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Wu TY, Li YR, Chang KJ, Fang JC, Urano D, Liu MJ. Modeling alternative translation initiation sites in plants reveals evolutionarily conserved cis-regulatory codes in eukaryotes. Genome Res 2024; 34:272-285. [PMID: 38479836 PMCID: PMC10984385 DOI: 10.1101/gr.278100.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 02/15/2024] [Indexed: 03/22/2024]
Abstract
mRNA translation relies on identifying translation initiation sites (TISs) in mRNAs. Alternative TISs are prevalent across plant transcriptomes, but the mechanisms for their recognition are unclear. Using ribosome profiling and machine learning, we developed models for predicting alternative TISs in the tomato (Solanum lycopersicum). Distinct feature sets were predictive of AUG and nonAUG TISs in 5' untranslated regions and coding sequences, including a novel CU-rich sequence that promoted plant TIS activity, a translational enhancer found across dicots and monocots, and humans and viruses. Our results elucidate the mechanistic and evolutionary basis of TIS recognition, whereby cis-regulatory RNA signatures affect start site selection. The TIS prediction model provides global estimates of TISs to discover neglected protein-coding genes across plant genomes. The prevalence of cis-regulatory signatures across plant species, humans, and viruses suggests their broad and critical roles in reprogramming the translational landscape.
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Affiliation(s)
- Ting-Ying Wu
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan;
| | - Ya-Ru Li
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 711, Taiwan
| | - Kai-Jyun Chang
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 711, Taiwan
- Institute of Tropical Plant Sciences, National Cheng Kung University, Tainan 701, Taiwan
| | - Jhen-Cheng Fang
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 711, Taiwan
| | - Daisuke Urano
- Temasek Life Sciences Laboratory, Singapore 117604, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore 117558, Singapore
| | - Ming-Jung Liu
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 711, Taiwan;
- Institute of Tropical Plant Sciences, National Cheng Kung University, Tainan 701, Taiwan
- Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan
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Chen Z, Wang F, Chen B, Wu G, Tian D, Yuan Q, Qiu S, Zhai Y, Chen J, Zheng H, Yan F. Turnip mosaic virus NIb weakens the function of eukaryotic translation initiation factor 6 facilitating viral infection in Nicotiana benthamiana. MOLECULAR PLANT PATHOLOGY 2024; 25:e13434. [PMID: 38388027 PMCID: PMC10883789 DOI: 10.1111/mpp.13434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Revised: 01/26/2024] [Accepted: 01/28/2024] [Indexed: 02/24/2024]
Abstract
Viruses rely completely on host translational machinery to produce the proteins encoded by their genes. Controlling translation initiation is important for gaining translational advantage in conflicts between the host and virus. The eukaryotic translation initiation factor 4E (eIF4E) has been reported to be hijacked by potyviruses for virus multiplication. The role of translation regulation in defence and anti-defence between plants and viruses is not well understood. We report that the transcript level of eIF6 was markedly increased in turnip mosaic virus (TuMV)-infected Nicotiana benthamiana. TuMV infection was impaired by overexpression of N. benthamiana eIF6 (NbeIF6) either transiently expressed in leaves or stably expressed in transgenic plants. Polysome profile assays showed that overexpression of NbeIF6 caused the accumulation of 40S and 60S ribosomal subunits, the reduction of polysomes, and also compromised TuMV UTR-mediated translation, indicating a defence role for upregulated NbeIF6 during TuMV infection. However, the polysome profile in TuMV-infected leaves was not identical to that in leaves overexpressing NbeIF6. Further analysis showed that TuMV NIb protein, the RNA-dependent RNA polymerase, interacted with NbeIF6 and interfered with its effect on the ribosomal subunits, suggesting that NIb might have a counterdefence role. The results propose a possible regulatory mechanism at the translation level during plant-virus interaction.
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Affiliation(s)
- Ziqiang Chen
- College of Life ScienceFujian Agriculture and Forestry UniversityFuzhouChina
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Biotechnology Research InstituteFujian Academy of Agricultural SciencesFuzhouChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Feng Wang
- Biotechnology Research InstituteFujian Academy of Agricultural SciencesFuzhouChina
| | - Binghua Chen
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Guanwei Wu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Dagang Tian
- Biotechnology Research InstituteFujian Academy of Agricultural SciencesFuzhouChina
| | - Quan Yuan
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Shiyou Qiu
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Yushan Zhai
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Jianping Chen
- College of Life ScienceFujian Agriculture and Forestry UniversityFuzhouChina
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Hongying Zheng
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
| | - Fei Yan
- State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro‐productsInstitute of Plant Virology, Ningbo UniversityNingboChina
- Key Laboratory of Biotechnology in Plant Protection of MARA and Zhejiang ProvinceInstitute of Plant Virology, Ningbo UniversityNingboChina
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Fang JC, Liu MJ. Translation initiation at AUG and non-AUG triplets in plants. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2023; 335:111822. [PMID: 37574140 DOI: 10.1016/j.plantsci.2023.111822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 07/22/2023] [Accepted: 08/07/2023] [Indexed: 08/15/2023]
Abstract
In plants and other eukaryotes, precise selection of translation initiation site (TIS) on mRNAs shapes the proteome in response to cellular events or environmental cues. The canonical translation of mRNAs initiates at a 5' proximal AUG codon in a favorable context. However, the coding and non-coding regions of plant genomes contain numerous unannotated alternative AUG and non-AUG TISs. Determining how and why these unexpected and prevalent TISs are activated in plants has emerged as an exciting research area. In this review, we focus on the selection of plant TISs and highlight studies that revealed previously unannotated TISs used in vivo via comparative genomics and genome-wide profiling of ribosome positioning and protein N-terminal ends. The biological signatures of non-AUG TIS-initiated open reading frames (ORFs) in plants are also discussed. We describe what is understood about cis-regulatory RNA elements and trans-acting eukaryotic initiation factors (eIFs) in the site selection for translation initiation by featuring the findings in plants along with supporting findings in non-plant species. The prevalent, unannotated TISs provide a hidden reservoir of ORFs that likely help reshape plant proteomes in response to developmental or environmental cues. These findings underscore the importance of understanding the mechanistic basis of TIS selection to functionally annotate plant genomes, especially for crops with large genomes.
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Affiliation(s)
- Jhen-Cheng Fang
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 711, Taiwan
| | - Ming-Jung Liu
- Biotechnology Center in Southern Taiwan, Academia Sinica, Tainan 711, Taiwan; Agricultural Biotechnology Research Center, Academia Sinica, Taipei 115, Taiwan.
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Bera S, Ilyas M, Mikkelsen AA, Simon AE. Conserved Structure Associated with Different 3′CITEs Is Important for Translation of Umbraviruses. Viruses 2023; 15:v15030638. [PMID: 36992347 PMCID: PMC10051134 DOI: 10.3390/v15030638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 02/17/2023] [Accepted: 02/24/2023] [Indexed: 03/05/2023] Open
Abstract
The cap-independent translation of plus-strand RNA plant viruses frequently depends on 3′ structures to attract translation initiation factors that bind ribosomal subunits or bind directly to ribosomes. Umbraviruses are excellent models for studying 3′ cap-independent translation enhancers (3′CITEs), as umbraviruses can have different 3′CITEs in the central region of their lengthy 3′UTRs, and most also have a particular 3′CITE (the T-shaped structure or 3′TSS) near their 3′ ends. We discovered a novel hairpin just upstream of the centrally located (known or putative) 3′CITEs in all 14 umbraviruses. These CITE-associated structures (CASs) have conserved sequences in their apical loops and at the stem base and adjacent positions. In 11 umbraviruses, CASs are preceded by two small hairpins joined by a putative kissing loop interaction (KL). Converting the conserved 6-nt apical loop to a GNRA tetraloop in opium poppy mosaic virus (OPMV) and pea enation mosaic virus 2 (PEMV2) enhanced translation of genomic (g)RNA, but not subgenomic (sg)RNA reporter constructs, and significantly repressed virus accumulation in Nicotiana benthamiana. Other alterations throughout OPMV CAS also repressed virus accumulation and only enhanced sgRNA reporter translation, while mutations in the lower stem repressed gRNA reporter translation. Similar mutations in the PEMV2 CAS also repressed accumulation but did not significantly affect gRNA or sgRNA reporter translation, with the exception of deletion of the entire hairpin, which only reduced translation of the gRNA reporter. OPMV CAS mutations had little effect on the downstream BTE 3′CITE or upstream KL element, while PEMV2 CAS mutations significantly altered KL structures. These results introduce an additional element associated with different 3′CITEs that differentially affect the structure and translation of different umbraviruses.
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Conserved RNA secondary structure in Cherry virus A 5'-UTR associated with translation regulation. Virol J 2022; 19:91. [PMID: 35619168 PMCID: PMC9137147 DOI: 10.1186/s12985-022-01824-z] [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: 01/27/2022] [Accepted: 05/18/2022] [Indexed: 11/14/2022] Open
Abstract
Background A variety of cis-acting RNA elements with structures in the 5′- or 3′-untranslated region (UTR) of viral genomes play key roles in viral translation. Cherry virus A (CVA) is a member of the genus Capillovirus in the family Betaflexiviridae. It has a positive single-stranded RNA genome of ~ 7400 nucleotides (nt). The length of the CVA 5′-UTR is ~ 100 nt; however, the function of this long UTR has not yet been reported. Methods Molecular and phylogenetic analyses were performed on 75 CVA sequences, which could be divided into four groups, and the RNA secondary structure was predicted in four CVA 5′-UTR types. These four CVA 5′-UTR types were then inserted upstream of the firefly luciferase reporter gene FLuc (FLuc), and in vitro translation of the corresponding transcripts was evaluated using wheat germ extract (WGE). Then, in-line structure probing was performed to reveal the conserved RNA structures in CVA-5′UTR. Results The four CVA 5′-UTR types appeared to have a conserved RNA structure, and the FLuc construct containing these four CVA 5′-UTR types increased the translation of FLuc by 2–3 folds, suggesting weak translation enhancement activity. Mutations in CVA 5′-UTR suppressed translation, suggesting that the conserved RNA structure was important for function. Conclusion The conserved RNA secondary structure was identified by structural evolution analysis of different CVA isolates and was found to regulate translation.
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Jaramillo-Mesa H, Fischer E, Rakotondrafara AM. Multiple Cis-acting Polypyrimidine Tract Elements Regulate a Cooperative Mechanism for Triticum Mosaic Virus Internal Ribosomal Entry Site Activity. FRONTIERS IN PLANT SCIENCE 2022; 13:864832. [PMID: 35498652 PMCID: PMC9042117 DOI: 10.3389/fpls.2022.864832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 03/16/2022] [Indexed: 06/14/2023]
Abstract
Diverse elements within the 5' untranslated region of an mRNA can influence the translation efficiency at the main AUG codon. We previously identified a core picornaviral like Y16X11-AUG motif with 16-nt polypyrimidine CU tract separated by an 11-nt spacer sequence from the 13th AUG codon, which is recognized as the preferred initiation site within the Triticum mosaic virus (TriMV) internal ribosome entry site (IRES) element. The motif is proposed to function as an internal ribosomal landing site at the designated start codon. Here, we exposed the cooperative role of multiple CU-rich segments flanking the TriMV YX-AUG motif to reach and drive internal initiation of translation at the preferred start site. We propose that these auxiliary domains may enhance the ribosome capacity and their delivery at proximity of the correct initiation site. These polypyrimidine tracts can be modulated with a cryptic AUG in a position-dependent manner to replace the native YX-AUG motif, and thus uncovering a new layer of control of start codon selection. In line with these observations, mass spectrometry analysis of proteins directly interacting with translationally impaired TriMV IRES mutants that bear these motifs indicated an enrichment in 40S and 60S ribosomal related proteins, revealing a new function of polypyrimidine tracts to regulate IRES-driven translation. Accessibility of these RNA regions for in trans interaction was validated by SHAPE analysis of the entire TriMV leader sequence and supported by the ability of anti-sense oligonucleotides designed to block the CU tracts accessibility to impair IRES activity. This is the first evidence that defines the core modular domains required for ribosomal recruitment and start codon selection in a complex, multi-AUG viral 5' UTR for translation in plants.
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Sorokin II, Vassilenko KS, Terenin IM, Kalinina NO, Agol VI, Dmitriev SE. Non-Canonical Translation Initiation Mechanisms Employed by Eukaryotic Viral mRNAs. BIOCHEMISTRY. BIOKHIMIIA 2021; 86:1060-1094. [PMID: 34565312 PMCID: PMC8436584 DOI: 10.1134/s0006297921090042] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 08/04/2021] [Accepted: 08/04/2021] [Indexed: 12/12/2022]
Abstract
Viruses exploit the translation machinery of an infected cell to synthesize their proteins. Therefore, viral mRNAs have to compete for ribosomes and translation factors with cellular mRNAs. To succeed, eukaryotic viruses adopt multiple strategies. One is to circumvent the need for m7G-cap through alternative instruments for ribosome recruitment. These include internal ribosome entry sites (IRESs), which make translation independent of the free 5' end, or cap-independent translational enhancers (CITEs), which promote initiation at the uncapped 5' end, even if located in 3' untranslated regions (3' UTRs). Even if a virus uses the canonical cap-dependent ribosome recruitment, it can still perturb conventional ribosomal scanning and start codon selection. The pressure for genome compression often gives rise to internal and overlapping open reading frames. Their translation is initiated through specific mechanisms, such as leaky scanning, 43S sliding, shunting, or coupled termination-reinitiation. Deviations from the canonical initiation reduce the dependence of viral mRNAs on translation initiation factors, thereby providing resistance to antiviral mechanisms and cellular stress responses. Moreover, viruses can gain advantage in a competition for the translational machinery by inactivating individual translational factors and/or replacing them with viral counterparts. Certain viruses even create specialized intracellular "translation factories", which spatially isolate the sites of their protein synthesis from cellular antiviral systems, and increase availability of translational components. However, these virus-specific mechanisms may become the Achilles' heel of a viral life cycle. Thus, better understanding of the unconventional mechanisms of viral mRNA translation initiation provides valuable insight for developing new approaches to antiviral therapy.
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Affiliation(s)
- Ivan I Sorokin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
- Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, 141701, Russia
| | - Konstantin S Vassilenko
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Ilya M Terenin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Natalia O Kalinina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia
| | - Vadim I Agol
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
- Institute of Poliomyelitis, Chumakov Center for Research and Development of Immunobiological Products, Russian Academy of Sciences, Moscow, 108819, Russia
| | - Sergey E Dmitriev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia.
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119234, Russia
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Urquidi-Camacho RA, Lokdarshi A, von Arnim AG. Translational gene regulation in plants: A green new deal. WILEY INTERDISCIPLINARY REVIEWS. RNA 2020; 11:e1597. [PMID: 32367681 PMCID: PMC9258721 DOI: 10.1002/wrna.1597] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 03/31/2020] [Accepted: 04/01/2020] [Indexed: 01/09/2023]
Abstract
The molecular machinery for protein synthesis is profoundly similar between plants and other eukaryotes. Mechanisms of translational gene regulation are embedded into the broader network of RNA-level processes including RNA quality control and RNA turnover. However, over eons of their separate history, plants acquired new components, dropped others, and generally evolved an alternate way of making the parts list of protein synthesis work. Research over the past 5 years has unveiled how plants utilize translational control to defend themselves against viruses, regulate translation in response to metabolites, and reversibly adjust translation to a wide variety of environmental parameters. Moreover, during seed and pollen development plants make use of RNA granules and other translational controls to underpin developmental transitions between quiescent and metabolically active stages. The economics of resource allocation over the daily light-dark cycle also include controls over cellular protein synthesis. Important new insights into translational control on cytosolic ribosomes continue to emerge from studies of translational control mechanisms in viruses. Finally, sketches of coherent signaling pathways that connect external stimuli with a translational response are emerging, anchored in part around TOR and GCN2 kinase signaling networks. These again reveal some mechanisms that are familiar and others that are different from other eukaryotes, motivating deeper studies on translational control in plants. This article is categorized under: Translation > Translation Regulation RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Ricardo A. Urquidi-Camacho
- UT-ORNL Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN 37996
| | - Ansul Lokdarshi
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996
| | - Albrecht G von Arnim
- Department of Biochemistry & Cellular and Molecular Biology and UT-ORNL Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN 37996
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The 3' Untranslated Region of a Plant Viral RNA Directs Efficient Cap-Independent Translation in Plant and Mammalian Systems. Pathogens 2019; 8:pathogens8010028. [PMID: 30823456 PMCID: PMC6471432 DOI: 10.3390/pathogens8010028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 02/03/2019] [Accepted: 02/23/2019] [Indexed: 11/29/2022] Open
Abstract
Many plant viral RNA genomes lack a 5′ cap, and instead are translated via a cap-independent translation element (CITE) in the 3′ untranslated region (UTR). The panicum mosaic virus-like CITE (PTE), found in many plant viral RNAs, binds and requires the cap-binding translation initiation factor eIF4E to facilitate translation. eIF4E is structurally conserved between plants and animals, so we tested cap-independent translation efficiency of PTEs of nine plant viruses in plant and mammalian systems. The PTE from thin paspalum asymptomatic virus (TPAV) facilitated efficient cap-independent translation in wheat germ extract, rabbit reticulocyte lysate, HeLa cell lysate, and in oat and mammalian (BHK) cells. Human eIF4E bound the TPAV PTE but not a PTE that did not stimulate cap-independent translation in mammalian extracts or cells. Selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) footprinting revealed that both human and wheat eIF4E protected the conserved guanosine (G)-rich domain in the TPAV PTE pseudoknot. The central G plays a key role, as it was found to be required for translation and protection from SHAPE modification by eIF4E. These results provide insight on how plant viruses gain access to the host’s translational machinery, an essential step in infection, and raise the possibility that similar PTE-like mechanisms may exist in mRNAs of mammals or their viruses.
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