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Talley MJ, Longworth MS. Retrotransposons in embryogenesis and neurodevelopment. Biochem Soc Trans 2024; 52:1159-1171. [PMID: 38716891 DOI: 10.1042/bst20230757] [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: 02/07/2024] [Revised: 04/22/2024] [Accepted: 04/24/2024] [Indexed: 06/27/2024]
Abstract
Retrotransposable elements (RTEs) are genetic elements that can replicate and insert new copies into different genomic locations. RTEs have long been identified as 'parasitic genes', as their mobilization can cause mutations, DNA damage, and inflammation. Interestingly, high levels of retrotransposon activation are observed in early embryogenesis and neurodevelopment, suggesting that RTEs may possess functional roles during these stages of development. Recent studies demonstrate that RTEs can function as transcriptional regulatory elements through mechanisms such as chromatin organization and noncoding RNAs. It is clear, however, that RTE expression and activity must be restrained at some level during development, since overactivation of RTEs during neurodevelopment is associated with several developmental disorders. Further investigation is needed to understand the importance of RTE expression and activity during neurodevelopment and the balance between RTE-regulated development and RTE-mediated pathogenesis.
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Affiliation(s)
- Mary Jo Talley
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, U.S.A
| | - Michelle S Longworth
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, U.S.A
- Cleveland Clinic Lerner College of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44195, U.S.A
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2
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D'Ordine AM, Jogl G, Sedivy JM. Identification and characterization of small molecule inhibitors of the LINE-1 retrotransposon endonuclease. Nat Commun 2024; 15:3883. [PMID: 38719805 PMCID: PMC11078990 DOI: 10.1038/s41467-024-48066-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 04/18/2024] [Indexed: 05/12/2024] Open
Abstract
The long interspersed nuclear element-1 (LINE-1 or L1) retrotransposon is the only active autonomously replicating retrotransposon in the human genome. L1 harms the cell by inserting new copies, generating DNA damage, and triggering inflammation. Therefore, L1 inhibition could be used to treat many diseases associated with these processes. Previous research has focused on inhibition of the L1 reverse transcriptase due to the prevalence of well-characterized inhibitors of related viral enzymes. Here we present the L1 endonuclease as another target for reducing L1 activity. We characterize structurally diverse small molecule endonuclease inhibitors using computational, biochemical, and biophysical methods. We also show that these inhibitors reduce L1 retrotransposition, L1-induced DNA damage, and inflammation reinforced by L1 in senescent cells. These inhibitors could be used for further pharmacological development and as tools to better understand the life cycle of this element and its impact on disease processes.
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Affiliation(s)
- Alexandra M D'Ordine
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
- Center on the Biology of Aging, Brown University, Providence, RI, USA
| | - Gerwald Jogl
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA.
- Center on the Biology of Aging, Brown University, Providence, RI, USA.
| | - John M Sedivy
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA.
- Center on the Biology of Aging, Brown University, Providence, RI, USA.
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3
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Janecki DM, Sen R, Szóstak N, Kajdasz A, Kordyś M, Plawgo K, Pandakov D, Philips A, Warkocki Z. LINE-1 mRNA 3' end dynamics shape its biology and retrotransposition potential. Nucleic Acids Res 2024; 52:3327-3345. [PMID: 38197223 PMCID: PMC11014359 DOI: 10.1093/nar/gkad1251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 12/16/2023] [Accepted: 12/20/2023] [Indexed: 01/11/2024] Open
Abstract
LINE-1 (L1) retrotransposons are mobile genetic elements that create new genomic insertions by a copy-paste mechanism involving L1 RNA/RNP intermediates. L1 encodes two ORFs, of which L1-ORF2p nicks genomic DNA and reverse transcribes L1 mRNA using the nicked DNA as a primer which base-pairs with poly(A) tail of L1 mRNA. To better understand the importance of non-templated L1 3' ends' dynamics and the interplay between L1 3' and 5' ends, we investigated the effects of genomic knock-outs and temporal knock-downs of XRN1, DCP2, and other factors. We hypothesized that in the absence of XRN1, the major 5'→3' exoribonuclease, there would be more L1 mRNA and retrotransposition. Conversely, we observed that loss of XRN1 decreased L1 retrotransposition. This occurred despite slight stabilization of L1 mRNA, but with decreased L1 RNP formation. Similarly, loss of DCP2, the catalytic subunit of the decapping complex, lowered retrotransposition despite increased steady-state levels of L1 proteins. In both XRN1 and DCP2 depletions we observed shortening of L1 3' poly(A) tails and their increased uridylation by TUT4/7. We explain the observed reduction of L1 retrotransposition by the changed qualities of non-templated L1 mRNA 3' ends demonstrating the important role of L1 3' end dynamics in L1 biology.
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Affiliation(s)
- Damian M Janecki
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Raneet Sen
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Natalia Szóstak
- Laboratory of Bioinformatics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Arkadiusz Kajdasz
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Martyna Kordyś
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Kinga Plawgo
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Dmytro Pandakov
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Anna Philips
- Laboratory of Bioinformatics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
| | - Zbigniew Warkocki
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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4
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Lanciano S, Philippe C, Sarkar A, Pratella D, Domrane C, Doucet AJ, van Essen D, Saccani S, Ferry L, Defossez PA, Cristofari G. Locus-level L1 DNA methylation profiling reveals the epigenetic and transcriptional interplay between L1s and their integration sites. CELL GENOMICS 2024; 4:100498. [PMID: 38309261 PMCID: PMC10879037 DOI: 10.1016/j.xgen.2024.100498] [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: 06/02/2023] [Revised: 07/20/2023] [Accepted: 01/09/2024] [Indexed: 02/05/2024]
Abstract
Long interspersed element 1 (L1) retrotransposons are implicated in human disease and evolution. Their global activity is repressed by DNA methylation, but deciphering the regulation of individual copies has been challenging. Here, we combine short- and long-read sequencing to unveil L1 methylation heterogeneity across cell types, families, and individual loci and elucidate key principles involved. We find that the youngest primate L1 families are specifically hypomethylated in pluripotent stem cells and the placenta but not in most tumors. Locally, intronic L1 methylation is intimately associated with gene transcription. Conversely, the L1 methylation state can propagate to the proximal region up to 300 bp. This phenomenon is accompanied by the binding of specific transcription factors, which drive the expression of L1 and chimeric transcripts. Finally, L1 hypomethylation alone is typically insufficient to trigger L1 expression due to redundant silencing pathways. Our results illuminate the epigenetic and transcriptional interplay between retrotransposons and their host genome.
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Affiliation(s)
- Sophie Lanciano
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - Claude Philippe
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - Arpita Sarkar
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - David Pratella
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - Cécilia Domrane
- University Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
| | - Aurélien J Doucet
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - Dominic van Essen
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - Simona Saccani
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France
| | - Laure Ferry
- University Paris Cité, CNRS, Epigenetics and Cell Fate, Paris, France
| | | | - Gael Cristofari
- University Cote d'Azur, INSERM, CNRS, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, France.
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5
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Cristofari G. Snapshots of genetic copy-and-paste machinery in action. Nature 2024; 626:40-42. [PMID: 38287184 DOI: 10.1038/d41586-024-00112-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2024]
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6
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Baldwin ET, van Eeuwen T, Hoyos D, Zalevsky A, Tchesnokov EP, Sánchez R, Miller BD, Di Stefano LH, Ruiz FX, Hancock M, Işik E, Mendez-Dorantes C, Walpole T, Nichols C, Wan P, Riento K, Halls-Kass R, Augustin M, Lammens A, Jestel A, Upla P, Xibinaku K, Congreve S, Hennink M, Rogala KB, Schneider AM, Fairman JE, Christensen SM, Desrosiers B, Bisacchi GS, Saunders OL, Hafeez N, Miao W, Kapeller R, Zaller DM, Sali A, Weichenrieder O, Burns KH, Götte M, Rout MP, Arnold E, Greenbaum BD, Romero DL, LaCava J, Taylor MS. Structures, functions and adaptations of the human LINE-1 ORF2 protein. Nature 2024; 626:194-206. [PMID: 38096902 PMCID: PMC10830420 DOI: 10.1038/s41586-023-06947-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 12/07/2023] [Indexed: 01/05/2024]
Abstract
The LINE-1 (L1) retrotransposon is an ancient genetic parasite that has written around one-third of the human genome through a 'copy and paste' mechanism catalysed by its multifunctional enzyme, open reading frame 2 protein (ORF2p)1. ORF2p reverse transcriptase (RT) and endonuclease activities have been implicated in the pathophysiology of cancer2,3, autoimmunity4,5 and ageing6,7, making ORF2p a potential therapeutic target. However, a lack of structural and mechanistic knowledge has hampered efforts to rationally exploit it. We report structures of the human ORF2p 'core' (residues 238-1061, including the RT domain) by X-ray crystallography and cryo-electron microscopy in several conformational states. Our analyses identified two previously undescribed folded domains, extensive contacts to RNA templates and associated adaptations that contribute to unique aspects of the L1 replication cycle. Computed integrative structural models of full-length ORF2p show a dynamic closed-ring conformation that appears to open during retrotransposition. We characterize ORF2p RT inhibition and reveal its underlying structural basis. Imaging and biochemistry show that non-canonical cytosolic ORF2p RT activity can produce RNA:DNA hybrids, activating innate immune signalling through cGAS/STING and resulting in interferon production6-8. In contrast to retroviral RTs, L1 RT is efficiently primed by short RNAs and hairpins, which probably explains cytosolic priming. Other biochemical activities including processivity, DNA-directed polymerization, non-templated base addition and template switching together allow us to propose a revised L1 insertion model. Finally, our evolutionary analysis demonstrates structural conservation between ORF2p and other RNA- and DNA-dependent polymerases. We therefore provide key mechanistic insights into L1 polymerization and insertion, shed light on the evolutionary history of L1 and enable rational drug development targeting L1.
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Affiliation(s)
| | - Trevor van Eeuwen
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - David Hoyos
- Computational Oncology, Department of Epidemiology & Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Arthur Zalevsky
- Department of Bioengineering and Therapeutic Sciences University of California, San Francisco, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
- Quantitative Biology Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Egor P Tchesnokov
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | | | - Bryant D Miller
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | - Luciano H Di Stefano
- European Research Institute for the Biology of Ageing, University Medical Center Groningen, Groningen, The Netherlands
| | - Francesc Xavier Ruiz
- Center for Advanced Biotechnology and Medicine and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA
| | - Matthew Hancock
- Department of Bioengineering and Therapeutic Sciences University of California, San Francisco, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
- Quantitative Biology Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Esin Işik
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | - Carlos Mendez-Dorantes
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA
| | - Thomas Walpole
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Charles Nichols
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Paul Wan
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Kirsi Riento
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | - Rowan Halls-Kass
- Charles River Laboratories, Chesterford Research Park, Saffron Walden, UK
| | | | - Alfred Lammens
- Proteros Biostructures GmbH, Martinsried, Planegg, Germany
| | - Anja Jestel
- Proteros Biostructures GmbH, Martinsried, Planegg, Germany
| | - Paula Upla
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA
| | - Kera Xibinaku
- Whitehead Institute for Biomedical Research, Cambridge, MA, USA
| | | | | | - Kacper B Rogala
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, USA
- Stanford Cancer Institute, Stanford University School of Medicine, Stanford, CA, USA
| | - Anna M Schneider
- Structural Biology of Selfish RNA, Department of Protein Evolution, Max Planck Institute for Biology, Tübingen, Germany
| | | | | | | | | | | | | | | | | | | | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences University of California, San Francisco, San Francisco, CA, USA
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA, USA
- Quantitative Biology Institute, University of California, San Francisco, San Francisco, CA, USA
| | - Oliver Weichenrieder
- Structural Biology of Selfish RNA, Department of Protein Evolution, Max Planck Institute for Biology, Tübingen, Germany
| | - Kathleen H Burns
- Department of Pathology, Dana Farber Cancer Institute and Harvard Medical School, Boston, MA, USA.
| | - Matthias Götte
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada.
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA.
| | - Eddy Arnold
- Center for Advanced Biotechnology and Medicine and Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ, USA.
| | - Benjamin D Greenbaum
- Computational Oncology, Department of Epidemiology & Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Physiology, Biophysics & Systems Biology, Weill Cornell Medicine, Weill Cornell Medical College, New York, NY, USA.
| | | | - John LaCava
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, NY, USA.
- European Research Institute for the Biology of Ageing, University Medical Center Groningen, Groningen, The Netherlands.
| | - Martin S Taylor
- Department of Pathology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
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7
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Zhang J, Tang J, Li G, Li N, Wang J, Yao R, Yu T. SINE-VNTR-Alu retrotransposon insertion as a novel mutational event underlying Glanzmann thrombasthenia. J Thromb Haemost 2023; 21:3597-3607. [PMID: 37604334 DOI: 10.1016/j.jtha.2023.08.012] [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: 01/09/2023] [Revised: 08/01/2023] [Accepted: 08/06/2023] [Indexed: 08/23/2023]
Abstract
BACKGROUND Glanzmann thrombasthenia (GT) is an autosomal recessive platelet aggregation disorder caused by mutations in ITGA2B or ITGB3. OBJECTIVES We aimed to assess the phenotype and investigate the genetic etiology of a GT pedigree. METHODS A patient with bleeding manifestations and mild mental retardation was enrolled. Complete blood count, coagulation, and platelet aggregation tests were performed. Causal mutations were identified via whole exome and genome sequencing and subsequently confirmed through polymerase chain reaction and Sanger sequencing. The transcription of ITGB3 was characterized using RNA sequencing and reverse transcription polymerase chain reaction. The αⅡb and β3 biosynthesis was investigated via whole blood flow cytometry and in vitro studies. RESULTS GT was diagnosed in a patient with defective platelet aggregation. Novel compound heterozygous ITGB3 variants were identified, with a maternal nonsense mutation (c.2222G>A, p.Trp741∗) and a paternal SINE-VNTR-Alu (SVA) retrotransposon insertion. The 5' truncated SVA element was inserted in a sense orientation in intron 11 of ITGB3, resulting in aberrant splicing of ITGB3 and significantly reducing β3 protein content. Meanwhile, both the expression and transportation of β3 were damaged by the ITGB3 c.2222G>A. Almost no αⅡb and β3 expressions were detected on the patient's platelets surface. CONCLUSION Novel compound heterozygous ITGB3 mutations were identified in the GT pedigree, resulting in defects of αⅡbβ3 biosynthesis. This is the first report of SVA retrotransposon insertion in the genetic pathogenesis of GT. Our study highlights the importance of combining multiple high-throughput sequencing technologies for the molecular diagnosis of genetic disorders.
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Affiliation(s)
- Jiasheng Zhang
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jie Tang
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Guoqiang Li
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Niu Li
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jian Wang
- International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Ruen Yao
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
| | - Tingting Yu
- Department of Medical Genetics and Molecular Diagnostic Laboratory, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
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8
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Bona N, Crossan GP. Fanconi anemia DNA crosslink repair factors protect against LINE-1 retrotransposition during mouse development. Nat Struct Mol Biol 2023; 30:1434-1445. [PMID: 37580626 PMCID: PMC10584689 DOI: 10.1038/s41594-023-01067-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 07/13/2023] [Indexed: 08/16/2023]
Abstract
Long interspersed nuclear element 1 (LINE-1) is the only autonomous retrotransposon in humans and new integrations are a major source of genetic variation between individuals. These events can also lead to de novo germline mutations, giving rise to heritable genetic diseases. Recently, a role for DNA repair in regulating these events has been identified. Here we find that Fanconi anemia (FA) DNA crosslink repair factors act in a common pathway to prevent retrotransposition. We purify recombinant SLX4-XPF-ERCC1, the crosslink repair incision complex, and find that it cleaves putative nucleic acid intermediates of retrotransposition. Mice deficient in upstream crosslink repair signaling (FANCA), a downstream component (FANCD2) or the nuclease XPF-ERCC1 show increased LINE-1 retrotransposition in vivo. Organisms limit retrotransposition through transcriptional silencing but this protection is attenuated during early development leaving the zygote vulnerable. We find that during this window of vulnerability, DNA crosslink repair acts as a failsafe to prevent retrotransposition. Together, our results indicate that the FA DNA crosslink repair pathway acts together to protect against mutation by restricting LINE-1 retrotransposition.
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Luqman-Fatah A, Miyoshi T. Human LINE-1 retrotransposons: impacts on the genome and regulation by host factors. Genes Genet Syst 2023; 98:121-154. [PMID: 36436935 DOI: 10.1266/ggs.22-00038] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Genome sequencing revealed that nearly half of the human genome is comprised of transposable elements. Although most of these elements have been rendered inactive due to mutations, full-length intact long interspersed element-1 (LINE-1 or L1) copies retain the ability to mobilize through RNA intermediates by a so-called "copy-and-paste" mechanism, termed retrotransposition. L1 is the only known autonomous mobile genetic element in the genome, and its retrotransposition contributes to inter- or intra-individual genetic variation within the human population. However, L1 retrotransposition also poses a threat to genome integrity due to gene disruption and chromosomal instability. Moreover, recent studies suggest that aberrant L1 expression can impact human health by causing diseases such as cancer and chronic inflammation that might lead to autoimmune disorders. To counteract these adverse effects, the host cells have evolved multiple layers of defense mechanisms at the epigenetic, RNA and protein levels. Intriguingly, several host factors have also been reported to facilitate L1 retrotransposition, suggesting that there is competition between negative and positive regulation of L1 by host factors. Here, we summarize the known host proteins that regulate L1 activity at different stages of the replication cycle and discuss how these factors modulate disease-associated phenotypes caused by L1.
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Affiliation(s)
- Ahmad Luqman-Fatah
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University
- Department of Stress Response, Radiation Biology Center, Graduate School of Biostudies, Kyoto University
| | - Tomoichiro Miyoshi
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University
- Department of Stress Response, Radiation Biology Center, Graduate School of Biostudies, Kyoto University
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10
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Warkocki Z. An update on post-transcriptional regulation of retrotransposons. FEBS Lett 2023; 597:380-406. [PMID: 36460901 DOI: 10.1002/1873-3468.14551] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2022] [Revised: 11/09/2022] [Accepted: 11/18/2022] [Indexed: 12/04/2022]
Abstract
Retrotransposons, including LINE-1, Alu, SVA, and endogenous retroviruses, are one of the major constituents of human genomic repetitive sequences. Through the process of retrotransposition, some of them occasionally insert into new genomic locations by a copy-paste mechanism involving RNA intermediates. Irrespective of de novo genomic insertions, retrotransposon expression can lead to DNA double-strand breaks and stimulate cellular innate immunity through endogenous patterns. As a result, retrotransposons are tightly regulated by multi-layered regulatory processes to prevent the dangerous effects of their expression. In recent years, significant progress was made in revealing how retrotransposon biology intertwines with general post-transcriptional RNA metabolism. Here, I summarize current knowledge on the involvement of post-transcriptional factors in the biology of retrotransposons, focusing on LINE-1. I emphasize general RNA metabolisms such as methylation of adenine (m6 A), RNA 3'-end polyadenylation and uridylation, RNA decay and translation regulation. I discuss the effects of retrotransposon RNP sequestration in cytoplasmic bodies and autophagy. Finally, I summarize how innate immunity restricts retrotransposons and how retrotransposons make use of cellular enzymes, including the DNA repair machinery, to complete their replication cycles.
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Affiliation(s)
- Zbigniew Warkocki
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland
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11
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Garcia-Cañadas M, Sanchez-Luque FJ, Sanchez L, Rojas J, Garcia Perez JL. LINE-1 Retrotransposition Assays in Embryonic Stem Cells. Methods Mol Biol 2023; 2607:257-309. [PMID: 36449167 DOI: 10.1007/978-1-0716-2883-6_13] [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] [Indexed: 06/17/2023]
Abstract
The ongoing mobilization of active non-long terminal repeat (LTR) retrotransposons continues to impact the genomes of most mammals, including humans and rodents. Non-LTR retrotransposons mobilize using an intermediary RNA and a copy-and-paste mechanism termed retrotransposition. Non-LTR retrotransposons are subdivided into long and short interspersed elements (LINEs and SINEs, respectively), depending on their size and autonomy; while active class 1 LINEs (LINE-1s or L1s) encode the enzymatic machinery required to mobilize in cis, active SINEs use the enzymatic machinery of active LINE-1s to mobilize in trans. The mobilization mechanism used by LINE-1s/SINEs was exploited to develop ingenious plasmid-based retrotransposition assays in cultured cells, which typically exploit a reporter gene that can only be activated after a round of retrotransposition. Retrotransposition assays, in cis or in trans, are instrumental tools to study the biology of mammalian LINE-1s and SINEs. In fact, these and other biochemical/genetic assays were used to uncover that endogenous mammalian LINE-1s/SINEs naturally retrotranspose during early embryonic development. However, embryonic stem cells (ESCs) are typically used as a cellular model in these and other studies interrogating LINE-1/SINE expression/regulation during early embryogenesis. Thus, human and mouse ESCs represent an excellent model to understand how active retrotransposons are regulated and how their activity impacts the germline. Here, we describe robust and quantitative protocols to study human/mouse LINE-1 (in cis) and SINE (in trans) retrotransposition using (human and mice) ESCs. These protocols are designed to study the mobilization of active non-LTR retrotransposons in a cellular physiologically relevant context.
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Affiliation(s)
- Marta Garcia-Cañadas
- Pfizer-University of Granada-Andalusian Government Centre for Genomics and Oncological Research (GENYO), PTS Granada, Granada, Spain.
| | - Francisco J Sanchez-Luque
- Institute of Parasitology and Biomedicine "Lopez-Neyra" (IPBLN), Spanish National Research Council (CSIC), PTS Granada, Granada, Spain
| | - Laura Sanchez
- Pfizer-University of Granada-Andalusian Government Centre for Genomics and Oncological Research (GENYO), PTS Granada, Granada, Spain
| | - Johana Rojas
- Pfizer-University of Granada-Andalusian Government Centre for Genomics and Oncological Research (GENYO), PTS Granada, Granada, Spain
| | - Jose L Garcia Perez
- Pfizer-University of Granada-Andalusian Government Centre for Genomics and Oncological Research (GENYO), PTS Granada, Granada, Spain.
- MRC Human Genetics Unit, Institute of Genetics and Cancer (IGC)/University of Edinburgh, Western General Hospital Campus, Edinburgh, UK.
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12
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Gerdes P, Lim SM, Ewing AD, Larcombe MR, Chan D, Sanchez-Luque FJ, Walker L, Carleton AL, James C, Knaupp AS, Carreira PE, Nefzger CM, Lister R, Richardson SR, Polo JM, Faulkner GJ. Retrotransposon instability dominates the acquired mutation landscape of mouse induced pluripotent stem cells. Nat Commun 2022; 13:7470. [PMID: 36463236 PMCID: PMC9719517 DOI: 10.1038/s41467-022-35180-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 11/22/2022] [Indexed: 12/04/2022] Open
Abstract
Induced pluripotent stem cells (iPSCs) can in principle differentiate into any cell of the body, and have revolutionized biomedical research and regenerative medicine. Unlike their human counterparts, mouse iPSCs (miPSCs) are reported to silence transposable elements and prevent transposable element-mediated mutagenesis. Here we apply short-read or Oxford Nanopore Technologies long-read genome sequencing to 38 bulk miPSC lines reprogrammed from 10 parental cell types, and 18 single-cell miPSC clones. While single nucleotide variants and structural variants restricted to miPSCs are rare, we find 83 de novo transposable element insertions, including examples intronic to Brca1 and Dmd. LINE-1 retrotransposons are profoundly hypomethylated in miPSCs, beyond other transposable elements and the genome overall, and harbor alternative protein-coding gene promoters. We show that treatment with the LINE-1 inhibitor lamivudine does not hinder reprogramming and efficiently blocks endogenous retrotransposition, as detected by long-read genome sequencing. These experiments reveal the complete spectrum and potential significance of mutations acquired by miPSCs.
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Affiliation(s)
- Patricia Gerdes
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Sue Mei Lim
- grid.1002.30000 0004 1936 7857Department of Anatomy & Developmental Biology, Monash University, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC 3800 Australia
| | - Adam D. Ewing
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Michael R. Larcombe
- grid.1002.30000 0004 1936 7857Department of Anatomy & Developmental Biology, Monash University, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC 3800 Australia
| | - Dorothy Chan
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Francisco J. Sanchez-Luque
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia ,grid.418805.00000 0004 0500 8423GENYO. Pfizer-University of Granada-Andalusian Government Centre for Genomics and Oncological Research, PTS, Granada, 18016 Spain
| | - Lucinda Walker
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Alexander L. Carleton
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Cini James
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Anja S. Knaupp
- grid.1002.30000 0004 1936 7857Department of Anatomy & Developmental Biology, Monash University, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC 3800 Australia
| | - Patricia E. Carreira
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Christian M. Nefzger
- grid.1002.30000 0004 1936 7857Department of Anatomy & Developmental Biology, Monash University, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC 3800 Australia
| | - Ryan Lister
- grid.1012.20000 0004 1936 7910Australian Research Council Centre of Excellence in Plant Energy Biology, School of Molecular Sciences, The University of Western Australia, Perth, WA 6009 Australia ,grid.431595.f0000 0004 0469 0045Harry Perkins Institute of Medical Research, Perth, WA 6009 Australia
| | - Sandra R. Richardson
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
| | - Jose M. Polo
- grid.1002.30000 0004 1936 7857Department of Anatomy & Developmental Biology, Monash University, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Development and Stem Cells Program, Monash Biomedicine Discovery Institute, Melbourne, VIC 3800 Australia ,grid.1002.30000 0004 1936 7857Australian Regenerative Medicine Institute, Monash University, Melbourne, VIC 3800 Australia ,grid.1010.00000 0004 1936 7304Adelaide Centre for Epigenetics and The South Australian Immunogenomics Cancer Institute, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide, SA 5005 Australia
| | - Geoffrey J. Faulkner
- grid.1003.20000 0000 9320 7537Mater Research Institute - University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia ,grid.1003.20000 0000 9320 7537Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072 Australia
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13
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Hepatitis B virus polymerase restricts LINE-1 mobility. Gene 2022; 850:146943. [PMID: 36198378 DOI: 10.1016/j.gene.2022.146943] [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: 05/23/2022] [Revised: 09/06/2022] [Accepted: 09/28/2022] [Indexed: 11/21/2022]
Abstract
Long interspersed element-1 (LINE-1, L1) transposable element (TE) composes about 17% of the human genome. However, genetic and biochemical interactions between L1 and hepatitis B virus (HBV) remain poorly understood. In this study, I found that HBV restricts L1 retrotransposition in a reverse transcriptase (RT)-independent manner. Notably, HBV polymerase (Pol) strongly inhibited L1 retrotransposition. Indeed, the ribonuclease H (RNase H) domain was essential for inhibition of L1 retrotransposition. The L1 ORF1p RNA-binding protein predominantly localized into cytoplasmic RNA granule termed P-body. However, HBV Pol hijacked L1 ORF1p from P-body through an interaction with L1 ORF1p, when both proteins were co-expressed. Furthermore, HBV Pol repressed the L1 5' untranslated region (UTR). Altogether, HBV seems to restrict L1 mobility at multiple steps. Thus, these results suggest a novel function or activity of HBV Pol in regulation of L1 retrotransposition.
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14
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Porubsky D, Höps W, Ashraf H, Hsieh P, Rodriguez-Martin B, Yilmaz F, Ebler J, Hallast P, Maria Maggiolini FA, Harvey WT, Henning B, Audano PA, Gordon DS, Ebert P, Hasenfeld P, Benito E, Zhu Q, Lee C, Antonacci F, Steinrücken M, Beck CR, Sanders AD, Marschall T, Eichler EE, Korbel JO. Recurrent inversion polymorphisms in humans associate with genetic instability and genomic disorders. Cell 2022; 185:1986-2005.e26. [PMID: 35525246 PMCID: PMC9563103 DOI: 10.1016/j.cell.2022.04.017] [Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 02/14/2022] [Accepted: 04/08/2022] [Indexed: 12/13/2022]
Abstract
Unlike copy number variants (CNVs), inversions remain an underexplored genetic variation class. By integrating multiple genomic technologies, we discover 729 inversions in 41 human genomes. Approximately 85% of inversions <2 kbp form by twin-priming during L1 retrotransposition; 80% of the larger inversions are balanced and affect twice as many nucleotides as CNVs. Balanced inversions show an excess of common variants, and 72% are flanked by segmental duplications (SDs) or retrotransposons. Since flanking repeats promote non-allelic homologous recombination, we developed complementary approaches to identify recurrent inversion formation. We describe 40 recurrent inversions encompassing 0.6% of the genome, showing inversion rates up to 2.7 × 10-4 per locus per generation. Recurrent inversions exhibit a sex-chromosomal bias and co-localize with genomic disorder critical regions. We propose that inversion recurrence results in an elevated number of heterozygous carriers and structural SD diversity, which increases mutability in the population and predisposes specific haplotypes to disease-causing CNVs.
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15
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Domazet-Lošo T. mRNA Vaccines: Why Is the Biology of Retroposition Ignored? Genes (Basel) 2022; 13:719. [PMID: 35627104 PMCID: PMC9141755 DOI: 10.3390/genes13050719] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 04/14/2022] [Accepted: 04/15/2022] [Indexed: 02/07/2023] Open
Abstract
The major advantage of mRNA vaccines over more conventional approaches is their potential for rapid development and large-scale deployment in pandemic situations. In the current COVID-19 crisis, two mRNA COVID-19 vaccines have been conditionally approved and broadly applied, while others are still in clinical trials. However, there is no previous experience with the use of mRNA vaccines on a large scale in the general population. This warrants a careful evaluation of mRNA vaccine safety properties by considering all available knowledge about mRNA molecular biology and evolution. Here, I discuss the pervasive claim that mRNA-based vaccines cannot alter genomes. Surprisingly, this notion is widely stated in the mRNA vaccine literature but never supported by referencing any primary scientific papers that would specifically address this question. This discrepancy becomes even more puzzling if one considers previous work on the molecular and evolutionary aspects of retroposition in murine and human populations that clearly documents the frequent integration of mRNA molecules into genomes, including clinical contexts. By performing basic comparisons, I show that the sequence features of mRNA vaccines meet all known requirements for retroposition using L1 elements-the most abundant autonomously active retrotransposons in the human genome. In fact, many factors associated with mRNA vaccines increase the possibility of their L1-mediated retroposition. I conclude that is unfounded to a priori assume that mRNA-based therapeutics do not impact genomes and that the route to genome integration of vaccine mRNAs via endogenous L1 retroelements is easily conceivable. This implies that we urgently need experimental studies that would rigorously test for the potential retroposition of vaccine mRNAs. At present, the insertional mutagenesis safety of mRNA-based vaccines should be considered unresolved.
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Affiliation(s)
- Tomislav Domazet-Lošo
- Laboratory of Evolutionary Genetics, Division of Molecular Biology, Ruđer Bošković Institute, Bijenička Cesta 54, HR-10000 Zagreb, Croatia;
- School of Medicine, Catholic University of Croatia, Ilica 242, HR-10000 Zagreb, Croatia
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16
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Miller I, Totrov M, Korotchkina L, Kazyulkin DN, Gudkov AV, Korolev S. Structural dissection of sequence recognition and catalytic mechanism of human LINE-1 endonuclease. Nucleic Acids Res 2021; 49:11350-11366. [PMID: 34554261 PMCID: PMC8565326 DOI: 10.1093/nar/gkab826] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/03/2021] [Accepted: 09/08/2021] [Indexed: 11/12/2022] Open
Abstract
Long interspersed nuclear element-1 (L1) is an autonomous non-LTR retrotransposon comprising ∼20% of the human genome. L1 self-propagation causes genomic instability and is strongly associated with aging, cancer and other diseases. The endonuclease domain of L1’s ORFp2 protein (L1-EN) initiates de novo L1 integration by nicking the consensus sequence 5′-TTTTT/AA-3′. In contrast, related nucleases including structurally conserved apurinic/apyrimidinic endonuclease 1 (APE1) are non-sequence specific. To investigate mechanisms underlying sequence recognition and catalysis by L1-EN, we solved crystal structures of L1-EN complexed with DNA substrates. This showed that conformational properties of the preferred sequence drive L1-EN’s sequence-specificity and catalysis. Unlike APE1, L1-EN does not bend the DNA helix, but rather causes ‘compression’ near the cleavage site. This provides multiple advantages for L1-EN’s role in retrotransposition including facilitating use of the nicked poly-T DNA strand as a primer for reverse transcription. We also observed two alternative conformations of the scissile bond phosphate, which allowed us to model distinct conformations for a nucleophilic attack and a transition state that are likely applicable to the entire family of nucleases. This work adds to our mechanistic understanding of L1-EN and related nucleases and should facilitate development of L1-EN inhibitors as potential anticancer and antiaging therapeutics.
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Affiliation(s)
- Ian Miller
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
| | | | | | | | - Andrei V Gudkov
- Genome Protection, Inc., Buffalo, NY 14203, USA.,Roswell Park Comprehensive Cancer Center, Buffalo, NY 14263, USA
| | - Sergey Korolev
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO 63104, USA
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17
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Factors Regulating the Activity of LINE1 Retrotransposons. Genes (Basel) 2021; 12:genes12101562. [PMID: 34680956 PMCID: PMC8535693 DOI: 10.3390/genes12101562] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 12/15/2022] Open
Abstract
LINE-1 (L1) is a class of autonomous mobile genetic elements that form somatic mosaicisms in various tissues of the organism. The activity of L1 retrotransposons is strictly controlled by many factors in somatic and germ cells at all stages of ontogenesis. Alteration of L1 activity was noted in a number of diseases: in neuropsychiatric and autoimmune diseases, as well as in various forms of cancer. Altered activity of L1 retrotransposons for some pathologies is associated with epigenetic changes and defects in the genes involved in their repression. This review discusses the molecular genetic mechanisms of the retrotransposition and regulation of the activity of L1 elements. The contribution of various factors controlling the expression and distribution of L1 elements in the genome occurs at all stages of the retrotransposition. The regulation of L1 elements at the transcriptional, post-transcriptional and integration into the genome stages is described in detail. Finally, this review also focuses on the evolutionary aspects of L1 accumulation and their interplay with the host regulation system.
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18
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Smits N, Rasmussen J, Bodea GO, Amarilla AA, Gerdes P, Sanchez-Luque FJ, Ajjikuttira P, Modhiran N, Liang B, Faivre J, Deveson IW, Khromykh AA, Watterson D, Ewing AD, Faulkner GJ. No evidence of human genome integration of SARS-CoV-2 found by long-read DNA sequencing. Cell Rep 2021; 36:109530. [PMID: 34380018 PMCID: PMC8316065 DOI: 10.1016/j.celrep.2021.109530] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/21/2021] [Accepted: 07/22/2021] [Indexed: 01/28/2023] Open
Abstract
A recent study proposed that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) hijacks the LINE-1 (L1) retrotransposition machinery to integrate into the DNA of infected cells. If confirmed, this finding could have significant clinical implications. Here, we apply deep (>50×) long-read Oxford Nanopore Technologies (ONT) sequencing to HEK293T cells infected with SARS-CoV-2 and do not find the virus integrated into the genome. By examining ONT data from separate HEK293T cultivars, we completely resolve 78 L1 insertions arising in vitro in the absence of L1 overexpression systems. ONT sequencing applied to hepatitis B virus (HBV)-positive liver cancer tissues located a single HBV insertion. These experiments demonstrate reliable resolution of retrotransposon and exogenous virus insertions by ONT sequencing. That we find no evidence of SARS-CoV-2 integration suggests that such events are, at most, extremely rare in vivo and therefore are unlikely to drive oncogenesis or explain post-recovery detection of the virus.
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Affiliation(s)
- Nathan Smits
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD 4102, Australia
| | - Jay Rasmussen
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia
| | - Gabriela O Bodea
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD 4102, Australia; Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia
| | - Alberto A Amarilla
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Patricia Gerdes
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD 4102, Australia
| | - Francisco J Sanchez-Luque
- GENYO, Pfizer-University of Granada-Andalusian Government Centre for Genomics and Oncological Research, PTS Granada 18016, Spain; MRC Human Genetics Unit, Institute of Genetics and Cancer (IGC), University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Prabha Ajjikuttira
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia
| | - Naphak Modhiran
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Benjamin Liang
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia
| | - Jamila Faivre
- INSERM, U1193, Paul-Brousse University Hospital, Hepatobiliary Centre, Villejuif 94800, France
| | - Ira W Deveson
- Kinghorn Centre for Clinical Genomics, Garvan Institute of Medical Research, Sydney, NSW 2010, Australia; St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2052, Australia
| | - Alexander A Khromykh
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia; Australian Infectious Diseases Research Centre, Global Virus Network Centre of Excellence, Brisbane, QLD 4072, Australia
| | - Daniel Watterson
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia; Australian Infectious Diseases Research Centre, Global Virus Network Centre of Excellence, Brisbane, QLD 4072, Australia
| | - Adam D Ewing
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD 4102, Australia
| | - Geoffrey J Faulkner
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, QLD 4102, Australia; Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072, Australia.
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19
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LeBien J, McCollam G, Atallah J. An in silico model of LINE-1-mediated neoplastic evolution. Bioinformatics 2020; 36:4144-4153. [PMID: 32365170 DOI: 10.1093/bioinformatics/btaa279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 04/19/2020] [Accepted: 04/24/2020] [Indexed: 11/13/2022] Open
Abstract
MOTIVATION Recent research has uncovered roles for transposable elements (TEs) in multiple evolutionary processes, ranging from somatic evolution in cancer to putatively adaptive germline evolution across species. Most models of TE population dynamics, however, have not incorporated actual genome sequence data. The effect of site integration preferences of specific TEs on evolutionary outcomes and the effects of different selection regimes on TE dynamics in a specific genome are unknown. We present a stochastic model of LINE-1 (L1) transposition in human cancer. This system was chosen because the transposition of L1 elements is well understood, the population dynamics of cancer tumors has been modeled extensively, and the role of L1 elements in cancer progression has garnered interest in recent years. RESULTS Our model predicts that L1 retrotransposition (RT) can play either advantageous or deleterious roles in tumor progression, depending on the initial lesion size, L1 insertion rate and tumor driver genes. Small changes in the RT rate or set of driver tumor-suppressor genes (TSGs) were observed to alter the dynamics of tumorigenesis. We found high variation in the density of L1 target sites across human protein-coding genes. We also present an analysis, across three cancer types, of the frequency of homozygous TSG disruption in wild-type hosts compared to those with an inherited driver allele. AVAILABILITY AND IMPLEMENTATION Source code is available at https://github.com/atallah-lab/neoplastic-evolution. CONTACT jlebien@uno.edu. SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Jack LeBien
- Department of Biological Sciences, The University of New, Orleans, New Orleans, LA 70148, USA
| | - Gerald McCollam
- Advanced Academic Programs, John Hopkins University, Baltimore, MD 21218, USA
| | - Joel Atallah
- Department of Biological Sciences, The University of New, Orleans, New Orleans, LA 70148, USA
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20
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Miyoshi T, Makino T, Moran JV. Poly(ADP-Ribose) Polymerase 2 Recruits Replication Protein A to Sites of LINE-1 Integration to Facilitate Retrotransposition. Mol Cell 2019; 75:1286-1298.e12. [PMID: 31473101 PMCID: PMC6754305 DOI: 10.1016/j.molcel.2019.07.018] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 05/23/2019] [Accepted: 07/12/2019] [Indexed: 10/26/2022]
Abstract
Long interspersed element-1 (LINE-1 or L1) retrotransposition poses a threat to genome integrity, and cells have evolved mechanisms to restrict retrotransposition. However, how cellular proteins facilitate L1 retrotransposition requires elucidation. Here, we demonstrate that single-strand DNA breaks induced by the L1 endonuclease trigger the recruitment of poly(ADP-ribose) polymerase 2 (PARP2) to L1 integration sites and that PARP2 activation leads to the subsequent recruitment of the replication protein A (RPA) complex to facilitate retrotransposition. We further demonstrate that RPA directly binds activated PARP2 through poly(ADP-ribosyl)ation and can protect single-strand L1 integration intermediates from APOBEC3-mediated cytidine deamination in vitro. Paradoxically, we provide evidence that RPA can guide APOBEC3A, and perhaps other APOBEC3 proteins, to sites of L1 integration. Thus, the interplay of L1-encoded and evolutionarily conserved cellular proteins is required for efficient retrotransposition; however, these interactions also may be exploited to restrict L1 retrotransposition in the human genome.
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Affiliation(s)
- Tomoichiro Miyoshi
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan; Department of Stress Response, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan; Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109-5618, USA.
| | - Takeshi Makino
- Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan; Department of Stress Response, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - John V Moran
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, MI 48109-5618, USA; Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109-5618, USA.
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21
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Saleh A, Macia A, Muotri AR. Transposable Elements, Inflammation, and Neurological Disease. Front Neurol 2019; 10:894. [PMID: 31481926 PMCID: PMC6710400 DOI: 10.3389/fneur.2019.00894] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 08/02/2019] [Indexed: 12/13/2022] Open
Abstract
Transposable Elements (TE) are mobile DNA elements that can replicate and insert themselves into different locations within the host genome. Their propensity to self-propagate has a myriad of consequences and yet their biological significance is not well-understood. Indeed, retrotransposons have evaded evolutionary attempts at repression and may contribute to somatic mosaicism. Retrotransposons are emerging as potent regulatory elements within the human genome. In the diseased state, there is mounting evidence that endogenous retroelements play a role in etiopathogenesis of inflammatory diseases, with a disposition for both autoimmune and neurological disorders. We postulate that active mobile genetic elements contribute more to human disease pathogenesis than previously thought.
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Affiliation(s)
- Aurian Saleh
- Department of Pediatrics, Rady Children's Hospital San Diego, University of California, San Diego, San Diego, CA, United States
| | - Angela Macia
- Department of Pediatrics, Rady Children's Hospital San Diego, University of California, San Diego, San Diego, CA, United States
| | - Alysson R Muotri
- Department of Pediatrics, Rady Children's Hospital San Diego, University of California, San Diego, San Diego, CA, United States
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22
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Kawano K, Doucet AJ, Ueno M, Kariya R, An W, Marzetta F, Kuroki M, Turelli P, Sukegawa S, Okada S, Strebel K, Trono D, Ariumi Y. HIV-1 Vpr and p21 restrict LINE-1 mobility. Nucleic Acids Res 2019; 46:8454-8470. [PMID: 30085096 PMCID: PMC6144823 DOI: 10.1093/nar/gky688] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 07/18/2018] [Indexed: 01/12/2023] Open
Abstract
Long interspersed element-1 (LINE-1, L1) composes ∼17% of the human genome. However, genetic interactions between L1 and human immunodeficiency virus type 1 (HIV-1) remain poorly understood. In this study, we found that HIV-1 suppresses L1 retrotransposition. Notably, HIV-1 Vpr strongly inhibited retrotransposition without inhibiting L1 promoter activity. Since Vpr is known to regulate host cell cycle, we examined the possibility whether Vpr suppresses L1 retrotransposition in a cell cycle dependent manner. We showed that the inhibitory effect of a mutant Vpr (H71R), which is unable to arrest the cell cycle, was significantly relieved compared with that of wild-type Vpr, suggesting that Vpr suppresses L1 mobility in a cell cycle dependent manner. Furthermore, a host cell cycle regulator p21Waf1 strongly suppressed L1 retrotransposition. The N-terminal kinase inhibitory domain (KID) of p21 was required for this inhibitory effect. Another KID-containing host cell cycle regulator p27Kip1 also strongly suppressed L1 retrotransposition. We showed that Vpr and p21 coimmunoprecipitated with L1 ORF2p and they suppressed the L1 reverse transcriptase activity in LEAP assay, suggesting that Vpr and p21 inhibit ORF2p-mediated reverse transcription. Altogether, our results suggest that viral and host cell cycle regulatory machinery limit L1 mobility in cultured cells.
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Affiliation(s)
- Koudai Kawano
- Center for AIDS Research, Kumamoto University, Kumamoto 860-0811, Japan
| | - Aurélien J Doucet
- Institute for Research on Cancer and Aging, Nice (IRCAN), INSERM U1081, CNRS UMR 7284, Université de Nice-Sophia-Antipolis, Faculté de Médecine, 06107 Nice Cedex 2, France
| | - Mikinori Ueno
- Center for AIDS Research, Kumamoto University, Kumamoto 860-0811, Japan
| | - Ryusho Kariya
- Center for AIDS Research, Kumamoto University, Kumamoto 860-0811, Japan
| | - Wenfeng An
- Department of Pharmaceutical Sciences, South Dakota State University, Brookings, SD 57007, USA
| | - Flavia Marzetta
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
| | - Misao Kuroki
- Center for AIDS Research, Kumamoto University, Kumamoto 860-0811, Japan
| | - Priscilla Turelli
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
| | - Sayaka Sukegawa
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0460, USA.,Clinical Research Center, Nagoya Medical Center, Nagoya 460-0001, Japan
| | - Seiji Okada
- Center for AIDS Research, Kumamoto University, Kumamoto 860-0811, Japan
| | - Klaus Strebel
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892-0460, USA
| | - Didier Trono
- School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne CH-1015, Switzerland
| | - Yasuo Ariumi
- Center for AIDS Research, Kumamoto University, Kumamoto 860-0811, Japan
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23
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Flasch DA, Macia Á, Sánchez L, Ljungman M, Heras SR, García-Pérez JL, Wilson TE, Moran JV. Genome-wide de novo L1 Retrotransposition Connects Endonuclease Activity with Replication. Cell 2019; 177:837-851.e28. [PMID: 30955886 DOI: 10.1016/j.cell.2019.02.050] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 01/10/2019] [Accepted: 02/25/2019] [Indexed: 12/18/2022]
Abstract
L1 retrotransposon-derived sequences comprise approximately 17% of the human genome. Darwinian selective pressures alter L1 genomic distributions during evolution, confounding the ability to determine initial L1 integration preferences. Here, we generated high-confidence datasets of greater than 88,000 engineered L1 insertions in human cell lines that act as proxies for cells that accommodate retrotransposition in vivo. Comparing these insertions to a null model, in which L1 endonuclease activity is the sole determinant dictating L1 integration preferences, demonstrated that L1 insertions are not significantly enriched in genes, transcribed regions, or open chromatin. By comparison, we provide compelling evidence that the L1 endonuclease disproportionately cleaves predominant lagging strand DNA replication templates, while lagging strand 3'-hydroxyl groups may prime endonuclease-independent L1 retrotransposition in a Fanconi anemia cell line. Thus, acquisition of an endonuclease domain, in conjunction with the ability to integrate into replicating DNA, allowed L1 to become an autonomous, interspersed retrotransposon.
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Affiliation(s)
- Diane A Flasch
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA.
| | - Ángela Macia
- Department of Genomic Medicine, GENYO: Centre for Genomics and Oncology (Pfizer-University of Granada and Andalusian Regional Government), PTS Granada, 18016, Spain
| | - Laura Sánchez
- Department of Genomic Medicine, GENYO: Centre for Genomics and Oncology (Pfizer-University of Granada and Andalusian Regional Government), PTS Granada, 18016, Spain
| | - Mats Ljungman
- Department of Radiation Oncology, University of Michigan Comprehensive Cancer Center, Translational Oncology Program and Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan, 48109, USA; Department of Environmental Health Sciences, School of Public Health, University of Michigan, Ann Arbor, Michigan, 48109, USA
| | - Sara R Heras
- Department of Genomic Medicine, GENYO: Centre for Genomics and Oncology (Pfizer-University of Granada and Andalusian Regional Government), PTS Granada, 18016, Spain
| | - José L García-Pérez
- Department of Genomic Medicine, GENYO: Centre for Genomics and Oncology (Pfizer-University of Granada and Andalusian Regional Government), PTS Granada, 18016, Spain; Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine (IGMM), University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Thomas E Wilson
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA; Department of Pathology, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA.
| | - John V Moran
- Department of Human Genetics, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA; Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, 48109, USA.
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24
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Sultana T, van Essen D, Siol O, Bailly-Bechet M, Philippe C, Zine El Aabidine A, Pioger L, Nigumann P, Saccani S, Andrau JC, Gilbert N, Cristofari G. The Landscape of L1 Retrotransposons in the Human Genome Is Shaped by Pre-insertion Sequence Biases and Post-insertion Selection. Mol Cell 2019; 74:555-570.e7. [PMID: 30956044 DOI: 10.1016/j.molcel.2019.02.036] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 01/28/2019] [Accepted: 02/25/2019] [Indexed: 01/10/2023]
Abstract
L1 retrotransposons are transposable elements and major contributors of genetic variation in humans. Where L1 integrates into the genome can directly impact human evolution and disease. Here, we experimentally induced L1 retrotransposition in cells and mapped integration sites at nucleotide resolution. At local scales, L1 integration is mostly restricted by genome sequence biases and the specificity of the L1 machinery. At regional scales, L1 shows a broad capacity for integration into all chromatin states, in contrast to other known mobile genetic elements. However, integration is influenced by the replication timing of target regions, suggesting a link to host DNA replication. The distribution of new L1 integrations differs from those of preexisting L1 copies, which are significantly reshaped by natural selection. Our findings reveal that the L1 machinery has evolved to efficiently target all genomic regions and underline a predominant role for post-integrative processes on the distribution of endogenous L1 elements.
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Affiliation(s)
- Tania Sultana
- Université Côte d'Azur, Inserm, CNRS, IRCAN, Nice, France
| | | | - Oliver Siol
- Institut de Génétique Humaine, University of Montpellier, CNRS, Montpellier, France
| | | | | | - Amal Zine El Aabidine
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Léo Pioger
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Pilvi Nigumann
- Université Côte d'Azur, Inserm, CNRS, IRCAN, Nice, France
| | - Simona Saccani
- Université Côte d'Azur, Inserm, CNRS, IRCAN, Nice, France
| | - Jean-Christophe Andrau
- Institut de Génétique Moléculaire de Montpellier, University of Montpellier, CNRS, Montpellier, France
| | - Nicolas Gilbert
- Institut de Génétique Humaine, University of Montpellier, CNRS, Montpellier, France; Institut de Médecine Régénératrice et de Biothérapie, Inserm U1183, CHU Montpellier, Montpellier, France
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25
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Warkocki Z, Liudkovska V, Gewartowska O, Mroczek S, Dziembowski A. Terminal nucleotidyl transferases (TENTs) in mammalian RNA metabolism. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2018.0162. [PMID: 30397099 PMCID: PMC6232586 DOI: 10.1098/rstb.2018.0162] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2018] [Indexed: 12/15/2022] Open
Abstract
In eukaryotes, almost all RNA species are processed at their 3′ ends and most mRNAs are polyadenylated in the nucleus by canonical poly(A) polymerases. In recent years, several terminal nucleotidyl transferases (TENTs) including non-canonical poly(A) polymerases (ncPAPs) and terminal uridyl transferases (TUTases) have been discovered. In contrast to canonical polymerases, TENTs' functions are more diverse; some, especially TUTases, induce RNA decay while others, such as cytoplasmic ncPAPs, activate translationally dormant deadenylated mRNAs. The mammalian genome encodes 11 different TENTs. This review summarizes the current knowledge about the functions and mechanisms of action of these enzymes. This article is part of the theme issue ‘5′ and 3′ modifications controlling RNA degradation’.
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Affiliation(s)
- Zbigniew Warkocki
- Department of RNA Metabolism, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, Poznan, Poland
| | - Vladyslava Liudkovska
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Olga Gewartowska
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Seweryn Mroczek
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Andrzej Dziembowski
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland .,Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
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26
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Nishiyama E, Ohshima K. Cross-Kingdom Commonality of a Novel Insertion Signature of RTE-Related Short Retroposons. Genome Biol Evol 2018; 10:1471-1483. [PMID: 29850801 PMCID: PMC6007223 DOI: 10.1093/gbe/evy098] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/18/2018] [Indexed: 12/15/2022] Open
Abstract
In multicellular organisms, such as vertebrates and flowering plants, horizontal transfer (HT) of genetic information is thought to be a rare event. However, recent findings unveiled unexpectedly frequent HT of RTE-clade LINEs. To elucidate the molecular footprints of the genomic integration machinery of RTE-related retroposons, the sequence patterns surrounding the insertion sites of plant Au-like SINE families were analyzed in the genomes of a wide variety of flowering plants. A novel and remarkable finding regarding target site duplications (TSDs) for SINEs was they start with thymine approximately one helical pitch (ten nucleotides) downstream of a thymine stretch. This TSD pattern was found in RTE-clade LINEs, which share the 3'-end sequence of these SINEs, in the genome of leguminous plants. These results demonstrably show that Au-like SINEs were mobilized by the enzymatic machinery of RTE-clade LINEs. Further, we discovered the same TSD pattern in animal SINEs from lizard and mammals, in which the RTE-clade LINEs sharing the 3'-end sequence with these animal SINEs showed a distinct TSD pattern. Moreover, a significant correlation was observed between the first nucleotide of TSDs and microsatellite-like sequences found at the 3'-ends of SINEs and LINEs. We propose that RTE-encoded protein could preferentially bind to a DNA region that contains a thymine stretch to cleave a phosphodiester bond downstream of the stretch. Further, determination of cleavage sites and/or efficiency of primer sites for reverse transcription may depend on microsatellite-like repeats in the RNA template. Such a unique mechanism may have enabled retroposons to successfully expand in frontier genomes after HT.
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Affiliation(s)
- Eri Nishiyama
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, Shiga, Japan
| | - Kazuhiko Ohshima
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, Shiga, Japan
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27
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Ariumi Y, Kawano K, Yasuda-Inoue M, Kuroki M, Fukuda H, Siddiqui R, Turelli P, Tateishi S. DNA repair protein Rad18 restricts LINE-1 mobility. Sci Rep 2018; 8:15894. [PMID: 30367120 PMCID: PMC6203705 DOI: 10.1038/s41598-018-34288-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 10/15/2018] [Indexed: 12/18/2022] Open
Abstract
Long interspersed element-1 (LINE-1, L1) is a mobile genetic element comprising about 17% of the human genome. L1 utilizes an endonuclease to insert L1 cDNA into the target genomic DNA, which induces double-strand DNA breaks in the human genome and activates the DNA damage signaling pathway, resulting in the recruitment of DNA-repair proteins. This may facilitate or protect L1 integration into the human genome. Therefore, the host DNA repair machinery has pivotal roles in L1 mobility. In this study, we have, for the first time, demonstrated that the DNA repair protein, Rad18, restricts L1 mobility. Notably, overexpression of Rad18 strongly suppressed L1 retrotransposition as well as L1-mediated Alu retrotransposition. In contrast, L1 retrotransposition was enhanced in Rad18-deficient or knockdown cells. Furthermore, the Rad6 (E2 ubiquitin-conjugated enzyme)-binding domain, but not the Polη-binding domain, was required for the inhibition of L1 retrotransposition, suggesting that the E3 ubiquitin ligase activity of Rad18 is important in regulating L1 mobility. Accordingly, wild-type, but not the mutant Rad18-lacking Rad6-binding domain, bound with L1 ORF1p and sequestered with L1 ORF1p into the Rad18-nuclear foci. Altogether, Rad18 restricts L1 and Alu retrotransposition as a guardian of the human genome against endogenous retroelements.
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Affiliation(s)
- Yasuo Ariumi
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan.
| | - Koudai Kawano
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Mariko Yasuda-Inoue
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Misao Kuroki
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Hiroyuki Fukuda
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Rokeya Siddiqui
- Center for AIDS Research, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
| | - Priscilla Turelli
- School of Life Science, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
| | - Satoshi Tateishi
- Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Chuo-ku, Kumamoto, 860-0811, Japan
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28
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Warkocki Z, Krawczyk PS, Adamska D, Bijata K, Garcia-Perez JL, Dziembowski A. Uridylation by TUT4/7 Restricts Retrotransposition of Human LINE-1s. Cell 2018; 174:1537-1548.e29. [PMID: 30122351 PMCID: PMC6191937 DOI: 10.1016/j.cell.2018.07.022] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 05/27/2018] [Accepted: 07/18/2018] [Indexed: 12/19/2022]
Abstract
LINE-1 retrotransposition is tightly restricted by layers of regulatory control, with epigenetic pathways being the best characterized. Looking at post-transcriptional regulation, we now show that LINE-1 mRNA 3' ends are pervasively uridylated in various human cellular models and in mouse testes. TUT4 and TUT7 uridyltransferases catalyze the modification and function in cooperation with the helicase/RNPase MOV10 to counteract the RNA chaperone activity of the L1-ORF1p retrotransposon protein. Uridylation potently restricts LINE-1 retrotransposition by a multilayer mechanism depending on differential subcellular localization of the uridyltransferases. We propose that uridine residues added by TUT7 in the cytoplasm inhibit initiation of reverse transcription of LINE-1 mRNAs once they are reimported to the nucleus, whereas uridylation by TUT4, which is enriched in cytoplasmic foci, destabilizes mRNAs. These results provide a model for the post-transcriptional restriction of LINE-1, revealing a key physiological role for TUT4/7-mediated uridylation in maintaining genome stability.
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Affiliation(s)
- Zbigniew Warkocki
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland.
| | - Paweł S Krawczyk
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland; Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Dorota Adamska
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland; Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Krystian Bijata
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland; Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Jose L Garcia-Perez
- Department of Genomic Medicine, Centre for Genomics and Oncology (Pfizer-University of Granada and Andalusian Regional Government), PTS Granada, Granada 18016, Spain; Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Andrzej Dziembowski
- Laboratory of RNA Biology and Functional Genomics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland; Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw, Pawinskiego 5a, 02-106 Warsaw, Poland.
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29
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Faulkner GJ, Billon V. L1 retrotransposition in the soma: a field jumping ahead. Mob DNA 2018; 9:22. [PMID: 30002735 PMCID: PMC6035798 DOI: 10.1186/s13100-018-0128-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/27/2018] [Indexed: 12/13/2022] Open
Abstract
Retrotransposons are transposable elements (TEs) capable of "jumping" in germ, embryonic and tumor cells and, as is now clearly established, in the neuronal lineage. Mosaic TE insertions form part of a broader landscape of somatic genome variation and hold significant potential to generate phenotypic diversity, in the brain and elsewhere. At present, the LINE-1 (L1) retrotransposon family appears to be the most active autonomous TE in most mammals, based on experimental data obtained from disease-causing L1 mutations, engineered L1 reporter systems tested in cultured cells and transgenic rodents, and single-cell genomic analyses. However, the biological consequences of almost all somatic L1 insertions identified thus far remain unknown. In this review, we briefly summarize the current state-of-the-art in the field, including estimates of L1 retrotransposition rate in neurons. We bring forward the hypothesis that an extensive subset of retrotransposition-competent L1s may be de-repressed and mobile in the soma but largely inactive in the germline. We discuss recent reports of non-canonical L1-associated sequence variants in the brain and propose that the elevated L1 DNA content reported in several neurological disorders may predominantly comprise accumulated, unintegrated L1 nucleic acids, rather than somatic L1 insertions. Finally, we consider the main objectives and obstacles going forward in elucidating the biological impact of somatic retrotransposition.
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Affiliation(s)
- Geoffrey J. Faulkner
- Mater Research Institute – University of Queensland, TRI Building, Woolloongabba, QLD 4102 Australia
- School of Biomedical Sciences, University of Queensland, Brisbane, QLD 4072 Australia
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072 Australia
| | - Victor Billon
- Queensland Brain Institute, University of Queensland, Brisbane, QLD 4072 Australia
- Biology Department, École Normale Supérieure Paris-Saclay, 61 Avenue du Président Wilson, 94230 Cachan, France
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30
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Spliced integrated retrotransposed element (SpIRE) formation in the human genome. PLoS Biol 2018; 16:e2003067. [PMID: 29505568 PMCID: PMC5860796 DOI: 10.1371/journal.pbio.2003067] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 03/20/2018] [Accepted: 02/14/2018] [Indexed: 12/20/2022] Open
Abstract
Human Long interspersed element-1 (L1) retrotransposons contain an internal RNA polymerase II promoter within their 5′ untranslated region (UTR) and encode two proteins, (ORF1p and ORF2p) required for their mobilization (i.e., retrotransposition). The evolutionary success of L1 relies on the continuous retrotransposition of full-length L1 mRNAs. Previous studies identified functional splice donor (SD), splice acceptor (SA), and polyadenylation sequences in L1 mRNA and provided evidence that a small number of spliced L1 mRNAs retrotransposed in the human genome. Here, we demonstrate that the retrotransposition of intra-5′UTR or 5′UTR/ORF1 spliced L1 mRNAs leads to the generation of spliced integrated retrotransposed elements (SpIREs). We identified a new intra-5′UTR SpIRE that is ten times more abundant than previously identified SpIREs. Functional analyses demonstrated that both intra-5′UTR and 5′UTR/ORF1 SpIREs lack Cis-acting transcription factor binding sites and exhibit reduced promoter activity. The 5′UTR/ORF1 SpIREs also produce nonfunctional ORF1p variants. Finally, we demonstrate that sequence changes within the L1 5′UTR over evolutionary time, which permitted L1 to evade the repressive effects of a host protein, can lead to the generation of new L1 splicing events, which, upon retrotransposition, generates a new SpIRE subfamily. We conclude that splicing inhibits L1 retrotransposition, SpIREs generally represent evolutionary “dead-ends” in the L1 retrotransposition process, mutations within the L1 5′UTR alter L1 splicing dynamics, and that retrotransposition of the resultant spliced transcripts can generate interindividual genomic variation. Long interspersed element-1 (L1) sequences comprise about 17% of the human genome reference sequence. The average human genome contains about 100 active L1s that mobilize throughout the genome by a “copy and paste” process termed retrotransposition. Active L1s encode two proteins (ORF1p and ORF2p). ORF1p and ORF2p preferentially bind to their encoding RNA, forming a ribonucleoprotein particle (RNP). During retrotransposition, the L1 RNP translocates to the nucleus, where the ORF2p endonuclease makes a single-strand nick in target site DNA that exposes a 3′ hydroxyl group in genomic DNA. The 3′ hydroxyl group then is used as a primer by the ORF2p reverse transcriptase to copy the L1 RNA into cDNA, leading to the integration of an L1 copy at a new genomic location. The evolutionary success of L1 requires the faithful retrotransposition of full-length L1 mRNAs; thus, it was surprising to find that a small number of L1 retrotransposition events are derived from spliced L1 mRNAs. By using genetic, biochemical, and computational approaches, we demonstrate that spliced L1 mRNAs can undergo an initial round of retrotransposition, leading to the generation of spliced integrated retrotransposed elements (SpIREs). SpIREs represent about 2% of previously annotated full-length primate-specific L1s in the human genome reference sequence. However, because splicing leads to intra-L1 deletions that remove critical sequences required for L1 expression, SpIREs generally cannot undergo subsequent rounds of retrotransposition and can be considered “dead on arrival” insertions. Our data further highlight how genetic conflict between L1 and its host has influenced L1 expression, L1 retrotransposition, and L1 splicing dynamics over evolutionary time.
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31
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Suarez NA, Macia A, Muotri AR. LINE-1 retrotransposons in healthy and diseased human brain. Dev Neurobiol 2017; 78:434-455. [PMID: 29239145 DOI: 10.1002/dneu.22567] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 12/07/2017] [Accepted: 12/08/2017] [Indexed: 12/12/2022]
Abstract
Long interspersed element-1 (LINE-1 or L1) is a transposable element with the ability to self-mobilize throughout the human genome. The L1 elements found in the human brain is hypothesized to date back 56 million years ago and has survived evolution, currently accounting for 17% of the human genome. L1 retrotransposition has been theorized to contribute to somatic mosaicism. This review focuses on the presence of L1 in the healthy and diseased human brain, such as in autism spectrum disorders. Throughout this exploration, we will discuss the impact L1 has on neurological disorders that can occur throughout the human lifetime. With this, we hope to better understand the complex role of L1 in the human brain development and its implications to human cognition. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 434-455, 2018.
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Affiliation(s)
- Nicole A Suarez
- Department of Pediatrics/Rady Children's Hospital San Diego, University of California San Diego, La Jolla, California, 92093
| | - Angela Macia
- Department of Pediatrics/Rady Children's Hospital San Diego, University of California San Diego, La Jolla, California, 92093
| | - Alysson R Muotri
- Department of Pediatrics/Rady Children's Hospital San Diego, University of California San Diego, La Jolla, California, 92093
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32
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Servant G, Streva VA, Deininger PL. Transcription coupled repair and biased insertion of human retrotransposon L1 in transcribed genes. Mob DNA 2017; 8:18. [PMID: 29225704 PMCID: PMC5717806 DOI: 10.1186/s13100-017-0100-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 11/06/2017] [Indexed: 11/26/2022] Open
Abstract
Background L1 retrotransposons inserted within genes in the human genome show a strong bias against sense orientation with respect to the gene. One suggested explanation for this observation was the possibility that L1 inserted randomly, but that there was negative selection against sense-oriented insertions. However, multiple studies have now found that de novo and polymorphic L1 insertions, which have little opportunity for selection to act, also show the same bias. Results Here we show that the transcription-coupled sub-pathway of nucleotide excision repair does not affect the overall rate of insertion of L1 elements, which is in contrast with the regulation by the global sub-pathway of nucleotide excision repair. The transcription-coupled subpathway does cause a strong bias against insertion in the sense orientation relative to genes. Conclusions This suggests that a major portion of the L1 orientation bias might be generated during the process of insertion through the action of transcription-coupled nucleotide excision repair. Electronic supplementary material The online version of this article (10.1186/s13100-017-0100-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Geraldine Servant
- Tulane University, Tulane Cancer Center and the Department of Epidemiology, 1430 Tulane Ave, New Orleans, LA 70112 USA
| | - Vincent A Streva
- Tulane University, Tulane Cancer Center and the Department of Epidemiology, 1430 Tulane Ave, New Orleans, LA 70112 USA.,Present Address: Division of Infectious Diseases, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Boston, MA 02115 USA
| | - Prescott L Deininger
- Tulane University, Tulane Cancer Center and the Department of Epidemiology, 1430 Tulane Ave, New Orleans, LA 70112 USA.,Tulane Cancer Center, SL66, Tulane University Health Sciences Center, 1430 Tulane Ave., New Orleans, LA 70112 USA
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33
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L1 Mosaicism in Mammals: Extent, Effects, and Evolution. Trends Genet 2017; 33:802-816. [PMID: 28797643 DOI: 10.1016/j.tig.2017.07.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 06/30/2017] [Accepted: 07/14/2017] [Indexed: 10/19/2022]
Abstract
The retrotransposon LINE-1 (long interspersed element 1, L1) is a transposable element that has extensively colonized the mammalian germline. L1 retrotransposition can also occur in somatic cells, causing genomic mosaicism, as well as in cancer. However, the extent of L1-driven mosaicism arising during ontogenesis is unclear. We discuss here recent experimental data which, at a minimum, fully substantiate L1 mosaicism in early embryonic development and neural cells, including post-mitotic neurons. We also consider the possible biological impact of somatic L1 insertions in neurons, the existence of donor L1s that are highly active ('hot') in specific spatiotemporal niches, and the evolutionary selection of donor L1s driving neuronal mosaicism.
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34
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Integration site selection by retroviruses and transposable elements in eukaryotes. Nat Rev Genet 2017; 18:292-308. [PMID: 28286338 DOI: 10.1038/nrg.2017.7] [Citation(s) in RCA: 145] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transposable elements and retroviruses are found in most genomes, can be pathogenic and are widely used as gene-delivery and functional genomics tools. Exploring whether these genetic elements target specific genomic sites for integration and how this preference is achieved is crucial to our understanding of genome evolution, somatic genome plasticity in cancer and ageing, host-parasite interactions and genome engineering applications. High-throughput profiling of integration sites by next-generation sequencing, combined with large-scale genomic data mining and cellular or biochemical approaches, has revealed that the insertions are usually non-random. The DNA sequence, chromatin and nuclear context, and cellular proteins cooperate in guiding integration in eukaryotic genomes, leading to a remarkable diversity of insertion site distribution and evolutionary strategies.
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35
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Involvement of Conserved Amino Acids in the C-Terminal Region of LINE-1 ORF2p in Retrotransposition. Genetics 2017; 205:1139-1149. [PMID: 28100588 DOI: 10.1534/genetics.116.191403] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 12/10/2016] [Indexed: 01/09/2023] Open
Abstract
Long interspersed element 1 (L1) is the only currently active autonomous retroelement in the human genome. Along with the parasitic SVA and short interspersed element Alu, L1 is the source of DNA damage induced by retrotransposition: a copy-and-paste process that has the potential to disrupt gene function and cause human disease. The retrotransposition process is dependent upon the ORF2 protein (ORF2p). However, it is unknown whether most of the protein is important for retrotransposition. In particular, other than the Cys motif, the C terminus of the protein has not been intensely examined in the context of retrotransposition. Using evolutionary analysis and the Alu retrotransposition assay, we sought to identify additional amino acids in the C terminus important for retrotransposition. Here, we demonstrate that Gal4-tagged and untagged C-terminally truncated ORF2p fragments possess residual potential to drive Alu retrotransposition. Using sight-directed mutagenesis we identify that while the Y1180 amino acid is important for ORF2p- and L1-driven Alu retrotransposition, a mutation at this position improves L1 retrotransposition. Even though the mechanism of the contribution of Y1180 to Alu and L1 mobilization remains unknown, experimental evidence rules out its direct involvement in the ability of the ORF2p reverse transcriptase to generate complementary DNA. Additionally, our data support that ORF2p amino acids 1180 and 1250-1262 may be involved in the reported ORF1p-mediated increase in ORF2p-driven Alu retrotransposition.
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Muñoz-Lopez M, Vilar-Astasio R, Tristan-Ramos P, Lopez-Ruiz C, Garcia-Pérez JL. Study of Transposable Elements and Their Genomic Impact. Methods Mol Biol 2016; 1400:1-19. [PMID: 26895043 DOI: 10.1007/978-1-4939-3372-3_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Transposable elements (TEs) have been considered traditionally as junk DNA, i.e., DNA sequences that despite representing a high proportion of genomes had no evident cellular functions. However, over the last decades, it has become undeniable that not only TE-derived DNA sequences have (and had) a fundamental role during genome evolution, but also TEs have important implications in the origin and evolution of many genomic disorders. This concise review provides a brief overview of the different types of TEs that can be found in genomes, as well as a list of techniques and methods used to study their impact and mobilization. Some of these techniques will be covered in detail in this Method Book.
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Affiliation(s)
- Martin Muñoz-Lopez
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain.
| | - Raquel Vilar-Astasio
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain
| | - Pablo Tristan-Ramos
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain
| | - Cesar Lopez-Ruiz
- Department of Human DNA Variability, Pfizer/University of Granada and Andalusian Regional Government Center for Genomics and Oncology (GENYO), Avda Ilustracion 114, PTS Granada, 18016, Granada, Spain
| | - Jose L Garcia-Pérez
- -Genyo (Center for Genomics and Oncological Research), Pfizer/Universidad de Granada/Junta de Andalucia. PTS Granada, Spain-Institute of Genetics and Molecular Medicine (IGMM), University of Edinburgh,, Edinburgh, UK
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37
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Philippe C, Vargas-Landin DB, Doucet AJ, van Essen D, Vera-Otarola J, Kuciak M, Corbin A, Nigumann P, Cristofari G. Activation of individual L1 retrotransposon instances is restricted to cell-type dependent permissive loci. eLife 2016; 5. [PMID: 27016617 PMCID: PMC4866827 DOI: 10.7554/elife.13926] [Citation(s) in RCA: 105] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/25/2016] [Indexed: 12/26/2022] Open
Abstract
LINE-1 (L1) retrotransposons represent approximately one sixth of the human genome, but only the human-specific L1HS-Ta subfamily acts as an endogenous mutagen in modern humans, reshaping both somatic and germline genomes. Due to their high levels of sequence identity and the existence of many polymorphic insertions absent from the reference genome, the transcriptional activation of individual genomic L1HS-Ta copies remains poorly understood. Here we comprehensively mapped fixed and polymorphic L1HS-Ta copies in 12 commonly-used somatic cell lines, and identified transcriptional and epigenetic signatures allowing the unambiguous identification of active L1HS-Ta copies in their genomic context. Strikingly, only a very restricted subset of L1HS-Ta loci - some being polymorphic among individuals - significantly contributes to the bulk of L1 expression, and these loci are differentially regulated among distinct cell lines. Thus, our data support a local model of L1 transcriptional activation in somatic cells, governed by individual-, locus-, and cell-type-specific determinants. DOI:http://dx.doi.org/10.7554/eLife.13926.001 Retrotransposons, also known as jumping genes, have invaded the genomes of most living organisms. These fragments of DNA have the ability to move or copy themselves from one location of a chromosome to another. Depending on where they insert themselves, retrotransposons can modify the sequence of nearby genes, which can alter or even abolish their activity. Although these genetic modifications have contributed significantly to the evolution of different species, retrotransposons can also have detrimental effects; for example, by causing new cases of genetic diseases. Adult human cells have a number of mechanisms that work to keep the activity of retrotransposons at a very low level. However, in many types of cancers retrotransposons escape these defense mechanisms and ‘jump’ actively. This is thought to contribute to the development and spread of cancerous tumors. To understand how jumping genes are mobilized, a fundamental question must be answered: is the high jumping gene activity observed in some cell types a result of activating many copies of the retrotransposons, or only a few of them? This question has been difficult to address because there are more than one hundred copies of retrotransposons that could potentially move in humans, many of which have not even been referenced in the human genome map. Furthermore, each copy is almost identical to another one, making it difficult to discriminate between them. Philippe et al. have now developed an approach that can map where individual retrotransposons are located in the genome of normal and cancerous cells and measure how active these jumping genes are. This revealed that only a very restricted number of them are active in any given cell type. Moreover, different subsets of jumping genes are active in different cell types, and their locations in the genome often do not overlap. Thus, whether jumping genes are activated depends on the cell type and their position in the genome. These results are in contrast to the prevalent view that retrotransposons are activated in a more widespread manner across the genome, at least in cancerous cells. Overall, Philippe et al.’s findings pave the way towards characterizing the chromosome regions in which retrotransposons are frequently activated and understanding how they contribute to cancer and other diseases. DOI:http://dx.doi.org/10.7554/eLife.13926.002
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Affiliation(s)
- Claude Philippe
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France.,FHU OncoAge, University of Nice-Sophia Antipolis, Nice, France
| | - Dulce B Vargas-Landin
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France.,Ecole Normale Supérieure, Paris, France
| | - Aurélien J Doucet
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France.,FHU OncoAge, University of Nice-Sophia Antipolis, Nice, France
| | - Dominic van Essen
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France
| | - Jorge Vera-Otarola
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France
| | - Monika Kuciak
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France.,Ecole Normale Supérieure de Lyon, Lyon, France
| | | | - Pilvi Nigumann
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France
| | - Gaël Cristofari
- INSERM U1081, CNRS UMR 7284, Institute for Research on Cancer and Aging of Nice, Nice, France.,Faculty of Medicine, University of Nice-Sophia Antipolis, Nice, France.,FHU OncoAge, University of Nice-Sophia Antipolis, Nice, France
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Abstract
Transposable elements have had a profound impact on the structure and function of mammalian genomes. The retrotransposon Long INterspersed Element-1 (LINE-1 or L1), by virtue of its replicative mobilization mechanism, comprises ∼17% of the human genome. Although the vast majority of human LINE-1 sequences are inactive molecular fossils, an estimated 80-100 copies per individual retain the ability to mobilize by a process termed retrotransposition. Indeed, LINE-1 is the only active, autonomous retrotransposon in humans and its retrotransposition continues to generate both intra-individual and inter-individual genetic diversity. Here, we briefly review the types of transposable elements that reside in mammalian genomes. We will focus our discussion on LINE-1 retrotransposons and the non-autonomous Short INterspersed Elements (SINEs) that rely on the proteins encoded by LINE-1 for their mobilization. We review cases where LINE-1-mediated retrotransposition events have resulted in genetic disease and discuss how the characterization of these mutagenic insertions led to the identification of retrotransposition-competent LINE-1s in the human and mouse genomes. We then discuss how the integration of molecular genetic, biochemical, and modern genomic technologies have yielded insight into the mechanism of LINE-1 retrotransposition, the impact of LINE-1-mediated retrotransposition events on mammalian genomes, and the host cellular mechanisms that protect the genome from unabated LINE-1-mediated retrotransposition events. Throughout this review, we highlight unanswered questions in LINE-1 biology that provide exciting opportunities for future research. Clearly, much has been learned about LINE-1 and SINE biology since the publication of Mobile DNA II thirteen years ago. Future studies should continue to yield exciting discoveries about how these retrotransposons contribute to genetic diversity in mammalian genomes.
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Pizarro JG, Cristofari G. Post-Transcriptional Control of LINE-1 Retrotransposition by Cellular Host Factors in Somatic Cells. Front Cell Dev Biol 2016; 4:14. [PMID: 27014690 PMCID: PMC4782638 DOI: 10.3389/fcell.2016.00014] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 02/18/2016] [Indexed: 12/13/2022] Open
Abstract
Long INterspersed Element-1 (LINE-1 or L1) retrotransposons form the only autonomously active family of transposable elements in humans. They are expressed and mobile in the germline, in embryonic stem cells and in the early embryo, but are silenced in most somatic tissues. Consistently, they play an important role in individual genome variations through insertional mutagenesis and sequence transduction, which occasionally lead to novel genetic diseases. In addition, they are reactivated in nearly half of the human epithelial cancers, contributing to tumor genome dynamics. The L1 element codes for two proteins, ORF1p and ORF2p, which are essential for its mobility. ORF1p is an RNA-binding protein with nucleic acid chaperone activity and ORF2p possesses endonuclease and reverse transcriptase activities. These proteins and the L1 RNA assemble into a ribonucleoprotein particle (L1 RNP), considered as the core of the retrotransposition machinery. The L1 RNP mediates the synthesis of new L1 copies upon cleavage of the target DNA and reverse transcription of the L1 RNA at the target site. The L1 element takes benefit of cellular host factors to complete its life cycle, however several cellular pathways also limit the cellular accumulation of L1 RNPs and their deleterious activities. Here, we review the known cellular host factors and pathways that regulate positively or negatively L1 retrotransposition at post-transcriptional level, in particular by interacting with the L1 machinery or L1 replication intermediates; and how they contribute to control L1 activity in somatic cells.
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Affiliation(s)
- Javier G Pizarro
- Institute for Research on Cancer and Aging of Nice (IRCAN), Faculty of Medicine, CNRS UMR7284, INSERM U1081, University of Nice Sophia Antipolis Nice, France
| | - Gaël Cristofari
- Institute for Research on Cancer and Aging of Nice (IRCAN), Faculty of Medicine, CNRS UMR7284, INSERM U1081, University of Nice Sophia Antipolis Nice, France
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40
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Viollet S, Doucet AJ, Cristofari G. Biochemical Approaches to Study LINE-1 Reverse Transcriptase Activity In Vitro. Methods Mol Biol 2016; 1400:357-76. [PMID: 26895064 DOI: 10.1007/978-1-4939-3372-3_22] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In vitro reverse transcriptase assays have been developed to monitor the presence and activity of ORF2p, an essential protein product of the LINE-1 retrotransposon (L1), in cellular fractions. We describe methods for expression and isolation of L1 ribonucleoprotein particles, and identification of ORF2p reverse transcriptase activity. Two independent methods are described: L1 element amplification protocol (LEAP) and direct L1 extension assay (DLEA). The first method involves cDNA synthesis by primer extension using dNTPs followed by a step of PCR amplification. The second method involves primer extension by incorporation of radiolabeled dTMPs followed by dot-blot or gel separation detection. Finally, we discuss the output and benefits of the two methods.
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Affiliation(s)
- Sébastien Viollet
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, 06100, France
- CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, 06100, France
- Faculty of Medicine, University of Nice-Sophia-Antipolis, Nice, 06100, France
| | - Aurélien J Doucet
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, 06100, France
- CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, 06100, France
- Faculty of Medicine, University of Nice-Sophia-Antipolis, Nice, 06100, France
| | - Gaël Cristofari
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, 06100, France.
- CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), Nice, 06100, France.
- Faculty of Medicine, University of Nice-Sophia-Antipolis, Nice, 06100, France.
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41
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Kopera HC, Flasch DA, Nakamura M, Miyoshi T, Doucet AJ, Moran JV. LEAP: L1 Element Amplification Protocol. Methods Mol Biol 2016; 1400:339-55. [PMID: 26895063 DOI: 10.1007/978-1-4939-3372-3_21] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Long INterspersed Element-1 (LINE-1 or L1) retrotransposons encode two proteins (ORF1p and ORF2p) that are required for retrotransposition. The L1 element amplification protocol (LEAP) assays the ability of L1 ORF2p to reverse transcribe L1 RNA in vitro. Ultracentrifugation or immunoprecipitation is used to isolate L1 ribonucleoprotein particle (RNP) complexes from cultured human cells transfected with an engineered L1 expression construct. The isolated RNPs are incubated with an oligonucleotide that contains a unique sequence at its 5' end and a thymidine-rich sequence at its 3' end. The addition of dNTPs to the reaction allows L1 ORF2p bound to L1 RNA to generate L1 cDNA. The resultant L1 cDNAs then are amplified using polymerase chain reaction (PCR) and the products are visualized by gel electrophoresis. Sequencing the resultant PCR products then allows product verification. The LEAP assay has been instrumental in determining how mutations in L1 ORF1p and ORF2p affect L1 reverse transcriptase (RT) activity. Furthermore, the LEAP assay has revealed that the L1 ORF2p RT can extend a DNA primer with mismatched 3' terminal bases when it is annealed to an L1 RNA template. As the LINE-1 biology field gravitates toward studying cellular proteins that regulate LINE-1, molecular genetic and biochemical approaches such as LEAP, in conjunction with the LINE-1-cultured cell retrotransposition assay, are essential to dissect the molecular mechanism of L1 retrotransposition.
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Affiliation(s)
- Huira C Kopera
- Department of Human Genetics, University of Michigan Medical School, 1241 E. Catherine Street, Ann Arbor, MI, 48109, USA.
| | - Diane A Flasch
- Department of Human Genetics, University of Michigan Medical School, 1241 E. Catherine Street, Ann Arbor, MI, 48109, USA
| | - Mitsuhiro Nakamura
- Department of Human Genetics, University of Michigan Medical School, 1241 E. Catherine Street, Ann Arbor, MI, 48109, USA
| | - Tomoichiro Miyoshi
- Department of Human Genetics, University of Michigan Medical School, 1241 E. Catherine Street, Ann Arbor, MI, 48109, USA
| | - Aurélien J Doucet
- Department of Human Genetics, University of Michigan Medical School, 1241 E. Catherine Street, Ann Arbor, MI, 48109, USA
| | - John V Moran
- Department of Human Genetics, University of Michigan Medical School, 1241 E. Catherine Street, Ann Arbor, MI, 48109, USA. .,Cellular and Molecular Biology Program, University of Michigan Medical School, Ann Arbor, MI, USA. .,Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA. .,Howard Hughes Medical Institute, Chevy Chase, MD, USA.
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A 3' Poly(A) Tract Is Required for LINE-1 Retrotransposition. Mol Cell 2015; 60:728-741. [PMID: 26585388 DOI: 10.1016/j.molcel.2015.10.012] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/30/2015] [Accepted: 10/06/2015] [Indexed: 11/22/2022]
Abstract
L1 retrotransposons express proteins (ORF1p and ORF2p) that preferentially mobilize their encoding RNA in cis, but they also can mobilize Alu RNA and, more rarely, cellular mRNAs in trans. Although these RNAs differ in sequence, each ends in a 3' polyadenosine (poly(A)) tract. Here, we replace the L1 polyadenylation signal with sequences derived from a non-polyadenylated long non-coding RNA (MALAT1), which can form a stabilizing triple helix at the 3' end of an RNA. L1/MALAT RNAs accumulate in cells, lack poly(A) tails, and are translated; however, they cannot retrotranspose in cis. Remarkably, the addition of a 16 or 40 base poly(A) tract downstream of the L1/MALAT triple helix restores retrotransposition in cis. The presence of a poly(A) tract also allows ORF2p to bind and mobilize RNAs in trans. Thus, a 3' poly(A) tract is critical for the retrotransposition of sequences that comprise approximately one billion base pairs of human DNA.
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43
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piRNA involvement in genome stability and human cancer. J Hematol Oncol 2015; 8:38. [PMID: 25895683 PMCID: PMC4412036 DOI: 10.1186/s13045-015-0133-5] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/31/2015] [Indexed: 12/16/2022] Open
Abstract
PIWI-interacting RNAs (piRNAs) are a large family of small, single-stranded, non-coding RNAs present throughout the animal kingdom. They form complexes with several members of the PIWI clade of Argonaute proteins and carry out regulatory functions. Their best established biological role is the inhibition of transposon mobilization, which they enforce both at the transcriptional level, through regulation of heterochromatin formation, and by promoting transcript degradation. In this capacity, piRNAs and PIWI proteins are at the heart of the germline cells’ efforts to preserve genome integrity. Additional regulatory roles of piRNAs and PIWI proteins in gene expression are becoming increasingly apparent. PIWI proteins and piRNAs are often detected in human cancers deriving from germline cells as well as somatic tissues. Their detection in cancer correlates with poorer clinical outcomes, suggesting that they play a functional role in the biology of cancer. Nonetheless, the currently available information, while highly suggestive, is still not sufficient to entirely discriminate between a ‘passenger’ role for the ectopic expression of piRNAs and PIWI proteins in cancer from a ‘driver’ role in the pathogenesis of these diseases. In this article, we review some of the key available evidence for the role of piRNAs and PIWI in human cancer and discuss ways in which our understanding of their functions may be improved.
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44
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Doucet AJ, Droc G, Siol O, Audoux J, Gilbert N. U6 snRNA Pseudogenes: Markers of Retrotransposition Dynamics in Mammals. Mol Biol Evol 2015; 32:1815-32. [PMID: 25761766 PMCID: PMC4476161 DOI: 10.1093/molbev/msv062] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Transposable elements comprise more than 45% of the human genome and long interspersed nuclear element 1 (LINE-1 or L1) is the only autonomous mobile element remaining active. Since its identification, it has been proposed that L1 contributes to the mobilization and amplification of other cellular RNAs and more recently, experimental demonstrations of this function has been described for many transcripts such as Alu, a nonautonomous mobile element, cellular mRNAs, or small noncoding RNAs. Detailed examination of the mobilization of various cellular RNAs revealed distinct pathways by which they could be recruited during retrotransposition; template choice or template switching. Here, by analyzing genomic structures and retrotransposition signatures associated with small nuclear RNA (snRNA) sequences, we identified distinct recruiting steps during the L1 retrotransposition cycle for the formation of snRNA-processed pseudogenes. Interestingly, some of the identified recruiting steps take place in the nucleus. Moreover, after comparison to other vertebrate genomes, we established that snRNA amplification by template switching is common to many LINE families from several LINE clades. Finally, we suggest that U6 snRNA copies can serve as markers of L1 retrotransposition dynamics in mammalian genomes.
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Affiliation(s)
- Aurélien J Doucet
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Institute for Research on Cancer and Aging, Nice (IRCAN), INSERM, U1081, CNRS UMR 7284, Nice, France
| | - Gaëtan Droc
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad), UMR AGAP, Montpellier, France
| | - Oliver Siol
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France
| | - Jérôme Audoux
- Institute for Regenerative Medicine and Biotherapy, INSERM, U1183, Montpellier, France
| | - Nicolas Gilbert
- Institut de Génétique Humaine, CNRS, UPR 1142, Montpellier, France Institute for Regenerative Medicine and Biotherapy, INSERM, U1183, Montpellier, France
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45
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Affiliation(s)
- Sandra R. Richardson
- Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba QLD 4102, Australia;
| | - Santiago Morell
- Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba QLD 4102, Australia;
| | - Geoffrey J. Faulkner
- Mater Research Institute, The University of Queensland, Translational Research Institute, Woolloongabba QLD 4102, Australia;
- School of Biomedical Sciences, The University of Queensland, Brisbane QLD 4072, Australia
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46
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Mir AA, Philippe C, Cristofari G. euL1db: the European database of L1HS retrotransposon insertions in humans. Nucleic Acids Res 2014; 43:D43-7. [PMID: 25352549 PMCID: PMC4383891 DOI: 10.1093/nar/gku1043] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Retrotransposons account for almost half of our genome. They are mobile genetics elements—also known as jumping genes—but only the L1HS subfamily of Long Interspersed Nuclear Elements (LINEs) has retained the ability to jump autonomously in modern humans. Their mobilization in germline—but also some somatic tissues—contributes to human genetic diversity and to diseases, such as cancer. Here, we present euL1db, the European database of L1HS retrotransposon insertions in humans (available at http://euL1db.unice.fr). euL1db provides a curated and comprehensive summary of L1HS insertion polymorphisms identified in healthy or pathological human samples and published in peer-reviewed journals. A key feature of euL1db is its sample-wise organization. Hence L1HS insertion polymorphisms are connected to samples, individuals, families and clinical conditions. The current version of euL1db centralizes results obtained in 32 studies. It contains >900 samples, >140 000 sample-wise insertions and almost 9000 distinct merged insertions. euL1db will help understanding the link between L1 retrotransposon insertion polymorphisms and phenotype or disease.
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Affiliation(s)
- Ashfaq A Mir
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France Faculty of Medicine, Institute for Research on Cancer and Aging of Nice (IRCAN), University of Nice-Sophia-Antipolis, F-06100 Nice, France
| | - Claude Philippe
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France Faculty of Medicine, Institute for Research on Cancer and Aging of Nice (IRCAN), University of Nice-Sophia-Antipolis, F-06100 Nice, France
| | - Gaël Cristofari
- INSERM, U1081, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France CNRS, UMR 7284, Institute for Research on Cancer and Aging of Nice (IRCAN), F-06100 Nice, France Faculty of Medicine, Institute for Research on Cancer and Aging of Nice (IRCAN), University of Nice-Sophia-Antipolis, F-06100 Nice, France
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47
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Retrotransposons in pluripotent cells: Impact and new roles in cellular plasticity. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:417-26. [PMID: 25042909 DOI: 10.1016/j.bbagrm.2014.07.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/08/2014] [Accepted: 07/10/2014] [Indexed: 12/27/2022]
Abstract
Transposable Elements are pieces of DNA able to mobilize from one location to another within genomes. Although they constitute more than 50% of the human genome, they have been classified as selfish DNA, with the only mission to spread within genomes and generate more copies of themselves that will ensure their presence over generations. Despite their remarkable prevalence, only a minor group of transposable elements remain active in the human genome and can sporadically be associated with the generation of a genetic disorder due to their ongoing mobility. Most of the transposable elements identified in the human genome corresponded to fixed insertions that no longer move in genomes. As selfish DNA, transposable element insertions accumulate in cell types where genetic information can be passed to the next generation. Indeed, work from different laboratories has demonstrated that the main heritable load of TE accumulation in humans occurs during early embryogenesis. Thus, active transposable elements have a clear impact on our pluripotent genome. However, recent findings suggest that the main proportion of fixed non-mobile transposable elements might also have emerging roles in cellular plasticity. In this concise review, we provide an overview of the impact of currently active transposable elements in our pluripotent genome and further discuss new roles of transposable elements (active or not) in regulating pluripotency. This article is part of a Special Issue entitled: Stress as a fundamental theme in cell plasticity.
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Guidez F. [Retrotransposons: selfish DNA or active epigenetic players in somatic cells?]. Med Sci (Paris) 2014; 30:659-64. [PMID: 25014457 DOI: 10.1051/medsci/20143006016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Transposable elements (TE) represent around 40% of the human genome. They are endogenous mobile DNA sequences able to jump and duplicate in the host genome. TE have long been considered as "junk" DNA but are now believed to be important regulators of gene expression by participating to the establishment of the DNA methylation profile. Recent advances in genome sequencing reveals a higher transposition frequency and TE driven gene expression in somatic cells than previously thought. As TE propagation is deleterious and may be involved in oncogenic mechanisms, host cells have developed silencing mechanisms mainly described in germinal and embryonic cells. However, somatic cells are also proned to TE transposition and use specific mechanisms involving tumor suppressor proteins including p53, Rb and PLZF. These transcription factors specifically target genomic retrotransposon sequences, histone deacetylase and DNA methylase activities, inducing epigenetic modifications related to gene silencing. Thus, these transcription factors negatively regulate TE expression by the formation of DNA methylation profil in somatic cells possibly associated with oncogenic mechanisms.
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Affiliation(s)
- Fabien Guidez
- Inserm UMRS 1131, université Paris Diderot, institut universitaire d'hématologie (IUH), hôpital Saint-Louis, 1, avenue Claude Vellefaux, 75010 Paris, France
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Viollet S, Monot C, Cristofari G. L1 retrotransposition: The snap-velcro model and its consequences. Mob Genet Elements 2014; 4:e28907. [PMID: 24818067 PMCID: PMC4014453 DOI: 10.4161/mge.28907] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/14/2014] [Accepted: 04/15/2014] [Indexed: 12/18/2022] Open
Abstract
LINE-1 (L1) elements are the only active and autonomous transposable elements in humans. The core retrotransposition machinery is a ribonucleoprotein particle (RNP) containing the L1 mRNA, with endonuclease and reverse transcriptase activities. It initiates reverse transcription directly at genomic target sites upon endonuclease cleavage. Recently, using a direct L1 extension assay (DLEA), we systematically tested the ability of native L1 RNPs to extend DNA substrates of various sequences and structures. We deduced from these experiments the general rules guiding the initiation of L1 reverse transcription, referred to as the snap-velcro model. In this model, L1 target choice is not only mediated by the sequence specificity of the endonuclease, but also through base-pairing between the L1 mRNA and the target site, which permits the subsequent L1 reverse transcription step. In addition, L1 reverse transcriptase efficiently primes L1 DNA synthesis only when the 3′ end of the DNA substrate is single-stranded, suggesting so-far unrecognized DNA processing steps at the integration site.
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Affiliation(s)
- Sébastien Viollet
- INSERM; U1081; Institute for Research on Cancer and Aging of Nice (IRCAN); Nice, France ; CNRS; UMR 7284; Institute for Research on Cancer and Aging of Nice (IRCAN); Nice, France ; University of Nice-Sophia Antipolis; Faculty of Medicine; Nice, France
| | - Clément Monot
- INSERM; U1081; Institute for Research on Cancer and Aging of Nice (IRCAN); Nice, France ; CNRS; UMR 7284; Institute for Research on Cancer and Aging of Nice (IRCAN); Nice, France ; University of Nice-Sophia Antipolis; Faculty of Medicine; Nice, France
| | - Gaël Cristofari
- INSERM; U1081; Institute for Research on Cancer and Aging of Nice (IRCAN); Nice, France ; CNRS; UMR 7284; Institute for Research on Cancer and Aging of Nice (IRCAN); Nice, France ; University of Nice-Sophia Antipolis; Faculty of Medicine; Nice, France
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Grandi FC, An W. Non-LTR retrotransposons and microsatellites: Partners in genomic variation. Mob Genet Elements 2013; 3:e25674. [PMID: 24195012 PMCID: PMC3812793 DOI: 10.4161/mge.25674] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 07/07/2013] [Accepted: 07/09/2013] [Indexed: 01/10/2023] Open
Abstract
The human genome is laden with both non-LTR (long-terminal repeat) retrotransposons and microsatellite repeats. Both types of sequences are able to, either actively or passively, mutagenize the genomes of human individuals and are therefore poised to dynamically alter the human genomic landscape across generations. Non-LTR retrotransposons, such as L1 and Alu, are a major source of new microsatellites, which are born both concurrently and subsequently to L1 and Alu integration into the genome. Likewise, the mutation dynamics of microsatellite repeats have a direct impact on the fitness of their non-LTR retrotransposon parent owing to microsatellite expansion and contraction. This review explores the interactions and dynamics between non-LTR retrotransposons and microsatellites in the context of genomic variation and evolution.
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Affiliation(s)
- Fiorella C Grandi
- School of Molecular Biosciences and Center for Reproductive Biology; Washington State University; Pullman, WA USA
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