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Jouravleva K, Golovenko D, Demo G, Dutcher RC, Hall TMT, Zamore PD, Korostelev AA. Structural basis of microRNA biogenesis by Dicer-1 and its partner protein Loqs-PB. Mol Cell 2022; 82:4049-4063.e6. [PMID: 36182693 PMCID: PMC9637774 DOI: 10.1016/j.molcel.2022.09.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 06/24/2022] [Accepted: 08/31/2022] [Indexed: 12/22/2022]
Abstract
In animals and plants, Dicer enzymes collaborate with double-stranded RNA-binding domain (dsRBD) proteins to convert precursor-microRNAs (pre-miRNAs) into miRNA duplexes. We report six cryo-EM structures of Drosophila Dicer-1 that show how Dicer-1 and its partner Loqs‑PB cooperate (1) before binding pre-miRNA, (2) after binding and in a catalytically competent state, (3) after nicking one arm of the pre-miRNA, and (4) following complete dicing and initial product release. Our reconstructions suggest that pre-miRNA binds a rare, open conformation of the Dicer‑1⋅Loqs‑PB heterodimer. The Dicer-1 dsRBD and three Loqs‑PB dsRBDs form a tight belt around the pre-miRNA, distorting the RNA helix to place the scissile phosphodiester bonds in the RNase III active sites. Pre-miRNA cleavage shifts the dsRBDs and partially closes Dicer-1, which may promote product release. Our data suggest a model for how the Dicer‑1⋅Loqs‑PB complex affects a complete cycle of pre-miRNA recognition, stepwise endonuclease cleavage, and product release.
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Affiliation(s)
- Karina Jouravleva
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, 368 Plantation Street, Worcester, MA 01605, USA
| | - Dmitrij Golovenko
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, 368 Plantation Street, Worcester, MA 01605, USA
| | - Gabriel Demo
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, 368 Plantation Street, Worcester, MA 01605, USA; Central European Institute of Technology, Masaryk University, Kamenice 5, Brno 62500, Czech Republic
| | - Robert C Dutcher
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA
| | - Traci M Tanaka Hall
- Epigenetics and Stem Cell Biology Laboratory, National Institute of Environmental Health Sciences, National Institutes of Health, 111 T.W. Alexander Drive, Research Triangle Park, NC 27709, USA.
| | - Phillip D Zamore
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, 368 Plantation Street, Worcester, MA 01605, USA; Howard Hughes Medical Institute, University of Massachusetts Chan Medical School, 368 Plantation Street, Worcester, MA 01605, USA.
| | - Andrei A Korostelev
- RNA Therapeutics Institute, University of Massachusetts Chan Medical School, 368 Plantation Street, Worcester, MA 01605, USA.
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2
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The Aedes aegypti siRNA pathway mediates broad-spectrum defense against human pathogenic viruses and modulates antibacterial and antifungal defenses. PLoS Biol 2022; 20:e3001668. [PMID: 35679279 PMCID: PMC9182253 DOI: 10.1371/journal.pbio.3001668] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 05/11/2022] [Indexed: 01/08/2023] Open
Abstract
The mosquito’s innate immune system defends against a variety of pathogens, and the conserved siRNA pathway plays a central role in the control of viral infections. Here, we show that transgenic overexpression of Dicer2 (Dcr2) or R2d2 resulted in an accumulation of 21-nucleotide viral sequences that was accompanied by a significant suppression of dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) replication, thus indicating the broad-spectrum antiviral response mediated by the siRNA pathway that can be applied for the development of novel arbovirus control strategies. Interestingly, overexpression of Dcr2 or R2d2 regulated the mRNA abundance of a variety of antimicrobial immune genes, pointing to additional functions of DCR2 and R2D2 as well as cross-talk between the siRNA pathway and other immune pathways. Accordingly, transgenic overexpression of Dcr2 or R2d2 resulted in a lesser proliferation of the midgut microbiota and increased resistance to bacterial and fungal infections. This study shows that transgenic overexpression of siRNA pathway factors in mosquitoes mediates a broad-spectrum antiviral action against human pathogenic viruses such as dengue, Zika and Chikungunya virus, with implications for novel arbovirus control strategies; the siRNA pathway also regulates antimicrobial immune responses against bacterial and fungal infections.
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3
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Gestuveo RJ, Parry R, Dickson LB, Lequime S, Sreenu VB, Arnold MJ, Khromykh AA, Schnettler E, Lambrechts L, Varjak M, Kohl A. Mutational analysis of Aedes aegypti Dicer 2 provides insights into the biogenesis of antiviral exogenous small interfering RNAs. PLoS Pathog 2022; 18:e1010202. [PMID: 34990484 PMCID: PMC8769306 DOI: 10.1371/journal.ppat.1010202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 01/19/2022] [Accepted: 12/15/2021] [Indexed: 12/13/2022] Open
Abstract
The exogenous small interfering RNA (exo-siRNA) pathway is a key antiviral mechanism in the Aedes aegypti mosquito, a widely distributed vector of human-pathogenic arboviruses. This pathway is induced by virus-derived double-stranded RNAs (dsRNA) that are cleaved by the ribonuclease Dicer 2 (Dcr2) into predominantly 21 nucleotide (nt) virus-derived small interfering RNAs (vsiRNAs). These vsiRNAs are used by the effector protein Argonaute 2 within the RNA-induced silencing complex to cleave target viral RNA. Dcr2 contains several domains crucial for its activities, including helicase and RNase III domains. In Drosophila melanogaster Dcr2, the helicase domain has been associated with binding to dsRNA with blunt-ended termini and a processive siRNA production mechanism, while the platform-PAZ domains bind dsRNA with 3’ overhangs and subsequent distributive siRNA production. Here we analyzed the contributions of the helicase and RNase III domains in Ae. aegypti Dcr2 to antiviral activity and to the exo-siRNA pathway. Conserved amino acids in the helicase and RNase III domains were identified to investigate Dcr2 antiviral activity in an Ae. aegypti-derived Dcr2 knockout cell line by reporter assays and infection with mosquito-borne Semliki Forest virus (Togaviridae, Alphavirus). Functionally relevant amino acids were found to be conserved in haplotype Dcr2 sequences from field-derived Ae. aegypti across different continents. The helicase and RNase III domains were critical for silencing activity and 21 nt vsiRNA production, with RNase III domain activity alone determined to be insufficient for antiviral activity. Analysis of 21 nt vsiRNA sequences (produced by functional Dcr2) to assess the distribution and phasing along the viral genome revealed diverse yet highly consistent vsiRNA pools, with predominantly short or long sequence overlaps including 19 nt overlaps (the latter representing most likely true Dcr2 cleavage products). Combined with the importance of the Dcr2 helicase domain, this suggests that the majority of 21 nt vsiRNAs originate by processive cleavage. This study sheds new light on Ae. aegypti Dcr2 functions and properties in this important arbovirus vector species. Aedes aegypti mosquitoes that transmit human-pathogenic viruses rely on the exogenous small interfering RNA (exo-siRNA) pathway as part of antiviral responses. This pathway is triggered by virus-derived double-stranded RNA (dsRNA) produced during viral replication that is then cleaved by Dicer 2 (Dcr2) into virus-derived small interfering RNAs (vsiRNAs). These vsiRNAs target viral RNA, leading to suppression of viral replication. The importance of Dcr2 in this pathway has been intensely studied in the Drosophila melanogaster model but is largely lacking in mosquitoes. Here, we have identified conserved and functionally relevant amino acids in the helicase and RNase III domains of Ae. aegypti Dcr2 that are important in its silencing activity and antiviral responses against Semliki Forest virus (SFV). Small RNA sequencing of SFV-infected mosquito cells with functional or mutated Dcr2 gave new insights into the nature and origin of vsiRNAs. The findings of this study, together with the different molecular tools we have previously developed to investigate the exo-siRNA pathway of mosquito cells, have started to uncover important properties of Dcr2 that could be valuable in understanding mosquito-arbovirus interactions and potentially in developing or assisting vector control strategies.
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Affiliation(s)
- Rommel J. Gestuveo
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- Division of Biological Sciences, University of the Philippines Visayas, Miagao, Iloilo, Philippines
- * E-mail: (R.J.G.); (M.V.); (A.K.)
| | - Rhys Parry
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Australia
| | - Laura B. Dickson
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas, United States of America
- Institute for Human Infection and Immunity, University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Sebastian Lequime
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
- Cluster of Microbial Ecology, Groningen Institute for Evolutionary Life Sciences, Groningen, The Netherlands
| | | | - Matthew J. Arnold
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Alexander A. Khromykh
- School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, Australia
- Australian Infectious Diseases Research Centre, Global Virus Network Centre of Excellence, Brisbane, Queensland, Australia
| | - Esther Schnettler
- Bernhard-Nocht-Institute for Tropical Medicine, Hamburg, Germany
- German Centre for Infection Research (DZIF), Partner Site Hamburg-Luebeck-Borstel-Riems, Hamburg, Germany
- Faculty of Mathematics, Informatics and Natural Sciences, University Hamburg, Hamburg, Germany
| | - Louis Lambrechts
- Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France
| | - Margus Varjak
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- Institute of Technology, University of Tartu, Tartu, Estonia
- * E-mail: (R.J.G.); (M.V.); (A.K.)
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- * E-mail: (R.J.G.); (M.V.); (A.K.)
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4
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The Significance of the DUF283 Domain for the Activity of Human Ribonuclease Dicer. Int J Mol Sci 2021; 22:ijms22168690. [PMID: 34445396 PMCID: PMC8395393 DOI: 10.3390/ijms22168690] [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: 07/05/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 01/22/2023] Open
Abstract
Dicers are multidomain proteins, usually comprising an amino-terminal putative helicase domain, a DUF283 domain (domain of unknown function), a PAZ domain, two RNase III domains (RNase IIIa and RNase IIIb) and a dsRNA-binding domain. Dicer homologs play an important role in the biogenesis of small regulatory RNAs by cleaving single-stranded precursors adopting stem-loop structures (pre-miRNAs) and double-strand RNAs into short RNA duplexes containing functional microRNAs or small interfering RNAs, respectively. Growing evidence shows that apart from the canonical role, Dicer proteins can serve a number of other functions. For example, results of our previous studies showed that human Dicer (hDicer), presumably through its DUF283 domain, can facilitate hybridization between two complementary RNAs, thus, acting as a nucleic acid annealer. Here, to test this assumption, we prepared a hDicer deletion variant lacking the amino acid residues 625-752 corresponding to the DUF283 domain. The respective 128-amino acid fragment of hDicer was earlier demonstrated to accelerate base-pairing between two complementary RNAs in vitro. We show that the ΔDUF(625-752) hDicer variant loses the potential to facilitate RNA-RNA base pairing, which strongly proves our hypothesis about the importance of the DUF283 domain for the RNA-RNA annealing activity of hDicer. Interestingly, the in vitro biochemical characterization of the obtained deletion variant reveals that it displays different RNA cleavage properties depending on the pre-miRNA substrate.
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5
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Genetic Insight into the Domain Structure and Functions of Dicer-Type Ribonucleases. Int J Mol Sci 2021; 22:ijms22020616. [PMID: 33435485 PMCID: PMC7827160 DOI: 10.3390/ijms22020616] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/05/2021] [Accepted: 01/06/2021] [Indexed: 12/12/2022] Open
Abstract
Ribonuclease Dicer belongs to the family of RNase III endoribonucleases, the enzymes that specifically hydrolyze phosphodiester bonds found in double-stranded regions of RNAs. Dicer enzymes are mostly known for their essential role in the biogenesis of small regulatory RNAs. A typical Dicer-type RNase consists of a helicase domain, a domain of unknown function (DUF283), a PAZ (Piwi-Argonaute-Zwille) domain, two RNase III domains, and a double-stranded RNA binding domain; however, the domain composition of Dicers varies among species. Dicer and its homologues developed only in eukaryotes; nevertheless, the two enzymatic domains of Dicer, helicase and RNase III, display high sequence similarity to their prokaryotic orthologs. Evolutionary studies indicate that a combination of the helicase and RNase III domains in a single protein is a eukaryotic signature and is supposed to be one of the critical events that triggered the consolidation of the eukaryotic RNA interference. In this review, we provide the genetic insight into the domain organization and structure of Dicer proteins found in vertebrate and invertebrate animals, plants and fungi. We also discuss, in the context of the individual domains, domain deletion variants and partner proteins, a variety of Dicers’ functions not only related to small RNA biogenesis pathways.
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6
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Arraes FBM, Martins-de-Sa D, Noriega Vasquez DD, Melo BP, Faheem M, de Macedo LLP, Morgante CV, Barbosa JARG, Togawa RC, Moreira VJV, Danchin EGJ, Grossi-de-Sa MF. Dissecting protein domain variability in the core RNA interference machinery of five insect orders. RNA Biol 2020; 18:1653-1681. [PMID: 33302789 DOI: 10.1080/15476286.2020.1861816] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
RNA interference (RNAi)-mediated gene silencing can be used to control specific insect pest populations. Unfortunately, the variable efficiency in the knockdown levels of target genes has narrowed the applicability of this technology to a few species. Here, we examine the current state of knowledge regarding the miRNA (micro RNA) and siRNA (small interfering RNA) pathways in insects and investigate the structural variability at key protein domains of the RNAi machinery. Our goal was to correlate domain variability with mechanisms affecting the gene silencing efficiency. To this end, the protein domains of 168 insect species, encompassing the orders Coleoptera, Diptera, Hemiptera, Hymenoptera, and Lepidoptera, were analysed using our pipeline, which takes advantage of meticulous structure-based sequence alignments. We used phylogenetic inference and the evolutionary rate coefficient (K) to outline the variability across domain regions and surfaces. Our results show that four domains, namely dsrm, Helicase, PAZ and Ribonuclease III, are the main contributors of protein variability in the RNAi machinery across different insect orders. We discuss the potential roles of these domains in regulating RNAi-mediated gene silencing and the role of loop regions in fine-tuning RNAi efficiency. Additionally, we identified several order-specific singularities which indicate that lepidopterans have evolved differently from other insect orders, possibly due to constant coevolution with plants and viruses. In conclusion, our results highlight several variability hotspots that deserve further investigation in order to improve the application of RNAi technology in the control of insect pests.
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Affiliation(s)
| | - Diogo Martins-de-Sa
- Departamento De Biologia Celular, Universidade De Brasília, Brasília-DF, Brazil
| | - Daniel D Noriega Vasquez
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Catholic University of Brasília, Brasília-DF, Brazil
| | - Bruno Paes Melo
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Viçosa University, UFV, Viçosa-MG, Brazil
| | - Muhammad Faheem
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Department of Biological Sciences, National University of Medical Sciences, Punjab, Pakistan
| | | | - Carolina Vianna Morgante
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Embrapa Semiarid, Petrolina-PE, Brazil.,National Institute of Science and Technology, Jakarta Embrapa-Brazil
| | | | - Roberto Coiti Togawa
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil
| | - Valdeir Junio Vaz Moreira
- Biotechnology Center, Brazil.,Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Departamento De Biologia Celular, Universidade De Brasília, Brasília-DF, Brazil
| | - Etienne G J Danchin
- National Institute of Science and Technology, Jakarta Embrapa-Brazil.,INRAE, Université Côte d'Azur, CNRS, Institut Sophia Agrobiotech, Sophia-Antipolis, France
| | - Maria Fatima Grossi-de-Sa
- Plant-Pest Molecular Interaction Laboratory (LIMPP), Brasilia, Brasília-DF, Brazil.,Catholic University of Brasília, Brasília-DF, Brazil.,National Institute of Science and Technology, Jakarta Embrapa-Brazil
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7
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Hansen SR, Aderounmu AM, Donelick HM, Bass BL. Dicer's Helicase Domain: A Meeting Place for Regulatory Proteins. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2020; 84:185-193. [PMID: 32179591 PMCID: PMC7384945 DOI: 10.1101/sqb.2019.84.039750] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The function of Dicer’s helicase domain has been enigmatic since its discovery. Why do only some Dicers require ATP, despite a high degree of sequence conservation in their helicase domains? We discuss evolutionary considerations based on differences between vertebrate and invertebrate antiviral defense, and how the helicase domain has been co-opted in extant organisms as the binding site for accessory proteins. Many accessory proteins are double-stranded RNA binding proteins, and we propose models for how they modulate Dicer function and catalysis.
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Affiliation(s)
- Sarah R Hansen
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Adedeji M Aderounmu
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Helen M Donelick
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
| | - Brenda L Bass
- Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112-5650, USA
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8
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Moura MO, Fausto AKS, Fanelli A, Guedes FADF, Silva TDF, Romanel E, Vaslin MFS. Genome-wide identification of the Dicer-like family in cotton and analysis of the DCL expression modulation in response to biotic stress in two contrasting commercial cultivars. BMC PLANT BIOLOGY 2019; 19:503. [PMID: 31729948 PMCID: PMC6858778 DOI: 10.1186/s12870-019-2112-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 10/31/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND Dicer-like proteins (DCLs) are essential players in RNA-silencing mechanisms, acting in gene regulation via miRNAs and in antiviral protection in plants and have also been associated to other biotic and abiotic stresses. To the best of our knowledge, despite being identified in some crops, cotton DCLs haven't been characterized until now. In this work, we characterized the DCLs of three cotton species and analyzed their expression profiles during biotic stress. RESULTS As main results, 11 DCLs in the allotetraploid cotton Gossypium hirsutum, 7 and 6 in the diploid G. arboreum and G. raimondii, were identified, respectively. Among some DCLs duplications observed in these genomes, the presence of an extra DCL3 in the three cotton species were detected, which haven't been found in others eudicots. All the DCL types identified by in silico analysis in the allotetraploid cotton genome were able to generate transcripts, as observed by gene expression analysis in distinct tissues. Based on the importance of DCLs for plant defense against virus, responses of cotton DCLs to virus infection and/or herbivore attack using two commercial cotton cultivars (cv.), one susceptible (FM966) and another resistant (DO) to polerovirus CLRDV infection, were analyzed. Both cvs. Responded differently to virus infection. At the inoculation site, the resistant cv. showed strong induction of DCL2a and b, while the susceptible cv. showed a down-regulation of these genes, wherever DCL4 expression was highly induced. A time course of DCL expression in aerial parts far from inoculation site along infection showed that DCL2b and DCL4 were repressed 24 h after infection in the susceptible cotton. As CLRDV is aphid-transmitted, herbivore attack was also checked. Opposite expression pattern of DCL2a and b and DCL4 was observed for R and S cottons, showing that aphid feeding alone may induce DCL modulation. CONCLUSIONS Almost all the DCLs of the allotetraploide G. hirsutum cotton were found in their relative diploids. Duplications of DCL2 and DCL3 were found in the three species. All four classes of DCL responded to aphid attack and virus infection in G. hirsutum. DCLs initial responses against the virus itself and/or herbivore attack may be contributing towards virus resistance.
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Affiliation(s)
- Marianna O. Moura
- Departamento de Virologia, Instituto de Microbiologia, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ 21941-590 Brazil
| | - Anna Karoline S. Fausto
- Departamento de Virologia, Instituto de Microbiologia, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ 21941-590 Brazil
| | - Amanda Fanelli
- Departamento de Biotecnologia, Escola de Engenharia de Lorena/Universidade de São Paulo (EEL/USP), Lorena, SP 12602-810 Brazil
| | - Fernanda A. de F. Guedes
- Programa de Pós-graduação em Biotecnologia Vegetal, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ 21941-590 Brazil
| | - Tatiane da F. Silva
- Departamento de Biotecnologia, Escola de Engenharia de Lorena/Universidade de São Paulo (EEL/USP), Lorena, SP 12602-810 Brazil
| | - Elisson Romanel
- Departamento de Biotecnologia, Escola de Engenharia de Lorena/Universidade de São Paulo (EEL/USP), Lorena, SP 12602-810 Brazil
| | - Maite F. S. Vaslin
- Departamento de Virologia, Instituto de Microbiologia, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ 21941-590 Brazil
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9
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Zhu L, Kandasamy SK, Fukunaga R. Dicer partner protein tunes the length of miRNAs using base-mismatch in the pre-miRNA stem. Nucleic Acids Res 2019; 46:3726-3741. [PMID: 29373753 PMCID: PMC5909426 DOI: 10.1093/nar/gky043] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 01/17/2018] [Indexed: 12/19/2022] Open
Abstract
Dicer partner proteins Drosophila Loquacious-PB (Loqs-PB) and human TRBP tune the length of miRNAs produced by Dicer from a subset of pre-miRNAs and thereby alter their target repertoire, by an unknown mechanism. Here, we developed a novel high-throughput method that we named Dram-seq (Dice randomized pre-miRNA pool and seq) to study length distributions of miRNAs produced from thousands of different pre-miRNA variants. Using Dram-seq, we found that a base-mismatch in the pre-miRNA stem can alter the length of miRNAs compared with a base-pair at the same position in both Drosophila and human, and is important for the miRNA length tuning by Loqs-PB. Loqs-PB directly bound base-mismatched nucleotides in the pre-miRNA stem. We speculate that Loqs-PB tunes miRNA length by changing the conformation of base-mismatched nucleotides in the pre-miRNA stem to that of base-paired ones and thereby altering the distance of the pre-miRNA stem.
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Affiliation(s)
- Li Zhu
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, 521A Physiology Building, Baltimore, MD 21205, USA
| | - Suresh K Kandasamy
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, 521A Physiology Building, Baltimore, MD 21205, USA
| | - Ryuya Fukunaga
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, 521A Physiology Building, Baltimore, MD 21205, USA
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10
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Li P, Tian Q, Hu M, Li W, Zhang X, Zeng Y. Cloning, expression, and characterization of the zebrafish Dicer and Drosha enzymes. Biochem Biophys Res Commun 2019; 514:200-204. [PMID: 31029426 DOI: 10.1016/j.bbrc.2019.04.122] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 04/17/2019] [Indexed: 10/27/2022]
Abstract
The biogenesis of animal microRNAs (miRNAs) involves transcription followed by a series of processing steps, with Drosha and Dicer being two key enzymes that cleave primary miRNA (pri-miRNA) and precursor miRNA (pre-miRNA) transcripts, respectively. While human and fly Dicer and human Drosha are well studied, their homologs in other organisms have not been biochemically characterized, leaving open the question of whether their miRNA substrate specificities and regulatory functions are conserved. Zebrafish is a widely used model organism, but its miRNA processing enzymes have never been reconstituted and analyzed. In this study we cloned and constructed expression plasmids encoding zebrafish Dicer, Drosha, and their accessory proteins TARBP2 and DGCR8. After transfection of human cell cultures, we isolated the recombinant protein complexes. We found that zebrafish Dicer bound TARBP2, but Dicer alone exhibited significant pre-miRNA processing activity. On the other hand, zebrafish Drosha associated with DGCR8, and both were required to cleave pri-miRNAs. The Drosha/DGCR8 holoenzyme preferred pri-miRNAs with a large terminal loop, an extended duplex region, and flanking single stranded RNAs. These results lay the foundation for future studies of the regulatory roles and conserved mechanisms of Drosha and Dicer.
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Affiliation(s)
- Peng Li
- Department of Zoology, College of Life Sciences, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu, 210095, China
| | - Qiuhuan Tian
- Department of Zoology, College of Life Sciences, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu, 210095, China
| | - Min Hu
- Department of Zoology, College of Life Sciences, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu, 210095, China
| | - Wenjing Li
- Department of Zoology, College of Life Sciences, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu, 210095, China
| | - Xiaoxiao Zhang
- Department of Zoology, College of Life Sciences, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu, 210095, China
| | - Yan Zeng
- Department of Zoology, College of Life Sciences, Nanjing Agricultural University, 1 Weigang, Nanjing, Jiangsu, 210095, China.
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11
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Lee CH, Carroll BJ. Evolution and Diversification of Small RNA Pathways in Flowering Plants. PLANT & CELL PHYSIOLOGY 2018; 59:2169-2187. [PMID: 30169685 DOI: 10.1093/pcp/pcy167] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Accepted: 08/30/2018] [Indexed: 06/08/2023]
Abstract
Small regulatory RNAs guide gene silencing at the DNA or RNA level through repression of complementary sequences. The two main forms of small RNAs are microRNA (miRNA) and small interfering RNA (siRNAs), which are generated from the processing of different forms of double-stranded RNA (dsRNA) precursors. These two forms of small regulatory RNAs function in distinct but overlapping gene silencing pathways in plants. Gene silencing pathways in eukaryotes evolved from an ancient prokaryotic mechanism involved in genome defense against invasive genetic elements, but has since diversified to also play a crucial role in regulation of endogenous gene expression. Here, we review the biogenesis of the different forms of small RNAs in plants, including miRNAs, phased, secondary siRNAs (phasiRNAs) and heterochromatic siRNAs (hetsiRNAs), with a focus on their functions in genome defense, transcriptional and post-transcriptional gene silencing, RNA-directed DNA methylation, trans-chromosomal methylation and paramutation. We also discuss the important role that gene duplication has played in the functional diversification of gene silencing pathways in plants, and we highlight recently discovered components of gene silencing pathways in plants.
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Affiliation(s)
- Chin Hong Lee
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
| | - Bernard J Carroll
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Australia
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12
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Heyam A, Coupland CE, Dégut C, Haley RA, Baxter NJ, Jakob L, Aguiar PM, Meister G, Williamson MP, Lagos D, Plevin MJ. Conserved asymmetry underpins homodimerization of Dicer-associated double-stranded RNA-binding proteins. Nucleic Acids Res 2017; 45:12577-12584. [PMID: 29045748 PMCID: PMC5716075 DOI: 10.1093/nar/gkx928] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 10/09/2017] [Indexed: 11/14/2022] Open
Abstract
Double-stranded RNA-binding domains (dsRBDs) are commonly found in modular proteins that interact with RNA. Two varieties of dsRBD exist: canonical Type A dsRBDs interact with dsRNA, while non-canonical Type B dsRBDs lack RNA-binding residues and instead interact with other proteins. In higher eukaryotes, the microRNA biogenesis enzyme Dicer forms a 1:1 association with a dsRNA-binding protein (dsRBP). Human Dicer associates with HIV TAR RNA-binding protein (TRBP) or protein activator of PKR (PACT), while Drosophila Dicer-1 associates with Loquacious (Loqs). In each case, the interaction involves a region of the protein that contains a Type B dsRBD. All three dsRBPs are reported to homodimerize, with the Dicer-binding region implicated in self-association. We report that these dsRBD homodimers display structural asymmetry and that this unusual self-association mechanism is conserved from flies to humans. We show that the core dsRBD is sufficient for homodimerization and that mutation of a conserved leucine residue abolishes self-association. We attribute differences in the self-association properties of Loqs, TRBP and PACT to divergence of the composition of the homodimerization interface. Modifications that make TRBP more like PACT enhance self-association. These data are examined in the context of miRNA biogenesis and the protein/protein interaction properties of Type B dsRBDs.
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Affiliation(s)
- Alex Heyam
- Department of Biology, University of York, York, YO10 5DD, UK
| | | | - Clément Dégut
- Department of Biology, University of York, York, YO10 5DD, UK
| | - Ruth A Haley
- Department of Biology, University of York, York, YO10 5DD, UK
| | - Nicola J Baxter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Leonhard Jakob
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Pedro M Aguiar
- Department of Chemistry, University of York, York, YO10 5DD, UK
| | - Gunter Meister
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Michael P Williamson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, S10 2TN, UK
| | - Dimitris Lagos
- Centre for Immunology and Infection, Department of Biology and Hull York Medical School, University of York, Wentworth Way, York, YO10 5DD, UK
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13
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Kandasamy SK, Zhu L, Fukunaga R. The C-terminal dsRNA-binding domain of Drosophila Dicer-2 is crucial for efficient and high-fidelity production of siRNA and loading of siRNA to Argonaute2. RNA (NEW YORK, N.Y.) 2017; 23:1139-1153. [PMID: 28416567 PMCID: PMC5473147 DOI: 10.1261/rna.059915.116] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 04/10/2017] [Indexed: 05/25/2023]
Abstract
Drosophila Dicer-2 efficiently and precisely produces 21-nucleotide (nt) siRNAs from long double-stranded RNA (dsRNA) substrates and loads these siRNAs onto the effector protein Argonaute2 for RNA silencing. The functional roles of each domain of the multidomain Dicer-2 enzyme in the production and loading of siRNAs are not fully understood. Here we characterized Dicer-2 mutants lacking either the N-terminal helicase domain or the C-terminal dsRNA-binding domain (CdsRBD) (ΔHelicase and ΔCdsRBD, respectively) in vivo and in vitro. We found that ΔCdsRBD Dicer-2 produces siRNAs with lowered efficiency and length fidelity, producing a smaller ratio of 21-nt siRNAs and higher ratios of 20- and 22-nt siRNAs in vivo and in vitro. We also found that ΔCdsRBD Dicer-2 cannot load siRNA duplexes to Argonaute2 in vitro. Consistent with these findings, we found that ΔCdsRBD Dicer-2 causes partial loss of RNA silencing activity in vivo. Thus, Dicer-2 CdsRBD is crucial for the efficiency and length fidelity in siRNA production and for siRNA loading. Together with our previously published findings, we propose that CdsRBD binds the proximal body region of a long dsRNA substrate whose 5'-monophosphate end is anchored by the phosphate-binding pocket in the PAZ domain. CdsRBD aligns the RNA to the RNA cleavage active site in the RNase III domain for efficient and high-fidelity siRNA production. This study reveals multifunctions of Dicer-2 CdsRBD and sheds light on the molecular mechanism by which Dicer-2 produces 21-nt siRNAs with a high efficiency and fidelity for efficient RNA silencing.
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Affiliation(s)
- Suresh K Kandasamy
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Li Zhu
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Ryuya Fukunaga
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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14
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Paces J, Nic M, Novotny T, Svoboda P. Literature review of baseline information to support the risk assessment of RNAi‐based GM plants. ACTA ACUST UNITED AC 2017. [PMCID: PMC7163844 DOI: 10.2903/sp.efsa.2017.en-1246] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Jan Paces
- Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic (IMG)
| | | | | | - Petr Svoboda
- Institute of Molecular Genetics of the Academy of Sciences of the Czech Republic (IMG)
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15
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Fukudome A, Fukuhara T. Plant dicer-like proteins: double-stranded RNA-cleaving enzymes for small RNA biogenesis. JOURNAL OF PLANT RESEARCH 2017; 130:33-44. [PMID: 27885504 DOI: 10.1007/s10265-016-0877-1] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 10/08/2016] [Indexed: 05/20/2023]
Abstract
Dicer, a double-stranded RNA (dsRNA)-specific endoribonuclease, plays an essential role in triggering both transcriptional and post-transcriptional gene silencing in eukaryotes by cleaving dsRNAs or single-stranded RNAs bearing stem-loop structures such as microRNA precursor transcripts into 21- to 24-nt small RNAs. Unlike animals, plants have evolved to utilize at least four Dicer-like (DCL) proteins. Extensive genetic studies have revealed that each DCL protein participates in a specific gene silencing pathway, with some redundancy. However, a mechanistic understanding of how the specific action of each DCL protein is regulated in its respective pathway is still in its infancy due to the limited number of biochemical studies on plant DCL proteins. In this review, we summarize and discuss the biochemical properties of plant DCL proteins revealed by studies using highly purified recombinant proteins, crude extracts, and immunoprecipitates. With help from co-factor proteins and an ATPase/DExH-box RNA-helicase domain, the microRNA-producing enzyme DCL1 recognizes bulges and terminal loop structures in its substrate transcripts to ensure accurate and efficient processing. DCL4 prefers long dsRNA substrates and requires the dsRNA-binding protein DRB4 for its activity. The short-dsRNA preference of DCL3 is well suited for short-RNA transcription and subsequent dsRNA formation by coupling between a plant-specific DNA-dependent RNA-polymerase IV and RNA-dependent RNA-polymerase 2 in the transcriptional gene silencing pathway. Inorganic phosphate also seems to play a role in differential regulation of DCL3 and DCL4 activities. Further development of biochemical approaches will be necessary for better understanding of how plant DCL proteins are fine-tuned in each small RNA biogenesis pathway under various physiological conditions.
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Affiliation(s)
- Akihito Fukudome
- Molecular and Environmental Plant Sciences, Department of Horticultural Sciences, Vegetable and Fruit Improvement Center, Texas A&M University, College Station, TX, 77843, USA
| | - Toshiyuki Fukuhara
- Department of Applied Biological Sciences and Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo, 183-8509, Japan.
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16
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Mickiewicz A, Sarzyńska J, Miłostan M, Kurzyńska-Kokorniak A, Rybarczyk A, Łukasiak P, Kuliński T, Figlerowicz M, Błażewicz J. Modeling of the catalytic core of Arabidopsis thaliana Dicer-like 4 protein and its complex with double-stranded RNA. Comput Biol Chem 2016; 66:44-56. [PMID: 27907832 DOI: 10.1016/j.compbiolchem.2016.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 10/11/2016] [Accepted: 11/16/2016] [Indexed: 12/20/2022]
Abstract
Plant Dicer-like proteins (DCLs) belong to the Ribonuclease III (RNase III) enzyme family. They are involved in the regulation of gene expression and antiviral defense through RNA interference pathways. A model plant, Arabidopsis thaliana encodes four DCL proteins (AtDCL1-4) that produce different classes of small regulatory RNAs. Our studies focus on AtDCL4 that processes double-stranded RNAs (dsRNAs) into 21 nucleotide trans-acting small interfering RNAs. So far, little is known about the structures of plant DCLs and the complexes they form with dsRNA. In this work, we present models of the catalytic core of AtDCL4 and AtDCL4-dsRNA complex constructed by computational methods. We built a homology model of the catalytic core of AtDCL4 comprising Platform, PAZ, Connector helix and two RNase III domains. To assemble the AtDCL4-dsRNA complex two modeling approaches were used. In the first method, to establish conformations that allow building a consistent model of the complex, we used Normal Mode Analysis for both dsRNA and AtDCL4. The second strategy involved template-based approach for positioning of the PAZ domain and manual arrangement of the Connector helix. Our results suggest that the spatial orientation of the Connector helix, Platform and PAZ relative to the RNase III domains is crucial for measuring dsRNA of defined length. The modeled complexes provide information about interactions that may contribute to the relative orientations of these domains and to dsRNA binding. All these information can be helpful for understanding the mechanism of AtDCL4-mediated dsRNA recognition and binding, to produce small RNA of specific size.
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Affiliation(s)
- Agnieszka Mickiewicz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland
| | - Joanna Sarzyńska
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland.
| | - Maciej Miłostan
- Institute of Computing Science, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland
| | - Anna Kurzyńska-Kokorniak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland
| | - Agnieszka Rybarczyk
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland; Institute of Computing Science, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland
| | - Piotr Łukasiak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland; Institute of Computing Science, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland
| | - Tadeusz Kuliński
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland
| | - Marek Figlerowicz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland; Institute of Computing Science, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland
| | - Jacek Błażewicz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznań, Poland; Institute of Computing Science, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland; European Centre for Bioinformatics and Genomics, Poznan University of Technology, Piotrowo 2, 60-965 Poznań, Poland
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17
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Revealing a new activity of the human Dicer DUF283 domain in vitro. Sci Rep 2016; 6:23989. [PMID: 27045313 PMCID: PMC4820750 DOI: 10.1038/srep23989] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 03/15/2016] [Indexed: 12/26/2022] Open
Abstract
The ribonuclease Dicer is a multidomain enzyme that plays a fundamental role in the biogenesis of small regulatory RNAs (srRNAs), which control gene expression by targeting complementary transcripts and inducing their cleavage or repressing their translation. Recent studies of Dicer's domains have permitted to propose their roles in srRNA biogenesis. For all of Dicer's domains except one, called DUF283 (domain of unknown function), their involvement in RNA substrate recognition, binding or cleavage has been postulated. For DUF283, the interaction with Dicer's protein partners has been the only function suggested thus far. In this report, we demonstrate that the isolated DUF283 domain from human Dicer is capable of binding single-stranded nucleic acids in vitro. We also show that DUF283 can act as a nucleic acid annealer that accelerates base-pairing between complementary RNA/DNA molecules in vitro. We further demonstrate an annealing activity of full length human Dicer. The overall results suggest that Dicer, presumably through its DUF283 domain, might facilitate hybridization between short RNAs and their targets. The presented findings reveal the complex nature of Dicer, whose functions may extend beyond the biogenesis of srRNAs.
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18
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Jakob L, Treiber T, Treiber N, Gust A, Kramm K, Hansen K, Stotz M, Wankerl L, Herzog F, Hannus S, Grohmann D, Meister G. Structural and functional insights into the fly microRNA biogenesis factor Loquacious. RNA (NEW YORK, N.Y.) 2016; 22:383-396. [PMID: 26769856 PMCID: PMC4748816 DOI: 10.1261/rna.055426.115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Accepted: 12/02/2015] [Indexed: 06/05/2023]
Abstract
In the microRNA (miRNA) pathway, Dicer processes precursors to mature miRNAs. For efficient processing, double-stranded RNA-binding proteins support Dicer proteins. In flies, Loquacious (Loqs) interacts with Dicer1 (dmDcr1) to facilitate miRNA processing. Here, we have solved the structure of the third double-stranded RNA-binding domain (dsRBD) of Loqs and define specific structural elements that interact with dmDcr1. In addition, we show that the linker preceding dsRBD3 contributes significantly to dmDcr1 binding. Furthermore, our structural work demonstrates that the third dsRBD of Loqs forms homodimers. Mutations in the dimerization interface abrogate dmDcr1 interaction. Loqs, however, binds to dmDcr1 as a monomer using the identified dimerization surface, which suggests that Loqs might form dimers under conditions where dmDcr1 is absent or not accessible. Since critical sequence elements are conserved, we suggest that dimerization might be a general feature of dsRBD proteins in gene silencing.
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Affiliation(s)
- Leonhard Jakob
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Thomas Treiber
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Nora Treiber
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Alexander Gust
- Department of Microbiology and Archaea Centre, Laboratory of Single-Molecule Biochemistry, University of Regensburg, 93053 Regensburg, Germany
| | - Kevin Kramm
- Department of Microbiology and Archaea Centre, Laboratory of Single-Molecule Biochemistry, University of Regensburg, 93053 Regensburg, Germany
| | - Kerrin Hansen
- Intana Bioscience GmbH, 82152 Planegg, Martinsried, Germany
| | - Mathias Stotz
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Ludwig Wankerl
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
| | - Franz Herzog
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-University, 81377 München, Germany
| | - Stefan Hannus
- Intana Bioscience GmbH, 82152 Planegg, Martinsried, Germany
| | - Dina Grohmann
- Department of Microbiology and Archaea Centre, Laboratory of Single-Molecule Biochemistry, University of Regensburg, 93053 Regensburg, Germany
| | - Gunter Meister
- Biochemistry Center Regensburg (BZR), Laboratory for RNA Biology, University of Regensburg, 93053 Regensburg, Germany
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19
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Liang C, Wang Y, Murota Y, Liu X, Smith D, Siomi MC, Liu Q. TAF11 Assembles the RISC Loading Complex to Enhance RNAi Efficiency. Mol Cell 2015; 59:807-18. [PMID: 26257286 DOI: 10.1016/j.molcel.2015.07.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 05/21/2015] [Accepted: 07/01/2015] [Indexed: 11/16/2022]
Abstract
Assembly of the RNA-induced silencing complex (RISC) requires formation of the RISC loading complex (RLC), which contains the Dicer-2 (Dcr-2)-R2D2 complex and recruits duplex siRNA to Ago2 in Drosophila melanogaster. However, the precise composition and action mechanism of Drosophila RLC remain unclear. Here we identified the missing factor of RLC as TATA-binding protein-associated factor 11 (TAF11) by genetic screen. Although it is an annotated nuclear transcription factor, we found that TAF11 also associated with Dcr-2/R2D2 and localized to cytoplasmic D2 bodies. Consistent with defective RLC assembly in taf11(-/-) ovary extract, we reconstituted the RLC in vitro using the recombinant Dcr-2-R2D2 complex, TAF11, and duplex siRNA. Furthermore, we showed that TAF11 tetramer facilitates Dcr-2-R2D2 tetramerization to enhance siRNA binding and RISC loading activities. Together, our genetic and biochemical studies define the molecular nature of the Drosophila RLC and elucidate a cytoplasmic function of TAF11 in organizing RLC assembly to enhance RNAi efficiency.
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Affiliation(s)
- Chunyang Liang
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yibing Wang
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Yukiko Murota
- Department of Biological Sciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Xiang Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Dean Smith
- Departments of Pharmacology and Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Mikiko C Siomi
- Department of Biological Sciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Qinghua Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; International Institute of Integrated Sleep Medicine, University of Tsukuba, Tsukuba 305-8575, Japan.
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20
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Kurzynska-Kokorniak A, Koralewska N, Pokornowska M, Urbanowicz A, Tworak A, Mickiewicz A, Figlerowicz M. The many faces of Dicer: the complexity of the mechanisms regulating Dicer gene expression and enzyme activities. Nucleic Acids Res 2015; 43:4365-80. [PMID: 25883138 PMCID: PMC4482082 DOI: 10.1093/nar/gkv328] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 03/31/2015] [Indexed: 12/14/2022] Open
Abstract
There is increasing evidence indicating that the production of small regulatory RNAs is not the only process in which ribonuclease Dicer can participate. For example, it has been demonstrated that this enzyme is also involved in chromatin structure remodelling, inflammation and apoptotic DNA degradation. Moreover, it has become increasingly clear that cellular transcript and protein levels of Dicer must be strictly controlled because even small changes in their accumulation can initiate various pathological processes, including carcinogenesis. Accordingly, in recent years, a number of studies have been performed to identify the factors regulating Dicer gene expression and protein activity. As a result, a large amount of complex and often contradictory data has been generated. None of these data have been subjected to an exhaustive review or critical discussion. This review attempts to fill this gap by summarizing the current knowledge of factors that regulate Dicer gene transcription, primary transcript processing, mRNA translation and enzyme activity. Because of the high complexity of this topic, this review mainly concentrates on human Dicer. This review also focuses on an additional regulatory layer of Dicer activity involving the interactions of protein and RNA factors with Dicer substrates.
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Affiliation(s)
| | - Natalia Koralewska
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland
| | - Maria Pokornowska
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland
| | - Anna Urbanowicz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland
| | - Aleksander Tworak
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland
| | - Agnieszka Mickiewicz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland
| | - Marek Figlerowicz
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland Institute of Computing Science, Poznan University of Technology, Poznan 60-965, Poland
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21
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Haac ME, Anderson MAE, Eggleston H, Myles KM, Adelman ZN. The hub protein loquacious connects the microRNA and short interfering RNA pathways in mosquitoes. Nucleic Acids Res 2015; 43:3688-700. [PMID: 25765650 PMCID: PMC4402513 DOI: 10.1093/nar/gkv152] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 02/16/2015] [Indexed: 01/28/2023] Open
Abstract
Aedes aegypti mosquitoes vector several arboviruses of global health significance, including dengue viruses and chikungunya virus. RNA interference (RNAi) plays an important role in antiviral immunity, gene regulation and protection from transposable elements. Double-stranded RNA binding proteins (dsRBPs) are important for efficient RNAi; in Drosophila functional specialization of the miRNA, endo-siRNA and exo-siRNA pathway is aided by the dsRBPs Loquacious (Loqs-PB, Loqs-PD) and R2D2, respectively. However, this functional specialization has not been investigated in other dipterans. We were unable to detect Loqs-PD in Ae. aegypti; analysis of other dipteran genomes demonstrated that this isoform is not conserved outside of Drosophila. Overexpression experiments and small RNA sequencing following depletion of each dsRBP revealed that R2D2 and Loqs-PA cooperate non-redundantly in siRNA production, and that these proteins exhibit an inhibitory effect on miRNA levels. Conversely, Loqs-PB alone interacted with mosquito dicer-1 and was essential for full miRNA production. Mosquito Loqs interacted with both argonaute 1 and 2 in a manner independent of its interactions with dicer. We conclude that the functional specialization of Loqs-PD in Drosophila is a recently derived trait, and that in other dipterans, including the medically important mosquitoes, Loqs-PA participates in both the miRNA and endo-siRNA based pathways.
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Affiliation(s)
- Mary Etna Haac
- Fralin Life Science Institute and Department of Entomology, Virginia Tech, Blacksburg, VA 24061, USA
| | - Michelle A E Anderson
- Fralin Life Science Institute and Department of Entomology, Virginia Tech, Blacksburg, VA 24061, USA
| | - Heather Eggleston
- Fralin Life Science Institute and Department of Entomology, Virginia Tech, Blacksburg, VA 24061, USA
| | - Kevin M Myles
- Fralin Life Science Institute and Department of Entomology, Virginia Tech, Blacksburg, VA 24061, USA
| | - Zach N Adelman
- Fralin Life Science Institute and Department of Entomology, Virginia Tech, Blacksburg, VA 24061, USA
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22
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Gleghorn ML, Maquat LE. 'Black sheep' that don't leave the double-stranded RNA-binding domain fold. Trends Biochem Sci 2014; 39:328-40. [PMID: 24954387 DOI: 10.1016/j.tibs.2014.05.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2014] [Revised: 05/19/2014] [Accepted: 05/19/2014] [Indexed: 12/28/2022]
Abstract
The canonical double-stranded RNA (dsRNA)-binding domain (dsRBD) is composed of an α1-β1-β2-β3-α2 secondary structure that folds in three dimensions to recognize dsRNA. Recently, structural and functional studies of divergent dsRBDs revealed adaptations that include intra- and/or intermolecular protein interactions, sometimes in the absence of detectable dsRNA-binding ability. We describe here how discrete dsRBD components can accommodate pronounced amino-acid sequence changes while maintaining the core fold. We exemplify the growing importance of divergent dsRBDs in mRNA decay by discussing Dicer, Staufen (STAU)1 and 2, trans-activation responsive RNA-binding protein (TARBP)2, protein activator of protein kinase RNA-activated (PKR) (PACT), DiGeorge syndrome critical region (DGCR)8, DEAH box helicase proteins (DHX) 9 and 30, and dsRBD-like fold-containing proteins that have ribosome-related functions. We also elaborate on the computational limitations to discovering yet-to-be-identified divergent dsRBDs.
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Affiliation(s)
- Michael L Gleghorn
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA
| | - Lynne E Maquat
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA.
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23
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Fukunaga R, Colpan C, Han BW, Zamore PD. Inorganic phosphate blocks binding of pre-miRNA to Dicer-2 via its PAZ domain. EMBO J 2014; 33:371-84. [PMID: 24488111 DOI: 10.1002/embj.201387176] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In Drosophila, Dicer-1 produces microRNAs (miRNAs) from pre-miRNAs, whereas Dicer-2 generates small interfering RNAs from long double-stranded RNA (dsRNA), a process that requires ATP hydrolysis. We previously showed that inorganic phosphate inhibits Dicer-2 cleavage of pre-miRNAs, but not long dsRNAs. Here, we report that phosphate-dependent substrate discrimination by Dicer-2 reflects dsRNA substrate length. Efficient processing by Dicer-2 of short dsRNA requires a 5' terminal phosphate and a two-nucleotide, 3' overhang, but does not require ATP. Phosphate inhibits cleavage of such short substrates. In contrast, cleavage of longer dsRNA requires ATP but no specific end structure: phosphate does not inhibit cleavage of these substrates. Mutation of a pair of conserved arginine residues in the Dicer-2 PAZ domain blocked cleavage of short, but not long, dsRNA. We propose that inorganic phosphate occupies a PAZ domain pocket required to bind the 5' terminal phosphate of short substrates, blocking their use and restricting pre-miRNA processing in flies to Dicer-1. Our study helps explain how a small molecule can alter the substrate specificity of a nucleic acid processing enzyme.
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Affiliation(s)
- Ryuya Fukunaga
- Howard Hughes Medical Institute RNA Therapeutics Institute University of Massachusetts Medical School, Worcester, MA, USA
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24
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Nagano H, Fukudome A, Hiraguri A, Moriyama H, Fukuhara T. Distinct substrate specificities of Arabidopsis DCL3 and DCL4. Nucleic Acids Res 2013; 42:1845-56. [PMID: 24214956 PMCID: PMC3919572 DOI: 10.1093/nar/gkt1077] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In Arabidopsis thaliana, Dicer-like 3 (DCL3) and Dicer-like 4 (DCL4) cleave long, perfect double-stranded RNAs (dsRNAs) into 24 and 21 nucleotides (nt) small interfering RNAs, respectively, which in turn function in RNA-directed DNA methylation and RNA interference, respectively. To reveal how DCL3 and DCL4 individually recognize long perfect dsRNAs as substrates, we biochemically characterized DCL3 and DCL4 and compared their enzymatic properties. DCL3 preferentially cleaves short dsRNAs with 5′ phosphorylated adenosine or uridine and a 1 nt 3′ overhang, whereas DCL4 cleaves long dsRNAs with blunt ends or with a 1 or 2 nt 3′ overhang with similar efficiency. DCL3 produces 24 nt RNA duplexes with 2 nt 3′ overhangs by the 5′ counting rule. Inorganic phosphate, NaCl and KCl enhance DCL3 activity but inhibit DCL4 activity. These results indicate that plants use DCLs with distinct catalytic profiles to ensure each dsRNA substrate generates only a specific length of siRNAs that trigger a unique siRNA-mediated response.
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Affiliation(s)
- Hideaki Nagano
- Department of Applied Biological Sciences, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo 183-8509, Japan
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25
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Shreve JT, Shukle RH, Subramanyam S, Johnson AJ, Schemerhorn BJ, Williams CE, Stuart JJ. A genome-wide survey of small interfering RNA and microRNA pathway genes in a galling insect. JOURNAL OF INSECT PHYSIOLOGY 2013; 59:367-376. [PMID: 23232437 DOI: 10.1016/j.jinsphys.2012.11.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 11/28/2012] [Accepted: 11/30/2012] [Indexed: 06/01/2023]
Abstract
Deployment of resistance (R) genes is the most effective control for Hessian fly, Mayetiola destructor (Say); however, deployment of R genes results in an increased frequency of pest genotypes that display virulence to them. RNA interference (RNAi) is a useful reverse genetics tool for studying such insect virulence pathways, but requires a systemic phenotype, which is not found in all species. In an effort to correlate our observed weak RNAi phenotype in M. destructor with a genetic basis, we have aggregated and compared RNAi related genes across M. destructor, three other insect species, and the nematode Caenorhabditis elegans. We report here the annotation of the core genes in the small interfering RNA (siRNA) and microRNA (miRNA) pathways in M. destructor. While most of the miRNA pathway genes were highly conserved across the species studied, the siRNA pathway genes showed increased relative variability in comparison to the miRNA pathway. In particular, the Piwi/Argonaute/Zwille (PAZ) domain of Dicer-2 (DCR-2) had the least amount of sequence similarity of any domain among species surveyed, with a trend of increased conservation in those species with amenable systemic RNAi. A homolog of the systemic interference defective-1 (Sid-1) gene of C. elegans was also not annotated in the M. destructor genome. Indeed, it is of interest that a Sid-1 homolog has not been detected in any dipteran species to date. We hypothesize the sequence architecture of the PAZ domain in the M. destructor DCR-2 protein is related to reduced efficacy of this enzyme and this taken together with the lack of a Sid-1 homolog may account for the weak RNAi response observed to date in this species as well as other dipteran species.
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Affiliation(s)
- Jacob T Shreve
- Department of Entomology, Purdue University, West Lafayette, IN 47907, USA
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26
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Fukunaga R, Han BW, Hung JH, Xu J, Weng Z, Zamore PD. Dicer partner proteins tune the length of mature miRNAs in flies and mammals. Cell 2012; 151:533-46. [PMID: 23063653 PMCID: PMC3609031 DOI: 10.1016/j.cell.2012.09.027] [Citation(s) in RCA: 135] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2012] [Revised: 07/28/2012] [Accepted: 09/06/2012] [Indexed: 01/31/2023]
Abstract
Drosophila Dicer-1 produces microRNAs (miRNAs) from pre-miRNA, whereas Dicer-2 generates small interfering RNAs (siRNAs) from long dsRNA. Alternative splicing of the loquacious (loqs) mRNA generates three distinct Dicer partner proteins. To understand the function of each, we constructed flies expressing Loqs-PA, Loqs-PB, or Loqs-PD. Loqs-PD promotes both endo- and exo-siRNA production by Dicer-2. Loqs-PA or Loqs-PB is required for viability, but the proteins are not fully redundant: a specific subset of miRNAs requires Loqs-PB. Surprisingly, Loqs-PB tunes where Dicer-1 cleaves pre-miR-307a, generating a longer miRNA isoform with a distinct seed sequence and target specificity. The longer form of miR-307a represses glycerol kinase and taranis mRNA expression. The mammalian Dicer-partner TRBP, a Loqs-PB homolog, similarly tunes where Dicer cleaves pre-miR-132. Thus, Dicer-binding partner proteins change the choice of cleavage site by Dicer, producing miRNAs with target specificities different from those made by Dicer alone or Dicer bound to alternative protein partners.
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Affiliation(s)
- Ryuya Fukunaga
- Howard Hughes Medical Institute and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Bo W. Han
- Howard Hughes Medical Institute and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Jui-Hung Hung
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Jia Xu
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Phillip D. Zamore
- Howard Hughes Medical Institute and Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
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Bouasker S, Simard MJ. The slicing activity of miRNA-specific Argonautes is essential for the miRNA pathway in C. elegans. Nucleic Acids Res 2012; 40:10452-62. [PMID: 22904066 PMCID: PMC3488219 DOI: 10.1093/nar/gks748] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Among the set of Argonautes proteins encoded by metazoan genomes, some have conserved amino acids important for catalytic or slicing activity. The functional significance of these residues in microRNA (miRNA)-specific Argonautes in animals is still unclear since miRNAs do not induce site-specific cleavage of targeted messenger RNAs (mRNAs), unlike small interfering RNAs (siRNAs). Here, we report that miRNA-specific ALG-1 and ALG-2 Argonautes from Caenorhabditis elegans possess the slicing activity normally implicated in the siRNA-silencing pathway. We also find that ALG-1/2 can bind and use a Dicer-processed miRNA duplex to target mRNAs, suggesting an ability to displace RNA strands. Importantly, the slicing activity of ALG-1 or ALG-2 is essential for the miRNA pathway in vivo, as shown by the accumulation of truncated miRNA precursors and altered miRNA-induced silencing complex (miRISC) formation. Taken together, our data demonstrate that the slicing activity of Argonautes contributes to a new and unexpected step in the canonical miRNA pathway that occurs prior to miRISC loading in animals.
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Affiliation(s)
- Samir Bouasker
- Laval University Cancer Research Centre, Hôtel-Dieu de Québec (CHUQ), Quebec City, Québec G1R 2J6, Canada
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28
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The molecular architecture of human Dicer. Nat Struct Mol Biol 2012; 19:436-40. [PMID: 22426548 PMCID: PMC3319852 DOI: 10.1038/nsmb.2268] [Citation(s) in RCA: 152] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 02/22/2012] [Indexed: 12/20/2022]
Abstract
Dicer is a multi-domain enzyme that generates small RNAs for gene silencing in eukaryotes. Current understanding of Dicer structure is restricted to simple forms of the enzyme, while that of the large and complex Dicer, widespread in eukarya, is unknown. Here, we describe a novel domain localization strategy developed to determine the structure of human Dicer by electron microscopy. A rearrangement of the nuclease core, compared to the archetypal Giardia Dicer, explains how metazoan Dicers generate 21–23 nucleotide products. The helicase domains form a clamp-like structure adjacent to the RNase III active site, facilitating recognition of pre-miRNA loops or translocation on long dsRNAs. Drosophila Dicer-2 displays similar features, revealing that the three-dimensional architecture is conserved. These results illuminate the structural basis for small RNA production in eukaryotes and provide a versatile new tool for determining structures of large molecular machines.
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29
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Dicer Proteins and Their Role in Gene Silencing Pathways. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/b978-0-12-404741-9.00001-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
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30
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Recognition of the pre-miRNA structure by Drosophila Dicer-1. Nat Struct Mol Biol 2011; 18:1153-8. [PMID: 21926993 DOI: 10.1038/nsmb.2125] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 07/13/2011] [Indexed: 11/09/2022]
Abstract
Drosophila melanogaster has two Dicer proteins with specialized functions. Dicer-1 liberates miRNA-miRNA* duplexes from precursor miRNAs (pre-miRNAs), whereas Dicer-2 processes long double-stranded RNAs into small interfering RNA duplexes. It was recently demonstrated that Dicer-2 is rendered highly specific for long double-stranded RNA substrates by inorganic phosphate and a partner protein R2D2. However, it remains unclear how Dicer-1 exclusively recognize pre-miRNAs. Here we show that fly Dicer-1 recognizes the single-stranded terminal loop structure of pre-miRNAs through its N-terminal helicase domain, checks the loop size and measures the distance between the 3' overhang and the terminal loop. This unique mechanism allows fly Dicer-1 to strictly inspect the authenticity of pre-miRNA structures.
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31
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Ye X, Huang N, Liu Y, Paroo Z, Huerta C, Li P, Chen S, Liu Q, Zhang H. Structure of C3PO and mechanism of human RISC activation. Nat Struct Mol Biol 2011; 18:650-7. [PMID: 21552258 PMCID: PMC3109212 DOI: 10.1038/nsmb.2032] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2010] [Accepted: 02/08/2011] [Indexed: 01/07/2023]
Abstract
Assembly of the RNA-induced silencing complex (RISC) consists of loading duplex (guide-passenger) siRNA onto Argonaute (Ago2) and removing the passenger strand. Ago2 contributes critically to RISC activation by nicking the passenger strand. Here we reconstituted duplex siRNA-initiated RISC activity using recombinant human Ago2 (hAgo2) and C3PO, indicating that C3PO has a critical role in hAgo2-RISC activation. Consistently, genetic depletion of C3PO compromised RNA silencing in mammalian cells. We determined the crystal structure of hC3PO, which reveals an asymmetric octamer barrel consisting of six translin and two TRAX subunits. This asymmetric assembly is critical for the function of C3PO as an endonuclease that cleaves RNA at the interior surface. The current work supports a Dicer-independent mechanism for human RISC activation, in which Ago2 directly binds duplex siRNA and nicks the passenger strand, and then C3PO activates RISC by degrading the Ago2-nicked passenger strand.
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Affiliation(s)
- Xuecheng Ye
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Nian Huang
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ying Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Zain Paroo
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Carlos Huerta
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Peng Li
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - She Chen
- National Institute of Biological Sciences, No.7 Science Park Road, Zhongguancun Life Science Park, Beijing 102206, China
| | - Qinghua Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA,Corresponding author: ; FAX: (214) 645–5948, ; FAX: (214) 648–8856
| | - Hong Zhang
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA,Corresponding author: ; FAX: (214) 645–5948, ; FAX: (214) 648–8856
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32
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Kanno T, Habu Y. siRNA-mediated chromatin maintenance and its function in Arabidopsis thaliana. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1809:444-51. [PMID: 21605714 DOI: 10.1016/j.bbagrm.2011.05.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/02/2011] [Accepted: 05/05/2011] [Indexed: 01/13/2023]
Abstract
Small interfering RNAs (siRNAs) are widespread in various eukaryotes and are involved in maintenance of chromatin modifications, especially those for inert states represented by covalent modifications of cytosine and/or histones. In contrast to mammalian genomes, in which cytosine methylation is restricted mostly to CG dinucleotide sequences, inert chromatin in plants carries cytosine methylation in all sequence contexts, and siRNAs play a major role in directing cytosine methylation through the process of RNA-directed DNA methylation. Recent advances in this field have revealed that siRNA-mediated maintenance of inert chromatin has diverse roles in development as well as in plant responses to the environment. Various proteinaceous factors required for siRNA-mediated chromatin modification have been identified in Arabidopsis thaliana, and much effort has been invested in understanding their function and interaction, resulting in the assignment of many of these factors to specific biochemical activities and engagement with specific steps such as transcription of intergenic RNAs, RNA processing, and cytosine methylation. However, the precise functions of a number of factors remain undesignated, and interactions of distinct pathways for siRNA-mediated chromatin modification are largely unknown. In this review, we summarize the roles of siRNA-mediated chromatin modification in various biological processes of A. thaliana, and present some speculation on the functions and interactions of silencing factors that, while not yet assigned to defined biochemical activities, have been loosely assigned to specific events in siRNA-mediated chromatin modification pathways. Special Issue entitled: Epigenetic control of cellular and developmental processes in plants.
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Affiliation(s)
- Tatsuo Kanno
- National Institute of Agrobiological Sciences, Ibaraki, Japan
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33
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Cenik ES, Fukunaga R, Lu G, Dutcher R, Wang Y, Tanaka Hall TM, Zamore PD. Phosphate and R2D2 restrict the substrate specificity of Dicer-2, an ATP-driven ribonuclease. Mol Cell 2011; 42:172-84. [PMID: 21419681 DOI: 10.1016/j.molcel.2011.03.002] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 01/26/2011] [Accepted: 03/03/2011] [Indexed: 12/29/2022]
Abstract
Drosophila Dicer-2 generates small interfering RNAs (siRNAs) from long double-stranded RNA (dsRNA), whereas Dicer-1 produces microRNAs (miRNAs) from pre-miRNA. What makes the two Dicers specific for their biological substrates? We find that purified Dicer-2 can efficiently cleave pre-miRNA, but that inorganic phosphate and the Dicer-2 partner protein R2D2 inhibit pre-miRNA cleavage. Dicer-2 contains C-terminal RNase III domains that mediate RNA cleavage and an N-terminal helicase motif, whose function is unclear. We show that Dicer-2 is a dsRNA-stimulated ATPase that hydrolyzes ATP to ADP; ATP hydrolysis is required for Dicer-2 to process long dsRNA, but not pre-miRNA. Wild-type Dicer-2, but not a mutant defective in ATP hydrolysis, can generate siRNAs faster than it can dissociate from a long dsRNA substrate. We propose that the Dicer-2 helicase domain uses ATP to generate many siRNAs from a single molecule of dsRNA before dissociating from its substrate.
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Affiliation(s)
- Elif Sarinay Cenik
- Department of Biochemistry and Molecular Pharmacology and Howard Hughes Medical Institute, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
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34
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Hartig JV, Förstemann K. Loqs-PD and R2D2 define independent pathways for RISC generation in Drosophila. Nucleic Acids Res 2011; 39:3836-51. [PMID: 21245036 PMCID: PMC3089465 DOI: 10.1093/nar/gkq1324] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In Drosophila, siRNAs are classified as endo- or exo-siRNAs based on their origin. Both are processed from double-stranded RNA precursors by Dcr-2 and then loaded into the Argonaute protein Ago2. While exo-siRNAs serve to defend the cell against viruses, endo-siRNAs restrict the spread of selfish DNA in somatic cells, analogous to piRNAs in the germ line. Endo- and exo-siRNAs display a differential requirement for double-stranded RNA binding domain proteins (dsRBPs): R2D2 is needed to load exo-siRNAs into Ago2 while the PD isoform of Loquacious (Loqs-PD) stimulates Dcr-2 during the nucleolytic processing of hairpin-derived endo-siRNAs. In cell culture assays, R2D2 antagonizes Loqs-PD in endo-siRNA silencing and Loqs-PD is an inhibitor of RNA interference. Loqs-PD can interact via the C-terminus unique to this isoform with the DExH/D-helicase domain of Drosophila Dcr-2, where binding of R2D2 has also been localized. Separation of the two pathways is not complete; rather, the dicing and Ago2-loading steps appear uncoupled, analogous to the corresponding steps in miRNA biogenesis. Analysis of deep sequencing data further demonstrates that in r2d2 mutant flies, siRNAs can be loaded into Ago2 but not all siRNA classes are equally proficient for this. Thus, the canonical Ago2-RISC loading complex can be bypassed under certain circumstances.
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Affiliation(s)
- Julia V Hartig
- Gene Center and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Str. 25, 81377 Munich, Germany
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35
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Wang TY, Dong YY, Li HY, Li XK. [Molecular evolution and regulatory mechanism of microRNAs]. YI CHUAN = HEREDITAS 2010; 32:874-80. [PMID: 20870607 DOI: 10.3724/sp.j.1005.2010.00874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
MicroRNAs, a type of small non-coding RNA specialized in regulation of gene expression, extensively participate in biological development, cell differentiation, apoptosis, and other cellular processes. MiRNAs evolved independently in different strains and generally conserved in the process of evolution. This review summarized the origin, regulation of methylation, and evolutionary conservation of miRNAs. In addition, application of miRNAs in diseases, animals and plants was discussed.
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Affiliation(s)
- Tian-Yu Wang
- Engineering Research Center of Bioreactor and Pharmaceutical Development, Ministry of Education, Jilin Agricultural University, Changchun 130118, China.
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36
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Chakravarthy S, Sternberg SH, Kellenberger CA, Doudna JA. Substrate-specific kinetics of Dicer-catalyzed RNA processing. J Mol Biol 2010; 404:392-402. [PMID: 20932845 DOI: 10.1016/j.jmb.2010.09.030] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 09/07/2010] [Accepted: 09/14/2010] [Indexed: 12/21/2022]
Abstract
The specialized ribonuclease Dicer plays a central role in eukaryotic gene expression by producing small regulatory RNAs-microRNAs (miRNAs) and short interfering RNAs (siRNAs)-from larger double-stranded RNA (dsRNA) substrates. Although Dicer will cleave both imperfectly base-paired hairpin structures (pre-miRNAs) and perfect duplexes (pre-siRNAs) in vitro, it has not been clear whether these are mechanistically equivalent substrates and how dsRNA binding proteins such as trans-activation response (TAR) RNA binding protein (TRBP) influence substrate selection and RNA processing efficiency. We show here that human Dicer is much faster at processing a pre-miRNA substrate compared to a pre-siRNA substrate under both single and multiple turnover conditions. Maximal cleavage rates (V(max)) calculated by Michaelis-Menten analysis differed by more than 100-fold under multiple turnover conditions. TRBP was found to enhance dicing of both substrates to similar extents, and this stimulation required the two N-terminal dsRNA binding domains of TRBP. These results demonstrate that multiple factors influence dicing kinetics. While TRBP stimulates dicing by enhancing the stability of Dicer-substrate complexes, Dicer itself generates product RNAs at rates determined at least in part by the structural properties of the substrate.
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Abstract
The discovery of RNA interference (RNAi) is among the most significant biomedical breakthroughs in recent history. Multiple classes of small RNA, including small-interfering RNA (siRNA), micro-RNA (miRNA), and piwi-interacting RNA (piRNA), play important roles in many fundamental biological and disease processes. Collective studies in multiple organisms, including plants, Drosophila, Caenorhabditis elegans, and mammals indicate that these pathways are highly conserved throughout evolution. Thus, scientists across disciplines have found novel pathways to unravel, new insights in probing pathology, and nascent technologies to develop. The field of RNAi also provides a clear framework for understanding fundamental principles of biochemistry. The current review highlights elegant, reason-based experimentation in discovering RNA-directed biological phenomena and the importance of robust assay development in translating these observations into mechanistic understanding. This biochemical template also provides a conceptual framework for overcoming emerging challenges in the field and for understanding an expanding small RNA world.
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Affiliation(s)
- Qinghua Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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38
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Welker NC, Pavelec DM, Nix DA, Duchaine TF, Kennedy S, Bass BL. Dicer's helicase domain is required for accumulation of some, but not all, C. elegans endogenous siRNAs. RNA (NEW YORK, N.Y.) 2010; 16:893-903. [PMID: 20354150 PMCID: PMC2856884 DOI: 10.1261/rna.2122010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Years after the discovery that Dicer is a key enzyme in gene silencing, the role of its helicase domain remains enigmatic. Here we show that this domain is critical for accumulation of certain endogenous small interfering RNAs (endo-siRNAs) in Caenorhabditis elegans. The domain is required for the production of the direct products of Dicer, or primary endo-siRNAs, and consequently affects levels of downstream intermediates, the secondary endo-siRNAs. Consistent with the role of endo-siRNAs in silencing, their loss correlates with an increase in cognate mRNA levels. We find that the helicase domain of Dicer is not necessary for microRNA (miRNA) processing, or RNA interference following exposure to exogenous double-stranded RNA. Comparisons of wild-type and helicase-defective strains using deep-sequencing analyses show that the helicase domain is required by a subset of annotated endo-siRNAs, in particular, those associated with the slightly longer 26-nucleotide small RNA species containing a 5' guanosine.
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MESH Headings
- Amino Acid Sequence
- Animals
- Animals, Genetically Modified
- Caenorhabditis elegans/genetics
- Caenorhabditis elegans/metabolism
- Gene Deletion
- Genes, Helminth
- MicroRNAs/genetics
- MicroRNAs/metabolism
- Molecular Sequence Data
- Point Mutation
- Protein Structure, Tertiary
- RNA Helicases/chemistry
- RNA Helicases/genetics
- RNA Helicases/metabolism
- RNA Interference
- RNA Processing, Post-Transcriptional
- RNA, Helminth/genetics
- RNA, Helminth/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- Ribonuclease III/chemistry
- Ribonuclease III/genetics
- Ribonuclease III/metabolism
- Sequence Homology, Amino Acid
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Affiliation(s)
- Noah C Welker
- 1Department of Biochemistry, University of Utah, Salt Lake City, Utah 84112, USA
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39
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Abstract
An enzyme that cleaves RNA is converted to a DNA-cleaving enzyme during programmed cell death in
Caenorhabditis elegans
.
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Affiliation(s)
- Qinghua Liu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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40
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Miyoshi K, Miyoshi T, Hartig JV, Siomi H, Siomi MC. Molecular mechanisms that funnel RNA precursors into endogenous small-interfering RNA and microRNA biogenesis pathways in Drosophila. RNA (NEW YORK, N.Y.) 2010; 16:506-15. [PMID: 20086050 PMCID: PMC2822916 DOI: 10.1261/rna.1952110] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 11/25/2009] [Indexed: 05/20/2023]
Abstract
In Drosophila, three types of endogenous small RNAs-microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), and endogenous small-interfering RNAs (endo-siRNAs or esiRNAs)-function as triggers in RNA silencing. Although piRNAs are produced independently of Dicer, miRNA and esiRNA biogenesis pathways require Dicer1 and Dicer2, respectively. Recent studies have shown that among the four isoforms of Loquacious (Loqs), Loqs-PB and Loqs-PD are involved in miRNA and esiRNA processing pathways, respectively. However, how these Loqs isoforms function in their respective small RNA biogenesis pathways remains elusive. Here, we show that Loqs-PD associates specifically with Dicer2 through its C-terminal domain. The Dicer2-Loqs-PD complex contains R2D2, another known Dicer2 partner, and excises both exogenous siRNAs and esiRNAs from their corresponding precursors in vitro. However, Loqs-PD, but not R2D2, enhanced Dicer2 activity. The Dicer2-Loqs-PD complex processes esiRNA precursor hairpins with long stems, which results in the production of AGO2-associated small RNAs. Interestingly, however, small RNAs derived from terminal hairpins of esiRNA precursors are loaded onto AGO1; thus, they are classified as a new subset of miRNAs. These results suggest that the precursor RNA structure determines the biogenesis mechanism of esiRNAs and miRNAs, thereby implicating hairpin structures with long stems as intermediates in the evolution of Drosophila miRNA.
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Affiliation(s)
- Keita Miyoshi
- Keio University School of Medicine, Tokyo 160-8582, Japan
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Qin H, Chen F, Huan X, Machida S, Song J, Yuan YA. Structure of the Arabidopsis thaliana DCL4 DUF283 domain reveals a noncanonical double-stranded RNA-binding fold for protein-protein interaction. RNA (NEW YORK, N.Y.) 2010; 16:474-81. [PMID: 20106953 PMCID: PMC2822912 DOI: 10.1261/rna.1965310] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Accepted: 12/07/2009] [Indexed: 05/19/2023]
Abstract
Dicer or Dicer-like (DCL) protein is a catalytic component involved in microRNA (miRNA) or small interference RNA (siRNA) processing pathway, whose fragment structures have been partially solved. However, the structure and function of the unique DUF283 domain within dicer is largely unknown. Here we report the first structure of the DUF283 domain from the Arabidopsis thaliana DCL4. The DUF283 domain adopts an alpha-beta-beta-beta-alpha topology and resembles the structural similarity to the double-stranded RNA-binding domain. Notably, the N-terminal alpha helix of DUF283 runs cross over the C-terminal alpha helix orthogonally, therefore, N- and C-termini of DUF283 are in close proximity. Biochemical analysis shows that the DUF283 domain of DCL4 displays weak dsRNA binding affinity and specifically binds to double-stranded RNA-binding domain 1 (dsRBD1) of Arabidopsis DRB4, whereas the DUF283 domain of DCL1 specifically binds to dsRBD2 of Arabidopsis HYL1. These data suggest a potential functional role of the Arabidopsis DUF283 domain in target selection in small RNA processing.
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Affiliation(s)
- Haina Qin
- Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
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Structure of the human Dicer-TRBP complex by electron microscopy. Structure 2010; 17:1326-32. [PMID: 19836333 DOI: 10.1016/j.str.2009.08.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 08/24/2009] [Accepted: 08/24/2009] [Indexed: 11/22/2022]
Abstract
Dicer is a specialized ribonuclease that initiates RNA interference (RNAi) by cleaving double-stranded RNA (dsRNA) into small RNA fragments about 22 nucleotides long. Here, we present the three-dimensional structure of human Dicer bound to the protein TRBP at approximately 20 A resolution determined by negative-stain electron microscopy (EM) and single-particle analysis. Our analysis reveals that the Dicer-TRBP complex is an L-shaped molecule with a long edge of 150 A and a 100 A extension on one end. A surface trench runs the length of the long edge of the molecule, defining a putative dsRNA-binding site. Docking the crystal structure of Giardia Dicer, which represents the nuclease core of human Dicer, into the EM map suggests two possible overall molecular architectures for human Dicer. These results offer insights into the structure of Dicer proteins found in multicellular organisms and provide a conceptual framework for understanding the initiation of RNAi.
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Wu H, Ye C, Ramirez D, Manjunath N. Alternative processing of primary microRNA transcripts by Drosha generates 5' end variation of mature microRNA. PLoS One 2009; 4:e7566. [PMID: 19859542 PMCID: PMC2762519 DOI: 10.1371/journal.pone.0007566] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 09/29/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND It is generally believed that the miRNA processing machinery ensures the generation of a mature miRNA with a fixed sequence, particularly at its 5' end. However, we and others have recently noted that the ends of a given mature miRNA are not absolutely fixed, but subject to variation. Neither the significance nor the mechanism behind the generation of such miRNA polymorphism is understood. miR-142 is an abundantly expressed miRNA in hematopoietic cells and exhibits a high frequency of 5' end polymorphism. METHODOLOGY/PRINCIPAL FINDINGS Here we show that a shift in the Drosha processing of pri-miRNA generates multiple forms of miR-142s in vivo with differing 5' ends that might target different genes. Sequence analysis of several pre-miRNA ends cloned from T cells reveals that unlike many other pri-miRNAs that are processed into a single pre-miRNA, pri-miR-142 is processed into 3 distinct pre-miR-142s. Dicer processing studies suggest that each of the 3 pre-miR-142s is processed into a distinct double-stranded miRNA, giving rise to 4 mature miRNA variants that might regulate different target gene pools. CONCLUSIONS/SIGNIFICANCE Thus, alternative Drosha processing might be a novel mechanism for diversification of the miRNA target gene pool.
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Affiliation(s)
- Haoquan Wu
- Center of Excellence in Infectious Disease Research, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas, United States of America
- * E-mail: (NM); (HW)
| | - Chunting Ye
- Center of Excellence in Infectious Disease Research, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas, United States of America
| | - Danielle Ramirez
- Center of Excellence in Infectious Disease Research, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas, United States of America
| | - N. Manjunath
- Center of Excellence in Infectious Disease Research, Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center, El Paso, Texas, United States of America
- * E-mail: (NM); (HW)
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Zhou R, Czech B, Brennecke J, Sachidanandam R, Wohlschlegel JA, Perrimon N, Hannon GJ. Processing of Drosophila endo-siRNAs depends on a specific Loquacious isoform. RNA (NEW YORK, N.Y.) 2009; 15:1886-95. [PMID: 19635780 PMCID: PMC2743050 DOI: 10.1261/rna.1611309] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Accepted: 06/30/2009] [Indexed: 05/20/2023]
Abstract
Drosophila melanogaster expresses three classes of small RNAs, which are classified according to their mechanisms of biogenesis. MicroRNAs are approximately 22-23 nucleotides (nt), ubiquitously expressed small RNAs that are sequentially processed from hairpin-like precursors by Drosha/Pasha and Dcr-1/Loquacious complexes. MicroRNAs usually associate with AGO1 and regulate the expression of protein-coding genes. Piwi-interacting RNAs (piRNAs) of approximately 24-28 nt associate with Piwi-family proteins and can arise from single-stranded precursors. piRNAs function in transposon silencing and are mainly restricted to gonadal tissues. Endo-siRNAs are found in both germline and somatic tissues. These approximately 21-nt RNAs are produced by a distinct Dicer, Dcr-2, and do not depend on Drosha/Pasha complexes. They predominantly bind to AGO2 and target both mobile elements and protein-coding genes. Surprisingly, a subset of endo-siRNAs strongly depend for their production on the dsRNA-binding protein Loquacious (Loqs), thought generally to be a partner for Dcr-1 and a cofactor for miRNA biogenesis. Endo-siRNA production depends on a specific Loqs isoform, Loqs-PD, which is distinct from the one, Loqs-PB, required for the production of microRNAs. Paralleling their roles in the biogenesis of distinct small RNA classes, Loqs-PD and Loqs-PB bind to different Dicer proteins, with Dcr-1/Loqs-PB complexes and Dcr-2/Loqs-PD complexes driving microRNA and endo-siRNA biogenesis, respectively.
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Affiliation(s)
- Rui Zhou
- Harvard Medical School, Department of Genetics, Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
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Flores-jasso CF, Arenas-huertero C, Reyes JL, Contreras-cubas C, Covarrubias A, Vaca L. First step in pre-miRNAs processing by human Dicer. Acta Pharmacol Sin 2009; 30:1177-85. [PMID: 19654583 DOI: 10.1038/aps.2009.108] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
AIM To investigate the strand preference of the initial cleavage of human pre-miRNAs by human Dicer in vitro. METHODS We used a series of in vitro transcribed pre-miRNAs that were radioactively labeled at their 5' or 3' ends in cleavage reactions with recombinant human Dicer or HeLa cytoplasmic S100 extracts. Pre-miRNAs samples were purified by denaturing and native PAGE and only the stem-loop structures were used in the experiments. Products of cleavage reactions were resolved by denaturing PAGE, and scanned by phosphor-imaging. RESULTS Recombinant hDicer performs a biased first-cleavage in the pre-let-7b and hsa-pre-miR-17 3' strand. This result is recapitulated in HeLa S100 cytoplasmic extracts. CONCLUSION The differential first-nick is observed in cleavage reactions only when stem-loops are substrates for hDicer.
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Abstract
MicroRNAs (miRNA) are small RNAs that regulate the translation of thousands of message RNAs and play a profound role in mammalian biology. Over the past 5 years, significant advances have been made towards understanding the pathways that generate miRNAs and the mechanisms by which miRNAs exert their regulatory functions. An emerging theme is that miRNAs are both generated by and utilized by large and complex macromolecular assemblies. Here, we review the biology of mammalian miRNAs with a focus on the macromolecular complexes that generate and control the biogenesis of miRNAs.
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Affiliation(s)
- Pick-Wei Lau
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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Ma E, MacRae IJ, Kirsch JF, Doudna JA. Autoinhibition of human dicer by its internal helicase domain. J Mol Biol 2008; 380:237-43. [PMID: 18508075 DOI: 10.1016/j.jmb.2008.05.005] [Citation(s) in RCA: 178] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2008] [Revised: 05/02/2008] [Accepted: 05/02/2008] [Indexed: 10/22/2022]
Abstract
Dicer, a member of the ribonuclease III family of enzymes, processes double-stranded RNA substrates into approximately 21- to 27-nt products that trigger sequence-directed gene silencing by RNA interference. Although the mechanism of RNA recognition and length-specific cleavage by Dicer has been established, the way in which dicing activity is regulated is unclear. Here, we show that the N-terminal domain of human Dicer, which is homologous to DExD/H-box helicases, substantially attenuates the rate of substrate cleavage. Deletion or mutation of this domain activates human Dicer in both single- and multiple-turnover assays. The catalytic efficiency (k(cat)/K(m)) of the deletion construct is increased by 65-fold over that exhibited by the intact enzyme. Kinetic analysis shows that this activation is almost entirely due to an enhancement in k(cat). Modest stimulation of catalysis by the full-length Dicer enzyme was observed in the presence of the TAR-RNA binding protein, which physically interacts with the DExD/H-box domain. These results suggest that the DExD/H-box domain likely disrupts the functionality of the Dicer active site until a structural rearrangement occurs, perhaps upon assembly with its molecular partners.
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Affiliation(s)
- Enbo Ma
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3206, USA
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