501
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van Rij RP, Andino R. The silent treatment: RNAi as a defense against virus infection in mammals. Trends Biotechnol 2006; 24:186-93. [PMID: 16503061 DOI: 10.1016/j.tibtech.2006.02.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2005] [Revised: 11/25/2005] [Accepted: 02/13/2006] [Indexed: 12/22/2022]
Abstract
RNA interference (RNAi) is a mechanism for sequence-specific gene silencing guided by double-stranded RNA. In plants and insects it is well established that RNAi is instrumental in the response to viral infections; whether RNAi has a similar function in mammals is under intense investigation. Recent studies to address this question have identified some unanticipated interactions between the RNAi machinery and mammalian viruses. Furthermore, introduction of virus-specific small interfering RNAs (siRNAs) into cells, thus programming the RNAi machinery to target viruses, is an effective therapeutic approach to inhibit virus replication in vitro and in animal models. Although several issues remain to be addressed, such as delivery and viral escape, these findings hold tremendous potential for the development of RNAi-based antiviral therapeutics.
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Affiliation(s)
- Ronald P van Rij
- Department of Microbiology and Immunology, University of California-San Francisco, San Francisco, CA 94143-2280, USA
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502
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Lingel A, Simon B, Izaurralde E, Sattler M. The structure of the flock house virus B2 protein, a viral suppressor of RNA interference, shows a novel mode of double-stranded RNA recognition. EMBO Rep 2006; 6:1149-55. [PMID: 16270100 PMCID: PMC1369214 DOI: 10.1038/sj.embor.7400583] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Revised: 10/18/2005] [Accepted: 10/19/2005] [Indexed: 11/08/2022] Open
Abstract
We report the structure of the flock house virus B2 protein, a potent suppressor of RNA interference (RNAi) in animals and plants. The B2 protein is a homodimer in solution and contains three alpha-helices per monomer. Chemical shift perturbation shows that an antiparallel arrangement of helices (alpha2/alpha2') forms an elongated binding interface with double-stranded RNA (dsRNA). This implies a novel mode of dsRNA recognition and provides insights into the mechanism of RNAi suppression by B2.
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MESH Headings
- Amino Acid Sequence
- Amino Acids/chemistry
- Amino Acids, Aromatic/chemistry
- Dimerization
- Hydrophobic and Hydrophilic Interactions
- Models, Molecular
- Nuclear Magnetic Resonance, Biomolecular
- Protein Binding
- Protein Conformation
- Protein Folding
- Protein Structure, Secondary
- Protein Subunits/chemistry
- RNA Interference
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/metabolism
- RNA, Small Interfering/chemistry
- RNA, Small Interfering/metabolism
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Solutions
- Spectrum Analysis, Raman
- Static Electricity
- Viral Proteins/chemistry
- Viral Proteins/isolation & purification
- Viral Proteins/metabolism
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Affiliation(s)
- Andreas Lingel
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Bernd Simon
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Elisa Izaurralde
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Tel: +49 6221 388 103; Fax: +49 6221 387 306; E-mail:
| | - Michael Sattler
- European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
- Tel: +49 6221 387 552; Fax: +49 6221 387 306; E-mail:
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503
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Yeung ML, Bennasser Y, LE SY, Jeang KT. siRNA, miRNA and HIV: promises and challenges. Cell Res 2006; 15:935-46. [PMID: 16354572 DOI: 10.1038/sj.cr.7290371] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Small interfering RNA (siRNA) and microRNA (miRNA) are small RNAs of 18-25 nucleotides (nt) in length that play important roles in regulating gene expression. They are incorporated into an RNA-induced silencing complex (RISC) and serve as guides for silencing their corresponding target mRNAs based on complementary base-pairing. The promise of gene silencing has led many researchers to consider siRNA as an anti-viral tool. However, in long-term settings, many viruses appear to escape from this therapeutical strategy. An example of this may be seen in the case of human immunodeficiency virus type-1 (HIV-1) which is able to evade RNA silencing by either mutating the siRNA-targeted sequence or by encoding for a partial suppressor of RNAi (RNA interference). On the other hand, because miRNA targeting does not require absolute complementarity of base-pairing, mutational escape by viruses from miRNA-specified silencing may be more difficult to achieve. In this review, we discuss stratagems used by various viruses to avoid the cells' antiviral si/mi-RNA defenses and notions of how viruses might control and regulate host cell genes by encoding viral miRNAs (vmiRNAs).
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Affiliation(s)
- Man Lung Yeung
- National Institute of Allergy and Infectious Diseases, National Institutes of Health Bethesda, Maryland 20892-0460, USA
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504
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Pazhouhandeh M, Dieterle M, Marrocco K, Lechner E, Berry B, Brault V, Hemmer O, Kretsch T, Richards KE, Genschik P, Ziegler-Graff V. F-box-like domain in the polerovirus protein P0 is required for silencing suppressor function. Proc Natl Acad Sci U S A 2006; 103:1994-9. [PMID: 16446454 PMCID: PMC1413668 DOI: 10.1073/pnas.0510784103] [Citation(s) in RCA: 224] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Indexed: 12/31/2022] Open
Abstract
Plants employ small RNA-mediated posttranscriptional gene silencing as a virus defense mechanism. In response, plant viruses encode proteins that can suppress RNA silencing, but the mode of action of most such proteins is poorly understood. Here, we show that the silencing suppressor protein P0 of two Arabidopsis-infecting poleroviruses interacts by means of a conserved minimal F-box motif with Arabidopsis thaliana orthologs of S-phase kinase-related protein 1 (SKP1), a component of the SCF family of ubiquitin E3 ligases. Point mutations in the F-box-like motif abolished the P0-SKP1 ortholog interaction, diminished virus pathogenicity, and inhibited the silencing suppressor activity of P0. Knockdown of expression of a SKP1 ortholog in Nicotiana benthamiana rendered the plants resistant to polerovirus infection. Together, the results support a model in which P0 acts as an F-box protein that targets an essential component of the host posttranscriptional gene silencing machinery.
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Affiliation(s)
- Maghsoud Pazhouhandeh
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Monika Dieterle
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Katia Marrocco
- Institut für Biologie 2/Botanik, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany; and
| | - Esther Lechner
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Bassam Berry
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Véronique Brault
- Institut National de la Recherche Agronomique, 28 Rue de Herrlisheim, 68021 Colmar, France
| | - Odile Hemmer
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Thomas Kretsch
- Institut für Biologie 2/Botanik, Albert-Ludwigs-Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany; and
| | - Kenneth E. Richards
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Pascal Genschik
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
| | - Véronique Ziegler-Graff
- *Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, 12 Rue du Général Zimmer, 67084 Strasbourg, France
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505
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Popova B, Kuhlmann M, Hinas A, Söderbom F, Nellen W. HelF, a putative RNA helicase acts as a nuclear suppressor of RNAi but not antisense mediated gene silencing. Nucleic Acids Res 2006; 34:773-84. [PMID: 16456031 PMCID: PMC1360742 DOI: 10.1093/nar/gkj465] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We have identified a putative RNA helicase from Dictyostelium that is closely related to drh-1, the 'dicer-related-helicase' from Caenorhabditis elegans and that also has significant similarity to proteins from vertebrates and plants. Green fluorescent protein (GFP)-tagged HelF protein was localized in speckles in the nucleus. Disruption of the helF gene resulted in a mutant morphology in late development. When transformed with RNAi constructs, HelF- cells displayed enhanced RNA interference on four tested genes. One gene that could not be knocked-down in the wild-type background was efficiently silenced in the mutant. Furthermore, the efficiency of silencing in the wild-type was dramatically improved when helF was disrupted in a secondary transformation. Silencing efficiency depended on transcription levels of hairpin RNA and the threshold was dramatically reduced in HelF- cells. However, the amount of siRNA did not depend on hairpin transcription. HelF is thus a natural nuclear suppressor of RNA interference. In contrast, no improvement of gene silencing was observed when mutant cells were challenged with corresponding antisense constructs. This indicates that RNAi and antisense have distinct requirements even though they may share parts of their pathways.
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Affiliation(s)
| | | | - Andrea Hinas
- Department of Molecular Biology, Biomedical Center, Swedish University of Agricultural SciencesBox 590, S-75124 Uppsala, Sweden
| | - Fredrik Söderbom
- Department of Molecular Biology, Biomedical Center, Swedish University of Agricultural SciencesBox 590, S-75124 Uppsala, Sweden
| | - Wolfgang Nellen
- To whom correspondence should be addressed. Tel: +49 0 561 804 4805; Fax: +49 0 561 804 4800;
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506
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Dunoyer P, Himber C, Voinnet O. Induction, suppression and requirement of RNA silencing pathways in virulent Agrobacterium tumefaciens infections. Nat Genet 2006; 38:258-63. [PMID: 16429161 DOI: 10.1038/ng1722] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2005] [Accepted: 10/17/2005] [Indexed: 11/08/2022]
Abstract
Regulation of gene expression through microRNAs (miRNAs) and antiviral defense through small interfering RNAs (siRNAs) are aspects of RNA silencing, a process originally discovered as an unintended consequence of plant transformation by disarmed Agrobacterium tumefaciens strains. Although RNA silencing protects cells against foreign genetic elements, its defensive role against virulent, tumor-inducing bacteria has remained unexplored. Here, we show that siRNAs corresponding to transferred-DNA oncogenes initially accumulate in virulent A. tumefaciens-infected tissues and that RNA interference-deficient plants are hypersusceptible to the pathogen. Successful infection relies on a potent antisilencing state established in tumors whereby siRNA synthesis is specifically inhibited. This inhibition has only modest side effects on the miRNA pathway, shown here to be essential for disease development. The similarities and specificities of the A. tumefaciens RNA silencing interaction are discussed and contrasted with the situation encountered with plant viruses.
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507
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Abstract
The availability of the human genome sequence has revolutionized the strategy of employing nucleic acids with sequences complementary to specific target genes to improve drug discovery and target validation. Development of sequence-specific DNA or RNA analogs that can block the activity of selected single-stranded genetic sequences offers the possibility of rational design with high specificity, lacking in many current drug treatments for various diseases including cancer, at relatively inexpensive costs. Antisense technology is one such example that has shown promising results and boasts of yielding the only approved drug to date in the genomics field. However, in vivo delivery issues have yet to be completely overcome for widespread clinical applications. In contrast to antisense oligonucleotides, the mechanism of silencing an endogenous gene by the introduction of a homologous double-stranded RNA (dsRNA), transgene or virus is called post-transcriptional gene silencing (PTGS) or RNA interference. PTGS is a natural mechanism whereby metazoan cells suppress expansion of genes when they come across dsRNA molecules with the same sequence. Short interfering RNA is currently the fastest growing sector of this antigene field for target validation and therapeutic applications. Although, in theory, the development of genomics-based agents to inhibit gene expression is simple and straightforward, the fundamental concern relies upon the capacity of the oligonucleotide to gain access to the target RNA. This paper summarizes the advances in the last decade in the field of PTGS using RNA interference approaches and provides relevant comparisons with other oligonucleotide-based approaches with a specific focus on oncology applications.
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Affiliation(s)
- G R Devi
- Comprehensive Cancer Center, Duke University Medical Center, Durham, NC 27710, USA.
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508
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Akbergenov R, Si-Ammour A, Blevins T, Amin I, Kutter C, Vanderschuren H, Zhang P, Gruissem W, Meins F, Hohn T, Pooggin MM. Molecular characterization of geminivirus-derived small RNAs in different plant species. Nucleic Acids Res 2006; 34:462-71. [PMID: 16421273 PMCID: PMC1342034 DOI: 10.1093/nar/gkj447] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 12/23/2005] [Accepted: 01/03/2006] [Indexed: 11/23/2022] Open
Abstract
DNA geminiviruses are thought to be targets of RNA silencing. Here, we characterize small interfering (si) RNAs-the hallmarks of silencing-associated with Cabbage leaf curl begomovirus in Arabidopsis and African cassava mosaic begomovirus in Nicotiana benthamiana and cassava. We detected 21, 22 and 24 nt siRNAs of both polarities, derived from both the coding and the intergenic regions of these geminiviruses. Genetic evidence showed that all the 24 nt and a substantial fraction of the 22 nt viral siRNAs are generated by the dicer-like proteins DCL3 and DCL2, respectively. The viral siRNAs were 5' end phosphorylated, as shown by phosphatase treatments, and methylated at the 3'-nucleotide, as shown by HEN1 miRNA methylase-dependent resistance to beta-elimination. Similar modifications were found in all types of endogenous and transgene-derived siRNAs tested, but not in a major fraction of siRNAs from a cytoplasmic RNA tobamovirus. We conclude that several distinct silencing pathways are involved in DNA virus-plant interactions.
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Affiliation(s)
- Rashid Akbergenov
- Institute of Botany, University of BaselSchönbeinstrasse 6, 4056 Basel, Switzerland
| | - Azeddine Si-Ammour
- Friedrich Miescher Institute for Biomedical ResearchMaulbeerstrasse 66, 4058 Basel, Switzerland
| | - Todd Blevins
- Friedrich Miescher Institute for Biomedical ResearchMaulbeerstrasse 66, 4058 Basel, Switzerland
| | - Imran Amin
- Institute of Botany, University of BaselSchönbeinstrasse 6, 4056 Basel, Switzerland
| | - Claudia Kutter
- Friedrich Miescher Institute for Biomedical ResearchMaulbeerstrasse 66, 4058 Basel, Switzerland
| | - Herve Vanderschuren
- Institute of Plant Sciences, ETH-Zurich, LFW E17, Universitätstrasse 28092 Zürich, Switzerland
| | - Peng Zhang
- Institute of Plant Sciences, ETH-Zurich, LFW E17, Universitätstrasse 28092 Zürich, Switzerland
| | - Wilhelm Gruissem
- Institute of Plant Sciences, ETH-Zurich, LFW E17, Universitätstrasse 28092 Zürich, Switzerland
| | - Frederick Meins
- Friedrich Miescher Institute for Biomedical ResearchMaulbeerstrasse 66, 4058 Basel, Switzerland
| | - Thomas Hohn
- Institute of Botany, University of BaselSchönbeinstrasse 6, 4056 Basel, Switzerland
- Friedrich Miescher Institute for Biomedical ResearchMaulbeerstrasse 66, 4058 Basel, Switzerland
| | - Mikhail M. Pooggin
- Institute of Botany, University of BaselSchönbeinstrasse 6, 4056 Basel, Switzerland
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509
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Teycheney PY, Laboureau N, Iskra-Caruana ML, Candresse T. High genetic variability and evidence for plant-to-plant transfer of Banana mild mosaic virus. J Gen Virol 2006; 86:3179-3187. [PMID: 16227242 DOI: 10.1099/vir.0.81197-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A total of 154 partial nucleotide sequences within the Banana mild mosaic virus (BanMMV) ORF1, which encodes the viral RNA-dependent RNA polymerase (RdRp), was obtained from 68 distinct infected banana accessions originating from various locations worldwide. The 310 nt sequences displayed a high level of variability with a mean pairwise nucleotide sequence divergence level of 20.4 %. This situation resulted essentially from a high rate of synonymous mutations. A similar analysis was performed for a limited selection of 10 banana accessions (30 sequences) on the region comprising approximately the last 310 nt of the BanMMV genome. This region corresponds to the 3' end of ORF5, which encodes the coat protein (234 nt), and to the 3' non-coding region. This analysis confirmed the high level of diversity observed in the RdRp dataset, characterized by a high level of synonymous mutations. Analysis of intra-host diversity indicated the existence of two distinct situations, with some plants containing only closely related sequence variants, whereas others contained widely divergent isolates. Analyses indicated that BanMMV genetic diversity is not structured by the geographical origin of the infected Musa accessions or by their genotype. This situation may be, in part, explained by the exchange of banana germplasm between different parts of the world and also by plant-to-plant transfer of virus isolates, the evidence for which is, for the first time, provided by this study.
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Affiliation(s)
- Pierre-Yves Teycheney
- CIRAD, UPR 75, Station de Neufchâteau, Sainte-Marie, F-97130 Capesterre Belle-Eau, Guadeloupe, French West Indies
| | - Nathalie Laboureau
- CIRAD/UMR BGPI, TA 41/K, Campus International de Baillarguet, F-34398 Montpellier Cedex, France
| | | | - Thierry Candresse
- UMR GD2P, INRA et Université Bordeaux 2, IBVM, Campus INRA de la Grande Ferrade, BP 81, F-33883 Villenave d'Ornon Cedex, France
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510
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Abstract
Interest in insect small RNA viruses (SRVs) has grown slowly but steadily. A number of new viruses have been analyzed at the sequence level, adding to our knowledge of their diversity at the level of both individual virus species and families. In particular, a number of possible new virus families have emerged. This research has largely been driven by interest in their potential for pest control, as well as in their importance as the causal agents of disease in beneficial arthropods. At the same time, research into known viruses has made valuable contributions to our understanding of an emerging new field of central importance to molecular biology-the existence of RNA-based gene silencing, developmental control, and adaptive immune systems in eukaryotes. Subject to RNA-based adaptive immune responses in their hosts, viruses have evolved a variety of genes encoding proteins capable of suppressing the immune response. Such genes were first identified in plant viruses, but the first examples known from animal viruses were identified in insect RNA viruses. This chapter will address the diversity of insect SRVs, and attempts to harness their simplicity in the engineering of transgenic plants expressing viruses for resistance to insect pests. We also describe RNA interference and antiviral pathways identified in plants and animals, how they have led viruses to evolve genes capable of suppressing such adaptive immunity, and the problems presented by these pathways for the strategy of expressing viruses in transgenic plants. Approaches for countering these problems are also discussed.
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511
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Schütz S, Sarnow P. Interaction of viruses with the mammalian RNA interference pathway. Virology 2006; 344:151-7. [PMID: 16364746 DOI: 10.1016/j.virol.2005.09.034] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2005] [Accepted: 09/14/2005] [Indexed: 01/24/2023]
Abstract
It has been known for some time that plants and insects use RNA interference (RNAi) as nucleic acid-based immunity against viral infections. However, it was unknown whether mammalian cells employ the RNA interference pathway as an antiviral mechanism as well. Over the past years, it has become clear that a variety of viruses, first in plants but recently in insect and mammalian viruses as well, encode suppressors of the RNAi pathway arguing for an antiviral role of this machinery. More recent findings have revealed that certain viruses encode their own microRNAs or microRNA-like RNA molecules, which are processed by the mammalian RNAi machinery. Furthermore, host-encoded microRNAs have been shown to both silence and enhance intracellular levels of viral RNAs. These findings argue that interactions between the RNAi pathway and viral genomes can profoundly affect the outcomes of the viral life cycles and contribute to the pathogenic signatures of the infectious agents.
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Affiliation(s)
- Sylvia Schütz
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA
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512
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Danilova N. The evolution of immune mechanisms. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2006; 306:496-520. [PMID: 16619242 DOI: 10.1002/jez.b.21102] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
From early on in evolution, organisms have had to protect themselves from pathogens. Mechanisms for discriminating "self" from "non-self" evolved to accomplish this task, launching a long history of host-pathogen co-evolution. Evolution of mechanisms of immune defense has resulted in a variety of strategies. Even unicellular organisms have rich arsenals of mechanisms for protection, such as restriction endonucleases, antimicrobial peptides, and RNA interference. In multicellular organisms, specialized immune cells have evolved, capable of recognition, phagocytosis, and killing of foreign cells as well as removing their own cells changed by damage, senescence, infection, or cancer. Additional humoral factors, such as the complement cascade, have developed that co-operate with cellular immunity in fighting infection and maintaining homeostasis. Defensive mechanisms based on germline-encoded receptors constitute a system known as innate immunity. In jaw vertebrates, this system is supplemented with a second system, adaptive immunity, which in contrast to innate immunity is based on diversification of immune receptors and on immunological memory in each individual.Usually, each newly evolved defense mechanism did not replace the previous one, but supplemented it, resulting in a layered structure of the immune system. The immune system is not one system but rather a sophisticated network of various defensive mechanisms operating on different levels, ranging from mechanisms common for every cell in the body to specialized immune cells and responses at the level of the whole organism. Adaptive changes in pathogens have shaped the evolution of the immune system at all levels.
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Affiliation(s)
- Nadia Danilova
- Department of Molecular, Cell & Developmental Biology, University of California, Los Angeles, CA 90095-1606, USA.
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513
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Yeung ML, Bennasser Y, Myers TG, Jiang G, Benkirane M, Jeang KT. Changes in microRNA expression profiles in HIV-1-transfected human cells. Retrovirology 2005; 2:81. [PMID: 16381609 PMCID: PMC1352379 DOI: 10.1186/1742-4690-2-81] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Accepted: 12/28/2005] [Indexed: 11/10/2022] Open
Abstract
MicroRNAs (miRNAs) are small RNAs of 18–25 nucleotides (nt) in length that play important roles in regulating a variety of biological processes. Recent studies suggest that cellular miRNAs may serve to control the replication of viruses in cells. If such is the case, viruses might be expected to evolve the ability to modulate the expression of cellular miRNAs. To ask if expression of HIV-1 genes changes the miRNA profiles in human cells, we employed a high throughput microarray method, termed the RNA-primed Array-based Klenow Enzyme (RAKE) assay. Here, we describe the optimization of this assay to quantify the expression of miRNAs in HIV-1 transfected human cells. We report distinct differences in miRNA profiles in mock-transfected HeLa cells versus HeLa cells transfected with an infectious HIV-1 molecular clone, pNL4-3.
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Affiliation(s)
- Man Lung Yeung
- Molecular Virology Section, Laboratory of Molecular Microbiology National Institute of Allergy and Infectious Diseases, National Institutes of Health Bethesda, Maryland 20892-0460, USA
| | - Yamina Bennasser
- Molecular Virology Section, Laboratory of Molecular Microbiology National Institute of Allergy and Infectious Diseases, National Institutes of Health Bethesda, Maryland 20892-0460, USA
| | - Timothy G Myers
- Microarray Research Facility, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health Bethesda, Maryland 20892-8005, USA
| | - Guojian Jiang
- Microarray Research Facility, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health Bethesda, Maryland 20892-8005, USA
| | - Monsef Benkirane
- Laboratoire de Virologie Moleculaire, Institut de Genetique Humaine, CNRS UPR1142, Montpellier, France
| | - Kuan-Teh Jeang
- Molecular Virology Section, Laboratory of Molecular Microbiology National Institute of Allergy and Infectious Diseases, National Institutes of Health Bethesda, Maryland 20892-0460, USA
- Building 4, Room 306, 9000 Rockville Pike, Bethesda, MD 20892-0460, USA
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514
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Ryabova LA, Pooggin MM, Hohn T. Translation reinitiation and leaky scanning in plant viruses. Virus Res 2005; 119:52-62. [PMID: 16325949 DOI: 10.1016/j.virusres.2005.10.017] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 09/27/2005] [Accepted: 10/20/2005] [Indexed: 11/24/2022]
Abstract
While translation of mRNAs in eukaryotic cells in general follows strict rules, viruses infecting these cells break those rules in various ways. Viruses are under high selection pressure to compete with the host, to economize genome size, and to accommodate signals for replication, virus assembly, etc., on their RNAs as well as using them for translation. The cornucopia of extraordinary translation strategies, such as leaky scanning, internal initiation of translation, ribosome shunt, and virus-controlled reinitiation of translation, evolved by viruses continues to surprise and inform our understanding of general translation mechanisms. While internal initiation is treated in another section of this issue, we concentrate on leaky scanning, shunt and reinitiation, with emphasis on plant pararetroviruses.
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Affiliation(s)
- Lyubov A Ryabova
- Institut de Biologie Moléculaire des Plantes, UPR CNRS 2357, Strasbourg, France.
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515
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Abstract
MicroRNAs (miRNAs) play a pivotal role in the regulation of genes involved in diverse processes such as development, differentiation, and cellular growth control. Recently, many viral-encoded miRNAs have been discovered, for the most part in viruses transcribed from double-stranded DNA genomes. As with their cellular counterparts, the functions of most viral-derived miRNAs are unknown; however, functions have been documented or proposed for viral miRNAs from three different viral families-herpesviruses, polyomaviruses, and retroviruses. Several virus-encoded miRNAs have unique aspects to their biogenesis, such as the polymerase that transcribes them or their location within the precursor transcript. Additionally, viral interactions with cellular miRNAs have also been identified, and these have substantially expanded our appreciation of miRNA functions.
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Affiliation(s)
- Christopher S Sullivan
- Howard Hughes Medical Institute, Department of Microbiology, University of California, San Francisco, CA 94143, USA
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516
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Park GS, Best SM, Bloom ME. Two mink parvoviruses use different cellular receptors for entry into CRFK cells. Virology 2005; 340:1-9. [PMID: 16040076 DOI: 10.1016/j.virol.2005.06.038] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2005] [Revised: 05/02/2005] [Accepted: 06/16/2005] [Indexed: 12/01/2022]
Abstract
Mink enteritis virus (MEV) and Aleutian mink disease parvovirus (ADV) are two mink parvoviruses that replicate permissively in Crandell feline kidney (CRFK) cells. We have used this cell model to examine if these two mink parvoviruses use the same cellular receptor. Whereas the cellular receptor for MEV is expected to be the transferrin receptor (TfR), the cellular receptor for ADV has not been clearly identified. We used short hairpin RNAs (shRNAs) produced from plasmids to trigger RNA interference (RNAi), specifically and effectively reducing TfR expression in CRFK cells. TfR expression was reduced to levels undetectable by immunofluorescence in the majority of cells. In viral infection assays, we show that TfR expression was necessary for MEV infection but was not required for ADV infection. Thus, our results demonstrate that TfR is the cellular receptor for MEV, but not the cellular receptor for ADV. The use of two different receptors by MEV and ADV to infect the same cell line is yet another difference between these two parvoviruses that may contribute to their unique pathogenesis in mink.
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Affiliation(s)
- Gregory S Park
- Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, NIAID, NIH, Hamilton, MT 59840, USA
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517
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Nisole S, Stoye JP, Saïb A. TRIM family proteins: retroviral restriction and antiviral defence. Nat Rev Microbiol 2005; 3:799-808. [PMID: 16175175 DOI: 10.1038/nrmicro1248] [Citation(s) in RCA: 576] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Members of the tripartite motif (TRIM) protein family are involved in various cellular processes, including cell proliferation, differentiation, development, oncogenesis and apoptosis. Some TRIM proteins display antiviral properties, targeting retroviruses in particular. The potential activity of TRIM19, better known as promyelocytic leukaemia protein, against several viruses has been well documented and, recently, TRIM5alpha has been identified as the factor responsible for the previously described Lv1 and Ref1 antiretroviral activities. There is also evidence indicating that other TRIM proteins can influence viral replication. These findings are reviewed here, and the possibility that TRIMs represent a new and widespread class of antiviral proteins involved in innate immunity is also considered.
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Affiliation(s)
- Sébastien Nisole
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7151, Université Paris 7, Hôpital Saint-Louis, 1 Avenue Claude Vellefaux, 75475 Paris cedex 10, France.
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518
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519
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Abstract
Recent findings show that the Tat protein of human immunodeficiency virus (HIV) can suppress the host's RNA-silencing pathway and may thus counteract host antiviral RNAs. RNA silencing has a known role in the antiviral responses of plants and insects. Recent evidence, including the finding that the Tat protein of human immunodeficiency virus (HIV) can suppress the host's RNA-silencing pathway and may thus counteract host antiviral RNAs, suggests that RNA-silencing pathways could also have key roles in mammalian virus-host interactions.
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Affiliation(s)
- Edward P Browne
- Molecular Pathogenesis Program and Howard Hughes Medical Institute, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Junjie Li
- Molecular Pathogenesis Program and Howard Hughes Medical Institute, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Mark Chong
- Molecular Pathogenesis Program and Howard Hughes Medical Institute, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
| | - Dan R Littman
- Molecular Pathogenesis Program and Howard Hughes Medical Institute, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, New York, NY 10016, USA
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520
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Lim HS, Ko TS, Lambert KN, Kim HG, Korban SS, Hartman GL, Domier LL. Soybean mosaic virus helper component-protease enhances somatic embryo production and stabilizes transgene expression in soybean. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2005; 43:1014-21. [PMID: 16316753 DOI: 10.1016/j.plaphy.2005.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Revised: 06/10/2005] [Accepted: 08/29/2005] [Indexed: 05/05/2023]
Abstract
Soybean mosaic virus (SMV) helper component protease (HC-Pro), a suppressor of post-transcriptional gene silencing, was evaluated for its ability to enhance production of soybean hygromycin-resistant somatic embryos (HR-SEs), and stabilize transgene expression. Immature soybean cotyledonary explants were co-cultured with Agrobacterium tumefaciens strain KYRT1 harboring either pCAMBIA1302, carrying a hygromycin phosphotransferase gene (hpt) and a gene encoding green fluorescent protein; pCAMBIA1305.1, carrying hpt and beta-glucuronidase (uidA) genes; pG2-HC-Pro, a derivative of pCAMBIA1305.1 containing SMV G2 HC-Pro; or pG5-HC-Pro, a derivative of pCAMBIA1305.1 containing SMV G5 HC-Pro, but lacking uidA. Significantly (rho<0.02) higher numbers of HR-SEs were obtained from explants transformed with Agrobacterium harboring either pG2-HC-Pro or pG5-HC-Pro than with either of the vector controls (pCAMBIA1302 or pCAMBIA1305.1). Beta-glucuronidase (GUS) expression was significantly (rho<0.003) higher in 50-day-old transgenic plants expressing GUS along with SMV-HC-Pro and in SMV-infected GUS transgenic plants than in transgenic plants expressing GUS alone. Together, these data suggest that SMV-HC-Pro enhanced recovery of HR-SEs by suppressing silencing of the hygromycin phosphotransferase gene.
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Affiliation(s)
- Hyoun-Sub Lim
- Department of Crop Sciences University of Illinois, 1102 Goodwin Avenue, Urbana, IL 61801, USA
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521
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Cao X, Zhou P, Zhang X, Zhu S, Zhong X, Xiao Q, Ding B, Li Y. Identification of an RNA silencing suppressor from a plant double-stranded RNA virus. J Virol 2005; 79:13018-27. [PMID: 16189004 PMCID: PMC1235839 DOI: 10.1128/jvi.79.20.13018-13027.2005] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Accepted: 07/26/2005] [Indexed: 01/05/2023] Open
Abstract
RNA silencing is a mechanism which higher plants and animals have evolved to defend against viral infection in addition to regulation of gene expression for growth and development. As a counterdefense, many plant and some animal viruses studied to date encode RNA silencing suppressors (RSS) that interfere with various steps of the silencing pathway. In this study, we report the first identification of an RSS from a plant double-stranded RNA (dsRNA) virus. Pns10, encoded by S10 of Rice dwarf phytoreovirus (RDV), exhibited RSS activity in coinfiltration assays with the reporter green fluorescent protein (GFP) in transgenic Nicotiana benthamiana line 16c carrying GFP. The other gene segments of the RDV genome did not have such a function. Pns10 suppressed local and systemic silencing induced by sense RNA but did not interfere with local and systemic silencing induced by dsRNA. Expression of Pns10 also increased the expression of beta-glucuronidase in transient assays and enhanced Potato virus X pathogenicity in N. benthamiana. Collectively, our results establish Pns10 as an RSS encoded by a plant dsRNA virus and further suggest that Pns10 targets an upstream step of dsRNA formation in the RNA silencing pathway.
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Affiliation(s)
- Xuesong Cao
- Peking-Yale Joint Center for Plant Molecular Genetics and Agrobiotechnology, National Laboratory of Protein Engineering and Plant Genetic Engineering, College of Life Sciences, Peking University, Beijing, China
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522
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Abstract
In plants and in some animals, the effects of post-transcriptional RNA silencing can extend beyond its sites of initiation, owing to the movement of signal molecules. Although the mechanisms and channels involved are different, plant and animal silencing signals must have RNA components that account for the nucleotide sequence-specificity of their effects. Studies carried out in plants and Caenorhabditis elegans have revealed that non-cell autonomous silencing is operated through specialized, remarkably sophisticated pathways and serves important biological functions, including antiviral immunity and, perhaps, developmental patterning. Recent intriguing observations suggest that systemic RNA silencing pathways may also exist in higher vertebrates.
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Affiliation(s)
- Olivier Voinnet
- Institut de Biologie Moléculaire des Plantes du CNRS UPR-2357, 12, rue du Général Zimmer, 67084 Strasbourg Cedex, France.
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523
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Ebhardt HA, Thi EP, Wang MB, Unrau PJ. Extensive 3' modification of plant small RNAs is modulated by helper component-proteinase expression. Proc Natl Acad Sci U S A 2005; 102:13398-403. [PMID: 16157869 PMCID: PMC1224661 DOI: 10.1073/pnas.0506597102] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Indexed: 11/18/2022] Open
Abstract
RNA silencing is an evolutionarily conserved process in eukaryotes that represses gene expression by using 21- to 24-nt guide RNAs to mediate mRNA cleavage or translational inhibition. Plants have two distinct groups of silencing-associated small RNAs (smRNAs): the micro RNAs (miRNAs) and the small interfering RNAs (siRNAs). A recent report by Yu et al. [Yu, B., Yang, Z., Li, J., Minakhina, S., Yang, M., Padgett, R. W., Steward, R. & Chen, X. (2005) Science 307, 932-935] has shown that plant miRNAs are modified at their 3' termini with a methyl group. Here, we show that a large fraction of all silencing-associated smRNAs in tobacco are modified; this modification occurs on the 2' hydroxyl of the terminal ribose and significantly reduces the cloning efficiency of these modified smRNAs. Expression of the strong silencing suppressor P1/helper-component proteinase results in a marked decrease in the 3'-terminal modification of viral siRNAs but does not significantly affect the modification of endogenous miRNAs and 24-nt siRNAs. The differential modification mediated by helper-component proteinase expression implies that exogenous and endogenous smRNAs are processed through independent pathways that are isolated by subcellular compartmentalization and/or the association with distinct Dicer complexes. The degree of terminal modification may play an important role in regulating the extent to which primary smRNA signals can be amplified by RNA-dependent RNA polymerases.
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Affiliation(s)
- H Alexander Ebhardt
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
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524
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Hutvagner G. Small RNA asymmetry in RNAi: function in RISC assembly and gene regulation. FEBS Lett 2005; 579:5850-7. [PMID: 16199039 DOI: 10.1016/j.febslet.2005.08.071] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2005] [Revised: 08/31/2005] [Accepted: 08/31/2005] [Indexed: 01/24/2023]
Abstract
RNAi is a conserved gene-specific regulatory mechanism, which silences target gene expression transcriptionally and post-transcriptionally. The RNAi machinery converts the sequence specific information of a long double stranded RNAs (dsRNAs) into small 21-22 nt long dsRNAs (siRNAs, miRNAs) which assemble into an effector complex, the RNA induced silencing complex (RISC). RISC assembly is asymmetric; one strand of an siRNA or a miRNA preferentially incorporates into the RNA-protein complex. Here, I review the rules of the asymmetric RISC formation and discuss their possible regulatory function in several steps in RNAi.
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Affiliation(s)
- Gyorgy Hutvagner
- University of Dundee, School of Life Sciences, Division of Gene Regulation and Expression, Dundee DD1 4HN, UK.
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525
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Lu R, Maduro M, Li F, Li HW, Broitman-Maduro G, Li WX, Ding SW. Animal virus replication and RNAi-mediated antiviral silencing in Caenorhabditis elegans. Nature 2005; 436:1040-1043. [PMID: 16107851 PMCID: PMC1388260 DOI: 10.1038/nature03870] [Citation(s) in RCA: 316] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2005] [Accepted: 06/06/2005] [Indexed: 12/11/2022]
Abstract
The worm Caenorhabditis elegans is a model system for studying many aspects of biology, including host responses to bacterial pathogens, but it is not known to support replication of any virus. Plants and insects encode multiple Dicer enzymes that recognize distinct precursors of small RNAs and may act cooperatively. However, it is not known whether the single Dicer of worms and mammals is able to initiate the small RNA-guided RNA interference (RNAi) antiviral immunity as occurs in plants and insects. Here we show complete replication of the Flock house virus (FHV) bipartite, plus-strand RNA genome in C. elegans. We show that FHV replication in C. elegans triggers potent antiviral silencing that requires RDE-1, an Argonaute protein essential for RNAi mediated by small interfering RNAs (siRNAs) but not by microRNAs. This immunity system is capable of rapid virus clearance in the absence of FHV B2 protein, which acts as a broad-spectrum RNAi inhibitor upstream of rde-1 by targeting the siRNA precursor. This work establishes a C. elegans model for genetic studies of animal virus-host interactions and indicates that mammals might use a siRNA pathway as an antiviral response.
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Affiliation(s)
- R Lu
- Institute for Integrative Genome Biology and Department of Plant Pathology, University of California, Riverside, CA 92521
| | - M Maduro
- Department of Biology, University of California, Riverside, CA 92521
| | - F Li
- Institute for Integrative Genome Biology and Department of Plant Pathology, University of California, Riverside, CA 92521
- Graduate Program for Microbiology, University of California, Riverside, CA 92521
| | - H W Li
- Institute for Integrative Genome Biology and Department of Plant Pathology, University of California, Riverside, CA 92521
| | - G Broitman-Maduro
- Department of Biology, University of California, Riverside, CA 92521
| | - W X Li
- Institute for Integrative Genome Biology and Department of Plant Pathology, University of California, Riverside, CA 92521
| | - S W Ding
- Institute for Integrative Genome Biology and Department of Plant Pathology, University of California, Riverside, CA 92521
- Graduate Program for Microbiology, University of California, Riverside, CA 92521
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526
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Qu F, Morris TJ. Suppressors of RNA silencing encoded by plant viruses and their role in viral infections. FEBS Lett 2005; 579:5958-64. [PMID: 16162340 DOI: 10.1016/j.febslet.2005.08.041] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2005] [Revised: 08/20/2005] [Accepted: 08/21/2005] [Indexed: 10/25/2022]
Abstract
RNA silencing as a robust host defense mechanism against plant viruses is generally countered by virus-encoded silencing suppressors. This strategy is now increasingly recognized to be used by animal viruses as well. We present here an overview of the common features shared by some of the better studied plant viral silencing suppressors. We then briefly describe the characteristics of the few reported animal viral suppressors, notably their extraordinary ability of cross-kingdom suppression. We next discuss the basis for biased protection of viral RNA and subviral parasites by silencing suppressors, the link between movement and silencing suppression, the influence of temperature on the outcome of viral infection and the effect of viral silencing suppressors on the microRNA pathway.
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Affiliation(s)
- Feng Qu
- School of Biological Sciences, University of Nebraska-Lincoln, E229 Beadle Center, Lincoln, NE 68588-0666, USA
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527
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Ye K, Patel DJ. RNA silencing suppressor p21 of Beet yellows virus forms an RNA binding octameric ring structure. Structure 2005; 13:1375-84. [PMID: 16154094 PMCID: PMC4689306 DOI: 10.1016/j.str.2005.06.017] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2005] [Revised: 06/17/2005] [Accepted: 06/19/2005] [Indexed: 11/19/2022]
Abstract
Many plant viruses encode proteins that suppress the antiviral RNA silencing response mounted by the host. The suppressors p19 from tombusvirus and p21 from Beet yellows virus appear to block silencing by directly binding siRNA, a critical mediator in the process. Here, we report the crystal structure of p21, which reveals an octameric ring architecture with a large central cavity of approximately 90 A diameter. The all alpha-helical p21 monomer consists of N- and C-terminal domains that associate with their neighboring counterparts through symmetric head-to-head and tail-to-tail interactions. A putative RNA binding surface is identified in the conserved, positive-charged inner surface of the ring. In contrast to the specific p19-siRNA duplex interaction, p21 is a general nucleic acid binding protein, interacting with 21 nt or longer single- and double-stranded RNAs in vitro. This study reveals an RNA binding structure adopted by the p21 silencing suppressor.
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Affiliation(s)
| | - Dinshaw J. Patel
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York 10021
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528
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Abstract
RNA silencing or RNA interference (RNAi) refers to the small RNA-guided gene silencing mechanism conserved in a wide range of eukaryotic organisms from plants to mammals. As part of this special issue on the biology, mechanisms and applications of RNAi, here we review the recent advances on defining a role of RNAi in the responses of invertebrate and vertebrate animals to virus infection. Approximately 40 miRNAs and 10 RNAi suppressors encoded by diverse mammalian viruses have been identified. Assays used for the identification of viral suppressors and possible biological functions of both viral miRNAs and suppressors are discussed. We propose that herpes viral miRNAs may act as specificity factors to initiate heterochromatin assembly of the latent viral DNA genome in the nucleus.
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529
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Collins RE, Cheng X. Structural domains in RNAi. FEBS Lett 2005; 579:5841-9. [PMID: 16107250 PMCID: PMC2702771 DOI: 10.1016/j.febslet.2005.07.072] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 07/27/2005] [Accepted: 07/28/2005] [Indexed: 10/25/2022]
Abstract
Structural and biochemical studies have begun to elucidate the pathway of RNA silencing that leads to the formation of the RISC complex. The outstanding feature of this pathway is the precise recognition and processing of double-stranded RNA. We present a review of recent structures that illustrate the molecular mechanisms contributing to these two related functions, highlighting models of Drosha, Dicer, and RISC function.
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Affiliation(s)
- Robert E. Collins
- Department of Biochemistry, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA
- Graduate Program in Biochemistry, Cell, and Development Biology, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA
| | - Xiaodong Cheng
- Department of Biochemistry, Emory University, 1510 Clifton Road, Atlanta, GA 30322, USA
- Corresponding author. Fax: +1 404 727 3746. E-mail addresses: (R.E. Collins), (X. Cheng)
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530
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Boevink P, Oparka KJ. Virus-host interactions during movement processes. PLANT PHYSIOLOGY 2005; 138:1815-21. [PMID: 16172094 PMCID: PMC1183373 DOI: 10.1104/pp.105.066761] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Affiliation(s)
- Petra Boevink
- Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, United Kingdom
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531
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Dunoyer P, Voinnet O. The complex interplay between plant viruses and host RNA-silencing pathways. CURRENT OPINION IN PLANT BIOLOGY 2005; 8:415-23. [PMID: 15939663 DOI: 10.1016/j.pbi.2005.05.012] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2005] [Accepted: 05/19/2005] [Indexed: 05/02/2023]
Abstract
RNA silencing was originally identified as an immune system targeted against transposons and viruses, but is now also recognized as a major regulatory process that affects all layers of host gene expression through the activities of various small RNA species. Recent work in plants and animals indicates that viruses not only suppress, but can also exploit, endogenous RNA silencing pathways to redirect host gene expression. There are also indications that cellular, as opposed to virus-derived small RNAs, might well constitute an unsuspected defense layer against foreign nucleic acids. This complex interplay has implications in the context of disease resistance and evolution of viral genomes.
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Affiliation(s)
- Patrice Dunoyer
- Institut de Biologie Moléculaire des Plantes, CNRS UPR2357, Strasbourg, France
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532
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Barik S. Silence of the transcripts: RNA interference in medicine. J Mol Med (Berl) 2005; 83:764-73. [PMID: 16028076 DOI: 10.1007/s00109-005-0690-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Accepted: 05/31/2005] [Indexed: 12/11/2022]
Abstract
Silencing of gene expression by ribonucleic acid (RNA), known as RNA interference (RNAi), is now recognized as a major means of gene regulation in biology. In this mechanism, small noncoding double-stranded RNA molecules knock down gene expression through a variety of mechanisms that include messenger RNA (mRNA) degradation, inhibition of mRNA translation, or chromatin remodeling. The posttranscriptional mechanism of RNAi has been embraced by researchers as a powerful tool for generating deficient phenotypes without mutating the gene. In parallel, exciting recent results have promised its application in disease therapy. This review aims to summarize the current knowledge in this area and provide a roadmap that may eventually launch RNAi from the research bench to the medicine chest.
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Affiliation(s)
- Sailen Barik
- Department of Biochemistry and Molecular Biology, College of Medicine, MSB2370, University of South Alabama, Mobile, 36688-0002, USA.
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533
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Bennasser Y, Le SY, Benkirane M, Jeang KT. Evidence that HIV-1 encodes an siRNA and a suppressor of RNA silencing. Immunity 2005; 22:607-19. [PMID: 15894278 DOI: 10.1016/j.immuni.2005.03.010] [Citation(s) in RCA: 361] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 03/24/2005] [Accepted: 03/28/2005] [Indexed: 12/18/2022]
Abstract
In plants and invertebrate animals, RNA silencing is a form of nucleic acid-based adaptive immunity. By contrast, jawed vertebrates have evolved complex protein-based adaptive immunity. Although short interfering RNAs (siRNAs) have been used as artificial tools to silence viral infection in human cells, it remains unknown whether mammalian viruses naturally elicit such immunity in vertebral cells. Here, we report the evidence that HIV-1 encodes viral siRNA precursors in its genome and that natural HIV-1 infection provokes nucleic acid-based immunity in human cells. To combat this cellular defense, HIV-1 has evolved in its Tat protein a suppressor of RNA silencing (SRS) function. Tat abrogates the cell's RNA-silencing defense by subverting the ability of Dicer to process precursor double-stranded RNAs into siRNAs.
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Affiliation(s)
- Yamina Bennasser
- Molecular Virology Section, Laboratory of Molecular Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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534
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Flintoft L. MicroRNAs: defenders of the mammalian cell. Nat Rev Genet 2005. [DOI: 10.1038/nrg1630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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535
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Reviews and comment from the nature publishing group. Nat Rev Microbiol 2005. [DOI: 10.1038/nrmicro1145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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536
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Reviews and comment from the nature publishing group. Nat Rev Immunol 2005. [DOI: 10.1038/nri1581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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537
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Yamamoto K, Takenaka K, Matsumata T, Shimada M, Itasaka H, Shirabe K, Sugimachi K. Right hepatic lobectomy in elderly patients with hepatocellular carcinoma. ACTA ACUST UNITED AC 1997. [PMID: 9164528 DOI: 10.4236/ojim.2012.23024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
BACKGROUND/AIMS The outcome of hepatectomy in elderly patients with hepatocellular carcinoma have been reported, however neither the morphological nor functional hepatic regeneration in elderly patients have been fully investigated. MATERIALS AND METHODS Fifty-six patients with hepatocellular carcinoma, who underwent a right hepatic lobectomy over an 8-year period, were classified into three groups according to their age; group 1 (n = 7), more than 70 years of age; group 2 (n = 40), patients from 50 to 69 years of age and group 3 (n = 9), under 50 years of age. There were no significant differences regarding backgrounds or intra-operative parameters among the three groups. The perioperative hepatic function, postoperative complications and the regeneration rate of the remnant left lobe at 1 month after operation were compared. RESULTS No differences were found in the regeneration rate, however, the levels of the hepaplastin test and lecithin:cholesterol acyltransferase at 7 days after hepatectomy in group 1 (31.3%, 8.8 U) were significantly lower than those in groups 2 and 3 (37.4%, 18.4 U; 47.9%, 29.4 U, respectively). The incidence of hospital death due to hepatic failure in group 1 (42.9%) was also significantly higher than that of group 2 (5.0%) or group 3 (0%). CONCLUSION The decline of postoperative protein synthesis regardless of the voluminal regeneration is a characteristic of the elderly. This phenomenon might thus be an important promoter of postoperative hepatic failure which remains unpredictable using any type of examination. Therefore, at this time, a major hepatectomy is not recommended as a viable treatment alternative in the elderly.
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Affiliation(s)
- K Yamamoto
- Department of Surgery II, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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