1
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Gilliland WD, May DP, Bowen AO, Conger KO, Elrad D, Marciniak M, Mashburn SA, Presbitero G, Welk LF. A cytological F1 RNAi screen for defects in Drosophila melanogaster female meiosis. Genetics 2024; 227:iyae046. [PMID: 38531678 DOI: 10.1093/genetics/iyae046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 01/11/2024] [Accepted: 03/16/2024] [Indexed: 03/28/2024] Open
Abstract
Genetic screens for recessive alleles induce mutations, make the mutated chromosomes homozygous, and then assay those homozygotes for the phenotype of interest. When screening for genes required for female meiosis, the phenotype of interest has typically been nondisjunction from chromosome segregation errors. As this requires that mutant females be viable and fertile, any mutants that are lethal or sterile when homozygous cannot be recovered by this approach. To overcome these limitations, we have screened the VALIUM22 collection of RNAi constructs that target germline-expressing genes in a vector optimized for germline expression by driving RNAi with GAL4 under control of a germline-specific promoter (nanos or mat-alpha4). This allowed us to test genes that would be lethal if knocked down in all cells, and by examining unfertilized metaphase-arrested mature oocytes, we could identify defects in sterile females. After screening >1,450 lines of the collection for two different defects (chromosome congression and the hypoxic sequestration of Mps1-GFP to ooplasmic filaments), we obtained multiple hits for both phenotypes, identified novel meiotic phenotypes for genes that had been previously characterized in other processes, and identified the first phenotypes to be associated with several previously uncharacterized genes.
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Affiliation(s)
- William D Gilliland
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | - Dennis P May
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | - Amelia O Bowen
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | - Kelly O Conger
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | - Doreen Elrad
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | - Marcin Marciniak
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | - Sarah A Mashburn
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
| | | | - Lucas F Welk
- Department of Biological Sciences, DePaul University, Chicago, IL 60614, USA
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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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Ortolá B, Daròs JA. RNA Interference in Insects: From a Natural Mechanism of Gene Expression Regulation to a Biotechnological Crop Protection Promise. BIOLOGY 2024; 13:137. [PMID: 38534407 DOI: 10.3390/biology13030137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/14/2024] [Accepted: 02/19/2024] [Indexed: 03/28/2024]
Abstract
Insect pests rank among the major limiting factors in agricultural production worldwide. In addition to direct effect on crops, some phytophagous insects are efficient vectors for plant disease transmission. Large amounts of conventional insecticides are required to secure food production worldwide, with a high impact on the economy and environment, particularly when beneficial insects are also affected by chemicals that frequently lack the desired specificity. RNA interference (RNAi) is a natural mechanism gene expression regulation and protection against exogenous and endogenous genetic elements present in most eukaryotes, including insects. Molecules of double-stranded RNA (dsRNA) or highly structured RNA are the substrates of cellular enzymes to produce several types of small RNAs (sRNAs), which play a crucial role in targeting sequences for transcriptional or post-transcriptional gene silencing. The relatively simple rules that underlie RNAi regulation, mainly based in Watson-Crick complementarity, have facilitated biotechnological applications based on these cellular mechanisms. This includes the promise of using engineered dsRNA molecules, either endogenously produced in crop plants or exogenously synthesized and applied onto crops, as a new generation of highly specific, sustainable, and environmentally friendly insecticides. Fueled on this expectation, this article reviews current knowledge about the RNAi pathways in insects, and some other applied questions such as production and delivery of recombinant RNA, which are critical to establish RNAi as a reliable technology for insect control in crop plants.
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Affiliation(s)
- Beltrán Ortolá
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València, 46022 Valencia, Spain
| | - José-Antonio Daròs
- Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-Universitat Politècnica de València, 46022 Valencia, Spain
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4
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Sun S, Defosse T, Boyd A, Sop J, Verderose F, Surray D, Aziz M, Howland M, Wu S, Changela N, Jang J, Schindler K, Xing J, McKim KS. Whole transcriptome screening for novel genes involved in meiosis and fertility in Drosophila melanogaster. Sci Rep 2024; 14:3602. [PMID: 38351116 PMCID: PMC10864285 DOI: 10.1038/s41598-024-53346-z] [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: 05/30/2023] [Accepted: 01/31/2024] [Indexed: 02/16/2024] Open
Abstract
Reproductive success requires the development of viable oocytes and the accurate segregation of chromosomes during meiosis. Failure to segregate chromosomes properly can lead to infertility, miscarriages, or developmental disorders. A variety of factors contribute to accurate chromosome segregation and oocyte development, such as spindle assembly and sister chromatid cohesion. However, many proteins required for meiosis remain unknown. In this study, we aimed to develop a screening pipeline for identifying novel meiotic and fertility genes using the genome of Drosophila melanogaster. To accomplish this goal, genes upregulated within meiotically active tissues were identified. More than 240 genes with no known function were silenced using RNA interference (RNAi) and the effects on meiosis and fertility were assessed. We identified 94 genes that when silenced caused infertility and/or high levels of chromosomal nondisjunction. The vast majority of these genes have human and mouse homologs that are also poorly studied. Through this screening process, we identified novel genes that are crucial for meiosis and oocyte development but have not been extensively studied in human or model organisms. Understanding the function of these genes will be an important step towards the understanding of their biological significance during reproduction.
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Affiliation(s)
- Siqi Sun
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
| | - Tyler Defosse
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Ayla Boyd
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Joel Sop
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Faith Verderose
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Diya Surray
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Mark Aziz
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Margaret Howland
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Siwen Wu
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Neha Changela
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Janet Jang
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA
| | - Karen Schindler
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
- Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, 145 Bevier Road, Piscataway, NJ, 08854, USA
| | - Jinchuan Xing
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
- Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, 145 Bevier Road, Piscataway, NJ, 08854, USA.
| | - Kim S McKim
- Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, NJ, USA.
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ, 08854, USA.
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5
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Gilliland WD, May DP, Bowen AO, Conger KO, Elrad D, Marciniak M, Mashburn SA, Presbitero G, Welk LF. A Cytological F1 RNAi Screen for Defects in Drosophila melanogaster Female Meiosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.12.575435. [PMID: 38293152 PMCID: PMC10827134 DOI: 10.1101/2024.01.12.575435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Genetic screens for recessive alleles induce mutations, make the mutated chromosomes homozygous, and then assay those homozygotes for the phenotype of interest. When screening for genes required for female meiosis, the phenotype of interest has typically been nondisjunction from chromosome segregation errors. As this requires that mutant females be viable and fertile, any mutants that are lethal or sterile when homozygous cannot be recovered by this approach. To overcome these limitations, our lab has screened the VALIUM22 collection produced by the Harvard TRiP Project, which contains RNAi constructs targeting genes known to be expressed in the germline in a vector optimized for germline expression. By driving RNAi with GAL4 under control of a germline-specific promoter (nanos or mat-alpha4), we can test genes that would be lethal if knocked down in all cells, and by examining unfertilized metaphase-arrested mature oocytes, we can identify defects associated with genes whose knockdown results in sterility or causes other errors besides nondisjunction. We screened this collection to identify genes that disrupt either of two phenotypes when knocked down: the ability of meiotic chromosomes to congress to a single mass at the end of prometaphase, and the sequestration of Mps1-GFP to ooplasmic filaments in response to hypoxia. After screening >1450 lines of the collection, we obtained multiple hits for both phenotypes, identified novel meiotic phenotypes for genes that had been previously characterized in other processes, and identified the first phenotypes to be associated with several previously uncharacterized genes.
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Affiliation(s)
| | | | | | | | - Doreen Elrad
- DePaul University Department of Biological Sciences
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6
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Milyaeva PA, Kukushkina IV, Kim AI, Nefedova LN. Stress Induced Activation of LTR Retrotransposons in the Drosophila melanogaster Genome. Life (Basel) 2023; 13:2272. [PMID: 38137873 PMCID: PMC10745035 DOI: 10.3390/life13122272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 11/20/2023] [Accepted: 11/25/2023] [Indexed: 12/24/2023] Open
Abstract
Background: Retrotransposons with long terminal repeats (LTR retrotransposons) are widespread in all groups of eukaryotes and are often both the cause of new mutations and the source of new sequences. Apart from their high activity in generative and differentiation-stage tissues, LTR retrotransposons also become more active in response to different stressors. The precise causes of LTR retrotransposons' activation in response to stress, however, have not yet been thoroughly investigated. Methods: We used RT-PCR to investigate the transcriptional profile of LTR retrotransposons and piRNA clusters in response to oxidative and chronic heat stresses. We used Oxford Nanopore sequencing to investigate the genomic environment of new insertions of the retrotransposons. We used bioinformatics methods to find the stress-induced transcription factor binding sites in LTR retrotransposons. Results: We studied the transposition activity and transcription level of LTR retrotransposons in response to oxidative and chronic heat stress and assessed the contribution of various factors that can affect the increase in their expression under stress conditions: the state of the piRNA-interference system, the influence of the genomic environment on individual copies, and the presence of the stress-induced transcription factor binding sites in retrotransposon sequences. Conclusions: The main reason for the activation of LTR retrotransposons under stress conditions is the presence of transcription factor binding sites in their regulatory sequences, which are triggered in response to stress and are necessary for tissue regeneration processes. Stress-induced transposable element activation can function as a trigger mechanism, triggering multiple signal pathways and resulting in a polyvariant cell response.
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Affiliation(s)
- Polina A. Milyaeva
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (P.A.M.); (I.V.K.); (A.I.K.)
- Faculty of Biology, Shenzhen MSU-BIT University, Longgang District, Shenzhen 518172, China
| | - Inna V. Kukushkina
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (P.A.M.); (I.V.K.); (A.I.K.)
| | - Alexander I. Kim
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (P.A.M.); (I.V.K.); (A.I.K.)
- Faculty of Biology, Shenzhen MSU-BIT University, Longgang District, Shenzhen 518172, China
| | - Lidia N. Nefedova
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia; (P.A.M.); (I.V.K.); (A.I.K.)
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7
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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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8
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Lin Y, Suyama R, Kawaguchi S, Iki T, Kai T. Tejas functions as a core component in nuage assembly and precursor processing in Drosophila piRNA biogenesis. J Cell Biol 2023; 222:e202303125. [PMID: 37555815 PMCID: PMC10412688 DOI: 10.1083/jcb.202303125] [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: 03/27/2023] [Revised: 06/11/2023] [Accepted: 07/13/2023] [Indexed: 08/10/2023] Open
Abstract
PIWI-interacting RNAs (piRNAs), which protect genome from the attack by transposons, are produced and amplified in membraneless granules called nuage. In Drosophila, PIWI family proteins, Tudor-domain-containing (Tdrd) proteins, and RNA helicases are assembled and form nuage to ensure piRNA production. However, the molecular functions of the Tdrd protein Tejas (Tej) in piRNA biogenesis remain unknown. Here, we conduct a detailed analysis of the subcellular localization of fluorescently tagged nuage proteins and behavior of piRNA precursors. Our results demonstrate that Tej functions as a core component that recruits Vasa (Vas) and Spindle-E (Spn-E) into nuage granules through distinct motifs, thereby assembling nuage and engaging precursors for further processing. Our study also reveals that the low-complexity region of Tej regulates the mobility of Vas. Based on these results, we propose that Tej plays a pivotal role in piRNA precursor processing by assembling Vas and Spn-E into nuage and modulating the mobility of nuage components.
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Affiliation(s)
- Yuxuan Lin
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Ritsuko Suyama
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | | | - Taichiro Iki
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
| | - Toshie Kai
- Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
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9
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Ho S, Rice NP, Yu T, Weng Z, Theurkauf WE. Aub, Vasa and Armi localization to phase separated nuage is dispensable for piRNA biogenesis and transposon silencing in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.549160. [PMID: 37546958 PMCID: PMC10402007 DOI: 10.1101/2023.07.25.549160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
From nematodes to placental mammals, key components of the germline transposon silencing piRNAs pathway localize to phase separated perinuclear granules. In Drosophila, the PIWI protein Aub, DEAD box protein Vasa and helicase Armi localize to nuage granules and are required for ping-pong piRNA amplification and phased piRNA processing. Drosophila piRNA mutants lead to genome instability and Chk2 kinase DNA damage signaling. By systematically analyzing piRNA pathway organization, small RNA production, and long RNA expression in single piRNA mutants and corresponding chk2/mnk double mutants, we show that Chk2 activation disrupts nuage localization of Aub and Vasa, and that the HP1 homolog Rhino, which drives piRNA precursor transcription, is required for Aub, Vasa, and Armi localization to nuage. However, these studies also show that ping-pong amplification and phased piRNA biogenesis are independent of nuage localization of Vasa, Aub and Armi. Dispersed cytoplasmic proteins thus appear to mediate these essential piRNA pathway functions.
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Affiliation(s)
- Samantha Ho
- Program in Molecular Medicine, UMass Chan Medical School, Worcester MA
| | - Nicholas P Rice
- Program in Molecular Medicine, UMass Chan Medical School, Worcester MA
| | - Tianxiong Yu
- Program in Bioinformatics and Integrative Biology, UMass Chan Medical School, Worcester MA
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, UMass Chan Medical School, Worcester MA
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10
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Iki T, Kawaguchi S, Kai T. miRNA/siRNA-directed pathway to produce noncoding piRNAs from endogenous protein-coding regions ensures Drosophila spermatogenesis. SCIENCE ADVANCES 2023; 9:eadh0397. [PMID: 37467338 PMCID: PMC10355832 DOI: 10.1126/sciadv.adh0397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 06/16/2023] [Indexed: 07/21/2023]
Abstract
PIWI-interacting RNA (piRNA) pathways control transposable elements (TEs) and endogenous genes, playing important roles in animal gamete formation. However, the underlying piRNA biogenesis mechanisms remain elusive. Here, we show that endogenous protein coding sequences (CDSs), which are normally used for translation, serve as origins of noncoding piRNA biogenesis in Drosophila melanogaster testes. The product, namely, CDS-piRNAs, formed silencing complexes with Aubergine (Aub) in germ cells. Proximity proteome and functional analyses show that CDS-piRNAs and cluster/TE-piRNAs are distinct species occupying Aub, the former loading selectively relies on chaperone Cyclophilin 40. Moreover, Argonaute 2 (Ago2) and Dicer-2 activities were found critical for CDS-piRNA production. We provide evidence that Ago2-bound short interfering RNAs (siRNAs) and microRNAs (miRNAs) specify precursors to be processed into piRNAs. We further demonstrate that Aub is crucial in spermatid differentiation, regulating chromatins through mRNA cleavage. Collectively, our data illustrate a unique strategy used by male germ line, expanding piRNA repertoire for silencing of endogenous genes during spermatogenesis.
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Affiliation(s)
| | - Shinichi Kawaguchi
- Laboratory of Germline Biology, Graduate School of Frontier Biosciences, Osaka University, Yamadaoka1-3, Suita, Osaka, Japan
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11
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Casier K, Autaa J, Gueguen N, Delmarre V, Marie PP, Ronsseray S, Carré C, Brasset E, Teysset L, Boivin A. The histone demethylase Kdm3 prevents auto-immune piRNAs production in Drosophila. SCIENCE ADVANCES 2023; 9:eade3872. [PMID: 37027460 PMCID: PMC10081847 DOI: 10.1126/sciadv.ade3872] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 03/08/2023] [Indexed: 06/19/2023]
Abstract
Genome integrity of the animal germline is protected from transposable element activity by PIWI-interacting RNAs (piRNAs). While piRNA biogenesis is intensively explored, little is known about the genetical determination of piRNA clusters, the genomic sources of piRNAs. Using a bimodal epigenetic state piRNA cluster (BX2), we identified the histone demethylase Kdm3 as being able to prevent a cryptic piRNA production. In the absence of Kdm3, dozens of coding gene-containing regions become genuine germline dual-strand piRNA clusters. Eggs laid by Kdm3 mutant females show developmental defects phenocopying loss of function of genes embedded into the additional piRNA clusters, suggesting an inheritance of functional ovarian "auto-immune" piRNAs. Antagonizing piRNA cluster determination through chromatin modifications appears crucial to prevent auto-immune genic piRNAs production.
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Affiliation(s)
- Karine Casier
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Julie Autaa
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Nathalie Gueguen
- iGReD, CNRS, INSERM, Faculté de Médecine, Université Clermont Auvergne, 63000 Clermont-Ferrand, France
| | - Valérie Delmarre
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Pauline P. Marie
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Stéphane Ronsseray
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Clément Carré
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Emilie Brasset
- iGReD, CNRS, INSERM, Faculté de Médecine, Université Clermont Auvergne, 63000 Clermont-Ferrand, France
| | - Laure Teysset
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
| | - Antoine Boivin
- Transgenerational Epigenetics and Small RNA Biology, Sorbonne Université, CNRS, Institut de Biologie Paris-Seine, Laboratoire Biologie du Développement, UMR7622, F-75005 Paris, France
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12
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Qu J, Betting V, van Iterson R, Kwaschik FM, van Rij RP. Chromatin profiling identifies transcriptional readthrough as a conserved mechanism for piRNA biogenesis in mosquitoes. Cell Rep 2023; 42:112257. [PMID: 36930642 DOI: 10.1016/j.celrep.2023.112257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 12/21/2022] [Accepted: 02/27/2023] [Indexed: 03/18/2023] Open
Abstract
The piRNA pathway in mosquitoes differs substantially from other model organisms, with an expanded PIWI gene family and functions in antiviral defense. Here, we define core piRNA clusters as genomic loci that show ubiquitous piRNA expression in both somatic and germline tissues. These core piRNA clusters are enriched for non-retroviral endogenous viral elements (nrEVEs) in antisense orientation and depend on key biogenesis factors, Veneno, Tejas, Yb, and Shutdown. Combined transcriptome and chromatin state analyses identify transcriptional readthrough as a conserved mechanism for cluster-derived piRNA biogenesis in the vector mosquitoes Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and Anopheles gambiae. Comparative analyses between the two Aedes species suggest that piRNA clusters function as traps for nrEVEs, allowing adaptation to environmental challenges such as virus infection. Our systematic transcriptome and chromatin state analyses lay the foundation for studies of gene regulation, genome evolution, and piRNA function in these important vector species.
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Affiliation(s)
- Jieqiong Qu
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands
| | - Valerie Betting
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands
| | - Ruben van Iterson
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands
| | - Florence M Kwaschik
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands
| | - Ronald P van Rij
- Department of Medical Microbiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, the Netherlands.
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13
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Wang X, Ramat A, Simonelig M, Liu MF. Emerging roles and functional mechanisms of PIWI-interacting RNAs. Nat Rev Mol Cell Biol 2023; 24:123-141. [PMID: 36104626 DOI: 10.1038/s41580-022-00528-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2022] [Indexed: 02/02/2023]
Abstract
PIWI-interacting RNAs (piRNAs) are a class of small non-coding RNAs that associate with proteins of the PIWI clade of the Argonaute family. First identified in animal germ line cells, piRNAs have essential roles in germ line development. The first function of PIWI-piRNA complexes to be described was the silencing of transposable elements, which is crucial for maintaining the integrity of the germ line genome. Later studies provided new insights into the functions of PIWI-piRNA complexes by demonstrating that they regulate protein-coding genes. Recent studies of piRNA biology, including in new model organisms such as golden hamsters, have deepened our understanding of both piRNA biogenesis and piRNA function. In this Review, we discuss the most recent advances in our understanding of piRNA biogenesis, the molecular mechanisms of piRNA function and the emerging roles of piRNAs in germ line development mainly in flies and mice, and in infertility, cancer and neurological diseases in humans.
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Affiliation(s)
- Xin Wang
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China.,Key Laboratory of Systems Health Science of Zhejiang Province, School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, China
| | - Anne Ramat
- Institute of Human Genetics, University of Montpellier, CNRS, Montpellier, France
| | - Martine Simonelig
- Institute of Human Genetics, University of Montpellier, CNRS, Montpellier, France.
| | - Mo-Fang Liu
- State Key Laboratory of Molecular Biology, Shanghai Key Laboratory of Molecular Andrology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China. .,Key Laboratory of Systems Health Science of Zhejiang Province, School of Life Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, China. .,School of Life Science and Technology, Shanghai Tech University, Shanghai, China.
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14
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MacPherson RA, Shankar V, Sunkara LT, Hannah RC, Campbell MR, Anholt RRH, Mackay TFC. Pleiotropic fitness effects of the lncRNA Uhg4 in Drosophila melanogaster. BMC Genomics 2022; 23:781. [PMID: 36451091 PMCID: PMC9710044 DOI: 10.1186/s12864-022-08972-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 10/26/2022] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Long noncoding RNAs (lncRNAs) are a diverse class of RNAs that are critical for gene regulation, DNA repair, and splicing, and have been implicated in development, stress response, and cancer. However, the functions of many lncRNAs remain unknown. In Drosophila melanogaster, U snoRNA host gene 4 (Uhg4) encodes an antisense long noncoding RNA that is host to seven small nucleolar RNAs (snoRNAs). Uhg4 is expressed ubiquitously during development and in all adult tissues, with maximal expression in ovaries; however, it has no annotated function(s). RESULTS We used CRISPR-Cas9 germline gene editing to generate multiple deletions spanning the promoter region and first exon of Uhg4. Females showed arrested egg development and both males and females were sterile. In addition, Uhg4 deletion mutants showed delayed development and decreased viability, and changes in sleep and responses to stress. Whole-genome RNA sequencing of Uhg4 deletion flies and their controls identified co-regulated genes and genetic interaction networks associated with Uhg4. Gene ontology analyses highlighted a broad spectrum of biological processes, including regulation of transcription and translation, morphogenesis, and stress response. CONCLUSION Uhg4 is a lncRNA essential for reproduction with pleiotropic effects on multiple fitness traits.
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Affiliation(s)
- Rebecca A MacPherson
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, 29646, USA
| | - Vijay Shankar
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, 29646, USA
| | - Lakshmi T Sunkara
- Present adress: Clemson Veterinary Diagnostic Center, Livestock Poultry Health, Clemson University, 500 Clemson Road, Columbia, SC, 29229, USA
| | - Rachel C Hannah
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, 29646, USA
| | - Marion R Campbell
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, 29646, USA
| | - Robert R H Anholt
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, 29646, USA.
| | - Trudy F C Mackay
- Center for Human Genetics and Department of Genetics and Biochemistry, Clemson University, 114 Gregor Mendel Circle, Greenwood, SC, 29646, USA.
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15
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Baumgartner L, Handler D, Platzer SW, Yu C, Duchek P, Brennecke J. The Drosophila ZAD zinc finger protein Kipferl guides Rhino to piRNA clusters. eLife 2022; 11:80067. [PMID: 36193674 PMCID: PMC9531945 DOI: 10.7554/elife.80067] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 08/11/2022] [Indexed: 12/15/2022] Open
Abstract
RNA interference systems depend on the synthesis of small RNA precursors whose sequences define the target spectrum of these silencing pathways. The Drosophila Heterochromatin Protein 1 (HP1) variant Rhino permits transcription of PIWI-interacting RNA (piRNA) precursors within transposon-rich heterochromatic loci in germline cells. Current models propose that Rhino’s specific chromatin occupancy at piRNA source loci is determined by histone marks and maternally inherited piRNAs, but also imply the existence of other, undiscovered specificity cues. Here, we identify a member of the diverse family of zinc finger associated domain (ZAD)-C2H2 zinc finger proteins, Kipferl, as critical Rhino cofactor in ovaries. By binding to guanosine-rich DNA motifs and interacting with the Rhino chromodomain, Kipferl recruits Rhino to specific loci and stabilizes it on chromatin. In kipferl mutant flies, Rhino is lost from most of its target chromatin loci and instead accumulates on pericentromeric Satellite arrays, resulting in decreased levels of transposon targeting piRNAs and impaired fertility. Our findings reveal that DNA sequence, in addition to the H3K9me3 mark, determines the identity of piRNA source loci and provide insight into how Rhino might be caught in the crossfire of genetic conflicts. The genes within our DNA encode the essentials of our body plan and how each task in the body is achieved. However, our genome also contains many repetitive regions of DNA that do not encode functional genes. Some of these regions are genetic parasites known as transposons that try to multiply and spread around the DNA of their host. To prevent transposon DNA from interfering with the way the body operates, humans and other animals have evolved elaborate defense mechanisms to identify transposons and prevent them from multiplying. In one such mechanism, known as the piRNA pathway, the host makes small molecules known as piRNAs that have sequences complementary to those of transposons, and act as guides to silence the transposons. The instructions to make these piRNAs are stored in the form of transposon fragments in dedicated regions of host DNA called piRNA clusters. These clusters thereby act as genetic memory, allowing the host to recognize and silence specific transposons in other locations within the host’s genome. In fruit flies, a protein called Rhino binds to piRNA clusters that are densely packed to allow piRNAs to be made. However, it remained unclear how Rhino is able to identify and bind to piRNA clusters, but not to other similarly densely packed regions of DNA. Baumgartner et al. used a combination of genetic, genomic, and imaging approaches to study how Rhino finds its way in the fruit fly genome. They found that another protein called Kipferl interacts with Rhino and is required for Rhino to bind to nearly all piRNA clusters. Since Kipferl can by itself bind to the sequences that Rhino needs to find, the results suggest that Kipferl acts to recruit and initiate Rhino binding within densely packed piRNA clusters. Further experiments found that, in flies lacking Kipferl, Rhino binds to regions of DNA called Satellite repeats, hinting that these selfish sequences may compete for Rhino for their own benefit. The finding that Kipferl and Rhino work together to define the memory system of the piRNA pathway strongly advances our understanding of how a sequence-specific defense system based on small RNAs can be established.
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Affiliation(s)
- Lisa Baumgartner
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria.,Vienna BioCenter PhD Program, Doctoral School of the University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Dominik Handler
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
| | - Sebastian Wolfgang Platzer
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
| | - Changwei Yu
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
| | - Peter Duchek
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
| | - Julius Brennecke
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna BioCenter, Vienna, Austria
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16
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Sending the message: specialized RNA export mechanisms in trypanosomes. Trends Parasitol 2022; 38:854-867. [PMID: 36028415 PMCID: PMC9894534 DOI: 10.1016/j.pt.2022.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 07/25/2022] [Accepted: 07/25/2022] [Indexed: 02/04/2023]
Abstract
Export of RNA from the nucleus is essential for all eukaryotic cells and has emerged as a major step in the control of gene expression. mRNA molecules are required to complete a complex series of processing events and pass a quality control system to protect the cytoplasm from the translation of aberrant proteins. Many of these events are highly conserved across eukaryotes, reflecting their ancient origin, but significant deviation from a canonical pathway as described from animals and fungi has emerged in the trypanosomatids. With significant implications for the mechanisms that control gene expression and hence differentiation, responses to altered environments and fitness as a parasite, these deviations may also reveal additional, previously unsuspected, mRNA export pathways.
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17
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Di Stefano L. All Quiet on the TE Front? The Role of Chromatin in Transposable Element Silencing. Cells 2022; 11:cells11162501. [PMID: 36010577 PMCID: PMC9406493 DOI: 10.3390/cells11162501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 07/27/2022] [Accepted: 08/03/2022] [Indexed: 01/09/2023] Open
Abstract
Transposable elements (TEs) are mobile genetic elements that constitute a sizeable portion of many eukaryotic genomes. Through their mobility, they represent a major source of genetic variation, and their activation can cause genetic instability and has been linked to aging, cancer and neurodegenerative diseases. Accordingly, tight regulation of TE transcription is necessary for normal development. Chromatin is at the heart of TE regulation; however, we still lack a comprehensive understanding of the precise role of chromatin marks in TE silencing and how chromatin marks are established and maintained at TE loci. In this review, I discuss evidence documenting the contribution of chromatin-associated proteins and histone marks in TE regulation across different species with an emphasis on Drosophila and mammalian systems.
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Affiliation(s)
- Luisa Di Stefano
- Molecular, Cellular and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), University of Toulouse, CNRS, UPS, 31062 Toulouse, France
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18
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Chattopadhyay T, Biswal P, Lalruatfela A, Mallick B. Emerging roles of PIWI-interacting RNAs (piRNAs) and PIWI proteins in head and neck cancer and their potential clinical implications. Biochim Biophys Acta Rev Cancer 2022; 1877:188772. [PMID: 35931391 DOI: 10.1016/j.bbcan.2022.188772] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 07/29/2022] [Accepted: 07/29/2022] [Indexed: 02/08/2023]
Abstract
Head and neck squamous cell carcinoma (HNSCC) are among the well-known neoplasms originating in the oral cavity, pharynx, and larynx. Despite advancements in chemotherapy, radiotherapy, and surgery, the survival rates of the patients are low, which has posed a major therapeutic challenge. A growing number of non-coding RNAs (ncRNAs), for instance, microRNAs, have been identified whose abnormal expression patterns have been implicated in HNSCC. However, more recently, several seminal research has shown that piwi-interacting RNAs (piRNAs), a promising and young class of small ncRNA, are linked to the emergence and progression of cancer. They can regulate transposable elements (TE) and gene expression through multiple mechanisms, making them potentially more powerful regulators than miRNAs. Hence, they can be more promising ncRNAs candidates for cancer therapeutic intervention. Here, we surveyed the roles and clinical implications of piRNAs and their PIWI proteins partners in tumorigenesis and associated molecular processes of cancer, with a particular focus on HNSCC, to offer a new avenue for diagnosis, prognosis, and therapeutic interventions for the malignancy, improving patient's outcomes.
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Affiliation(s)
- Trisha Chattopadhyay
- RNAi and Functional Genomics Lab., Department of Life Science, National Institute of Technology, Rourkela 769008, Odisha, India
| | - Priyajit Biswal
- RNAi and Functional Genomics Lab., Department of Life Science, National Institute of Technology, Rourkela 769008, Odisha, India
| | - Anthony Lalruatfela
- RNAi and Functional Genomics Lab., Department of Life Science, National Institute of Technology, Rourkela 769008, Odisha, India
| | - Bibekanand Mallick
- RNAi and Functional Genomics Lab., Department of Life Science, National Institute of Technology, Rourkela 769008, Odisha, India.
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19
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piRNA-guided intron removal from pre-mRNAs regulates density-dependent reproductive strategy. Cell Rep 2022; 39:110593. [PMID: 35476998 DOI: 10.1016/j.celrep.2022.110593] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 09/05/2021] [Accepted: 03/09/2022] [Indexed: 11/23/2022] Open
Abstract
Animal density-dependent experiences have profound effects on reproductive strategies with marked fecundity differences. Migratory locust adopts distinct population density-dependent reproductive strategies to cope with their respective life cycles, but the mechanisms remain poorly understood. Here, we report that Piwi-interacting RNAs (piRNAs) in the locust germline play key roles in this process. We find that the locust Piwi protein Liwi1 and piRNAs are highly expressed in early developing egg chambers in solitarious locusts, which have higher fecundity than gregarious locusts. Approximately 40% of solitarious locust-associated piRNAs map to protein-coding genes. We find that Liwi1/piRNAs facilitate pre-mRNA splicing of oocyte development-related genes, such as oo18 RNA-binding protein (Orb), in the germline by recruiting the splicing factor U2AF35 to piRNA-targeted introns, thereby increasing fecundity. Such piRNA-guided pre-mRNA splicing is also functional in Drosophila and mouse germ cells. We uncover a piRNA-guided splicing mechanism for processing reproduction-related mRNAs and determining animal reproductive strategies.
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20
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Saito K. Drosophila Genetic Resources for Elucidating piRNA Pathway. Methods Mol Biol 2022; 2509:135-141. [PMID: 35796961 DOI: 10.1007/978-1-0716-2380-0_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Emerging evidence indicates that PIWI proteins, in collaboration with PIWI-interacting RNAs (piRNAs), play a critical role in gonadal development and retrotransposon silencing in metazoans. Numerous studies have characterized the mechanism of retrotransposon silencing and identified dozens of factors involved in the piRNA pathways. Drosophila is an attractive model organism for piRNA studies due to its great availability of genetic tools and the low cost of maintenance. Here, I introduce Drosophila genetic resources and techniques valuable for studying piRNA pathway genes via their impact on retrotransposon silencing.
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Affiliation(s)
- Kuniaki Saito
- Invertebrate Genetics Laboratory, Department of Chromosome Science, National Institute of Genetics, Research Organization of Information and Systems (ROIS), Mishima, Shizuoka, Japan.
- Division of Invertebrate Genetics, Department of Genetics, The Graduate University for Advanced Studies (SOKENDAI), Mishima, Shizuoka, Japan.
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21
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To export, or not to export: how nuclear export factor variants resolve Piwi's dilemma. Biochem Soc Trans 2021; 49:2073-2079. [PMID: 34643228 DOI: 10.1042/bst20201171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 09/06/2021] [Accepted: 09/15/2021] [Indexed: 11/17/2022]
Abstract
Piwi-interacting RNAs (piRNAs) defend animal gonads by guiding PIWI-clade Argonaute proteins to silence transposons. The nuclear Piwi/piRNA complexes confer transcriptional repression of transposons, which is accompanied with heterochromatin formation at target loci. On the other hand, piRNA clusters, genomic loci that transcribe piRNA precursors composed of transposon fragments, are often recognized by piRNAs to define their heterochromatic identity. Therefore, Piwi/piRNA complexes must resolve this conundrum of silencing transposons while allowing the expression of piRNA precursors, at least in Drosophila germlines. This review is focused on recent advances how the piRNA pathway deals with this genetic conflict.
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22
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ElMaghraby MF, Tirian L, Senti KA, Meixner K, Brennecke J. A genetic toolkit for studying transposon control in the Drosophila melanogaster ovary. Genetics 2021; 220:6414620. [PMID: 34718559 PMCID: PMC8733420 DOI: 10.1093/genetics/iyab179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 09/19/2021] [Indexed: 11/12/2022] Open
Abstract
Argonaute proteins of the PIWI clade complexed with PIWI-interacting RNAs (piRNAs) protect the animal germline genome by silencing transposable elements. One of the leading experimental systems for studying piRNA biology is the Drosophila melanogaster ovary. In addition to classical mutagenesis, transgenic RNA interference (RNAi), which enables tissue-specific silencing of gene expression, plays a central role in piRNA research. Here, we establish a versatile toolkit focused on piRNA biology that combines germline transgenic RNAi, GFP marker lines for key proteins of the piRNA pathway, and reporter transgenes to establish genetic hierarchies. We compare constitutive, pan-germline RNAi with an equally potent transgenic RNAi system that is activated only after germ cell cyst formation. Stage-specific RNAi allows us to investigate the role of genes essential for germline cell survival, for example nuclear RNA export or the SUMOylation pathway, in piRNA-dependent and independent transposon silencing. Our work forms the basis for an expandable genetic toolkit provided by the Vienna Drosophila Resource Center.
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Affiliation(s)
- Mostafa F ElMaghraby
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria.,Vienna BioCenter PhD Program, Doctoral School at the University of Vienna and Medical University of Vienna, 1030 Vienna, Austria
| | - Laszlo Tirian
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Kirsten-André Senti
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Katharina Meixner
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
| | - Julius Brennecke
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Vienna BioCenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
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23
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Zhang G, Yu T, Parhad SS, Ho S, Weng Z, Theurkauf WE. piRNA-independent transposon silencing by the Drosophila THO complex. Dev Cell 2021; 56:2623-2635.e5. [PMID: 34547226 DOI: 10.1016/j.devcel.2021.08.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 06/18/2021] [Accepted: 08/27/2021] [Indexed: 12/19/2022]
Abstract
piRNAs guide Piwi/Panoramix-dependent H3K9me3 chromatin modification and transposon silencing during Drosophila germline development. The THO RNA export complex is composed of Hpr1, Tho2, and Thoc5-7. Null thoc7 mutations, which displace Thoc5 and Thoc6 from a Tho2-Hpr1 subcomplex, reduce expression of a subset of germline piRNAs and increase transposon expression, suggesting that THO silences transposons by promoting piRNA biogenesis. Here, we show that the thoc7-null mutant combination increases transposon transcription but does not reduce anti-sense piRNAs targeting half of the transcriptionally activated transposon families. These mutations also fail to reduce piRNA-guided H3K9me3 chromatin modification or block Panoramix-dependent silencing of a reporter transgene, and unspliced transposon transcripts co-precipitate with THO through a Piwi- and Panoramix-independent mechanism. Mutations in piwi also dominantly enhance germline defects associated with thoc7-null alleles. THO thus functions in a piRNA-independent transposon-silencing pathway, which acts cooperatively with Piwi to support germline development.
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Affiliation(s)
- Gen Zhang
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - Tianxiong Yu
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA; Department of Bioinformatics, School of Life Sciences and Technology, Tongji University, Shanghai, People's Republic of China
| | - Swapnil S Parhad
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - Samantha Ho
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA.
| | - William E Theurkauf
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA.
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24
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Chen P, Luo Y, Aravin AA. RDC complex executes a dynamic piRNA program during Drosophila spermatogenesis to safeguard male fertility. PLoS Genet 2021; 17:e1009591. [PMID: 34473737 PMCID: PMC8412364 DOI: 10.1371/journal.pgen.1009591] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 05/10/2021] [Indexed: 11/19/2022] Open
Abstract
piRNAs are small non-coding RNAs that guide the silencing of transposons and other targets in animal gonads. In Drosophila female germline, many piRNA source loci dubbed “piRNA clusters” lack hallmarks of active genes and exploit an alternative path for transcription, which relies on the Rhino-Deadlock-Cutoff (RDC) complex. RDC was thought to be absent in testis, so it remains to date unknown how piRNA cluster transcription is regulated in the male germline. We found that components of RDC complex are expressed in male germ cells during early spermatogenesis, from germline stem cells (GSCs) to early spermatocytes. RDC is essential for expression of dual-strand piRNA clusters and transposon silencing in testis; however, it is dispensable for expression of Y-linked Suppressor of Stellate piRNAs and therefore Stellate silencing. Despite intact Stellate repression, males lacking RDC exhibited compromised fertility accompanied by germline DNA damage and GSC loss. Thus, piRNA-guided repression is essential for normal spermatogenesis beyond Stellate silencing. While RDC associates with multiple piRNA clusters in GSCs and early spermatogonia, its localization changes in later stages as RDC concentrates on a single X-linked locus, AT-chX. Dynamic RDC localization is paralleled by changes in piRNA cluster expression, indicating that RDC executes a fluid piRNA program during different stages of spermatogenesis. These results disprove the common belief that RDC is dispensable for piRNA biogenesis in testis and uncover the unexpected, sexually dimorphic and dynamic behavior of a core piRNA pathway machinery. Large fractions of eukaryotic genomes are occupied by mobile genetic elements called transposons. Active transposons can move in the genome causing DNA damage and mutations, while inactive copies can contribute to chromosome organization and regulation of gene expression. Host cells employ several mechanisms to discriminate transposons from other genes and repress transposon activities. In germ cells, a conserved class of short RNAs called Piwi-interacting (pi)RNAs recognize target RNAs in both the nucleus and cytoplasm and then guide transposon repression by preventing their transcription and destroying their RNAs. piRNAs are encoded in extended genomic regions dubbed piRNA clusters. Previously, composition and regulation of piRNA clusters were studied in the female germline of fruit flies, where a nuclear protein complex, the RDC complex, was shown to promote non-canonical transcription of these regions. However, RDC was believed to be dispensable in males. Here, we showed that RDC is essential for transposon repression in males, and males lacking RDC exhibit compromised fertility and loss of germ cells. We found that RDC binds multiple piRNA clusters in early germ cells but concentrates on a single locus at later stages. Our results indicate dynamic regulation of loci that produce piRNAs and, therefore, piRNA targets throughout spermatogenesis.
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Affiliation(s)
- Peiwei Chen
- California Institute of Technology, Division of Biology and Biological Engineering, Pasadena, California, United States of America
- * E-mail: (PC); (AAA)
| | - Yicheng Luo
- California Institute of Technology, Division of Biology and Biological Engineering, Pasadena, California, United States of America
| | - Alexei A. Aravin
- California Institute of Technology, Division of Biology and Biological Engineering, Pasadena, California, United States of America
- * E-mail: (PC); (AAA)
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25
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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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26
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Eastwood EL, Jara KA, Bornelöv S, Munafò M, Frantzis V, Kneuss E, Barbar EJ, Czech B, Hannon GJ. Dimerisation of the PICTS complex via LC8/Cut-up drives co-transcriptional transposon silencing in Drosophila. eLife 2021; 10:e65557. [PMID: 33538693 PMCID: PMC7861614 DOI: 10.7554/elife.65557] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 01/04/2021] [Indexed: 12/16/2022] Open
Abstract
In animal gonads, the PIWI-interacting RNA (piRNA) pathway guards genome integrity in part through the co-transcriptional gene silencing of transposon insertions. In Drosophila ovaries, piRNA-loaded Piwi detects nascent transposon transcripts and instructs heterochromatin formation through the Panoramix-induced co-transcriptional silencing (PICTS) complex, containing Panoramix, Nxf2 and Nxt1. Here, we report that the highly conserved dynein light chain LC8/Cut-up (Ctp) is an essential component of the PICTS complex. Loss of Ctp results in transposon de-repression and a reduction in repressive chromatin marks specifically at transposon loci. In turn, Ctp can enforce transcriptional silencing when artificially recruited to RNA and DNA reporters. We show that Ctp drives dimerisation of the PICTS complex through its interaction with conserved motifs within Panoramix. Artificial dimerisation of Panoramix bypasses the necessity for its interaction with Ctp, demonstrating that conscription of a protein from a ubiquitous cellular machinery has fulfilled a fundamental requirement for a transposon silencing complex.
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Affiliation(s)
- Evelyn L Eastwood
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Kayla A Jara
- Department of Biochemistry and Biophysics, Oregon State UniversityCorvallisUnited States
| | - Susanne Bornelöv
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Marzia Munafò
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Vasileios Frantzis
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Emma Kneuss
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Elisar J Barbar
- Department of Biochemistry and Biophysics, Oregon State UniversityCorvallisUnited States
| | - Benjamin Czech
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
| | - Gregory J Hannon
- Cancer Research UK Cambridge Institute, University of Cambridge, Li Ka Shing CentreCambridgeUnited Kingdom
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27
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Ramat A, Simonelig M. Functions of PIWI Proteins in Gene Regulation: New Arrows Added to the piRNA Quiver. Trends Genet 2021; 37:188-200. [DOI: 10.1016/j.tig.2020.08.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Revised: 08/05/2020] [Accepted: 08/18/2020] [Indexed: 12/14/2022]
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28
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Ellison CE, Kagda MS, Cao W. Telomeric TART elements target the piRNA machinery in Drosophila. PLoS Biol 2020; 18:e3000689. [PMID: 33347429 PMCID: PMC7785250 DOI: 10.1371/journal.pbio.3000689] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 01/05/2021] [Accepted: 12/10/2020] [Indexed: 11/23/2022] Open
Abstract
Coevolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by reestablishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. The TART-A TE functions as an important component of Drosophila telomeres but has also reportedly inserted into the Drosophila melanogaster nuclear export factor gene nxf2. We find that, rather than inserting into nxf2, TART-A has actually captured a portion of nxf2 sequence. We show that TART-A produces abundant Piwi-interacting small RNAs (piRNAs), some of which are antisense to the nxf2 transcript, and that the TART-like region of nxf2 is evolving rapidly. Furthermore, in D. melanogaster, TART-A is present at higher copy numbers, and nxf2 shows reduced expression, compared to the closely related species Drosophila simulans. We propose that capturing nxf2 sequence allowed TART-A to target the nxf2 gene for piRNA-mediated repression and that these 2 elements are engaged in antagonistic coevolution despite the fact that TART-A is serving a critical role for its host genome. Co-evolution between transposable elements (TEs) and their hosts can be antagonistic, where TEs evolve to avoid silencing and the host responds by re-establishing TE suppression, or mutualistic, where TEs are co-opted to benefit their host. This study shows that a specialized Drosophila retrotransposon that functions as a telomere has captured a portion of a host piRNA gene which may allow it to evade silencing.
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Affiliation(s)
- Christopher E. Ellison
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
- * E-mail:
| | - Meenakshi S. Kagda
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Weihuan Cao
- Department of Genetics, Human Genetics Institute of New Jersey, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
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29
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Gamez S, Srivastav S, Akbari OS, Lau NC. Diverse Defenses: A Perspective Comparing Dipteran Piwi-piRNA Pathways. Cells 2020; 9:E2180. [PMID: 32992598 PMCID: PMC7601171 DOI: 10.3390/cells9102180] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/22/2020] [Accepted: 09/23/2020] [Indexed: 02/07/2023] Open
Abstract
Animals face the dual threat of virus infections hijacking cellular function and transposons proliferating in germline genomes. For insects, the deeply conserved RNA interference (RNAi) pathways and other chromatin regulators provide an important line of defense against both viruses and transposons. For example, this innate immune system displays adaptiveness to new invasions by generating cognate small RNAs for targeting gene silencing measures against the viral and genomic intruders. However, within the Dipteran clade of insects, Drosophilid fruit flies and Culicids mosquitoes have evolved several unique mechanistic aspects of their RNAi defenses to combat invading transposons and viruses, with the Piwi-piRNA arm of the RNAi pathways showing the greatest degree of novel evolution. Whereas central features of Piwi-piRNA pathways are conserved between Drosophilids and Culicids, multiple lineage-specific innovations have arisen that may reflect distinct genome composition differences and specific ecological and physiological features dividing these two branches of Dipterans. This perspective review focuses on the most recent findings illuminating the Piwi/piRNA pathway distinctions between fruit flies and mosquitoes, and raises open questions that need to be addressed in order to ameliorate human diseases caused by pathogenic viruses that mosquitoes transmit as vectors.
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Affiliation(s)
- Stephanie Gamez
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, CA 92093, USA; (S.G.); (O.S.A.)
| | - Satyam Srivastav
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853-2703, USA;
| | - Omar S. Akbari
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, CA 92093, USA; (S.G.); (O.S.A.)
| | - Nelson C. Lau
- Department of Biochemistry and Genome Science Institute, Boston University School of Medicine, Boston, MA 02118, USA
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Pippadpally S, Venkatesh T. Deciphering piRNA biogenesis through cytoplasmic granules, mitochondria and exosomes. Arch Biochem Biophys 2020; 695:108597. [PMID: 32976825 DOI: 10.1016/j.abb.2020.108597] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 09/16/2020] [Accepted: 09/19/2020] [Indexed: 12/31/2022]
Abstract
RNA systems biology is marked by a myriad of cellular processes mediated by small and long non-coding RNAs. Small non-coding RNAs include siRNAs (small interfering RNAs), miRNAs (microRNAs), tRFs(tRNA derived fragments), and piRNAs (PIWI-interacting RNAs). piRNAs are vital for the maintenance of the germ-line integrity and repress the transposons either transcriptionally or post-transcriptionally. Studies based on model organisms have shown that defects in the piRNA pathway exhibit impaired gametogenesis and loss of fertility. piRNA biogenesis is marked by transcription of precursor molecules and their subsequent processing in the cytoplasm to generate mature piRNAs. Their biogenesis is unique and complex, which involves non-canonical transcription and self-amplification mechanisms such as the ping-pong cycle. piRNA biogenesis is different in somatic and germ cells and involves the role of cytoplasmic granules in addition to mitochondria. In this review, we discuss the biogenesis and maturation of piRNAs in various cytoplasmic granules such as Yb and nuage bodies. Also, we review the role of P bodies, stress granules, and P granules, and membrane-bound compartments such as mitochondria and exosomes in piRNA biogenesis.
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Affiliation(s)
- Srikanth Pippadpally
- Department of Biochemistry and Molecular Biology, Central University of Kerala, Kasargod, 671316, India
| | - Thejaswini Venkatesh
- Department of Biochemistry and Molecular Biology, Central University of Kerala, Kasargod, 671316, India.
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31
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SATO K, SIOMI MC. The piRNA pathway in Drosophila ovarian germ and somatic cells. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2020; 96:32-42. [PMID: 31932527 PMCID: PMC6974405 DOI: 10.2183/pjab.96.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 10/28/2019] [Indexed: 05/30/2023]
Abstract
RNA silencing refers to gene silencing pathways mediated by small non-coding RNAs, including microRNAs. Piwi-interacting RNAs (piRNAs) constitute the largest class of small non-coding RNAs in animal gonads, which repress transposons to protect the germline genome from the selfish invasion of transposons. Deterioration of the system causes DNA damage, leading to severe defects in gametogenesis and infertility. Studies using Drosophila ovaries show that piRNAs originate from specific genomic loci, termed piRNA clusters, and that in piRNA biogenesis, cluster transcripts are processed into mature piRNAs via three distinct pathways: initiator or responder for ping-pong piRNAs and trailing for phased piRNAs. piRNAs then assemble with PIWI members of the Argonaute family of proteins to form piRNA-induced RNA silencing complexes (piRISCs), the core engine of the piRNA-mediated silencing pathway. Upon piRISC assembly, the PIWI member, Piwi, is translocated to the nucleus and represses transposons co-transcriptionally by inducing local heterochromatin formation at target transposon loci.
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Affiliation(s)
- Kaoru SATO
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Mikiko C. SIOMI
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan
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32
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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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33
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Casier K, Boivin A, Carré C, Teysset L. Environmentally-Induced Transgenerational Epigenetic Inheritance: Implication of PIWI Interacting RNAs. Cells 2019; 8:cells8091108. [PMID: 31546882 PMCID: PMC6770481 DOI: 10.3390/cells8091108] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 09/16/2019] [Accepted: 09/17/2019] [Indexed: 12/11/2022] Open
Abstract
Environmentally-induced transgenerational epigenetic inheritance is an emerging field. The understanding of associated epigenetic mechanisms is currently in progress with open questions still remaining. In this review, we present an overview of the knowledge of environmentally-induced transgenerational inheritance and associated epigenetic mechanisms, mainly in animals. The second part focuses on the role of PIWI-interacting RNAs (piRNAs), a class of small RNAs involved in the maintenance of the germline genome, in epigenetic memory to put into perspective cases of environmentally-induced transgenerational inheritance involving piRNA production. Finally, the last part addresses how genomes are facing production of new piRNAs, and from a broader perspective, how this process might have consequences on evolution and on sporadic disease development.
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Affiliation(s)
- Karine Casier
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| | - Antoine Boivin
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| | - Clément Carré
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
| | - Laure Teysset
- Transgenerational Epigenetics & small RNA Biology, Sorbonne Université, CNRS, Laboratoire Biologie du Développement, Institut de Biologie Paris-Seine, UMR7622, 75005 Paris, France.
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34
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Abstract
RNA export is tightly coupled to splicing in metazoans. In the Drosophila germline, precursors for the majority of Piwi-interacting RNAs (piRNAs) are unspliced. In this issue of Genes & Development, Kneuss and colleagues (pp. 1208-1220) identify Nxf3 as a novel germline-specific export adapter for such unspliced transcripts. Their findings reveal the sequence of events leading from its role at the site of transcription to delivery of the cargo to cytoplasmic piRNA biogenesis sites.
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Affiliation(s)
- Mateusz Mendel
- Department of Molecular Biology, Science III, University of Geneva, CH-1211 Geneva 4, Switzerland
| | - Ramesh S Pillai
- Department of Molecular Biology, Science III, University of Geneva, CH-1211 Geneva 4, Switzerland
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