1
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Parreno V, Loubiere V, Schuettengruber B, Fritsch L, Rawal CC, Erokhin M, Győrffy B, Normanno D, Di Stefano M, Moreaux J, Butova NL, Chiolo I, Chetverina D, Martinez AM, Cavalli G. Transient loss of Polycomb components induces an epigenetic cancer fate. Nature 2024; 629:688-696. [PMID: 38658752 DOI: 10.1038/s41586-024-07328-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 03/15/2024] [Indexed: 04/26/2024]
Abstract
Although cancer initiation and progression are generally associated with the accumulation of somatic mutations1,2, substantial epigenomic alterations underlie many aspects of tumorigenesis and cancer susceptibility3-6, suggesting that genetic mechanisms might not be the only drivers of malignant transformation7. However, whether purely non-genetic mechanisms are sufficient to initiate tumorigenesis irrespective of mutations has been unknown. Here, we show that a transient perturbation of transcriptional silencing mediated by Polycomb group proteins is sufficient to induce an irreversible switch to a cancer cell fate in Drosophila. This is linked to the irreversible derepression of genes that can drive tumorigenesis, including members of the JAK-STAT signalling pathway and zfh1, the fly homologue of the ZEB1 oncogene, whose aberrant activation is required for Polycomb perturbation-induced tumorigenesis. These data show that a reversible depletion of Polycomb proteins can induce cancer in the absence of driver mutations, suggesting that tumours can emerge through epigenetic dysregulation leading to inheritance of altered cell fates.
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Affiliation(s)
- V Parreno
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
| | - V Loubiere
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
- Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria
| | - B Schuettengruber
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
| | - L Fritsch
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
| | - C C Rawal
- University of Southern California, Los Angeles, CA, USA
| | - M Erokhin
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - B Győrffy
- Semmelweis University Department of Bioinformatics, Budapest, Hungary
- Department of Biophysics, Medical School, University of Pécs, Pécs, Hungary
| | - D Normanno
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
| | - M Di Stefano
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
| | - J Moreaux
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France
- Department of Biological Hematology, CHU Montpellier, Montpellier, France
- UFR Medicine, University of Montpellier, Montpellier, France
| | - N L Butova
- University of Southern California, Los Angeles, CA, USA
| | - I Chiolo
- University of Southern California, Los Angeles, CA, USA
| | - D Chetverina
- Institute of Gene Biology, Russian Academy of Sciences, Moscow, Russia
| | - A-M Martinez
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France.
| | - G Cavalli
- Institute of Human Genetics, CNRS, University of Montpellier, Montpellier, France.
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2
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Ryu T, Merigliano C, Chiolo I. Nup153 is not required for anchoring heterochromatic DSBs to the nuclear periphery. MicroPubl Biol 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] [What about the content of this article? (0)] [Affiliation(s)] [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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3
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Rawal CC, Loubiere V, Butova NL, Garcia J, Parreno V, Martinez AM, Cavalli G, Chiolo I. Sustained inactivation of the Polycomb PRC1 complex induces DNA repair defects and genomic instability in epigenetic tumors. Res Sq 2024:rs.3.rs-4289524. [PMID: 38746379 PMCID: PMC11092839 DOI: 10.21203/rs.3.rs-4289524/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Cancer initiation and progression are typically associated with the accumulation of driver mutations and genomic instability. However, recent studies demonstrated that cancers can also be purely initiated by epigenetic alterations, without driver mutations. Specifically, a 24-hours transient down-regulation of polyhomeotic (ph-KD), a core component of the Polycomb complex PRC1, is sufficient to drive epigenetically initiated cancers (EICs) in Drosophila, which are proficient in DNA repair and are characterized by a stable genome. Whether genomic instability eventually occurs when PRC1 down-regulation is performed for extended periods of time remains unclear. Here we show that prolonged depletion of a PRC1 component, which mimics cancer initiating events, results in broad dysregulation of DNA replication and repair genes, along with the accumulation of DNA breaks, defective repair, and widespread genomic instability in the cancer tissue. A broad mis-regulation of H2AK118 ubiquitylation and to a lesser extent of H3K27 trimethylation also occurs, and might contribute to these phenotypes. Together, this study supports a model where DNA repair and replication defects amplify the tumorigenic transformation epigenetically induced by PRC1 loss, resulting in genomic instability and cancer progression.
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4
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Palumbieri MD, Merigliano C, González-Acosta D, Kuster D, Krietsch J, Stoy H, von Känel T, Ulferts S, Welter B, Frey J, Doerdelmann C, Sanchi A, Grosse R, Chiolo I, Lopes M. Nuclear actin polymerization rapidly mediates replication fork remodeling upon stress by limiting PrimPol activity. Nat Commun 2023; 14:7819. [PMID: 38016948 PMCID: PMC10684888 DOI: 10.1038/s41467-023-43183-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 11/02/2023] [Indexed: 11/30/2023] Open
Abstract
Cells rapidly respond to replication stress actively slowing fork progression and inducing fork reversal. How replication fork plasticity is achieved in the context of nuclear organization is currently unknown. Using nuclear actin probes in living and fixed cells, we visualized nuclear actin filaments in unperturbed S phase and observed their rapid extension in number and length upon genotoxic treatments, frequently taking contact with replication factories. Chemically or genetically impairing nuclear actin polymerization shortly before these treatments prevents active fork slowing and abolishes fork reversal. Defective fork remodeling is linked to deregulated chromatin loading of PrimPol, which promotes unrestrained and discontinuous DNA synthesis and limits the recruitment of RAD51 and SMARCAL1 to nascent DNA. Moreover, defective nuclear actin polymerization upon mild replication interference induces chromosomal instability in a PRIMPOL-dependent manner. Hence, by limiting PrimPol activity, nuclear F-actin orchestrates replication fork plasticity and is a key molecular determinant in the rapid cellular response to genotoxic treatments.
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Affiliation(s)
| | - Chiara Merigliano
- Molecular and Computational Biology Department, University of Southern California, Los Angeles, CA, USA
| | | | - Danina Kuster
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Jana Krietsch
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Henriette Stoy
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
- Department of Cellular and Molecular Medicine, Copenhagen University, Copenhagen, Denmark
| | - Thomas von Känel
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Svenja Ulferts
- Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty, University of Freiburg, Freiburg im Breisgau, Germany
| | - Bettina Welter
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Joël Frey
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Cyril Doerdelmann
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Andrea Sanchi
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
| | - Robert Grosse
- Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty, 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.
| | - Massimo Lopes
- Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
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5
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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 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] [What about the content of this article? (0)] [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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6
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Palumbieri MD, Merigliano C, Acosta DG, von Känel T, Welter B, Stoy H, Krietsch J, Ulferts S, Sanchi A, Grosse R, Chiolo I, Lopes M. Replication fork plasticity upon replication stress requires rapid nuclear actin polymerization. bioRxiv 2023:2023.03.24.534097. [PMID: 36993227 PMCID: PMC10055433 DOI: 10.1101/2023.03.24.534097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Cells rapidly respond to replication stress actively slowing fork progression and inducing fork reversal. How replication fork plasticity is achieved in the context of nuclear organization is currently unknown. Using nuclear actin probes in living and fixed cells, we visualized nuclear actin filaments in unperturbed S phase, rapidly extending in number and thickness upon genotoxic treatments, and taking frequent contact with replication factories. Chemically or genetically impairing nuclear actin polymerization shortly before these treatments prevents active fork slowing and abolishes fork reversal. Defective fork plasticity is linked to reduced recruitment of RAD51 and SMARCAL1 to nascent DNA. Conversely, PRIMPOL gains access to replicating chromatin, promoting unrestrained and discontinuous DNA synthesis, which is associated with increased chromosomal instability and decreased cellular resistance to replication stress. Hence, nuclear F-actin orchestrates replication fork plasticity and is a key molecular determinant in the rapid cellular response to genotoxic treatments.
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7
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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8
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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9
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Merigliano C, Burla R, La Torre M, Del Giudice S, Teo H, Liew CW, Chojnowski A, Goh WI, Olmos Y, Maccaroni K, Giubettini M, Chiolo I, Carlton JG, Raimondo D, Vernì F, Stewart CL, Rhodes D, Wright GD, Burke BE, Saggio I. AKTIP interacts with ESCRT I and is needed for the recruitment of ESCRT III subunits to the midbody. PLoS Genet 2021; 17:e1009757. [PMID: 34449766 PMCID: PMC8428793 DOI: 10.1371/journal.pgen.1009757] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 09/09/2021] [Accepted: 08/04/2021] [Indexed: 11/18/2022] Open
Abstract
To complete mitosis, the bridge that links the two daughter cells needs to be cleaved. This step is carried out by the endosomal sorting complex required for transport (ESCRT) machinery. AKTIP, a protein discovered to be associated with telomeres and the nuclear membrane in interphase cells, shares sequence similarities with the ESCRT I component TSG101. Here we present evidence that during mitosis AKTIP is part of the ESCRT machinery at the midbody. AKTIP interacts with the ESCRT I subunit VPS28 and forms a circular supra-structure at the midbody, in close proximity with TSG101 and VPS28 and adjacent to the members of the ESCRT III module CHMP2A, CHMP4B and IST1. Mechanistically, the recruitment of AKTIP is dependent on MKLP1 and independent of CEP55. AKTIP and TSG101 are needed together for the recruitment of the ESCRT III subunit CHMP4B and in parallel for the recruitment of IST1. Alone, the reduction of AKTIP impinges on IST1 and causes multinucleation. Our data altogether reveal that AKTIP is a component of the ESCRT I module and functions in the recruitment of ESCRT III components required for abscission. To complete cell division, the bridge that links the two daughter cells needs to be cleaved. This step is carried out by a machinery named “endosomal sorting complex required for transport” (ESCRT). The dissection of this machinery is important in basic biology and for investigating diseases in which cell division is altered. AKTIP, a factor discovered to be needed for chromosome integrity, shares similarities with a component of the ESCRT machinery named TSG101. Here we present evidence that AKTIP is part of the ESCRT machinery, as TSG101. More specifically, we show that AKTIP physically interacts with members of the ESCRT machinery and forms a characteristic circular structure at the center of the bridge linking the daughter cells. We also show that the reduction of AKTIP levels causes defects in the assembly of the ESCRT machinery and in cell division. In future work, it will be interesting to investigate the association of AKTIP with cancer, because in tumorigenesis cell division is altered and since an implication in cancer has been described for TSG101 and other ESCRT factors.
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Affiliation(s)
| | - Romina Burla
- Sapienza University Dept. Biology and Biotechnology, Rome, Italy
- CNR Institute of Molecular Biology and Pathology, Rome, Italy
| | - Mattia La Torre
- Sapienza University Dept. Biology and Biotechnology, Rome, Italy
| | | | - Hsiangling Teo
- Institute of Structural Biology, Nanyang Technological University, Singapore
| | - Chong Wai Liew
- Institute of Structural Biology, Nanyang Technological University, Singapore
| | - Alexandre Chojnowski
- A*STAR, Developmental and Regenerative Biology, ASLR, Agency for Science, Technology and Research, Singapore
- A*STAR, Singapore Nuclear Dynamics and Architecture, ASLR Skin Research Labs, Agency for Science, Technology and Research, Singapore
| | - Wah Ing Goh
- A*STAR Microscopy Platform, Research Support Centre, Agency for Science, Technology and Research, Singapore
| | - Yolanda Olmos
- School of Cancer and Pharmaceutical Sciences, King’s College London, London, United Kingdom
- Organelle Dynamics Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Klizia Maccaroni
- Sapienza University Dept. Biology and Biotechnology, Rome, Italy
| | | | - Irene Chiolo
- University of Southern California, Molecular and Computational Biology Dept., Los Angeles, California, United States of America
| | - Jeremy G. Carlton
- School of Cancer and Pharmaceutical Sciences, King’s College London, London, United Kingdom
- Organelle Dynamics Laboratory, The Francis Crick Institute, London, United Kingdom
| | | | - Fiammetta Vernì
- Sapienza University Dept. Biology and Biotechnology, Rome, Italy
| | - Colin L. Stewart
- A*STAR, Developmental and Regenerative Biology, ASLR, Agency for Science, Technology and Research, Singapore
- Dept. of Physiology National University of Singapore, Singapore
| | - Daniela Rhodes
- Institute of Structural Biology, Nanyang Technological University, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Graham D. Wright
- A*STAR Microscopy Platform, Research Support Centre, Agency for Science, Technology and Research, Singapore
| | - Brian E. Burke
- A*STAR, Singapore Nuclear Dynamics and Architecture, ASLR Skin Research Labs, Agency for Science, Technology and Research, Singapore
| | - Isabella Saggio
- Sapienza University Dept. Biology and Biotechnology, Rome, Italy
- CNR Institute of Molecular Biology and Pathology, Rome, Italy
- Institute of Structural Biology, Nanyang Technological University, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
- * E-mail:
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10
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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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11
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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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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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13
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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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14
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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15
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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16
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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17
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Li Q, Tjong H, Li X, Gong K, Zhou XJ, Chiolo I, Alber F. The three-dimensional genome organization of Drosophila melanogaster through data integration. Genome Biol 2017; 18:145. [PMID: 28760140 PMCID: PMC5576134 DOI: 10.1186/s13059-017-1264-5] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Accepted: 06/26/2017] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Genome structures are dynamic and non-randomly organized in the nucleus of higher eukaryotes. To maximize the accuracy and coverage of three-dimensional genome structural models, it is important to integrate all available sources of experimental information about a genome's organization. It remains a major challenge to integrate such data from various complementary experimental methods. Here, we present an approach for data integration to determine a population of complete three-dimensional genome structures that are statistically consistent with data from both genome-wide chromosome conformation capture (Hi-C) and lamina-DamID experiments. RESULTS Our structures resolve the genome at the resolution of topological domains, and reproduce simultaneously both sets of experimental data. Importantly, this data deconvolution framework allows for structural heterogeneity between cells, and hence accounts for the expected plasticity of genome structures. As a case study we choose Drosophila melanogaster embryonic cells, for which both data types are available. Our three-dimensional genome structures have strong predictive power for structural features not directly visible in the initial data sets, and reproduce experimental hallmarks of the D. melanogaster genome organization from independent and our own imaging experiments. Also they reveal a number of new insights about genome organization and its functional relevance, including the preferred locations of heterochromatic satellites of different chromosomes, and observations about homologous pairing that cannot be directly observed in the original Hi-C or lamina-DamID data. CONCLUSIONS Our approach allows systematic integration of Hi-C and lamina-DamID data for complete three-dimensional genome structure calculation, while also explicitly considering genome structural variability.
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Affiliation(s)
- Qingjiao Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Harianto Tjong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Xiao Li
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Ke Gong
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA
| | - Xianghong Jasmine Zhou
- Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California, Los Angeles, USA
| | - Irene Chiolo
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA.
| | - Frank Alber
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, 1050 Childs Way, Los Angeles, CA, 90089, USA.
- Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, 90089, USA.
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18
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Delabaere L, Ertl HA, Massey DJ, Hofley CM, Sohail F, Bienenstock EJ, Sebastian H, Chiolo I, LaRocque JR. Aging impairs double-strand break repair by homologous recombination in Drosophila germ cells. Aging Cell 2017; 16:320-328. [PMID: 28000382 PMCID: PMC5334535 DOI: 10.1111/acel.12556] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/14/2016] [Indexed: 12/23/2022] Open
Abstract
Aging is characterized by genome instability, which contributes to cancer formation and cell lethality leading to organismal decline. The high levels of DNA double-strand breaks (DSBs) observed in old cells and premature aging syndromes are likely a primary source of genome instability, but the underlying cause of their formation is still unclear. DSBs might result from higher levels of damage or repair defects emerging with advancing age, but repair pathways in old organisms are still poorly understood. Here, we show that premeiotic germline cells of young and old flies have distinct differences in their ability to repair DSBs by the error-free pathway homologous recombination (HR). Repair of DSBs induced by either ionizing radiation (IR) or the endonuclease I-SceI is markedly defective in older flies. This correlates with a remarkable reduction in HR repair measured with the DR-white DSB repair reporter assay. Strikingly, most of this repair defect is already present at 8 days of age. Finally, HR defects correlate with increased expression of early HR components and increased recruitment of Rad51 to damage in older organisms. Thus, we propose that the defect in the HR pathway for germ cells in older flies occurs following Rad51 recruitment. These data reveal that DSB repair defects arise early in the aging process and suggest that HR deficiencies are a leading cause of genome instability in germ cells of older animals.
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Affiliation(s)
- Laetitia Delabaere
- Molecular and Computational Biology Department; University of Southern California; Los Angeles CA 90089 USA
| | - Henry A. Ertl
- Department of Human Science; Georgetown University Medical Center; Washington DC 20057 USA
| | - Dashiell J. Massey
- Department of Human Science; Georgetown University Medical Center; Washington DC 20057 USA
| | - Carolyn M. Hofley
- Department of Human Science; Georgetown University Medical Center; Washington DC 20057 USA
| | - Faraz Sohail
- Department of Human Science; Georgetown University Medical Center; Washington DC 20057 USA
| | - Elisa J. Bienenstock
- Department of Human Science; Georgetown University Medical Center; Washington DC 20057 USA
- College of Public Service & Community Solutions; Arizona State University; Phoenix AZ 85004 USA
| | - Hans Sebastian
- Molecular and Computational Biology Department; University of Southern California; Los Angeles CA 90089 USA
| | - Irene Chiolo
- Molecular and Computational Biology Department; University of Southern California; Los Angeles CA 90089 USA
| | - Jeannine R. LaRocque
- Department of Human Science; Georgetown University Medical Center; Washington DC 20057 USA
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19
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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20
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Abstract
Repairing double-strand breaks (DSBs) is particularly challenging in heterochromatin, where the abundance of repeated sequences exacerbates the risk of ectopic recombination and chromosome rearrangements. In Drosophila cells, faithful homologous recombination (HR) repair of heterochromatic DSBs relies on a specialized pathway that relocalizes repair sites to the nuclear periphery before Rad51 recruitment. Here we show that HR progression is initially blocked inside the heterochromatin domain by SUMOylation and the coordinated activity of two distinct Nse2 SUMO E3 ligases: Quijote (Qjt) and Cervantes (Cerv). In addition, the SUMO-targeted ubiquitin ligase (STUbL) Dgrn, but not its partner dRad60, is recruited to heterochromatic DSBs at early stages of repair and mediates relocalization. However, Dgrn is not required to prevent Rad51 recruitment inside the heterochromatin domain, suggesting that the block to HR progression inside the domain and relocalization to the nuclear periphery are genetically separable pathways. Further, SUMOylation defects affect relocalization without blocking heterochromatin expansion, revealing that expansion is not required for relocalization. Finally, nuclear pores and inner nuclear membrane proteins (INMPs) anchor STUbL/RENi components and repair sites to the nuclear periphery, where repair continues. Together, these studies reveal a critical role of SUMOylation and nuclear architecture in the spatial and temporal regulation of heterochromatin repair and the protection of genome integrity.
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Affiliation(s)
- Taehyun Ryu
- a University of Southern California , Molecular and Computational Biology Department , Los Angeles , CA , USA
| | - Melissa R Bonner
- a University of Southern California , Molecular and Computational Biology Department , Los Angeles , CA , USA
| | - Irene Chiolo
- a University of Southern California , Molecular and Computational Biology Department , Los Angeles , CA , USA
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21
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Affiliation(s)
- Laetitia Delabaere
- a Molecular and Computational Biology Department , University of Southern California , Los Angeles , CA , USA
| | - Irene Chiolo
- a Molecular and Computational Biology Department , University of Southern California , Los Angeles , CA , USA
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22
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Robert T, Vanoli F, Chiolo I, Shubassi G, Bernstein KA, Rothstein R, Botrugno OA, Parazzoli D, Oldani A, Minucci S, Foiani M. HDACs link the DNA damage response, processing of double-strand breaks and autophagy. Nature 2011; 471:74-79. [PMID: 21368826 DOI: 10.1038/nature09803] [Citation(s) in RCA: 309] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 01/11/2011] [Indexed: 11/09/2022]
Abstract
Protein acetylation is mediated by histone acetyltransferases (HATs) and deacetylases (HDACs), which influence chromatin dynamics, protein turnover and the DNA damage response. ATM and ATR mediate DNA damage checkpoints by sensing double-strand breaks and single-strand-DNA-RFA nucleofilaments, respectively. However, it is unclear how acetylation modulates the DNA damage response. Here we show that HDAC inhibition/ablation specifically counteracts yeast Mec1 (orthologue of human ATR) activation, double-strand-break processing and single-strand-DNA-RFA nucleofilament formation. Moreover, the recombination protein Sae2 (human CtIP) is acetylated and degraded after HDAC inhibition. Two HDACs, Hda1 and Rpd3, and one HAT, Gcn5, have key roles in these processes. We also find that HDAC inhibition triggers Sae2 degradation by promoting autophagy that affects the DNA damage sensitivity of hda1 and rpd3 mutants. Rapamycin, which stimulates autophagy by inhibiting Tor, also causes Sae2 degradation. We propose that Rpd3, Hda1 and Gcn5 control chromosome stability by coordinating the ATR checkpoint and double-strand-break processing with autophagy.
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Affiliation(s)
- Thomas Robert
- Fondazione IFOM (Istituto FIRC di Oncologia Molecolare), IFOM-IEO Campus, via Adamello 16, Milan 20139, Italy
| | - Fabio Vanoli
- Fondazione IFOM (Istituto FIRC di Oncologia Molecolare), IFOM-IEO Campus, via Adamello 16, Milan 20139, Italy
| | - Irene Chiolo
- Fondazione IFOM (Istituto FIRC di Oncologia Molecolare), IFOM-IEO Campus, via Adamello 16, Milan 20139, Italy.,LBNL, Department of Genome Biology, Berkeley, California 94710-2722, USA
| | - Ghadeer Shubassi
- Fondazione IFOM (Istituto FIRC di Oncologia Molecolare), IFOM-IEO Campus, via Adamello 16, Milan 20139, Italy
| | - Kara A Bernstein
- Department of Genetics and Development, Columbia University Medical Center, New York, New York 10032-2704, USA
| | - Rodney Rothstein
- Department of Genetics and Development, Columbia University Medical Center, New York, New York 10032-2704, USA
| | | | | | | | - Saverio Minucci
- European Institute of Oncology, IFOM-IEO campus, Milan 20139, Italy.,DSBB-Università degli Studi di Milano, Milan 20139, Italy
| | - Marco Foiani
- Fondazione IFOM (Istituto FIRC di Oncologia Molecolare), IFOM-IEO Campus, via Adamello 16, Milan 20139, Italy.,DSBB-Università degli Studi di Milano, Milan 20139, Italy
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23
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Costes SV, Chiolo I, Pluth JM, Barcellos-Hoff MH, Jakob B. Spatiotemporal characterization of ionizing radiation induced DNA damage foci and their relation to chromatin organization. Mutat Res 2010; 704:78-87. [PMID: 20060491 DOI: 10.1016/j.mrrev.2009.12.006] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/17/2009] [Accepted: 12/22/2009] [Indexed: 11/28/2022]
Abstract
DNA damage sensing proteins have been shown to localize to the sites of DNA double strand breaks (DSB) within seconds to minutes following ionizing radiation (IR) exposure, resulting in the formation of microscopically visible nuclear domains referred to as radiation-induced foci (RIF). This review characterizes the spatiotemporal properties of RIF at physiological doses, minutes to hours following exposure to ionizing radiation, and it proposes a model describing RIF formation and resolution as a function of radiation quality and chromatin territories. Discussion is limited to RIF formed by three interrelated proteins ATM (Ataxia telangiectasia mutated), 53BP1 (p53 binding protein 1) and gammaH2AX (phosphorylated variant histone H2AX), with an emphasis on the later. This review discusses the importance of not equating RIF with DSB in all situations and shows how dose and time dependence of RIF frequency is inconsistent with a one to one equivalence. Instead, we propose that RIF mark regions of the chromatin that would serve as scaffolds rigid enough to keep broken DNA from diffusing away, but open enough to allow the repair machinery to access the damage site. We review data indicating clear kinetic and physical differences between RIF emerging from dense and uncondensed regions of the nucleus. We suggest that persistent RIF observed days following exposure to ionizing radiation are nuclear marks of permanent rearrangement of the chromatin architecture. Such chromatin alterations may not always lead to growth arrest as cells have been shown to replicate these in progeny. Thus, heritable persistent RIF spanning over tens of Mbp may reflect persistent changes in the transcriptome of a large progeny of cells. Such model opens the door to a "non-DNA-centric view" of radiation-induced phenotypes.
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Affiliation(s)
- S V Costes
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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24
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Chiolo I, Saponaro M, Baryshnikova A, Kim JH, Seo YS, Liberi G. The human F-Box DNA helicase FBH1 faces Saccharomyces cerevisiae Srs2 and postreplication repair pathway roles. Mol Cell Biol 2007; 27:7439-50. [PMID: 17724085 PMCID: PMC2169053 DOI: 10.1128/mcb.00963-07] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Saccharomyces cerevisiae Srs2 UvrD DNA helicase controls genome integrity by preventing unscheduled recombination events. While Srs2 orthologues have been identified in prokaryotic and lower eukaryotic organisms, human orthologues of Srs2 have not been described so far. We found that the human F-box DNA helicase hFBH1 suppresses specific recombination defects of S. cerevisiae srs2 mutants, consistent with the finding that the helicase domain of hFBH1 is highly conserved with that of Srs2. Surprisingly, hFBH1 in the absence of SRS2 also suppresses the DNA damage sensitivity caused by inactivation of postreplication repair-dependent functions leading to PCNA ubiquitylation. The F-box domain of hFBH1, which is not present in Srs2, is crucial for hFBH1 functions in substituting for Srs2 and postreplication repair factors. Furthermore, our findings indicate that an intact F-box domain, acting as an SCF ubiquitin ligase, is required for the DNA damage-induced degradation of hFBH1 itself. Overall, our findings suggest that the hFBH1 helicase is a functional human orthologue of budding yeast Srs2 that also possesses self-regulation properties necessary to execute its recombination functions.
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Affiliation(s)
- Irene Chiolo
- FIRC Institute of Molecular Oncology Foundation, Via Adamello 16, 20139 Milan, Italy
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25
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Chiolo I, Carotenuto W, Maffioletti G, Petrini JHJ, Foiani M, Liberi G. Srs2 and Sgs1 DNA helicases associate with Mre11 in different subcomplexes following checkpoint activation and CDK1-mediated Srs2 phosphorylation. Mol Cell Biol 2005; 25:5738-51. [PMID: 15964827 PMCID: PMC1156977 DOI: 10.1128/mcb.25.13.5738-5751.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mutations in the genes encoding the BLM and WRN RecQ DNA helicases and the MRE11-RAD50-NBS1 complex lead to genome instability and cancer predisposition syndromes. The Saccharomyces cerevisiae Sgs1 RecQ helicase and the Mre11 protein, together with the Srs2 DNA helicase, prevent chromosome rearrangements and are implicated in the DNA damage checkpoint response and in DNA recombination. By searching for Srs2 physical interactors, we have identified Sgs1 and Mre11. We show that Srs2, Sgs1, and Mre11 form a large complex, likely together with yet unidentified proteins. This complex reorganizes into Srs2-Mre11 and Sgs1-Mre11 subcomplexes following DNA damage-induced activation of the Mec1 and Tel1 checkpoint kinases. The defects in subcomplex formation observed in mec1 and tel1 cells can be recapitulated in srs2-7AV mutants that are hypersensitive to intra-S DNA damage and are altered in the DNA damage-induced and Cdk1-dependent phosphorylation of Srs2. Altogether our observations indicate that Mec1- and Tel1-dependent checkpoint pathways modulate the functional interactions between Srs2, Sgs1, and Mre11 and that the Srs2 DNA helicase represents an important target of the Cdk1-mediated cellular response induced by DNA damage.
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Affiliation(s)
- Irene Chiolo
- FIRC Institute of Molecular Oncology Foundation, Via Adamello 16, 20139, Milan, Italy
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26
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Liberi G, Maffioletti G, Lucca C, Chiolo I, Baryshnikova A, Cotta-Ramusino C, Lopes M, Pellicioli A, Haber JE, Foiani M. Rad51-dependent DNA structures accumulate at damaged replication forks in sgs1 mutants defective in the yeast ortholog of BLM RecQ helicase. Genes Dev 2005; 19:339-50. [PMID: 15687257 PMCID: PMC546512 DOI: 10.1101/gad.322605] [Citation(s) in RCA: 266] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
S-phase cells overcome chromosome lesions through replication-coupled recombination processes that seem to be assisted by recombination-dependent DNA structures and/or replication-related sister chromatid junctions. RecQ helicases, including yeast Sgs1 and human BLM, have been implicated in both replication and recombination and protect genome integrity by preventing unscheduled mitotic recombination events. We have studied the RecQ helicase-mediated mechanisms controlling genome stability by analyzing replication forks encountering a damaged template in sgs1 cells. We show that, in sgs1 mutants, recombination-dependent cruciform structures accumulate at damaged forks. Their accumulation requires Rad51 protein, is counteracted by Srs2 DNA helicase, and does not prevent fork movement. Sgs1, but not Srs2, promotes resolution of these recombination intermediates. A functional Rad53 checkpoint kinase that is known to protect the integrity of the sister chromatid junctions is required for the accumulation of recombination intermediates in sgs1 mutants. Finally, top3 and top3 sgs1 mutants accumulate the same structures as sgs1 cells. We suggest that, in sgs1 cells, the unscheduled accumulation of Rad51-dependent cruciform structures at damaged forks result from defective maturation of recombination-dependent intermediates that originate from the replication-related sister chromatid junctions. Our findings might contribute to explaining some of the recombination defects of BLM cells.
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Affiliation(s)
- Giordano Liberi
- F.I.R.C. Institute of Molecular Oncology Foundation, 20141, Milan, Italy.
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27
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Liberi G, Chiolo I, Pellicioli A, Lopes M, Plevani P, Muzi-Falconi M, Foiani M. Srs2 DNA helicase is involved in checkpoint response and its regulation requires a functional Mec1-dependent pathway and Cdk1 activity. EMBO J 2000; 19:5027-38. [PMID: 10990466 PMCID: PMC314228 DOI: 10.1093/emboj/19.18.5027] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In Saccharomyces cerevisiae the rate of DNA replication is slowed down in response to DNA damage as a result of checkpoint activation, which is mediated by the Mec1 and Rad53 protein kinases. We found that the Srs2 DNA helicase, which is involved in DNA repair and recombination, is phosphorylated in response to intra-S DNA damage in a checkpoint-dependent manner. DNA damage-induced Srs2 phosphorylation also requires the activity of the cyclin-dependent kinase Cdk1, suggesting that the checkpoint pathway might modulate Cdk1 activity in response to DNA damage. Moreover, srs2 mutants fail to activate Rad53 properly and to slow down DNA replication in response to intra-S DNA damage. The residual Rad53 activity observed in srs2 cells depends upon the checkpoint proteins Rad17 and Rad24. Moreover, DNA damage-induced lethality in rad17 mutants depends partially upon Srs2, suggesting that a functional Srs2 helicase causes accumulation of lethal events in a checkpoint-defective context. Altogether, our data implicate Srs2 in the Mec1 and Rad53 pathway and connect the checkpoint response to DNA repair and recombination.
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Affiliation(s)
- G Liberi
- Dipartimento di Genetica e di Biologia dei Microrganismi, Università degli Studi di Milano, via Celoria 26, 20133 Milan, Italy.
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