1
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Ryu T, Merigliano C, Chiolo I. Nup153 is not required for anchoring heterochromatic DSBs to the nuclear periphery. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001176. [PMID: 38737725 PMCID: PMC11087819 DOI: 10.17912/micropub.biology.001176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/20/2024] [Accepted: 04/26/2024] [Indexed: 05/14/2024]
Abstract
Pericentromeric heterochromatin mostly comprises repeated DNA sequences prone to ectopic recombination. In Drosophila cells, 'safe' homologous recombination repair requires relocalization of heterochromatic repair sites to the nuclear periphery before Rad51 recruitment and strand invasion. DSBs are anchored to the nuclear periphery through the Nup107/160 nucleoporin complex. Previous studies suggested that the nuclear pore 'basket' protein Nup153 could also mediate anchoring, but Nup153 RNAi depletion also affects Nup107 association with the pores, preventing a direct assessment of Nup153 role. Using a separation of function mutant, here we show that Nup153 is not required for anchoring heterochromatic DSBs to the nuclear periphery.
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Affiliation(s)
- Taehyun Ryu
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
- Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Chiara Merigliano
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
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2
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van Bueren MAE, Janssen A. The impact of chromatin on double-strand break repair: Imaging tools and discoveries. DNA Repair (Amst) 2024; 133:103592. [PMID: 37976899 DOI: 10.1016/j.dnarep.2023.103592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 10/16/2023] [Accepted: 11/07/2023] [Indexed: 11/19/2023]
Abstract
Eukaryotic nuclei are constantly being exposed to factors that break or chemically modify the DNA. Accurate repair of this DNA damage is crucial to prevent DNA mutations and maintain optimal cell function. To overcome the detrimental effects of DNA damage, a multitude of repair pathways has evolved. These pathways need to function properly within the different chromatin domains present in the nucleus. Each of these domains exhibit distinct molecular- and bio-physical characteristics that can influence the response to DNA damage. In particular, chromatin domains highly enriched for repetitive DNA sequences, such as nucleoli, centromeres and pericentromeric heterochromatin require tailored repair mechanisms to safeguard genome stability. Work from the past decades has led to the development of innovative imaging tools as well as inducible DNA damage techniques to gain new insights into the impact of these repetitive chromatin domains on the DNA repair process. Here we summarize these tools with a particular focus on Double-Strand Break (DSB) repair, and discuss the insights gained into our understanding of the influence of chromatin domains on DSB -dynamics and -repair pathway choice.
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Affiliation(s)
- Marit A E van Bueren
- Center for Molecular Medicine, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, the Netherlands
| | - Aniek Janssen
- Center for Molecular Medicine, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, the Netherlands.
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3
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Miller JM, Prange S, Ji H, Rau AR, Khodaverdian VY, Li X, Patel A, Butova N, Lutter A, Chung H, Merigliano C, Rawal CC, Hanscom T, McVey M, Chiolo I. Alternative end-joining results in smaller deletions in heterochromatin relative to euchromatin. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.03.531058. [PMID: 37645729 PMCID: PMC10461932 DOI: 10.1101/2023.03.03.531058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Pericentromeric heterochromatin is highly enriched for repetitive sequences prone to aberrant recombination. Previous studies showed that homologous recombination (HR) repair is uniquely regulated in this domain to enable 'safe' repair while preventing aberrant recombination. In Drosophila cells, DNA double-strand breaks (DSBs) relocalize to the nuclear periphery through nuclear actin-driven directed motions before recruiting the strand invasion protein Rad51 and completing HR repair. End-joining (EJ) repair also occurs with high frequency in heterochromatin of fly tissues, but how alternative EJ (alt-EJ) pathways operate in heterochromatin remains largely uncharacterized. Here, we induce DSBs in single euchromatic and heterochromatic sites using a new system that combines the DR- white reporter and I-SceI expression in spermatogonia of flies. Using this approach, we detect higher frequency of HR repair in heterochromatin, relative to euchromatin. Further, sequencing of mutagenic repair junctions reveals the preferential use of different EJ pathways across distinct euchromatic and heterochromatic sites. Interestingly, synthesis-dependent microhomology-mediated end joining (SD-MMEJ) appears differentially regulated in the two domains, with a preferential use of motifs close to the cut site in heterochromatin relative to euchromatin, resulting in smaller deletions. Together, these studies establish a new approach to study repair outcomes in fly tissues, and support the conclusion that heterochromatin uses more HR and less mutagenic EJ repair relative to euchromatin.
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4
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Rawal CC, Butova NL, Mitra A, Chiolo I. An Expanding Toolkit for Heterochromatin Repair Studies. Genes (Basel) 2022; 13:genes13030529. [PMID: 35328082 PMCID: PMC8955653 DOI: 10.3390/genes13030529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 02/28/2022] [Accepted: 03/02/2022] [Indexed: 12/04/2022] Open
Abstract
Pericentromeric heterochromatin is mostly composed of repetitive DNA sequences prone to aberrant recombination. Cells have developed highly specialized mechanisms to enable ‘safe’ homologous recombination (HR) repair while preventing aberrant recombination in this domain. Understanding heterochromatin repair responses is essential to understanding the critical mechanisms responsible for genome integrity and tumor suppression. Here, we review the tools, approaches, and methods currently available to investigate double-strand break (DSB) repair in pericentromeric regions, and also suggest how technologies recently developed for euchromatin repair studies can be adapted to characterize responses in heterochromatin. With this ever-growing toolkit, we are witnessing exciting progress in our understanding of how the ‘dark matter’ of the genome is repaired, greatly improving our understanding of genome stability mechanisms.
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5
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Zhang L, Geng X, Wang F, Tang J, Ichida Y, Sharma A, Jin S, Chen M, Tang M, Pozo FM, Wang W, Wang J, Wozniak M, Guo X, Miyagi M, Jin F, Xu Y, Yao X, Zhang Y. 53BP1 regulates heterochromatin through liquid phase separation. Nat Commun 2022; 13:360. [PMID: 35042897 PMCID: PMC8766474 DOI: 10.1038/s41467-022-28019-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 01/03/2022] [Indexed: 01/09/2023] Open
Abstract
Human 53BP1 is primarily known as a key player in regulating DNA double strand break (DSB) repair choice; however, its involvement in other biological process is less well understood. Here, we report a previously uncharacterized function of 53BP1 at heterochromatin, where it undergoes liquid-liquid phase separation (LLPS) with the heterochromatin protein HP1α in a mutually dependent manner. Deletion of 53BP1 results in a reduction in heterochromatin centers and the de-repression of heterochromatic tandem repetitive DNA. We identify domains and residues of 53BP1 required for its LLPS, which overlap with, but are distinct from, those involved in DSB repair. Further, 53BP1 mutants deficient in DSB repair, but proficient in LLPS, rescue heterochromatin de-repression and protect cells from stress-induced DNA damage and senescence. Our study suggests that in addition to DSB repair modulation, 53BP1 contributes to the maintenance of heterochromatin integrity and genome stability through LLPS.
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Affiliation(s)
- Lei Zhang
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA.
- National 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering, Hubei University of Technology, Wuhan, Hubei, 430068, China.
| | - Xinran Geng
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Fangfang Wang
- Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou, 510632, China
| | - Jinshan Tang
- Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou, 510632, China
| | - Yu Ichida
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Arishya Sharma
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Sora Jin
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Mingyue Chen
- National 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering, Hubei University of Technology, Wuhan, Hubei, 430068, China
| | - Mingliang Tang
- College of Life Sciences, Wuhan University, Wuhan, Hubei, 430068, China
| | - Franklin Mayca Pozo
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Wenxiu Wang
- National 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering, Hubei University of Technology, Wuhan, Hubei, 430068, China
| | - Janet Wang
- Department of Genetics and Genome Sciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Michal Wozniak
- Department of Pharmacology and Toxicology, Wright State University, Dayton, OH, 45435, USA
- Department of Molecular Biology of Cancer, Medical University of Lodz, 6/8 Mazowiecka Street, 92-215, Lodz, Poland
| | - Xiaoxia Guo
- National 111 Center for Cellular Regulation and Molecular Pharmaceutics, Key Laboratory of Fermentation Engineering, Hubei University of Technology, Wuhan, Hubei, 430068, China
| | - Masaru Miyagi
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Fulai Jin
- Department of Genetics and Genome Sciences, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA
| | - Yongjie Xu
- Department of Pharmacology and Toxicology, Wright State University, Dayton, OH, 45435, USA
| | - Xinsheng Yao
- Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou, 510632, China
| | - Youwei Zhang
- Department of Pharmacology, Case Comprehensive Cancer Center, Case Western Reserve University, School of Medicine, Cleveland, OH, 44106, USA.
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6
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Abstract
TEX264 (testes expressed gene 264) is a single-pass transmembrane protein, consisting of an N-terminal hydrophobic region, a gyrase inhibitory (GyrI)-like domain, and a loosely structured C terminus. TEX264 was first identified as an endoplasmic reticulum (ER)-resident Atg8-family-binding protein that mediates the degradation of portions of the ER during starvation (i.e., reticulophagy). More recently, TEX264 was identified as a cofactor of VCP/p97 ATPase that promotes the repair of covalently trapped TOP1 (DNA topoisomerase 1)-DNA crosslinks. This review summarizes the current knowledge of TEX264 as a protein with roles in both autophagy and DNA repair and provides an evolutionary and structural analysis of GyrI proteins. Based on our phylogenetic analysis, we provide evidence that TEX264 is a member of a large superfamily of GyrI-like proteins that evolved in bacteria and are present in metazoans, including invertebrates and chordates.Abbreviations: Atg8: autophagy related 8; Atg39: autophagy related 39; Cdc48: cell division cycle 48; CGAS: cyclic GMP-AMP synthase; DPC: DNA-protein crosslinks; DSB: DNA double-strand break; ER: endoplasmic reticulum; GyrI: gyrase inhibitory domain; LRR: leucine-rich repeat; MAFFT: multiple alignment using fast Fourier transform; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; STUBL: SUMO targeted ubiquitin ligase; SUMO: small ubiquitin-like modifier; TEX264: testis expressed gene 264; TOP1cc: topoisomerase 1-cleavage complex; UBZ: ubiquitin binding Zn finger domain; VCP: valosin containing protein.
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Affiliation(s)
- John Fielden
- Medical Research Council (MRC) Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK
| | - Marta Popović
- Laboratory for Molecular Ecotoxicology, Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb, Croatia
| | - Kristijan Ramadan
- Medical Research Council (MRC) Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK
- CONTACT Kristijan Ramadan Medical Research Council (MRC) Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, UK
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7
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Merigliano C, Chiolo I. Multi-scale dynamics of heterochromatin repair. Curr Opin Genet Dev 2021; 71:206-215. [PMID: 34717276 DOI: 10.1016/j.gde.2021.09.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 09/16/2021] [Accepted: 09/27/2021] [Indexed: 10/24/2022]
Abstract
Studies across different organisms show that nuclear architecture and dynamics play central roles in different aspects of homologous recombination (HR) repair. Here we review the most recent discoveries in this field, ranging from directed motions mediating relocalization pathways, to global chromatin mobilization, local DNA looping, and changes in repair focus properties associated with clustering and phase separation. We discuss how these dynamics work in different contexts, including molecular mechanisms and regulatory pathways involved. We specifically highlight how they function in pericentromeric heterochromatin, which presents a unique environment for HR repair given the abundance of repeated DNA sequences prone to aberrant recombination, the 'silent' chromatin state, and the phase separation characterizing this domain.
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Affiliation(s)
- Chiara Merigliano
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA
| | - Irene Chiolo
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA.
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8
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The Sound of Silence: How Silenced Chromatin Orchestrates the Repair of Double-Strand Breaks. Genes (Basel) 2021; 12:genes12091415. [PMID: 34573397 PMCID: PMC8467445 DOI: 10.3390/genes12091415] [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: 08/16/2021] [Revised: 09/07/2021] [Accepted: 09/13/2021] [Indexed: 12/29/2022] Open
Abstract
The eukaryotic nucleus is continuously being exposed to endogenous and exogenous sources that cause DNA breaks, whose faithful repair requires the activity of dedicated nuclear machineries. DNA is packaged into a variety of chromatin domains, each characterized by specific molecular properties that regulate gene expression and help maintain nuclear structure. These different chromatin environments each demand a tailored response to DNA damage. Silenced chromatin domains in particular present a major challenge to the cell’s DNA repair machinery due to their specific biophysical properties and distinct, often repetitive, DNA content. To this end, we here discuss the interplay between silenced chromatin domains and DNA damage repair, specifically double-strand breaks, and how these processes help maintain genome stability.
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9
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Chang YC, Oram MK, Bielinsky AK. SUMO-Targeted Ubiquitin Ligases and Their Functions in Maintaining Genome Stability. Int J Mol Sci 2021; 22:ijms22105391. [PMID: 34065507 PMCID: PMC8161396 DOI: 10.3390/ijms22105391] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 05/14/2021] [Accepted: 05/16/2021] [Indexed: 02/06/2023] Open
Abstract
Small ubiquitin-like modifier (SUMO)-targeted E3 ubiquitin ligases (STUbLs) are specialized enzymes that recognize SUMOylated proteins and attach ubiquitin to them. They therefore connect the cellular SUMOylation and ubiquitination circuits. STUbLs participate in diverse molecular processes that span cell cycle regulated events, including DNA repair, replication, mitosis, and transcription. They operate during unperturbed conditions and in response to challenges, such as genotoxic stress. These E3 ubiquitin ligases modify their target substrates by catalyzing ubiquitin chains that form different linkages, resulting in proteolytic or non-proteolytic outcomes. Often, STUbLs function in compartmentalized environments, such as the nuclear envelope or kinetochore, and actively aid in nuclear relocalization of damaged DNA and stalled replication forks to promote DNA repair or fork restart. Furthermore, STUbLs reside in the same vicinity as SUMO proteases and deubiquitinases (DUBs), providing spatiotemporal control of their targets. In this review, we focus on the molecular mechanisms by which STUbLs help to maintain genome stability across different species.
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10
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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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11
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LINC complex regulation of genome organization and function. Curr Opin Genet Dev 2021; 67:130-141. [PMID: 33524904 DOI: 10.1016/j.gde.2020.12.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 11/25/2020] [Accepted: 12/11/2020] [Indexed: 12/28/2022]
Abstract
The regulation of genomic function is in part mediated through the physical organization and architecture of the nucleus. Disruption to nuclear organization and architecture is increasingly being recognized by its contribution to many diseases. The LINC complexes - protein structures traversing the nuclear envelope, that physically connect the nuclear interior, and hence the genome, to cytoplasmic cytoskeletal networks are an important component in the physical organization of the genome and its function. This connection, potentially allows for the constant detection of environmental mechanical stimuli, resulting in altered regulation of nuclear architecture and genome function, either directly or via the process of mechanotransduction. Here, we review the influences LINC complexes exert on genome functions and their impact on cellular/organismal health.
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12
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See C, Arya D, Lin E, Chiolo I. Live Cell Imaging of Nuclear Actin Filaments and Heterochromatic Repair foci in Drosophila and Mouse Cells. Methods Mol Biol 2021; 2153:459-482. [PMID: 32840799 DOI: 10.1007/978-1-0716-0644-5_32] [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] [Indexed: 12/17/2022]
Abstract
Pericentromeric heterochromatin is mostly composed of repeated DNA sequences, which are prone to aberrant recombination during double-strand break (DSB) repair. Studies in Drosophila and mouse cells revealed that 'safe' homologous recombination (HR) repair of these sequences relies on the relocalization of repair sites to outside the heterochromatin domain before Rad51 recruitment. Relocalization requires a striking network of nuclear actin filaments (F-actin) and myosins that drive directed motions. Understanding this pathway requires the detection of nuclear actin filaments that are significantly less abundant than those in the cytoplasm, and the imaging and tracking of repair sites for long time periods. Here, we describe an optimized protocol for live cell imaging of nuclear F-actin in Drosophila cells, and for repair focus tracking in mouse cells, including: imaging setup, image processing approaches, and analysis methods. We emphasize approaches that can be applied to identify the most effective fluorescent markers for live cell imaging, strategies to minimize photobleaching and phototoxicity with a DeltaVision deconvolution microscope, and image processing and analysis methods using SoftWoRx and Imaris software. These approaches enable a deeper understanding of the spatial and temporal dynamics of heterochromatin repair and have broad applicability in the fields of nuclear architecture, nuclear dynamics, and DNA repair.
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Affiliation(s)
- Colby See
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Deepak Arya
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Emily Lin
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | - Irene Chiolo
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA.
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13
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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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14
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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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15
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Valori V, Tus K, Laukaitis C, Harris DT, LeBeau L, Maggert KA. Human rDNA copy number is unstable in metastatic breast cancers. Epigenetics 2020; 15:85-106. [PMID: 31352858 PMCID: PMC6961696 DOI: 10.1080/15592294.2019.1649930] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/07/2019] [Accepted: 07/22/2019] [Indexed: 12/27/2022] Open
Abstract
Chromatin-mediated silencing, including the formation of heterochromatin, silent chromosome territories, and repressed gene promoters, acts to stabilize patterns of gene regulation and the physical structure of the genome. Reduction of chromatin-mediated silencing can result in genome rearrangements, particularly at intrinsically unstable regions of the genome such as transposons, satellite repeats, and repetitive gene clusters including the rRNA gene clusters (rDNA). It is thus expected that mutational or environmental conditions that compromise heterochromatin function might cause genome instability, and diseases associated with decreased epigenetic stability might exhibit genome changes as part of their aetiology. We find the support of this hypothesis in invasive ductal breast carcinoma, in which reduced epigenetic silencing has been previously described, by using a facile method to quantify rDNA copy number in biopsied breast tumours and pair-matched healthy tissue. We found that rDNA and satellite DNA sequences had significant copy number variation - both losses and gains of copies - compared to healthy tissue, arguing that these genome rearrangements are common in developing breast cancer. Thus, any proposed aetiology onset or progression of breast cancer should consider alterations to the epigenome, but must also accommodate concomitant changes to genome sequence at heterochromatic loci.
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Affiliation(s)
- Virginia Valori
- Department of Applied Biosciences, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Katalin Tus
- Department of Pathology, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Christina Laukaitis
- Department of Medicine, University of Arizona, College of Medicine, Tucson, AZ, USA
- University of Arizona Cancer Center, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - David T. Harris
- Department of Immunobiology, University of Arizona, College of Medicine, Tucson, AZ, USA
- Arizona Health Sciences Center Biorepository, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Lauren LeBeau
- Department of Pathology, University of Arizona, College of Medicine, Tucson, AZ, USA
| | - Keith A. Maggert
- University of Arizona Cancer Center, University of Arizona, College of Medicine, Tucson, AZ, USA
- Department of Cellular and Molecular Medicine, University of Arizona, College of Medicine, Tucson, AZ, USA
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16
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Dialynas G, Delabaere L, Chiolo I. Arp2/3 and Unc45 maintain heterochromatin stability in Drosophila polytene chromosomes. Exp Biol Med (Maywood) 2019; 244:1362-1371. [PMID: 31364400 PMCID: PMC6880141 DOI: 10.1177/1535370219862282] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 06/18/2019] [Indexed: 12/31/2022] Open
Abstract
Repairing DNA double-strand breaks is particularly challenging in pericentromeric heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination. In Drosophila Kc cells, accurate homologous recombination repair of heterochromatic double-strand breaks relies on the relocalization of repair sites to the nuclear periphery before Rad51 recruitment and strand invasion. This movement is driven by Arp2/3-dependent nuclear actin filaments and myosins’ ability to walk along them. Conserved mechanisms enable the relocalization of heterochromatic repair sites in mouse cells, and defects in these pathways lead to massive ectopic recombination in heterochromatin and chromosome rearrangements. In Drosophila polytene chromosomes, extensive DNA movement is blocked by a stiff structure of chromosome bundles. Repair pathways in this context are poorly characterized, and whether heterochromatic double-strand breaks relocalize in these cells is unknown. Here, we show that damage in heterochromatin results in relaxation of the heterochromatic chromocenter, consistent with a dynamic response. Arp2/3, the Arp2/3 activator Scar, and the myosin activator Unc45, are required for heterochromatin stability in polytene cells, suggesting that relocalization enables heterochromatin repair also in this tissue. Together, these studies reveal critical roles for actin polymerization and myosin motors in heterochromatin repair and genome stability across different organisms and tissue types.
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Affiliation(s)
- George Dialynas
- Department of Molecular and Computational Biology,
University
of Southern California, Los Angeles
90089, USA
| | - Laetitia Delabaere
- Department of Molecular and Computational Biology,
University
of Southern California, Los Angeles
90089, USA
| | - Irene Chiolo
- Department of Molecular and Computational Biology,
University
of Southern California, Los Angeles
90089, USA
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17
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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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18
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Li C, Danilowicz C, Tashjian TF, Godoy VG, Prévost C, Prentiss M. The positioning of Chi sites allows the RecBCD pathway to suppress some genomic rearrangements. Nucleic Acids Res 2019; 47:1836-1846. [PMID: 30544167 PMCID: PMC6393298 DOI: 10.1093/nar/gky1252] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 11/29/2018] [Accepted: 12/11/2018] [Indexed: 12/03/2022] Open
Abstract
Bacterial recombinational repair of double-strand breaks often begins with creation of initiating 3′ single-stranded DNA (ssDNA) tails on each side of a double-strand break (DSB). Importantly, if the RecBCD pathway is followed, RecBCD creates a gap between the sequences at 3′ ends of the initiating strands. The gap flanks the DSB and extends at least to the nearest Chi site on each strand. Once the initiating strands form ssDNA–RecA filaments, each ssDNA–RecA filament searches for homologous double-stranded DNA (dsDNA) to use as a template for the DNA synthesis needed to fill the gap created by RecBCD. Our experimental results show that the DNA synthesis requires formation of a heteroduplex dsDNA that pairs >20 contiguous bases in the initiating strand with sequence matched bases in a strand from the original dsDNA. To trigger synthesis, the heteroduplex must be near the 3′ end of the initiating strand. Those experimentally determined requirements for synthesis combined with the Chi site dependence of the function of RecBCD and the distribution of Chi sites in bacterial genomes could allow the RecBCD pathway to avoid some genomic rearrangements arising from directly induced DSBs; however, the same three factors could promote other rearrangements.
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Affiliation(s)
- Chastity Li
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | | | - Tommy F Tashjian
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Veronica G Godoy
- Department of Biology, Northeastern University, Boston, MA 02115, USA
| | - Chantal Prévost
- Laboratoire de BioChimie Théorique, CNRS UMR 9080, IBPC, Paris, France
| | - Mara Prentiss
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
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19
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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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20
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Chromatin control in double strand break repair. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019. [PMID: 30798938 DOI: 10.1016/bs.apcsb.2018.11.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2023]
Abstract
DNA double strand breaks (DSB) are the most deleterious type of damage inflicted on DNA by various environmental factors and as consequences of normal cellular metabolism. The multistep nature of DSB repair and the need to assemble large protein complexes at repair sites necessitate multiple chromatin changes there. This review focuses on the key findings of how chromatin regulators exert temporal and spatial control on DSB repair. These mechanisms coordinate repair with cell cycle progression, lead to DSB repair pathway choice, provide accessibility of repair machinery to damaged sites and move the lesions to nuclear environments permissive for repair.
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21
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Palecek JJ. SMC5/6: Multifunctional Player in Replication. Genes (Basel) 2018; 10:genes10010007. [PMID: 30583551 PMCID: PMC6356406 DOI: 10.3390/genes10010007] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 12/18/2018] [Accepted: 12/19/2018] [Indexed: 12/13/2022] Open
Abstract
The genome replication process is challenged at many levels. Replication must proceed through different problematic sites and obstacles, some of which can pause or even reverse the replication fork (RF). In addition, replication of DNA within chromosomes must deal with their topological constraints and spatial organization. One of the most important factors organizing DNA into higher-order structures are Structural Maintenance of Chromosome (SMC) complexes. In prokaryotes, SMC complexes ensure proper chromosomal partitioning during replication. In eukaryotes, cohesin and SMC5/6 complexes assist in replication. Interestingly, the SMC5/6 complexes seem to be involved in replication in many ways. They stabilize stalled RFs, restrain RF regression, participate in the restart of collapsed RFs, and buffer topological constraints during RF progression. In this (mini) review, I present an overview of these replication-related functions of SMC5/6.
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Affiliation(s)
- Jan J Palecek
- National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic.
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
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22
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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: 227] [Impact Index Per Article: 37.8] [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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23
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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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24
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Fortuny A, Polo SE. The response to DNA damage in heterochromatin domains. Chromosoma 2018; 127:291-300. [PMID: 29594515 PMCID: PMC6440646 DOI: 10.1007/s00412-018-0669-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 03/18/2018] [Accepted: 03/19/2018] [Indexed: 10/24/2022]
Abstract
Eukaryotic genomes are organized into chromatin, divided into structurally and functionally distinct euchromatin and heterochromatin compartments. The high level of compaction and the abundance of repeated sequences in heterochromatin pose multiple challenges for the maintenance of genome stability. Cells have evolved sophisticated and highly controlled mechanisms to overcome these constraints. Here, we summarize recent findings on how the heterochromatic state influences DNA damage formation, signaling, and repair. By focusing on distinct heterochromatin domains in different eukaryotic species, we highlight the heterochromatin contribution to the compartmentalization of DNA damage repair in the cell nucleus and to the repair pathway choice. We also describe the diverse chromatin alterations associated with the DNA damage response in heterochromatin domains and present our current understanding of their regulatory mechanisms. Finally, we discuss the biological significance and the evolutionary conservation of these processes.
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Affiliation(s)
- Anna Fortuny
- Epigenetics and Cell Fate Centre, UMR7216 CNRS, Paris Diderot University, Paris, France
| | - Sophie E Polo
- Epigenetics and Cell Fate Centre, UMR7216 CNRS, Paris Diderot University, Paris, France.
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25
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Caridi CP, Delabaere L, Tjong H, Hopp H, Das D, Alber F, Chiolo I. Quantitative Methods to Investigate the 4D Dynamics of Heterochromatic Repair Sites in Drosophila Cells. Methods Enzymol 2018. [PMID: 29523239 DOI: 10.1016/bs.mie.2017.11.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Heterochromatin is mostly composed of long stretches of repeated DNA sequences prone to ectopic recombination during double-strand break (DSB) repair. In Drosophila, "safe" homologous recombination (HR) repair of heterochromatic DSBs relies on a striking relocalization of repair sites to the nuclear periphery. Central to understanding heterochromatin repair is the ability to investigate the 4D dynamics (movement in space and time) of repair sites. A specific challenge of these studies is preventing phototoxicity and photobleaching effects while imaging the sample over long periods of time, and with sufficient time points and Z-stacks to track repair foci over time. Here we describe an optimized approach for high-resolution live imaging of heterochromatic DSBs in Drosophila cells, with a specific emphasis on the fluorescent markers and imaging setup used to capture the motion of repair foci over long-time periods. We detail approaches that minimize photobleaching and phototoxicity with a DeltaVision widefield deconvolution microscope, and image processing techniques for signal recovery postimaging using SoftWorX and Imaris software. We present a method to derive mean square displacement curves revealing some of the biophysical properties of the motion. Finally, we describe a method in R to identify tracts of directed motions (DMs) in mixed trajectories. These approaches enable a deeper understanding of the mechanisms of heterochromatin dynamics and genome stability in the three-dimensional context of the nucleus and have broad applicability in the field of nuclear dynamics.
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Affiliation(s)
| | | | - Harianto Tjong
- University of Southern California, Los Angeles, CA, United States
| | - Hannah Hopp
- University of Southern California, Los Angeles, CA, United States
| | - Devika Das
- University of Southern California, Los Angeles, CA, United States
| | - Frank Alber
- University of Southern California, Los Angeles, CA, United States
| | - Irene Chiolo
- University of Southern California, Los Angeles, CA, United States.
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26
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Lorković ZJ, Berger F. Heterochromatin and DNA damage repair: Use different histone variants and relax. Nucleus 2017; 8:583-588. [PMID: 29077523 DOI: 10.1080/19491034.2017.1384893] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Repair of damaged DNA requires the activation of kinases, which in turn phosphorylate diverse proteins including histone H2A.X, an event conserved from yeast to human. By combining genetics, biochemical, and cytological approaches, we recently reported that, in addition to H2A.X, phosphorylation of histone variant H2A.W.7 is required for DNA damage response in Arabidopsis. This work provides direct evidence for the functional diversification of plant-specific H2A.W histone variants, which are tightly associated with heterochromatin. We place our findings in perspective of other recent reports and discuss how DNA damage is being recognized and repaired in heterochromatin.
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Affiliation(s)
- Zdravko J Lorković
- a Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC) , Dr. Bohr-Gasse 3, Vienna , Austria
| | - Frédéric Berger
- a Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC) , Dr. Bohr-Gasse 3, Vienna , Austria
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27
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The evolutionarily conserved factor Sus1/ENY2 plays a role in telomere length maintenance. Curr Genet 2017; 64:635-644. [DOI: 10.1007/s00294-017-0778-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 11/02/2017] [Accepted: 11/03/2017] [Indexed: 11/26/2022]
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28
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Amaral N, Ryu T, Li X, Chiolo I. Nuclear Dynamics of Heterochromatin Repair. Trends Genet 2017; 33:86-100. [PMID: 28104289 DOI: 10.1016/j.tig.2016.12.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 12/19/2016] [Accepted: 12/20/2016] [Indexed: 01/09/2023]
Abstract
Repairing double-strand breaks (DSBs) is particularly challenging in pericentromeric heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination and chromosome rearrangements. Recent studies in Drosophila cells revealed that faithful homologous recombination (HR) repair of heterochromatic DSBs relies on the relocalization of DSBs to the nuclear periphery before Rad51 recruitment. We summarize here the exciting progress in understanding this pathway, including conserved responses in mammalian cells and surprising similarities with mechanisms in yeast that deal with DSBs in distinct sites that are difficult to repair, including other repeated sequences. We will also point out some of the most important open questions in the field and emerging evidence suggesting that deregulating these pathways might have dramatic consequences for human health.
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Affiliation(s)
- Nuno Amaral
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA
| | - Taehyun Ryu
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA
| | - Xiao Li
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA
| | - Irene Chiolo
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA 90089, USA.
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