral microtubule forces alter nuclear organization and inhibit DNA repair in budding yeast. Mol Biol Cell 2019; 30:2000-2013. [PMID: 31067146 PMCID: PMC6727761 DOI: 10.1091/mbc.e18-12-0808] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Dividing cells must balance the maintenance of genome integrity with the generation of cytoskeletal forces that control chromosome position. In this study, we investigate how forces on astral microtubules impact the genome during cell division by using live-cell imaging of the cytoskeleton, chromatin, and DNA damage repair in budding yeast. Our results demonstrate that dynein-dependent forces on astral microtubules are propagated through the spindle during nuclear migration and when in excess can increase the frequency of double-stranded breaks (DSBs). Under these conditions, we find that homology-directed repair of DSBs is delayed, indicating antagonism between nuclear migration and the mechanism of homology-directed repair. These effects are partially rescued by mutants that weaken pericentric cohesion or mutants that decrease constriction on the nucleus as it moves through the bud neck. We propose that minimizing nuclear movement aids in finding a donor strand for homologous recombination.
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Affiliation(s)
- Cassi Estrem
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
| | - Jeffrey K Moore
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, CO 80045
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39
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Laflamme G, Sim S, Leary A, Pascariu M, Vogel J, D’Amours D. Interphase Microtubules Safeguard Mitotic Progression by Suppressing an Aurora B-Dependent Arrest Induced by DNA Replication Stress. Cell Rep 2019; 26:2875-2889.e3. [DOI: 10.1016/j.celrep.2019.02.051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 12/21/2018] [Accepted: 02/13/2019] [Indexed: 10/27/2022] Open
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40
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Shimamoto K, Sunada Y. Dimensionality Expansion of a Butterfly Shaped Pd 4 Framework: Constructing Edge-Sharing Pd 6 Tetrahedra. Chemistry 2019; 25:3761-3765. [PMID: 30762905 DOI: 10.1002/chem.201805678] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 01/22/2019] [Indexed: 11/09/2022]
Abstract
The construction of well-defined transition-metal clusters has attracted substantial attention due to their unique chemical and/or physical properties. Metal clusters with 1D or 2D structures are now accessible by template-synthesis methods, in which multiple metal atoms are arranged with the aid of template molecules and their 1D or 2D structures. However, the rational synthesis of 3D clusters remains challenging, mostly due to a lack of appropriate template molecules. Herein, we report the rational synthesis of a 2D butterfly shaped Pd4 framework (2) and 3D edge-sharing Pd6 tetrahedra (5) by treatment of easily available organosilicon compounds with Pd(CNtBu)2 . The diphenylsilylene moiety thereby serves as the key component to generate the butterfly structure of the Pd4 clusters in 2. A dimensionality expansion, induced by two Cl atoms, of two butterfly shaped Pd4 subunits supported by two diphenylsilylene moieties afforded the edge-sharing tetrahedral architecture of the Pd6 cluster in 5.
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Affiliation(s)
- Kento Shimamoto
- Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Yusuke Sunada
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Meguro-ku, Komaba, Tokyo, Japan.,Department of Applied Chemistry, School of Engineering, The University of Tokyo, Tokyo, Japan
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41
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Abstract
Recent advances in both the technologies used to measure chromatin movement and the biophysical analysis used to model them have yielded a fuller understanding of chromatin dynamics and the polymer structure that underlies it. Changes in nucleosome packing, checkpoint kinase activation, the cell cycle, chromosomal tethers, and external forces acting on nuclei in response to external and internal stimuli can alter the basal mobility of DNA in interphase nuclei of yeast or mammalian cells. Although chromatin movement is assumed to be necessary for many DNA-based processes, including gene activation by distal enhancer–promoter interaction or sequence-based homology searches during double-strand break repair, experimental evidence supporting an essential role in these activities is sparse. Nonetheless, high-resolution tracking of chromatin dynamics has led to instructive models of the higher-order folding and flexibility of the chromatin polymer. Key regulators of chromatin motion in physiological conditions or after damage induction are reviewed here.
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Affiliation(s)
- Andrew Seeber
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
- Faculty of Natural Sciences, University of Basel, 4056 Basel, Switzerland
- Current affiliation: Harvard Center for Advanced Imaging, Cambridge, MA 02138, USA
| | - Michael H. Hauer
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
- Faculty of Natural Sciences, University of Basel, 4056 Basel, Switzerland
| | - Susan M. Gasser
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
- Faculty of Natural Sciences, University of Basel, 4056 Basel, Switzerland
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42
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Conserved Pbp1/Ataxin-2 regulates retrotransposon activity and connects polyglutamine expansion-driven protein aggregation to lifespan-controlling rDNA repeats. Commun Biol 2018; 1:187. [PMID: 30417124 PMCID: PMC6218562 DOI: 10.1038/s42003-018-0187-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 10/09/2018] [Indexed: 12/17/2022] Open
Abstract
Ribosomal DNA (rDNA) repeat instability and protein aggregation are thought to be two major and independent drivers of cellular aging. Pbp1, the yeast ortholog of human ATXN2, maintains rDNA repeat stability and lifespan via suppression of RNA-DNA hybrids. ATXN2 polyglutamine expansion drives neurodegeneration causing spinocerebellar ataxia type 2 and promoting amyotrophic lateral sclerosis. Here, molecular characterization of Pbp1 revealed that its knockout or subjection to disease-modeling polyQ expansion represses Ty1 (Transposons of Yeast) retrotransposons by respectively promoting Trf4-depedendent RNA turnover and Ty1 Gag protein aggregation. This aggregation, but not its impact on retrotransposition, compromises rDNA repeat stability and shortens lifespan by hyper-activating Trf4-dependent turnover of intergenic ncRNA within the repeats. We uncover a function for the conserved Pbp1/ATXN2 proteins in the promotion of retrotransposition, create and describe powerful yeast genetic models of ATXN2-linked neurodegenerative diseases, and connect the major aging mechanisms of rDNA instability and protein aggregation.
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43
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Rodriguez-Berriguete G, Granata G, Puliyadi R, Tiwana G, Prevo R, Wilson RS, Yu S, Buffa F, Humphrey TC, McKenna WG, Higgins GS. Nucleoporin 54 contributes to homologous recombination repair and post-replicative DNA integrity. Nucleic Acids Res 2018; 46:7731-7746. [PMID: 29986057 PMCID: PMC6125679 DOI: 10.1093/nar/gky569] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 05/25/2018] [Accepted: 06/14/2018] [Indexed: 12/21/2022] Open
Abstract
The nuclear pore complex (NPC) machinery is emerging as an important determinant in the maintenance of genome integrity and sensitivity to DNA double-strand break (DSB)-inducing agents, such as ionising radiation (IR). In this study, using a high-throughput siRNA screen, we identified the central channel NPC protein Nup54, and concomitantly its molecular partners Nup62 and Nup58, as novel factors implicated in radiosensitivity. Nup54 depletion caused an increase in cell death by mitotic catastrophe after IR, and specifically enhanced both the duration of the G2 arrest and the radiosensitivity of cells that contained replicated DNA at the time of IR exposure. Nup54-depleted cells also exhibited increased formation of chromosome aberrations arisen from replicated DNA. Interestingly, we found that Nup54 is epistatic with the homologous recombination (HR) factor Rad51. Moreover, using specific DNA damage repair reporters, we observed a decreased HR repair activity upon Nup54 knockdown. In agreement with a role in HR repair, we also demonstrated a decreased formation of HR-linked DNA synthesis foci and sister chromatid exchanges after IR in cells depleted of Nup54. Our study reveals a novel role for Nup54 in the response to IR and the maintenance of HR-mediated genome integrity.
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Affiliation(s)
- Gonzalo Rodriguez-Berriguete
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Giovanna Granata
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Rathi Puliyadi
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Gaganpreet Tiwana
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Remko Prevo
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Rhodri S Wilson
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Sheng Yu
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Francesca Buffa
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Timothy C Humphrey
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - W Gillies McKenna
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
| | - Geoff S Higgins
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford OX3 7DQ, UK
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44
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Oshidari R, Strecker J, Chung DKC, Abraham KJ, Chan JNY, Damaren CJ, Mekhail K. Nuclear microtubule filaments mediate non-linear directional motion of chromatin and promote DNA repair. Nat Commun 2018; 9:2567. [PMID: 29967403 PMCID: PMC6028458 DOI: 10.1038/s41467-018-05009-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2018] [Accepted: 06/07/2018] [Indexed: 12/19/2022] Open
Abstract
Damaged DNA shows increased mobility, which can promote interactions with repair-conducive nuclear pore complexes (NPCs). This apparently random mobility is paradoxically abrogated upon disruption of microtubules or kinesins, factors that typically cooperate to mediate the directional movement of macromolecules. Here, we resolve this paradox by uncovering DNA damage-inducible intranuclear microtubule filaments (DIMs) that mobilize damaged DNA and promote repair. Upon DNA damage, relief of centromeric constraint induces DIMs that cooperate with the Rad9 DNA damage response mediator and Kar3 kinesin motor to capture DNA lesions, which then linearly move along dynamic DIMs. Decreasing and hyper-inducing DIMs respectively abrogates and hyper-activates repair. Accounting for DIM dynamics across cell populations by measuring directional changes of damaged DNA reveals that it exhibits increased non-linear directional behavior in nuclear space. Abrogation of DIM-dependent processes or repair-promoting factors decreases directional behavior. Thus, inducible and dynamic nuclear microtubule filaments directionally mobilize damaged DNA and promote repair. Following DNA damage, different processes come to action to aid repair. The authors here find that microtubule filaments within the cell nucleus capture and non-randomly mobilize damaged chromatin to mediate DNA repair.
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Affiliation(s)
- Roxanne Oshidari
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, University of Toronto, West Tower, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Jonathan Strecker
- Department of Molecular Genetics, MaRS Centre, University of Toronto, West Tower, 661 University Avenue, Toronto, ON, M5G 1M1, Canada.,Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, ON, M5G 1X5, Canada.,Broad Institute of MIT and Harvard, 75 Ames Street, Cambridge, MA, 02142, USA
| | - Daniel K C Chung
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, University of Toronto, West Tower, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Karan J Abraham
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, University of Toronto, West Tower, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Janet N Y Chan
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, University of Toronto, West Tower, 661 University Avenue, Toronto, ON, M5G 1M1, Canada
| | - Christopher J Damaren
- Institute for Aerospace Studies, University of Toronto, 4925 Dufferin Street, Toronto, ON, M3H 5T6, Canada
| | - Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, MaRS Centre, University of Toronto, West Tower, 661 University Avenue, Toronto, ON, M5G 1M1, Canada. .,Canada Research Chairs Program, University of Toronto, 1 King's College Circle, Toronto, ON, M5S 1A8, Canada.
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45
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Caridi CP, D'Agostino C, Ryu T, Zapotoczny G, Delabaere L, Li X, Khodaverdian VY, Amaral N, Lin E, Rau AR, Chiolo I. Nuclear F-actin and myosins drive relocalization of heterochromatic breaks. Nature 2018; 559:54-60. [PMID: 29925946 PMCID: PMC6051730 DOI: 10.1038/s41586-018-0242-8] [Citation(s) in RCA: 232] [Impact Index Per Article: 38.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 05/18/2018] [Indexed: 12/13/2022]
Abstract
Heterochromatin mainly comprises repeated DNA sequences that are prone to ectopic recombination. In Drosophila cells, 'safe' repair of heterochromatic double-strand breaks by homologous recombination relies on the relocalization of repair sites to the nuclear periphery before strand invasion. The mechanisms responsible for this movement were unknown. Here we show that relocalization occurs by directed motion along nuclear actin filaments assembled at repair sites by the Arp2/3 complex. Relocalization requires nuclear myosins associated with the heterochromatin repair complex Smc5/6 and the myosin activator Unc45, which is recruited to repair sites by Smc5/6. ARP2/3, actin nucleation and myosins also relocalize heterochromatic double-strand breaks in mouse cells. Defects in this pathway result in impaired heterochromatin repair and chromosome rearrangements. These findings identify de novo nuclear actin filaments and myosins as effectors of chromatin dynamics for heterochromatin repair and stability in multicellular eukaryotes.
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Affiliation(s)
- Christopher P Caridi
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Carla D'Agostino
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Taehyun Ryu
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Grzegorz Zapotoczny
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Laetitia Delabaere
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Xiao Li
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Varandt Y Khodaverdian
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Nuno Amaral
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
- Karolinska Institute, Stockholm, Sweden
| | - Emily Lin
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Alesandra R Rau
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA
| | - Irene Chiolo
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA, USA.
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Zimmer C, Fabre E. Chromatin mobility upon DNA damage: state of the art and remaining questions. Curr Genet 2018; 65:1-9. [DOI: 10.1007/s00294-018-0852-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 05/30/2018] [Accepted: 06/04/2018] [Indexed: 12/14/2022]
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Abstract
The health of an organism is intimately linked to its ability to repair damaged DNA. Importantly, DNA repair processes are highly dynamic. This highlights the necessity of characterizing DNA repair in live cells. Advanced genome editing and imaging approaches allow us to visualize damaged DNA and its associated factors in real time. Here, we summarize both established and recent methods that are used to induce DNA damage and visualize damaged DNA and its repair in live cells.
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Affiliation(s)
- Roxanne Oshidari
- Department of Laboratory Medicine and Pathobiology, University of Toronto, MaRS Centre, West Tower, 661 University Avenue, Toronto, Ontario M5G 1M1, Canada
| | - Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, University of Toronto, MaRS Centre, West Tower, 661 University Avenue, Toronto, Ontario M5G 1M1, Canada; Canada Research Chairs Program, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.
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48
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Cheung S, Manhas S, Measday V. Retrotransposon targeting to RNA polymerase III-transcribed genes. Mob DNA 2018; 9:14. [PMID: 29713390 PMCID: PMC5911963 DOI: 10.1186/s13100-018-0119-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 04/16/2018] [Indexed: 12/20/2022] Open
Abstract
Retrotransposons are genetic elements that are similar in structure and life cycle to retroviruses by replicating via an RNA intermediate and inserting into a host genome. The Saccharomyces cerevisiae (S. cerevisiae) Ty1-5 elements are long terminal repeat (LTR) retrotransposons that are members of the Ty1-copia (Pseudoviridae) or Ty3-gypsy (Metaviridae) families. Four of the five S. cerevisiae Ty elements are inserted into the genome upstream of RNA Polymerase (Pol) III-transcribed genes such as transfer RNA (tRNA) genes. This particular genomic locus provides a safe environment for Ty element insertion without disruption of the host genome and is a targeting strategy used by retrotransposons that insert into compact genomes of hosts such as S. cerevisiae and the social amoeba Dictyostelium. The mechanism by which Ty1 targeting is achieved has been recently solved due to the discovery of an interaction between Ty1 Integrase (IN) and RNA Pol III subunits. We describe the methods used to identify the Ty1-IN interaction with Pol III and the Ty1 targeting consequences if the interaction is perturbed. The details of Ty1 targeting are just beginning to emerge and many unexplored areas remain including consideration of the 3-dimensional shape of genome. We present a variety of other retrotransposon families that insert adjacent to Pol III-transcribed genes and the mechanism by which the host machinery has been hijacked to accomplish this targeting strategy. Finally, we discuss why retrotransposons selected Pol III-transcribed genes as a target during evolution and how retrotransposons have shaped genome architecture.
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Affiliation(s)
- Stephanie Cheung
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
| | - Savrina Manhas
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
| | - Vivien Measday
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, Vancouver, BC V6T 1Z4 Canada
- Department of Food Science, Wine Research Centre, Faculty of Land and Food Systems, University of British Columbia, Room 325-2205 East Mall, Vancouver, British Columbia V6T 1Z4 Canada
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Caridi PC, Delabaere L, Zapotoczny G, Chiolo I. And yet, it moves: nuclear and chromatin dynamics of a heterochromatic double-strand break. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0291. [PMID: 28847828 PMCID: PMC5577469 DOI: 10.1098/rstb.2016.0291] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/07/2017] [Indexed: 12/15/2022] Open
Abstract
Heterochromatin is mostly composed of repeated DNA sequences prone to aberrant recombination. How cells maintain the stability of these sequences during double-strand break (DSB) repair has been a long-standing mystery. Studies in Drosophila cells revealed that faithful homologous recombination repair of heterochromatic DSBs relies on the striking relocalization of repair sites to the nuclear periphery before Rad51 recruitment and repair progression. Here, we summarize our current understanding of this response, including the molecular mechanisms involved, and conserved pathways in mammalian cells. We will highlight important similarities with pathways identified in budding yeast for repair of other types of repeated sequences, including rDNA and short telomeres. We will also discuss the emerging role of chromatin composition and regulation in heterochromatin repair progression. Together, these discoveries challenged previous assumptions that repair sites are substantially static in multicellular eukaryotes, that heterochromatin is largely inert in the presence of DSBs, and that silencing and compaction in this domain are obstacles to repair. This article is part of the themed issue ‘Chromatin modifiers and remodellers in DNA repair and signalling’.
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Affiliation(s)
- P Christopher Caridi
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | - Laetitia Delabaere
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | - Grzegorz Zapotoczny
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
| | - Irene Chiolo
- Department of Molecular and Computational Biology, University of Southern California, Los Angeles, CA 90089, USA
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Mekhail K. Defining the Damaged DNA Mobility Paradox as Revealed by the Study of Telomeres, DSBs, Microtubules and Motors. Front Genet 2018; 9:95. [PMID: 29616083 PMCID: PMC5869915 DOI: 10.3389/fgene.2018.00095] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 03/07/2018] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic genomes are non-randomly arranged inside the nucleus. Despite this ordered spatial genome organization, damaged DNA exhibits increased random mobility within nuclear space. This increased random movement is thought to promote DNA repair by facilitating homology search, allowing targeting to repair-conducive nuclear domains, or releasing damage from repair-repressive locations. Recent studies focusing on the relationship between telomeres, DNA repair processes, and nuclear organization have revealed that the disruption of motor proteins or microtubules, which typically mediate the directed motion of cargo, disrupts the random mobility of damaged DNA. These findings define a new biological paradox. Here, I define this as the damaged DNA mobility paradox, describe how it uncovers key gaps in knowledge, and highlight key questions to help guide us toward paradox resolution.
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Affiliation(s)
- Karim Mekhail
- Department of Laboratory Medicine and Pathobiology, University of Toronto, MaRS Centre, Toronto, ON, Canada.,Canada Research Chairs Program, University of Toronto, Toronto, ON, Canada
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