1
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Shao Z, Hu J, Jandura A, Wilk R, Jachimowicz M, Ma L, Hu C, Sundquist A, Das I, Samuel-Larbi P, Brill JA, Krause HM. Spatially revealed roles for lncRNAs in Drosophila spermatogenesis, Y chromosome function and evolution. Nat Commun 2024; 15:3806. [PMID: 38714658 PMCID: PMC11076287 DOI: 10.1038/s41467-024-47346-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 03/25/2024] [Indexed: 05/10/2024] Open
Abstract
Unlike coding genes, the number of lncRNA genes in organism genomes is relatively proportional to organism complexity. From plants to humans, the tissues with highest numbers and levels of lncRNA gene expression are the male reproductive organs. To learn why, we initiated a genome-wide analysis of Drosophila lncRNA spatial expression patterns in these tissues. The numbers of genes and levels of expression observed greatly exceed those previously reported, due largely to a preponderance of non-polyadenylated transcripts. In stark contrast to coding genes, the highest numbers of lncRNAs expressed are in post-meiotic spermatids. Correlations between expression levels, localization and previously performed genetic analyses indicate high levels of function and requirement. More focused analyses indicate that lncRNAs play major roles in evolution by controlling transposable element activities, Y chromosome gene expression and sperm construction. A new type of lncRNA-based particle found in seminal fluid may also contribute to reproductive outcomes.
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Affiliation(s)
- Zhantao Shao
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
| | - Jack Hu
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
| | - Allison Jandura
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
| | - Ronit Wilk
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
| | - Matthew Jachimowicz
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
| | - Lingfeng Ma
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada
| | - Chun Hu
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
| | - Abby Sundquist
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
| | - Indrani Das
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada
| | | | - Julie A Brill
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.
| | - Henry M Krause
- Donnelly Ctr., 160 College St., University of Toronto, Toronto, ON, Canada.
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.
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2
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Ho S, Theurkauf W, Rice N. piRNA-Guided Transposon Silencing and Response to Stress in Drosophila Germline. Viruses 2024; 16:714. [PMID: 38793595 PMCID: PMC11125864 DOI: 10.3390/v16050714] [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: 03/28/2024] [Revised: 04/23/2024] [Accepted: 04/27/2024] [Indexed: 05/26/2024] Open
Abstract
Transposons are integral genome constituents that can be domesticated for host functions, but they also represent a significant threat to genome stability. Transposon silencing is especially critical in the germline, which is dedicated to transmitting inherited genetic material. The small Piwi-interacting RNAs (piRNAs) have a deeply conserved function in transposon silencing in the germline. piRNA biogenesis and function are particularly well understood in Drosophila melanogaster, but some fundamental mechanisms remain elusive and there is growing evidence that the pathway is regulated in response to genotoxic and environmental stress. Here, we review transposon regulation by piRNAs and the piRNA pathway regulation in response to stress, focusing on the Drosophila female germline.
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Affiliation(s)
- Samantha Ho
- Program in Molecular Medicine, University Campus, University of Massachusetts Chan Medical School, Worcester, MA 01655, USA;
| | | | - Nicholas Rice
- Program in Molecular Medicine, University Campus, University of Massachusetts Chan Medical School, Worcester, MA 01655, USA;
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3
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van Lopik J, Alizada A, Trapotsi MA, Hannon GJ, Bornelöv S, Czech Nicholson B. Unistrand piRNA clusters are an evolutionarily conserved mechanism to suppress endogenous retroviruses across the Drosophila genus. Nat Commun 2023; 14:7337. [PMID: 37957172 PMCID: PMC10643416 DOI: 10.1038/s41467-023-42787-1] [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: 04/04/2023] [Accepted: 10/18/2023] [Indexed: 11/15/2023] Open
Abstract
The PIWI-interacting RNA (piRNA) pathway prevents endogenous genomic parasites, i.e. transposable elements, from damaging the genetic material of animal gonadal cells. Specific regions in the genome, called piRNA clusters, are thought to define each species' piRNA repertoire and therefore its capacity to recognize and silence specific transposon families. The unistrand cluster flamenco (flam) is essential in the somatic compartment of the Drosophila ovary to restrict Gypsy-family transposons from infecting the neighbouring germ cells. Disruption of flam results in transposon de-repression and sterility, yet it remains unknown whether this silencing mechanism is present more widely. Here, we systematically characterise 119 Drosophila species and identify five additional flam-like clusters separated by up to 45 million years of evolution. Small RNA-sequencing validated these as bona-fide unistrand piRNA clusters expressed in somatic cells of the ovary, where they selectively target transposons of the Gypsy family. Together, our study provides compelling evidence of a widely conserved transposon silencing mechanism that co-evolved with virus-like Gypsy-family transposons.
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Affiliation(s)
- Jasper van Lopik
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Azad Alizada
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Maria-Anna Trapotsi
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK
| | - Susanne Bornelöv
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK.
| | - Benjamin Czech Nicholson
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing Centre, Cambridge, CB2 0RE, UK.
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4
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Loubalova Z, Konstantinidou P, Haase AD. Themes and variations on piRNA-guided transposon control. Mob DNA 2023; 14:10. [PMID: 37660099 PMCID: PMC10474768 DOI: 10.1186/s13100-023-00298-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 08/21/2023] [Indexed: 09/04/2023] Open
Abstract
PIWI-interacting RNAs (piRNAs) are responsible for preventing the movement of transposable elements in germ cells and protect the integrity of germline genomes. In this review, we examine the common elements of piRNA-guided silencing as well as the differences observed between species. We have categorized the mechanisms of piRNA biogenesis and function into modules. Individual PIWI proteins combine these modules in various ways to produce unique PIWI-piRNA pathways, which nevertheless possess the ability to perform conserved functions. This modular model incorporates conserved core mechanisms and accommodates variable co-factors. Adaptability is a hallmark of this RNA-based immune system. We believe that considering the differences in germ cell biology and resident transposons in different organisms is essential for placing the variations observed in piRNA biology into context, while still highlighting the conserved themes that underpin this process.
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Affiliation(s)
- Zuzana Loubalova
- National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Parthena Konstantinidou
- National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Astrid D Haase
- National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
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5
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Chakrabarty P, Sen R, Sengupta S. From parasites to partners: exploring the intricacies of host-transposon dynamics and coevolution. Funct Integr Genomics 2023; 23:278. [PMID: 37610667 DOI: 10.1007/s10142-023-01206-w] [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: 06/14/2023] [Revised: 08/01/2023] [Accepted: 08/07/2023] [Indexed: 08/24/2023]
Abstract
Transposable elements, often referred to as "jumping genes," have long been recognized as genomic parasites due to their ability to integrate and disrupt normal gene function and induce extensive genomic alterations, thereby compromising the host's fitness. To counteract this, the host has evolved a plethora of mechanisms to suppress the activity of the transposons. Recent research has unveiled the host-transposon relationships to be nuanced and complex phenomena, resulting in the coevolution of both entities. Transposition increases the mutational rate in the host genome, often triggering physiological pathways such as immune and stress responses. Current gene transfer technologies utilizing transposable elements have potential drawbacks, including off-target integration, induction of mutations, and modifications of cellular machinery, which makes an in-depth understanding of the host-transposon relationship imperative. This review highlights the dynamic interplay between the host and transposable elements, encompassing various factors and components of the cellular machinery. We provide a comprehensive discussion of the strategies employed by transposable elements for their propagation, as well as the mechanisms utilized by the host to mitigate their parasitic effects. Additionally, we present an overview of recent research identifying host proteins that act as facilitators or inhibitors of transposition. We further discuss the evolutionary outcomes resulting from the genetic interactions between the host and the transposable elements. Finally, we pose open questions in this field and suggest potential avenues for future research.
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Affiliation(s)
- Prayas Chakrabarty
- Department of Life Sciences, Presidency University Kolkata, 86/1 College Street, Kolkata, 700073, India
| | - Raneet Sen
- Department of Life Sciences, Presidency University Kolkata, 86/1 College Street, Kolkata, 700073, India
- Institute of Bioorganic Chemistry, Department of RNA Metabolism, Polish Academy of Sciences, Poznan, Poland
| | - Sugopa Sengupta
- Department of Life Sciences, Presidency University Kolkata, 86/1 College Street, Kolkata, 700073, India.
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6
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Signor S, Vedanayagam J, Kim BY, Wierzbicki F, Kofler R, Lai EC. Rapid evolutionary diversification of the flamenco locus across simulans clade Drosophila species. PLoS Genet 2023; 19:e1010914. [PMID: 37643184 PMCID: PMC10495008 DOI: 10.1371/journal.pgen.1010914] [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: 03/07/2023] [Revised: 09/11/2023] [Accepted: 08/09/2023] [Indexed: 08/31/2023] Open
Abstract
Suppression of transposable elements (TEs) is paramount to maintain genomic integrity and organismal fitness. In D. melanogaster, the flamenco locus is a master suppressor of TEs, preventing the mobilization of certain endogenous retrovirus-like TEs from somatic ovarian support cells to the germline. It is transcribed by Pol II as a long (100s of kb), single-stranded, primary transcript, and metabolized into ~24-32 nt Piwi-interacting RNAs (piRNAs) that target active TEs via antisense complementarity. flamenco is thought to operate as a trap, owing to its high content of recent horizontally transferred TEs that are enriched in antisense orientation. Using newly-generated long read genome data, which is critical for accurate assembly of repetitive sequences, we find that flamenco has undergone radical transformations in sequence content and even copy number across simulans clade Drosophilid species. Drosophila simulans flamenco has duplicated and diverged, and neither copy exhibits synteny with D. melanogaster beyond the core promoter. Moreover, flamenco organization is highly variable across D. simulans individuals. Next, we find that D. simulans and D. mauritiana flamenco display signatures of a dual-stranded cluster, with ping-pong signals in the testis and/or embryo. This is accompanied by increased copy numbers of germline TEs, consistent with these regions operating as functional dual-stranded clusters. Overall, the physical and functional diversity of flamenco orthologs is testament to the extremely dynamic consequences of TE arms races on genome organization, not only amongst highly related species, but even amongst individuals.
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Affiliation(s)
- Sarah Signor
- Biological Sciences, North Dakota State University, Fargo, North Dakota, United States of America
| | - Jeffrey Vedanayagam
- Developmental Biology Program, Sloan-Kettering Institute, New York, New York, United States of America
- Department of Neuroscience, Developmental and Regenerative Biology, University of Texas at San Antonio, Texas, United States of America
| | - Bernard Y. Kim
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Filip Wierzbicki
- Institut für Populationsgenetik, Vetmeduni Vienna, Vienna, Austria
- Vienna Graduate School of Population Genetics, Vienna, Austria
| | - Robert Kofler
- Institut für Populationsgenetik, Vetmeduni Vienna, Vienna, Austria
| | - Eric C. Lai
- Developmental Biology Program, Sloan-Kettering Institute, New York, New York, United States of America
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7
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Zhou J, Xie H, Liu J, Huang R, Xiang Y, Tian D, Bian E. PIWI-interacting RNAs: Critical roles and therapeutic targets in cancer. Cancer Lett 2023; 562:216189. [PMID: 37076042 DOI: 10.1016/j.canlet.2023.216189] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 04/02/2023] [Accepted: 04/12/2023] [Indexed: 04/21/2023]
Abstract
P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are a novel class of small regulatory RNAs (approximately 24-31 nucleotides in length) that often bind to members of the PIWI protein family. piRNAs regulate transposons in animal germ cells; piRNAs are also specifically expressed in many human tissues and regulate pivotal signaling pathways. Additionally, the abnormal expression of piRNAs and PIWI proteins has been associated with various malignant tumours, and multiple mechanisms of piRNA-mediated target gene dysregulation are involved in tumourigenesis and progression, suggesting that they have the potential to serve as new biomarkers and therapeutic targets for tumours. However, the functions and potential mechanisms of action of piRNAs in cancer have not yet been elucidated. This review summarises the current findings on the biogenesis, function, and mechanisms of piRNAs and PIWI proteins in cancer. We also discuss the clinical significance of piRNAs as diagnostic or prognostic biomarkers and therapeutic tools for cancer. Finally, we present some critical questions regarding piRNA research that need to be addressed to provide insight into the future development of the field.
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Affiliation(s)
- Jialin Zhou
- Department of Clinical Medicine, The Second School of Clinical Medical, Anhui Medical University, Hefei, China
| | - Han Xie
- Department of Orthopaedics, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, Anhui Province, 230601, China; Institute of Orthopaedics, Research Center for Translational Medicine, The Second Hospital of Anhui Medical University, Anhui Medical University, Hefei, 230601, China
| | - Jun Liu
- Department of Orthopaedics, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, Anhui Province, 230601, China; Institute of Orthopaedics, Research Center for Translational Medicine, The Second Hospital of Anhui Medical University, Anhui Medical University, Hefei, 230601, China
| | - Ruixiang Huang
- Department of Orthopaedics, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, Anhui Province, 230601, China; Institute of Orthopaedics, Research Center for Translational Medicine, The Second Hospital of Anhui Medical University, Anhui Medical University, Hefei, 230601, China
| | - Yufei Xiang
- Department of Orthopaedics, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, Anhui Province, 230601, China; Institute of Orthopaedics, Research Center for Translational Medicine, The Second Hospital of Anhui Medical University, Anhui Medical University, Hefei, 230601, China
| | - Dasheng Tian
- Department of Orthopaedics, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, Anhui Province, 230601, China; Institute of Orthopaedics, Research Center for Translational Medicine, The Second Hospital of Anhui Medical University, Anhui Medical University, Hefei, 230601, China.
| | - Erbao Bian
- Department of Orthopaedics, The Second Affiliated Hospital of Anhui Medical University, 678 Fu Rong Road, Hefei, Anhui Province, 230601, China; Institute of Orthopaedics, Research Center for Translational Medicine, The Second Hospital of Anhui Medical University, Anhui Medical University, Hefei, 230601, China.
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8
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Retrotransposons Down- and Up-Regulation in Aging Somatic Tissues. Cells 2021; 11:cells11010079. [PMID: 35011640 PMCID: PMC8750722 DOI: 10.3390/cells11010079] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/22/2021] [Accepted: 12/26/2021] [Indexed: 01/19/2023] Open
Abstract
The transposon theory of aging hypothesizes the activation of transposable elements (TEs) in somatic tissues with age, leading to a shortening of the lifespan. It is thought that TE activation in aging produces an increase in DNA double-strand breaks, contributing to genome instability and promoting the activation of inflammatory responses. To investigate how TE regulation changes in somatic tissues during aging, we analyzed the expression of some TEs, as well as a source of small RNAs that specifically silence the analyzed TEs; the Drosophila cluster named flamenco. We found significant variations in the expression levels of all the analyzed TEs during aging, with a trend toward reduction in middle-aged adults and reactivation in older individuals that suggests dynamic regulation during the lifespan.
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9
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Baptista B, Riscado M, Queiroz J, Pichon C, Sousa F. Non-coding RNAs: Emerging from the discovery to therapeutic applications. Biochem Pharmacol 2021. [DOI: 10.1016/j.bcp.2021.114469 order by 22025--] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
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10
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Munafò M, Lawless VR, Passera A, MacMillan S, Bornelöv S, Haussmann IU, Soller M, Hannon GJ, Czech B. Channel nuclear pore complex subunits are required for transposon silencing in Drosophila. eLife 2021; 10:e66321. [PMID: 33856346 PMCID: PMC8133776 DOI: 10.7554/elife.66321] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 04/14/2021] [Indexed: 12/21/2022] Open
Abstract
The nuclear pore complex (NPC) is the principal gateway between nucleus and cytoplasm that enables exchange of macromolecular cargo. Composed of multiple copies of ~30 different nucleoporins (Nups), the NPC acts as a selective portal, interacting with factors which individually license passage of specific cargo classes. Here we show that two Nups of the inner channel, Nup54 and Nup58, are essential for transposon silencing via the PIWI-interacting RNA (piRNA) pathway in the Drosophila ovary. In ovarian follicle cells, loss of Nup54 and Nup58 results in compromised piRNA biogenesis exclusively from the flamenco locus, whereas knockdowns of other NPC subunits have widespread consequences. This provides evidence that some Nups can acquire specialised roles in tissue-specific contexts. Our findings consolidate the idea that the NPC has functions beyond simply constituting a barrier to nuclear/cytoplasmic exchange as genomic loci subjected to strong selective pressure can exploit NPC subunits to facilitate their expression.
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Affiliation(s)
- Marzia Munafò
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Victoria R Lawless
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Alessandro Passera
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Serena MacMillan
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Susanne Bornelöv
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Irmgard U Haussmann
- Department of Life Science, Faculty of Health, Education and Life Sciences, Birmingham City UniversityBirminghamUnited Kingdom
- School of Biosciences, College of Life and Environmental Sciences, University of BirminghamBirminghamUnited Kingdom
| | - Matthias Soller
- School of Biosciences, College of Life and Environmental Sciences, University of BirminghamBirminghamUnited Kingdom
- Birmingham Center for Genome Biology, University of BirminghamBirminghamUnited Kingdom
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Benjamin Czech
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
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11
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Baptista B, Riscado M, Queiroz JA, Pichon C, Sousa F. Non-coding RNAs: Emerging from the discovery to therapeutic applications. Biochem Pharmacol 2021; 189:114469. [PMID: 33577888 DOI: 10.1016/j.bcp.2021.114469] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/03/2021] [Accepted: 02/04/2021] [Indexed: 02/06/2023]
Abstract
The knowledge about non-coding RNAs (ncRNAs) is rapidly increasing with new data continuously emerging, regarding their diverse types, applications, and roles. Particular attention has been given to ncRNA with regulatory functions, which may have a critical role both in biological and pathological conditions. As a result of the diversity of ncRNAs and their ubiquitous involvement in several biologic processes, ncRNA started to be considered in the biomedical field, with immense potential to be exploited either as biomarkers or as therapeutic agents in certain pathologies. Indeed, ncRNA-based therapeutics have been proposed in many disorders and some even reached clinical trials. However, to prepare an RNA product suitable for pharmacological applications, certain criteria must be fulfilled, and it has to be guaranteed RNA purity, stability, and bioactivity. So, in this review, the different types of ncRNAs are identified and characterized, by describing their biogenesis, functions, and applications. A perspective on the main challenges and innovative approaches for the future and broad therapeutic application of RNA is also presented.
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Affiliation(s)
- B Baptista
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - M Riscado
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - J A Queiroz
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - C Pichon
- Centre de Biophysique Moléculaire (CBM), UPR 4301 CNRS & University of Orléans Orléans, France
| | - F Sousa
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal.
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12
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Mérel V, Boulesteix M, Fablet M, Vieira C. Transposable elements in Drosophila. Mob DNA 2020; 11:23. [PMID: 32636946 PMCID: PMC7334843 DOI: 10.1186/s13100-020-00213-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 04/14/2020] [Indexed: 12/25/2022] Open
Abstract
Drosophila has been studied as a biological model for many years and many discoveries in biology rely on this species. Research on transposable elements (TEs) is not an exception. Drosophila has contributed significantly to our knowledge on the mechanisms of transposition and their regulation, but above all, it was one of the first organisms on which genetic and genomic studies of populations were done. In this review article, in a very broad way, we will approach the TEs of Drosophila with a historical hindsight as well as recent discoveries in the field.
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Affiliation(s)
- Vincent Mérel
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69622 Villeurbanne, France
| | - Matthieu Boulesteix
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69622 Villeurbanne, France
| | - Marie Fablet
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69622 Villeurbanne, France
| | - Cristina Vieira
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR 5558, F-69622 Villeurbanne, France
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13
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Wu PH, Fu Y, Cecchini K, Özata DM, Arif A, Yu T, Colpan C, Gainetdinov I, Weng Z, Zamore PD. The evolutionarily conserved piRNA-producing locus pi6 is required for male mouse fertility. Nat Genet 2020; 52:728-739. [PMID: 32601478 PMCID: PMC7383350 DOI: 10.1038/s41588-020-0657-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Accepted: 05/29/2020] [Indexed: 12/16/2022]
Abstract
Pachytene PIWI-interacting RNAs (piRNAs), which comprise >80% of small RNAs in the adult mouse testis, have been proposed to bind and regulate target RNAs like microRNAs, cleave targets like short interfering RNAs or lack biological function altogether. Although piRNA pathway protein mutants are male sterile, no biological function has been identified for any mammalian piRNA-producing locus. Here, we report that males lacking piRNAs from a conserved mouse pachytene piRNA locus on chromosome 6 (pi6) produce sperm with defects in capacitation and egg fertilization. Moreover, heterozygous embryos sired by pi6-/- fathers show reduced viability in utero. Molecular analyses suggest that pi6 piRNAs repress gene expression by cleaving messenger RNAs encoding proteins required for sperm function. pi6 also participates in a network of piRNA-piRNA precursor interactions that initiate piRNA production from a second piRNA locus on chromosome 10, as well as pi6 itself. Our data establish a direct role for pachytene piRNAs in spermiogenesis and embryo viability.
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Affiliation(s)
- Pei-Hsuan Wu
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA.
| | - Yu Fu
- Bioinformatics Program, Boston University, Boston, MA, USA.,Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA.,Oncology Drug Discovery Unit, Takeda Pharmaceuticals, Cambridge, MA, USA
| | - Katharine Cecchini
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Deniz M Özata
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Amena Arif
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Tianxiong Yu
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA.,School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Cansu Colpan
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ildar Gainetdinov
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA. .,Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA.
| | - Phillip D Zamore
- Howard Hughes Medical Institute and RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA.
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14
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Kukushkina IV, Makhnovskii PA, Nefedova LN, Balakireva EA, Romanova NI, Kuzmin IV, Lavrenov AR, Kim AI. A Study of the Fertility of a Drosophila melanogaster MS Strain with Impaired Transposition Control of the gypsy Mobile Element. Mol Biol 2020. [DOI: 10.1134/s0026893320030097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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15
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Yamashiro H, Negishi M, Kinoshita T, Ishizu H, Ohtani H, Siomi MC. Armitage determines Piwi-piRISC processing from precursor formation and quality control to inter-organelle translocation. EMBO Rep 2020; 21:e48769. [PMID: 31833223 PMCID: PMC7001504 DOI: 10.15252/embr.201948769] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 11/16/2019] [Accepted: 11/18/2019] [Indexed: 01/06/2023] Open
Abstract
Piwi and piRNA form the piRNA-induced silencing complex (piRISC) to repress transposons. In the current model, Armitage (Armi) brings the Piwi-piRISC precursor (pre-piRISC) to mitochondria, where Zucchini-dependent piRISC maturation occurs. Here, we show that Armi is necessary for Piwi-pre-piRISC formation at Yb bodies and that Armi triggers the exit of Piwi-pre-piRISC from Yb bodies and the translocation to mitochondria. Piwi-pre-piRISC resist leaving Yb bodies until Armi binds Piwi-pre-piRISC through the piRNA precursors. The lack of the Armi N-terminus also blocks the Piwi-pre-piRISC exit from Yb bodies. Thus, Armi determines Piwi-piRISC processing, in a multilayered manner, from precursor formation and quality control to inter-organelle translocation for maturation.
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Affiliation(s)
- Haruna Yamashiro
- Department of Biological SciencesGraduate School of ScienceThe University of TokyoTokyoJapan
| | - Mayu Negishi
- Department of Biological SciencesGraduate School of ScienceThe University of TokyoTokyoJapan
| | - Tatsuki Kinoshita
- Department of Biological SciencesGraduate School of ScienceThe University of TokyoTokyoJapan
| | - Hirotsugu Ishizu
- Department of Molecular BiologyKeio University School of MedicineTokyoJapan
| | - Hitoshi Ohtani
- Department of Molecular BiologyKeio University School of MedicineTokyoJapan
- Present address:
Van Andel Research InstituteGrand RapidsMIUSA
| | - Mikiko C Siomi
- Department of Biological SciencesGraduate School of ScienceThe University of TokyoTokyoJapan
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16
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Abstract
In mammals and invertebrates, the proliferation of an invading transposable element (TE) is thought to be stopped by an insertion into a piRNA cluster. Here, we explore the dynamics of TE invasions under this trap model using computer simulations. We found that piRNA clusters confer a substantial benefit, effectively preventing extinction of host populations from a proliferation of deleterious TEs. TE invasions consist of three distinct phases: first, the TE amplifies within the population, next TE proliferation is stopped by segregating cluster insertions, and finally the TE is inactivated by fixation of a cluster insertion. Suppression by segregating cluster insertions is unstable and bursts of TE activity may yet occur. The transposition rate and the population size mostly influence the length of the phases but not the amount of TEs accumulating during an invasion. Solely, the size of piRNA clusters was identified as a major factor influencing TE abundance. We found that a single nonrecombining cluster is more efficient in stopping invasions than clusters distributed over several chromosomes. Recombination among cluster sites makes it necessary that each diploid carries, on the average, four cluster insertions to stop an invasion. Surprisingly, negative selection in a model with piRNA clusters can lead to a novel equilibrium state, where TE copy numbers remain stable despite only some individuals in a population carrying a cluster insertion. In Drosophila melanogaster, the trap model accounts for the abundance of TEs produced in the germline but fails to predict the abundance of TEs produced in the soma.
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Affiliation(s)
- Robert Kofler
- Institut für Populationsgenetik, Vetmeduni Vienna, Wien, Austria
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17
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Sokolova OA, Mikhaleva EA, Kharitonov SL, Abramov YA, Gvozdev VA, Klenov MS. Special vulnerability of somatic niche cells to transposable element activation in Drosophila larval ovaries. Sci Rep 2020; 10:1076. [PMID: 31974416 PMCID: PMC6978372 DOI: 10.1038/s41598-020-57901-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 01/07/2020] [Indexed: 01/09/2023] Open
Abstract
In the Drosophila ovary, somatic escort cells (ECs) form a niche that promotes differentiation of germline stem cell (GSC) progeny. The piRNA (Piwi-interacting RNA) pathway, which represses transposable elements (TEs), is required in ECs to prevent the accumulation of undifferentiated germ cells (germline tumor phenotype). The soma-specific piRNA cluster flamenco (flam) produces a substantial part of somatic piRNAs. Here, we characterized the biological effects of somatic TE activation on germ cell differentiation in flam mutants. We revealed that the choice between normal and tumorous phenotypes of flam mutant ovaries depends on the number of persisting ECs, which is determined at the larval stage. Accordingly, we found much more frequent DNA breaks in somatic cells of flam larval ovaries than in adult ECs. The absence of Chk2 or ATM checkpoint kinases dramatically enhanced oogenesis defects of flam mutants, in contrast to the germline TE-induced defects that are known to be mostly suppressed by сhk2 mutation. These results demonstrate a crucial role of checkpoint kinases in protecting niche cells against deleterious TE activation and suggest substantial differences between DNA damage responses in ovarian somatic and germ cells.
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Affiliation(s)
- Olesya A Sokolova
- Department of Molecular Genetics of the Cell, Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Sq., 123182, Moscow, Russian Federation
| | - Elena A Mikhaleva
- Department of Molecular Genetics of the Cell, Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Sq., 123182, Moscow, Russian Federation
| | - Sergey L Kharitonov
- Department of Molecular Genetics of the Cell, Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Sq., 123182, Moscow, Russian Federation.,Laboratory of Postgenomic Research, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilova St., 119991, Moscow, Russian Federation
| | - Yuri A Abramov
- Department of Molecular Genetics of the Cell, Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Sq., 123182, Moscow, Russian Federation
| | - Vladimir A Gvozdev
- Department of Molecular Genetics of the Cell, Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Sq., 123182, Moscow, Russian Federation
| | - Mikhail S Klenov
- Department of Molecular Genetics of the Cell, Institute of Molecular Genetics, Russian Academy of Sciences, 2 Kurchatov Sq., 123182, Moscow, Russian Federation.
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18
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Assembly and Function of Gonad-Specific Non-Membranous Organelles in Drosophila piRNA Biogenesis. Noncoding RNA 2019; 5:ncrna5040052. [PMID: 31698692 PMCID: PMC6958439 DOI: 10.3390/ncrna5040052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/29/2019] [Accepted: 11/04/2019] [Indexed: 12/16/2022] Open
Abstract
PIWI-interacting RNAs (piRNAs) are small non-coding RNAs that repress transposons in animal germlines. This protects the genome from the invasive DNA elements. piRNA pathway failures lead to DNA damage, gonadal development defects, and infertility. Thus, the piRNA pathway is indispensable for the continuation of animal life. piRNA-mediated transposon silencing occurs in both the nucleus and cytoplasm while piRNA biogenesis is a solely cytoplasmic event. piRNA production requires a number of proteins, the majority of which localize to non-membranous organelles that specifically appear in the gonads. Other piRNA factors are localized on outer mitochondrial membranes. In situ RNA hybridization experiments show that piRNA precursors are compartmentalized into other non-membranous organelles. In this review, we summarize recent findings about the function of these organelles in the Drosophila piRNA pathway by focusing on their assembly and function.
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19
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piRNA-Guided CRISPR-like Immunity in Eukaryotes. Trends Immunol 2019; 40:998-1010. [DOI: 10.1016/j.it.2019.09.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 09/17/2019] [Accepted: 09/17/2019] [Indexed: 02/07/2023]
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20
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The piRNA Response to Retroviral Invasion of the Koala Genome. Cell 2019; 179:632-643.e12. [PMID: 31607510 DOI: 10.1016/j.cell.2019.09.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/19/2019] [Accepted: 08/30/2019] [Indexed: 12/20/2022]
Abstract
Antisense Piwi-interacting RNAs (piRNAs) guide silencing of established transposons during germline development, and sense piRNAs drive ping-pong amplification of the antisense pool, but how the germline responds to genome invasion is not understood. The KoRV-A gammaretrovirus infects the soma and germline and is sweeping through wild koalas by a combination of horizontal and vertical transfer, allowing direct analysis of retroviral invasion of the germline genome. Gammaretroviruses produce spliced Env mRNAs and unspliced transcripts encoding Gag, Pol, and the viral genome, but KoRV-A piRNAs are almost exclusively derived from unspliced genomic transcripts and are strongly sense-strand biased. Significantly, selective piRNA processing of unspliced proviral transcripts is conserved from insects to placental mammals. We speculate that bypassed splicing generates a conserved molecular pattern that directs proviral genomic transcripts to the piRNA biogenesis machinery and that this "innate" piRNA response suppresses transposition until antisense piRNAs are produced, establishing sequence-specific adaptive immunity.
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21
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Ozata DM, Gainetdinov I, Zoch A, O'Carroll D, Zamore PD. PIWI-interacting RNAs: small RNAs with big functions. Nat Rev Genet 2019; 20:89-108. [PMID: 30446728 DOI: 10.1038/s41576-018-0073-3] [Citation(s) in RCA: 625] [Impact Index Per Article: 125.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
In animals, PIWI-interacting RNAs (piRNAs) of 21-35 nucleotides in length silence transposable elements, regulate gene expression and fight viral infection. piRNAs guide PIWI proteins to cleave target RNA, promote heterochromatin assembly and methylate DNA. The architecture of the piRNA pathway allows it both to provide adaptive, sequence-based immunity to rapidly evolving viruses and transposons and to regulate conserved host genes. piRNAs silence transposons in the germ line of most animals, whereas somatic piRNA functions have been lost, gained and lost again across evolution. Moreover, most piRNA pathway proteins are deeply conserved, but different animals employ remarkably divergent strategies to produce piRNA precursor transcripts. Here, we discuss how a common piRNA pathway allows animals to recognize diverse targets, ranging from selfish genetic elements to genes essential for gametogenesis.
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Affiliation(s)
- Deniz M Ozata
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ildar Gainetdinov
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ansgar Zoch
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Dónal O'Carroll
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.,Wellcome Centre for Cell Biology, School of Biological Sciences, The University of Edinburgh, Edinburgh, UK
| | - Phillip D Zamore
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA.
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22
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Duc C, Yoth M, Jensen S, Mouniée N, Bergman CM, Vaury C, Brasset E. Trapping a somatic endogenous retrovirus into a germline piRNA cluster immunizes the germline against further invasion. Genome Biol 2019; 20:127. [PMID: 31227013 PMCID: PMC6587276 DOI: 10.1186/s13059-019-1736-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 06/11/2019] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND For species survival, the germline must faithfully transmit genetic information to the progeny. Transposable elements (TEs) constitute a significant threat to genome stability due to their mobility. In the metazoan germline, their mobilization is limited by a class of small RNAs called PIWI-interacting RNAs (piRNAs) produced by dedicated genomic loci called piRNA clusters. Although the piRNA pathway is an adaptive genomic immunity system, it remains unclear how the germline gains protection from a new transposon invasion. RESULTS To address this question, we analyze Drosophila melanogaster lines harboring a deletion within flamenco, a major piRNA cluster specifically expressed in somatic follicular cells. This deletion leads to derepression of the retrotransposon ZAM in the somatic follicular cells and subsequent germline genome invasion. In this mutant line, we identify de novo production of sense and antisense ZAM-derived piRNAs that display a germinal molecular signature. These piRNAs originated from a new ZAM insertion into a germline dual-strand piRNA cluster and silence ZAM expression specifically in germ cells. Finally, we find that ZAM trapping in a germinal piRNA cluster is a frequent event that occurs early during the isolation of the mutant line. CONCLUSIONS Transposons can hijack the host developmental process to propagate whenever their silencing is lost. Here, we show that the germline can protect itself by trapping invading somatic-specific TEs into germline piRNA clusters. This is the first demonstration of "auto-immunization" of a germline endangered by mobilization of a surrounding somatic TE.
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Affiliation(s)
- Céline Duc
- GReD, Université Clermont Auvergne, CNRS, INSERM, Faculté de Médecine, 63000 Clermont-Ferrand, France
- Present address: UFIP UMR-CNRS 6286, Epigénétique: prolifération et différenciation, Faculté des Sciences et des Techniques, 2 rue de la Houssinière, 44322 Nantes, France
| | - Marianne Yoth
- GReD, Université Clermont Auvergne, CNRS, INSERM, Faculté de Médecine, 63000 Clermont-Ferrand, France
| | - Silke Jensen
- GReD, Université Clermont Auvergne, CNRS, INSERM, Faculté de Médecine, 63000 Clermont-Ferrand, France
| | - Nolwenn Mouniée
- GReD, Université Clermont Auvergne, CNRS, INSERM, Faculté de Médecine, 63000 Clermont-Ferrand, France
| | - Casey M. Bergman
- Department of Genetics and Institute of Bioinformatics, University of Georgia, 120 E. Green St, Athens, GA 30602 USA
| | - Chantal Vaury
- GReD, Université Clermont Auvergne, CNRS, INSERM, Faculté de Médecine, 63000 Clermont-Ferrand, France
| | - Emilie Brasset
- GReD, Université Clermont Auvergne, CNRS, INSERM, Faculté de Médecine, 63000 Clermont-Ferrand, France
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23
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Bourgeois Y, Boissinot S. On the Population Dynamics of Junk: A Review on the Population Genomics of Transposable Elements. Genes (Basel) 2019; 10:genes10060419. [PMID: 31151307 PMCID: PMC6627506 DOI: 10.3390/genes10060419] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 05/05/2019] [Accepted: 05/21/2019] [Indexed: 01/18/2023] Open
Abstract
Transposable elements (TEs) play an important role in shaping genomic organization and structure, and may cause dramatic changes in phenotypes. Despite the genetic load they may impose on their host and their importance in microevolutionary processes such as adaptation and speciation, the number of population genetics studies focused on TEs has been rather limited so far compared to single nucleotide polymorphisms (SNPs). Here, we review the current knowledge about the dynamics of transposable elements at recent evolutionary time scales, and discuss the mechanisms that condition their abundance and frequency. We first discuss non-adaptive mechanisms such as purifying selection and the variable rates of transposition and elimination, and then focus on positive and balancing selection, to finally conclude on the potential role of TEs in causing genomic incompatibilities and eventually speciation. We also suggest possible ways to better model TEs dynamics in a population genomics context by incorporating recent advances in TEs into the rich information provided by SNPs about the demography, selection, and intrinsic properties of genomes.
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Affiliation(s)
- Yann Bourgeois
- New York University Abu Dhabi, P.O. 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates.
| | - Stéphane Boissinot
- New York University Abu Dhabi, P.O. 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates.
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24
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Czech B, Munafò M, Ciabrelli F, Eastwood EL, Fabry MH, Kneuss E, Hannon GJ. piRNA-Guided Genome Defense: From Biogenesis to Silencing. Annu Rev Genet 2018; 52:131-157. [PMID: 30476449 PMCID: PMC10784713 DOI: 10.1146/annurev-genet-120417-031441] [Citation(s) in RCA: 285] [Impact Index Per Article: 47.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
PIWI-interacting RNAs (piRNAs) and their associated PIWI clade Argonaute proteins constitute the core of the piRNA pathway. In gonadal cells, this conserved pathway is crucial for genome defense, and its main function is to silence transposable elements. This is achieved through posttranscriptional and transcriptional gene silencing. Precursors that give rise to piRNAs require specialized transcription and transport machineries because piRNA biogenesis is a cytoplasmic process. The ping-pong cycle, a posttranscriptional silencing mechanism, combines the cleavage-dependent silencing of transposon RNAs with piRNA production. PIWI proteins also function in the nucleus, where they scan for nascent target transcripts with sequence complementarity, instructing transcriptional silencing and deposition of repressive chromatin marks at transposon loci. Although studies have revealed numerous factors that participate in each branch of the piRNA pathway, the precise molecular roles of these factors often remain unclear. In this review, we summarize our current understanding of the mechanisms involved in piRNA biogenesis and function.
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Affiliation(s)
- Benjamin Czech
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Marzia Munafò
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Filippo Ciabrelli
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Evelyn L Eastwood
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Martin H Fabry
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Emma Kneuss
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Cambridge CB2 0RE, United Kingdom; ,
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25
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Regulating gene expression in animals through RNA endonucleolytic cleavage. Heliyon 2018; 4:e00908. [PMID: 30426105 PMCID: PMC6223193 DOI: 10.1016/j.heliyon.2018.e00908] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 10/28/2018] [Accepted: 10/29/2018] [Indexed: 12/22/2022] Open
Abstract
The expression of any gene must be precisely controlled for appropriate function. This expression can be controlled at various levels. This includes epigenetic regulation through DNA methylation or histone modifications. At the posttranscriptional level, regulation can be via alternative splicing or controlling messenger RNA (mRNA) stability. RNA cleavage is one way to control mRNA stability. For example, microRNA (miRNA)-induced mRNA cleavage has long been recognised in plants. RNA cleavage also appears to be widespread in other kingdoms of life, and it is now clear that mRNA cleavage plays critical functions in animals. Although miRNA-induced mRNA cleavage can occur in animals, it is not a widespread mechanism. Instead, mRNA cleavage can be induced by a range of other mechanisms, including by endogenous short inhibitory RNAs (endo-siRNAs), as well as the Ribonuclease III (RNase III) enzymes Drosha and Dicer. In addition, RNA cleavage induced by endo-siRNAs and PIWI-interacting RNAs (piRNAs) is important for genome defence against transposons. Moreover, several RNase has been identified as important antiviral mediators. In this review, we will discuss these various RNA endonucleolytic cleavage mechanisms utilised by animals to regulate the expression of genes and as a defence against retrotransposons and viral infection.
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26
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Abstract
Gametogenesis represents the most dramatic cellular differentiation pathways in both female and male flies. At the genome level, meiosis ensures that diploid germ cells become haploid gametes. At the epigenome level, extensive changes are required to turn on and shut off gene expression in a precise spatiotemporally controlled manner. Research applying conventional molecular genetics and cell biology, in combination with rapidly advancing genomic tools have helped us to investigate (1) how germ cells maintain lineage specificity throughout their adult reproductive lifetime; (2) what molecular mechanisms ensure proper oogenesis and spermatogenesis, as well as protect genome integrity of the germline; (3) how signaling pathways contribute to germline-soma communication; and (4) if such communication is important. In this chapter, we highlight recent discoveries that have improved our understanding of these questions. On the other hand, restarting a new life cycle upon fertilization is a unique challenge faced by gametes, raising questions that involve intergenerational and transgenerational epigenetic inheritance. Therefore, we also discuss new developments that link changes during gametogenesis to early embryonic development-a rapidly growing field that promises to bring more understanding to some fundamental questions regarding metazoan development.
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27
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Fu Y, Yang Y, Zhang H, Farley G, Wang J, Quarles KA, Weng Z, Zamore PD. The genome of the Hi5 germ cell line from Trichoplusia ni, an agricultural pest and novel model for small RNA biology. eLife 2018; 7:31628. [PMID: 29376823 PMCID: PMC5844692 DOI: 10.7554/elife.31628] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Accepted: 01/26/2018] [Indexed: 12/30/2022] Open
Abstract
We report a draft assembly of the genome of Hi5 cells from the lepidopteran insect pest, Trichoplusia ni, assigning 90.6% of bases to one of 28 chromosomes and predicting 14,037 protein-coding genes. Chemoreception and detoxification gene families reveal T. ni-specific gene expansions that may explain its widespread distribution and rapid adaptation to insecticides. Transcriptome and small RNA data from thorax, ovary, testis, and the germline-derived Hi5 cell line show distinct expression profiles for 295 microRNA- and >393 piRNA-producing loci, as well as 39 genes encoding small RNA pathway proteins. Nearly all of the W chromosome is devoted to piRNA production, and T. ni siRNAs are not 2´-O-methylated. To enable use of Hi5 cells as a model system, we have established genome editing and single-cell cloning protocols. The T. ni genome provides insights into pest control and allows Hi5 cells to become a new tool for studying small RNAs ex vivo. A common moth called the cabbage looper is becoming increasingly relevant to the scientific community. Its caterpillars are a serious threat to cabbage, broccoli and cauliflower crops, and they have started to resist the pesticides normally used to control them. Moreover, the insect’s germline cells – the ones that will produce sperm and eggs – are used in laboratories as ‘factories’ to artificially produce proteins of interest. The germline cells also host a group of genetic mechanisms called RNA silencing. One of these processes is known as piRNA, and it protects the genome against ‘jumping genes’. These genetic elements can cause mutations by moving from place to place in the DNA: in germline cells, piRNA suppresses them before the genetic information is transmitted to the next generation. Not all germline cells grow equally well under experimental conditions, or are easy to use to examine piRNA mechanisms in a laboratory. The germline cells from the cabbage looper, on the other hand, have certain characteristics that would make them ideal to study piRNA in insects. However, the genome of the moth had not yet been fully resolved. This hinders research on new ways of controlling the pest, on how to use the germline cells to produce more useful proteins, or on piRNA. Decoding a genome requires several steps. First, the entire genetic information is broken in short sections that can then be deciphered. Next, these segments need to be ‘assembled’ – put together, and in the right order, to reconstitute the entire genome. Certain portions of the genome, which are formed of repeats of the same sections, can be difficult to assemble. Finally, the genome must be annotated: the different regions – such as the genes – need to be identified and labeled. Here, Fu et al. assembled and annotated the genome of the cabbage looper, and in the process developed strategies that could be used for other species with a lot of repeated sequences in their genomes. Having access to the looper’s full genetic information makes it possible to use their germline cells to produce new types of proteins, for example for pharmaceutical purposes. Fu et al. went on to make working with these cells even easier by refining protocols so that modern research techniques, such as the gene-editing technology CRISPR-Cas9, can be used on the looper germline cells. The mapping of the genome also revealed that the genes involved in removing toxins from the insects’ bodies are rapidly evolving, which may explain why the moths readily become resistant to insecticides. This knowledge could help finding new ways of controlling the pest. Finally, the genes involved in RNA silencing were labeled: results show that an entire chromosome is the source of piRNAs. Combined with the new protocols developed by Fu et al., this could make cabbage looper germline cells the default option for any research into the piRNA mechanism. How piRNA works in the moth could inform work on human piRNA, as these processes are highly similar across the animal kingdom.
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Affiliation(s)
- Yu Fu
- Bioinformatics Program, Boston University, Boston, United States.,Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, United States
| | - Yujing Yang
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, United States
| | - Han Zhang
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, United States
| | - Gwen Farley
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, United States
| | - Junling Wang
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, United States
| | - Kaycee A Quarles
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, United States
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, United States
| | - Phillip D Zamore
- RNA Therapeutics Institute and Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, United States
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28
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Yamashiro H, Siomi MC. PIWI-Interacting RNA in Drosophila: Biogenesis, Transposon Regulation, and Beyond. Chem Rev 2017; 118:4404-4421. [PMID: 29281264 DOI: 10.1021/acs.chemrev.7b00393] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PIWI-interacting RNAs (piRNAs) are germline-enriched small RNAs that control transposons to maintain genome integrity. To achieve this, upon being processed from piRNA precursors, most of which are transcripts of intergenic piRNA clusters, piRNAs bind PIWI proteins, germline-specific Argonaute proteins, to form effector complexes. The mechanism of this piRNA-mediated transposon silencing pathway is fundamentally similar to that of siRNA/miRNA-dependent gene silencing in that a small RNA guides its partner Argonaute protein to target gene transcripts for repression via RNA-RNA base pairing. However, the uniqueness of this piRNA pathway has emerged through intensive genetic, biochemical, bioinformatic, and structural investigations. Here, we review the studies that elucidated the piRNA pathway, mainly in Drosophila, by describing both historical and recent progress. Studies in other species that have made important contributions to the field are also described.
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Affiliation(s)
- Haruna Yamashiro
- Department of Biological Sciences, Graduate School of Science , The University of Tokyo , Tokyo 113-0032 , Japan
| | - Mikiko C Siomi
- Department of Biological Sciences, Graduate School of Science , The University of Tokyo , Tokyo 113-0032 , Japan
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29
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The New RNA World: Growing Evidence for Long Noncoding RNA Functionality. Trends Genet 2017; 33:665-676. [DOI: 10.1016/j.tig.2017.08.002] [Citation(s) in RCA: 155] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 08/01/2017] [Accepted: 08/02/2017] [Indexed: 12/18/2022]
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Silencing of Transposable Elements by piRNAs in Drosophila: An Evolutionary Perspective. GENOMICS PROTEOMICS & BIOINFORMATICS 2017; 15:164-176. [PMID: 28602845 PMCID: PMC5487533 DOI: 10.1016/j.gpb.2017.01.006] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 01/02/2017] [Accepted: 01/12/2017] [Indexed: 11/28/2022]
Abstract
Transposable elements (TEs) are DNA sequences that can move within the genome. TEs have greatly shaped the genomes, transcriptomes, and proteomes of the host organisms through a variety of mechanisms. However, TEs generally disrupt genes and destabilize the host genomes, which substantially reduce fitness of the host organisms. Understanding the genomic distribution and evolutionary dynamics of TEs will greatly deepen our understanding of the TE-mediated biological processes. Most TE insertions are highly polymorphic in Drosophila melanogaster, providing us a good system to investigate the evolution of TEs at the population level. Decades of theoretical and experimental studies have well established “transposition-selection” population genetics model, which assumes that the equilibrium between TE replication and purifying selection determines the copy number of TEs in the genome. In the last decade, P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) were demonstrated to be master repressors of TE activities in Drosophila. The discovery of piRNAs revolutionized our understanding of TE repression, because it reveals that the host organisms have evolved an adaptive mechanism to defend against TE invasion. Tremendous progress has been made to understand the molecular mechanisms by which piRNAs repress active TEs, although many details in this process remain to be further explored. The interaction between piRNAs and TEs well explains the molecular mechanisms underlying hybrid dysgenesis for the I-R and P-M systems in Drosophila, which have puzzled evolutionary biologists for decades. The piRNA repression pathway provides us an unparalleled system to study the co-evolutionary process between parasites and host organisms.
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Production of Small Noncoding RNAs from the flamenco Locus Is Regulated by the gypsy Retrotransposon of Drosophila melanogaster. Genetics 2016; 204:631-644. [PMID: 27558137 DOI: 10.1534/genetics.116.187922] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 08/18/2016] [Indexed: 11/18/2022] Open
Abstract
Protective mechanisms based on RNA silencing directed against the propagation of transposable elements are highly conserved in eukaryotes. The control of transposable elements is mediated by small noncoding RNAs, which derive from transposon-rich heterochromatic regions that function as small RNA-generating loci. These clusters are transcribed and the precursor transcripts are processed to generate Piwi-interacting RNAs (piRNAs) and endogenous small interfering RNAs (endo-siRNAs), which silence transposable elements in gonads and somatic tissues. The flamenco locus is a Drosophila melanogaster small RNA cluster that controls gypsy and other transposable elements, and has played an important role in understanding how small noncoding RNAs repress transposable elements. In this study, we describe a cosuppression mechanism triggered by new euchromatic gypsy insertions in genetic backgrounds carrying flamenco alleles defective in gypsy suppression. We found that the silencing of gypsy is accompanied by the silencing of other transposons regulated by flamenco, and of specific flamenco sequences from which small RNAs against gypsy originate. This cosuppression mechanism seems to depend on a post-transcriptional regulation that involves both endo-siRNA and piRNA pathways and is associated with the occurrence of developmental defects. In conclusion, we propose that new gypsy euchromatic insertions trigger a post-transcriptional silencing of gypsy sense and antisense sequences, which modifies the flamenco activity. This cosuppression mechanism interferes with some developmental processes, presumably by influencing the expression of specific genes.
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Czech B, Hannon GJ. One Loop to Rule Them All: The Ping-Pong Cycle and piRNA-Guided Silencing. Trends Biochem Sci 2016; 41:324-337. [PMID: 26810602 PMCID: PMC4819955 DOI: 10.1016/j.tibs.2015.12.008] [Citation(s) in RCA: 300] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 12/17/2015] [Accepted: 12/22/2015] [Indexed: 01/06/2023]
Abstract
The PIWI-interacting RNA (piRNA) pathway is a conserved defense mechanism that protects the genetic information of animal germ cells from the deleterious effects of molecular parasites, such as transposons. Discovered nearly a decade ago, this small RNA silencing system comprises PIWI-clade Argonaute proteins and their associated RNA-binding partners, the piRNAs. In this review, we highlight recent work that has advanced our understanding of how piRNAs preserve genome integrity across generations. We discuss the mechanism of piRNA biogenesis, give an overview of common themes as well as differences in piRNA-mediated silencing between species, and end by highlighting known and emerging functions of piRNAs.
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Affiliation(s)
- Benjamin Czech
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, CB2 0RE, UK.
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Cambridge, CB2 0RE, UK.
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He Z, Liu B, Wang X, Bian M, He R, Yan J, Zhong M, Zhao X, Liu X. Construction and Validation of a Dual-Transgene Vector System for Stable Transformation in Plants. J Genet Genomics 2016; 43:199-207. [PMID: 27157807 DOI: 10.1016/j.jgg.2016.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Revised: 02/14/2016] [Accepted: 02/25/2016] [Indexed: 11/16/2022]
Abstract
In this study, we constructed dual-transgene vectors (pDT1, pDT7, and pDT7G) that simultaneously co-expressed two genes in plants. ACTIN2 and UBQ10 promoters were used to control the expression of these two genes. The 4×Myc, 3×HA, and 3×Flag reporter genes allowed for the convenient identification of a tunable co-expression system in plants, whereas the dexamethasone (Dex) inducible reporter gene C-terminus of the glucocorticoid receptor (cGR) provided Dex-dependent translocation of the fusion gene between the nucleus and cytoplasm. The function of pDT vectors was validated using four pairwise genes in Nicotiana benthamiana or Arabidopsis thaliana. The co-expression efficiency of two genes from the pDT1 and pDT7G vectors was 35% and 42%, respectively, which ensured the generation of sufficient transgenic materials. These pDT vectors are simple, reliable, efficient, and time-saving tools for the co-expression of two genes through a single transformation event and can be used in the study of protein-protein interactions or multi-component complexes.
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Affiliation(s)
- Zhimin He
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha 410082, China; Department of Molecular, Cell & Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Bin Liu
- Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Xu Wang
- Department of Molecular, Cell & Developmental Biology, University of California, Los Angeles, CA 90095, USA
| | - Mingdi Bian
- College of Plant Sciences, Jilin University, Changchun 130062, China
| | - Reqing He
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha 410082, China
| | - Jindong Yan
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha 410082, China
| | - Ming Zhong
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha 410082, China
| | - Xiaoying Zhao
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha 410082, China.
| | - Xuanming Liu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha 410082, China; State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, China.
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A Small RNA-Based Immune System Defends Germ Cells against Mobile Genetic Elements. Stem Cells Int 2015; 2016:7595791. [PMID: 26681955 PMCID: PMC4670677 DOI: 10.1155/2016/7595791] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 06/11/2015] [Indexed: 11/17/2022] Open
Abstract
Transposons are mobile genetic elements that threaten the survival of species by destabilizing the germline genomes. Limiting the spread of these selfish elements is imperative. Germ cells employ specialized small regulatory RNA pathways to restrain transposon activity. PIWI proteins and Piwi-interacting RNAs (piRNAs) silence transposons at the transcriptional and posttranscriptional level with loss-of-function mutant animals universally exhibiting sterility often associated with germ cell defects. This short review aims to illustrate basic strategies of piRNA-guided defense against transposons. Mechanisms of piRNA silencing are most readily studied in Drosophila melanogaster, which serves as a model to delineate molecular concepts and as a reference for mammalian piRNA systems. PiRNA pathways utilize two major strategies to handle the challenges of transposon control: (1) the hard-wired molecular memory of prior transpositions enables recognition of mobile genetic elements and discriminates transposons from host genes; (2) a feed-forward adaptation mechanism shapes piRNA populations to selectively combat the immediate threat of transposon transcripts. In flies, maternally contributed PIWI-piRNA complexes bolster both of these lines of defense and ensure transgenerational immunity. While recent studies have provided a conceptual framework of what could be viewed as an ancient immune system, we are just beginning to appreciate its many molecular innovations.
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Parrish NF, Fujino K, Shiromoto Y, Iwasaki YW, Ha H, Xing J, Makino A, Kuramochi-Miyagawa S, Nakano T, Siomi H, Honda T, Tomonaga K. piRNAs derived from ancient viral processed pseudogenes as transgenerational sequence-specific immune memory in mammals. RNA (NEW YORK, N.Y.) 2015; 21:1691-1703. [PMID: 26283688 PMCID: PMC4574747 DOI: 10.1261/rna.052092.115] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 07/08/2015] [Indexed: 06/04/2023]
Abstract
Endogenous bornavirus-like nucleoprotein elements (EBLNs) are sequences within vertebrate genomes derived from reverse transcription and integration of ancient bornaviral nucleoprotein mRNA via the host retrotransposon machinery. While species with EBLNs appear relatively resistant to bornaviral disease, the nature of this association is unclear. We hypothesized that EBLNs could give rise to antiviral interfering RNA in the form of PIWI-interacting RNAs (piRNAs), a class of small RNA known to silence transposons but not exogenous viruses. We found that in both rodents and primates, which acquired their EBLNs independently some 25-40 million years ago, EBLNs are present within piRNA-generating regions of the genome far more often than expected by chance alone (ℙ = 8 × 10(-3)-6 × 10(-8)). Three of the seven human EBLNs fall within annotated piRNA clusters and two marmoset EBLNs give rise to bona fide piRNAs. In both rats and mice, at least two of the five EBLNs give rise to abundant piRNAs in the male gonad. While no EBLNs are syntenic between rodent and primate, some of the piRNA clusters containing EBLNs are; thus we deduce that EBLNs were integrated into existing piRNA clusters. All true piRNAs derived from EBLNs are antisense relative to the proposed ancient bornaviral nucleoprotein mRNA. These observations are consistent with a role for EBLN-derived piRNA-like RNAs in interfering with ancient bornaviral infection. They raise the hypothesis that retrotransposon-dependent virus-to-host gene flow could engender RNA-mediated, sequence-specific antiviral immune memory in metazoans analogous to the CRISPR/Cas system in prokaryotes.
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Affiliation(s)
- Nicholas F Parrish
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
| | - Kan Fujino
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
| | - Yusuke Shiromoto
- Department of Pathology, Medical School and Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Yuka W Iwasaki
- Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Hongseok Ha
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Jinchuan Xing
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA
| | - Akiko Makino
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan Center for Emerging Virus Research, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan
| | - Satomi Kuramochi-Miyagawa
- Department of Pathology, Medical School and Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Toru Nakano
- Department of Pathology, Medical School and Graduate School of Frontier Biosciences, Osaka University, Osaka 565-0871, Japan
| | - Haruhiko Siomi
- Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Tomoyuki Honda
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan Department of Tumor Viruses, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
| | - Keizo Tomonaga
- Department of Viral Oncology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan Department of Tumor Viruses, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, Kyoto 606-8507, Japan
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36
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Abstract
PIWI-interacting RNAs (piRNAs) are a class of small RNAs that are 24-31 nucleotides in length. They associate with PIWI proteins, which constitute a germline-specific subclade of the Argonaute family, to form effector complexes known as piRNA-induced silencing complexes, which repress transposons via transcriptional or posttranscriptional mechanisms and maintain germline genome integrity. In addition to having a role in transposon silencing, piRNAs in diverse organisms function in the regulation of cellular genes. In some cases, piRNAs have shown transgenerational inheritance to pass on the memory of "self" and "nonself," suggesting a contribution to various cellular processes over generations. Many piRNA factors have been identified; however, both the molecular mechanisms leading to the production of mature piRNAs and the effector phases of gene silencing are still enigmatic. Here, we summarize the current state of our knowledge on the biogenesis of piRNA, its biological functions, and the underlying mechanisms.
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Affiliation(s)
- Yuka W Iwasaki
- Department of Molecular Biology, Keio University School of Medicine, Tokyo 160-8582, Japan;
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37
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Touret F, Guiguen F, Greenland T, Terzian C. In between: gypsy in Drosophila melanogaster reveals new insights into endogenous retrovirus evolution. Viruses 2014; 6:4914-25. [PMID: 25502325 PMCID: PMC4276936 DOI: 10.3390/v6124914] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 11/17/2014] [Accepted: 11/26/2014] [Indexed: 11/16/2022] Open
Abstract
Retroviruses are RNA viruses that are able to synthesize a DNA copy of their genome and insert it into a chromosome of the host cell. Sequencing of different eukaryote genomes has revealed the presence of many such endogenous retroviral sequences. The mechanisms by which these retroviral sequences have colonized the genome are still unknown, and the endogenous retrovirus gypsy of Drosophila melanogaster is a powerful experimental model for deciphering this process in vivo. Gypsy is expressed in a layer of somatic cells, and then transferred into the oocyte by an unknown mechanism. This critical step is the start of the endogenization process. Moreover gypsy has been shown to have infectious properties, probably due to its envelope gene acquired from a baculovirus. Recently we have also shown that gypsy maternal transmission is reduced in the presence of the endosymbiotic bacterium Wolbachia. These studies demonstrate that gypsy is a unique and powerful model for understanding the endogenization of retroviruses.
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Affiliation(s)
- Franck Touret
- Pathologie Comparée, Unité Mixte de Recherche 754, Institut National de la Recherche Agronomique, Université Claude Bernard Lyon1, Université de Lyon, Unité Mixte de Service 3444, 69367 Lyon Cedex 7, France.
| | - François Guiguen
- Pathologie Comparée, Unité Mixte de Recherche 754, Institut National de la Recherche Agronomique, Université Claude Bernard Lyon1, Université de Lyon, Unité Mixte de Service 3444, 69367 Lyon Cedex 7, France.
| | | | - Christophe Terzian
- Pathologie Comparée, Unité Mixte de Recherche 754, Institut National de la Recherche Agronomique, Université Claude Bernard Lyon1, Université de Lyon, Unité Mixte de Service 3444, 69367 Lyon Cedex 7, France.
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38
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Abstract
Retroelements with long-terminal repeats (LTRs) inhabit nearly all eukaryotic genomes. During the time of their rich evolutionary history they have developed highly diverse forms, ranging from ordinary retrotransposons to complex pathogenic retroviruses such as HIV-I. Errantiviruses are a group of insect endogenous LTR elements that share structural and functional features with vertebrate endogenous retroviruses. The errantiviruses illustrate one of the evolutionary strategies of retrotransposons to become infective, which together with their similarities to vertebrate retroviruses make them an attractive object of research promising to shed more light on the evolution of retroviruses.
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Affiliation(s)
- Yury Stefanov
- Engelhardt Institute of Molecular Biology; Russian Academy of Sciences; Moscow, Russia
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39
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Wolbachia influences the maternal transmission of the gypsy endogenous retrovirus in Drosophila melanogaster. mBio 2014; 5:e01529-14. [PMID: 25182324 PMCID: PMC4173782 DOI: 10.1128/mbio.01529-14] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The endosymbiotic bacteria of the genus Wolbachia are present in most insects and are maternally transmitted through the germline. Moreover, these intracellular bacteria exert antiviral activity against insect RNA viruses, as in Drosophila melanogaster, which could explain the prevalence of Wolbachia bacteria in natural populations. Wolbachia is maternally transmitted in D. melanogaster through a mechanism that involves distribution at the posterior pole of mature oocytes and then incorporation into the pole cells of the embryos. In parallel, maternal transmission of several endogenous retroviruses is well documented in D. melanogaster. Notably, gypsy retrovirus is expressed in permissive follicle cells and transferred to the oocyte and then to the offspring by integrating into their genomes. Here, we show that the presence of Wolbachia wMel reduces the rate of gypsy insertion into the ovo gene. However, the presence of Wolbachia does not modify the expression levels of gypsy RNA and envelope glycoprotein from either permissive or restrictive ovaries. Moreover, Wolbachia affects the pattern of distribution of the retroviral particles and the gypsy envelope protein in permissive follicle cells. Altogether, our results enlarge the knowledge of the antiviral activity of Wolbachia to include reducing the maternal transmission of endogenous retroviruses in D. melanogaster. Animals have established complex relationships with bacteria and viruses that spread horizontally among individuals or are vertically transmitted, i.e., from parents to offspring. It is well established that members of the genus Wolbachia, maternally inherited symbiotic bacteria present mainly in arthropods, reduce the replication of several RNA viruses transmitted horizontally. Here, we demonstrate for the first time that Wolbachia diminishes the maternal transmission of gypsy, an endogenous retrovirus in Drosophila melanogaster. We hypothesize that gypsy cannot efficiently integrate into the germ cells of offspring during embryonic development in the presence of Wolbachia because both are competitors for localization to the posterior pole of the egg. More generally, it would be of interest to analyze the influence of Wolbachia on vertically transmitted exogenous viruses, such as some arboviruses.
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40
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Goriaux C, Théron E, Brasset E, Vaury C. History of the discovery of a master locus producing piRNAs: the flamenco/COM locus in Drosophila melanogaster. Front Genet 2014; 5:257. [PMID: 25136352 PMCID: PMC4120762 DOI: 10.3389/fgene.2014.00257] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Accepted: 07/12/2014] [Indexed: 11/14/2022] Open
Abstract
The discovery of transposable elements (TEs) in the 1950s by B. McClintock implied the existence of cellular regulatory systems controlling TE activity. The discovery of flamenco (flam) an heterochromatic locus from Drosophila melanogaster and its ability to survey several TEs such as gypsy, ZAM, and Idefix contributed to peer deeply into the mechanisms of the genetic and epigenetic regulation of TEs. flam was the first cluster producing small RNAs to be discovered long before RNAi pathways were identified in 1998. As a result of the detailed genetic analyses performed by certain laboratories and of the sophisticated genetic tools they developed, this locus has played a major role in our understanding of piRNA mediated TE repression in animals. Here we review the first discovery of this locus and retrace decades of studies that led to our current understanding of the relationship between genomes and their TE targets.
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Affiliation(s)
- Coline Goriaux
- Laboratoire GReD, Faculté de Médecine, Clermont Université - Université d'Auvergne, Clermont-Ferrand France ; INSERM, U 1103, Clermont-Ferrand France ; CNRS, UMR 6293, Clermont-Ferrand France
| | - Emmanuelle Théron
- Laboratoire GReD, Faculté de Médecine, Clermont Université - Université d'Auvergne, Clermont-Ferrand France ; INSERM, U 1103, Clermont-Ferrand France ; CNRS, UMR 6293, Clermont-Ferrand France
| | - Emilie Brasset
- Laboratoire GReD, Faculté de Médecine, Clermont Université - Université d'Auvergne, Clermont-Ferrand France ; INSERM, U 1103, Clermont-Ferrand France ; CNRS, UMR 6293, Clermont-Ferrand France
| | - Chantal Vaury
- Laboratoire GReD, Faculté de Médecine, Clermont Université - Université d'Auvergne, Clermont-Ferrand France ; INSERM, U 1103, Clermont-Ferrand France ; CNRS, UMR 6293, Clermont-Ferrand France
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Yamanaka S, Siomi MC, Siomi H. piRNA clusters and open chromatin structure. Mob DNA 2014; 5:22. [PMID: 25126116 PMCID: PMC4131230 DOI: 10.1186/1759-8753-5-22] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 07/09/2014] [Indexed: 12/27/2022] Open
Abstract
Transposable elements (TEs) are major structural components of eukaryotic genomes; however, mobilization of TEs generally has negative effects on the host genome. To counteract this threat, host cells have evolved genetic and epigenetic mechanisms that keep TEs silenced. One such mechanism involves the Piwi-piRNA complex, which represses TEs in animal gonads either by cleaving TE transcripts in the cytoplasm or by directing specific chromatin modifications at TE loci in the nucleus. Most Piwi-interacting RNAs (piRNAs) are derived from genomic piRNA clusters. There has been remarkable progress in our understanding of the mechanisms underlying piRNA biogenesis. However, little is known about how a specific locus in the genome is converted into a piRNA-producing site. In this review, we will discuss a possible link between chromatin boundaries and piRNA cluster formation.
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Affiliation(s)
- Soichiro Yamanaka
- Department of Molecular Biology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
| | - Mikiko C Siomi
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan
| | - Haruhiko Siomi
- Department of Molecular Biology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo 160-8582, Japan
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42
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Chambeyron S, Seitz H. Insect small non-coding RNA involved in epigenetic regulations. CURRENT OPINION IN INSECT SCIENCE 2014; 1:1-9. [PMID: 32846724 DOI: 10.1016/j.cois.2014.05.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 05/01/2014] [Accepted: 05/01/2014] [Indexed: 06/11/2023]
Abstract
Small regulatory RNAs can not only guide post-transcriptional repression of target genes, but some of them can also direct heterochromatin formation of specific genomic loci. Here we review the published literature on small RNA-guided epigenetic regulation in insects. The recent development of novel analytical technologies (deep sequencing and RNAi screens) has led to the identification of some of the factors involved in these processes, as well as their molecular mechanism and subcellular localization. Other findings uncovered an additional mode of epigenetic control, where maternally inherited small RNAs can affect phenotypes in a stable, transgenerational manner. The evolutive history of small RNA effector proteins in insects suggests that these two modes of regulation are variably conserved among species.
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Affiliation(s)
- Séverine Chambeyron
- Institut de Génétique Humaine, Centre National de la Recherche Scientifique (CNRS), UPR 1142, 141, rue de la Cardonille, 34396 Montpellier Cedex 5, France
| | - Hervé Seitz
- Institut de Génétique Humaine, Centre National de la Recherche Scientifique (CNRS), UPR 1142, 141, rue de la Cardonille, 34396 Montpellier Cedex 5, France.
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43
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Olovnikov IA, Kalmykova AI. piRNA clusters as a main source of small RNAs in the animal germline. BIOCHEMISTRY (MOSCOW) 2014; 78:572-84. [PMID: 23980884 DOI: 10.1134/s0006297913060035] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PIWI subfamily Argonaute proteins and small RNAs bound to them (PIWI interacting RNA, piRNA) control mobilization of transposable elements (TE) in the animal germline. piRNAs are generated by distinct genomic regions termed piRNA clusters. piRNA clusters are often extensive loci enriched in damaged fragments of TEs. New TE integration into piRNA clusters causes production of TE-specific piRNAs and repression of cognate sequences. piRNAs are thought to be generated from long single-stranded precursors encoded by piRNA clusters. Special chromatin structures might be essential to distinguish these genomic loci as a source for piRNAs. In this review, we present recent findings on the structural organization of piRNA clusters and piRNA biogenesis in Drosophila and other organisms, which are important for understanding a key epigenetic mechanism that provides defense against TE expansion.
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Affiliation(s)
- I A Olovnikov
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
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44
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Goriaux C, Desset S, Renaud Y, Vaury C, Brasset E. Transcriptional properties and splicing of the flamenco piRNA cluster. EMBO Rep 2014; 15:411-8. [PMID: 24562610 DOI: 10.1002/embr.201337898] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In Drosophila, the piRNA cluster, flamenco, produces most of the piRNAs (PIWI-interacting RNAs) that silence transposable elements in the somatic follicle cells during oogenesis. These piRNAs are thought to be processed from a long single-stranded precursor transcript. Here, we demonstrate that flamenco transcription is initiated from an RNA polymerase II promoter containing an initiator motif (Inr) and downstream promoter element (DPE) and requires the transcription factor, Cubitus interruptus. We show that the flamenco precursor transcript undergoes differential alternative splicing to generate diverse RNA precursors that are processed to piRNAs. Our data reveal dynamic processing steps giving rise to piRNA cluster precursors.
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Affiliation(s)
- Coline Goriaux
- Clermont Université Université d'Auvergne, Clermont-Ferrand, France
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45
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Distribution, evolution, and diversity of retrotransposons at the flamenco locus reflect the regulatory properties of piRNA clusters. Proc Natl Acad Sci U S A 2013; 110:19842-7. [PMID: 24248389 DOI: 10.1073/pnas.1313677110] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Most of our understanding of Drosophila heterochromatin structure and evolution has come from the annotation of heterochromatin from the isogenic y; cn bw sp strain. However, almost nothing is known about the heterochromatin's structural dynamics and evolution. Here, we focus on a 180-kb heterochromatic locus producing Piwi-interacting RNAs (piRNA cluster), the flamenco (flam) locus, known to be responsible for the control of at least three transposable elements (TEs). We report its detailed structure in three different Drosophila lines chosen according to their capacity to repress or not to repress the expression of two retrotransposons named ZAM and Idefix, and we show that they display high structural diversity. Numerous rearrangements due to homologous and nonhomologous recombination, deletions and segmental duplications, and loss and gain of TEs are diverse sources of active genomic variation at this locus. Notably, we evidence a correlation between the presence of ZAM and Idefix in this piRNA cluster and their silencing. They are absent from flam in the strain where they are derepressed. We show that, unexpectedly, more than half of the flam locus results from recent TE insertions and that most of the elements concerned are prone to horizontal transfer between species of the melanogaster subgroup. We build a model showing how such high and constant dynamics of a piRNA master locus open the way to continual emergence of new patterns of piRNA biogenesis leading to changes in the level of transposition control.
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Palazzo A, Marconi S, Specchia V, Bozzetti MP, Ivics Z, Caizzi R, Marsano RM. Functional characterization of the Bari1 transposition system. PLoS One 2013; 8:e79385. [PMID: 24244492 PMCID: PMC3828361 DOI: 10.1371/journal.pone.0079385] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 09/20/2013] [Indexed: 01/12/2023] Open
Abstract
The transposons of the Bari family are mobile genetic elements widespread in the Drosophila genus. However, despite a broad diffusion, virtually no information is available on the mechanisms underlying their mobility. In this paper we report the functional characterization of the Bari elements transposition system. Using the Bari1 element as a model, we investigated the subcellular localization of the transposase, its physical interaction with the transposon, and its catalytic activity. The Bari1 transposase localized in the nucleus and interacted with the terminal sequences of the transposon both in vitro and in vivo, however, no transposition activity was detected in transposition assays. Profiling of mRNAs expressed by the transposase gene revealed the expression of abnormal, internally processed transposase transcripts encoding truncated, catalytically inactive transposase polypeptides. We hypothesize that a post-transcriptional control mechanism produces transposase-derived polypeptides that effectively repress transposition. Our findings suggest further clues towards understanding the mechanisms that control transposition of an important class of mobile elements, which are both an endogenous source of genomic variability and widely used as transformation vectors/biotechnological tools.
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Affiliation(s)
| | - Simona Marconi
- Dipartimento di Biologia, Università di Bari, Bari, Italy
| | - Valeria Specchia
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali (DiSTeBA), Università del Salento, Lecce, Italy
| | - Maria Pia Bozzetti
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali (DiSTeBA), Università del Salento, Lecce, Italy
| | - Zoltán Ivics
- Division of Medical Biotechnology, Paul Ehrlich Institute, Langen, Germany
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Mani SR, Juliano CE. Untangling the web: the diverse functions of the PIWI/piRNA pathway. Mol Reprod Dev 2013; 80:632-64. [PMID: 23712694 DOI: 10.1002/mrd.22195] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 05/13/2013] [Indexed: 12/26/2022]
Abstract
Small RNAs impact several cellular processes through gene regulation. Argonaute proteins bind small RNAs to form effector complexes that control transcriptional and post-transcriptional gene expression. PIWI proteins belong to the Argonaute protein family, and bind PIWI-interacting RNAs (piRNAs). They are highly abundant in the germline, but are also expressed in some somatic tissues. The PIWI/piRNA pathway has a role in transposon repression in Drosophila, which occurs both by epigenetic regulation and post-transcriptional degradation of transposon mRNAs. These functions are conserved, but clear differences in the extent and mechanism of transposon repression exist between species. Mutations in piwi genes lead to the upregulation of transposon mRNAs. It is hypothesized that this increased transposon mobilization leads to genomic instability and thus sterility, although no causal link has been established between transposon upregulation and genome instability. An alternative scenario could be that piwi mutations directly affect genomic instability, and thus lead to increased transposon expression. We propose that the PIWI/piRNA pathway controls genome stability in several ways: suppression of transposons, direct regulation of chromatin architecture and regulation of genes that control important biological processes related to genome stability. The PIWI/piRNA pathway also regulates at least some, if not many, protein-coding genes, which further lends support to the idea that piwi genes may have broader functions beyond transposon repression. An intriguing possibility is that the PIWI/piRNA pathway is using transposon sequences to coordinate the expression of large groups of genes to regulate cellular function.
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Affiliation(s)
- Sneha Ramesh Mani
- Yale Stem Cell Center, Yale University, New Haven, Connecticut 06520, USA
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Rozhkov NV, Hammell M, Hannon GJ. Multiple roles for Piwi in silencing Drosophila transposons. Genes Dev 2013; 27:400-12. [PMID: 23392609 DOI: 10.1101/gad.209767.112] [Citation(s) in RCA: 200] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Silencing of transposons in the Drosophila ovary relies on three Piwi family proteins--Piwi, Aubergine (Aub), and Ago3--acting in concert with their small RNA guides, the Piwi-interacting RNAs (piRNAs). Aub and Ago3 are found in the germ cell cytoplasm, where they function in the ping-pong cycle to consume transposon mRNAs. The nuclear Piwi protein is required for transposon silencing in both germ and somatic follicle cells, yet the precise mechanisms by which Piwi acts remain largely unclear. We investigated the role of Piwi by combining cell type-specific knockdowns with measurements of steady-state transposon mRNA levels, nascent RNA synthesis, chromatin state, and small RNA abundance. In somatic cells, Piwi loss led to concerted effects on nascent transcripts and transposon mRNAs, indicating that Piwi acts through transcriptional gene silencing (TGS). In germ cells, Piwi loss showed disproportionate impacts on steady-state RNA levels, indicating that it also exerts an effect on post-transcriptional gene silencing (PTGS). Piwi knockdown affected levels of germ cell piRNAs presumably bound to Aub and Ago3, perhaps explaining its post-transcriptional impacts. Overall, our results indicate that Piwi plays multiple roles in the piRNA pathway, in part enforcing transposon repression through effects on local chromatin states and transcription but also participating in germ cell piRNA biogenesis.
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Affiliation(s)
- Nikolay V Rozhkov
- Watson School of Biological Sciences, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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Nefedova LN, Urusov FA, Romanova NI, Shmel’kova AO, Kim AI. Study of the transcriptional and transpositional activities of the Tirant Retrotransposon in Drosophila melanogaster strains mutant for the flamenco locus. RUSS J GENET+ 2012. [DOI: 10.1134/s1022795412110063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
The recent explosive growth of molecular genetic databases has yielded increasingly detailed insights into the evolutionary dynamics of eukaryotic genomes. DNA sequences with the self-encoded ability to transpose and replicate are unexpectedly abundant and widespread in eukaryotic genomes. They seem to be sexual parasites. By dispersing themselves among the chromosomes, they increase their transmission rates and can invade outcrossing populations despite reducing host fitness. Once established, molecular parasites may themselves be parasitized by other elements, and through selection for reduced virulence may become beneficial genes. Elements have been isolated at various stages in this progression, from transposons that regulate their own transposition rates, to fundamental components of eukaryotic cytology, such as telomeres.
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