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Li Y, Zhang L, Wang L, Li J, Zhao Y, Liu F, Wang Q. Structure and function of type IV IRES in picornaviruses: a systematic review. Front Microbiol 2024; 15:1415698. [PMID: 38855772 PMCID: PMC11157119 DOI: 10.3389/fmicb.2024.1415698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Accepted: 05/13/2024] [Indexed: 06/11/2024] Open
Abstract
The Picornaviridae is a family of icosahedral viruses with single-stranded, highly diverse positive-sense RNA genomes. Virions consist of a capsid, without envelope, surrounding a core of RNA genome. A typical genome of picornavirus harbors a well-conserved and highly structured RNA element known as the internal ribosome entry site (IRES), functionally essential for viral replication and protein translation. Based on differences in their structures and mechanisms of action, picornaviral IRESs have been categorized into five types: type I, II, III, IV, and V. Compared with the type IV IRES, the others not only are structurally complicated, but also involve multiple initiation factors for triggering protein translation. The type IV IRES, often referred to as hepatitis C virus (HCV)-like IRES due to its structural resemblance to the HCV IRES, exhibits a simpler and more compact structure than those of the other four. The increasing identification of picornaviruses with the type IV IRES suggests that this IRES type seems to reveal strong retention and adaptation in terms of viral evolution. Here, we systematically reviewed structural features and biological functions of the type IV IRES in picornaviruses. A comprehensive understanding of the roles of type IV IRESs will contribute to elucidating the replication mechanism and pathogenesis of picornaviruses.
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Affiliation(s)
- Yan Li
- College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
- Qingdao Center for Animal Disease Control and Prevention, Qingdao, China
| | - Lei Zhang
- Shandong New Hope Liuhe Group Co., Ltd., Qingdao, China
| | - Ling Wang
- University Hospital, Qingdao Agricultural University, Qingdao, China
| | - Jing Li
- Market Supervision Administration of Huangdao District, Qingdao, China
| | - Yanwei Zhao
- College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
| | - Fuxiao Liu
- College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
| | - Qianqian Wang
- College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China
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Impacts of single nucleotide deletions from the 3' end of Senecavirus A 5' untranslated region on activity of viral IRES and on rescue of recombinant virus. Virology 2021; 563:126-133. [PMID: 34530232 DOI: 10.1016/j.virol.2021.09.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/22/2021] [Accepted: 09/05/2021] [Indexed: 02/07/2023]
Abstract
The 5' untranslated region (UTR) of Senecavirus A (SVA) harbors an internal ribosome entry site (IRES), in which a pseudoknot structure is upstream of start codon AUG. Wild-type SVAs have a highly conserved 13-nt-sequence between the pseudoknot stem II (PKS-II)-forming motif and the AUG. In this study, a single nucleotide was deleted one by one from the 13-nt-sequence within a wild-type SVA minigenome. The result showed that neither mono- nor multi-nucleotide deletions abolished the IRES activity. Furthermore, a single nucleotide was deleted one by one from the 13-nt-sequence within a full-length SVA cDNA clone. The result indicated that nucleotide-deleting SVAs could be rescued from 1- to 5-nt-deleting cDNA clones, whereas only the 1- and 2-nt-deleting viruses were genetically stable during nine serial passages in vitro. Additionally, only the 1-nt-deleting SVA showed similar growth kinetics to that of the wild-type virus, suggesting that the pseudoknot-AUG distance was crucial for SVA replication.
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Romero-López C, Berzal-Herranz A. The Role of the RNA-RNA Interactome in the Hepatitis C Virus Life Cycle. Int J Mol Sci 2020; 21:ijms21041479. [PMID: 32098260 PMCID: PMC7073135 DOI: 10.3390/ijms21041479] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/18/2020] [Accepted: 02/19/2020] [Indexed: 02/05/2023] Open
Abstract
RNA virus genomes are multifunctional entities endowed with conserved structural elements that control translation, replication and encapsidation, among other processes. The preservation of these structural RNA elements constraints the genomic sequence variability. The hepatitis C virus (HCV) genome is a positive, single-stranded RNA molecule with numerous conserved structural elements that manage different steps during the infection cycle. Their function is ensured by the association of protein factors, but also by the establishment of complex, active, long-range RNA-RNA interaction networks-the so-called HCV RNA interactome. This review describes the RNA genome functions mediated via RNA-RNA contacts, and revisits some canonical ideas regarding the role of functional high-order structures during the HCV infective cycle. By outlining the roles of long-range RNA-RNA interactions from translation to virion budding, and the functional domains involved, this work provides an overview of the HCV genome as a dynamic device that manages the course of viral infection.
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Karagyaur M, Rostovtseva A, Semina E, Klimovich P, Balabanyan V, Makarevich P, Popov V, Stambolsky D, Tkachuk V. A Bicistronic Plasmid Encoding Brain-Derived Neurotrophic Factor and Urokinase Plasminogen Activator Stimulates Peripheral Nerve Regeneration After Injury. J Pharmacol Exp Ther 2019; 372:248-255. [DOI: 10.1124/jpet.119.261594] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 12/17/2019] [Indexed: 12/14/2022] Open
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Lattimer J, Stewart H, Locker N, Tuplin A, Stonehouse NJ, Harris M. Structure-function analysis of the equine hepacivirus 5' untranslated region highlights the conservation of translational mechanisms across the hepaciviruses. J Gen Virol 2019; 100:1501-1514. [PMID: 31490115 PMCID: PMC7615701 DOI: 10.1099/jgv.0.001316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Equine hepacivirus (EHcV) (now also classified as hepacivirus A) is the closest genetic relative to hepatitis C virus (HCV) and is proposed to have diverged from HCV within the last 1000 years. The 5' untranslated regions (UTRs) of both HCV and EHcV exhibit internal ribosome entry site (IRES) activity, allowing cap-independent translational initiation, yet only the HCV 5'UTR has been systematically analysed. Here, we report a detailed structural and functional analysis of the EHcV 5'UTR. The secondary structure was determined using selective 2' hydroxyl acylation analysed by primer extension (SHAPE), revealing four stem-loops, termed SLI, SLIA, SLII and SLIII, by analogy to HCV. This guided a mutational analysis of the EHcV 5'UTR, allowing us to investigate the roles of the stem-loops in IRES function. This approach revealed that SLI was not required for EHcV IRES-mediated translation. Conversely, SLIII was essential, specifically SLIIIb, SLIIId and a GGG motif that is conserved across the Hepaciviridae. Further SHAPE analysis provided evidence that this GGG motif mediated interaction with the 40S ribosomal subunit, whilst a CUU sequence in the apical loop of SLIIIb mediated an interaction with eIF3. In addition, we showed that a microRNA122 target sequence located between SLIA and SLII mediated an enhancement of translation in the context of a subgenomic replicon. Taken together, these results highlight the conservation of hepaciviral translation mechanisms, despite divergent primary sequences.
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Affiliation(s)
- Joseph Lattimer
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Hazel Stewart
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Nicolas Locker
- Faculty of Health and Medical Sciences, School of Biosciences and Medicine, University of Surrey, Guildford, GU2 7XH, UK
| | - Andrew Tuplin
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Nicola J. Stonehouse
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Mark Harris
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
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Mercuri L, Thomson EC, Hughes J, Karayiannis P. Quasispecies Changes with Distinctive Point Mutations in the Hepatitis C Virus Internal Ribosome Entry Site (IRES) Derived from PBMCs and Plasma. Adv Virol 2018; 2018:4835252. [PMID: 30581467 PMCID: PMC6276526 DOI: 10.1155/2018/4835252] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 11/11/2018] [Indexed: 12/12/2022] Open
Abstract
The 5' untranslated region (UTR) of the hepatitis C virus (HCV) genome contains the internal ribosome entry site (IRES), a highly conserved RNA structure essential for cap-independent translation of the viral polyprotein. HCV, apart from the liver, is thought to be associated with lymphocyte subpopulations of peripheral blood mononuclear cells (PBMCs), in lymph nodes and brain tissue. In this study, RT-PCR, cloning, and sequence analysis were employed to investigate the quasispecies nature of the 5'UTR following extraction of viral RNA from PBMCs and plasma of HCV infected individuals. The nucleotide variation between IRES-derived sequences from PBMCs and plasma indicated the existence of polymorphic sites within the IRES. HCV isolates had divergent variants with unique mutations particularly at positions 107, 204, and 243 of the IRES. Most of the PBMC-derived sequences contained an A-A-A variant at these positions. The mutations associated with the IRESes suggested the presence of unique quasispecies populations in PBMCs compared with plasma.
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Affiliation(s)
- Luca Mercuri
- Hepatology Section, Division of Medicine, Faculty of Medicine, Imperial College, London, UK
| | - Emma C. Thomson
- University of Glasgow MRC Centre for Virus Research, Glasgow, UK
| | - Joseph Hughes
- University of Glasgow MRC Centre for Virus Research, Glasgow, UK
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Mutational Analysis of the Bovine Hepacivirus Internal Ribosome Entry Site. J Virol 2018; 92:JVI.01974-17. [PMID: 29769341 DOI: 10.1128/jvi.01974-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Accepted: 05/11/2018] [Indexed: 12/19/2022] Open
Abstract
In recent years, hepatitis C virus (HCV)-related viruses were identified in several species, including dogs, horses, bats, and rodents. In addition, a novel virus of the genus Hepacivirus has been discovered in bovine samples and was termed bovine hepacivirus (BovHepV). Prediction of the BovHepV internal ribosome entry site (IRES) structure revealed strong similarities to the HCV IRES structure comprising domains II, IIIabcde, pseudoknot IIIf, and IV with the initiation codon AUG. Unlike HCV, only one microRNA-122 (miR-122) binding site could be identified in the BovHepV 5' nontranslated region. In this study, we analyzed the necessity of BovHepV IRES domains to initiate translation and investigated possible interactions between the IRES and core coding sequences by using a dual luciferase reporter assay. Our results suggest that such long-range interactions within the viral genome can affect IRES-driven translation. Moreover, the significance of a possible miR-122 binding to the BovHepV IRES was investigated. When analyzing translation in human Huh-7 cells with large amounts of endogenous miR-122, introduction of point mutations to the miR-122 binding site resulted in reduced translation efficiency. Similar results were observed in HeLa cells after substitution of miR-122. Nevertheless, the absence of pronounced effects in a bovine hepatocyte cell line expressing hardly any miR-122 as well suggests additional functions of this host factor in virus replication.IMPORTANCE Several members of the family Flaviviridae, including HCV, have adapted cap-independent translation strategies to overcome canonical eukaryotic translation pathways and use cis-acting RNA-elements, designated viral internal ribosome entry sites (IRES), to initiate translation. Although novel hepaciviruses have been identified in different animal species, only limited information is available on their biology on molecular level. Therefore, our aim was a fundamental analysis of BovHepV IRES functions. The findings which show that functional IRES elements are also crucial for BovHepV translation expand our knowledge on molecular mechanism of hepacivirus propagation. We also studied the possible effects of one major host factor implicated in HCV pathogenesis, miR-122. The results of mutational analyses suggested that miR-122 enhances virus translation mediated by BovHepV IRES.
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Romero-López C, Berzal-Herranz A. The 5BSL3.2 Functional RNA Domain Connects Distant Regions in the Hepatitis C Virus Genome. Front Microbiol 2017; 8:2093. [PMID: 29163393 PMCID: PMC5671509 DOI: 10.3389/fmicb.2017.02093] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 10/12/2017] [Indexed: 02/05/2023] Open
Abstract
Viral genomes are complexly folded entities that carry all the information required for the infective cycle. The nucleotide sequence of the RNA virus genome encodes proteins and functional information contained in discrete, highly conserved structural units. These so-called functional RNA domains play essential roles in the progression of infection, which requires their preservation from one generation to the next. Numerous functional RNA domains exist in the genome of the hepatitis C virus (HCV). Among them, the 5BSL3.2 domain in the cis-acting replication element (CRE) at the 3' end of the viral open reading frame has become of particular interest given its role in HCV RNA replication and as a regulator of viral protein synthesis. These functionalities are achieved via the establishment of a complex network of long-distance RNA-RNA contacts involving (at least as known to date) the highly conserved 3'X tail, the apical loop of domain IIId in the internal ribosome entry site, and/or the so-called Alt region upstream of the CRE. Changing contacts promotes the execution of different stages of the viral cycle. The 5BSL3.2 domain thus operates at the core of a system that governs the progression of HCV infection. This review summarizes our knowledge of the long-range RNA-RNA interaction network in the HCV genome, with special attention paid to the structural and functional consequences derived from the establishment of different contacts. The potential implications of such interactions in switching between the different stages of the viral cycle are discussed.
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Affiliation(s)
- Cristina Romero-López
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas (IPBLN-CSIC), Granada, Spain
| | - Alfredo Berzal-Herranz
- Instituto de Parasitología y Biomedicina “López-Neyra”, Consejo Superior de Investigaciones Científicas (IPBLN-CSIC), Granada, Spain
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Moulton JD. Using Morpholinos to Control Gene Expression. CURRENT PROTOCOLS IN NUCLEIC ACID CHEMISTRY 2017; 68:4.30.1-4.30.29. [PMID: 28252184 PMCID: PMC7162182 DOI: 10.1002/cpnc.21] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Morpholino oligonucleotides are stable, uncharged, water-soluble molecules used to block complementary sequences of RNA, preventing processing, read-through, or protein binding at those sites. Morpholinos are typically used to block translation of mRNA and to block splicing of pre-mRNA, though they can block other interactions between biological macromolecules and RNA. Morpholinos are effective, specific, and lack non-antisense effects. They work in any cell that transcribes and translates RNA, but must be delivered into the nuclear/cytosolic compartment to be effective. Morpholinos form stable base pairs with complementary nucleic acid sequences but apparently do not bind to proteins to a significant extent. They are not recognized by any proteins and do not undergo protein-mediated catalysis-nor do they mediate RNA cleavage by RNase H or the RISC complex. This work focuses on techniques and background for using Morpholinos. © 2017 by John Wiley & Sons, Inc.
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10
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The chaperone-like activity of the hepatitis C virus IRES and CRE elements regulates genome dimerization. Sci Rep 2017; 7:43415. [PMID: 28233845 PMCID: PMC5324077 DOI: 10.1038/srep43415] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 01/24/2017] [Indexed: 02/08/2023] Open
Abstract
The RNA genome of the hepatitis C virus (HCV) establishes a network of long-distance RNA-RNA interactions that direct the progression of the infective cycle. This work shows that the dimerization of the viral genome, which is initiated at the dimer linkage sequence (DLS) within the 3′UTR, is promoted by the CRE region, while the IRES is a negative regulatory partner. Using differential 2′-acylation probing (SHAPE-dif) and molecular interference (HMX) technologies, the CRE activity was found to mainly lie in the critical 5BSL3.2 domain, while the IRES-mediated effect is dependent upon conserved residues within the essential structural elements JIIIabc, JIIIef and PK2. These findings support the idea that, along with the DLS motif, the IRES and CRE are needed to control HCV genome dimerization. They also provide evidences of a novel function for these elements as chaperone-like partners that fine-tune the architecture of distant RNA domains within the HCV genome.
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Safir Filho M, Martin AR, Benhida R. Assessment of new triplet forming artificial nucleobases as RNA ligands directed towards HCV IRES IIId loop. Bioorg Med Chem Lett 2017; 27:1780-1783. [PMID: 28274634 DOI: 10.1016/j.bmcl.2017.02.061] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 02/21/2017] [Accepted: 02/23/2017] [Indexed: 12/23/2022]
Abstract
We report the synthesis of two new artificial nucleobase scaffolds, 1 and 2, featuring adequate hydrogen bonding donors and acceptors for the molecular recognition of U:A and C:G base pairs, respectively. The tethering of these structures to various amino acids and the assessment of these artificial nucleobase-amino acid conjugates as RNA ligands against a model of HCV IRES IIId domain are also reported. Compound 1e displayed the highest affinity (Kd twice lower than neomycin - control). Moreover, it appears that this interaction is enthalpically and entropically favored.
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Affiliation(s)
- Mauro Safir Filho
- Université Côte d'Azur, CNRS, Institut de Chimie de Nice UMR7272, 06108 Nice, France; CAPES Foundation, Ministry of Education of Brazil, Brasília DF 70040-020, Brazil
| | - Anthony R Martin
- Université Côte d'Azur, CNRS, Institut de Chimie de Nice UMR7272, 06108 Nice, France
| | - Rachid Benhida
- Université Côte d'Azur, CNRS, Institut de Chimie de Nice UMR7272, 06108 Nice, France.
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12
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Ashraf A, Chakravarti A, Roy P, Kar P, Siddiqui O. Frequency of nucleotide sequence variations in the internal ribosome entry site region of hepatitis C virus RNA isolated from responding and non-responding patients with hepatitis C virus genotype 3 infection. Virusdisease 2016; 27:251-259. [PMID: 28466036 PMCID: PMC5394696 DOI: 10.1007/s13337-016-0335-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 07/27/2016] [Indexed: 01/18/2023] Open
Abstract
Located within 5' untranslated region of HCV RNA is internal ribosome entry site (IRES) which directs cap-independent translation of viral polyprotein. Mutations in IRES sequence have been shown to cause changes in efficiency of protein translation in vitro in few instances. No study has been done to investigate association between frequency of nucleotide sequence variations in IRES region of HCV-3 RNA and response to pegylated interferon-α plus ribavirin therapy. Hence, this study was planned to analyze relationship between frequency of nucleotide sequence variations of HCV-3 IRES region and response to therapy. Twenty-seven HCV-3 patients were studied, of whom 19 responded to therapy and 8 did not. Alanine aminotransferase and aspartate aminotransferase levels were significantly lower in responders compared to non-responders. HCV RNA detection and genotyping was performed by nested-PCR and RFLP respectively. Viral load quantification in pre and post therapy samples was done by real time PCR. The viral load was significantly lower in the patients after treatment as compared to before treatment. HCV IRES region from pre-treatment sera of 27 HCV-3 infected patients was amplified by nested PCR and sequenced. Secondary structure of IRES region of HCV-3 was predicted using the M fold Web Server. Mutational analysis revealed hot spot of mutations in HCV-3 IRES region from 40-80 and 210-280 nucleotides. Though more mutations were found in non-responders as compared to responders, this difference was statistically insignificant. Therefore, in addition to IRES region of HCV-3, some other host and viral factors may contribute to therapy outcome.
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Affiliation(s)
- Anzar Ashraf
- Virology Laboratory, Department of Microbiology, Maulana Azad Medical College, New Delhi, Delhi 110002 India
| | - Anita Chakravarti
- Virology Laboratory, Department of Microbiology, Maulana Azad Medical College, New Delhi, Delhi 110002 India
- 79, South Park Apartment, Kalkaji, New Delhi, Delhi 110019 India
| | - Priyamvada Roy
- Virology Laboratory, Department of Microbiology, Maulana Azad Medical College, New Delhi, Delhi 110002 India
| | - Premashish Kar
- Department of Medicine, Maulana Azad Medical College and Associated Lok Nayak Hospital, New Delhi, Delhi 110002 India
| | - Oves Siddiqui
- Virology Laboratory, Department of Microbiology, Maulana Azad Medical College, New Delhi, Delhi 110002 India
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Floden EW, Khawaja A, Vopálenský V, Pospíšek M. HCVIVdb: The hepatitis-C IRES variation database. BMC Microbiol 2016; 16:187. [PMID: 27527702 PMCID: PMC4986321 DOI: 10.1186/s12866-016-0804-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 08/04/2016] [Indexed: 01/22/2023] Open
Abstract
Background Sequence variability in the hepatitis C virus (HCV) genome has led to the development and classification of six genotypes and a number of subtypes. The HCV 5′ untranslated region mainly comprises an internal ribosomal entry site (IRES) responsible for cap-independent synthesis of the viral polyprotein and is conserved among all HCV genotypes. Description Considering the possible high impact of variations in HCV IRES on viral protein production and thus virus replication, we decided to collect the available data on known nucleotide variants in the HCV IRES and their impact on IRES function in translation initiation. The HCV IRES variation database (HCVIVdb) is a collection of naturally occurring and engineered mutation entries for the HCV IRES. Each entry contains contextual information pertaining to the entry such as the HCV genotypic background and links to the original publication. Where available, quantitative data on the IRES efficiency in translation have been collated along with details on the reporter system used to generate the data. Data are displayed both in a tabular and graphical formats and allow direct comparison of results from different experiments. Together the data provide a central resource for researchers in the IRES and hepatitis C-oriented fields. Conclusion The collation of over 1900 mutations enables systematic analysis of the HCV IRES. The database is mainly dedicated to detailed comparative and functional analysis of all the HCV IRES domains, which can further lead to the development of site-specific drug designs and provide a guide for future experiments. HCVIVdb is available at http://www.hcvivdb.org. Electronic supplementary material The online version of this article (doi:10.1186/s12866-016-0804-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Evan W Floden
- Department of Genetics & Microbiology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44, Prague 2, Czech Republic.,Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr. Aiguader 88, Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain
| | - Anas Khawaja
- Department of Genetics & Microbiology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44, Prague 2, Czech Republic
| | - Václav Vopálenský
- Department of Genetics & Microbiology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44, Prague 2, Czech Republic
| | - Martin Pospíšek
- Department of Genetics & Microbiology, Faculty of Science, Charles University in Prague, Viničná 5, 128 44, Prague 2, Czech Republic
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14
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Dixit U, Pandey AK, Mishra P, Sengupta A, Pandey VN. Staufen1 promotes HCV replication by inhibiting protein kinase R and transporting viral RNA to the site of translation and replication in the cells. Nucleic Acids Res 2016; 44:5271-87. [PMID: 27106056 PMCID: PMC4914112 DOI: 10.1093/nar/gkw312] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 04/14/2016] [Indexed: 01/23/2023] Open
Abstract
Persistent hepatitis C virus (HCV) infection leads to chronic hepatitis C (CHC), which often progresses to liver cirrhosis (LC) and hepatocellular carcinoma (HCC). The molecular mechanisms that establish CHC and cause its subsequent development into LC and HCC are poorly understood. We have identified a cytoplasmic double-stranded RNA binding protein, Stau1, which is crucial for HCV replication. In this study, Stau1 specifically interacted with the variable-stem-loop region in the 3′ NTR and domain IIId of the HCV-IRES in the 5′ NTR, and promoted HCV replication and translation. Stau1 coimmunoprecipitates HCV NS5B and a cell factor, protein kinase R (PKR), which is critical for interferon-induced cellular antiviral and antiproliferative responses. Like Stau1, PKR displayed binding specificity to domain IIId of HCV-IRES. Stau1 binds to PKR and strongly inhibits PKR-autophosphorylation. We demonstrated that the transport of HCV RNA on the polysomes is Stau1-dependent, being mainly localized in the monosome fractions when Stau1 is downregulated and exclusively localized in the polysomes when Stau1 is overexpressed. Our findings suggest that HCV may appropriate Stau1 to its advantage to prevent PKR-mediated inhibition of eIF2α, which is required for the synthesis of HCV proteins for translocation of viral RNA genome to the polysomes for efficient translation and replication.
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Affiliation(s)
- Updesh Dixit
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, Rutgers, the State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Ashutosh K Pandey
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, Rutgers, the State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Priya Mishra
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, Rutgers, the State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Amitabha Sengupta
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, Rutgers, the State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Virendra N Pandey
- Department of Microbiology, Biochemistry and Molecular Genetics, New Jersey Medical School, Rutgers, Rutgers, the State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
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Thakor N, Smith MD, Roberts L, Faye MD, Patel H, Wieden HJ, Cate JHD, Holcik M. Cellular mRNA recruits the ribosome via eIF3-PABP bridge to initiate internal translation. RNA Biol 2016; 14:553-567. [PMID: 26828225 PMCID: PMC5449081 DOI: 10.1080/15476286.2015.1137419] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
IRES-mediated translation of key cell fate regulating genes has been implicated in tumorigenesis. Concerted action of canonical eukaryotic initiation factors and IRES transacting factors (ITAFs) was shown to regulate cellular IRES mediated translation; however, the precise molecular mechanism of ribosome recruitment to cellular IRESes remains unclear. Here we show that the X-linked inhibitor of apoptosis (XIAP) IRES operates in an evolutionary conserved viral like mode and the structural integrity, particularly in the vicinity of AUG, is critical for ribosome recruitment. The binding of eIF3 together with PABP potentiates ribosome recruitment to the IRES. Our data support the model in which eIF3 binds directly to the XIAP IRES RNA in a structure-dependent manner and acts as a scaffold for IRES RNA, PABP and the 40S ribosome.
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Affiliation(s)
- Nehal Thakor
- a Apoptosis Research Center , Children's Hospital of Eastern Ontario Research Institute , Ottawa , Ontario , Canada.,c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - M Duane Smith
- d Department of Molecular and Cell Biology , University of California , Berkeley , CA , USA
| | - Luc Roberts
- c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - Mame Daro Faye
- a Apoptosis Research Center , Children's Hospital of Eastern Ontario Research Institute , Ottawa , Ontario , Canada
| | - Harshil Patel
- c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - Hans-Joachim Wieden
- c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - Jamie H D Cate
- d Department of Molecular and Cell Biology , University of California , Berkeley , CA , USA
| | - Martin Holcik
- a Apoptosis Research Center , Children's Hospital of Eastern Ontario Research Institute , Ottawa , Ontario , Canada.,b Department of Pediatrics , University of Ottawa , Ottawa , Ontario , Canada
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Angulo J, Ulryck N, Deforges J, Chamond N, Lopez-Lastra M, Masquida B, Sargueil B. LOOP IIId of the HCV IRES is essential for the structural rearrangement of the 40S-HCV IRES complex. Nucleic Acids Res 2015; 44:1309-25. [PMID: 26626152 PMCID: PMC4756818 DOI: 10.1093/nar/gkv1325] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/11/2015] [Indexed: 12/14/2022] Open
Abstract
As obligatory intracellular parasites, viruses rely on cellular machines to complete their life cycle, and most importantly they recruit the host ribosomes to translate their mRNA. The Hepatitis C viral mRNA initiates translation by directly binding the 40S ribosomal subunit in such a way that the initiation codon is correctly positioned in the P site of the ribosome. Such a property is likely to be central for many viruses, therefore the description of host-pathogen interaction at the molecular level is instrumental to provide new therapeutic targets. In this study, we monitored the 40S ribosomal subunit and the viral RNA structural rearrangement induced upon the formation of the binary complex. We further took advantage of an IRES viral mutant mRNA deficient for translation to identify the interactions necessary to promote translation. Using a combination of structure probing in solution and molecular modeling we establish a whole atom model which appears to be very similar to the one obtained recently by cryoEM. Our model brings new information on the complex, and most importantly reveals some structural rearrangement within the ribosome. This study suggests that the formation of a ‘kissing complex’ between the viral RNA and the 18S ribosomal RNA locks the 40S ribosomal subunit in a conformation proficient for translation.
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Affiliation(s)
- Jenniffer Angulo
- CNRS UMR 8015, Laboratoire de cristallographie et RMN Biologiques, Université Paris Descartes, 4 avenue de l'Observatoire, 75270 Paris Cedex 06, France Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Escuela de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Nathalie Ulryck
- CNRS UMR 8015, Laboratoire de cristallographie et RMN Biologiques, Université Paris Descartes, 4 avenue de l'Observatoire, 75270 Paris Cedex 06, France
| | - Jules Deforges
- CNRS UMR 8015, Laboratoire de cristallographie et RMN Biologiques, Université Paris Descartes, 4 avenue de l'Observatoire, 75270 Paris Cedex 06, France
| | - Nathalie Chamond
- CNRS UMR 8015, Laboratoire de cristallographie et RMN Biologiques, Université Paris Descartes, 4 avenue de l'Observatoire, 75270 Paris Cedex 06, France
| | - Marcelo Lopez-Lastra
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Escuela de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile
| | - Benoît Masquida
- UMR 7156 Génétique Moléculaire Génomique Microbiologie, CNRS - Université de Strasbourg, Strasbourg, France
| | - Bruno Sargueil
- CNRS UMR 8015, Laboratoire de cristallographie et RMN Biologiques, Université Paris Descartes, 4 avenue de l'Observatoire, 75270 Paris Cedex 06, France
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17
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Mauro VP, Matsuda D. Translation regulation by ribosomes: Increased complexity and expanded scope. RNA Biol 2015; 13:748-55. [PMID: 26513496 DOI: 10.1080/15476286.2015.1107701] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The primary function of ribosomes is to decode mRNAs into polypeptide chains; however, this description is overly simplistic. Accumulating evidence shows that ribosomes themselves can affect the relative efficiency with which various mRNAs are translated and indicates that these effects can be modulated by ribosome heterogeneity. The notion that ribosomes have regulatory capabilities was elaborated more than a decade ago in the ribosome filter hypothesis. Various lines of evidence support this idea and have shown that the translation of some mRNAs is affected by discrete binding interactions with rRNA or ribosomal proteins. Recent work from our laboratory has demonstrated that base-pairing of the Hepatitis C Virus (HCV) internal ribosome entry site (IRES) to 18S rRNA is required for IRES function, but only in the context of more complex ribosomal interactions. The HCV IRES provides an example of the ribosome filter that involves multiple binding interactions between mRNAs and ribosomal subunits.
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Affiliation(s)
- Vincent P Mauro
- a Promosome, LLC , San Diego , CA , USA.,b The Scripps Research Institute , La Jolla , CA , USA
| | - Daiki Matsuda
- b The Scripps Research Institute , La Jolla , CA , USA
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18
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Bader El Din NG, El Hefnawy MM, Omran MH, Dawood RM, El Abd Y, Ibrahim MK, El Awady MK. Spontaneous clearance of chronic hepatitis C infection is associated with an internal ribosomal entry site IIId stem loop structure variant. Indian J Med Microbiol 2015; 33 Suppl:143-8. [PMID: 25657135 DOI: 10.4103/0255-0857.148835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIM To investigate if any mutations in hepatitis C virus (HCV) internal ribosome entry site (IRES) can inhibit the translation of viral polyprotein. MATERIALS AND METHODS A 26-year-old male patient infected with HCV 10 years ago was followed up. After 9 years of chronic infection. The patient had managed to resolve the infection for a period of 9 months, after which the patient experienced a viral recurrence characterized by high viral load and diverse HCV quasispecies. The IRES structures of the viral strains that disappeared were comparable with those that are currently active using structural mutational analysis. RESULTS A novo mutational position 254 combined with a rarely observed mutation at position 253 in the stem of the IIId subdomain were observed and the new conformation had an octa-apical loop (AGUGUUGG) and a shift in the 3 ` GU from the loop to the stem. CONCLUSIONS These mutations were found to be highly deleterious, and they affected the direct binding of the IIId loop to the 40S ribosomal subunit with a subsequent inhibition of translation of viral polyprotein and clearance of the virus.
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Affiliation(s)
- N G Bader El Din
- Department of Microbial Biotechnology , National Research Center, Tahrir, Dokki, Cairo, Egypt
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19
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Abstract
Pestiviruses are among the economically most important pathogens of livestock. The biology of these viruses is characterized by unique and interesting features that are both crucial for their success as pathogens and challenging from a scientific point of view. Elucidation of these features at the molecular level has made striking progress during recent years. The analyses revealed that major aspects of pestivirus biology show significant similarity to the biology of human hepatitis C virus (HCV). The detailed molecular analyses conducted for pestiviruses and HCV supported and complemented each other during the last three decades resulting in elucidation of the functions of viral proteins and RNA elements in replication and virus-host interaction. For pestiviruses, the analyses also helped to shed light on the molecular basis of persistent infection, a special strategy these viruses have evolved to be maintained within their host population. The results of these investigations are summarized in this chapter.
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Affiliation(s)
- Norbert Tautz
- Institute for Virology and Cell Biology, University of Lübeck, Lübeck, Germany
| | - Birke Andrea Tews
- Institut für Immunologie, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany
| | - Gregor Meyers
- Institut für Immunologie, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Greifswald-Insel Riems, Germany.
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20
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Khawaja A, Vopalensky V, Pospisek M. Understanding the potential of hepatitis C virus internal ribosome entry site domains to modulate translation initiation via their structure and function. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 6:211-24. [PMID: 25352252 PMCID: PMC4361049 DOI: 10.1002/wrna.1268] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Revised: 08/31/2014] [Accepted: 09/02/2014] [Indexed: 12/16/2022]
Abstract
Translation initiation in the hepatitis C virus (HCV) occurs through a cap-independent mechanism that involves an internal ribosome entry site (IRES) capable of interacting with and utilizing the eukaryotic translational machinery. In this review, we focus on the structural configuration of the different HCV IRES domains and the impact of IRES primary sequence variations on secondary structure conservation and function. In some cases, multiple mutations, even those scattered across different domains, led to restoration of the translational activity of the HCV IRES, although the individual occurrences of these mutations were found to be deleterious. We propose that such observation may be attributed to probable long-range inter- and/or intra-domain functional interactions. The precise functioning of the HCV IRES requires the specific interaction of its domains with ribosomal subunits and a subset of eukaryotic translation initiation factors (eIFs). The structural conformation, sequence preservation and variability, and translational machinery association with the HCV IRES regions are also thoroughly discussed, along with other factors that can affect and influence the formation of translation initiation complexes. WIREs RNA 2015, 6:211–224. doi: 10.1002/wrna.1268
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Affiliation(s)
- Anas Khawaja
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Prague 2, Czech Republic
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21
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Base pairing between hepatitis C virus RNA and 18S rRNA is required for IRES-dependent translation initiation in vivo. Proc Natl Acad Sci U S A 2014; 111:15385-9. [PMID: 25313046 DOI: 10.1073/pnas.1413472111] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Degeneracy in eukaryotic translation initiation is evident in the initiation strategies of various viruses. Hepatitis C virus (HCV) provides an exceptional example--translation of the HCV RNA is facilitated by an internal ribosome entry site (IRES) that can autonomously bind a 40S ribosomal subunit and accurately position it at the initiation codon. This binding involves both ribosomal protein and 18S ribosomal RNA (rRNA) interactions. In this study, we evaluate the functional significance of the rRNA interaction and show that HCV IRES activity requires a 3-nt Watson-Crick base-pairing interaction between the apical loop of subdomain IIId in the IRES and helix 26 in 18S rRNA. Mutations of these nucleotides in either RNA dramatically disrupted IRES activity. The activities of the mutated HCV IRESs could be restored by compensatory mutations in the 18S rRNA. The effects of the 18S rRNA mutations appeared to be specific inasmuch as ribosomes containing these mutations did not support translation mediated by the wild-type HCV IRES, but did not block translation mediated by the cap structure or other viral IRESs. The present study provides, to our knowledge, the first functional demonstration of mRNA-rRNA base pairing in mammalian cells. By contrast with other rRNA-binding sites in mRNAs that can enhance translation as independent elements, e.g., the Shine-Dalgarno sequence in prokaryotes, the rRNA-binding site in the HCV IRES functions as an essential component of a more complex interaction.
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22
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Measurement of the change in twist at a helical junction in RNA using the orientation dependence of FRET. Biophys J 2014; 105:2175-81. [PMID: 24209863 DOI: 10.1016/j.bpj.2013.09.042] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 09/04/2013] [Accepted: 09/23/2013] [Indexed: 02/05/2023] Open
Abstract
Indocarbocyanine fluorophores attached via the 5' terminus of double-stranded nucleic acids have a strong propensity to stack onto the terminal basepair. We previously demonstrated that the efficiency of fluorescence resonance energy transfer between cyanine 3 and 5 terminally attached to duplex species exhibits a pronounced modulation with helix length. This results from a systematic variation in the orientation parameter κ(2) as the relative rotation of the fluorophore transition moments changes due to the helical geometry. Analysis of such profiles provides a rich source of orientational information. In this work, we applied this methodology to the structure of a three-way helical junction that plays an important role in the hepatitis C virus internal ribosome entry site. By comparing matched pairs of duplex and junction species, we were able to measure the change in rotation at the junction. The data reveal a 29.5° overwinding and a small axial extension. This shows the power of this approach for measuring orientational information in biologically important RNA junctions.
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23
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Romero-López C, Berzal-Herranz A. Structure-function relationship in viral RNA genomes: The case of hepatitis C virus. World J Med Genet 2014; 4:6-18. [DOI: 10.5496/wjmg.v4.i2.6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 01/23/2014] [Accepted: 04/03/2014] [Indexed: 02/06/2023] Open
Abstract
The acquisition of a storage information system beyond the nucleotide sequence has been a crucial issue for the propagation and dispersion of RNA viruses. This system is composed by highly conserved, complex structural units in the genomic RNA, termed functional RNA domains. These elements interact with other regions of the viral genome and/or proteins to direct viral translation, replication and encapsidation. The genomic RNA of the hepatitis C virus (HCV) is a good model for investigating about conserved structural units. It contains functional domains, defined by highly conserved structural RNA motifs, mostly located in the 5’-untranslatable regions (5’UTRs) and 3’UTR, but also occupying long stretches of the coding sequence. Viral translation initiation is mediated by an internal ribosome entry site located at the 5’ terminus of the viral genome and regulated by distal functional RNA domains placed at the 3’ end. Subsequent RNA replication strongly depends on the 3’UTR folding and is also influenced by the 5’ end of the HCV RNA. Further increase in the genome copy number unleashes the formation of homodimers by direct interaction of two genomic RNA molecules, which are finally packed and released to the extracellular medium. All these processes, as well as transitions between them, are controlled by structural RNA elements that establish a complex, direct and long-distance RNA-RNA interaction network. This review summarizes current knowledge about functional RNA domains within the HCV RNA genome and provides an overview of the control exerted by direct, long-range RNA-RNA contacts for the execution of the viral cycle.
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24
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Malygin AA, Kossinova OA, Shatsky IN, Karpova GG. HCV IRES interacts with the 18S rRNA to activate the 40S ribosome for subsequent steps of translation initiation. Nucleic Acids Res 2013; 41:8706-14. [PMID: 23873958 PMCID: PMC3794592 DOI: 10.1093/nar/gkt632] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Previous analyses of complexes of 40S ribosomal subunits with the hepatitis C virus (HCV) internal ribosome entry site (IRES) have revealed contacts made by the IRES with ribosomal proteins. Here, using chemical probing, we show that the HCV IRES also contacts the backbone and bases of the CCC triplet in the 18S ribosomal RNA (rRNA) expansion segment 7. These contacts presumably provide interplay between IRES domain II and the AUG codon close to ribosomal protein S5, which causes a rearrangement of 18S rRNA structure in the vicinity of the universally conserved nucleotide G1639. As a result, G1639 becomes exposed and the corresponding site of the 40S subunit implicated in transfer RNA discrimination can select . These data are the first demonstration at nucleotide resolution of direct IRES–rRNA interactions and how they induce conformational transition in the 40S subunit allowing the HCV IRES to function without AUG recognition initiation factors.
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Affiliation(s)
- Alexey A Malygin
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia
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25
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Plank TDM, Whitehurst JT, Kieft JS. Cell type specificity and structural determinants of IRES activity from the 5' leaders of different HIV-1 transcripts. Nucleic Acids Res 2013; 41:6698-714. [PMID: 23661682 PMCID: PMC3711417 DOI: 10.1093/nar/gkt358] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Internal ribosome entry site (IRES) RNAs are important regulators of gene expression, but their diverse molecular mechanisms remain partially understood. The HIV-1 gag transcript leader contains an IRES that may be a good model for understanding the function of many other IRESs. We investigated the possibility that this IRES’ function is linked to both the structure of the RNA and its cellular environment. We find that in the context of a bicistronic reporter construct, HIV-1 gag IRES’ activity is cell type-specific, with higher activity in T-cell culture systems that model the natural target cells for HIV-1 infection. This finding underscores how an IRES may be fine tuned to function in certain cells, perhaps owing to cell type-specific protein factors. Using RNA probing and mutagenesis, we demonstrate that the HIV-1 gag IRES does not use pre-folded RNA structure to drive function, a finding that gives insight into how conformationally dynamic IRESs operate. Furthermore, we find that a common exon drives IRES activity in a diverse set of alternatively spliced transcripts. We propose a mechanism in which a structurally plastic RNA element confers the ability to initiate translation internally, and activity from this common element is modulated by 3′ nucleotides added by alternative splicing.
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Affiliation(s)
- Terra-Dawn M Plank
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, Aurora, Colorado, 80045, USA
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26
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Shetty S, Stefanovic S, Mihailescu MR. Hepatitis C virus RNA: molecular switches mediated by long-range RNA-RNA interactions? Nucleic Acids Res 2012; 41:2526-40. [PMID: 23275555 PMCID: PMC3575821 DOI: 10.1093/nar/gks1318] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Multiple conserved structural cis-acting regulatory elements have been recognized both in the coding and untranslated regions (UTRs) of the hepatitis C virus (HCV) genome. For example, the cis-element 5BSL3.2 in the HCV-coding region has been predicted to use both its apical and internal loops to interact with the X RNA in the 3'-UTR, with the IIId domain in the 5'-UTR and with the Alt sequence in the coding region. Additionally, the X RNA region uses a palindromic sequence that overlaps the sequence required for the interaction with 5BSL3.2, to dimerize with another HCV genome. The ability of the 5BSL3.2 and X RNA regions to engage in multi-interactions suggests the existence of one or more molecular RNA switches which may regulate different steps of the HCV life cycle. In this study, we used biophysical methods to characterize the essential interactions of these HCV cis-elements at the molecular level. Our results indicate that X RNA interacts with 5BSL3.2 and another X RNA molecule by adopting two different conformations and that 5BSL3.2 engages simultaneously in kissing interactions using its apical and internal loops. Based on these results, we propose a mode of action for possible molecular switches involving the HCV RNA.
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Affiliation(s)
- Sumangala Shetty
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15282, USA
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27
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Penn AC, Balik A, Greger IH. Steric antisense inhibition of AMPA receptor Q/R editing reveals tight coupling to intronic editing sites and splicing. Nucleic Acids Res 2012; 41:1113-23. [PMID: 23172291 PMCID: PMC3553965 DOI: 10.1093/nar/gks1044] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Adenosine-to-Inosine (A-to-I) RNA editing is a post-transcriptional mechanism, evolved to diversify the transcriptome in metazoa. In addition to wide-spread editing in non-coding regions protein recoding by RNA editing allows for fine tuning of protein function. Functional consequences are only known for some editing sites and the combinatorial effect between multiple sites (functional epistasis) is currently unclear. Similarly, the interplay between RNA editing and splicing, which impacts on post-transcriptional gene regulation, has not been resolved. Here, we describe a versatile antisense approach, which will aid resolving these open questions. We have developed and characterized morpholino oligos targeting the most efficiently edited site—the AMPA receptor GluA2 Q/R site. We show that inhibition of editing closely correlates with intronic editing efficiency, which is linked to splicing efficiency. In addition to providing a versatile tool our data underscore the unique efficiency of a physiologically pivotal editing site.
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Affiliation(s)
- Andrew C Penn
- Neurobiology Division, MRC Laboratory of Molecular Biology, CB2 0QH Cambridge, UK.
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28
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de Breyne S, Soto-Rifo R, López-Lastra M, Ohlmann T. Translation initiation is driven by different mechanisms on the HIV-1 and HIV-2 genomic RNAs. Virus Res 2012; 171:366-81. [PMID: 23079111 DOI: 10.1016/j.virusres.2012.10.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 10/05/2012] [Accepted: 10/08/2012] [Indexed: 02/08/2023]
Abstract
The human immunodeficiency virus (HIV) unspliced full length genomic RNA possesses features of an eukaryotic cellular mRNA as it is capped at its 5' end and polyadenylated at its 3' extremity. This genomic RNA is used both for the production of the viral structural and enzymatic proteins (Gag and Pol, respectively) and as genome for encapsidation in the newly formed viral particle. Although both of these processes are critical for viral replication, they should be controlled in a timely manner for a coherent progression into the viral cycle. Some of this regulation is exerted at the level of translational control and takes place on the viral 5' untranslated region and the beginning of the gag coding region. In this review, we have focused on the different initiation mechanisms (cap- and internal ribosome entry site (IRES)-dependent) that are used by the HIV-1 and HIV-2 genomic RNAs and the cellular and viral factors that can modulate their expression. Interestingly, although HIV-1 and HIV-2 share many similarities in the overall clinical syndrome they produce, in some aspects of their replication cycle, and in the structure of their respective genome, they exhibit some differences in the way that ribosomes are recruited on the gag mRNA to initiate translation and produce the viral proteins; this will be discussed in the light of the literature.
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29
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Romero-López C, Barroso-Deljesus A, García-Sacristán A, Briones C, Berzal-Herranz A. The folding of the hepatitis C virus internal ribosome entry site depends on the 3'-end of the viral genome. Nucleic Acids Res 2012; 40:11697-713. [PMID: 23066110 PMCID: PMC3526292 DOI: 10.1093/nar/gks927] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Hepatitis C virus (HCV) translation initiation is directed by an internal ribosome entry site (IRES) and regulated by distant regions at the 3′-end of the viral genome. Through a combination of improved RNA chemical probing methods, SHAPE structural analysis and screening of RNA accessibility using antisense oligonucleotide microarrays, here, we show that HCV IRES folding is fine-tuned by the genomic 3′-end. The essential IRES subdomains IIIb and IIId, and domain IV, adopted a different conformation in the presence of the cis-acting replication element and/or the 3′-untranslatable region compared to that taken up in their absence. Importantly, many of the observed changes involved significant decreases in the dimethyl sulfate or N-methyl-isatoic anhydride reactivity profiles at subdomains IIIb and IIId, while domain IV appeared as a more flexible element. These observations were additionally confirmed in a replication-competent RNA molecule. Significantly, protein factors are not required for these conformational differences to be made manifest. Our results suggest that a complex, direct and long-distance RNA–RNA interaction network plays an important role in the regulation of HCV translation and replication, as well as in the switching between different steps of the viral cycle.
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Affiliation(s)
- Cristina Romero-López
- Departamento de Biología Molecular, Instituto de Parasitología y Biomedicina López-Neyra, IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento s/n, Armilla, 18100 Granada, Spain.
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Abstract
Modulation of translation initiation efficiency on classical swine fever virus (CSFV) RNA can be achieved by targeted mutations within the internal ribosome entry site (IRES). In this study, cDNAs corresponding to the wild-type (wt) or mutant forms of the IRES of CSFV strain Paderborn were amplified and inserted into dicistronic reporter plasmids encoding Fluc and Rluc under the control of a T7 promoter. The mutations were within domains II, IIId(1), and IIIf of the IRES. The plasmids were transfected into baby hamster kidney (BHK) cells infected with recombinant vaccinia virus vTF7-3, which expresses the T7 RNA polymerase. IRES mutants with different levels of IRES activity were identified and then introduced by homologous recombination into bacterial artificial chromosomes (BACs) containing CSFV Paderborn cDNA downstream of a T7 promoter. From the wt and mutant BACs, full-length CSFV RNA transcripts were produced in vitro and electroporated into porcine PK15 cells. Rescued mutant viruses were obtained from RNAs that contained mutations within domain IIIf which retained more than 75% of the wt translation efficiency. Sequencing of cDNA generated from these rescued viruses verified the maintenance of the introduced changes within the IRES. The growth characteristics of each rescued mutant virus were compared to those of the wt virus. It was shown that viable mutant viruses with reduced translation initiation efficiency can be designed and generated and that viruses containing mutations within domain IIIf of the IRES have reduced growth in cell culture compared to the wt virus.
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31
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Tuplin A, Struthers M, Simmonds P, Evans DJ. A twist in the tail: SHAPE mapping of long-range interactions and structural rearrangements of RNA elements involved in HCV replication. Nucleic Acids Res 2012; 40:6908-21. [PMID: 22561372 PMCID: PMC3413155 DOI: 10.1093/nar/gks370] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The RNA structure and long-range interactions of the SL9266 cis-acting replication element located within the NS5B coding region of hepatitis C virus (HCV) were determined using selective 2′-hydroxyl acylation analysed by primer extension. Marked differences were found in the long-range interactions of SL9266 when the two widely used genotype 2a JFH-1 (HCVcc) and genotype 1b Con1b sub-genomic replicon systems were compared. In both genomes, there was evidence for interaction of the sub-terminal bulge loop of SL9266 and sequences around nucleotide 9110, though the replication phenotype of genomes bearing mutations that disrupted this interaction was fundamentally different. In contrast, a ‘kissing loop’ interaction between the terminal loop of SL9266 and sequences in the 3′-untranslated X-tail was only detectable in JFH-1-based genomes. In the latter, where both long-range interactions are present, they were independent, implying that SL9266 forms the core of an extended pseudoknot. The presence of the ‘kissing loop’ interaction inhibited the formation of SL9571 in the 3′-X-tail, an RNA structure implicated in genome replication. We propose that, SL9266 may contribute a switch function that modulates the mutually incompatible translation and replication events that must occur for replication of the positive-strand RNA genome of HCV.
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Affiliation(s)
- Andrew Tuplin
- School of Life Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
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Romero-López C, Berzal-Herranz B, Gómez J, Berzal-Herranz A. An engineered inhibitor RNA that efficiently interferes with hepatitis C virus translation and replication. Antiviral Res 2012; 94:131-8. [PMID: 22426470 DOI: 10.1016/j.antiviral.2012.02.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 01/25/2012] [Accepted: 02/28/2012] [Indexed: 02/08/2023]
Abstract
Hepatitis C virus (HCV) translation is mediated by a highly conserved internal ribosome entry site (IRES), mainly located at the 5'untranslatable region (5'UTR) of the viral genome. Viral protein synthesis clearly differs from that used by most cellular mRNAs, rendering the IRES an attractive target for novel antiviral compounds. The engineering of RNA compounds is an effective strategy for targeting conserved functional regions in viral RNA genomes. The present work analyses the anti-HCV potential of HH363-24, an in vitro selected molecule composed of a catalytic RNA cleaving domain with an extension at the 3' end that acts as aptamer for the viral 5'UTR. The engineered HH363-24 efficiently cleaved the HCV genome and bound to the essential IIId domain of the IRES region. This action interfered with the proper assembly of the translationally active ribosomal particles 48S and 80S, likely leading to effective inhibition of the IRES function in a hepatic cell line. HH363-24 also efficiently reduced HCV RNA levels up to 70% in a subgenomic replicon system. These findings provide new insights into the development of potential therapeutic strategies based on RNA molecules targeting genomic RNA structural domains and highlight the feasibility of generating novel engineered RNAs as potent antiviral agents.
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Affiliation(s)
- Cristina Romero-López
- Instituto de Parasitología y Biomedicina "López-Neyra", IPBLN-CSIC, Parque Tecnológico de Ciencias de la Salud, Armilla, Granada, Spain
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Romero-López C, Berzal-Herranz A. The functional RNA domain 5BSL3.2 within the NS5B coding sequence influences hepatitis C virus IRES-mediated translation. Cell Mol Life Sci 2012; 69:103-13. [PMID: 21598019 PMCID: PMC11115049 DOI: 10.1007/s00018-011-0729-z] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 04/12/2011] [Accepted: 05/05/2011] [Indexed: 02/06/2023]
Abstract
Hepatitis C virus (HCV) translation is mediated by an internal ribosome entry site (IRES) located at the 5' end of the genomic RNA. The 3' untranslatable region (3'UTR) stimulates translation by the recruitment of protein factors that simultaneously bind to the 5' end of the viral genome. This leads to the formation of a macromolecular complex with a closed loop conformation, similar to that described for the cap-translated mRNAs. We previously demonstrated the existence of a long-range RNA-RNA interaction involving subdomain IIId of the IRES region and the stem-loop 5BSL3.2 of the CRE element at the 3' end of the viral genome. The present study provides evidence that the enhancement of HCV IRES-dependent translation mediated by the 3'UTR is negatively controlled by the CRE region in the human hepatoma cell lines Huh-7 and Hep-G2 in a time-dependent manner. Domain 5BSL3.2 is the major partner in this process. Mutations in this motif lead to an increase in IRES activity by up to eightfold. These data support the existence of a functional high order structure in the HCV genome that involves two evolutionarily conserved RNA elements, domain IIId in the IRES and stem-loop 5BSL3.2 in the CRE region. This interaction could have a role in the circularisation of the viral genome.
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Affiliation(s)
- Cristina Romero-López
- Instituto de Parasitología y Biomedicina “López-Neyra” IPBLN-CSIC, CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento s/n, 18100 Armilla, Granada Spain
| | - Alfredo Berzal-Herranz
- Instituto de Parasitología y Biomedicina “López-Neyra” IPBLN-CSIC, CSIC, Parque Tecnológico de Ciencias de la Salud, Avda. del Conocimiento s/n, 18100 Armilla, Granada Spain
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Burks JM, Zwieb C, Müller F, Wower IK, Wower J. Comparative structural studies of bovine viral diarrhea virus IRES RNA. Virus Res 2011; 160:136-42. [DOI: 10.1016/j.virusres.2011.06.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 05/28/2011] [Accepted: 06/01/2011] [Indexed: 02/03/2023]
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eIF2A mediates translation of hepatitis C viral mRNA under stress conditions. EMBO J 2011; 30:2454-64. [PMID: 21556050 DOI: 10.1038/emboj.2011.146] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 04/13/2011] [Indexed: 02/08/2023] Open
Abstract
Translation of most mRNAs is suppressed under stress conditions. Phosphorylation of the α-subunit of eukaryotic translation initiation factor 2 (eIF2), which delivers initiator tRNA (Met-tRNA(i)) to the P site of the 40S ribosomal subunit, is responsible for such translational suppression. However, translation of hepatitis C viral (HCV) mRNA is refractory to the inhibitory effects of eIF2α phosphorylation, which prevents translation by disrupting formation of the eIF2-GTP-Met-tRNA(i) ternary complex. Here, we report that eIF2A, an alternative initiator tRNA-binding protein, has a key role in the translation of HCV mRNA during HCV infection, in turn promoting eIF2α phosphorylation by activating the eIF2α kinase PKR. Direct interaction of eIF2A with the IIId domain of the HCV internal ribosome entry site (IRES) is required for eIF2A-dependent translation. These data indicate that stress-independent translation of HCV mRNA occurs by recruitment of eIF2A to the HCV IRES via direct interaction with the IIId domain and subsequent loading of Met-tRNA(i) to the P site of the 40S ribosomal subunit.
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Structural features of the Seneca Valley virus internal ribosome entry site (IRES) element: a picornavirus with a pestivirus-like IRES. J Virol 2011; 85:4452-61. [PMID: 21325406 DOI: 10.1128/jvi.01107-10] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The RNA genome of Seneca Valley virus (SVV), a recently identified picornavirus, contains an internal ribosome entry site (IRES) element which has structural and functional similarity to that from classical swine fever virus (CSFV) and hepatitis C virus, members of the Flaviviridae. The SVV IRES has an absolute requirement for the presence of a short region of virus-coding sequence to allow it to function either in cells or in rabbit reticulocyte lysate. The IRES activity does not require the translation initiation factor eIF4A or intact eIF4G. The predicted secondary structure indicates that the SVV IRES is more closely related to the CSFV IRES, including the presence of a bipartite IIId domain. Mutagenesis of the SVV IRES, coupled to functional assays, support the core elements of the IRES structure model, but surprisingly, deletion of the conserved IIId(2) domain had no effect on IRES activity, including 40S and eIF3 binding. This is the first example of a picornavirus IRES that is most closely related to the CSFV IRES and suggests the possibility of multiple, independent recombination events between the genomes of the Picornaviridae and Flaviviridae to give rise to similar IRES elements.
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Ouellet J, Melcher S, Iqbal A, Ding Y, Lilley DMJ. Structure of the three-way helical junction of the hepatitis C virus IRES element. RNA (NEW YORK, N.Y.) 2010; 16:1597-1609. [PMID: 20581129 PMCID: PMC2905758 DOI: 10.1261/rna.2158410] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2010] [Accepted: 05/04/2010] [Indexed: 05/29/2023]
Abstract
The hepatitis C virus internal ribosome entry site (IRES) element contains a three-way junction that is important in the overall RNA conformation, and for its role in the internal initiation of translation. The junction also illustrates some important conformational principles in the folding of three-way helical junctions. It is formally a 3HS(4) junction, with the possibility of two alternative stacking conformers. However, in principle, the junction can also undergo two steps of branch migration that would form 2HS(1)HS(3) and 2HS(2)HS(2) junctions. Comparative gel electrophoresis and ensemble fluorescence resonance energy transfer (FRET) studies show that the junction is induced to fold by the presence of Mg(2+) ions in low micromolar concentrations, and suggest that the structure adopted is based on coaxial stacking of the two helices that do not terminate in a hairpin loop (i.e., helix IIId). Single-molecule FRET studies confirm this conclusion, and indicate that there is no minor conformer present based on an alternative choice of helical stacking partners. Moreover, analysis of single-molecule FRET data at an 8-msec resolution failed to reveal evidence for structural transitions. It seems probable that this junction adopts a single conformation as a unique and stable fold.
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Affiliation(s)
- Jonathan Ouellet
- Cancer Research UK Nucleic Acid Structure Research Group, MSI/WTB Complex, The University of Dundee, Dundee DD1 5EH, United Kingdom
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Jangra RK, Yi M, Lemon SM. Regulation of hepatitis C virus translation and infectious virus production by the microRNA miR-122. J Virol 2010; 84:6615-25. [PMID: 20427538 PMCID: PMC2903297 DOI: 10.1128/jvi.00417-10] [Citation(s) in RCA: 254] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 04/16/2010] [Indexed: 12/14/2022] Open
Abstract
miR-122 is a liver-specific microRNA that positively regulates hepatitis C virus (HCV) RNA abundance and is essential for production of infectious HCV. Using a genetic approach, we show that its ability to enhance yields of infectious virus is dependent upon two miR-122-binding sites near the 5' end of the HCV genome, S1 and S2. Viral RNA with base substitutions in both S1 and S2 failed to produce infectious virus in transfected cells, while virus production was rescued to near-wild-type levels in cells supplemented with a complementary miR-122 mutant. A comparison of mutants with substitutions in only one site revealed S1 to be dominant, as an S2 but not S1 mutant produced high virus yields in cells supplemented with wild-type miR-122. Translation of HCV RNA was reduced over 50% by mutations in either S1 or S2 and was partially rescued by transfection of the complementary miR-122 mutant. Unlike the case for virus replication, however, both sites function equally in regulating translation. We conclude that miR-122 promotes replication by binding directly to both sites in the genomic RNA and, at least in part, by stimulating internal ribosome entry site (IRES)-mediated translation. However, a comparison of the replication capacities of the double-binding-site mutant and an IRES mutant with a quantitatively equivalent defect in translation suggests that the decrement in translation associated with loss of miR-122 binding is insufficient to explain the profound defect in virus production by the double mutant. miR-122 is thus likely to act at an additional step in the virus life cycle.
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Affiliation(s)
- Rohit K. Jangra
- Center for Hepatitis Research, Institute for Human Infections and Immunity, and Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas 77555-0610
| | - MinKyung Yi
- Center for Hepatitis Research, Institute for Human Infections and Immunity, and Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas 77555-0610
| | - Stanley M. Lemon
- Center for Hepatitis Research, Institute for Human Infections and Immunity, and Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas 77555-0610
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Abstract
The current standard of care for the treatment of hepatitis C virus infection, pegylated interferon-alpha and ribavirin, is costly, associated with significant side effects, and effective in only 50% of patients. There is therefore a need for the development of novel antiviral therapies. One such approach involves the application of gene silencing technologies, including antisense oligonucleotides, ribozymes, RNA interference, and aptamers. However, despite great scientific advances over the past decade, and promising in vitro data, several significant challenges continue to limit the translation of this technology to the clinical setting. This review provides a concise update of the current literature.
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Affiliation(s)
- Alexander J V Thompson
- Division of Gastroenterology/Hepatology, Duke Clinical Research Institute, Duke University, Durham, NC 27715, USA
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Romero-López C, Berzal-Herranz A. A long-range RNA-RNA interaction between the 5' and 3' ends of the HCV genome. RNA 2009; 15:1740-52. [PMID: 19605533 DOI: 10.1261/rna.1680809] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The RNA genome of the hepatitis C virus (HCV) contains multiple conserved structural cis domains that direct protein synthesis, replication, and infectivity. The untranslatable regions (UTRs) play essential roles in the HCV cycle. Uncapped viral RNAs are translated via an internal ribosome entry site (IRES) located at the 5' UTR, which acts as a scaffold for recruiting multiple protein factors. Replication of the viral genome is initiated at the 3' UTR. Bioinformatics methods have identified other structural RNA elements thought to be involved in the HCV cycle. The 5BSL3.2 motif, which is embedded in a cruciform structure at the 3' end of the NS5B coding sequence, contributes to the three-dimensional folding of the entire 3' end of the genome. It is essential in the initiation of replication. This paper reports the identification of a novel, strand-specific, long-range RNA-RNA interaction between the 5' and 3' ends of the genome, which involves 5BSL3.2 and IRES motifs. Mutants harboring substitutions in the apical loop of domain IIId or in the internal loop of 5BSL3.2 disrupt the complex, indicating these regions are essential in initiating the kissing interaction. No complex was formed when the UTRs of the related foot and mouth disease virus were used in binding assays, suggesting this interaction is specific for HCV sequences. The present data firmly suggest the existence of a higher-order structure that may mediate a protein-independent circularization of the HCV genome. The 5'-3' end bridge may have a role in viral translation modulation and in the switch from protein synthesis to RNA replication.
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Affiliation(s)
- Cristina Romero-López
- Departamento de Biología Molecular, Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain
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Easton LE, Locker N, Lukavsky PJ. Conserved functional domains and a novel tertiary interaction near the pseudoknot drive translational activity of hepatitis C virus and hepatitis C virus-like internal ribosome entry sites. Nucleic Acids Res 2009; 37:5537-49. [PMID: 19596815 PMCID: PMC2760816 DOI: 10.1093/nar/gkp588] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The translational activity of the hepatitis C virus (HCV) internal ribosome entry site (IRES) and other HCV-like IRES RNAs depends on structured RNA elements in domains II and III, which serve to recruit the ribosomal 40S subunit, eukaryotic initiation factor (eIF) 3 and the ternary eIF2/Met-tRNAiMet/GTP complex and subsequently domain II assists subunit joining. Porcine teschovirus-1 talfan (PTV-1) is a member of the Picornaviridae family, with a predicted HCV-like secondary structure, but only stem-loops IIId and IIIe in the 40S-binding domain display significant sequence conservation with the HCV IRES. Here, we use chemical probing to show that interaction sites with the 40S subunit and eIF3 are conserved between HCV and HCV-like IRESs. In addition, we reveal the functional role of a strictly conserved co-variation between a purine–purine mismatch near the pseudoknot (A–A/G) and the loop sequence of domain IIIe (GAU/CA). These nucleotides are involved in a tertiary interaction, which serves to stabilize the pseudoknot structure and correlates with translational efficiency in both the PTV-1 and HCV IRES. Our data demonstrate conservation of functional domains in HCV and HCV-like IRESs including a more complex structure surrounding the pseudoknot than previously assumed.
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Affiliation(s)
- Laura E Easton
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
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42
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Yasmeen A, Siddiqui AA, Hamid S, Sultana T, Jafri W, Persson MAA. Genetic variations in a well conserved 5'-untranslated region of hepatitis C virus genome isolated in Pakistan. J Virol Methods 2009; 160:38-47. [PMID: 19406160 DOI: 10.1016/j.jviromet.2009.04.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2008] [Revised: 04/13/2009] [Accepted: 04/20/2009] [Indexed: 02/05/2023]
Abstract
The diversity and extent of sequence variations between hepatitis C virus (HCV) isolates from Pakistan were studied and the probable effects of these variations were assessed on secondary viral structures. Sequencing and phylogenetic analysis was performed on 33 samples, of which 25 were typed as genotype 3 by RFLP (restriction fragment length polymorphism) and 8 remained unresolved. Rooted neighbour-joining (NJ) tree revealed that 28 isolates were HCV type 3a and 5 isolates were typed as 3b. The majority of unresolved samples clustered in a different branch of genotype 3, supported by a bootstrap value of 71%. Another, cluster, cluster I, was found to have a bootstrap value of 81%. Genetic distance values showed significant diversity of isolates in these two clusters compared to the reference sequences. Pair-wise comparison showed the presence of additional restriction sites of HaeIII and RsaI in unresolved isolates. In conclusion, unique sequence variability was observed in the 5'-UTR of HCV type 3 isolates from Pakistan. One of the reasons for this sequence variability is the presence of mutations, which are additional restriction sites in the 5'-UTR. These mutations were also responsible for failure of conventional RFLP to type some of the HCV isolates.
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Affiliation(s)
- Anila Yasmeen
- Department of Biological and Biomedical Sciences, Aga Khan University, Karachi, Sindh, Pakistan.
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43
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Gene knockdowns in adult animals: PPMOs and vivo-morpholinos. Molecules 2009; 14:1304-23. [PMID: 19325525 PMCID: PMC6253989 DOI: 10.3390/molecules14031304] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 03/23/2009] [Accepted: 03/24/2009] [Indexed: 11/17/2022] Open
Abstract
Antisense molecules do not readily cross cell membranes. This has limited the use of antisense to systems where techniques have been worked out to introduce the molecules into cells, such as embryos and cell cultures. Uncharged antisense bearing a group of guanidinium moieties on either a linear peptide or dendrimer scaffold can enter cells by endocytosis and subsequently escape from endosomes into the cytosol/nuclear compartment of cells. These technologies allow systemic administration of antisense, making gene knockdowns and splice modification feasible in adult animals; this review presents examples of such animal studies. Techniques developed with PPMOs, which are an arginine-rich cell-penetrating peptide linked to a Morpholino oligo, can also be performed using commercially available Vivo-Morpholinos, which are eight guanidinium groups on a dendrimeric scaffold linked to a Morpholino oligo. Antisense-based techniques such as blocking translation, modifying pre-mRNA splicing, inhibiting miRNA maturation and inhibiting viral replication can be conveniently applied in adult animals by injecting PPMOs or Vivo-Morpholinos.
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44
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Barría MI, González A, Vera-Otarola J, León U, Vollrath V, Marsac D, Monasterio O, Pérez-Acle T, Soza A, López-Lastra M. Analysis of natural variants of the hepatitis C virus internal ribosome entry site reveals that primary sequence plays a key role in cap-independent translation. Nucleic Acids Res 2008; 37:957-71. [PMID: 19106142 PMCID: PMC2647302 DOI: 10.1093/nar/gkn1022] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The HCV internal ribosome entry site (IRES) spans a region of ∼340 nt that encompasses most of the 5′ untranslated region (5′UTR) of the viral mRNA and the first 24–40 nt of the core-coding region. To investigate the implication of altering the primary sequence of the 5′UTR on IRES activity, naturally occurring variants of the 5′UTR were isolated from clinical samples and analyzed. The impact of the identified mutations on translation was evaluated in the context of RLuc/FLuc bicistronic RNAs. Results show that depending on their location within the RNA structure, these naturally occurring mutations cause a range of effects on IRES activity. However, mutations within subdomain IIId hinder HCV IRES-mediated translation. In an attempt to explain these data, the dynamic behavior of the subdomain IIId was analyzed by means of molecular dynamics (MD) simulations. Despite the loss of function, MD simulations predicted that mutant G266A/G268U possesses a structure similar to the wt-RNA. This prediction was validated by analyzing the secondary structure of the isolated IIId RNAs by circular dichroism spectroscopy in the presence or absence of Mg2+ ions. These data strongly suggest that the primary sequence of subdomain IIId plays a key role in HCV IRES-mediated translation.
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Affiliation(s)
- María Inés Barría
- Laboratorio de Virología Molecular, Centro de Investigaciones Médicas, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
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45
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Belsham GJ. Divergent picornavirus IRES elements. Virus Res 2008; 139:183-92. [PMID: 18675861 DOI: 10.1016/j.virusres.2008.07.001] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/25/2008] [Accepted: 07/01/2008] [Indexed: 01/22/2023]
Abstract
Internal ribosome entry site (IRES) elements were first identified about 20 years ago within the 5' untranslated region of picornavirus RNAs. They direct a cap-independent mechanism of translation initiation on the viral RNA. Within the picornavirus family it is now known that there are four classes of IRES element which vary in size (450-270 nt), they also have different, complex, secondary structures and distinct requirements for cellular proteins to allow them to function. This review describes the features of each class of picornavirus IRES element but focuses on the characteristics of the most recently described group, initially identified within the porcine teschovirus-1 RNA, which has strong similarities to the IRES elements from within the genomes of hepatitis C virus and the pestiviruses which are members of the flavivirus family. The selection of the initiation codon by these distinct IRES elements is also discussed.
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Affiliation(s)
- Graham J Belsham
- National Veterinary Institute, Technical University of Denmark, Lindholm, DK-4771 Kalvehave, Denmark.
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Abstract
Morpholino oligonucleotides are stable, uncharged, water-soluble molecules used to block complementary sequences of RNA, preventing processing, read-through, or protein binding at those sites. Morpholinos are typically used to block translation of mRNA and to block splicing of pre-mRNA, though they can block other interactions between biological macromolecules and RNA. Morpholinos are effective, specific, and lack non-antisense effects. They work in any cell that transcribes and translates RNA, but must be delivered into the nuclear/cytosolic compartment to be effective. Morpholinos form stable base pairs with complementary nucleic acid sequences but apparently do not bind to proteins to a significant extent. They are not recognized by any proteins and do not undergo protein-mediated catalysis; nor do they mediate RNA cleavage by RNase H or the RISC complex. This work focuses on techniques and background for using Morpholinos.
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Abstract
Morpholino oligonucleotides are stable, uncharged, water-soluble molecules that bind to complementary sequences of RNA, thereby inhibiting mRNA processing, read-through, and protein binding at those sites. Morpholinos are typically used to inhibit translation of mRNA, splicing of pre-mRNA, and maturation of miRNA, although they can also inhibit other interactions between biological macromolecules and RNA. Morpholinos are effective, specific, and lack non-antisense effects. They work in any cell that transcribes and translates RNA. However, unmodified Morpholinos do not pass well through plasma membranes and must therefore be delivered into the nuclear or cytosolic compartment to be effective. Morpholinos form stable base pairs with complementary nucleic acid sequences but apparently do not bind to proteins to a significant extent. They are not recognized by proteins and do not undergo protein-mediated catalysis; nor do they mediate RNA cleavage by RNase H or the RISC complex. This work focuses on techniques and background for using Morpholinos.
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48
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Lukavsky PJ. Structure and function of HCV IRES domains. Virus Res 2008; 139:166-71. [PMID: 18638512 PMCID: PMC2726286 DOI: 10.1016/j.virusres.2008.06.004] [Citation(s) in RCA: 151] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Accepted: 06/11/2008] [Indexed: 12/16/2022]
Abstract
The HCV IRES is a highly structured RNA which mediates cap-independent translation initiation in higher eukaryotes. This function is encoded in conserved structural motifs in the two major domains of HCV and HCV-like IRESs, which play crucial and distinct roles along the initiation pathway. In this review, I discuss structural features of IRES domains and how these RNA motifs function as RNA-based initiation factors to form 48S initiation complexes and 80S ribosomes with only a subset of canonical, protein-based eukaryotic initiation factors.
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Affiliation(s)
- Peter J Lukavsky
- Laboratory of Molecular Biology, MRC, Hills Road, Cambridge CB2 0QH, UK.
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49
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Moulton HM, Moulton JD. Antisense Morpholino Oligomers and Their Peptide Conjugates. THERAPEUTIC OLIGONUCLEOTIDES 2008. [DOI: 10.1039/9781847558275-00043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Hong M. Moulton
- AVI BioPharma Inc. 4575 SW Research Way Corvallis OR 97333 USA
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50
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Abstract
Since the discovery of the hepatitis C virus (HCV) as the major cause of non-A, non-B hepatitis in 1989, the search for specific targeted antiviral therapy for HCV (STAT-C) has been underway. Recently, major advances in the understanding of HCV biology and the development of an in vitro system of HCV replication have contributed to the selection of multiple candidate drugs for the treatment of hepatitis C. In 2006, five such candidate drugs have entered phase II clinical trials in patients chronically infected with hepatitis C, including small molecule inhibitors of the HCV NS3 serine protease and NS5B RNA-dependent RNA polymerase. This review focuses on hepatitis C protease and polymerase inhibitors that have progressed to phase II clinical development, foreshadowing the era of STAT-Cs.
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Affiliation(s)
- Mark S Sulkowski
- Johns Hopkins University School of Medicine, 600 North Wolfe Street, 1830 Building, Room 448, Baltimore, MD 21287, USA.
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