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Brito Querido J, Sokabe M, Díaz-López I, Gordiyenko Y, Fraser CS, Ramakrishnan V. The structure of a human translation initiation complex reveals two independent roles for the helicase eIF4A. Nat Struct Mol Biol 2024; 31:455-464. [PMID: 38287194 PMCID: PMC10948362 DOI: 10.1038/s41594-023-01196-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 11/30/2023] [Indexed: 01/31/2024]
Abstract
Eukaryotic translation initiation involves recruitment of the 43S pre-initiation complex to the 5' end of mRNA by the cap-binding complex eIF4F, forming the 48S translation initiation complex (48S), which then scans along the mRNA until the start codon is recognized. We have previously shown that eIF4F binds near the mRNA exit channel of the 43S, leaving open the question of how mRNA secondary structure is removed as it enters the mRNA channel on the other side of the 40S subunit. Here we report the structure of a human 48S that shows that, in addition to the eIF4A that is part of eIF4F, there is a second eIF4A helicase bound at the mRNA entry site, which could unwind RNA secondary structures as they enter the 48S. The structure also reveals conserved interactions between eIF4F and the 43S, probaby explaining how eIF4F can promote mRNA recruitment in all eukaryotes.
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Affiliation(s)
- Jailson Brito Querido
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Department of Biological Chemistry and Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA
| | | | | | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA.
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Wang X, Zhu J, Zhang D, Liu G. Ribosomal control in RNA virus-infected cells. Front Microbiol 2022; 13:1026887. [PMID: 36419416 PMCID: PMC9677555 DOI: 10.3389/fmicb.2022.1026887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 10/19/2022] [Indexed: 11/09/2022] Open
Abstract
Viruses are strictly intracellular parasites requiring host cellular functions to complete their reproduction cycle involving virus infection of host cell, viral genome replication, viral protein translation, and virion release. Ribosomes are protein synthesis factories in cells, and viruses need to manipulate ribosomes to complete their protein synthesis. Viruses use translation initiation factors through their own RNA structures or cap structures, thereby inducing ribosomes to synthesize viral proteins. Viruses also affect ribosome production and the assembly of mature ribosomes, and regulate the recognition of mRNA by ribosomes, thereby promoting viral protein synthesis and inhibiting the synthesis of host antiviral immune proteins. Here, we review the remarkable mechanisms used by RNA viruses to regulate ribosomes, in particular, the mechanisms by which RNA viruses induce the formation of specific heterogeneous ribosomes required for viral protein translation. This review provides valuable insights into the control of viral infection and diseases from the perspective of viral protein synthesis.
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Brito Querido J, Sokabe M, Kraatz S, Gordiyenko Y, Skehel JM, Fraser CS, Ramakrishnan V. Structure of a human 48 S translational initiation complex. Science 2020; 369:1220-1227. [PMID: 32883864 DOI: 10.1126/science.aba4904] [Citation(s) in RCA: 110] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 07/07/2020] [Indexed: 12/20/2022]
Abstract
A key step in translational initiation is the recruitment of the 43S preinitiation complex by the cap-binding complex [eukaryotic initiation factor 4F (eIF4F)] at the 5' end of messenger RNA (mRNA) to form the 48S initiation complex (i.e., the 48S). The 48S then scans along the mRNA to locate a start codon. To understand the mechanisms involved, we used cryo-electron microscopy to determine the structure of a reconstituted human 48S The structure reveals insights into early events of translation initiation complex assembly, as well as how eIF4F interacts with subunits of eIF3 near the mRNA exit channel in the 43S The location of eIF4F is consistent with a slotting model of mRNA recruitment and suggests that downstream mRNA is unwound at least in part by being "pulled" through the 40S subunit during scanning.
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Affiliation(s)
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA
| | | | | | | | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA.
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Madden EA, Plante KS, Morrison CR, Kutchko KM, Sanders W, Long KM, Taft-Benz S, Cruz Cisneros MC, White AM, Sarkar S, Reynolds G, Vincent HA, Laederach A, Moorman NJ, Heise MT. Using SHAPE-MaP To Model RNA Secondary Structure and Identify 3'UTR Variation in Chikungunya Virus. J Virol 2020; 94:e00701-20. [PMID: 32999019 PMCID: PMC7925192 DOI: 10.1128/jvi.00701-20] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 09/17/2020] [Indexed: 01/04/2023] Open
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus associated with debilitating arthralgia in humans. RNA secondary structure in the viral genome plays an important role in the lifecycle of alphaviruses; however, the specific role of RNA structure in regulating CHIKV replication is poorly understood. Our previous studies found little conservation in RNA secondary structure between alphaviruses, and this structural divergence creates unique functional structures in specific alphavirus genomes. Therefore, to understand the impact of RNA structure on CHIKV biology, we used SHAPE-MaP to inform the modeling of RNA secondary structure throughout the genome of a CHIKV isolate from the 2013 Caribbean outbreak. We then analyzed regions of the genome with high levels of structural specificity to identify potentially functional RNA secondary structures and identified 23 regions within the CHIKV genome with higher than average structural stability, including four previously identified, functionally important CHIKV RNA structures. We also analyzed the RNA flexibility and secondary structures of multiple 3'UTR variants of CHIKV that are known to affect virus replication in mosquito cells. This analysis found several novel RNA structures within these 3'UTR variants. A duplication in the 3'UTR that enhances viral replication in mosquito cells led to an overall increase in the amount of unstructured RNA in the 3'UTR. This analysis demonstrates that the CHIKV genome contains a number of unique, specific RNA secondary structures and provides a strategy for testing these secondary structures for functional importance in CHIKV replication and pathogenesis.IMPORTANCE Chikungunya virus (CHIKV) is a mosquito-borne RNA virus that causes febrile illness and debilitating arthralgia in humans. CHIKV causes explosive outbreaks but there are no approved therapies to treat or prevent CHIKV infection. The CHIKV genome contains functional RNA secondary structures that are essential for proper virus replication. Since RNA secondary structures have only been defined for a small portion of the CHIKV genome, we used a chemical probing method to define the RNA secondary structures of CHIKV genomic RNA. We identified 23 highly specific structured regions of the genome, and confirmed the functional importance of one structure using mutagenesis. Furthermore, we defined the RNA secondary structure of three CHIKV 3'UTR variants that differ in their ability to replicate in mosquito cells. Our study highlights the complexity of the CHIKV genome and describes new systems for designing compensatory mutations to test the functional relevance of viral RNA secondary structures.
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Affiliation(s)
- Emily A Madden
- Department of Microbiology and Immunology, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Kenneth S Plante
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Clayton R Morrison
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Katrina M Kutchko
- Biology Department, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
- Curriculum in Bioinformatics and Computational Biology, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Wes Sanders
- Department of Microbiology and Immunology, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Kristin M Long
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Sharon Taft-Benz
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | | | | | - Sanjay Sarkar
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Grace Reynolds
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Heather A Vincent
- Department of Microbiology and Immunology, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Alain Laederach
- Biology Department, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Nathanial J Moorman
- Department of Microbiology and Immunology, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
- Lineberger Comprehensive Cancer Center, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
| | - Mark T Heise
- Department of Microbiology and Immunology, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
- Department of Genetics, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
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Díaz-López I, Toribio R, Berlanga JJ, Ventoso I. An mRNA-binding channel in the ES6S region of the translation 48S-PIC promotes RNA unwinding and scanning. eLife 2019; 8:48246. [PMID: 31789591 PMCID: PMC6887119 DOI: 10.7554/elife.48246] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 11/16/2019] [Indexed: 11/30/2022] Open
Abstract
Loading of mRNA onto the ribosomal 43S pre-initiation complex (PIC) and its subsequent scanning require the removal of the secondary structure of the by RNA helicases such as eIF4A. However, the topology and mechanics of the scanning complex bound to mRNA (48S-PIC) and the influence of its solvent-side composition on the scanning process are poorly known. Here, we found that the ES6S region of the 48S-PIC constitutes an extended binding channel for eIF4A-mediated unwinding of mRNA and scanning. Blocking ES6S inhibited the cap-dependent translation of mRNAs that have structured 5′ UTRs (including G-quadruplexes), many of which are involved in signal transduction and growth, but it did not affect IRES-driven translation. Genome-wide analysis of mRNA translation revealed a great diversity in ES6S-mediated scanning dependency. Our data suggest that mRNA threading into the ES6S region makes scanning by 48S PIC slower but more processive. Hence, we propose a topological and functional model of the scanning 48S-PIC.
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Affiliation(s)
- Irene Díaz-López
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Departamento de Biología Molecular, Universidad Autónoma de Madrid (UAM), Madrid, Spain
| | - René Toribio
- Centro de Biotecnología y Genómica de Plantas, Madrid, Spain
| | - Juan José Berlanga
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Departamento de Biología Molecular, Universidad Autónoma de Madrid (UAM), Madrid, Spain
| | - Iván Ventoso
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Departamento de Biología Molecular, Universidad Autónoma de Madrid (UAM), Madrid, Spain
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Stern-Ginossar N, Thompson SR, Mathews MB, Mohr I. Translational Control in Virus-Infected Cells. Cold Spring Harb Perspect Biol 2019; 11:a033001. [PMID: 29891561 PMCID: PMC6396331 DOI: 10.1101/cshperspect.a033001] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
As obligate intracellular parasites, virus reproduction requires host cell functions. Despite variations in genome size and configuration, nucleic acid composition, and their repertoire of encoded functions, all viruses remain unconditionally dependent on the protein synthesis machinery resident within their cellular hosts to translate viral messenger RNAs (mRNAs). A complex signaling network responsive to physiological stress, including infection, regulates host translation factors and ribosome availability. Furthermore, access to the translation apparatus is patrolled by powerful host immune defenses programmed to restrict viral invaders. Here, we review the tactics and mechanisms used by viruses to appropriate control over host ribosomes, subvert host defenses, and dominate the infected cell translational landscape. These not only define aspects of infection biology paramount for virus reproduction, but continue to drive fundamental discoveries into how cellular protein synthesis is controlled in health and disease.
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Affiliation(s)
- Noam Stern-Ginossar
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sunnie R Thompson
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Michael B Mathews
- Department of Medicine, Rutgers New Jersey Medical School, Newark, New Jersey 07103
| | - Ian Mohr
- Department of Microbiology, New York University School of Medicine, New York, New York 10016
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Henss L, Scholz T, Grünweller A, Schnierle BS. Silvestrol Inhibits Chikungunya Virus Replication. Viruses 2018; 10:v10110592. [PMID: 30380742 PMCID: PMC6266838 DOI: 10.3390/v10110592] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 10/19/2018] [Accepted: 10/26/2018] [Indexed: 02/08/2023] Open
Abstract
Silvestrol, a natural compound that is isolated from plants of the genus Aglaia, is a specific inhibitor of the RNA helicase eIF4A, which unwinds RNA secondary structures in 5′-untranslated regions (UTRs) of mRNAs and allows translation. Silvestrol has a broad antiviral activity against multiple RNA virus families. Here, we show that silvestrol inhibits the replication of chikungunya virus (CHIKV), a positive single-stranded RNA virus. Silvestrol delayed the protein synthesis of non-structural (nsPs) and structural proteins, resulting in a delayed innate response to CHIKV infection. Interferon-α induced STAT1 phosphorylation was not inhibited nor did eIF2α become phosphorylated 16 h post infection in the presence of silvestrol. In addition, the host protein shut-off induced by CHIKV infection was decreased in silvestrol-treated cells. Silvestrol acts by limiting the amount of nsPs, and thereby reducing CHIKV RNA replication. From our results, we propose that inhibition of the host helicase eIF4A might have potential as a therapeutic strategy to treat CHIKV infections.
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Affiliation(s)
- Lisa Henss
- Paul-Ehrlich-Institut, Department of Virology, 63225 Langen, Germany.
| | - Tatjana Scholz
- Paul-Ehrlich-Institut, Department of Virology, 63225 Langen, Germany.
| | - Arnold Grünweller
- Institut für Pharmazeutische Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany.
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