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Warsaba R, Salcedo-Porras N, Flibotte S, Jan E. Expansion of viral genomes with viral protein genome linked copies. Virology 2022; 577:174-184. [PMID: 36395539 DOI: 10.1016/j.virol.2022.10.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 10/24/2022] [Accepted: 10/26/2022] [Indexed: 11/13/2022]
Abstract
Virus protein-linked genome (VPg) proteins are required for replication. VPgs are duplicated in a subset of RNA viruses however their roles are not fully understood and the extent of viral genomes containing VPg copies has not been investigated in detail. Here, we generated a novel bioinformatics approach to identify VPg sequences in viral genomes using hidden Markov models (HMM) based on alignments of dicistrovirus VPg sequences. From metagenomic datasets of dicistrovirus genomes, we identified 717 dicistrovirus genomes containing VPgs ranging from a single copy to 8 tandem copies. The VPgs are classified into nine distinct types based on their sequence and length. The VPg types but not VPg numbers per viral genome followed specific virus clades, thus suggesting VPgs co-evolved with viral genomes. We also identified VPg duplications in aquamavirus and mosavirus genomes. This study greatly expands the number of viral genomes that contain VPg copies and indicates that duplicated viral sequences are more widespread than anticipated.
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Affiliation(s)
- Reid Warsaba
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada; Life Sciences Institute, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Nicolas Salcedo-Porras
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada; Life Sciences Institute, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Stephane Flibotte
- Life Sciences Institute, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada; UBC/LSI Bioinformatics Facility, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | - Eric Jan
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada; Life Sciences Institute, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
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Multiple Viral Protein Genome-Linked Proteins Compensate for Viral Translation in a Positive-Sense Single-Stranded RNA Virus Infection. J Virol 2022; 96:e0069922. [PMID: 35993738 PMCID: PMC9472611 DOI: 10.1128/jvi.00699-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Viral protein genome-linked (VPg) protein plays an essential role in protein-primed replication of plus-stranded RNA viruses. VPg is covalently linked to the 5' end of the viral RNA genome via a phosphodiester bond typically at a conserved amino acid. Whereas most viruses have a single VPg, some viruses have multiple VPgs that are proposed to have redundant yet undefined roles in viral replication. Here, we use cricket paralysis virus (CrPV), a dicistrovirus that has four nonidentical copies of VPg, as a model to characterize the role of VPg copies in infection. Dicistroviruses contain two main open reading frames (ORFs) that are driven by distinct internal ribosome entry sites (IRESs). We systematically generated single and combinatorial deletions and mutations of VPg1 to VPg4 within the CrPV infectious clone and monitored viral yield in Drosophila S2 cells. Deletion of one to three VPg copies progressively decreased viral yield and delayed viral replication, suggesting a threshold number of VPgs for productive infection. Mass spectrometry analysis of CrPV VPg-linked RNAs revealed viral RNA linkage to either a serine or threonine in VPg, mutations of which in all VPgs attenuated infection. Mutating serine 4 in a single VPg abolished viral infection, indicating a dominant negative effect. Using viral minigenome reporters that monitor dicistrovirus 5' untranslated (UTR) and IRES translation revealed a relationship between VPg copy number and the ratio of distinct IRES translation activities. We uncovered a novel viral strategy whereby VPg copies in dicistrovirus genomes compensate for the relative IRES translation efficiencies to promote infection. IMPORTANCE Genetic duplication is exceedingly rare in small RNA viral genomes, as there is selective pressure to prevent RNA genomes from expanding. However, some small RNA viruses encode multiple copies of a viral protein, most notably an unusual viral protein that is linked to the viral RNA genome. Here, we investigate a family of viruses that contains multiple viral protein genome-linked proteins and reveal a novel viral strategy whereby viral protein copy number counterbalances differences in viral protein synthesis mechanisms.
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3
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The hinge region of the Israeli acute paralysis virus internal ribosome entry site directs ribosomal positioning, translational activity and virus infection. J Virol 2022; 96:e0133021. [PMID: 35019716 DOI: 10.1128/jvi.01330-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
All viruses must usurp host ribosomes for viral protein synthesis. Dicistroviruses utilize an InterGenic Region Internal Ribosome Entry Site (IGR IRES) to directly recruit ribosomes and mediate translation initiation from a non-AUG start codon. The IGR IRES adopts a three-pseudoknot structure that is comprised of a ribosome binding domain of pseudoknot II and III (PKII and PKIII), and a tRNA-like anticodon domain (PKI) connected via a short, one to three nucleotide hinge region. Recent cryo-EM structural analysis of the dicistrovirus Taura syndrome virus (TSV) IGR IRES bound to the ribosome suggests that the hinge region may facilitate translocation of the IRES from the ribosomal A to P site. In this study, we provide mechanistic and functional insights into the role of the hinge region in IGR IRES translation. Using the honeybee dicistrovirus, Israeli acute paralysis virus (IAPV), as a model, we demonstrate that mutations of the hinge region resulted in decreased IRES-dependent translation in vitro. Toeprinting primer extension analysis of mutant IRESs bound to purified ribosomes and in rabbit reticulocyte lysates showed defects in the initial ribosome positioning on the IRES. Finally, using a hybrid dicistrovirus clone, mutations in the hinge region of the IAPV IRES resulted in decreased viral yield. Our work reveals an unexpected role of the hinge region of the dicistrovirus IGR IRES coordinating the two independently folded domains of the IRES to properly position the ribosome to start translation. IMPORTANCE Viruses must use the host cell machinery to direct viral protein expression for productive infection. One such mechanism is an internal ribosome entry site which can directly recruit host cell machinery. In this study, we have identified a novel sequence in an IRES that provides insight into the mechanism of viral gene expression. Specifically, this novel sequence promotes viral IRES activity by directly guiding the host cell machinery to start gene expression at a specific site.
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Wu X, He WT, Tian S, Meng D, Li Y, Chen W, Li L, Tian L, Zhong CQ, Han F, Chen J, Han J. pelo is required for high efficiency viral replication. PLoS Pathog 2014; 10:e1004034. [PMID: 24722736 PMCID: PMC3983054 DOI: 10.1371/journal.ppat.1004034] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 02/14/2014] [Indexed: 11/18/2022] Open
Abstract
Viruses hijack host factors for their high speed protein synthesis, but information about these factors is largely unknown. In searching for genes that are involved in viral replication, we carried out a forward genetic screen for Drosophila mutants that are more resistant or sensitive to Drosophila C virus (DCV) infection-caused death, and found a virus-resistant line in which the expression of pelo gene was deficient. Our mechanistic studies excluded the viral resistance of pelo deficient flies resulting from the known Drosophila anti-viral pathways, and revealed that pelo deficiency limits the high level synthesis of the DCV capsid proteins but has no or very little effect on the expression of some other viral proteins, bulk cellular proteins, and transfected exogenous genes. The restriction of replication of other types of viruses in pelo deficient flies was also observed, suggesting pelo is required for high level production of capsids of all kinds of viruses. We show that both pelo deficiency and high level DCV protein synthesis increase aberrant 80S ribosomes, and propose that the preferential requirement of pelo for high level synthesis of viral capsids is at least partly due to the role of pelo in dissociation of stalled 80S ribosomes and clearance of aberrant viral RNA and proteins. Our data demonstrated that pelo is a host factor that is required for high efficiency translation of viral capsids and targeting pelo could be a strategy for general inhibition of viral infection.
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Affiliation(s)
- Xiurong Wu
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Wan-Ting He
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Shuye Tian
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Dan Meng
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Yuanyue Li
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Wanze Chen
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Lisheng Li
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Lili Tian
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Chuan-Qi Zhong
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Felicia Han
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
| | - Jianming Chen
- The Key Laboratory of Marine Biogenetic Resources, The Third Institute of Oceanography, State Oceanic Administration of China, Xiamen, Fujian, China
| | - Jiahuai Han
- State Key Laboratory of Cellular Stress Biology, Innovation Center for Cell Biology, School of Life Sciences, Xiamen University, Xiamen, Fujian, China
- * E-mail: ,
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Xu J, Cherry S. Viruses and antiviral immunity in Drosophila. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2014; 42:67-84. [PMID: 23680639 PMCID: PMC3826445 DOI: 10.1016/j.dci.2013.05.002] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/26/2013] [Accepted: 05/02/2013] [Indexed: 05/10/2023]
Abstract
Viral pathogens present many challenges to organisms, driving the evolution of a myriad of antiviral strategies to combat infections. A wide variety of viruses infect invertebrates, including both natural pathogens that are insect-restricted, and viruses that are transmitted to vertebrates. Studies using the powerful tools in the model organism Drosophila have expanded our understanding of antiviral defenses against diverse viruses. In this review, we will cover three major areas. First, we will describe the tools used to study viruses in Drosophila. Second, we will survey the major viruses that have been studied in Drosophila. And lastly, we will discuss the well-characterized mechanisms that are active against these diverse pathogens, focusing on non-RNAi mediated antiviral mechanisms. Antiviral RNAi is discussed in another paper in this issue.
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Affiliation(s)
- Jie Xu
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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Jurgeit A, Moese S, Roulin P, Dorsch A, Lötzerich M, Lee WM, Greber UF. An RNA replication-center assay for high content image-based quantifications of human rhinovirus and coxsackievirus infections. Virol J 2010; 7:264. [PMID: 20937137 PMCID: PMC2958916 DOI: 10.1186/1743-422x-7-264] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 10/11/2010] [Indexed: 01/17/2023] Open
Abstract
Background Picornaviruses are common human and animal pathogens, including polio and rhinoviruses of the enterovirus family, and hepatits A or food-and-mouth disease viruses. There are no effective countermeasures against the vast majority of picornaviruses, with the exception of polio and hepatitis A vaccines. Human rhinoviruses (HRV) are the most prevalent picornaviruses comprising more than one hundred serotypes. The existing and also emerging HRVs pose severe health risks for patients with asthma or chronic obstructive pulmonary disease. Here, we developed a serotype-independent infection assay using a commercially available mouse monoclonal antibody (mabJ2) detecting double-strand RNA. Results Immunocytochemical staining for RNA replication centers using mabJ2 identified cells that were infected with either HRV1A, 2, 14, 16, 37 or coxsackievirus (CV) B3, B4 or A21. MabJ2 labeled-cells were immunocytochemically positive for newly synthesized viral capsid proteins from HRV1A, 14, 16, 37 or CVB3, 4. We optimized the procedure for detection of virus replication in settings for high content screening with automated fluorescence microscopy and single cell analysis. Our data show that the infection signal was dependent on multiplicity, time and temperature of infection, and the mabJ2-positive cell numbers correlated with viral titres determined in single step growth curves. The mabJ2 infection assay was adapted to determine the efficacy of anti-viral compounds and small interfering RNAs (siRNAs) blocking enterovirus infections. Conclusions We report a broadly applicable, rapid protocol to measure infection of cultured cells with enteroviruses at single cell resolution. This assay can be applied to a wide range of plus-sense RNA viruses, and hence allows comparative studies of viral infection biology without dedicated reagents or procedures. This protocol also allows to directly compare results from small compound or siRNA infection screens for different serotypes without the risk of assay specific artifacts.
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Affiliation(s)
- Andreas Jurgeit
- Institute of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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7
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Balvay L, Soto Rifo R, Ricci EP, Decimo D, Ohlmann T. Structural and functional diversity of viral IRESes. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2009; 1789:542-57. [PMID: 19632368 DOI: 10.1016/j.bbagrm.2009.07.005] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 07/17/2009] [Accepted: 07/19/2009] [Indexed: 01/06/2023]
Abstract
Some 20 years ago, the study of picornaviral RNA translation led to the characterization of an alternative mechanism of initiation by direct ribosome binding to the 5' UTR. By using a bicistronic vector, it was shown that the 5' UTR of the poliovirus (PV) or the Encephalomyelitis virus (EMCV) had the ability to bind the 43S preinitiation complex in a 5' and cap-independent manner. This is rendered possible by an RNA domain called IRES for Internal Ribosome Entry Site which enables efficient translation of an mRNA lacking a 5' cap structure. IRES elements have now been found in many different viral families where they often confer a selective advantage to allow ribosome recruitment under conditions where cap-dependent protein synthesis is severely repressed. In this review, we compare and contrast the structure and function of IRESes that are found within 4 distinct family of RNA positive stranded viruses which are the (i) Picornaviruses; (ii) Flaviviruses; (iii) Dicistroviruses; and (iv) Lentiviruses.
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Affiliation(s)
- Laurent Balvay
- Unité de Virologie Humaine, Ecole Normale Supérieure de Lyon, Lyon F-693643, France
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8
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Abstract
The fruit fly Drosophila melanogaster is a powerful model to study host-pathogen interactions. Most studies so far have focused on extracellular pathogens such as bacteria and fungi. More recently, viruses have come to the front, and RNA interference was shown to play a critical role in the control of viral infections in drosophila. We review here our current knowledge on drosophila viruses. A diverse set of RNA viruses belonging to several families (Rhabdoviridae, Dicistroviridae, Birnaviridae, Reoviridae, Errantiviridae) has been reported in D. melanogaster. By contrast, no DNA virus has been recovered up to now. The drosophila viruses represent powerful tools to study virus-cell interactions in vivo. Analysis of the literature however reveals that for many of them, important gaps exist in our understanding of their replication cycle, genome organization, morphology or pathogenesis. The data obtained in the past few years on antiviral defense mechanisms in drosophila, which point to evolutionary conserved pathways, highlight the potential of the D. melanogaster model to study antiviral innate immunity and to better understand the complex interaction between arthropod-borne viruses and their insect vectors.
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Nakashima N, Uchiumi T. Functional analysis of structural motifs in dicistroviruses. Virus Res 2008; 139:137-47. [PMID: 18621089 DOI: 10.1016/j.virusres.2008.06.006] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Accepted: 06/11/2008] [Indexed: 10/21/2022]
Abstract
The family Dicistroviridae is composed of positive-stranded RNA viruses which have monopartite genomes. These viruses carry genome-linked virus proteins (VPg) and poly (A) tails. The 5' untranslated region (UTR) is approximately 500 nucleotides and contains an internal ribosome entry site (IRES). These features resemble those of vertebrate picornaviruses, but dicistroviruses have other distinct characteristics. Picornaviruses have a single large open reading frame (ORF) encoding the capsid proteins at the 5'-end and the replicases at the 3'-end. In contrast, dicistroviruses have two nonoverlapping ORFs. The 5'-proximal ORF encodes the replicases and the 3'-proximal ORF encodes the capsid proteins. Usually, positive-stranded viruses which have capsid protein genes in the 3' part of the genome produce subgenomic RNA for synthesis of the capsid proteins, because abundant quantities of the capsid proteins are required for the viral replication cycle. In dicistroviruses, translation of the capsid proteins is controlled by an additional IRES. This IRES is located in the intergenic region (IGR) between the replicase and capsid coding regions, and mediates the initiation of translation for the capsid proteins. The IGR-IRES has a multiple stem-loop structure containing three pseudoknots. We describe the characteristics of dicistroviruses, including the RNA elements and viral proteins.
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Affiliation(s)
- Nobuhiko Nakashima
- National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
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Cherry S, Kunte A, Wang H, Coyne C, Rawson RB, Perrimon N. COPI activity coupled with fatty acid biosynthesis is required for viral replication. PLoS Pathog 2006; 2:e102. [PMID: 17040126 PMCID: PMC1599761 DOI: 10.1371/journal.ppat.0020102] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Accepted: 08/25/2006] [Indexed: 11/26/2022] Open
Abstract
During infection by diverse viral families, RNA replication occurs on the surface of virally induced cytoplasmic membranes of cellular origin. How this process is regulated, and which cellular factors are required, has been unclear. Moreover, the host–pathogen interactions that facilitate the formation of this new compartment might represent critical determinants of viral pathogenesis, and their elucidation may lead to novel insights into the coordination of vesicular trafficking events during infection. Here we show that in Drosophila cells, Drosophila C virus remodels the Golgi apparatus and forms a novel vesicular compartment, on the surface of which viral RNA replication takes place. Using genome-wide RNA interference screening, we found that this step in the viral lifecycle requires at least two host encoded pathways: the coat protein complex I (COPI) coatamer and fatty acid biosynthesis. Our results integrate, clarify, and extend numerous observations concerning the cell biology of viral replication, allowing us to conclude that the coupling of new cellular membrane formation with the budding of these vesicles from the Golgi apparatus allows for the regulated generation of this new virogenic organelle, which is essential for viral replication. Additionally, because these pathways are also limiting in flies and in human cells infected with the related RNA virus poliovirus, they may represent novel targets for antiviral therapies. In order to successfully invade and replicate within their hosts, viruses hijack cellular factors. In the case of many RNA viruses, including a Drosophila picorna-like virus Drosophila C virus, they must undergo the essential step of genomic replication on the surface of cytoplasmic membranes. Specifically, for picornaviruses, these vesicles are induced in the infected cell, and the ontogeny and cellular factors required to form this compartment have been unclear. Circumstantial evidence has implicated coat protein complex I (COPI), COPII, and autophagy. Here, Cherry and colleagues present their findings using a genome-wide RNA interference screening approach using a picorna-like virus that COPI and fatty acid biosynthesis are critical host pathways required to generate this intracellular vesicular compartment. Furthermore, they show that loss of COPI, but not COPII, is protective both in adult flies and in human cells infected with the related picornavirus, poliovirus. These novel and exciting findings have broad-scale implications for picornavirus replication and for the potential use of these pathways as novel antiviral targets.
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Affiliation(s)
- Sara Cherry
- University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America.
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Nakashima N, Shibuya N. Multiple coding sequences for the genome-linked virus protein (VPg) in dicistroviruses. J Invertebr Pathol 2006; 92:100-4. [PMID: 16707137 DOI: 10.1016/j.jip.2006.03.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2005] [Revised: 03/15/2006] [Accepted: 03/29/2006] [Indexed: 11/23/2022]
Abstract
N-terminal Edman sequencing of the genome-linked viral protein (VPg) of Plautia stali intestine virus (PSIV, Dicistroviridae) detected heterologus residues. The VPg sequence determined was found to be triplicated in the nonstructural protein precursor. Multiple VPg-like sequences were also found in 10 of the 12 dicistroviruses with a maximum of six copies in Solenopsis invicta virus-1. We postulate that redundant VPg coding sequences facilitate multiplication of dicistroviruses, because fewer cycle of translation of the nonstructural protein precursor produces larger amounts of VPg proteins in parallel with the increased production of capsid proteins by the intergenic internal ribosome entry site mediated translation.
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Affiliation(s)
- Nobuhiko Nakashima
- National Institute of Agrobiological Sciences, Owashi, Tsukuba, Ibaraki 305-8634, Japan.
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12
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Jan E. Divergent IRES elements in invertebrates. Virus Res 2005; 119:16-28. [PMID: 16307820 DOI: 10.1016/j.virusres.2005.10.011] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2005] [Revised: 09/05/2005] [Accepted: 10/20/2005] [Indexed: 02/05/2023]
Abstract
Viruses have evolved unique strategies and mechanisms to recruit ribosomes to ensure continued translation of their viral RNA during infection. The Dicistroviridae family of invertebrate viruses contains an unusual internal ribosome entry site (IRES), which can directly recruit ribosomes in the absence of initiation factors. Moreover, this IRES initiates translation at a non-AUG codon independent of an initiator Met-tRNA. Recent studies have shown that the IRES mimicks a tRNA to interact with and manipulate the ribosome. The presence of this divergent IRES likely allows translation of the dicistroviral RNA during infection when host translation is compromised. This review will explore the unique properties of this unprecedented mechanism of gene expression. Specific topics will examine structural components of the IRES, the mechanism of initiating translation at non-AUG codons and the regulation of this IRES in vivo. The existence of this mechanism suggests that the repertoire of open reading frames in our genome may be greater than anticipated.
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Affiliation(s)
- Eric Jan
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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13
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Cherry S, Doukas T, Armknecht S, Whelan S, Wang H, Sarnow P, Perrimon N. Genome-wide RNAi screen reveals a specific sensitivity of IRES-containing RNA viruses to host translation inhibition. Genes Dev 2005; 19:445-52. [PMID: 15713840 PMCID: PMC548945 DOI: 10.1101/gad.1267905] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The widespread class of RNA viruses that utilize internal ribosome entry sites (IRESs) for translation include poliovirus and Hepatitis C virus. To identify host factors required for IRES-dependent translation and viral replication, we performed a genome-wide RNAi screen in Drosophila cells infected with Drosophila C virus (DCV). We identified 66 ribosomal proteins that, when depleted, specifically inhibit DCV growth, but not a non-IRES-containing RNA virus. Moreover, treatment of flies with a translation inhibitor is protective in vivo. Finally, this increased sensitivity to ribosome levels also holds true for poliovirus infection of human cells, demonstrating the generality of these findings.
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Affiliation(s)
- Sara Cherry
- Department of Genetics, Harvard Medical School and Howard Hughes Medical Instutite, Boston, Massachusetts 02115, USA.
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14
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Ongus JR, Peters D, Bonmatin JM, Bengsch E, Vlak JM, van Oers MM. Complete sequence of a picorna-like virus of the genus Iflavirus replicating in the mite Varroa destructor. J Gen Virol 2004; 85:3747-3755. [PMID: 15557248 DOI: 10.1099/vir.0.80470-0] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aggregations of 27 nm virus-like particles were observed in electron microscopy images of sectioned Varroa destructor mite tissue. The scattered occurrence of individual particles and accumulation of the virions in lattices in the cytoplasm gave an apparent indication that the virus replicates in the mite. Sequence analysis of the RNA of the purified virus revealed a genome organization with high similarity to that of members of the genus Iflavirus. Phylogenetic analysis of the polymerase showed that the virus was related most closely to Deformed wing virus (DWV) and Kakugo virus (KV) of bees. The virus has a genome of 10 112 nt without the poly(A) tail, with an overall RNA genome identity of 84 % to those of DWV and KV and has one large ORF, translated into a 2893 aa polyprotein with an amino acid identity of 95 % to those of DWV and KV. The first 1455 nt of the ORF encoding the lower molecular mass structural proteins shows the greatest diversion from those of DWV and KV, with an RNA identity of 79 %, and translates to a polypeptide of 485 aa with an identity of 90 %. The name proposed for this virus is Varroa destructor virus 1 (VDV-1). To determine whether VDV-1 replicates in mites, a selective RT-PCR was done to detect the presence of the negative-sense RNA strand. The virus isolate and the closely related DWV could be discriminated by two primer sets, each specific to one virus. Both viruses replicated in the population of the mite species studied.
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Affiliation(s)
- Juliette R Ongus
- Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands
| | - Dick Peters
- Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands
| | | | - Eberhard Bengsch
- GSF-Institute for Ecological Chemistry, D-85764 Oberschleissheim, Germany
- Centre de Biophysique Moléculaire, CNRS, Orléans, France
| | - Just M Vlak
- Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands
| | - Monique M van Oers
- Laboratory of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands
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15
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Wilson JE, Powell MJ, Hoover SE, Sarnow P. Naturally occurring dicistronic cricket paralysis virus RNA is regulated by two internal ribosome entry sites. Mol Cell Biol 2000; 20:4990-9. [PMID: 10866656 PMCID: PMC85949 DOI: 10.1128/mcb.20.14.4990-4999.2000] [Citation(s) in RCA: 259] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cricket paralysis virus is a member of a group of insect picorna-like viruses. Cloning and sequencing of the single plus-strand RNA genome revealed the presence of two nonoverlapping open reading frames, ORF1 and ORF2, that encode the nonstructural and structural proteins, respectively. We show that each ORF is preceded by one internal ribosome entry site (IRES). The intergenic IRES is located 6,024 nucleotides from the 5' end of the viral RNA and is more active than the IRES located at the 5' end of the RNA, providing a mechanistic explanation for the increased abundance of structural proteins relative to nonstructural proteins in infected cells. Mutational analysis of this intergenic-region IRES revealed that ORF2 begins with a noncognate CCU triplet. Complementarity of this CCU triplet with sequences in the IRES is important for IRES function, pointing to an involvement of RNA-RNA interactions in translation initiation. Thus, the cricket paralysis virus genome is an example of a naturally occurring, functionally dicistronic eukaryotic mRNA whose translation is controlled by two IRES elements located at the 5' end and in the middle of the mRNA. This finding argues that eukaryotic mRNAs can express multiple proteins not only by polyprotein processing, reinitiation and frameshifting but also by using multiple IRES elements.
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Affiliation(s)
- J E Wilson
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305, USA
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