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Merigliano C, Ryu T, See CD, Caridi CP, Li X, Butova NL, Reynolds TW, Deng C, Chenoweth DM, Capelson M, Chiolo I. "Off-pore" nucleoporins relocalize heterochromatic breaks through phase separation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.07.570729. [PMID: 39071440 PMCID: PMC11275802 DOI: 10.1101/2023.12.07.570729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
Phase separation forms membraneless compartments in the nuclei, including by establishing heterochromatin "domains" and repair foci. Pericentromeric heterochromatin mostly comprises repeated sequences prone to aberrant recombination, and "safe" homologous recombination (HR) repair of these sequences requires the movement of repair sites to the nuclear periphery before Rad51 recruitment and strand invasion. How this mobilization initiates is unknown, and the contribution of phase separation to these dynamics is unclear. Here, we show that Nup98 nucleoporin is recruited to heterochromatic repair sites before relocalization through Sec13 or Nup88 nucleoporins, and downstream from the Smc5/6 complex and SUMOylation. Remarkably, the phase separation properties of Nup98 are required and sufficient to mobilize repair sites and exclude Rad51, thus preventing aberrant recombination while promoting HR repair. Disrupting this pathway results in heterochromatin repair defects and widespread chromosome rearrangements, revealing a novel "off-pore" role for nucleoporins and phase separation in nuclear dynamics and genome integrity in a multicellular eukaryote.
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Affiliation(s)
- Chiara Merigliano
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
| | - Taehyun Ryu
- Harvard Medical School, Department of Genetics, Boston, MA, USA
| | - Colby D. See
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
| | - Christopher P. Caridi
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
| | - Xiao Li
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
| | - Nadejda L. Butova
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
| | - Trevor W. Reynolds
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
| | - Changfeng Deng
- University of Pennsylvania, Department of Chemistry, School of Arts and Sciences, Philadelphia, PA, USA
| | - David M. Chenoweth
- University of Pennsylvania, Department of Chemistry, School of Arts and Sciences, Philadelphia, PA, USA
| | - Maya Capelson
- San Diego State University, Department of Biology, San Diego, CA, USA
| | - Irene Chiolo
- University of Southern California, Molecular and Computational Biology Department, Los Angeles, CA, USA
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2
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Ferchiou S, Caza F, Villemur R, Betoulle S, St-Pierre Y. From shells to sequences: A proof-of-concept study for on-site analysis of hemolymphatic circulating cell-free DNA from sentinel mussels using Nanopore technology. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 934:172969. [PMID: 38754506 DOI: 10.1016/j.scitotenv.2024.172969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 04/30/2024] [Accepted: 05/01/2024] [Indexed: 05/18/2024]
Abstract
Blue mussels are often abundant and widely distributed in polar marine coastal ecosystems. Because of their wide distribution, ecological importance, and relatively stationary lifestyle, bivalves have long been considered suitable indicators of ecosystem health and changes. Monitoring the population dynamics of blue mussels can provide information on the overall biodiversity, species interactions, and ecosystem functioning. In the present work, we combined the concept of liquid biopsy (LB), an emerging concept in medicine based on the sequencing of free circulating DNA, with the Oxford Nanopore Technologies (ONT) platform using a portable laboratory in a remote area. Our results demonstrate that this platform is ideally suited for sequencing hemolymphatic circulating cell-free DNA (ccfDNA) fragments found in blue mussels. The percentage of non-self ccfDNA accounted for >50 % of ccfDNA at certain sampling Sites, allowing the quick, on-site acquisition of a global view of the biodiversity of a coastal marine ecosystem. These ccfDNA fragments originated from viruses, bacteria, plants, arthropods, algae, and multiple Chordata. Aside from non-self ccfDNA, we found DNA fragments from all 14 blue mussel chromosomes, as well as those originating from the mitochondrial genomes. However, the distribution of nuclear and mitochondrial DNA was significantly different between Sites. Similarly, analyses between various sampling Sites showed that the biodiversity varied significantly within microhabitats. Our work shows that the ONT platform is well-suited for LB in sentinel blue mussels in remote and challenging conditions, enabling faster fieldwork for conservation strategies and resource management in diverse settings.
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Affiliation(s)
- Sophia Ferchiou
- INRS-Centre Armand-Frappier Santé Technologie, 531 Boul. des Prairies, Laval, QC H7V 1B7, Canada
| | - France Caza
- INRS-Centre Armand-Frappier Santé Technologie, 531 Boul. des Prairies, Laval, QC H7V 1B7, Canada
| | - Richard Villemur
- INRS-Centre Armand-Frappier Santé Technologie, 531 Boul. des Prairies, Laval, QC H7V 1B7, Canada
| | - Stéphane Betoulle
- Université Reims Champagne-Ardenne, UMR-I 02 SEBIO Stress environnementaux et Biosurveillance des milieux aquatiques, Campus Moulin de la Housse, 51687 Reims, France
| | - Yves St-Pierre
- INRS-Centre Armand-Frappier Santé Technologie, 531 Boul. des Prairies, Laval, QC H7V 1B7, Canada.
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3
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Hatanaka R, Tamagawa K, Haruta N, Sugimoto A. The impact of differential transposition activities of autonomous and nonautonomous hAT transposable elements on genome architecture and gene expression in Caenorhabditis inopinata. Genetics 2024; 227:iyae052. [PMID: 38577765 DOI: 10.1093/genetics/iyae052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 01/08/2024] [Accepted: 03/28/2024] [Indexed: 04/06/2024] Open
Abstract
Transposable elements are DNA sequences capable of moving within genomes and significantly influence genomic evolution. The nematode Caenorhabditis inopinata exhibits a much higher transposable element copy number than its sister species, Caenorhabditis elegans. In this study, we identified a novel autonomous transposable element belonging to the hAT superfamily from a spontaneous transposable element-insertion mutant in C. inopinata and named this transposon Ci-hAT1. Further bioinformatic analyses uncovered 3 additional autonomous hAT elements-Ci-hAT2, Ci-hAT3, and Ci-hAT4-along with over 1,000 copies of 2 nonautonomous miniature inverted-repeat transposable elements, mCi-hAT1 and mCi-hAT4, likely derived from Ci-hAT1 and Ci-hAT4 through internal deletion. We tracked at least 3 sequential transpositions of Ci-hAT1 over several years. However, the transposition rates of the other 3 autonomous hAT elements were lower, suggesting varying activity levels. Notably, the distribution patterns of the 2 miniature inverted-repeat transposable element families differed significantly: mCi-hAT1 was primarily located in the chromosome arms, a pattern observed in the transposable elements of other Caenorhabditis species, whereas mCi-hAT4 was more evenly distributed across chromosomes. Additionally, interspecific transcriptome analysis indicated that C. inopinata genes with upstream or intronic these miniature inverted-repeat transposable element insertions tend to be more highly expressed than their orthologous genes in C. elegans. These findings highlight the significant role of de-silenced transposable elements in driving the evolution of genomes and transcriptomes, leading to species-specific genetic diversity.
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Affiliation(s)
- Ryuhei Hatanaka
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Katsunori Tamagawa
- Laboratory of Evolutionary Genomics, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Nami Haruta
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
| | - Asako Sugimoto
- Laboratory of Developmental Dynamics, Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan
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4
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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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5
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Flynn JM, Yamashita YM. The implications of satellite DNA instability on cellular function and evolution. Semin Cell Dev Biol 2024; 156:152-159. [PMID: 37852904 DOI: 10.1016/j.semcdb.2023.10.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Revised: 09/21/2023] [Accepted: 10/11/2023] [Indexed: 10/20/2023]
Abstract
Abundant tandemly repeated satellite DNA is present in most eukaryotic genomes. Previous limitations including a pervasive view that it was uninteresting junk DNA, combined with challenges in studying it, are starting to dissolve - and recent studies have found important functions for satellite DNAs. The observed rapid evolution and implied instability of satellite DNA now has important significance for their functions and maintenance within the genome. In this review, we discuss the processes that lead to satellite DNA copy number instability, and the importance of mechanisms to manage the potential negative effects of instability. Satellite DNA is vulnerable to challenges during replication and repair, since it forms difficult-to-process secondary structures and its homology within tandem arrays can result in various types of recombination. Satellite DNA instability may be managed by DNA or chromatin-binding proteins ensuring proper nuclear localization and repair, or by proteins that process aberrant structures that satellite DNAs tend to form. We also discuss the pattern of satellite DNA mutations from recent mutation accumulation (MA) studies that have tracked changes in satellite DNA for up to 1000 generations with minimal selection. Finally, we highlight examples of satellite evolution from studies that have characterized satellites across millions of years of Drosophila fruit fly evolution, and discuss possible ways that selection might act on the satellite DNA composition.
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Affiliation(s)
- Jullien M Flynn
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA; Howard Hughes Medical Institute, Cambridge, MA, USA.
| | - Yukiko M Yamashita
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA; Howard Hughes Medical Institute, Cambridge, MA, USA; Massachusetts Institute of Technology, Cambridge, MA, USA.
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6
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Deshpande P, Prentice E, Ceballos AV, Casaccia P, Elbaum-Garfinkle S. Modified histone peptides uniquely tune the material properties of HP1α condensates. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.07.579285. [PMID: 38370661 PMCID: PMC10871333 DOI: 10.1101/2024.02.07.579285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Biomolecular condensates have emerged as a powerful new paradigm in cell biology with broad implications to human health and disease, particularly in the nucleus where phase separation is thought to underly elements of chromatin organization and regulation. Specifically, it has been recently reported that phase separation of heterochromatin protein 1alpha (HP1α) with DNA contributes to the formation of condensed chromatin states. HP1α localization to heterochromatic regions is mediated by its binding to specific repressive marks on the tail of histone H3, such as trimethylated lysine 9 on histone H3 (H3K9me3). However, whether epigenetic marks play an active role in modulating the material properties of HP1α and dictating emergent functions of its condensates, remains only partially understood. Here, we leverage a reductionist system, comprised of modified and unmodified histone H3 peptides, HP1α and DNA to examine the contribution of specific epigenetic marks to phase behavior of HP1α. We show that the presence of histone peptides bearing the repressive H3K9me3 is compatible with HP1α condensates, while peptides containing unmodified residues or bearing the transcriptional activation mark H3K4me3 are incompatible with HP1α phase separation. In addition, inspired by the decreased ratio of nuclear H3K9me3 to HP1α detected in cells exposed to uniaxial strain, using fluorescence microscopy and rheological approaches we demonstrate that H3K9me3 histone peptides modulate the dynamics and network properties of HP1α condensates in a concentration dependent manner. These data suggest that HP1α-DNA condensates are viscoelastic materials, whose properties may provide an explanation for the dynamic behavior of heterochromatin in cells in response to mechanostimulation.
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Affiliation(s)
- Priyasha Deshpande
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, NY
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, NY
| | - Emily Prentice
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Neuroscience Initiative, Advanced Science Research Center, CUNY, New York, NY
| | | | - Patrizia Casaccia
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, NY
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Neuroscience Initiative, Advanced Science Research Center, CUNY, New York, NY
| | - Shana Elbaum-Garfinkle
- Ph.D. Program in Biochemistry, Graduate Center of the City University of New York, NY
- Ph.D. Program in Biology, Graduate Center of the City University of New York, NY
- Structural Biology Initiative, Advanced Science Research Center, CUNY, New York, NY
- Ph.D. Program in Chemistry, Graduate Center of the City University of New York, NY
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7
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Dion C, Laberthonnière C, Magdinier F. [Epigenetics, principles and examples of applications]. Rev Med Interne 2023; 44:594-601. [PMID: 37438189 DOI: 10.1016/j.revmed.2023.06.011] [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: 01/21/2023] [Revised: 06/20/2023] [Accepted: 06/20/2023] [Indexed: 07/14/2023]
Abstract
Since the discovery of DNA as the support of genetic information, the challenge for generations of life scientists was to understand the mechanisms underlying the process that translate the sequence of a gene to a phenotype. In the 1950s, the concept of epigenetics was defined by the British biologist Conrad H. Waddington as the study of "epigenesis" that governs the biological processes involved in the development of any organism. The term epigenetics, now best defined as "above the DNA sequence" reflects the gene-environment interactions by which genes determine traits. Since, its first description, studies underlying the mechanisms involved in these processes has led to an increasing understanding of the regulation all genome transactions such as transcription, replication, repair and the biological pathways coordinated by these mechanisms. We will discuss here the main principles regulating epigenetic processes, their roles in physiology, their evolution over the life time and their implications in medicine.
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Affiliation(s)
- C Dion
- Aix Marseille Univ, INSERM, Marseille Medical Genetics, 13000 Marseille, France; MRC London Institute of Medical Sciences (LMS), London, United Kingdom; Institute of Clinical Sciences (ICS), Faculty of Medicine, Imperial College London, London, United Kingdom
| | - C Laberthonnière
- Aix Marseille Univ, INSERM, Marseille Medical Genetics, 13000 Marseille, France; Molecular Developmental Biology, Faculty of Science, Radboud University, Radboud Institute for Molecular Life Sciences, Nijmegen, The Netherlands
| | - F Magdinier
- Aix Marseille Univ, INSERM, Marseille Medical Genetics, 13000 Marseille, France.
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8
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Theophanous A, Christodoulou A, Mattheou C, Sibai DS, Moss T, Santama N. Transcription factor UBF depletion in mouse cells results in downregulation of both downstream and upstream elements of the rRNA transcription network. J Biol Chem 2023; 299:105203. [PMID: 37660911 PMCID: PMC10558777 DOI: 10.1016/j.jbc.2023.105203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 08/20/2023] [Accepted: 08/24/2023] [Indexed: 09/05/2023] Open
Abstract
Transcription/processing of the ribosomal RNA (rRNA) precursor, as part of ribosome biosynthesis, is intensively studied and characterized in eukaryotic cells. Here, we constructed shRNA-based mouse cell lines partially silenced for the Upstream Binding Factor UBF, the master regulator of rRNA transcription and organizer of open rDNA chromatin. Full Ubf silencing in vivo is not viable, and these new tools allow further characterization of rRNA transcription and its coordination with cellular signaling. shUBF cells display cell cycle G1 delay and reduced 47S rRNA precursor and 28S rRNA at baseline and serum-challenged conditions. Growth-related mTOR signaling is downregulated with the fractions of active phospho-S6 Kinase and pEIF4E translation initiation factor reduced, similar to phosphorylated cell cycle regulator retinoblastoma, pRB, positive regulator of UBF availability/rRNA transcription. Additionally, we find transcription-competent pUBF (Ser484) severely restricted and its interacting initiation factor RRN3 reduced and responsive to extracellular cues. Furthermore, fractional UBF occupancy on the rDNA unit is decreased in shUBF, and expression of major factors involved in different aspects of rRNA transcription is severely downregulated by UBF depletion. Finally, we observe reduced RNA Pol1 occupancy over rDNA promoter sequences and identified unexpected regulation of RNA Pol1 expression, relative to serum availability and under UBF silencing, suggesting that regulation of rRNA transcription may not be restricted to modulation of Pol1 promoter binding/elongation rate. Overall, this work reveals that UBF depletion has a critical downstream and upstream impact on the whole network orchestrating rRNA transcription in mammalian cells.
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Affiliation(s)
- Andria Theophanous
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus
| | | | | | - Dany S Sibai
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Quebec, Canada; Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, Canada
| | - Tom Moss
- Laboratory of Growth and Development, St-Patrick Research Group in Basic Oncology, Cancer Division of the Quebec University Hospital Research Centre, Quebec, Canada; Department of Molecular Biology, Medical Biochemistry and Pathology, Faculty of Medicine, Laval University, Quebec, Canada
| | - Niovi Santama
- Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus.
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9
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Scelfo A, Fachinetti D. Centromere: A Trojan horse for genome stability. DNA Repair (Amst) 2023; 130:103569. [PMID: 37708591 DOI: 10.1016/j.dnarep.2023.103569] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 08/22/2023] [Accepted: 09/05/2023] [Indexed: 09/16/2023]
Abstract
Centromeres play a key role in the maintenance of genome stability to prevent carcinogenesis and diseases. They are specialized chromosome loci essential to ensure faithful transmission of genomic information across cell generations by mediating the interaction with spindle microtubules. Nonetheless, while fulfilling these essential roles, their distinct repetitive composition and susceptibility to mechanical stresses during cell division render them susceptible to breakage events. In this review, we delve into the present understanding of the underlying causes of centromere fragility, from the mechanisms governing its DNA replication and repair, to the pathways acting to counteract potential challenges. We propose that the centromere represents a "Trojan horse" exerting vital functions that, at the same time, potentially threatens whole genome stability.
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Affiliation(s)
- Andrea Scelfo
- Institut Curie, CNRS, UMR 144, Sorbonne University, 26 rue d'Ulm, 75005 Paris, France.
| | - Daniele Fachinetti
- Institut Curie, CNRS, UMR 144, Sorbonne University, 26 rue d'Ulm, 75005 Paris, France.
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10
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Duhamel M, Hood ME, Rodríguez de la Vega RC, Giraud T. Dynamics of transposable element accumulation in the non-recombining regions of mating-type chromosomes in anther-smut fungi. Nat Commun 2023; 14:5692. [PMID: 37709766 PMCID: PMC10502011 DOI: 10.1038/s41467-023-41413-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 08/30/2023] [Indexed: 09/16/2023] Open
Abstract
In the absence of recombination, the number of transposable elements (TEs) increases due to less efficient selection, but the dynamics of such TE accumulations are not well characterized. Leveraging a dataset of 21 independent events of recombination cessation of different ages in mating-type chromosomes of Microbotryum fungi, we show that TEs rapidly accumulated in regions lacking recombination, but that TE content reached a plateau at ca. 50% of occupied base pairs by 1.5 million years following recombination suppression. The same TE superfamilies have expanded in independently evolved non-recombining regions, in particular rolling-circle replication elements (Helitrons). Long-terminal repeat (LTR) retrotransposons of the Copia and Ty3 superfamilies also expanded, through transposition bursts (distinguished from gene conversion based on LTR divergence), with both non-recombining regions and autosomes affected, suggesting that non-recombining regions constitute TE reservoirs. This study improves our knowledge of genome evolution by showing that TEs can accumulate through bursts, following non-linear decelerating dynamics.
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Affiliation(s)
- Marine Duhamel
- Ecologie Systématique Evolution, IDEEV, CNRS, Université Paris-Saclay, AgroParisTech, Bâtiment 680, 12 route RD128, 91190, Gif-sur-Yvette, France.
- Evolution der Pflanzen und Pilze, Ruhr-Universität Bochum, Universitätsstraße 150, 44780, Bochum, Germany.
| | - Michael E Hood
- Department of Biology, Amherst College, 01002-5000, Amherst, MA, USA
| | - Ricardo C Rodríguez de la Vega
- Ecologie Systématique Evolution, IDEEV, CNRS, Université Paris-Saclay, AgroParisTech, Bâtiment 680, 12 route RD128, 91190, Gif-sur-Yvette, France
| | - Tatiana Giraud
- Ecologie Systématique Evolution, IDEEV, CNRS, Université Paris-Saclay, AgroParisTech, Bâtiment 680, 12 route RD128, 91190, Gif-sur-Yvette, France
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11
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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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12
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Chen B, Ge T, Jian M, Chen L, Fang Z, He Z, Huang C, An Y, Yin S, Xiong Y, Zhang J, Li R, Ye M, Li Y, Liu F, Ma W, Songyang Z. Transmembrane nuclease NUMEN/ENDOD1 regulates DNA repair pathway choice at the nuclear periphery. Nat Cell Biol 2023:10.1038/s41556-023-01165-1. [PMID: 37322289 DOI: 10.1038/s41556-023-01165-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 05/10/2023] [Indexed: 06/17/2023]
Abstract
Proper repair of DNA damage lesions is essential to maintaining genome integrity and preventing the development of human diseases, including cancer. Increasing evidence suggests the importance of the nuclear envelope in the spatial regulation of DNA repair, although the mechanisms of such regulatory processes remain poorly defined. Through a genome-wide synthetic viability screen for PARP-inhibitor resistance using an inducible CRISPR-Cas9 platform and BRCA1-deficient breast cancer cells, we identified a transmembrane nuclease (renamed NUMEN) that could facilitate compartmentalized and non-homologous end joining-dependent repair of double-stranded DNA breaks at the nuclear periphery. Collectively, our data demonstrate that NUMEN generates short 5' overhangs through its endonuclease and 3'→5' exonuclease activities, promotes the repair of DNA lesions-including heterochromatic lamina-associated domain breaks as well as deprotected telomeres-and functions as a downstream effector of DNA-dependent protein kinase catalytic subunit. These findings underline the role of NUMEN as a key player in DNA repair pathway choice and genome-stability maintenance, and have implications for ongoing research into the development and treatment of genome instability disorders.
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Affiliation(s)
- Bohong Chen
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Tianyu Ge
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Meiqi Jian
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Liutao Chen
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Zhengwen Fang
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Zibin He
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Chengjing Huang
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yan An
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Shanshan Yin
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yuanyuan Xiong
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - JingKai Zhang
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Ruofei Li
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Miaoman Ye
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Yubing Li
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Feng Liu
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Wenbing Ma
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Zhou Songyang
- MOE Key Laboratory of Gene Function and Regulation and Guangzhou Key Laboratory of Healthy Aging Research, School of Life Sciences, Sun Yat-sen University, Guangzhou, China.
- Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.
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13
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Qiang Y, He X, Li Z, Li S, Zhang J, Liu T, Tursunniyaz M, Wang X, Liu Z, Fang L. Genome-wide identification and expression analysis of the response regulator gene family in alfalfa ( Medicago sativa L.) reveals their multifarious roles in stress response. FRONTIERS IN PLANT SCIENCE 2023; 14:1149880. [PMID: 36998691 PMCID: PMC10043395 DOI: 10.3389/fpls.2023.1149880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 02/23/2023] [Indexed: 06/19/2023]
Abstract
As important components of the two-component regulatory system, response regulatory proteins (RRPs) play a crucial role in histidine phosphorylation-mediated signal transduction in response to environmental fluctuations. Accumulating evidence has revealed that RRPs play important roles in plant growth and stress response. However, the specific functions of RR genes (RRs) in cultivated alfalfa remain ambiguous. Therefore, in this study, we identified and characterized the RR family genes in the alfalfa genome using bioinformatics methods. Our analysis revealed 37 RRs in the alfalfa genome of Zhongmu No.1 that were unevenly distributed on the chromosomes. Cis-elements analysis revealed the involvement of RRs in responses to light, stress, and various plant hormones. Expression analysis of RRs in different tissues revealed their distinct tissue expression patterns. These findings provide preliminary insights into the roles of RRs in plant responses to abiotic stress, which can be used to improve the stress tolerance of autotetraploid-cultivated alfalfa plants via genetic engineering.
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Affiliation(s)
- Yuqin Qiang
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Xiaojuan He
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Zhen Li
- National Engineering Laboratory for Volatile Organic Compounds Pollution Control Material & Technology, University of Chinese Academy of Sciences, Beijing, China
| | - Siqi Li
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Jia Zhang
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Tao Liu
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Mamateliy Tursunniyaz
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Xinyu Wang
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Zhipeng Liu
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
| | - Longfa Fang
- State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, China
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14
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Ni C, Buszczak M. The homeostatic regulation of ribosome biogenesis. Semin Cell Dev Biol 2023; 136:13-26. [PMID: 35440410 PMCID: PMC9569395 DOI: 10.1016/j.semcdb.2022.03.043] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 03/30/2022] [Accepted: 03/31/2022] [Indexed: 12/22/2022]
Abstract
The continued integrity of biological systems depends on a balance between interdependent elements at the molecular, cellular, and organismal levels. This is particularly true for the generation of ribosomes, which influence almost every aspect of cell and organismal biology. Ribosome biogenesis (RiBi) is an energetically demanding process that involves all three RNA polymerases, numerous RNA processing factors, chaperones, and the coordinated expression of 79-80 ribosomal proteins (r-proteins). Work over the last several decades has revealed that the dynamic regulation of ribosome production represents a major mechanism by which cells maintain homeostasis in response to changing environmental conditions and acute stress. More recent studies suggest that cells and tissues within multicellular organisms exhibit dramatically different levels of ribosome production and protein synthesis, marked by the differential expression of RiBi factors. Thus, distinct bottlenecks in the RiBi process, downstream of rRNA transcription, may exist within different cell populations of multicellular organisms during development and in adulthood. This review will focus on our current understanding of the mechanisms that link the complex molecular process of ribosome biogenesis with cellular and organismal physiology. We will discuss diverse topics including how different steps in the RiBi process are coordinated with one another, how MYC and mTOR impact RiBi, and how RiBi levels change between stem cells and their differentiated progeny. In turn, we will also review how regulated changes in ribosome production itself can feedback to influence cell fate and function.
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Affiliation(s)
- Chunyang Ni
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA
| | - Michael Buszczak
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9148, USA.
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15
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Huang M, Hong M, Hou X, Zhu C, Chen D, Chen X, Guang S, Feng X. H3K9me1/2 methylation limits the lifespan of daf-2 mutants in C. elegans. eLife 2022; 11:74812. [PMID: 36125117 PMCID: PMC9514849 DOI: 10.7554/elife.74812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 09/16/2022] [Indexed: 11/29/2022] Open
Abstract
Histone methylation plays crucial roles in the development, gene regulation, and maintenance of stem cell pluripotency in mammals. Recent work shows that histone methylation is associated with aging, yet the underlying mechanism remains unclear. In this work, we identified a class of putative histone 3 lysine 9 mono/dimethyltransferase genes (met-2, set-6, set-19, set-20, set-21, set-32, and set-33), mutations in which induce synergistic lifespan extension in the long-lived DAF-2 (insulin growth factor 1 [IGF-1] receptor) mutant in Caenorhabditis elegans. These putative histone methyltransferase plus daf-2 double mutants not only exhibited an average lifespan nearly three times that of wild-type animals and a maximal lifespan of approximately 100 days, but also significantly increased resistance to oxidative and heat stress. Synergistic lifespan extension depends on the transcription factor DAF-16 (FOXO). mRNA-seq experiments revealed that the mRNA levels of DAF-16 Class I genes, which are activated by DAF-16, were further elevated in the daf-2;set double mutants. Among these genes, tts-1, F35E8.7, ins-35, nhr-62, sod-3, asm-2, and Y39G8B.7 are required for the lifespan extension of the daf-2;set-21 double mutant. In addition, treating daf-2 animals with the H3K9me1/2 methyltransferase G9a inhibitor also extends lifespan and increases stress resistance. Therefore, investigation of DAF-2 and H3K9me1/2 deficiency-mediated synergistic longevity will contribute to a better understanding of the molecular mechanisms of aging and therapeutic applications.
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Affiliation(s)
- Meng Huang
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
| | - Minjie Hong
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
| | - Xinhao Hou
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
| | - Chengming Zhu
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
| | - Di Chen
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
| | - Xiangyang Chen
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
| | - Shouhong Guang
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
| | - Xuezhu Feng
- Department of Obstetrics and Gynecology, University of Science and Technology of China, Hefei, China
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16
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Liquid-liquid phase separation in tumor biology. Signal Transduct Target Ther 2022; 7:221. [PMID: 35803926 PMCID: PMC9270353 DOI: 10.1038/s41392-022-01076-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 06/16/2022] [Accepted: 06/21/2022] [Indexed: 12/12/2022] Open
Abstract
Liquid–liquid phase separation (LLPS) is a novel principle for explaining the precise spatial and temporal regulation in living cells. LLPS compartmentalizes proteins and nucleic acids into micron-scale, liquid-like, membraneless bodies with specific functions, which were recently termed biomolecular condensates. Biomolecular condensates are executors underlying the intracellular spatiotemporal coordination of various biological activities, including chromatin organization, genomic stability, DNA damage response and repair, transcription, and signal transduction. Dysregulation of these cellular processes is a key event in the initiation and/or evolution of cancer, and emerging evidence has linked the formation and regulation of LLPS to malignant transformations in tumor biology. In this review, we comprehensively summarize the detailed mechanisms of biomolecular condensate formation and biophysical function and review the recent major advances toward elucidating the multiple mechanisms involved in cancer cell pathology driven by aberrant LLPS. In addition, we discuss the therapeutic perspectives of LLPS in cancer research and the most recently developed drug candidates targeting LLPS modulation that can be used to combat tumorigenesis.
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17
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Liu Q, Liu P, Ji T, Zheng L, Shen C, Ran S, Liu J, Zhao Y, Niu Y, Wang T, Dong J. The histone methyltransferase SUVR2 promotes DSB repair via chromatin remodeling and liquid-liquid phase separation. MOLECULAR PLANT 2022; 15:1157-1175. [PMID: 35610973 DOI: 10.1016/j.molp.2022.05.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 05/15/2022] [Accepted: 05/18/2022] [Indexed: 06/15/2023]
Abstract
Maintaining genomic integrity and stability is particularly important for stem cells, which are at the top of the cell lineage origin. Here, we discovered that the plant-specific histone methyltransferase SUVR2 maintains the genome integrity of the root tip stem cells through chromatin remodeling and liquid-liquid phase separation (LLPS) when facing DNA double-strand breaks (DSBs). The histone methyltransferase SUVR2 (MtSUVR2) has histone methyltransferase activity and catalyzes the conversion of histone H3 lysine 9 monomethylation (H3K9me1) to H3K9me2/3 in vitro and in Medicago truncatula. Under DNA damage, the proportion of heterochromatin decreased and the level of DSB damage marker γ-H2AX increased in suvr2 mutants, indicating that MtSUVR2 promotes the compaction of the chromatin structure through H3K9 methylation modification to protect DNA from damage. Interestingly, MtSUVR2 was induced by DSBs to phase separate and form droplets to localize at the damage sites, and this was confirmed by immunofluorescence and fluorescence recovery after photobleaching experiments. The IDR1 and low-complexity domain regions of MtSUVR2 determined its phase separation in the nucleus, whereas the IDR2 region determined the interaction with the homologous recombinase MtRAD51. Furthermore, we found that MtSUVR2 drove the phase separation of MtRAD51 to form "DNA repair bodies," which could enhance the stability of MtRAD51 proteins to facilitate error-free homologous recombination repair of stem cells. Taken together, our study reveals that chromatin remodeling-associated proteins participate in DNA repair through LLPS.
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Affiliation(s)
- Qianwen Liu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Peng Liu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Tuo Ji
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Lihua Zheng
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Chen Shen
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shasha Ran
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jinling Liu
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yafei Zhao
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yiding Niu
- Key Laboratory of Forage and Endemic Crop Biology, Ministry of Education, School of Life Sciences, Inner Mongolia University, Hohhot, China
| | - Tao Wang
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
| | - Jiangli Dong
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
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18
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Population Scale Analysis of Centromeric Satellite DNA Reveals Highly Dynamic Evolutionary Patterns and Genomic Organization in Long-Tailed and Rhesus Macaques. Cells 2022; 11:cells11121953. [PMID: 35741082 PMCID: PMC9221937 DOI: 10.3390/cells11121953] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 06/12/2022] [Accepted: 06/14/2022] [Indexed: 02/04/2023] Open
Abstract
Centromeric satellite DNA (cen-satDNA) consists of highly divergent repeat monomers, each approximately 171 base pairs in length. Here, we investigated the genetic diversity in the centromeric region of two primate species: long-tailed (Macaca fascicularis) and rhesus (Macaca mulatta) macaques. Fluorescence in situ hybridization and bioinformatic analysis showed the chromosome-specific organization and dynamic nature of cen-satDNAsequences, and their substantial diversity, with distinct subfamilies across macaque populations, suggesting increased turnovers. Comparative genomics identified high level polymorphisms spanning a 120 bp deletion region and a remarkable interspecific variability in cen-satDNA size and structure. Population structure analysis detected admixture patterns within populations, indicating their high divergence and rapid evolution. However, differences in cen-satDNA profiles appear to not be involved in hybrid incompatibility between the two species. Our study provides a genomic landscape of centromeric repeats in wild macaques and opens new avenues for exploring their impact on the adaptive evolution and speciation of primates.
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19
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Boldyreva LV, Andreyeva EN, Pindyurin AV. Position Effect Variegation: Role of the Local Chromatin Context in Gene Expression Regulation. Mol Biol 2022. [DOI: 10.1134/s0026893322030049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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20
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Wang Y, Li Y, Zai W, Hu K, Zhu Y, Deng Q, Wu M, Li Y, Chen J, Yuan Z. HBV covalently closed circular DNA minichromosomes in distinct epigenetic transcriptional states differ in their vulnerability to damage. Hepatology 2022; 75:1275-1288. [PMID: 34779008 DOI: 10.1002/hep.32245] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 10/20/2021] [Accepted: 11/10/2021] [Indexed: 12/19/2022]
Abstract
BACKGROUND AND AIMS HBV covalently closed circular DNA (cccDNA) is a major obstacle for a cure of chronic hepatitis B. Accumulating evidence suggests that epigenetic modifications regulate the transcriptional activity of cccDNA minichromosomes. However, it remains unclear how the epigenetic state of cccDNA affects its stability. APPROACHES AND RESULTS By using HBV infection cell models and in vitro and in vivo recombinant cccDNA (rcccDNA) and HBVcircle models, the reduction rate of HBV cccDNA and the efficacy of apolipoprotein B mRNA editing enzyme catalytic subunit 3A (APOBEC3A)-mediated and CRISPR/CRISPR-associated 9 (Cas9)-mediated cccDNA targeting were compared between cccDNAs with distinct transcriptional activities. Interferon-α treatment and hepatitis B x protein (HBx) deletion were applied as two strategies for cccDNA repression. Chromatin immunoprecipitation and micrococcal nuclease assays were performed to determine the epigenetic pattern of cccDNA. HBV cccDNA levels remained stable in nondividing hepatocytes; however, they were significantly reduced during cell division, and the reduction rate was similar between cccDNAs in transcriptionally active and transcriptionally repressed states. Strikingly, HBV rcccDNA without HBx expression exhibited a significantly longer persistence in mice. The cccDNA with low transcriptional activity exhibited an epigenetically inactive pattern and was more difficult to access by APOBEC3A and engineered CRISPR-Cas9. The epigenetic regulator activating cccDNA increased its vulnerability to APOBEC3A. CONCLUSIONS HBV cccDNA minichromosomes in distinct epigenetic transcriptional states showed a similar reduction rate during cell division but significantly differed in their accessibility and vulnerability to targeted nucleases and antiviral agents. Epigenetic sensitization of cccDNA makes it more susceptible to damage and may potentially contribute to an HBV cure.
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Affiliation(s)
- Yang Wang
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina
| | - Yumeng Li
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina
| | - Wenjing Zai
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina
| | - Kongying Hu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina
| | - Yuanfei Zhu
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina
| | - Qiang Deng
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina.,Research Unit of Cure of Chronic Hepatitis B Virus InfectionChinese Academy of Medical SciencesShanghaiChina.,Shanghai Frontiers Science Center of Pathogenic Microbes and InfectionShanghaiChina
| | - Min Wu
- Shanghai Public Health Clinical CenterFudan UniversityShanghaiChina
| | - Yaming Li
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina
| | - Jieliang Chen
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina.,Research Unit of Cure of Chronic Hepatitis B Virus InfectionChinese Academy of Medical SciencesShanghaiChina.,Shanghai Frontiers Science Center of Pathogenic Microbes and InfectionShanghaiChina
| | - Zhenghong Yuan
- Key Laboratory of Medical Molecular Virology (MOE/NHC/CAMS)School of Basic Medical SciencesShanghai Medical CollegeFudan UniversityShanghaiChina.,Research Unit of Cure of Chronic Hepatitis B Virus InfectionChinese Academy of Medical SciencesShanghaiChina.,Shanghai Frontiers Science Center of Pathogenic Microbes and InfectionShanghaiChina
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21
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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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22
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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: 42] [Impact Index Per Article: 21.0] [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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23
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Spangenberg V, Losev M, Volkhin I, Smirnova S, Nikitin P, Kolomiets O. DNA Environment of Centromeres and Non-Homologous Chromosomes Interactions in Mouse. Cells 2021; 10:3375. [PMID: 34943883 PMCID: PMC8699862 DOI: 10.3390/cells10123375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 11/16/2022] Open
Abstract
Although the pericentromeric regions of chromosomes that are enriched in tandemly repeated satellite DNA represent a significant part of eukaryotic genomes, they remain understudied, which is mainly due to interdisciplinary knowledge gaps. Recent studies suggest their important role in genome regulation, karyotype stability, and evolution. Thus, the idea of satellite DNA as a junk part of the genome has been refuted. The integration of data regarding molecular composition, chromosome behaviour, and the details of the in situ organization of pericentromeric regions is of great interest. The objective of this work was a cytogenetic analysis of the interactions between pericentromeric regions from non-homologous chromosomes in mouse spermatocytes using immuno-FISH. We analysed two events: the associations between centromeric regions of the X chromosome and autosomes and the associations between the centromeric regions of the autosomal bivalents that form chromocenters. We concluded that the X chromosome forms temporary synaptic associations with different autosomes in early meiotic prophase I, which can normally be found until the pachytene-diplotene, without signs of pachytene arrest. These associations are formed between the satellite-DNA-rich centromeric regions of the X chromosome and different autosomes but do not involve the satellite-DNA-poor centromeric region of the Y chromosome. We suggest the hypothetical model of X chromosome competitive replacement from such associations during synaptic correction. We showed that the centromeric region of the X chromosome in association remains free of γH2Ax-dependent chromatin inactivation, while the Y chromosome is completely inactivated. This finding highlights the predominant role of associations between satellite DNA-rich regions of different chromosomes, including the X chromosome. We suppose that X-autosomal transient associations are a manifestation of an additional synaptic disorder checkpoint. These associations are normally corrected before the late diplotene stage. We revealed that the intense spreading conditions that were applied to the spermatocyte I nuclei did not lead to the destruction of stretched chromatin fibers of elongated chromocenters enriched in satellite DNA. The tight associations that we revealed between the pericentromeric regions of different autosomal bivalents and the X chromosome may represent the basis for a mechanism for maintaining the repeats stability in the autosomes and in the X chromosome. The consequences of our findings are discussed.
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Affiliation(s)
- Victor Spangenberg
- Vavilov Institute of General Genetics, Russian Academy of Sciences, 119991 Moscow, Russia; (M.L.); (I.V.); (S.S.); (P.N.); (O.K.)
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Reyes Lerma AC, Šťáhlavský F, Seiter M, Carabajal Paladino LZ, Divišová K, Forman M, Sember A, Král J. Insights into the Karyotype Evolution of Charinidae, the Early-Diverging Clade of Whip Spiders (Arachnida: Amblypygi). Animals (Basel) 2021; 11:3233. [PMID: 34827965 PMCID: PMC8614469 DOI: 10.3390/ani11113233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/05/2021] [Accepted: 11/09/2021] [Indexed: 11/16/2022] Open
Abstract
Whip spiders (Amblypygi) represent an ancient order of tetrapulmonate arachnids with a low diversity. Their cytogenetic data are confined to only a few reports. Here, we analyzed the family Charinidae, a lineage almost at the base of the amblypygids, providing an insight into the ancestral traits and basic trajectories of amblypygid karyotype evolution. We performed Giemsa staining, selected banding techniques, and detected 18S ribosomal DNA and telomeric repeats by fluorescence in situ hybridization in four Charinus and five Sarax species. Both genera exhibit a wide range of diploid chromosome numbers (2n = 42-76 and 22-74 for Charinus and Sarax, respectively). The 2n reduction was accompanied by an increase of proportion of biarmed elements. We further revealed a single NOR site (probably an ancestral condition for charinids), the presence of a (TTAGG)n telomeric motif localized mostly at the chromosome ends, and an absence of heteromorphic sex chromosomes. Our data collectively suggest a high pace of karyotype repatterning in amblypygids, with probably a high ancestral 2n and its subsequent gradual reduction by fusions, and the action of pericentric inversions, similarly to what has been proposed for neoamblypygids. The possible contribution of fissions to charinid karyotype repatterning, however, cannot be fully ruled out.
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Affiliation(s)
- Azucena Claudia Reyes Lerma
- Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague, Czech Republic; (A.C.R.L.); (K.D.); (M.F.); (J.K.)
| | - František Šťáhlavský
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, 128 44 Prague, Czech Republic;
| | - Michael Seiter
- Unit Integrative Zoology, Department of Evolutionary Biology, University of Vienna, Djerassiplatz 1, 1030 Vienna, Austria;
- Natural History Museum Vienna, 3. Zoology (Invertebrates), Burgring 7, 1010 Vienna, Austria
| | - Leonela Zusel Carabajal Paladino
- Biology Centre of the Czech Academy of Sciences, Institute of Entomology, Branišovská 31, 370 05 České Budějovice, Czech Republic;
- Arthropod Genetics Group, The Pirbright Institute, Ash Road, Pirbright, Woking GU24 0NF, UK
| | - Klára Divišová
- Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague, Czech Republic; (A.C.R.L.); (K.D.); (M.F.); (J.K.)
| | - Martin Forman
- Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague, Czech Republic; (A.C.R.L.); (K.D.); (M.F.); (J.K.)
| | - Alexandr Sember
- Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague, Czech Republic; (A.C.R.L.); (K.D.); (M.F.); (J.K.)
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Rumburská 89, 277 21 Liběchov, Czech Republic
| | - Jiří Král
- Laboratory of Arachnid Cytogenetics, Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 44 Prague, Czech Republic; (A.C.R.L.); (K.D.); (M.F.); (J.K.)
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Li J, Gao J, Wang R. Control of Chromatin Organization and Chromosome Behavior during the Cell Cycle through Phase Separation. Int J Mol Sci 2021; 22:ijms222212271. [PMID: 34830152 PMCID: PMC8621359 DOI: 10.3390/ijms222212271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 10/29/2021] [Accepted: 11/09/2021] [Indexed: 01/02/2023] Open
Abstract
Phase-separated condensates participate in various biological activities. Liquid-liquid phase separation (LLPS) can be driven by collective interactions between multivalent and intrinsically disordered proteins. The manner in which chromatin-with various morphologies and activities-is organized in a complex and small nucleus still remains to be fully determined. Recent findings support the claim that phase separation is involved in the regulation of chromatin organization and chromosome behavior. Moreover, phase separation also influences key events during mitosis and meiosis. This review elaborately dissects how phase separation regulates chromatin and chromosome organization and controls mitotic and meiotic chromosome behavior.
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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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Du J, Ge C, Li T, Wang S, Gao Z, Sassa H, Qiao Y. Molecular characteristics of S-RNase alleles as the determinant of self-incompatibility in the style of Fragaria viridis. HORTICULTURE RESEARCH 2021; 8:185. [PMID: 34333550 PMCID: PMC8325692 DOI: 10.1038/s41438-021-00623-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 05/29/2021] [Accepted: 06/01/2021] [Indexed: 05/11/2023]
Abstract
Strawberry (Fragaria spp.) is a member of the Rosoideae subfamily in the family Rosaceae. The self-incompatibility (SI) of some diploid species is a key agronomic trait that acts as a basic pollination barrier; however, the genetic mechanism underlying SI control in strawberry remains unclear. Two candidate S-RNases (Sa- and Sb-RNase) identified in the transcriptome of the styles of the self-incompatible Fragaria viridis 42 were confirmed to be SI determinants at the S locus following genotype identification and intraspecific hybridization using selfing progenies. Whole-genome collinearity and RNase T2 family analysis revealed that only an S locus exists in Fragaria; however, none of the compatible species contained S-RNase. Although the results of interspecific hybridization experiments showed that F. viridis (SI) styles could accept pollen from F. mandshurica (self-compatible), the reciprocal cross was incompatible. Sa and Sb-RNase contain large introns, and their noncoding sequences (promotors and introns) can be transcribed into long noncoding RNAs (lncRNAs). Overall, the genus Fragaria exhibits S-RNase-based gametophytic SI, and S-RNase loss occurs at the S locus of compatible germplasms. In addition, a type of SI-independent unilateral incompatibility exists between compatible and incompatible Fragaria species. Furthermore, the large introns and neighboring lncRNAs in S-RNase in Fragaria could offer clues about S-RNase expression strategies.
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Affiliation(s)
- Jianke Du
- Laboratory of Fruit Crop Biotechnology, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
- Laboratory of Genetics and Plant Breeding, Graduate School of Horticulture, Chiba University, Matsudo, 271-8510, Chiba, Japan
| | - Chunfeng Ge
- Laboratory of Fruit Crop Biotechnology, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, Jiangsu, China
| | - Tingting Li
- Laboratory of Fruit Crop Biotechnology, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Sanhong Wang
- Laboratory of Fruit Crop Biotechnology, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Zhihong Gao
- Laboratory of Fruit Crop Biotechnology, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China
| | - Hidenori Sassa
- Laboratory of Genetics and Plant Breeding, Graduate School of Horticulture, Chiba University, Matsudo, 271-8510, Chiba, Japan
| | - Yushan Qiao
- Laboratory of Fruit Crop Biotechnology, College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China.
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Wei KHC, Chan C, Bachtrog D. Establishment of H3K9me3-dependent heterochromatin during embryogenesis in Drosophila miranda. eLife 2021; 10:55612. [PMID: 34128466 PMCID: PMC8285105 DOI: 10.7554/elife.55612] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Accepted: 06/14/2021] [Indexed: 12/27/2022] Open
Abstract
Heterochromatin is a key architectural feature of eukaryotic genomes crucial for silencing of repetitive elements. During Drosophila embryonic cellularization, heterochromatin rapidly appears over repetitive sequences, but the molecular details of how heterochromatin is established are poorly understood. Here, we map the genome-wide distribution of H3K9me3-dependent heterochromatin in individual embryos of Drosophila miranda at precisely staged developmental time points. We find that canonical H3K9me3 enrichment is established prior to cellularization and matures into stable and broad heterochromatin domains through development. Intriguingly, initial nucleation sites of H3K9me3 enrichment appear as early as embryonic stage 3 over transposable elements (TEs) and progressively broaden, consistent with spreading to neighboring nucleosomes. The earliest nucleation sites are limited to specific regions of a small number of recently active retrotransposon families and often appear over promoter and 5' regions of LTR retrotransposons, while late nucleation sites develop broadly across the entirety of most TEs. Interestingly, early nucleating TEs are strongly associated with abundant maternal piRNAs and show early zygotic transcription. These results support a model of piRNA-associated co-transcriptional silencing while also suggesting additional mechanisms for site-restricted H3K9me3 nucleation at TEs in pre-cellular Drosophila embryos.
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Affiliation(s)
- Kevin H-C Wei
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
| | - Carolus Chan
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
| | - Doris Bachtrog
- Department of Integrative Biology, University of California, Berkeley, Berkeley, United States
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Pappalardo XG, Barra V. Losing DNA methylation at repetitive elements and breaking bad. Epigenetics Chromatin 2021; 14:25. [PMID: 34082816 PMCID: PMC8173753 DOI: 10.1186/s13072-021-00400-z] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 05/21/2021] [Indexed: 02/08/2023] Open
Abstract
Background DNA methylation is an epigenetic chromatin mark that allows heterochromatin formation and gene silencing. It has a fundamental role in preserving genome stability (including chromosome stability) by controlling both gene expression and chromatin structure. Therefore, the onset of an incorrect pattern of DNA methylation is potentially dangerous for the cells. This is particularly important with respect to repetitive elements, which constitute the third of the human genome. Main body Repetitive sequences are involved in several cell processes, however, due to their intrinsic nature, they can be a source of genome instability. Thus, most repetitive elements are usually methylated to maintain a heterochromatic, repressed state. Notably, there is increasing evidence showing that repetitive elements (satellites, long interspersed nuclear elements (LINEs), Alus) are frequently hypomethylated in various of human pathologies, from cancer to psychiatric disorders. Repetitive sequences’ hypomethylation correlates with chromatin relaxation and unscheduled transcription. If these alterations are directly involved in human diseases aetiology and how, is still under investigation. Conclusions Hypomethylation of different families of repetitive sequences is recurrent in many different human diseases, suggesting that the methylation status of these elements can be involved in preservation of human health. This provides a promising point of view towards the research of therapeutic strategies focused on specifically tuning DNA methylation of DNA repeats.
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Affiliation(s)
- Xena Giada Pappalardo
- Department of Biomedical and Biotechnological Sciences (BIOMETEC), University of Catania, 95125, Catania, Italy.,National Council of Research, Institute for Biomedical Research and Innovation (IRIB), Unit of Catania, 95125, Catania, Italy
| | - Viviana Barra
- Department of Biological, Chemical and Pharmaceutical Sciences and Technologies (STEBICEF), University of Palermo, 90128, Palermo, Italy.
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Touati R, Tajouri A, Mesaoudi I, Oueslati AE, Lachiri Z, Kharrat M. New methodology for repetitive sequences identification in human X and Y chromosomes. Biomed Signal Process Control 2021; 64:102207. [PMID: 33101452 PMCID: PMC7572123 DOI: 10.1016/j.bspc.2020.102207] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 07/23/2020] [Accepted: 09/01/2020] [Indexed: 11/24/2022]
Abstract
Repetitive DNA sequences occupy the major proportion of DNA in the human genome and even in the other species' genomes. The importance of each repetitive DNA type depends on many factors: structural and functional roles, positions, lengths and numbers of these repetitions are clear examples. Conserving such DNA sequences or not in different locations in the chromosome remains a challenge for researchers in biology. Detecting their location despite their great variability and finding novel repetitive sequences remains a challenging task. To side-step this problem, we developed a new method based on signal and image processing tools. In fact, using this method we could find repetitive patterns in DNA images regardless of the repetition length. This new technique seems to be more efficient in detecting new repetitive sequences than bioinformatics tools. In fact, the classical tools present limited performances especially in case of mutations (insertion or deletion). However, modifying one or a few numbers of pixels in the image doesn't affect the global form of the repetitive pattern. As a consequence, we generated a new repetitive patterns database which contains tandem and dispersed repeated sequences. The highly repetitive sequences, we have identified in X and Y chromosomes, are shown to be located in other human chromosomes or in other genomes. The data we have generated is then taken as input to a Convolutional neural network classifier in order to classify them. The system we have constructed is efficient and gives an average of 94.4% as recognition score.
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Affiliation(s)
- Rabeb Touati
- University of Tunis El Manar, LR99ES10 Human Genetics Laboratory, Faculty of Medicine of Tunis (FMT), Tunisia
- University of Tunis El Manar, SITI Laboratory, National School of Engineers of Tunis, BP 37, Le Belvédère, 1002, Tunis, Tunisia
| | - Asma Tajouri
- University of Tunis El Manar, LR99ES10 Human Genetics Laboratory, Faculty of Medicine of Tunis (FMT), Tunisia
| | - Imen Mesaoudi
- University of Tunis El Manar, SITI Laboratory, National School of Engineers of Tunis, BP 37, Le Belvédère, 1002, Tunis, Tunisia
| | - Afef Elloumi Oueslati
- University of Tunis El Manar, SITI Laboratory, National School of Engineers of Tunis, BP 37, Le Belvédère, 1002, Tunis, Tunisia
| | - Zied Lachiri
- University of Tunis El Manar, SITI Laboratory, National School of Engineers of Tunis, BP 37, Le Belvédère, 1002, Tunis, Tunisia
| | - Maher Kharrat
- University of Tunis El Manar, LR99ES10 Human Genetics Laboratory, Faculty of Medicine of Tunis (FMT), Tunisia
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Gualtieri CT. Genomic Variation, Evolvability, and the Paradox of Mental Illness. Front Psychiatry 2021; 11:593233. [PMID: 33551865 PMCID: PMC7859268 DOI: 10.3389/fpsyt.2020.593233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 11/27/2020] [Indexed: 12/30/2022] Open
Abstract
Twentieth-century genetics was hard put to explain the irregular behavior of neuropsychiatric disorders. Autism and schizophrenia defy a principle of natural selection; they are highly heritable but associated with low reproductive success. Nevertheless, they persist. The genetic origins of such conditions are confounded by the problem of variable expression, that is, when a given genetic aberration can lead to any one of several distinct disorders. Also, autism and schizophrenia occur on a spectrum of severity, from mild and subclinical cases to the overt and disabling. Such irregularities reflect the problem of missing heritability; although hundreds of genes may be associated with autism or schizophrenia, together they account for only a small proportion of cases. Techniques for higher resolution, genomewide analysis have begun to illuminate the irregular and unpredictable behavior of the human genome. Thus, the origins of neuropsychiatric disorders in particular and complex disease in general have been illuminated. The human genome is characterized by a high degree of structural and behavioral variability: DNA content variation, epistasis, stochasticity in gene expression, and epigenetic changes. These elements have grown more complex as evolution scaled the phylogenetic tree. They are especially pertinent to brain development and function. Genomic variability is a window on the origins of complex disease, neuropsychiatric disorders, and neurodevelopmental disorders in particular. Genomic variability, as it happens, is also the fuel of evolvability. The genomic events that presided over the evolution of the primate and hominid lineages are over-represented in patients with autism and schizophrenia, as well as intellectual disability and epilepsy. That the special qualities of the human genome that drove evolution might, in some way, contribute to neuropsychiatric disorders is a matter of no little interest.
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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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Woodruff GC, Teterina AA. Degradation of the Repetitive Genomic Landscape in a Close Relative of Caenorhabditis elegans. Mol Biol Evol 2020; 37:2549-2567. [PMID: 32359146 PMCID: PMC7475029 DOI: 10.1093/molbev/msaa107] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The abundance, diversity, and genomic distribution of repetitive elements is highly variable among species. These patterns are thought to be driven in part by reproductive mode and the interaction of selection and recombination, and recombination rates typically vary by chromosomal position. In the nematode Caenorhabditis elegans, repetitive elements are enriched at chromosome arms and depleted on centers, and this mirrors the chromosomal distributions of other genomic features such as recombination rate. How conserved is this genomic landscape of repeats, and what evolutionary forces maintain it? To address this, we compared the genomic organization of repetitive elements across five Caenorhabditis species with chromosome-level assemblies. As previously reported, repeat content is enriched on chromosome arms in most Caenorhabditis species, and no obvious patterns of repeat content associated with reproductive mode were observed. However, the fig-associated C. inopinata has experienced repetitive element expansion and reveals no association of global repeat density with chromosome position. Patterns of repeat superfamily specific distributions reveal this global pattern is driven largely by a few repeat superfamilies that in C. inopinata have expanded in number and have weak associations with chromosome position. Additionally, 15% of predicted protein-coding genes in C. inopinata align to transposon-related proteins. When these are excluded, C. inopinata has no enrichment of genes in chromosome centers, in contrast to its close relatives who all have such clusters. Forward evolutionary simulations reveal that chromosomal heterogeneity in recombination rate alone can generate structured repetitive genomic landscapes when insertions are weakly deleterious, whereas chromosomal heterogeneity in the fitness effects of transposon insertion can promote such landscapes across a variety of evolutionary scenarios. Thus, patterns of gene density along chromosomes likely contribute to global repetitive landscapes in this group, although other historical or genomic factors are needed to explain the idiosyncrasy of genomic organization of various transposable element taxa within C. inopinata. Taken together, these results highlight the power of comparative genomics and evolutionary simulations in testing hypotheses regarding the causes of genome organization.
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Affiliation(s)
- Gavin C Woodruff
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR
| | - Anastasia A Teterina
- Institute of Ecology and Evolution, University of Oregon, Eugene, OR
- Center of Parasitology, Severtsov Institute of Ecology and Evolution RAS, Moscow, Russia
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Miga KH. Centromere studies in the era of 'telomere-to-telomere' genomics. Exp Cell Res 2020; 394:112127. [PMID: 32504677 DOI: 10.1016/j.yexcr.2020.112127] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 05/23/2020] [Accepted: 05/30/2020] [Indexed: 12/17/2022]
Abstract
We are entering into an exciting era of genomics where truly complete, high-quality assemblies of human chromosomes are available end-to-end, or from 'telomere-to-telomere' (T2T). This technological advance offers a new opportunity to include endogenous human centromeric regions in high-resolution, sequence-based studies. These emerging reference maps are expected to reveal a new functional landscape in the human genome, where centromere proteins, transcriptional regulation, and spatial organization can be examined with base-level resolution across different stages of development and disease. Such studies will depend on innovative assembly methods of extremely long tandem repeats (ETRs), or satellite DNAs, paired with the development of new, orthogonal validation methods to ensure accuracy and completeness. This review reflects the progress in centromere genomics, credited by recent advancements in long-read sequencing and assembly methods. In doing so, I will discuss the challenges that remain and the promise for a new period of scientific discovery for satellite DNA biology and centromere function.
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Affiliation(s)
- Karen H Miga
- UC Santa Cruz Genomics Institute, University of California, Santa Cruz, CA, CA, 95064, USA.
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35
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Epigenetic Factors That Control Pericentric Heterochromatin Organization in Mammals. Genes (Basel) 2020; 11:genes11060595. [PMID: 32481609 PMCID: PMC7349813 DOI: 10.3390/genes11060595] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/17/2020] [Accepted: 05/25/2020] [Indexed: 12/11/2022] Open
Abstract
Pericentric heterochromatin (PCH) is a particular form of constitutive heterochromatin that is localized to both sides of centromeres and that forms silent compartments enriched in repressive marks. These genomic regions contain species-specific repetitive satellite DNA that differs in terms of nucleotide sequences and repeat lengths. In spite of this sequence diversity, PCH is involved in many biological phenomena that are conserved among species, including centromere function, the preservation of genome integrity, the suppression of spurious recombination during meiosis, and the organization of genomic silent compartments in the nucleus. PCH organization and maintenance of its repressive state is tightly regulated by a plethora of factors, including enzymes (e.g., DNA methyltransferases, histone deacetylases, and histone methyltransferases), DNA and histone methylation binding factors (e.g., MECP2 and HP1), chromatin remodeling proteins (e.g., ATRX and DAXX), and non-coding RNAs. This evidence helps us to understand how PCH organization is crucial for genome integrity. It then follows that alterations to the molecular signature of PCH might contribute to the onset of many genetic pathologies and to cancer progression. Here, we describe the most recent updates on the molecular mechanisms known to underlie PCH organization and function.
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Li J, Wei S, Cao C, Chen K, He H, Gao G. Retrovectors packaged in CHO cells to generate GLP-1-Fc stable expression CHO cell lines. ELECTRON J BIOTECHN 2020; 41:56-59. [PMID: 32288149 PMCID: PMC7125944 DOI: 10.1016/j.ejbt.2019.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 07/26/2019] [Indexed: 11/18/2022] Open
Abstract
Background Chinese hamster ovary (CHO) cells are the most dependable mammalian cells for the production of recombinant proteins. Replication-incompetent retroviral vector (retrovector) is an efficient tool to generate stable cell lines. Multiple copies of integrated genes by retrovector transduction results in improved recombinant protein yield. HEK-293 and their genetic derivatives are principal cells for retrovector production. Retrovectors packaged in HEK-293 cells pose a risk of infectious agent transmission, such as viruses and mycoplasmas, from serum and packaging cells. Results In this report, retrovectors were packaged in CHO cells cultured in chemically defined (CD) media. The retrovectors were then used to transduce CHO cells. This method can block potential transmission of infectious agents from serum and packaging cells. With this method, we generated glucagon-like protein-1 Fc fusion protein (GLP-1-Fc) stable expression CHO cell lines. Productivity of GLP-1-Fc can reach 3.15 g/L. The GLP-1-Fc protein produced by this method has comparable bioactivity to that of dulaglutide (Trulicity). These stable cell lines retain 95–100% of productivity after 40 days of continuous culture (~ 48–56 generations). Conclusions Suspension CHO cells are clean, safe, and reliable cells for retrovector packaging. Retrovectors packaged from this system could be used to generate CHO stable cell lines for recombinant protein expression. How to cite: Li J, Wei S, Cao C, et al. Retrovectors packaged in CHO cells to generate GLP-1-Fc stable expression CHO cell lines. Electron J Biotechnol 2019;41. https://doi.org/10.1016/j.ejbt.2019.07.002.
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Affiliation(s)
- Jing Li
- Department of Biochemistry, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
- Zhuhai United Laboratories Co., Ltd., 2428 Anji Road, Zhuhai, Guangdong, China
- Corresponding author.
| | - Suzhen Wei
- Zhuhai United Laboratories Co., Ltd., 2428 Anji Road, Zhuhai, Guangdong, China
| | - Chunlai Cao
- Zhuhai United Laboratories Co., Ltd., 2428 Anji Road, Zhuhai, Guangdong, China
| | - Kangyue Chen
- Zhuhai United Laboratories Co., Ltd., 2428 Anji Road, Zhuhai, Guangdong, China
| | - Hua He
- Zhuhai United Laboratories Co., Ltd., 2428 Anji Road, Zhuhai, Guangdong, China
| | - Guoquan Gao
- Department of Biochemistry, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
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Gambogi CW, Dawicki-McKenna JM, Logsdon GA, Black BE. The unique kind of human artificial chromosome: Bypassing the requirement for repetitive centromere DNA. Exp Cell Res 2020; 391:111978. [PMID: 32246994 DOI: 10.1016/j.yexcr.2020.111978] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 03/23/2020] [Accepted: 03/25/2020] [Indexed: 12/20/2022]
Abstract
Centromeres are essential components of all eukaryotic chromosomes, including artificial/synthetic ones built in the laboratory. In humans, centromeres are typically located on repetitive α-satellite DNA, and these sequences are the "major ingredient" in first-generation human artificial chromosomes (HACs). Repetitive centromeric sequences present a major challenge for the design of synthetic mammalian chromosomes because they are difficult to synthesize, assemble, and characterize. Additionally, in most eukaryotes, centromeres are defined epigenetically. Here, we review the role of the genetic and epigenetic contributions to establishing centromere identity, highlighting recent work to hijack the epigenetic machinery to initiate centromere identity on a new generation of HACs built without α-satellite DNA. We also discuss the opportunities and challenges in developing useful unique sequence-based HACs.
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Affiliation(s)
- Craig W Gambogi
- Department of Biochemistry and Biophysics, Graduate Program in Biochemistry and Molecular Biophysics, Penn Center for Genome Integrity, and Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Jennine M Dawicki-McKenna
- Department of Biochemistry and Biophysics, Graduate Program in Biochemistry and Molecular Biophysics, Penn Center for Genome Integrity, and Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Glennis A Logsdon
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA, 98195, USA
| | - Ben E Black
- Department of Biochemistry and Biophysics, Graduate Program in Biochemistry and Molecular Biophysics, Penn Center for Genome Integrity, and Epigenetics Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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Puppo IL, Saifitdinova AF, Tonyan ZN. The Role of Satellite DNA in Causing Structural Rearrangements in Human Karyotype. RUSS J GENET+ 2020. [DOI: 10.1134/s1022795419080155] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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39
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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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40
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Buscaino A. Chromatin-Mediated Regulation of Genome Plasticity in Human Fungal Pathogens. Genes (Basel) 2019; 10:E855. [PMID: 31661931 PMCID: PMC6896017 DOI: 10.3390/genes10110855] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/18/2019] [Accepted: 10/25/2019] [Indexed: 12/20/2022] Open
Abstract
Human fungal pathogens, such as Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans, are a public health problem, causing millions of infections and killing almost half a million people annually. The ability of these pathogens to colonise almost every organ in the human body and cause life-threating infections relies on their capacity to adapt and thrive in diverse hostile host-niche environments. Stress-induced genome instability is a key adaptive strategy used by human fungal pathogens as it increases genetic diversity, thereby allowing selection of genotype(s) better adapted to a new environment. Heterochromatin represses gene expression and deleterious recombination and could play a key role in modulating genome stability in response to environmental changes. However, very little is known about heterochromatin structure and function in human fungal pathogens. In this review, I use our knowledge of heterochromatin structure and function in fungal model systems as a road map to review the role of heterochromatin in regulating genome plasticity in the most common human fungal pathogens: Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans.
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Affiliation(s)
- Alessia Buscaino
- University of Kent, School of Biosciences, Kent Fungal Group, Canterbury Kent CT2 7NJ, UK.
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41
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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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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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Langley SA, Miga KH, Karpen GH, Langley CH. Haplotypes spanning centromeric regions reveal persistence of large blocks of archaic DNA. eLife 2019; 8:e42989. [PMID: 31237235 PMCID: PMC6592686 DOI: 10.7554/elife.42989] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 05/20/2019] [Indexed: 12/22/2022] Open
Abstract
Despite critical roles in chromosome segregation and disease, the repetitive structure and vast size of centromeres and their surrounding heterochromatic regions impede studies of genomic variation. Here we report the identification of large-scale haplotypes (cenhaps) in humans that span the centromere-proximal regions of all metacentric chromosomes, including the arrays of highly repeated α-satellites on which centromeres form. Cenhaps reveal deep diversity, including entire introgressed Neanderthal centromeres and equally ancient lineages among Africans. These centromere-spanning haplotypes contain variants, including large differences in α-satellite DNA content, which may influence the fidelity and bias of chromosome transmission. The discovery of cenhaps creates new opportunities to investigate their contribution to phenotypic variation, especially in meiosis and mitosis, as well as to more incisively model the unexpectedly rich evolution of these challenging genomic regions.
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Affiliation(s)
- Sasha A Langley
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
- Biological Systems and Engineering DivisionLawrence Berkeley National LaboratoryBerkeleyUnited States
| | - Karen H Miga
- UC Santa Cruz Genomics InstituteUniversity of California, Santa CruzSanta CruzUnited States
| | - Gary H Karpen
- Department of Molecular and Cell BiologyUniversity of California, BerkeleyBerkeleyUnited States
- Biological Systems and Engineering DivisionLawrence Berkeley National LaboratoryBerkeleyUnited States
| | - Charles H Langley
- Department of Evolution and EcologyUniversity of California, DavisDavisUnited States
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Pellestor F. Chromoanagenesis: cataclysms behind complex chromosomal rearrangements. Mol Cytogenet 2019; 12:6. [PMID: 30805029 PMCID: PMC6371609 DOI: 10.1186/s13039-019-0415-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 01/17/2019] [Indexed: 12/21/2022] Open
Abstract
Background During the last decade, genome sequencing projects in cancer genomes as well as in patients with congenital diseases and healthy individuals have led to the identification of new types of massive chromosomal rearrangements arising during single chaotic cellular events. These unanticipated catastrophic phenomenon are termed chromothripsis, chromoanasynthesis and chromoplexis., and are grouped under the name of “chromoanagenesis”. Results For each process, several specific features have been described, allowing each phenomenon to be distinguished from each other and to understand its mechanism of formation and to better understand its aetiology. Thus, chromothripsis derives from chromosome shattering followed by the random restitching of chromosomal fragments with low copy-number change whereas chromoanasynthesis results from erroneous DNA replication of a chromosome through serial fork stalling and template switching with variable copy-number gains, and chromoplexy refers to the occurrence of multiple inter-and intra-chromosomal translocations and deletions with little or no copy-number alterations in prostate cancer. Cumulating data and experimental models have shown that chromothripsis and chromoanasynthesis may essentially result from lagging chromosome encapsulated in micronuclei or telomere attrition and end-to-end telomere fusion. Conclusion The concept of chromanagenesis has provided new insight into the aetiology of complex structural rearrangements, the connection between defective cell cycle progression and genomic instability, and the complexity of cancer evolution. Increasing reported chromoanagenesis events suggest that these chaotic mechanisms are probably much more frequent than anticipated.
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Affiliation(s)
- Franck Pellestor
- Unit of Chromosomal Genetics, Department of Medical Genetics, Arnaud de Villeneuve Hospital, Montpellier CHRU, 371, avenue du Doyen Gaston Giraud, 34295 Montpellier cedex 5, France.,INSERM 1183 Unit «Genome and Stem Cell Plasticity in Development and Aging », Institute of Regenerative Medicine and Biotherapies, St Eloi Hospital, Montpellier, France
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45
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Barby FF, Bertollo LAC, de Oliveira EA, Yano CF, Hatanaka T, Ráb P, Sember A, Ezaz T, Artoni RF, Liehr T, Al-Rikabi ABH, Trifonov V, de Oliveira EHC, Molina WF, Jegede OI, Tanomtong A, de Bello Cioffi M. Emerging patterns of genome organization in Notopteridae species (Teleostei, Osteoglossiformes) as revealed by Zoo-FISH and Comparative Genomic Hybridization (CGH). Sci Rep 2019; 9:1112. [PMID: 30718776 PMCID: PMC6361938 DOI: 10.1038/s41598-019-38617-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Accepted: 01/03/2019] [Indexed: 11/09/2022] Open
Abstract
Notopteridae (Teleostei, Osteoglossiformes) represents an old fish lineage with ten currently recognized species distributed in African and Southeastern Asian rivers. Their karyotype structures and diploid numbers remained conserved over long evolutionary periods, since African and Asian lineages diverged approximately 120 Mya. However, a significant genetic diversity was already identified for these species using molecular data. Thus, why the evolutionary relationships within Notopteridae are so diverse at the genomic level but so conserved in terms of their karyotypes? In an attempt to develop a more comprehensive picture of the karyotype and genome evolution in Notopteridae, we performed comparative genomic hybridization (CGH) and cross-species (Zoo-FISH) whole chromosome painting experiments to explore chromosome-scale intergenomic divergence among seven notopterid species, collected in different African and Southeast Asian river basins. CGH demonstrated an advanced stage of sequence divergence among the species and Zoo-FISH experiments showed diffuse and limited homology on inter-generic level, showing a temporal reduction of evolutionarily conserved syntenic regions. The sharing of a conserved chromosomal region revealed by Zoo-FISH in these species provides perspectives that several other homologous syntenic regions have remained conserved among their genomes despite long temporal isolation. In summary, Notopteridae is an interesting model for tracking the chromosome evolution as it is (i) ancestral vertebrate group with Gondwanan distribution and (ii) an example of animal group exhibiting karyotype stasis. The present study brings new insights into degree of genome divergence vs. conservation at chromosomal and sub-chromosomal level in representative sampling of this group.
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Affiliation(s)
- Felipe Faix Barby
- Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luiz Km. 235, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - Luiz Antônio Carlos Bertollo
- Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luiz Km. 235, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - Ezequiel Aguiar de Oliveira
- Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luiz Km. 235, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - Cassia Fernanda Yano
- Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luiz Km. 235, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - Terumi Hatanaka
- Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luiz Km. 235, C.P. 676, São Carlos, SP, 13565-905, Brazil
| | - Petr Ráb
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Rumburská 89, Liběchov, 277 21, Czech Republic
| | - Alexandr Sember
- Laboratory of Fish Genetics, Institute of Animal Physiology and Genetics, Czech Academy of Sciences, Rumburská 89, Liběchov, 277 21, Czech Republic
| | - Tariq Ezaz
- Institute for Applied Ecology, University of Canberra, Canberra, ACT 2617, Australia
| | - Roberto Ferreira Artoni
- Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Ponta Grossa, PR, 84030-900, Brazil
| | - Thomas Liehr
- Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Ponta Grossa, PR, 84030-900, Brazil
| | | | - Vladimir Trifonov
- Molecular and Cellular Biology, Russian Academy of Sciences, Novosibirsk, Russia
| | - Edivaldo H C de Oliveira
- Laboratório de Cultura de Tecidos e Citogenética, SAMAM, Instituto Evandro Chagas, Belém, Brazil
| | - Wagner Franco Molina
- Department of Cellular Biology and Genetics, Biosciences Center, Federal University of Rio Grande do Norte, Natal, Brazil
| | - Oladele Ilesanmi Jegede
- Department of Fisheries and Aquaculture, Adamawa State University, P.M.B. 25, Mubi, Adamawa State, Nigeria
| | - Alongklod Tanomtong
- Toxic Substances in Livestock and Aquatic Animals Research Group, KhonKaen University, Muang, KhonKaen, 40002, Thailand
| | - Marcelo de Bello Cioffi
- Departamento de Genética e Evolução, Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luiz Km. 235, C.P. 676, São Carlos, SP, 13565-905, Brazil.
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46
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Black EM, Giunta S. Repetitive Fragile Sites: Centromere Satellite DNA As a Source of Genome Instability in Human Diseases. Genes (Basel) 2018; 9:E615. [PMID: 30544645 PMCID: PMC6315641 DOI: 10.3390/genes9120615] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 12/03/2018] [Accepted: 12/03/2018] [Indexed: 12/31/2022] Open
Abstract
Maintenance of an intact genome is essential for cellular and organismal homeostasis. The centromere is a specialized chromosomal locus required for faithful genome inheritance at each round of cell division. Human centromeres are composed of large tandem arrays of repetitive alpha-satellite DNA, which are often sites of aberrant rearrangements that may lead to chromosome fusions and genetic abnormalities. While the centromere has an essential role in chromosome segregation during mitosis, the long and repetitive nature of the highly identical repeats has greatly hindered in-depth genetic studies, and complete annotation of all human centromeres is still lacking. Here, we review our current understanding of human centromere genetics and epigenetics as well as recent investigations into the role of centromere DNA in disease, with a special focus on cancer, aging, and human immunodeficiency⁻centromeric instability⁻facial anomalies (ICF) syndrome. We also highlight the causes and consequences of genomic instability at these large repetitive arrays and describe the possible sources of centromere fragility. The novel connection between alpha-satellite DNA instability and human pathological conditions emphasizes the importance of obtaining a truly complete human genome assembly and accelerating our understanding of centromere repeats' role in physiology and beyond.
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Affiliation(s)
- Elizabeth M Black
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
| | - Simona Giunta
- Laboratory of Chromosome and Cell Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
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47
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Bughio F, Maggert KA. The peculiar genetics of the ribosomal DNA blurs the boundaries of transgenerational epigenetic inheritance. Chromosome Res 2018; 27:19-30. [PMID: 30511202 DOI: 10.1007/s10577-018-9591-2] [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] [Received: 10/02/2018] [Revised: 10/31/2018] [Accepted: 11/07/2018] [Indexed: 12/20/2022]
Abstract
Our goal is to draw a line-hypothetical in its totality but experimentally supported at each individual step-connecting the ribosomal DNA and the phenomenon of transgenerational epigenetic inheritance of induced phenotypes. The reasonableness of this hypothesis is offset by its implication, that many (or most) (or all) of the cases of induced-and-inherited phenotypes that are seen to persist for generations are instead unmapped induced polymorphisms in the ribosomal DNA, and thus are the consequence of the peculiar and enduringly fascinating genetics of the highly transcribed repeat DNA structure at that locus.
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Affiliation(s)
- Farah Bughio
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA
- University of Arizona Cancer Center, University of Arizona College of Medicine, Tucson, AZ, USA
| | - Keith A Maggert
- Department of Cellular and Molecular Medicine, College of Medicine, University of Arizona, Tucson, AZ, USA.
- University of Arizona Cancer Center, University of Arizona College of Medicine, Tucson, AZ, USA.
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48
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Dvorak J, Wang L, Zhu T, Jorgensen CM, Luo MC, Deal KR, Gu YQ, Gill BS, Distelfeld A, Devos KM, Qi P, McGuire PE. Reassessment of the evolution of wheat chromosomes 4A, 5A, and 7B. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2018; 131:2451-2462. [PMID: 30141064 PMCID: PMC6208953 DOI: 10.1007/s00122-018-3165-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 08/13/2018] [Indexed: 05/02/2023]
Abstract
Comparison of genome sequences of wild emmer wheat and Aegilops tauschii suggests a novel scenario of the evolution of rearranged wheat chromosomes 4A, 5A, and 7B. Past research suggested that wheat chromosome 4A was subjected to a reciprocal translocation T(4AL;5AL)1 that occurred in the diploid progenitor of the wheat A subgenome and to three major rearrangements that occurred in polyploid wheat: pericentric inversion Inv(4AS;4AL)1, paracentric inversion Inv(4AL;4AL)1, and reciprocal translocation T(4AL;7BS)1. Gene collinearity along the pseudomolecules of tetraploid wild emmer wheat (Triticum turgidum ssp. dicoccoides, subgenomes AABB) and diploid Aegilops tauschii (genomes DD) was employed to confirm these rearrangements and to analyze the breakpoints. The exchange of distal regions of chromosome arms 4AS and 4AL due to pericentric inversion Inv(4AS;4AL)1 was detected, and breakpoints were validated with an optical Bionano genome map. Both breakpoints contained satellite DNA. The breakpoints of reciprocal translocation T(4AL;7BS)1 were also found. However, the breakpoints that generated paracentric inversion Inv(4AL;4AL)1 appeared to be collocated with the 4AL breakpoints that had produced Inv(4AS;4AL)1 and T(4AL;7BS)1. Inv(4AS;4AL)1, Inv(4AL;4AL)1, and T(4AL;7BS)1 either originated sequentially, and Inv(4AL;4AL)1 was produced by recurrent chromosome breaks at the same breakpoints that generated Inv(4AS;4AL)1 and T(4AL;7BS)1, or Inv(4AS;4AL)1, Inv(4AL;4AL)1, and T(4AL;7BS)1 originated simultaneously. We prefer the latter hypothesis since it makes fewer assumptions about the sequence of events that produced these chromosome rearrangements.
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Affiliation(s)
- Jan Dvorak
- Department of Plant Sciences, University of California, Davis, CA USA
| | - Le Wang
- Department of Plant Sciences, University of California, Davis, CA USA
| | - Tingting Zhu
- Department of Plant Sciences, University of California, Davis, CA USA
| | - Chad M. Jorgensen
- Department of Plant Sciences, University of California, Davis, CA USA
| | - Ming-Cheng Luo
- Department of Plant Sciences, University of California, Davis, CA USA
| | - Karin R. Deal
- Department of Plant Sciences, University of California, Davis, CA USA
| | - Yong Q. Gu
- Crop Improvement and Genetics Research, USDA-ARS, Albany, CA USA
| | - Bikram S. Gill
- Department of Plant Pathology, Kansas State University, Manhattan, KS USA
| | - Assaf Distelfeld
- School of Plant Sciences and Food Security, Tel Aviv University, Tel Aviv, Israel
| | - Katrien M. Devos
- Institute of Plant Breeding, Genetics and Genomics, Department of Crop and Soil Sciences, University of Georgia, Athens, GA USA
- Department of Plant Biology, University of Georgia, Athens, GA USA
| | - Peng Qi
- Institute of Plant Breeding, Genetics and Genomics, Department of Crop and Soil Sciences, University of Georgia, Athens, GA USA
- Department of Plant Biology, University of Georgia, Athens, GA USA
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49
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HP1 cooperates with CAF-1 to compact heterochromatic transgene repeats in mammalian cells. Sci Rep 2018; 8:14141. [PMID: 30237539 PMCID: PMC6147918 DOI: 10.1038/s41598-018-32381-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 09/04/2018] [Indexed: 11/19/2022] Open
Abstract
The nuclear organization of tightly condensed heterochromatin plays important roles in regulating gene transcription and genome integrity. Heterochromatic domains are usually present at chromosomal regions containing a large array of repeated DNA sequences. We previously showed that integration of a 1,000-copy tandem array of an inducible reporter gene into the genome of mammalian cells induces the formation of a highly compact heterochromatic domain enriched in heterochromatin protein 1 (HP1). It remains to be determined how these DNA repeats are packaged into a heterochromatic form and are silenced. Here, we show that HP1-mediated transgene condensation and silencing require the interaction with PxVxL motif-containing proteins. The chromatin assembly factor 1 (CAF-1) complex concentrates at the transgenic locus through the interaction of its PxVxL motif-containing p150 subunit with HP1. Knockdown of p150 relieves HP1-mediated transgene compaction and repression. When targeted to the transgenic locus, p150 mutants defective in binding HP1 cause transgene decondensation and activation. Taken together, these results suggest that HP1 cooperates with CAF-1 to compact transgene repeats. This study provides important insight into how heterochromatin is maintained at chromosomal regions with abundant DNA repeats.
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50
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Kent TV, Uzunović J, Wright SI. Coevolution between transposable elements and recombination. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0458. [PMID: 29109221 DOI: 10.1098/rstb.2016.0458] [Citation(s) in RCA: 142] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2017] [Indexed: 12/24/2022] Open
Abstract
One of the most striking patterns of genome structure is the tight, typically negative, association between transposable elements (TEs) and meiotic recombination rates. While this is a highly recurring feature of eukaryotic genomes, the mechanisms driving correlations between TEs and recombination remain poorly understood, and distinguishing cause versus effect is challenging. Here, we review the evidence for a relation between TEs and recombination, and discuss the underlying evolutionary forces. Evidence to date suggests that overall TE densities correlate negatively with recombination, but the strength of this correlation varies across element types, and the pattern can be reversed. Results suggest that heterogeneity in the strength of selection against ectopic recombination and gene disruption can drive TE accumulation in regions of low recombination, but there is also strong evidence that the regulation of TEs can influence local recombination rates. We hypothesize that TE insertion polymorphism may be important in driving within-species variation in recombination rates in surrounding genomic regions. Furthermore, the interaction between TEs and recombination may create positive feedback, whereby TE accumulation in non-recombining regions contributes to the spread of recombination suppression. Further investigation of the coevolution between recombination and TEs has important implications for our understanding of the evolution of recombination rates and genome structure.This article is part of the themed issue 'Evolutionary causes and consequences of recombination rate variation in sexual organisms'.
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Affiliation(s)
- Tyler V Kent
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, Ontario, Canada M5S3B2
| | - Jasmina Uzunović
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, Ontario, Canada M5S3B2
| | - Stephen I Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, Ontario, Canada M5S3B2
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