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Padget RL, Zeitz MJ, Blair GA, Wu X, North MD, Tanenbaum MT, Stanley KE, Phillips CM, King DR, Lamouille S, Gourdie RG, Hoeker GS, Swanger SA, Poelzing S, Smyth JW. Acute Adenoviral Infection Elicits an Arrhythmogenic Substrate Prior to Myocarditis. Circ Res 2024; 134:892-912. [PMID: 38415360 PMCID: PMC11003857 DOI: 10.1161/circresaha.122.322437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 02/12/2024] [Indexed: 02/29/2024]
Abstract
BACKGROUND Viral cardiac infection represents a significant clinical challenge encompassing several etiological agents, disease stages, complex presentation, and a resulting lack of mechanistic understanding. Myocarditis is a major cause of sudden cardiac death in young adults, where current knowledge in the field is dominated by later disease phases and pathological immune responses. However, little is known regarding how infection can acutely induce an arrhythmogenic substrate before significant immune responses. Adenovirus is a leading cause of myocarditis, but due to species specificity, models of infection are lacking, and it is not understood how adenoviral infection may underlie sudden cardiac arrest. Mouse adenovirus type-3 was previously reported as cardiotropic, yet it has not been utilized to understand the mechanisms of cardiac infection and pathology. METHODS We have developed mouse adenovirus type-3 infection as a model to investigate acute cardiac infection and molecular alterations to the infected heart before an appreciable immune response or gross cardiomyopathy. RESULTS Optical mapping of infected hearts exposes decreases in conduction velocity concomitant with increased Cx43Ser368 phosphorylation, a residue known to regulate gap junction function. Hearts from animals harboring a phospho-null mutation at Cx43Ser368 are protected against mouse adenovirus type-3-induced conduction velocity slowing. Additional to gap junction alterations, patch clamping of mouse adenovirus type-3-infected adult mouse ventricular cardiomyocytes reveals prolonged action potential duration as a result of decreased IK1 and IKs current density. Turning to human systems, we find human adenovirus type-5 increases phosphorylation of Cx43Ser368 and disrupts synchrony in human induced pluripotent stem cell-derived cardiomyocytes, indicating common mechanisms with our mouse whole heart and adult cardiomyocyte data. CONCLUSIONS Together, these findings demonstrate that adenoviral infection creates an arrhythmogenic substrate through direct targeting of gap junction and ion channel function in the heart. Such alterations are known to precipitate arrhythmias and likely contribute to sudden cardiac death in acutely infected patients.
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Affiliation(s)
- Rachel L. Padget
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA 24061, USA
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Michael J. Zeitz
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Grace A. Blair
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA 24061, USA
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Xiaobo Wu
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Michael D. North
- Virginia Tech Carilion School of Medicine, Roanoke, VA 24016, USA
| | | | - Kari E. Stanley
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA 24061, USA
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Chelsea M. Phillips
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - D. Ryan King
- Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA 24061, USA
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Samy Lamouille
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA 24016, USA
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
| | - Robert G. Gourdie
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA 24016, USA
- Department of Biomedical Engineering and Mechanics, College of Engineering, Virginia Tech, Blacksburg, VA 24061, USA
| | - Gregory S. Hoeker
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
| | - Sharon A. Swanger
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA 24016, USA
- Department of Biomedical Sciences and Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA
| | - Steven Poelzing
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA 24016, USA
- Department of Biomedical Engineering and Mechanics, College of Engineering, Virginia Tech, Blacksburg, VA 24061, USA
| | - James W. Smyth
- Fralin Biomedical Research Institute at Virginia Tech Carilion, Roanoke, VA 24016, USA
- Center for Vascular and Heart Research, FBRI at VTC, Roanoke, VA 24016, USA
- Virginia Tech Carilion School of Medicine, Roanoke, VA 24016, USA
- Department of Biomedical Engineering and Mechanics, College of Engineering, Virginia Tech, Blacksburg, VA 24061, USA
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, USA
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Monsion B, Mohd Jaafar F, Mertens PPC, Attoui H. Uncovering the Underlying Mechanisms Blocking Replication of Bluetongue Virus Serotype 26 (BTV-26) in Culicoides Cells. Biomolecules 2023; 13:878. [PMID: 37371457 DOI: 10.3390/biom13060878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 05/05/2023] [Accepted: 05/18/2023] [Indexed: 06/29/2023] Open
Abstract
At least 12 serotypes of 'atypical' bluetongue virus (BTV-25 to BTV-36) have been identified to date. These atypical serotypes fail to infect/replicate in Culicoides-derived cell lines and/or adult Culicoides vectors and hence can no longer be transmitted by these vectors. They appear to be horizontally transmitted from infected to in-contact ruminants, although the route(s) of infection remain to be identified. Viral genome segments 1, 2 and 3 (Seg-1, Seg2 and Seg-3) of BTV-26 were identified as involved in blocking virus replication in KC cells. We have developed Culicoides-specific expression plasmids, which we used in transfected insect cells to assess the stability of viral mRNAs and protein expression from full-length open reading frames of Seg-1, -2 and -3 of BTV-1 (a Culicoides-vectored BTV) or BTV-26. Our results indicate that the blocked replication of BTV-26 in KC cells is not due to an RNAi response, which would lead to rapid degradation of viral mRNAs. A combination of degradation/poor expression and/or modification of the proteins encoded by these segments appears to drive the failure of BTV-26 core/whole virus-particles to assemble and replicate effectively in Culicoides cells.
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Affiliation(s)
- Baptiste Monsion
- UMR1161 VIROLOGIE, INRAE, Ecole Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, F-94700 Maisons-Alfort, France
| | - Fauziah Mohd Jaafar
- UMR1161 VIROLOGIE, INRAE, Ecole Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, F-94700 Maisons-Alfort, France
| | - Peter P C Mertens
- One Virology, The Wolfson Centre for Global Virus Research, School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, Leicestershire, UK
| | - Houssam Attoui
- UMR1161 VIROLOGIE, INRAE, Ecole Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, F-94700 Maisons-Alfort, France
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3
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Fragile X-Related Protein FXR1 Controls Human Adenovirus Capsid mRNA Metabolism. J Virol 2023; 97:e0153922. [PMID: 36749074 PMCID: PMC9972981 DOI: 10.1128/jvi.01539-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Human adenoviruses (HAdVs) are widespread pathogens causing a variety of diseases. A well-controlled expression of virus capsid mRNAs originating from the major late transcription unit (MLTU) is essential for forming the infectious virus progeny. However, regulation of the MLTU mRNA metabolism has mainly remained enigmatic. In this study, we show that the cellular RNA-binding protein FXR1 controls the stability of the HAdV-5 MLTU mRNAs, as depletion of FXR1 resulted in increased steady-state levels of MLTU mRNAs. Surprisingly, the lack of FXR1 reduced viral capsid protein accumulation and formation of the infectious virus progeny, indicating an opposing function of FXR1 in HAdV-5 infection. Further, the long FXR1 isoform interfered with MLTU mRNA translation, suggesting FXR1 isoform-specific functions in virus-infected cells. We also show that the FXR1 protein interacts with N6-methyladenosine (m6A)-modified MLTU mRNAs, thereby acting as a novel m6A reader protein in HAdV-5 infected cells. Collectively, our study identifies FXR1 as a regulator of MLTU mRNA metabolism in the lytic HAdV-5 life cycle. IMPORTANCE Human adenoviruses (HAdVs) are common pathogens causing various self-limiting diseases, such as the common cold and conjunctivitis. Even though adenoviruses have been studied for more than 6 decades, there are still gaps in understanding how the virus interferes with the host cell to achieve efficient growth. In this study, we identified the cellular RNA-binding protein FXR1 as a factor manipulating the HAdV life cycle. We show that the FXR1 protein specifically interferes with mRNAs encoding essential viral capsid proteins. Since the lack of the FXR1 protein reduces virus growth, we propose that FXR1 can be considered a novel cellular proviral factor needed for efficient HAdV growth. Collectively, our study provides new detailed insights about the HAdV-host interactions, which might be helpful when developing countermeasures against pathogenic adenovirus infections and for improving adenovirus-based therapies.
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Bi-directional ribosome scanning controls the stringency of start codon selection. Nat Commun 2021; 12:6604. [PMID: 34782646 PMCID: PMC8593136 DOI: 10.1038/s41467-021-26923-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 10/28/2021] [Indexed: 11/29/2022] Open
Abstract
The fidelity of start codon recognition by ribosomes is paramount during protein synthesis. The current knowledge of eukaryotic translation initiation implies unidirectional 5'→3' migration of the pre-initiation complex (PIC) along the 5' UTR. In probing translation initiation from ultra-short 5' UTR, we report that an AUG triplet near the 5' end can be selected via PIC backsliding. Bi-directional ribosome scanning is supported by competitive selection of closely spaced AUG codons and recognition of two initiation sites flanking an internal ribosome entry site. Transcriptome-wide PIC profiling reveals footprints with an oscillation pattern near the 5' end and start codons. Depleting the RNA helicase eIF4A leads to reduced PIC oscillations and impaired selection of 5' end start codons. Enhancing the ATPase activity of eIF4A promotes nonlinear PIC scanning and stimulates upstream translation initiation. The helicase-mediated PIC conformational switch may provide an operational mechanism that unifies ribosome recruitment, scanning, and start codon selection.
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Igarashi K, Kashiwagi K. Functional roles of polyamines and their metabolite acrolein in eukaryotic cells. Amino Acids 2021; 53:1473-1492. [PMID: 34546444 DOI: 10.1007/s00726-021-03073-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 08/24/2021] [Indexed: 12/26/2022]
Abstract
Among low molecular weight substances, polyamines (spermidine, spermine and their precursor putrescine) are present in eukaryotic cells at the mM level together with ATP and glutathione. It is expected therefore that polyamines play important roles in cell proliferation and viability. Polyamines mainly exist as a polyamine-RNA complex and regulate protein synthesis. It was found that polyamines enhance translation from inefficient mRNAs. The detailed mechanisms of polyamine stimulation of specific kinds of protein syntheses and the physiological functions of these proteins are described in this review. Spermine is metabolized into acrolein (CH2 = CH-CHO) and hydrogen peroxide (H2O2) by spermine oxidase. Although it is thought that cell damage is mainly caused by reactive oxygen species (O2-, H2O2, and •OH), it was found that acrolein is much more toxic than H2O2. Accordingly, the level of acrolein produced becomes a useful biomarker for several tissue-damage diseases like brain stroke. Thus, the mechanisms of cell toxicity caused by acrolein are described in this review.
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Affiliation(s)
- Kazuei Igarashi
- Amine Pharma Research Institute, Innovation Plaza at Chiba University, 1-8-15 Inohana, Chuo-ku, Chiba, Chiba, 260-0856, Japan.
- Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, Chiba, 260-8675, Japan.
| | - Keiko Kashiwagi
- Faculty of Pharmacy, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba, 288-0025, Japan
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Tickner ZJ, Farzan M. Riboswitches for Controlled Expression of Therapeutic Transgenes Delivered by Adeno-Associated Viral Vectors. Pharmaceuticals (Basel) 2021; 14:ph14060554. [PMID: 34200913 PMCID: PMC8230432 DOI: 10.3390/ph14060554] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 05/28/2021] [Accepted: 06/04/2021] [Indexed: 11/16/2022] Open
Abstract
Vectors developed from adeno-associated virus (AAV) are powerful tools for in vivo transgene delivery in both humans and animal models, and several AAV-delivered gene therapies are currently approved for clinical use. However, AAV-mediated gene therapy still faces several challenges, including limited vector packaging capacity and the need for a safe, effective method for controlling transgene expression during and after delivery. Riboswitches, RNA elements which control gene expression in response to ligand binding, are attractive candidates for regulating expression of AAV-delivered transgene therapeutics because of their small genomic footprints and non-immunogenicity compared to protein-based expression control systems. In addition, the ligand-sensing aptamer domains of many riboswitches can be exchanged in a modular fashion to allow regulation by a variety of small molecules, proteins, and oligonucleotides. Riboswitches have been used to regulate AAV-delivered transgene therapeutics in animal models, and recently developed screening and selection methods allow rapid isolation of riboswitches with novel ligands and improved performance in mammalian cells. This review discusses the advantages of riboswitches in the context of AAV-delivered gene therapy, the subsets of riboswitch mechanisms which have been shown to function in human cells and animal models, recent progress in riboswitch isolation and optimization, and several examples of AAV-delivered therapeutic systems which might be improved by riboswitch regulation.
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Affiliation(s)
- Zachary J. Tickner
- Department of Immunology and Microbiology, the Scripps Research Institute, Jupiter, FL 33458, USA;
- Correspondence:
| | - Michael Farzan
- Department of Immunology and Microbiology, the Scripps Research Institute, Jupiter, FL 33458, USA;
- Emmune, Inc., Jupiter, FL 33458, USA
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7
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Unconventional viral gene expression mechanisms as therapeutic targets. Nature 2021; 593:362-371. [PMID: 34012080 DOI: 10.1038/s41586-021-03511-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 03/22/2021] [Indexed: 12/14/2022]
Abstract
Unlike the human genome that comprises mostly noncoding and regulatory sequences, viruses have evolved under the constraints of maintaining a small genome size while expanding the efficiency of their coding and regulatory sequences. As a result, viruses use strategies of transcription and translation in which one or more of the steps in the conventional gene-protein production line are altered. These alternative strategies of viral gene expression (also known as gene recoding) can be uniquely brought about by dedicated viral enzymes or by co-opting host factors (known as host dependencies). Targeting these unique enzymatic activities and host factors exposes vulnerabilities of a virus and provides a paradigm for the design of novel antiviral therapies. In this Review, we describe the types and mechanisms of unconventional gene and protein expression in viruses, and provide a perspective on how future basic mechanistic work could inform translational efforts that are aimed at viral eradication.
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Sakamoto A, Terui Y, Uemura T, Igarashi K, Kashiwagi K. Translational Regulation of Clock Genes BMAL1 and REV-ERBα by Polyamines. Int J Mol Sci 2021; 22:1307. [PMID: 33525630 PMCID: PMC7865260 DOI: 10.3390/ijms22031307] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 01/26/2021] [Indexed: 11/16/2022] Open
Abstract
Polyamines stimulate the synthesis of specific proteins at the level of translation, and the genes encoding these proteins are termed as the "polyamine modulon". The circadian clock generates daily rhythms in mammalian physiology and behavior. We investigated the role of polyamines in the circadian rhythm using control and polyamine-reduced NIH3T3 cells. The intracellular polyamines exhibited a rhythm with a period of about 24 h. In the polyamine-reduced NIH3T3 cells, the circadian period of circadian clock genes was lengthened and the synthesis of BMAL1 and REV-ERBα was significantly reduced at the translation level. Thus, the mechanism of polyamine stimulation of these protein syntheses was analyzed using NIH3T3 cells transiently transfected with genes encoding enhanced green fluorescent protein (EGFP) fusion mRNA with normal or mutated 5'-untranslated region (5'-UTR) of Bmal1 or Rev-erbα mRNA. It was found that polyamines stimulated BMAL1 and REV-ERBα synthesis through the enhancement of ribosomal shunting during the ribosome shunting within the 5'-UTR of mRNAs. Accordingly, the genes encoding Bmal1 and Rev-erbα were identified as the members of "polyamine modulon", and these two proteins are significantly involved in the circadian rhythm control.
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Affiliation(s)
- Akihiko Sakamoto
- Faculty of Pharmacy, Chiba Institute of Science, Choshi, Chiba 288-0025, Japan; (A.S.); (Y.T.)
| | - Yusuke Terui
- Faculty of Pharmacy, Chiba Institute of Science, Choshi, Chiba 288-0025, Japan; (A.S.); (Y.T.)
| | - Takeshi Uemura
- Amine Pharma Research Institute, Innovation Plaza at Chiba University, Chiba 260-0856, Japan; (T.U.); (K.I.)
- Graduate School of Pharmaceutical Science, Chiba University, Chiba 260-8675, Japan
| | - Kazuei Igarashi
- Amine Pharma Research Institute, Innovation Plaza at Chiba University, Chiba 260-0856, Japan; (T.U.); (K.I.)
- Graduate School of Pharmaceutical Science, Chiba University, Chiba 260-8675, Japan
| | - Keiko Kashiwagi
- Faculty of Pharmacy, Chiba Institute of Science, Choshi, Chiba 288-0025, Japan; (A.S.); (Y.T.)
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Donovan-Banfield I, Turnell AS, Hiscox JA, Leppard KN, Matthews DA. Deep splicing plasticity of the human adenovirus type 5 transcriptome drives virus evolution. Commun Biol 2020; 3:124. [PMID: 32170151 PMCID: PMC7070027 DOI: 10.1038/s42003-020-0849-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 02/12/2020] [Indexed: 02/06/2023] Open
Abstract
Viral genomes have high gene densities and complex transcription strategies rendering transcriptome analysis through short-read RNA-seq approaches problematic. Adenovirus transcription and splicing is especially complex. We used long-read direct RNA sequencing to study adenovirus transcription and splicing during infection. This revealed a previously unappreciated complexity of alternative splicing and potential for secondary initiating codon usage. Moreover, we find that most viral transcripts tend to shorten polyadenylation lengths as infection progresses. Development of an open reading frame centric bioinformatics analysis pipeline provided a deeper quantitative and qualitative understanding of adenovirus's genetic potential. Across the viral genome adenovirus makes multiple distinctly spliced transcripts that code for the same protein. Over 11,000 different splicing patterns were recorded across the viral genome, most occurring at low levels. This low-level use of alternative splicing patterns potentially enables the virus to maximise its coding potential over evolutionary timescales.
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Affiliation(s)
- I'ah Donovan-Banfield
- Department of Cellular and Molecular Medicine, School of Medical Sciences University Walk, University of Bristol, Bristol, BS8 1TD, UK
| | - Andrew S Turnell
- Institute of Cancer and Genomic Sciences College of Medical and Dental Sciences University of Birmingham Edgbaston, Birmingham, B15 2TT, UK
| | - Julian A Hiscox
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, ic2 Building, Liverpool, L3 5RF, UK
| | - Keith N Leppard
- Life Sciences University of Warwick Coventry, Coventry, CV4 7AL, UK
| | - David A Matthews
- Department of Cellular and Molecular Medicine, School of Medical Sciences University Walk, University of Bristol, Bristol, BS8 1TD, UK.
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Nemerow G, Flint J. Lessons learned from adenovirus (1970-2019). FEBS Lett 2019; 593:3395-3418. [PMID: 31777951 DOI: 10.1002/1873-3468.13700] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/24/2019] [Accepted: 11/24/2019] [Indexed: 12/11/2022]
Abstract
Animal viruses are well recognized for their ability to uncover fundamental cell and molecular processes, and adenovirus certainly provides a prime example. This review illustrates the lessons learned from studying adenovirus over the past five decades. We take a look back at the key studies of adenovirus structure and biophysical properties, which revealed the mechanisms of adenovirus association with antibody, cell receptor, and immune molecules that regulate infection. In addition, we discuss the critical contribution of studies of adenovirus gene expression to elucidation of fundamental reactions in pre-mRNA processing and its regulation. Other pioneering studies furnished the first examples of protein-primed initiation of DNA synthesis and viral small RNAs. As a nonenveloped virus, adenoviruses have furnished insights into the modes of virus attachment, entry, and penetration of host cells, and we discuss the diversity of cell receptors that support these processes, as well as membrane penetration. As a result of these extensive studies, adenovirus vectors were among the first to be developed for therapeutic applications. We highlight some of the early (unsuccessful) trials and the lessons learned from them.
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Affiliation(s)
- Glen Nemerow
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA, USA
| | - Jane Flint
- Department of Molecular Biology, Princeton University, NJ, USA
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Lacerda R, Menezes J, Candeias MM. Alternative Mechanisms of mRNA Translation Initiation in Cellular Stress Response and Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1157:117-132. [PMID: 31342440 DOI: 10.1007/978-3-030-19966-1_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Throughout evolution, eukaryotic cells have devised different mechanisms to cope with stressful environments. When eukaryotic cells are exposed to stress stimuli, they activate adaptive pathways that allow them to restore cellular homeostasis. Most types of stress stimuli have been reported to induce a decrease in overall protein synthesis accompanied by induction of alternative mechanisms of mRNA translation initiation. Here, we present well-studied and recent examples of such stress responses and the alternative translation initiation mechanisms they induce, and discuss the consequences of such regulation for cell homeostasis and oncogenic transformation.
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Affiliation(s)
- Rafaela Lacerda
- Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge, Lisboa, Portugal.,Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, University of Lisbon, Lisboa, Portugal
| | - Juliane Menezes
- Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge, Lisboa, Portugal.,Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, University of Lisbon, Lisboa, Portugal
| | - Marco M Candeias
- Department of Human Genetics, National Institute of Health Doutor Ricardo Jorge, Lisboa, Portugal. .,MaRCU - Molecular and RNA Cancer Unit, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
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12
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Smirnova VV, Shestakova ED, Bikmetov DV, Chugunova AA, Osterman IA, Serebryakova MV, Sergeeva OV, Zatsepin TS, Shatsky IN, Terenin IM. eIF4G2 balances its own mRNA translation via a PCBP2-based feedback loop. RNA (NEW YORK, N.Y.) 2019; 25:757-767. [PMID: 31010886 PMCID: PMC6573783 DOI: 10.1261/rna.065623.118] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 03/18/2019] [Indexed: 06/09/2023]
Abstract
Poly(rC)-binding protein 2 (PCBP2, hnRNP E2) is one of the most abundant RNA-binding proteins in mammalian cells. In humans, it exists in seven isoforms, which are assumed to play similar roles in cells. The protein is shown to bind 3'-untranslated regions (3'-UTRs) of many mRNAs and regulate their translation and/or stability, but nothing is known about the functional consequences of PCBP2 binding to 5'-UTRs. Here we show that the PCBP2 isoform f interacts with the 5'-UTRs of mRNAs encoding eIF4G2 (a translation initiation factor with a yet unknown mechanism of action, also known as DAP5) and Cyclin I, and inhibits their translation in vitro and in cultured cells, while the PCBP2 isoform e only affects Cyclin I translation. Furthermore, eIF4G2 participates in a cap-dependent translation of the PCBP2 mRNA. Thus, PCBP2 and eIF4G2 seem to regulate one another's expression via a novel type of feedback loop formed by the translation initiation factor and the RNA-binding protein.
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Affiliation(s)
- Victoria V Smirnova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Leninskie Gory, 119234 Moscow, Russia
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
| | - Ekaterina D Shestakova
- Department of Biochemistry, School of Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow, 119234, Russian Federation
| | - Dmitry V Bikmetov
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Leninskie Gory, 119234 Moscow, Russia
| | - Anastasia A Chugunova
- Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow Region 143026, Russia
| | - Ilya A Osterman
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
- Chemistry Department, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow Region 143026, Russia
| | - Marina V Serebryakova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
| | - Olga V Sergeeva
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow Region 143026, Russia
| | - Timofey S Zatsepin
- Skolkovo Institute of Science and Technology, Skolkovo, Moscow Region 143026, Russia
| | - Ivan N Shatsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
| | - Ilya M Terenin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119992, Russia
- Sechenov First Moscow State Medical University, Institute of Molecular Medicine, 119991, Moscow, Russian Federation
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13
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Li S. Regulation of Ribosomal Proteins on Viral Infection. Cells 2019; 8:E508. [PMID: 31137833 PMCID: PMC6562653 DOI: 10.3390/cells8050508] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Revised: 05/17/2019] [Accepted: 05/21/2019] [Indexed: 12/20/2022] Open
Abstract
Ribosomal proteins (RPs), in conjunction with rRNA, are major components of ribosomes involved in the cellular process of protein biosynthesis, known as "translation". The viruses, as the small infectious pathogens with limited genomes, must recruit a variety of host factors to survive and propagate, including RPs. At present, more and more information is available on the functional relationship between RPs and virus infection. This review focuses on advancements in my own understanding of critical roles of RPs in the life cycle of viruses. Various RPs interact with viral mRNA and proteins to participate in viral protein biosynthesis and regulate the replication and infection of virus in host cells. Most interactions are essential for viral translation and replication, which promote viral infection and accumulation, whereas the minority represents the defense signaling of host cells by activating immune pathway against virus. RPs provide a new platform for antiviral therapy development, however, at present, antiviral therapeutics with RPs involving in virus infection as targets is limited, and exploring antiviral strategy based on RPs will be the guides for further study.
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Affiliation(s)
- Shuo Li
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
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14
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Kwan T, Thompson SR. Noncanonical Translation Initiation in Eukaryotes. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a032672. [PMID: 29959190 DOI: 10.1101/cshperspect.a032672] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The vast majority of eukaryotic messenger RNAs (mRNAs) initiate translation through a canonical, cap-dependent mechanism requiring a free 5' end and 5' cap and several initiation factors to form a translationally active ribosome. Stresses such as hypoxia, apoptosis, starvation, and viral infection down-regulate cap-dependent translation during which alternative mechanisms of translation initiation prevail to express proteins required to cope with the stress, or to produce viral proteins. The diversity of noncanonical initiation mechanisms encompasses a broad range of strategies and cellular cofactors. Herein, we provide an overview and, whenever possible, a mechanistic understanding of the various noncanonical mechanisms of initiation used by cells and viruses. Despite many unanswered questions, recent advances have propelled our understanding of the scope, diversity, and mechanisms of alternative initiation.
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Affiliation(s)
- Thaddaeus Kwan
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
| | - Sunnie R Thompson
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294
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15
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The functional role of polyamines in eukaryotic cells. Int J Biochem Cell Biol 2018; 107:104-115. [PMID: 30578954 DOI: 10.1016/j.biocel.2018.12.012] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 12/15/2018] [Accepted: 12/19/2018] [Indexed: 11/22/2022]
Abstract
Polyamines, consisting of putrescine, spermidine and spermine are essential for normal cell growth and viability in eukaryotic cells. Since polyamines are cations, they interact with DNA, ATP, phospholipids, specific kinds of proteins, and especially with RNA. Consequently, the functions of these acidic compounds and some proteins are modified by polyamines. In this review, the functional modifications of these molecules by polyamines are presented. Structural change of specific mRNAs by polyamines causes the stimulation of the synthesis of several different proteins, which are important for cell growth and viability. eIF5 A, the only known protein containing a spermidine derivative, i.e. hypusine, also functions at the level of translation. Experimental results thus far obtained strongly suggest that the most important function of polyamines is at the level of translation.
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16
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Lei J, Jacobus EJ, Taverner WK, Fisher KD, Hemmi S, West K, Slater L, Lilley F, Brown A, Champion B, Duffy MR, Seymour LW. Expression of human CD46 and trans-complementation by murine adenovirus 1 fails to allow productive infection by a group B oncolytic adenovirus in murine cancer cells. J Immunother Cancer 2018; 6:55. [PMID: 29898782 PMCID: PMC6000980 DOI: 10.1186/s40425-018-0350-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 05/07/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Oncolytic viruses are currently experiencing accelerated development in several laboratories worldwide, with some forty-seven clinical trials currently recruiting. Many oncolytic viruses combine targeted cytotoxicity to cancer cells with a proinflammatory cell lysis. Due to their additional potential to express immunomodulatory transgenes, they are also often known as oncolytic viral vaccines. However, several types of oncolytic viruses are human-specific and the lack of suitable immune-competent animal models complicates biologically relevant evaluation of their vaccine potential. This is a particular challenge for group B adenoviruses, which fail to infect even those immunocompetent animal model systems identified as semi-permissive for type 5 adenovirus. Here, we aim to develop a murine cell line capable of supporting replication of a group B oncolytic adenovirus, enadenotucirev (EnAd), for incorporation into a syngeneic immunocompetent animal model to explore the oncolytic vaccine potential of group B oncolytic viruses. METHODS Transgenic murine cell lines were infected with EnAd expressing GFP transgene under replication-independent or -dependent promoters. Virus mRNA expression, genome replication, and late protein expression were determined by qRT-PCR, qPCR, and immunoblotting, respectively. We also use Balb/c immune-competent mice to determine the tumourogenicity and infectivity of transgenic murine cell lines. RESULTS Our results show that a broad range of human carcinoma cells will support EnAd replication, but not murine carcinoma cells. Murine cells can be readily modified to express surface human CD46, one of the receptors for group B adenoviruses, allowing receptor-mediated uptake of EnAd particles into the murine cells and expression of CMV promoter-driven transgenes. Although the early E1A mRNA was expressed in murine cells at levels similar to human cells, adenovirus E2B and Fibre mRNA expression levels were hampered and few virus genomes were produced. Unlike previous reports on group C adenoviruses, trans-complementation of group B adenoviruses by co-infection with mouse adenovirus 1 did not rescue replication. A panel of group B adenoviruses expressing individual mouse adenovirus 1 genes were also unable to rescue EnAd replication. CONCLUSION Together, these results indicate that there may be major differences in the early stages of replication of group C and B adenoviruses in murine cells, and that the block to the life cycle of B adenoviruses in murine cells occurs in the early stage of virus replication, perhaps reflecting poor activity of Ad11p E1A in murine cells.
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Affiliation(s)
- Janet Lei
- 0000 0004 1936 8948grid.4991.5Department of OncologyUniversity of Oxford OX3 7DQ Oxford UK
| | - Egon J Jacobus
- 0000 0004 1936 8948grid.4991.5Department of OncologyUniversity of Oxford OX3 7DQ Oxford UK
| | - William K Taverner
- 0000 0004 1936 8948grid.4991.5Department of OncologyUniversity of Oxford OX3 7DQ Oxford UK
| | - Kerry D Fisher
- 0000 0004 1936 8948grid.4991.5Department of OncologyUniversity of Oxford OX3 7DQ Oxford UK
| | - Silvio Hemmi
- 0000 0004 1937 0650grid.7400.3Institute of Molecular Life SciencesUniversity of Zurich Zurich Switzerland
| | - Katy West
- 0000 0004 0394 8673grid.476643.4PsiOxus Therapeutics Ltd PsiOxus House, 4-10 The Quadrant, Barton Lane OX14 3YS Abingdon Oxfordshire UK
| | - Lorna Slater
- 0000 0004 0394 8673grid.476643.4PsiOxus Therapeutics Ltd PsiOxus House, 4-10 The Quadrant, Barton Lane OX14 3YS Abingdon Oxfordshire UK
| | - Fred Lilley
- 0000 0004 0394 8673grid.476643.4PsiOxus Therapeutics Ltd PsiOxus House, 4-10 The Quadrant, Barton Lane OX14 3YS Abingdon Oxfordshire UK
| | - Alice Brown
- 0000 0004 0394 8673grid.476643.4PsiOxus Therapeutics Ltd PsiOxus House, 4-10 The Quadrant, Barton Lane OX14 3YS Abingdon Oxfordshire UK
| | - Brian Champion
- 0000 0004 0394 8673grid.476643.4PsiOxus Therapeutics Ltd PsiOxus House, 4-10 The Quadrant, Barton Lane OX14 3YS Abingdon Oxfordshire UK
| | - Margaret R Duffy
- 0000 0004 1936 8948grid.4991.5Department of OncologyUniversity of Oxford OX3 7DQ Oxford UK
| | - Len W Seymour
- 0000 0004 1936 8948grid.4991.5Department of OncologyUniversity of Oxford OX3 7DQ Oxford UK
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17
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Gaba A, Ayalew LE, Patel A, Kumar P, Tikoo SK. Bovine adenovirus‐3 protein VIII associates with eukaryotic initiation factor‐6 during infection. Cell Microbiol 2018. [DOI: 10.1111/cmi.12842] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Amit Gaba
- VIDO‐InterVacUniversity of Saskatchewan Saskatoon Saskatchewan Canada
- Veterinary MicrobiologyUniversity of Saskatchewan Saskatoon Saskatchewan Canada
| | - Lisanework E. Ayalew
- VIDO‐InterVacUniversity of Saskatchewan Saskatoon Saskatchewan Canada
- Veterinary MicrobiologyUniversity of Saskatchewan Saskatoon Saskatchewan Canada
| | - Amrutlal Patel
- VIDO‐InterVacUniversity of Saskatchewan Saskatoon Saskatchewan Canada
- Veterinary MicrobiologyUniversity of Saskatchewan Saskatoon Saskatchewan Canada
| | - Pankaj Kumar
- VIDO‐InterVacUniversity of Saskatchewan Saskatoon Saskatchewan Canada
| | - Suresh K. Tikoo
- VIDO‐InterVacUniversity of Saskatchewan Saskatoon Saskatchewan Canada
- Veterinary MicrobiologyUniversity of Saskatchewan Saskatoon Saskatchewan Canada
- Vaccinology & Immunotherapeutics Program, School of Public HealthUniversity of Saskatchewan Saskatoon Saskatchewan Canada
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18
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Pooggin MM, Ryabova LA. Ribosome Shunting, Polycistronic Translation, and Evasion of Antiviral Defenses in Plant Pararetroviruses and Beyond. Front Microbiol 2018; 9:644. [PMID: 29692761 PMCID: PMC5902531 DOI: 10.3389/fmicb.2018.00644] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/19/2018] [Indexed: 12/15/2022] Open
Abstract
Viruses have compact genomes and usually translate more than one protein from polycistronic RNAs using leaky scanning, frameshifting, stop codon suppression or reinitiation mechanisms. Viral (pre-)genomic RNAs often contain long 5′-leader sequences with short upstream open reading frames (uORFs) and secondary structure elements, which control both translation initiation and replication. In plants, viral RNA and DNA are targeted by RNA interference (RNAi) generating small RNAs that silence viral gene expression, while viral proteins are recognized by innate immunity and autophagy that restrict viral infection. In this review we focus on plant pararetroviruses of the family Caulimoviridae and describe the mechanisms of uORF- and secondary structure-driven ribosome shunting, leaky scanning and reinitiation after translation of short and long uORFs. We discuss conservation of these mechanisms in different genera of Caulimoviridae, including host genome-integrated endogenous viral elements, as well as in other viral families, and highlight a multipurpose use of the highly-structured leader sequence of plant pararetroviruses in regulation of translation, splicing, packaging, and reverse transcription of pregenomic RNA (pgRNA), and in evasion of RNAi. Furthermore, we illustrate how targeting of several host factors by a pararetroviral effector protein can lead to transactivation of viral polycistronic translation and concomitant suppression of antiviral defenses. Thus, activation of the plant protein kinase target of rapamycin (TOR) by the Cauliflower mosaic virus transactivator/viroplasmin (TAV) promotes reinitiation of translation after long ORFs on viral pgRNA and blocks antiviral autophagy and innate immunity responses, while interaction of TAV with the plant RNAi machinery interferes with antiviral silencing.
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Affiliation(s)
- Mikhail M Pooggin
- INRA, UMR Biologie et Génétique des Interactions Plante-Parasite, Montpellier, France
| | - Lyubov A Ryabova
- Institut de Biologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, UPR 2357, Université de Strasbourg, Strasbourg, France
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19
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Shirokikh NE, Preiss T. Translation initiation by cap-dependent ribosome recruitment: Recent insights and open questions. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1473. [PMID: 29624880 DOI: 10.1002/wrna.1473] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/02/2018] [Accepted: 02/14/2018] [Indexed: 12/14/2022]
Abstract
Gene expression universally relies on protein synthesis, where ribosomes recognize and decode the messenger RNA template by cycling through translation initiation, elongation, and termination phases. All aspects of translation have been studied for decades using the tools of biochemistry and molecular biology available at the time. Here, we focus on the mechanism of translation initiation in eukaryotes, which is remarkably more complex than prokaryotic initiation and is the target of multiple types of regulatory intervention. The "consensus" model, featuring cap-dependent ribosome entry and scanning of mRNA leader sequences, represents the predominantly utilized initiation pathway across eukaryotes, although several variations of the model and alternative initiation mechanisms are also known. Recent advances in structural biology techniques have enabled remarkable molecular-level insights into the functional states of eukaryotic ribosomes, including a range of ribosomal complexes with different combinations of translation initiation factors that are thought to represent bona fide intermediates of the initiation process. Similarly, high-throughput sequencing-based ribosome profiling or "footprinting" approaches have allowed much progress in understanding the elongation phase of translation, and variants of them are beginning to reveal the remaining mysteries of initiation, as well as aspects of translation termination and ribosomal recycling. A current view on the eukaryotic initiation mechanism is presented here with an emphasis on how recent structural and footprinting results underpin axioms of the consensus model. Along the way, we further outline some contested mechanistic issues and major open questions still to be addressed. This article is categorized under: Translation > Translation Mechanisms Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Nikolay E Shirokikh
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Thomas Preiss
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
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20
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Kashiwagi K, Terui Y, Igarashi K. Modulation of Protein Synthesis by Polyamines in Mammalian Cells. Methods Mol Biol 2018; 1694:325-336. [PMID: 29080177 DOI: 10.1007/978-1-4939-7398-9_27] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Polyamines exist mainly as RNA-polyamine complexes in cells. Thus, we looked for proteins whose synthesis is enhanced by polyamines at the level of translation in mammalian cells. Here, we describe how synthesis of Cct2 (T-complex protein 1, β-subunit, a chaperonin assisting in the folding actin, tubulin, and several other proteins) and eEF1A (one of the elongation factors of protein synthesis) is stimulated by polyamines at the level of translation. Polyamines stimulated Cct2 synthesis through the stimulation of ribosome shunting during 5'-processive scanning of 40S ribosomal subunits from the m7G-cap to the initiation codon AUG, and eEF1A synthesis through the structural change of the unusual position of a complementary sequence to 18S rRNA in eEF1A mRNA.
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Affiliation(s)
- Keiko Kashiwagi
- Faculty of Pharmacy, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba, 288-0025, Japan.
| | - Yusuke Terui
- Faculty of Pharmacy, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba, 288-0025, Japan
| | - Kazuei Igarashi
- Amine Pharma Research Institute, Innovation Plaza at Chiba University, 1-8-15 Inohana, Chuo-ku, Chiba, 260-0856, Japan
- Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8675, Japan
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21
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El-Mogy MA, Abdalla MA, Misic V, Haj-Ahmad Y. Effect of adenovirus infection on transgene expression under the adenoviral MLP/TPL and the CMVie promoter/enhancer in CHO cells. J Genet Eng Biotechnol 2017; 15:211-217. [PMID: 30647657 PMCID: PMC6296590 DOI: 10.1016/j.jgeb.2017.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 02/27/2017] [Accepted: 04/05/2017] [Indexed: 11/19/2022]
Abstract
The adenovirus major late promoter (MLP) and its translational regulator - the tripartite leader (TPL) sequence - can actively drive efficient gene expression during adenoviral infection. However, both elements have not been widely tested in transgene expression outside of the adenovirus genome context. In this study, we tested whether the combination of MLP and TPL would enhance transgene expression beyond that of the most widely used promoter in transgene expression in mammalian cells, the cytomegalovirus immediate early (CMVie) promoter/enhancer. The activity of these two regulatory elements was compared in Chinese hamster ovary (CHO) cells. Although transient expression was significantly higher under the control of the CMVie promoter/enhance compared to the MLP/TPL, this difference was greater at the level of transcription (30 folds) than translation (11 folds). Even with adenovirus infection to provide additional elements (in trans), CMVie promoter/enhancer exhibited significantly higher activity relative to MLP/TPL. Interestingly, the CMVie promoter/enhancer was 1.9 folds more active in adenovirus-infected cells than in non-infected cells. Our study shows that the MLP-TPL drives lower transgene expression than the CMVie promoter/enhancer particularly at the transcription level. The data also highlight the utility of the TPL sequence at the translation level and/or possible overwhelming of the cellular translational machinery by the high transcription activity of the CMVie promoter/enhancer. In addition, here we present data that show stimulation of the CMVie promoter/enhancer by adenovirus infection, which may prove interesting in future work to test the combination of CMVie/TPL sequence, and additional adenovirus elements, for transgene expression.
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Key Words
- Adenovirus
- CHO, Chinese hamster ovary
- CMVie promoter/enhancer
- CMVie, cytomegalovirus immediate early
- GFP, green fluorescence proteins
- IRES, internal ribosome entry site
- MLP
- MLP, major late promoter
- MOI, multiplicity of infection
- PFU, plaque forming unit
- RFU, relative fluorescence units
- TPL
- TPL, tripartite leader
- Transgene expression
- qPCR, Quantitative PCR
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Affiliation(s)
- Mohamed A. El-Mogy
- Molecular Biology Department, National Research Centre, Dokki, Giza, Egypt
- Department of Biological Sciences, Brock University, St. Catharines, ON, Canada
- Corresponding author at: Molecular Biology Department, National Research Centre, Dokki, Giza, Egypt.
| | - Moemen A.K. Abdalla
- Department of Biochemistry, Faculty of Science, Alexandria University, Alexandria, Egypt
| | - Vanja Misic
- Department of Biological Sciences, Brock University, St. Catharines, ON, Canada
| | - Yousef Haj-Ahmad
- Department of Biological Sciences, Brock University, St. Catharines, ON, Canada
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22
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Ramke M, Lee JY, Dyer DW, Seto D, Rajaiya J, Chodosh J. The 5'UTR in human adenoviruses: leader diversity in late gene expression. Sci Rep 2017; 7:618. [PMID: 28377580 PMCID: PMC5429599 DOI: 10.1038/s41598-017-00747-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 03/14/2017] [Indexed: 01/05/2023] Open
Abstract
Human adenoviruses (HAdVs) shut down host cellular cap-dependent mRNA translation while initiating the translation of viral late mRNAs in a cap-independent manner. HAdV 5′ untranslated regions (5′UTRs) are crucial for cap-independent initiation, and influence mRNA localization and stability. However, HAdV translational regulation remains relatively uncharacterized. The HAdV tripartite leader (TPL), composed of three introns (TPL 1–3), is critical to the translation of HAdV late mRNA. Herein, we annotated and analyzed 72 HAdV genotypes for the HAdV TPL and another previously described leader, the i-leader. Using HAdV species D, type 37 (HAdV-D37), we show by reverse transcription PCR and Sanger sequencing that mRNAs of the HAdV-D37 E3 transcription unit are spliced to the TPL. We also identified a polycistronic mRNA for RID-α and RID-β. Analysis of the i-leader revealed a potential open reading frame within the leader sequence and the termination of this potential protein in TPL3. A potential new leader embedded within the E3 region was also detected and tentatively named the j-leader. These results suggest an underappreciated complexity of post-transcriptional regulation, and the importance of HAdV 5′UTRs for precisely coordinated viral protein expression along the path from genotype to phenotype.
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Affiliation(s)
- Mirja Ramke
- Howe Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, 243 Charles Street, Boston, Massachusetts, USA
| | - Jeong Yoon Lee
- Howe Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, 243 Charles Street, Boston, Massachusetts, USA
| | - David W Dyer
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Donald Seto
- Bioinformatics and Computational Biology Program, School of Systems Biology, George Mason University, Manassas, Virginia, USA
| | - Jaya Rajaiya
- Howe Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, 243 Charles Street, Boston, Massachusetts, USA.
| | - James Chodosh
- Howe Laboratory, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, 243 Charles Street, Boston, Massachusetts, USA.
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23
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Ayalew LE, Patel AK, Gaba A, Islam A, Tikoo SK. Bovine Adenovirus-3 pVIII Suppresses Cap-Dependent mRNA Translation Possibly by Interfering with the Recruitment of DDX3 and Translation Initiation Factors to the mRNA Cap. Front Microbiol 2016; 7:2119. [PMID: 28082972 PMCID: PMC5186766 DOI: 10.3389/fmicb.2016.02119] [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: 05/11/2016] [Accepted: 12/15/2016] [Indexed: 12/20/2022] Open
Abstract
Earlier, targeting of DDX3 by few viral proteins has defined its role in mRNA transport and induction of interferon production. This study was conducted to investigate the function of bovine adenovirus (BAdV)-3 pVIII during virus infection. Here, we provided evidence regarding involvement of DDX3 in cap dependent cellular mRNA translation and demonstrated that targeting of DDX3 by adenovirus protein VIII interfered with cap-dependent mRNA translation function of DDX3 in virus infected cells. Adenovirus late protein pVIII interacted with DDX3 in transfected and BAdV-3 infected cells. pVIII inhibited capped mRNA translation in vitro and in vivo by limiting the amount of DDX3 and eIF3. Diminished amount of DDX3 and eIFs including eIF3, eIF4E, eIF4G, and PABP were present in cap binding complex in BAdV-3 infected or pVIII transfected cells with no trace of pVIII in cap binding complex. The total amount of eIFs appeared similar in uninfected or infected cells as BAdV-3 did not appear to degrade eIFs. The co-immunoprecipitation experiments indicated the absence of direct interaction between pVIII and eIF3, eIF4E, or PABP. These data indicate that interaction of pVIII with DDX3 interferes with the binding of eIF3, eIF4E and PABP to the 5′ Cap. We conclude that DDX3 promotes cap-dependent cellular mRNA translation and BAdV-3 pVIII inhibits translation of capped cellular mRNA possibly by interfering with the recruitment of eIFs to the capped cellular mRNA.
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Affiliation(s)
- Lisanework E Ayalew
- Vaccine and Infectious Disease Organization - International Vaccine Centre, University of Saskatchewan, Saskatoon, SKCanada; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SKCanada
| | - Amrutlal K Patel
- Vaccine and Infectious Disease Organization - International Vaccine Centre, University of Saskatchewan, Saskatoon, SKCanada; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SKCanada
| | - Amit Gaba
- Vaccine and Infectious Disease Organization - International Vaccine Centre, University of Saskatchewan, Saskatoon, SKCanada; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SKCanada
| | - Azharul Islam
- Vaccine and Infectious Disease Organization - International Vaccine Centre, University of Saskatchewan, Saskatoon, SK Canada
| | - Suresh K Tikoo
- Vaccine and Infectious Disease Organization - International Vaccine Centre, University of Saskatchewan, Saskatoon, SKCanada; Department of Veterinary Microbiology, University of Saskatchewan, Saskatoon, SKCanada; Vaccinology & Immunotherapeutics Program, School of Public Health, University of Saskatchewan, Saskatoon, SKCanada
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24
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Curran JA, Weiss B. What Is the Impact of mRNA 5' TL Heterogeneity on Translational Start Site Selection and the Mammalian Cellular Phenotype? Front Genet 2016; 7:156. [PMID: 27630668 PMCID: PMC5005323 DOI: 10.3389/fgene.2016.00156] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 08/16/2016] [Indexed: 12/23/2022] Open
Abstract
A major determinant in the efficiency of ribosome loading onto mRNAs is the 5′ TL (transcript leader or 5′ UTR). In addition, elements within this region also impact on start site selection demonstrating that it can modulate the protein readout at both quantitative and qualitative levels. With the increasing wealth of data generated by the mining of the mammalian transcriptome, it has become evident that a genes 5′ TL is not homogeneous but actually exhibits significant heterogeneity. This arises due to the utilization of alternative promoters, and is further compounded by significant variability with regards to the precise transcriptional start sites of each (not to mention alternative splicing). Consequently, the transcript for a protein coding gene is not a unique mRNA, but in-fact a complexed quasi-species of variants whose composition may respond to the changing physiological environment of the cell. Here we examine the potential impact of these events with regards to the protein readout.
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Affiliation(s)
- Joseph A Curran
- Department of Microbiology and Molecular Medicine, Medical School, University of GenevaGeneva, Switzerland; Institute of Genetics and Genomics of Geneva, University of GenevaGeneva, Switzerland
| | - Benjamin Weiss
- Department of Microbiology and Molecular Medicine, Medical School, University of Geneva Geneva, Switzerland
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25
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Villanueva E, Martí-Solano M, Fillat C. Codon optimization of the adenoviral fiber negatively impacts structural protein expression and viral fitness. Sci Rep 2016; 6:27546. [PMID: 27278133 PMCID: PMC4899721 DOI: 10.1038/srep27546] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/20/2016] [Indexed: 11/09/2022] Open
Abstract
Codon usage adaptation of lytic viruses to their hosts is determinant for viral fitness. In this work, we analyzed the codon usage of adenoviral proteins by principal component analysis and assessed their codon adaptation to the host. We observed a general clustering of adenoviral proteins according to their function. However, there was a significant variation in the codon preference between the host-interacting fiber protein and the rest of structural late phase proteins, with a non-optimal codon usage of the fiber. To understand the impact of codon bias in the fiber, we optimized the Adenovirus-5 fiber to the codon usage of the hexon structural protein. The optimized fiber displayed increased expression in a non-viral context. However, infection with adenoviruses containing the optimized fiber resulted in decreased expression of the fiber and of wild-type structural proteins. Consequently, this led to a drastic reduction in viral release. The insertion of an exogenous optimized protein as a late gene in the adenovirus with the optimized fiber further interfered with viral fitness. These results highlight the importance of balancing codon usage in viral proteins to adequately exploit cellular resources for efficient infection and open new opportunities to regulate viral fitness for virotherapy and vaccine development.
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Affiliation(s)
- Eneko Villanueva
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
| | - Maria Martí-Solano
- Research Programme on Biomedical Informatics, Department of Experimental and Health Sciences, Pompeu Fabra University, Hospital del Mar Medical Research Institute, Barcelona, Spain
| | - Cristina Fillat
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Barcelona, Spain
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Remaining Mysteries of Molecular Biology: The Role of Polyamines in the Cell. J Mol Biol 2015; 427:3389-406. [DOI: 10.1016/j.jmb.2015.06.020] [Citation(s) in RCA: 401] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Revised: 06/12/2015] [Accepted: 06/29/2015] [Indexed: 11/23/2022]
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Igarashi K, Kashiwagi K. Modulation of protein synthesis by polyamines. IUBMB Life 2015; 67:160-9. [PMID: 25906835 DOI: 10.1002/iub.1363] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Accepted: 02/02/2015] [Indexed: 11/09/2022]
Abstract
Polyamines are ubiquitous small basic molecules that play important roles in cell growth and viability. Since polyamines mainly exist as a polyamine-RNA complex, we looked for proteins whose synthesis is preferentially stimulated by polyamines at the level of translation, and thus far identified 17 proteins in Escherichia coli and 6 proteins in eukaryotes. The mechanisms of polyamine stimulation of synthesis of these proteins were investigated. In addition, the role of eIF5A, containing hypusine formed from spermidine, on protein synthesis is described. These results clearly indicate that polyamines and eIF5A contribute to cell growth and viability through modulation of protein synthesis.
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Affiliation(s)
- Kazuei Igarashi
- Department of Clinical Biochemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Chuo-Ku, Chiba, Japan; Amine Pharma Research Institute, Chuo-Ku, Chiba, Japan
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Garcia-Moreno M, Sanz MA, Carrasco L. Initiation codon selection is accomplished by a scanning mechanism without crucial initiation factors in Sindbis virus subgenomic mRNA. RNA (NEW YORK, N.Y.) 2015; 21:93-112. [PMID: 25404563 PMCID: PMC4274640 DOI: 10.1261/rna.047084.114] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Translation initiation of alphavirus subgenomic mRNA (sgmRNA) can occur in the absence of several initiation factors (eIFs) in infected cells; however, the precise translation mechanism is still poorly understood. In this study, we have examined the mechanism of initiation and AUG selection in Sindbis virus (SINV) sgmRNA. Our present findings suggest that sgmRNA is translated via a scanning mechanism, since the presence of a hairpin structure before the initiation codon hampers protein synthesis directed by this mRNA. In addition, translation is partially recovered when an in-frame AUG codon is placed upstream of this hairpin. This scanning process takes place without the participation of eIF4A and active eIF2. These results, combined with our findings through modifying the SINV sgmRNA leader sequence, do not support the possibility of a direct initiation from the start codon without previous scanning, or a shunting mechanism. Moreover, studies carried out with sgmRNAs containing two alternative AUG codons within a good context for translation reveal differences in AUG selection which are dependent on the cellular context and the phosphorylation state of eIF2α. Thus, initiation at the additional AUG is strictly dependent on active eIF2, whereas the genuine AUG codon can start translation following eIF2α inactivation. Collectively, our results suggest that SINV sgmRNA is translated by a scanning mechanism without the potential participation of crucial eIFs. A model is presented that explains the mechanism of initiation of mRNAs bearing two alternative initiation codons.
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Affiliation(s)
- Manuel Garcia-Moreno
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), C/Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Miguel Angel Sanz
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), C/Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
| | - Luis Carrasco
- Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), C/Nicolás Cabrera 1, Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain
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Terui Y, Sakamoto A, Yoshida T, Kasahara T, Tomitori H, Higashi K, Igarashi K, Kashiwagi K. Polyamine stimulation of eEF1A synthesis based on the unusual position of a complementary sequence to 18S rRNA in eEF1A mRNA. Amino Acids 2014; 47:345-56. [PMID: 25425115 DOI: 10.1007/s00726-014-1867-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Accepted: 11/02/2014] [Indexed: 01/11/2023]
Abstract
It is thought that Shine-Dalgarno-like sequences, which exhibit complementarity to the nucleotide sequences at the 3'-end of 18S rRNA, are not present in eukaryotic mRNAs. However, complementary sequences consisting of more than 5 nucleotides to the 3'-end of 18S rRNA, i.e., a CR sequence, are present at -17 to -32 upstream from the initiation codon AUG in 18 mRNAs involved in protein synthesis except eEF1A mRNA. Thus, effects of the CR sequence in mRNAs and polyamines on protein synthesis were examined using control and polyamine-reduced FM3A and NIH3T3 cells. Polyamines did not stimulate protein synthesis encoded by 18 mRNAs possessing a normal CR sequence. When the CR sequence was deleted, protein synthetic activities decreased to less than 70% of intact mRNAs. In eEF1A mRNA, the CR sequence was located at -33 to -39 upstream from the initiation codon AUG, and polyamines stimulated eEF1A synthesis about threefold. When the CR sequence was shifted to -22 to -28 upstream from the AUG, eEF1A synthesis increased in polyamine-reduced cells and the degree of polyamine stimulation decreased greatly. The results indicate that the CR sequence exists in many eukaryotic mRNAs, and the location of a CR sequence in mRNAs influences polyamine stimulation of protein synthesis.
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Affiliation(s)
- Yusuke Terui
- Faculty of Pharmacy, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba, 288-0025, Japan
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Yasuda M, Hatanaka T, Shirato H, Nishioka T. Cell type-specific reciprocal regulation of HIF1A gene expression is dependent on 5'- and 3'-UTRs. Biochem Biophys Res Commun 2014; 447:638-43. [PMID: 24769203 DOI: 10.1016/j.bbrc.2014.04.058] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 04/11/2014] [Indexed: 01/04/2023]
Abstract
In the present study, we demonstrated the reciprocal regulation of hypoxia-inducible factor 1 alpha (HIF1A) gene expression via untranslated region-(UTR) dependent mechanisms. A 151 nucleotide sequence found in the HIF1A 5'-UTR is sufficient for significant translational up-regulation. On the other hand, the 3'-UTR of HIF1A has been implicated in mRNA degradation. In the non-metastatic breast cancer cell line MCF7, the 3'-UTR-dependent down-regulatory machinery predominates over the 5'-UTR-dependent up-regulation of HIF1A. However, 5'-UTR-dependent up-regulation is dominant among metastatic cell lines (MDA-MB453, U87MG). It is therefore likely that the predominance of 5'-UTR-dependent translational enhancement of HIF1A is critical for the malignant phenotype of cancer cells. PTBP-1, but not HuR, is a candidate RNA binding protein for the translational control of HIF1A.
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Affiliation(s)
- Motoaki Yasuda
- Department of Oral Pathobiology, Graduate School of Dental Medicine, Hokkaido University, N13 W7, Kita-ku, Sapporo 060-8586, Japan
| | - Tomoyuki Hatanaka
- Department of Oral Pathobiology, Graduate School of Dental Medicine, Hokkaido University, N13 W7, Kita-ku, Sapporo 060-8586, Japan
| | - Hiroki Shirato
- Department of Radiation Medicine, Hokkaido University School of Medicine, K15 W7, Kita-ku, Sapporo 060-8638, Japan
| | - Takeshi Nishioka
- Department of Biomedical Sciences and Engineering, Graduate School of Health Sciences, Hokkaido University, N12 W5, Kita-ku, Sapporo 060-0812, Japan.
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Abstract
Internal ribosome entry sites/segments (IRESs) were first discovered over 20 years ago in picornaviruses, followed by the discovery of two other types of IRES in hepatitis C virus (HCV), and the dicistroviruses, which infect invertebrates. In the meantime, reports of IRESs in eukaryotic cellular mRNAs started to appear, and the list of such putative IRESs continues to grow to the point in which it now stands at ~100, 80% of them in vertebrate mRNAs. Despite initial skepticism from some quarters, there now seems universal agreement that there is genuine internal ribosome entry on the viral IRESs. However, the same cannot be said for cellular mRNA IRESs, which continue to be shrouded in controversy. The aim of this article is to explain why vertebrate mRNA IRESs remain controversial, and to discuss ways in which these controversies might be resolved.
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Affiliation(s)
- Richard J Jackson
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom.
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Walsh D, Mathews MB, Mohr I. Tinkering with translation: protein synthesis in virus-infected cells. Cold Spring Harb Perspect Biol 2013; 5:a012351. [PMID: 23209131 DOI: 10.1101/cshperspect.a012351] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Viruses are obligate intracellular parasites, and their replication requires host cell functions. Although the size, composition, complexity, and functions encoded by their genomes are remarkably diverse, all viruses rely absolutely on the protein synthesis machinery of their host cells. Lacking their own translational apparatus, they must recruit cellular ribosomes in order to translate viral mRNAs and produce the protein products required for their replication. In addition, there are other constraints on viral protein production. Crucially, host innate defenses and stress responses capable of inactivating the translation machinery must be effectively neutralized. Furthermore, the limited coding capacity of the viral genome needs to be used optimally. These demands have resulted in complex interactions between virus and host that exploit ostensibly virus-specific mechanisms and, at the same time, illuminate the functioning of the cellular protein synthesis apparatus.
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Affiliation(s)
- Derek Walsh
- Department of Microbiology, New York University School of Medicine, New York, NY 10016, USA.
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Ribosomal protein S25 dependency reveals a common mechanism for diverse internal ribosome entry sites and ribosome shunting. Mol Cell Biol 2012; 33:1016-26. [PMID: 23275440 DOI: 10.1128/mcb.00879-12] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
During viral infection or cellular stress, cap-dependent translation is shut down. Proteins that are synthesized under these conditions use alternative mechanisms to initiate translation. This study demonstrates that at least two alternative translation initiation routes, internal ribosome entry site (IRES) initiation and ribosome shunting, rely on ribosomal protein S25 (RPS25). This suggests that they share a mechanism for initiation that is not employed by cap-dependent translation, since cap-dependent translation is not affected by the loss of RPS25. Furthermore, we demonstrate that viruses that utilize an IRES or a ribosome shunt, such as hepatitis C virus, poliovirus, or adenovirus, have impaired amplification in cells depleted of RPS25. In contrast, viral amplification of a virus that relies solely on cap-dependent translation, herpes simplex virus, is not hindered. We present a model that explains how RPS25 can be a nexus for multiple alternative translation initiation pathways.
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Abstract
Viruses have adapted a broad range of unique mechanisms to modulate the cellular translational machinery to ensure viral translation at the expense of cellular protein synthesis. Many of these promote virus-specific translation by use of molecular tags on viral mRNA such as internal ribosome entry sites (IRES) and genome-linked viral proteins (VPg) that bind translation machinery components in unusual ways and promote RNA circularization. This review describes recent advances in understanding some of the mechanisms in which animal virus mRNAs gain an advantage over cellular transcripts, including new structural and biochemical insights into IRES function and novel proteins that function as alternate met-tRNAimet carriers in translation initiation. Comparisons between animal and plant virus mechanisms that promote translation of viral mRNAs are discussed.
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Affiliation(s)
- Lucas C Reineke
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77030, USA
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35
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Paek KY, Park SM, Hong KY, Jang SK. Cap-dependent translation without base-by-base scanning of an messenger ribonucleic acid. Nucleic Acids Res 2012; 40:7541-51. [PMID: 22638585 PMCID: PMC3424581 DOI: 10.1093/nar/gks471] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
‘Ribosome scanning’ is the generally accepted mechanism for explaining how a ribosome finds an initiation codon located far removed from the ribosome recruiting site (cap structure). However, the molecular characteristics of ribosome scanning along 5′ untranslated regions (UTRs) remain obscure. Herein, using a rabbit reticulocyte lysate (RRL) system and artificial ribonucleic acid (RNA) constructs composed of a capped leader RNA and an uncapped reporter RNA annealed through a double-stranded RNA (dsRNA) bridge, we show that the ribosome can efficiently bypass a stable, dsRNA region without melting the structure. The insertion of an upstream open reading frame in the capped leader RNA impaired the translation of reporter RNA, indicating that a ribosome associated with the 5′-end explores the regions upstream of the dsRNA bridge in search of the initiation codon. These data indicate that a ribosome may skip part(s) of an messenger RNA 5′UTR without thoroughly scanning it.
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Affiliation(s)
- Ki Young Paek
- PBC, Department of Life Science, Pohang University of Science and Technology, San 31, Hyoja-dong, Nam-gu, Pohang, Kyungbuk 790-784, Republic of Korea
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36
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A new framework for understanding IRES-mediated translation. Gene 2012; 502:75-86. [PMID: 22555019 DOI: 10.1016/j.gene.2012.04.039] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Revised: 03/23/2012] [Accepted: 04/17/2012] [Indexed: 01/08/2023]
Abstract
Studies over the past 5 or so years have indicated that the traditional clustering of mechanisms for translation initiation in eukaryotes into cap-dependent and cap-independent (or IRES-mediated) is far too narrow. From individual studies of a number of mRNAs encoding proteins that are regulatory in nature (i.e. likely to be needed in small amounts such as transcription factors, protein kinases, etc.), it is now evident that mRNAs exist that blur these boundaries. This review seeks to set the basic ground rules for the analysis of different initiation pathways that are associated with these new mRNAs as well as related to the more traditional mechanisms, especially the cap-dependent translational process that is the major route of initiation of mRNAs for housekeeping proteins and thus, the bulk of protein synthesis in most cells. It will become apparent that a mixture of descriptions is likely to become the norm in the near future (i.e. m(7)G-assisted internal initiation).
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Abstract
Although viruses encode many of the functions that are required for viral replication, they are completely reliant on the protein synthesis machinery that is present in their host cells. Recruiting cellular ribosomes to translate viral mRNAs represents a crucial step in the replication of all viruses. To ensure translation of their mRNAs, viruses use a diverse collection of strategies (probably pirated from their cellular hosts) to commandeer key translation factors that are required for the initiation, elongation and termination steps of translation. Viruses also neutralize host defences that seek to incapacitate the translation machinery in infected cells.
Viruses rely on the translation machinery of the host cell to produce the proteins that are essential for their replication. Here, Walsh and Mohr discuss the diverse strategies by which viruses subvert the host protein synthesis machinery and regulate the translation of viral mRNAs. Viruses are fully reliant on the translation machinery of their host cells to produce the polypeptides that are essential for viral replication. Consequently, viruses recruit host ribosomes to translate viral mRNAs, typically using virally encoded functions to seize control of cellular translation factors and the host signalling pathways that regulate their activity. This not only ensures that viral proteins will be produced, but also stifles innate host defences that are aimed at inhibiting the capacity of infected cells for protein synthesis. Remarkably, nearly every step of the translation process can be targeted by virally encoded functions. This Review discusses the diverse strategies that viruses use to subvert host protein synthesis functions and regulate mRNA translation in infected cells.
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38
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Szolajska E, Chroboczek J. Faithful chaperones. Cell Mol Life Sci 2011; 68:3307-22. [PMID: 21655914 PMCID: PMC3181412 DOI: 10.1007/s00018-011-0740-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Revised: 05/19/2011] [Accepted: 05/23/2011] [Indexed: 12/01/2022]
Abstract
This review describes the properties of some rare eukaryotic chaperones that each assist in the folding of only one target protein. In particular, we describe (1) the tubulin cofactors, (2) p47, which assists in the folding of collagen, (3) α-hemoglobin stabilizing protein (AHSP), (4) the adenovirus L4-100 K protein, which is a chaperone of the major structural viral protein, hexon, and (5) HYPK, the huntingtin-interacting protein. These various-sized proteins (102–1,190 amino acids long) are all involved in the folding of oligomeric polypeptides but are otherwise functionally unique, as they each assist only one particular client. This raises a question regarding the biosynthetic cost of the high-level production of such chaperones. As the clients of faithful chaperones are all abundant proteins that are essential cellular or viral components, it is conceivable that this necessary metabolic expenditure withstood evolutionary pressure to minimize biosynthetic costs. Nevertheless, the complexity of the folding pathways in which these chaperones are involved results in error-prone processes. Several human disorders associated with these chaperones are discussed.
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Affiliation(s)
- Ewa Szolajska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02106 Warsaw, Poland
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39
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Kato SEM, Huang W, Flint SJ. Role of the RNA recognition motif of the E1B 55 kDa protein in the adenovirus type 5 infectious cycle. Virology 2011; 417:9-17. [PMID: 21605885 DOI: 10.1016/j.virol.2011.04.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 04/08/2011] [Accepted: 04/25/2011] [Indexed: 11/30/2022]
Abstract
Although the adenovirus type 5 (Ad5) E1B 55 kDa protein can bind to RNA in vitro, no UV-light-induced crosslinking of this E1B protein to RNA could be detected in infected cells, under conditions in which RNA binding by a known viral RNA-binding protein (the L4 100 kDa protein) was observed readily. Substitution mutations, including substitutions reported to inhibit RNA binding in vitro, did not impair synthesis of viral early or late proteins or alter significantly the efficiency of viral replication in transformed or normal human cells. However, substitutions of conserved residues in the C-terminal segment of an RNA recognition motif specifically inhibited degradation of Mre11. We conclude that, if the E1B 55 kDa protein binds to RNA in infected cells in the same manner as in in vitro assays, this activity is not required for such well established functions as induction of selective export of viral late mRNAs.
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Affiliation(s)
- Sayuri E M Kato
- Princeton University, Department of Molecular Biology, Lewis Thomas Laboratory, Princeton, NJ 08544, USA
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40
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Griffin BD, Nagy É. Coding potential and transcript analysis of fowl adenovirus 4: insight into upstream ORFs as common sequence features in adenoviral transcripts. J Gen Virol 2011; 92:1260-1272. [PMID: 21430092 DOI: 10.1099/vir.0.030064-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Recombinant fowl adenoviruses (FAdVs) have been successfully used as veterinary vaccine vectors. However, insufficient definitions of the protein-coding and non-coding regions and an incomplete understanding of virus-host interactions limit the progress of next-generation vectors. FAdVs are known to cause several diseases of poultry. Certain isolates of species FAdV-C are the aetiological agent of inclusion body hepatitis/hydropericardium syndrome (IBH/HPS). In this study, we report the complete 45667 bp genome sequence of FAdV-4 of species FAdV-C. Assessment of the protein-coding potential of FAdV-4 was carried out with the Bio-Dictionary-based Gene Finder together with an evaluation of sequence conservation among species FAdV-A and FAdV-D. On this basis, 46 potentially protein-coding ORFs were identified. Of these, 33 and 13 ORFs were assigned high and low protein-coding potential, respectively. Homologues of the ancestral adenoviral genes were, with few exceptions, assigned high protein-coding potential. ORFs that were unique to the FAdVs were differentiated into high and low protein-coding potential groups. Notable putative genes with high protein-coding capacity included the previously unreported fiber 1, hypothetical 10.3K and hypothetical 10.5K genes. Transcript analysis revealed that several of the small ORFs less than 300 nt in length that were assigned low coding potential contributed to upstream ORFs (uORFs) in important mRNAs, including the ORF22 mRNA. Subsequent analysis of the previously reported transcripts of FAdV-1, FAdV-9, human adenovirus 2 and bovine adenovirus 3 identified widespread uORFs in AdV mRNAs that have the potential to act as important translational regulatory elements.
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Affiliation(s)
- Bryan D Griffin
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Éva Nagy
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
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Manipulation of the host translation initiation complex eIF4F by DNA viruses. Biochem Soc Trans 2011; 38:1511-6. [PMID: 21118117 DOI: 10.1042/bst0381511] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the absence of their own translational machinery, all viruses must gain access to host cell ribosomes to synthesize viral proteins and replicate. Ribosome recruitment and scanning of capped host mRNAs is facilitated by the multisubunit eIF (eukaryotic initiation factor) 4F, which consists of a cap-binding protein, eIF4E and an RNA helicase, eIF4A, assembled on a large scaffolding protein, eIF4G. Although inactivated by many viruses to inhibit host translation, a growing number of DNA viruses are being found to employ diverse strategies to stimulate eIF4F activity in infected cells and maximize viral protein synthesis. These strategies include stimulation of cellular mTOR (mammalian target of rapamycin) signalling to inactivate 4E-BPs (eIF4E-binding proteins), a family of translational repressors that limit eIF4E availability and eIF4F complex formation, together with modulating the activity of the eIF4E kinase Mnk (mitogen-activated protein kinase signal-integrating kinase) in a variety of manners to regulate both host and viral mRNA translation. In some cases, specific viral proteins that mediate these signalling events have been identified, whereas others have been shown to interact with host translation initiation factors or complexes and modify their activity and/or subcellular localization. The present review outlines current understanding of the role of eIF4F in the life cycle of various DNA viruses and discusses its potential as a therapeutic target to suppress viral infection.
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42
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Abaeva IS, Marintchev A, Pisareva VP, Hellen CUT, Pestova TV. Bypassing of stems versus linear base-by-base inspection of mammalian mRNAs during ribosomal scanning. EMBO J 2010; 30:115-29. [PMID: 21113134 DOI: 10.1038/emboj.2010.302] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 11/03/2010] [Indexed: 11/10/2022] Open
Abstract
Initiation codon selection in eukaryotes involves base-by-base inspection of the 5'-untranslated region of mRNA by scanning ribosomal 43S preinitiation complexes. We employed in vitro reconstitution to investigate factor requirements for this process and report that in the absence of eIF1 and DHX29, eIFs 4A, 4B and 4G promote efficient bypassing of stable stems by scanning 43S complexes and formation of 48S initiation complexes on AUG codons immediately upstream and downstream of such stems, without their unwinding. However, intact stems are not threaded through the entire mRNA Exit channel of the 40S subunit, resulting in incorrect positioning of mRNA upstream of the ribosomal P site in 48S complexes formed on AUG codons following intact stems, which renders them susceptible to dissociation by eIF1. In 48S complexes formed on AUG codons preceding intact stems, the stems are accommodated in the A site. Such aberrant complexes are destabilized by DHX29, which also ensures that mRNA enters the mRNA-binding cleft in a single-stranded form and therefore undergoes base-by-base inspection during scanning.
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Affiliation(s)
- Irina S Abaeva
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
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43
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Wiener D, Vandevelde M, Zurbriggen A, Plattet P. Investigation of a unique short open reading frame within the 3' untranslated region of the canine distemper virus matrix messenger RNA. Virus Res 2010; 153:234-43. [PMID: 20797417 DOI: 10.1016/j.virusres.2010.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 08/03/2010] [Accepted: 08/08/2010] [Indexed: 10/19/2022]
Abstract
Increasing evidence suggest that the long "untranslated" region (UTR) between the matrix (M) and the fusion (F) proteins of morbilliviruses has a functional role. In canine distemper virus (CDV), the F 5' UTR was recently shown to code for a long F signal peptide (Fsp). Subsequently, it was reported that the M/F UTRs combined with the long Fsp were synergistically regulating the F mRNA and protein expression, thereby modulating virulence. Unique to CDV, a short putative open reading frame (ORF) has been identified within the wild-type CDV-M 3' UTR (termed M2). Here, we investigated whether M2 was expressed from the genome of the virulent and demyelinating A75/17-CDV strain. An expression plasmid encoding the M2 ORF tagged both at its N-terminal (HA) and C-terminal domains (RFP), was first constructed. Then, a recombinant virus with its putative M2 ORF replaced by HA-M2-RFP was successfully recovered from cDNA (termed recA75/17(green)-HA-M2-RFP). M2 expression in cells transfected or infected with these mutants was studied by immunoprecipitation, immunofluorescence, immunoblot and flow cytometry analyses. Although fluorescence was readily detected in HA-M2-RFP-transfected cells, absence of red fluorescence emission in several recA75/17(green)-HA-M2-RFP-infected cell types suggested lack of M2 biosynthesis, which was confirmed by the other techniques. Consistent with these data, no functional role of the short polypeptide was revealed by infecting various cell types with HA-M2-RFP over-expressing or M2-knockout recombinant viruses. Thus, in sharp contrast to the CDV-F 5' UTR reported to translate a long Fsp, our data provided evidence that the CDV-M 3' UTR does not express any polypeptides.
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Affiliation(s)
- Dominique Wiener
- Department of Clinical Research and Veterinary Public Health, Vetsuisse Faculty, University of Bern, Bremgartenstrasse 109a, 3001 Bern, Switzerland
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López-Lastra M, Ramdohr P, Letelier A, Vallejos M, Vera-Otarola J, Valiente-Echeverría F. Translation initiation of viral mRNAs. Rev Med Virol 2010; 20:177-95. [PMID: 20440748 PMCID: PMC7169124 DOI: 10.1002/rmv.649] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Viruses depend on cells for their replication but have evolved mechanisms to achieve this in an efficient and, in some instances, a cell‐type‐specific manner. The expression of viral proteins is frequently subject to translational control. The dominant target of such control is the initiation step of protein synthesis. Indeed, during the early stages of infection, viral mRNAs must compete with their host counterparts for the protein synthetic machinery, especially for the limited pool of eukaryotic translation initiation factors (eIFs) that mediate the recruitment of ribosomes to both viral and cellular mRNAs. To circumvent this competition viruses use diverse strategies so that ribosomes can be recruited selectively to viral mRNAs. In this review we focus on the initiation of protein synthesis and outline some of the strategies used by viruses to ensure efficient translation initiation of their mRNAs. Copyright © 2010 John Wiley & Sons, Ltd.
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Affiliation(s)
- Marcelo López-Lastra
- Laboratorio de Virología Molecular, Instituto Milenio de Inmunología e Inmunoterapia, Centro de Investigaciones Médicas, Facultad de Medicina, Pontificia Universidad Católica de Chile, Marcoleta 391, Santiago, Chile.
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Racine T, Duncan R. Facilitated leaky scanning and atypical ribosome shunting direct downstream translation initiation on the tricistronic S1 mRNA of avian reovirus. Nucleic Acids Res 2010; 38:7260-72. [PMID: 20610435 PMCID: PMC2978376 DOI: 10.1093/nar/gkq611] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The S1 mRNA of avian reovirus is functionally tricistronic, encoding three unrelated proteins, p10, p17 and σC, from three sequential, partially overlapping open reading frames (ORFs). The mechanism of translation initiation at the 3'-proximal σC ORF is currently unknown. Transient RNA transfections using Renilla luciferase reporter constructs revealed only a modest reduction in reporter expression upon optimization of either the p10 or p17 start sites. Insertion of multiple upstream AUG (uAUG) codons in a preferred start codon sequence context resulted in a substantial retention of downstream translation initiation on the S1 mRNA, but not on a heterologous mRNA. The S1 mRNA therefore facilitates leaky scanning to promote ribosome access to the σC start codon. Evidence also indicates that σC translation is mediated by a second scanning-independent mechanism capable of bypassing upstream ORFs. This alternate mechanism is cap-dependent and requires a sequence-dependent translation enhancer element that is complementary to 18S rRNA. Downstream translation initiation of the tricistronic S1 mRNA is therefore made possible by two alternate mechanisms, facilitated leaky scanning and an atypical form of ribosome shunting. This dual mechanism of downstream translation initiation ensures sufficient expression of the σC cell attachment protein that is essential for infectious progeny virus production.
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Affiliation(s)
- Trina Racine
- Department of Microbiology and Immunology, Faculty of Medicine, Dalhousie University, Halifax, NS, Canada B3H1X5
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Wang JT, Chuang YC, Chen KL, Lu CC, Doong SL, Cheng HH, Chen YL, Liu TY, Chang Y, Han CH, Yeh SW, Chen MR. Characterization of Epstein-Barr virus BGLF4 kinase expression control at the transcriptional and translational levels. J Gen Virol 2010; 91:2186-96. [PMID: 20444992 DOI: 10.1099/vir.0.019729-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The BGLF4 protein of Epstein-Barr virus (EBV) is a serine/threonine protein kinase that phosphorylates several viral and cellular substrates at cellular cyclin-dependent kinase target sites. BGLF4 is required for efficient viral DNA replication and release of mature virions. It also stimulates the transactivation activity of the immediate-early transactivator Zta (BZLF1) and suppresses the transactivation activities of BMRF1 and EBNA-2. This study aimed to characterize further the regulation of BGLF4 expression at the transcriptional and translational levels. It was shown that BGLF4 was expressed with early kinetics and reached maximal levels after DNA replication. The promoter activity of BGLF4 was upregulated mainly by the immediate-early transactivator Rta, rather than Zta, as revealed by Zta-specific short hairpin RNA in EBV-positive cells and by luciferase reporter assays. By rapid amplification of 5' cDNA ends, two major transcriptional start sites were identified at 201 and 255 nt upstream of the first in-frame ATG of BGLF4 in P3HR1 cells. An additional transcript initiated from -468 was detected in Akata cells. The translation initiation site of BGLF4 was confirmed by mutagenesis, in vitro translation and transient transfection. The translation regulatory effect mediated by the long 5'-untranslated region (5'UTR) of BGLF4 was demonstrated by dual reporter assays in 293T and EBV-positive NA cells. These results suggested that different promoter usage and 5'UTR-mediated translation enhancement may ensure the proper expression of BGLF4 at various stages of virus replication.
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Affiliation(s)
- Jiin-Tarng Wang
- Department of Microbiology, National Taiwan University, Taipei, Taiwan, Republic of China
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Mechanism of initiation site selection promoted by the human rhinovirus 2 internal ribosome entry site. J Virol 2010; 84:6578-89. [PMID: 20427535 DOI: 10.1128/jvi.00123-10] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Translation initiation site usage on the human rhinovirus 2 internal ribosome entry site (IRES) has been examined in a mixed reticulocyte lysate/HeLa cell extract system. There are two relevant AUG triplets, both in a base-paired hairpin structure (domain VI), with one on the 5' side at nucleotide (nt) 576, base paired with the other at nt 611, which is the initiation site for polyprotein synthesis. A single residue was inserted in the apical loop to put AUG-576 in frame with AUG-611, and in addition another in-frame AUG was introduced at nt 593. When most of the IRES was deleted to generate a monocistronic mRNA, the use of these AUGs conformed to the scanning ribosome model: improving the AUG-576 context increased initiation at this site and decreased initiation at downstream sites, whereas the converse was seen when AUG-576 was mutated to GUA; and AUG-593, when present, took complete precedence over AUG-611. Under IRES-dependent conditions, by contrast, much less initiation occurred at AUG-576 than in a monocistronic mRNA with the same AUG-576 context, mutation of AUG-576 decreased initiation at downstream sites by approximately 70%, and introduction of AUG-593 did not completely abrogate initiation at AUG-611, unless the apical base pairing in domain VI was destroyed by point mutations. These results indicate that ribosomes first bind at the AUG-576 site, but instead of initiating there, most of them are transferred to AUG-611, the majority by strictly linear scanning and a substantial minority by direct transfer, which is possibly facilitated by the occasional persistence of base pairing in the apical part of the domain VI stem.
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Uemura T, Higashi K, Takigawa M, Toida T, Kashiwagi K, Igarashi K. Polyamine modulon in yeast—Stimulation of COX4 synthesis by spermidine at the level of translation. Int J Biochem Cell Biol 2009; 41:2538-45. [DOI: 10.1016/j.biocel.2009.08.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Accepted: 08/11/2009] [Indexed: 11/27/2022]
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Roberts LO, Jopling CL, Jackson RJ, Willis AE. Viral strategies to subvert the mammalian translation machinery. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:313-67. [PMID: 20374746 PMCID: PMC7102724 DOI: 10.1016/s1877-1173(09)90009-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Viruses do not carry their own protein biosynthesis machinery and the translation of viral proteins therefore requires that the virus usurps the machinery of the host cell. To allow optimal translation of viral proteins at the expense of cellular proteins, virus families have evolved a variety of methods to repress the host translation machinery, while allowing effective viral protein synthesis. Many viruses use noncanonical mechanisms that permit translation of their own RNAs under these conditions. Viruses have also developed mechanisms to evade host innate immune responses that would repress translation under conditions of viral infection, in particular PKR activation in response to double-stranded RNA (dsRNA). Importantly, the study of viral translation mechanisms has enormously enhanced our understanding of many aspects of the cellular protein biosynthesis pathway and its components. A number of unusual mechanisms of translation initiation that were first discovered in viruses have since been observed in cellular mRNAs, and it has become apparent that a diverse range of translation mechanisms operates in eukaryotes, allowing subtle regulation of this essential process.
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Affiliation(s)
- Lisa O Roberts
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
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