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Zhang H, Quintana J, Ütkür K, Adrian L, Hawer H, Mayer K, Gong X, Castanedo L, Schulten A, Janina N, Peters M, Wirtz M, Brinkmann U, Schaffrath R, Krämer U. Translational fidelity and growth of Arabidopsis require stress-sensitive diphthamide biosynthesis. Nat Commun 2022; 13:4009. [PMID: 35817801 PMCID: PMC9273596 DOI: 10.1038/s41467-022-31712-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 06/30/2022] [Indexed: 11/09/2022] Open
Abstract
Diphthamide, a post-translationally modified histidine residue of eukaryotic TRANSLATION ELONGATION FACTOR2 (eEF2), is the human host cell-sensitizing target of diphtheria toxin. Diphthamide biosynthesis depends on the 4Fe-4S-cluster protein Dph1 catalyzing the first committed step, as well as Dph2 to Dph7, in yeast and mammals. Here we show that diphthamide modification of eEF2 is conserved in Arabidopsis thaliana and requires AtDPH1. Ribosomal -1 frameshifting-error rates are increased in Arabidopsis dph1 mutants, similar to yeast and mice. Compared to the wild type, shorter roots and smaller rosettes of dph1 mutants result from fewer formed cells. TARGET OF RAPAMYCIN (TOR) kinase activity is attenuated, and autophagy is activated, in dph1 mutants. Under abiotic stress diphthamide-unmodified eEF2 accumulates in wild-type seedlings, most strongly upon heavy metal excess, which is conserved in human cells. In summary, our results suggest that diphthamide contributes to the functionality of the translational machinery monitored by plants to regulate growth.
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Affiliation(s)
- Hongliang Zhang
- Molecular Genetics and Physiology of Plants, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, Box 44 ND3/30, 44801, Bochum, Germany
| | - Julia Quintana
- Molecular Genetics and Physiology of Plants, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, Box 44 ND3/30, 44801, Bochum, Germany
| | - Koray Ütkür
- Microbiology, Institute for Biology, University of Kassel, 34132, Kassel, Germany
| | - Lorenz Adrian
- Environmental Biotechnology, Helmholtz Centre for Environmental Research-UFZ, 04318, Leipzig, Germany.,Chair of Geobiotechnology, Technische Universität Berlin, 13355, Berlin, Germany
| | - Harmen Hawer
- Microbiology, Institute for Biology, University of Kassel, 34132, Kassel, Germany
| | - Klaus Mayer
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, 82377, Penzberg, Germany
| | - Xiaodi Gong
- Centre for Organismal Studies (COS), University of Heidelberg, 69120, Heidelberg, Germany
| | - Leonardo Castanedo
- Molecular Genetics and Physiology of Plants, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, Box 44 ND3/30, 44801, Bochum, Germany
| | - Anna Schulten
- Molecular Genetics and Physiology of Plants, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, Box 44 ND3/30, 44801, Bochum, Germany
| | - Nadežda Janina
- Molecular Genetics and Physiology of Plants, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, Box 44 ND3/30, 44801, Bochum, Germany
| | - Marcus Peters
- Molecular Immunology, Medical Faculty, Ruhr University Bochum, 44801, Bochum, Germany
| | - Markus Wirtz
- Centre for Organismal Studies (COS), University of Heidelberg, 69120, Heidelberg, Germany
| | - Ulrich Brinkmann
- Roche Pharma Research & Early Development, Large Molecule Research, Roche Innovation Center Munich, 82377, Penzberg, Germany
| | - Raffael Schaffrath
- Microbiology, Institute for Biology, University of Kassel, 34132, Kassel, Germany
| | - Ute Krämer
- Molecular Genetics and Physiology of Plants, Faculty of Biology and Biotechnology, Ruhr University Bochum, Universitaetsstrasse 150, Box 44 ND3/30, 44801, Bochum, Germany.
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2
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Shao Y, Molestak E, Su W, Stankevič M, Tchórzewski M. Sordarin - the antifungal antibiotic with a unique modus operandi. Br J Pharmacol 2021; 179:1125-1145. [PMID: 34767248 DOI: 10.1111/bph.15724] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 09/13/2021] [Accepted: 10/18/2021] [Indexed: 12/01/2022] Open
Abstract
Fungal infections cause serious problems in many aspects of human life, in particular infections in immunocompromised patients represent serious problems. Current antifungal antibiotics target various metabolic pathways, predominantly the cell wall or cellular membrane. Numerous compounds are available to combat fungal infections, but their efficacy is far from being satisfactory and some of them display high toxicity. The emerging resistance represents a serious issue as well; hence, there is a considerable need for new anti-fungal compounds with lower toxicity and higher effectiveness. One of the unique antifungal antibiotics is sordarin, the only known compound that acts on the fungal translational machinery per se. Sordarin inhibits protein synthesis at the elongation step of the translational cycle, acting on eukaryotic translation elongation factor 2. In this review, we intend to deliver a robust scientific platform promoting the development of antifungal compounds, in particular focusing on the molecular action of sordarin.
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Affiliation(s)
- Yutian Shao
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, PR China.,Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Eliza Molestak
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
| | - Weike Su
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, PR China.,National Engineering Research Center for Process Development of Active Pharmaceutical Ingredients, Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, PR China.,Key Laboratory for Green Pharmaceutical Technologies and Related Equipment of Ministry of Education, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou, PR China
| | - Marek Stankevič
- Department of Organic Chemistry, Institute of Chemical Sciences, Faculty of Chemistry, Maria Curie Sklodowska University, Lublin, Poland
| | - Marek Tchórzewski
- Department of Molecular Biology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Lublin, Poland
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3
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Méndez-Godoy A, García-Montalvo D, Martínez-Castilla LP, Sánchez-Puig N. Evolutionary and functional relationships in the ribosome biogenesis SBDS and EFL1 protein families. Mol Genet Genomics 2021; 296:1263-1278. [PMID: 34453201 DOI: 10.1007/s00438-021-01814-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 08/15/2021] [Indexed: 11/25/2022]
Abstract
Nascent ribosomal 60S subunits undergo the last maturation steps in the cytoplasm. The last one involves removing the anti-association factor eIF6 from the 60S ribosomal surface by the joint action of the Elongation Factor-like 1 (EFL1) GTPase and the SBDS protein. Herein, we studied the evolutionary relationship of the EFL1 and EF-2 protein families and the functional conservation within EFL1 orthologues. Phylogenetic analysis demonstrated that the EFL1 proteins are exclusive of eukaryotes and share an evolutionary origin with the EF-2 and EF-G protein families. EFL1 proteins originated by gene duplication from the EF-2 proteins and specialized in ribosome maturation while the latter retained their function in translation. Some organisms have more than one EFL1 protein resulting from alternative splicing, while others are encoded in different genes originated by gene duplication. However, the function of these alternative EFL1 proteins is still unknown. We performed GTPase activity and complementation assays to study the functional conservation of EFL1 homologs alone and together with their SBDS counterparts. None of the orthologues or cross-species combinations could replace the function of the corresponding yeast EFL1•SBDS binomial. The complementation of SBDS interspecies chimeras indicates that domain 2 is vital for its function together with EFL1 and the 60S subunit. The results suggest a functional species-specificity and possible co-evolution between EFL1, SBDS, and the 60S ribosomal subunit. These findings set the basis for further studies directed to understand the molecular evolution of these proteins and their impact on ribosome biogenesis and disease.
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Affiliation(s)
- Alfonso Méndez-Godoy
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Ciudad de México, 04510, México.,Unit of Biochemistry, Department of Biology, University of Fribourg, 1700, Fribourg, Switzerland
| | - Daniel García-Montalvo
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Ciudad de México, 04510, México
| | - León P Martínez-Castilla
- Departamento de Ciencias Naturales, Unidad Cuajimalpa, Universidad Autónoma Metropolitana, Ciudad de México, México
| | - Nuria Sánchez-Puig
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Ciudad de México, 04510, México.
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4
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Ranjan N, Pochopien AA, Chih-Chien Wu C, Beckert B, Blanchet S, Green R, V Rodnina M, Wilson DN. Yeast translation elongation factor eEF3 promotes late stages of tRNA translocation. EMBO J 2021; 40:e106449. [PMID: 33555093 PMCID: PMC7957392 DOI: 10.15252/embj.2020106449] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 12/10/2020] [Accepted: 12/21/2020] [Indexed: 11/21/2022] Open
Abstract
In addition to the conserved translation elongation factors eEF1A and eEF2, fungi require a third essential elongation factor, eEF3. While eEF3 has been implicated in tRNA binding and release at the ribosomal A and E sites, its exact mechanism of action is unclear. Here, we show that eEF3 acts at the mRNA–tRNA translocation step by promoting the dissociation of the tRNA from the E site, but independent of aminoacyl‐tRNA recruitment to the A site. Depletion of eEF3 in vivo leads to a general slowdown in translation elongation due to accumulation of ribosomes with an occupied A site. Cryo‐EM analysis of native eEF3‐ribosome complexes shows that eEF3 facilitates late steps of translocation by favoring non‐rotated ribosomal states, as well as by opening the L1 stalk to release the E‐site tRNA. Additionally, our analysis provides structural insights into novel translation elongation states, enabling presentation of a revised yeast translation elongation cycle.
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Affiliation(s)
- Namit Ranjan
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Agnieszka A Pochopien
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Munich, Germany.,Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Colin Chih-Chien Wu
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Bertrand Beckert
- Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Sandra Blanchet
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Daniel N Wilson
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Munich, Germany.,Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
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5
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Yang HW, Kim HD, Kim TS, Kim J. Senescent Cells Differentially Translate Senescence-Related mRNAs Via Ribosome Heterogeneity. J Gerontol A Biol Sci Med Sci 2020; 74:1015-1024. [PMID: 30285098 DOI: 10.1093/gerona/gly228] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Indexed: 12/15/2022] Open
Abstract
The ribosome has a lateral stalk which consists of rpLP0, rpLP1, and rpLP2. One of these proteins, rpLP2, is decreased in translating ribosome when cellular senescence is induced. Y-box binding protein-1 (YB-1) is also reduced in polysomal fraction of senescent cells. We discovered that rpLP2 depletion in the ribosome can cause the detachment of YB-1 in polysomes and that it is linked to cellular senescence. Our results also revealed that a decrement of CK2α or GRK2 in senescent cells induced an increment of unphosphorylated rpLP2, resulting in release of YB-1 from polysomes. This heterogeneous senescent ribosome has different translational efficiencies for some senescence-related genes. We also showed that the decrease of rpLP1/rpLP2 and YB-1 in senescent ribosomes was not specific to cell type or stress type and the same phenomenon was also observed in aged mouse livers regardless of gender. Taken together, our results suggest that the senescent ribosome complex appears to have low levels of rpLP1/rpLP2 and YB-1, resulting in altered translational efficiency for senescence-related genes.
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Affiliation(s)
- Hee Woong Yang
- Laboratory of Biochemistry, Division of Life Sciences, Korea University, Seoul, Republic of Korea
| | - Hag Dong Kim
- Laboratory of Biochemistry, Division of Life Sciences, Korea University, Seoul, Republic of Korea.,HAEL Lab, TechnoComplex Building, Korea University, Seoul, Republic of Korea
| | - Tae-Sung Kim
- Laboratory of Biochemistry, Division of Life Sciences, Korea University, Seoul, Republic of Korea
| | - Joon Kim
- Laboratory of Biochemistry, Division of Life Sciences, Korea University, Seoul, Republic of Korea.,HAEL Lab, TechnoComplex Building, Korea University, Seoul, Republic of Korea
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6
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Dörfer M, Heine D, König S, Gore S, Werz O, Hertweck C, Gressler M, Hoffmeister D. Melleolides impact fungal translation via elongation factor 2. Org Biomol Chem 2019; 17:4906-4916. [PMID: 31042251 DOI: 10.1039/c9ob00562e] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2023]
Abstract
Melleolides from the honey mushroom Armillaria mellea represent a structurally diverse group of polyketide-sesquiterpene hybrids. Among various bioactivites, melleolides show antifungal effects against Aspergillus and other fungi. This bioactivity depends on a Δ2,4-double bond present in dihydroarmillylorsellinate (DAO) or arnamial, for example. Yet, the mode of action of Δ2,4-unsaturated, antifungal melleolides has been unknown. Here, we report on the molecular target of DAO in the fungus Aspergillus nidulans. Using a combination of synthetic chemistry to create a DAO-labelled probe, protein pulldown assays, MALDI-TOF-based peptide analysis and western blotting, we identify the eukaryotic translation elongation factor 2 (eEF2) as a binding partner of DAO. We confirm the inhibition of protein biosynthesis in vivo with an engineered A. nidulans strain producing the red fluorescent protein mCherry. Our work suggests a binding site dissimilar from that of the protein biosynthesis inhibitor sordarin, and highlights translational elongation as a valid antifungal drug target.
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Affiliation(s)
- Maximilian Dörfer
- Department Pharmaceutical Microbiology at the Hans Knöll Institute, Friedrich-Schiller-University, Beutenbergstrasse 11a, 07745 Jena, Germany.
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7
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Li W, Agrawal RK. Joachim Frank's Binding with the Ribosome. Structure 2019; 27:411-419. [PMID: 30595455 PMCID: PMC11062599 DOI: 10.1016/j.str.2018.11.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Revised: 11/09/2018] [Accepted: 11/15/2018] [Indexed: 01/03/2023]
Abstract
With recent technological advancements, single-particle cryogenic electron microscopy (cryo-EM) is now the technique of choice to study structure and function of biological macromolecules at near-atomic resolution. Many single-particle EM reconstruction methods necessary for these advances were pioneered by Joachim Frank, and were optimized using the ribosome as a benchmark specimen. In doing so, he made several landmark contributions to the understanding of the structure and function of ribosomes. These include the first 3D visualization of ribosome-bound transfer RNAs, the first experimentally derived structures of the primary complexes formed during the bacterial translation elongation cycle, and the critical ribosomal conformational transitions required for translation. Over the years, his laboratory studied many important functional complexes of the ribosome from both eubacterial and eukaryotic systems, including ribosomes from pathogenic organisms. This article presents a brief account of the contributions made by Joachim Frank to the ribosome field.
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Affiliation(s)
- Wen Li
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA.
| | - Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA; Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, NY, USA.
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8
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Himes BA, Zhang P. emClarity: software for high-resolution cryo-electron tomography and subtomogram averaging. Nat Methods 2018; 15:955-961. [PMID: 30349041 PMCID: PMC6281437 DOI: 10.1038/s41592-018-0167-z] [Citation(s) in RCA: 158] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 07/25/2018] [Indexed: 11/17/2022]
Abstract
Macromolecular complexes are intrinsically flexible and often challenging to purify for structure determination by single particle cryoEM. Such complexes may be studied using cryo-electron tomography combined with sub-tomogram alignment and classification, which in exceptional cases reaches sub-nanometer resolution, yielding insight into structure-function relationships. Extending this approach to specimens that exhibit conformational or compositional heterogeneity, and that may be present at low abundance, remains challenging. To address this challenge, we developed emClarity (https://github.com/bHimes/emClarity/wiki), a GPU-accelerated image processing package, which features an iterative tomographic tilt-series refinement algorithm using sub-tomograms as fiducial markers and a 3D-samping function compensated, multi-scale Principle Component Analysis classification method. We demonstrate substantial improvements in the resolution of maps and in the separation of different functional states of macromolecular complexes, compared to those generated using current state-of-the-art software.
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Affiliation(s)
- Benjamin A Himes
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.,Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Peijun Zhang
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. .,Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK. .,Electron Bio-Imaging Centre, Diamond Light Source, Didcot, UK.
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9
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Mailliot J, Martin F. Viral internal ribosomal entry sites: four classes for one goal. WILEY INTERDISCIPLINARY REVIEWS. RNA 2018; 9. [PMID: 29193740 DOI: 10.1002/wrna.1458] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 09/19/2017] [Accepted: 10/02/2017] [Indexed: 12/22/2022]
Abstract
To ensure efficient propagation, viruses need to rapidly produce viral proteins after cell entrance. Since viral genomes do not encode any components of the protein biosynthesis machinery, viral proteins must be produced by the host cell. To hi-jack the host cellular translation, viruses use a great variety of distinct strategies. Many single-stranded positive-sensed RNA viruses contain so-called internal ribosome entry sites (IRESs). IRESs are structural RNA motifs that have evolved to specific folds that recruit the host ribosomes on the viral coding sequences in order to synthesize viral proteins. In host canonical translation, recruitment of the translation machinery components is essentially guided by the 5' cap (m7 G) of mRNA. In contrast, IRESs are able to promote efficient ribosome assembly internally and in cap-independent manner. IRESs have been categorized into four classes, based on their length, nucleotide sequence, secondary and tertiary structures, as well as their mode of action. Classes I and II require the assistance of cellular auxiliary factors, the eukaryotic intiation factors (eIF), for efficient ribosome assembly. Class III IRESs require only a subset of eIFs whereas Class IV, which are the more compact, can promote translation without any eIFs. Extensive functional and structural investigations of IRESs over the past decades have allowed a better understanding of their mode of action for viral translation. Because viral translation has a pivotal role in the infectious program, IRESs are therefore attractive targets for therapeutic purposes. WIREs RNA 2018, 9:e1458. doi: 10.1002/wrna.1458 This article is categorized under: Translation > Ribosome Structure/Function Translation > Translation Mechanisms RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.
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Affiliation(s)
- Justine Mailliot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR7104, INSERM U964, Illkirch-Graffenstaden, France
| | - Franck Martin
- Institut de Biologie Moléculaire et Cellulaire, "Architecture et Réactivité de l'ARN" CNRS UPR9002, Université De Strasbourg, Strasbourg, France
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10
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Johnson AG, Grosely R, Petrov AN, Puglisi JD. Dynamics of IRES-mediated translation. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0177. [PMID: 28138065 DOI: 10.1098/rstb.2016.0177] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 12/19/2022] Open
Abstract
Viral internal ribosome entry sites (IRESs) are unique RNA elements, which use stable and dynamic RNA structures to recruit ribosomes and drive protein synthesis. IRESs overcome the high complexity of the canonical eukaryotic translation initiation pathway, often functioning with a limited set of eukaryotic initiation factors. The simplest types of IRESs are typified by the cricket paralysis virus intergenic region (CrPV IGR) and hepatitis C virus (HCV) IRESs, both of which independently form high-affinity complexes with the small (40S) ribosomal subunit and bypass the molecular processes of cap-binding and scanning. Owing to their simplicity and ribosomal affinity, the CrPV and HCV IRES have been important models for structural and functional studies of the eukaryotic ribosome during initiation, serving as excellent targets for recent technological breakthroughs in cryogenic electron microscopy (cryo-EM) and single-molecule analysis. High-resolution structural models of ribosome : IRES complexes, coupled with dynamics studies, have clarified decades of biochemical research and provided an outline of the conformational and compositional trajectory of the ribosome during initiation. Here we review recent progress in the study of HCV- and CrPV-type IRESs, highlighting important structural and dynamics insights and the synergy between cryo-EM and single-molecule studies.This article is part of the themed issue 'Perspectives on the ribosome'.
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Affiliation(s)
- Alex G Johnson
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Alexey N Petrov
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
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11
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Recurring RNA structural motifs underlie the mechanics of L1 stalk movement. Nat Commun 2017; 8:14285. [PMID: 28176782 PMCID: PMC5309774 DOI: 10.1038/ncomms14285] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 12/15/2016] [Indexed: 01/19/2023] Open
Abstract
The L1 stalk of the large ribosomal subunit undergoes large-scale movements coupled to the translocation of deacylated tRNA during protein synthesis. We use quantitative comparative structural analysis to localize the origins of L1 stalk movement and to understand its dynamic interactions with tRNA and other structural elements of the ribosome. Besides its stacking interactions with the tRNA elbow, stalk movement is directly linked to intersubunit rotation, rotation of the 30S head domain and contact of the acceptor arm of deacylated tRNA with helix 68 of 23S rRNA. Movement originates from pivoting at stacked non-canonical base pairs in a Family A three-way junction and bending in an internal G-U-rich zone. Use of these same motifs as hinge points to enable such dynamic events as rotation of the 30S subunit head domain and in flexing of the anticodon arm of tRNA suggests that they represent general strategies for movement of functional RNAs. Translocation of the tRNA on the ribosome is associated with large-scale molecular movements of the ribosomal L1 stalk. Here the authors identify the key determinants that allow these dramatic movements, and suggest they represent general strategies used to enable large-scale motions in functional RNAs.
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12
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Wawiórka L, Molestak E, Szajwaj M, Michalec-Wawiórka B, Boguszewska A, Borkiewicz L, Liudkovska V, Kufel J, Tchórzewski M. Functional analysis of the uL11 protein impact on translational machinery. Cell Cycle 2017; 15:1060-72. [PMID: 26939941 DOI: 10.1080/15384101.2016.1154245] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The ribosomal GTPase associated center constitutes the ribosomal area, which is the landing platform for translational GTPases and stimulates their hydrolytic activity. The ribosomal stalk represents a landmark structure in this center, and in eukaryotes is composed of uL11, uL10 and P1/P2 proteins. The modus operandi of the uL11 protein has not been exhaustively studied in vivo neither in prokaryotic nor in eukaryotic cells. Using a yeast model, we have brought functional insight into the translational apparatus deprived of uL11, filling the gap between structural and biochemical studies. We show that the uL11 is an important element in various aspects of 'ribosomal life'. uL11 is involved in 'birth' (biogenesis and initiation), by taking part in Tif6 release and contributing to ribosomal subunit-joining at the initiation step of translation. uL11 is particularly engaged in the 'active life' of the ribosome, in elongation, being responsible for the interplay with eEF1A and fidelity of translation and contributing to a lesser extent to eEF2-dependent translocation. Our results define the uL11 protein as a critical GAC element universally involved in trGTPase 'productive state' stabilization, being primarily a part of the ribosomal element allosterically contributing to the fidelity of the decoding event.
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Affiliation(s)
- Leszek Wawiórka
- a Department of Molecular Biology , Maria Curie-Skłodowska University , Lublin , Poland
| | - Eliza Molestak
- a Department of Molecular Biology , Maria Curie-Skłodowska University , Lublin , Poland
| | - Monika Szajwaj
- a Department of Molecular Biology , Maria Curie-Skłodowska University , Lublin , Poland
| | | | | | - Lidia Borkiewicz
- a Department of Molecular Biology , Maria Curie-Skłodowska University , Lublin , Poland
| | - Vladyslava Liudkovska
- b Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw , Warsaw , Poland
| | - Joanna Kufel
- b Institute of Genetics and Biotechnology, Faculty of Biology, University of Warsaw , Warsaw , Poland
| | - Marek Tchórzewski
- a Department of Molecular Biology , Maria Curie-Skłodowska University , Lublin , Poland
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13
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Billod JM, Saenz-Mendez P, Blomberg A, Eriksson LA. Structures, Properties, and Dynamics of Intermediates in eEF2-Diphthamide Biosynthesis. J Chem Inf Model 2016; 56:1776-86. [PMID: 27525663 DOI: 10.1021/acs.jcim.6b00223] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The eukaryotic translation Elongation Factor 2 (eEF2) is an essential enzyme in protein synthesis. eEF2 contains a unique modification of a histidine (His699 in yeast; HIS) into diphthamide (DTA), obtained via 3-amino-3-carboxypropyl (ACP) and diphthine (DTI) intermediates in the biosynthetic pathway. This essential and unique modification is also vulnerable, in that it can be efficiently targeted by NAD(+)-dependent ADP-ribosylase toxins, such as diphtheria toxin (DT). However, none of the intermediates in the biosynthesis path is equally vulnerable against the toxins. This study aims to address the different susceptibility of DTA and its precursors against bacterial toxins. We have herein undertaken a detailed in silico study of the structural features and dynamic motion of different His699 intermediates along the diphthamide synthesis pathway (HIS, ACP, DTI, DTA). The study points out that DTA forms a strong hydrogen bond with an asparagine which might explain the ADP-ribosylation mechanism caused by the diphtheria toxin (DT). Finally, in silico mutagenesis studies were performed on the DTA modified protein, in order to hamper the formation of such a hydrogen bond. The results indicate that the mutant structure might in fact be less susceptible to attack by DT and thereby behave similarly to DTI in this respect.
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Affiliation(s)
- Jean-Marc Billod
- Department of Chemical and Physical Biology, Center for Biological Research, CIB-CSIC , 28040 Madrid, Spain
| | - Patricia Saenz-Mendez
- Computational Chemistry and Biology Group, Facultad de Química, Universidad de la República , 11800 Montevideo, Uruguay
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Garcia-Esparcia P, Hernández-Ortega K, Koneti A, Gil L, Delgado-Morales R, Castaño E, Carmona M, Ferrer I. Altered machinery of protein synthesis is region- and stage-dependent and is associated with α-synuclein oligomers in Parkinson's disease. Acta Neuropathol Commun 2015; 3:76. [PMID: 26621506 PMCID: PMC4666041 DOI: 10.1186/s40478-015-0257-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/14/2015] [Indexed: 01/17/2023] Open
Abstract
INTRODUCTION Parkinson's disease (PD) is characterized by the accumulation of abnormal α-synuclein in selected regions of the brain following a gradient of severity with disease progression. Whether this is accompanied by globally altered protein synthesis is poorly documented. The present study was carried out in PD stages 1-6 of Braak and middle-aged (MA) individuals without alterations in brain in the substantia nigra, frontal cortex area 8, angular gyrus, precuneus and putamen. RESULTS Reduced mRNA expression of nucleolar proteins nucleolin (NCL), nucleophosmin (NPM1), nucleoplasmin 3 (NPM3) and upstream binding transcription factor (UBF), decreased NPM1 but not NPM3 nucleolar protein immunostaining in remaining neurons; diminished 18S rRNA, 28S rRNA; reduced expression of several mRNAs encoding ribosomal protein (RP) subunits; and altered protein levels of initiation factor eIF3 and elongation factor eEF2 of protein synthesis was found in the substantia nigra in PD along with disease progression. Although many of these changes can be related to neuron loss in the substantia nigra, selective alteration of certain factors indicates variable degree of vulnerability of mRNAs, rRNAs and proteins in degenerating sustantia nigra. NPM1 mRNA and 18S rRNA was increased in the frontal cortex area 8 at stage 5-6; modifications were less marked and region-dependent in the angular gyrus and precuneus. Several RPs were abnormally regulated in the frontal cortex area 8 and precuneus, but only one RP in the angular gyrus, in PD. Altered levels of eIF3 and eIF1, and decrease eEF1A and eEF2 protein levels were observed in the frontal cortex in PD. No modifications were found in the putamen at any time of the study except transient modifications in 28S rRNA and only one RP mRNA at stages 5-6. These observations further indicate marked region-dependent and stage-dependent alterations in the cerebral cortex in PD. Altered solubility and α-synuclein oligomer formation, assessed in total homogenate fractions blotted with anti-α-synuclein oligomer-specific antibody, was demonstrated in the substantia nigra and frontal cortex, but not in the putamen, in PD. Dramatic increase in α-synuclein oligomers was also seen in fluorescent-activated cell sorter (FACS)-isolated nuclei in the frontal cortex in PD. CONCLUSIONS Altered machinery of protein synthesis is altered in the substantia nigra and cerebral cortex in PD being the frontal cortex area 8 more affected than the angular gyrus and precuneus; in contrast, pathways of protein synthesis are apparently preserved in the putamen. This is associated with the presence of α-synuclein oligomeric species in total homogenates; substantia nigra and frontal cortex are enriched, albeit with different band patterns, in α-synuclein oligomeric species, whereas α-synuclein oligomers are not detected in the putamen.
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Affiliation(s)
- Paula Garcia-Esparcia
- Institute of Neuropathology, Bellvitge University Hospital, University of Barcelona, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat; Biomedical Research Center of Neurodegenerative Diseases (CIBERNED), Barcelona, Spain
| | - Karina Hernández-Ortega
- Institute of Neuropathology, Bellvitge University Hospital, University of Barcelona, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat; Biomedical Research Center of Neurodegenerative Diseases (CIBERNED), Barcelona, Spain
| | - Anusha Koneti
- Institute of Neuropathology, Bellvitge University Hospital, University of Barcelona, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat; Biomedical Research Center of Neurodegenerative Diseases (CIBERNED), Barcelona, Spain
| | - Laura Gil
- Department of Genetics, Medical School, Alfonso X el Sabio University, Villanueva de la Cañada, Madrid, Spain
| | - Raul Delgado-Morales
- Cancer Epigenetics and Biology Program, IDIBELL, Hospitalet de Llobregat, Barcelona, Spain
| | - Ester Castaño
- Biology-Bellvitge Unit, Scientific and Technological Centers-University of Barcelona (CCiTUB), Hospitalet de Llobregat, Barcelona, Spain
| | - Margarita Carmona
- Institute of Neuropathology, Bellvitge University Hospital, University of Barcelona, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat; Biomedical Research Center of Neurodegenerative Diseases (CIBERNED), Barcelona, Spain
| | - Isidre Ferrer
- Institute of Neuropathology, Bellvitge University Hospital, University of Barcelona, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat; Biomedical Research Center of Neurodegenerative Diseases (CIBERNED), Barcelona, Spain.
- Institute of Neuropathology, Service of Pathologic Anatomy, Bellvitge University Hospital, carrer Feixa Llarga s/n, 08907, Hospitalet de Llobregat, Spain.
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15
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Abstract
BACKGROUND During protein synthesis, the nascent peptide chain emerges from the ribosome through the ribosomal exit tunnel. Biochemical interactions between the nascent peptide and the tunnel may stall the ribosome movement and thus affect the expression level of the protein being synthesized. Earlier studies focused on one model organism (S. cerevisiae), have suggested that certain amino acid sequences may be responsible for ribosome stalling; however, the stalling effect at the individual amino acid level across many organisms has not yet been quantified. RESULTS By analyzing multiple ribosome profiling datasets from different organisms (including prokaryotes and eukaryotes), we report for the first time the organism-specific amino acids that significantly lead to ribosome stalling. We show that the identity of the stalling amino acids vary across the tree of life. In agreement with previous studies, we observed a remarkable stalling signal of proline and arginine in S. cerevisiae. In addition, our analysis supports the conjecture that the stalling effect of positively charged amino acids is not universal and that in certain conditions, negative charge may also induce ribosome stalling. Finally, we show that the beginning part of the tunnel tends to undergo more interactions with the translated amino acids than other positions along the tunnel. CONCLUSIONS The reported results support the conjecture that the ribosomal exit tunnel interacts with various amino acids and that the nature of these interactions varies among different organisms. Our findings should contribute towards better understanding of transcript and proteomic evolution and translation elongation regulation.
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Affiliation(s)
- Renana Sabi
- Department of Biomedical Engineering, Tel Aviv University (TAU), Tel Aviv, Israel
| | - Tamir Tuller
- Department of Biomedical Engineering, Tel Aviv University (TAU), Tel Aviv, Israel
- The Sagol School of Neuroscience, Tel-Aviv University (TAU), Tel-Aviv, Israel
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16
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Studying the properties of domain I of the ribosomal protein l1: incorporation into ribosome and regulation of the l1 operon expression. Protein J 2015; 34:103-10. [PMID: 25681234 DOI: 10.1007/s10930-015-9602-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
L1 is a conserved protein of the large ribosomal subunit. This protein binds strongly to the specific region of the high molecular weight rRNA of the large ribosomal subunit, thus forming a conserved flexible structural element--the L1 stalk. L1 protein also regulates translation of the operon that comprises its own gene. Crystallographic data suggest that L1 interacts with RNA mainly by means of its domain I. We show here for the first time that the isolated domain I of the bacterial protein L1 of Thermus thermophilus and Escherichia coli is able to incorporate in vivo into the E. coli ribosome. Furthermore, domain I of T. thermophilus L1 can regulate expression of the L1 gene operon of Archaea in the coupled transcription-translation system in vitro, as well as the intact protein. We have identified the structural elements of domain I of the L1 protein that may be responsible for its regulatory properties.
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17
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Bousset L, Mary C, Brooks MA, Scherrer A, Strub K, Cusack S. Crystal structure of a signal recognition particle Alu domain in the elongation arrest conformation. RNA (NEW YORK, N.Y.) 2014; 20:1955-1962. [PMID: 25336584 PMCID: PMC4238359 DOI: 10.1261/rna.047209.114] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2014] [Accepted: 09/04/2014] [Indexed: 06/04/2023]
Abstract
The signal recognition particle (SRP) is a conserved ribonucleoprotein particle that targets membrane and secreted proteins to translocation channels in membranes. In eukaryotes, the Alu domain, which comprises the 5' and 3' extremities of the SRP RNA bound to the SRP9/14 heterodimer, is thought to interact with the ribosome to pause translation elongation during membrane docking. We present the 3.2 Å resolution crystal structure of a chimeric Alu domain, comprising Alu RNA from the archaeon Pyrococcus horikoshii bound to the human Alu binding proteins SRP9/14. The structure reveals how intricate tertiary interactions stabilize the RNA 5' domain structure and how an extra, archaeal-specific, terminal stem helps constrain the Alu RNA into the active closed conformation. In this conformation, highly conserved noncanonical base pairs allow unusually tight side-by-side packing of 5' and 3' RNA stems within the SRP9/14 RNA binding surface. The biological relevance of this structure is confirmed by showing that a reconstituted full-length chimeric archaeal-human SRP is competent to elicit elongation arrest in vitro. The structure will be useful in refining our understanding of how the SRP Alu domain interacts with the ribosome.
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Affiliation(s)
- Luc Bousset
- European Molecular Biology Laboratory, Grenoble Outstation, 38042 Grenoble Cedex 9, France
| | - Camille Mary
- Département de Biologie Cellulaire, Université de Genève, Sciences III, 1211 Geneva 4, Switzerland
| | - Mark A Brooks
- European Molecular Biology Laboratory, Grenoble Outstation, 38042 Grenoble Cedex 9, France
| | - Anne Scherrer
- Département de Biologie Cellulaire, Université de Genève, Sciences III, 1211 Geneva 4, Switzerland
| | - Katharina Strub
- Département de Biologie Cellulaire, Université de Genève, Sciences III, 1211 Geneva 4, Switzerland
| | - Stephen Cusack
- European Molecular Biology Laboratory, Grenoble Outstation, 38042 Grenoble Cedex 9, France
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18
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Perucho L, Artero-Castro A, Guerrero S, Ramón y Cajal S, LLeonart ME, Wang ZQ. RPLP1, a crucial ribosomal protein for embryonic development of the nervous system. PLoS One 2014; 9:e99956. [PMID: 24959908 PMCID: PMC4069005 DOI: 10.1371/journal.pone.0099956] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Accepted: 05/20/2014] [Indexed: 12/22/2022] Open
Abstract
Ribosomal proteins are pivotal to development and tissue homeostasis. RP Large P1 (Rplp1) overexpression is associated with tumorigenesis. However, the physiological function of Rplp1 in mammalian development remains unknown. In this study, we disrupted Rplp1 in the mouse germline and central nervous system (Rplp1CNSΔ). Rplp1 heterozygosity caused body size reductions, male infertility, systemic abnormalities in various tissues and a high frequency of early postnatal death. Rplp1CNSΔ</emph> newborn mice exhibited perinatal lethality and brain atrophy with size reductions of the neocortex, midbrain and ganglionic eminence. The Rplp1 knockout neocortex exhibited progenitor cell proliferation arrest and apoptosis due to the dysregulation of key cell cycle and apoptosis regulators (cyclin A, cyclin E, p21CIP1, p27KIP1, p53). Similarly, Rplp1 deletion in pMEFs led to proliferation arrest and premature senescence. Importantly, Rplp1 deletion in primary mouse embryonic fibroblasts did not alter global protein synthesis, but did change the expression patterns of specific protein subsets involved in protein folding and the unfolded protein response, cell death, protein transport and signal transduction, among others. Altogether, we demonstrated that the translation “fine-tuning” exerted by Rplp1 is essential for embryonic and brain development and for proper cell proliferation.
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Affiliation(s)
- Laura Perucho
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Ana Artero-Castro
- Oncology and Pathology Group, Institut de Recerca Hospital Vall d'Hebron, Barcelona, Spain
| | - Sergi Guerrero
- Oncology and Pathology Group, Institut de Recerca Hospital Vall d'Hebron, Barcelona, Spain
| | - Santiago Ramón y Cajal
- Oncology and Pathology Group, Institut de Recerca Hospital Vall d'Hebron, Barcelona, Spain
| | - Matilde E. LLeonart
- Oncology and Pathology Group, Institut de Recerca Hospital Vall d'Hebron, Barcelona, Spain
- * E-mail:
| | - Zhao-Qi Wang
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
- Faculty of Biology and Pharmacy, Friedrich Schiller University of Jena, Jena, Germany
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Chen KC, Xie H, Cai Y. Modes of action of ADP-ribosylated elongation factor 2 in inhibiting the polypeptide elongation cycle: a modeling study. PLoS One 2013; 8:e66446. [PMID: 23861744 PMCID: PMC3704607 DOI: 10.1371/journal.pone.0066446] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Accepted: 05/05/2013] [Indexed: 11/19/2022] Open
Abstract
Despite the fact that ADP-ribosylation of eukaryotic elongation factor 2 (EF2) leads to inhibition of protein synthesis, the mechanism by which ADP-ribosylated EF2 (ADPR•EF2) causes this inhibition remains controversial. Here, we applied modeling approaches to investigate the consequences of various modes of ADPR•EF2 inhibitory actions on the two coupled processes, the polypeptide chain elongation and ADP-ribosylation of EF2. Modeling of experimental data indicates that ADPR•EF2 fully blocks the late-phase translocation of tRNAs; but the impairment in the translocation upstream process, mainly the GTP-dependent factor binding with the pretranslocation ribosome and/or the guanine nucleotide exchange in EF2, is responsible for the overall inhibition kinetics. The reduced ADPR•EF2-ribosome association spares the ribosome to bind and shield native EF2 against toxin attack, thereby deferring the inhibition of protein synthesis inhibition and inactivation of EF2. Minimum association with the ribosome also keeps ADPR•EF2 in an accessible state for toxins to catalyze the reverse reaction when nicotinamide becomes available. Our work underscores the importance of unveiling the interactions between ADPR•EF2 and the ribosome, and argues against that toxins inhibit protein synthesis through converting native EF2 to a competitive inhibitor to actively disable the ribosome.
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Affiliation(s)
- Kevin C Chen
- Multidisciplinary Research Center, Shantou University, Guangdong, China.
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20
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Chakraborty B, Mukherjee R, Sengupta J. Structural insights into the mechanism of translational inhibition by the fungicide sordarin. J Comput Aided Mol Des 2013; 27:173-84. [PMID: 23397219 DOI: 10.1007/s10822-013-9636-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 01/25/2013] [Indexed: 11/25/2022]
Abstract
The translational machinery has been found to be the target for a number of antibiotics. One such antibiotic sordarin selectively inhibits fungal translation by impairing the function of elongation factor 2 (eEF2) while being ineffective to higher eukaryotes. Surprisingly, sordarin is not even equally effective in impairing translation for all fungal species. The binding cavity of sordarin on eEF2 has been localized by X-ray crystallographic study and its unique specificity towards sordarin has been attributed to the species specific substitutions within a stretch of amino acids (sordarin specificity region, SSR) at the entrance of the cavity. In this study, we have analyzed the sordarin-binding cavity of eEF2 from different species both in isolated and ribosome-bound forms in order to decipher the mechanism of sordarin binding selectivity. Our results reveal that the molecular architecture as well as the microenvironment of the sordarin-binding cavity changes significantly from one species to another depending on the species specific substitutions within the cavity. Moreover, eEF2 binding to ribosome aggravates the effects of these substitutions. Thus, this study, while shedding light on the molecular mechanism underpinning the selective inhibitory effects of sordarin, will also be a helpful guide for future studies aiming at developing novel antifungal drugs with broader spectrum of activity.
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Affiliation(s)
- Biprashekhar Chakraborty
- Structural Biology and Bio-Informatics Division, Indian Institute of Chemical Biology (Council of Scientific and Industrial Research), 4, Raja S.C. Mullick Road, Kolkata 700 032, India
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21
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Mittal N, Subramanian G, Bütikofer P, Madhubala R. Unique posttranslational modifications in eukaryotic translation factors and their roles in protozoan parasite viability and pathogenesis. Mol Biochem Parasitol 2013; 187:21-31. [PMID: 23201129 DOI: 10.1016/j.molbiopara.2012.11.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 11/04/2012] [Accepted: 11/05/2012] [Indexed: 11/21/2022]
Abstract
Protozoan parasites are one of the major causes of diseases worldwide. The vector transmitted parasites exhibit complex life cycles involving interactions between humans, protozoa, and arthropods. In order to adapt themselves to the changing microenvironments, they have to undergo complex morphological and metabolic changes. These changes can be brought about by expressing a new pool of proteins in the cell or by modifying the existing repertoire of proteins via posttranslational modifications (PTMs). PTMs involve covalent modification and processing of proteins thereby modulating their functions. Some of these changes may involve PTMs of parasite proteins to help the parasite survive within the host and the vector. Out of many PTMs known, three are unique since they occur only on single proteins: ethanolamine phosphoglycerol (EPG) glutamate, hypusine and diphthamide. These modifications occur on eukaryotic elongation factor 1A (eEF1A), eukaryotic initiation factor 5A (eIF5A) and eukaryotic elongation factor 2 (eEF2), respectively. Interestingly, the proteins carrying these unique modifications are all involved in the elongation steps of translation. Here we review these unique PTMs, which are well conserved in protozoan parasites, and discuss their roles in viability and pathogenesis of parasites. Characterization of these modifications and studying their roles in physiology as well as pathogenesis will provide new insights in parasite biology, which may also help in developing new therapeutic interventions.
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Affiliation(s)
- Nimisha Mittal
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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22
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Fernández-Pevida A, Rodríguez-Galán O, Díaz-Quintana A, Kressler D, de la Cruz J. Yeast ribosomal protein L40 assembles late into precursor 60 S ribosomes and is required for their cytoplasmic maturation. J Biol Chem 2012; 287:38390-407. [PMID: 22995916 DOI: 10.1074/jbc.m112.400564] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most ribosomal proteins play important roles in ribosome biogenesis and function. Here, we have examined the contribution of the essential ribosomal protein L40 in these processes in the yeast Saccharomyces cerevisiae. Deletion of either the RPL40A or RPL40B gene and in vivo depletion of L40 impair 60 S ribosomal subunit biogenesis. Polysome profile analyses reveal the accumulation of half-mers and a moderate reduction in free 60 S ribosomal subunits. Pulse-chase, Northern blotting, and primer extension analyses in the L40-depleted strain clearly indicate that L40 is not strictly required for the precursor rRNA (pre-rRNA) processing reactions but contributes to optimal 27 SB pre-rRNA maturation. Moreover, depletion of L40 hinders the nucleo-cytoplasmic export of pre-60 S ribosomal particles. Importantly, all these defects most likely appear as the direct consequence of impaired Nmd3 and Rlp24 release from cytoplasmic pre-60 S ribosomal subunits and their inefficient recycling back into the nucle(ol)us. In agreement, we show that hemagglutinin epitope-tagged L40A assembles in the cytoplasm into almost mature pre-60 S ribosomal particles. Finally, we have identified that the hemagglutinin epitope-tagged L40A confers resistance to sordarin, a translation inhibitor that impairs the function of eukaryotic elongation factor 2, whereas the rpl40a and rpl40b null mutants are hypersensitive to this antibiotic. We conclude that L40 is assembled at a very late stage into pre-60 S ribosomal subunits and that its incorporation into 60 S ribosomal subunits is a prerequisite for subunit joining and may ensure proper functioning of the translocation process.
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Risler JK, Kenny AE, Palumbo RJ, Gamache ER, Curcio MJ. Host co-factors of the retrovirus-like transposon Ty1. Mob DNA 2012; 3:12. [PMID: 22856544 PMCID: PMC3522557 DOI: 10.1186/1759-8753-3-12] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 06/18/2012] [Indexed: 11/10/2022] Open
Abstract
UNLABELLED BACKGROUND Long-terminal repeat (LTR) retrotransposons have complex modes of mobility involving reverse transcription of their RNA genomes in cytoplasmic virus-like particles (VLPs) and integration of the cDNA copies into the host genome. The limited coding capacity of retrotransposons necessitates an extensive reliance on host co-factors; however, it has been challenging to identify co-factors that are required for endogenous retrotransposon mobility because retrotransposition is such a rare event. RESULTS To circumvent the low frequency of Ty1 LTR-retrotransposon mobility in Saccharomyces cerevisiae, we used iterative synthetic genetic array (SGA) analysis to isolate host mutations that reduce retrotransposition. Query strains that harbor a chromosomal Ty1his3AI reporter element and either the rtt101Δ or med1Δ mutation, both of which confer a hypertransposition phenotype, were mated to 4,847 haploid ORF deletion strains. Retrotransposition was measured in the double mutant progeny, and a set of 275 ORF deletions that suppress the hypertransposition phenotypes of both rtt101Δ and med1Δ were identified. The corresponding set of 275 retrotransposition host factors (RHFs) includes 45 previously identified Ty1 or Ty3 co-factors. More than half of the RHF genes have statistically robust human homologs (E < 1 x 10-10). The level of unintegrated Ty1 cDNA in 181 rhfΔ single mutants was altered <2-fold, suggesting that the corresponding co-factors stimulate retrotransposition at a step after cDNA synthesis. However, deletion of 43 RHF genes, including specific ribosomal protein and ribosome biogenesis genes and RNA degradation, modification and transport genes resulted in low Ty1 cDNA levels. The level of Ty1 Gag but not RNA was reduced in ribosome biogenesis mutants bud21Δ, hcr1Δ, loc1Δ, and puf6Δ. CONCLUSION Ty1 retrotransposition is dependent on multiple co-factors acting at different steps in the replication cycle. Human orthologs of these RHFs are potential, or in a few cases, presumptive HIV-1 co-factors in human cells. RHF genes whose absence results in decreased Ty1 cDNA include characterized RNA metabolism and modification genes, consistent with their having roles in early steps in retrotransposition such as expression, nuclear export, translation, localization, or packaging of Ty1 RNA. Our results suggest that Bud21, Hcr1, Loc1, and Puf6 promote efficient synthesis or stability of Ty1 Gag.
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Affiliation(s)
- Jenni K Risler
- Laboratory of Molecular Genetics, Wadsworth Center, Albany, NY, 12201, USA.
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24
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Solution structure of the natively assembled yeast ribosomal stalk determined by small-angle X-ray scattering. Biochem J 2012; 444:205-9. [DOI: 10.1042/bj20120115] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The ribosomal stalk of the 60S subunit has been shown to play a crucial role in all steps of protein synthesis, but its structure and exact molecular function remain an unanswered question. In the present study, we show the low-resolution models of the solution structure of the yeast ribosomal stalk, composed of five proteins, P0–(P1–P2)2. The model of the pentameric stalk complex determined by small-angle X-ray scattering reveals an elongated shape with a maximum length of 13 nm. The model displays three distinct lobes, which may correspond to the individual P1–P2 heterodimers anchored to the C-terminal domain of the P0 protein.
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25
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Becker T, Armache JP, Jarasch A, Anger AM, Villa E, Sieber H, Motaal BA, Mielke T, Berninghausen O, Beckmann R. Structure of the no-go mRNA decay complex Dom34-Hbs1 bound to a stalled 80S ribosome. Nat Struct Mol Biol 2011; 18:715-20. [PMID: 21623367 DOI: 10.1038/nsmb.2057] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Accepted: 03/15/2011] [Indexed: 11/09/2022]
Abstract
No-go decay (NGD) is a mRNA quality-control mechanism in eukaryotic cells that leads to degradation of mRNAs stalled during translational elongation. The key factors triggering NGD are Dom34 and Hbs1. We used cryo-EM to visualize NGD intermediates resulting from binding of the Dom34-Hbs1 complex to stalled ribosomes. At subnanometer resolution, all domains of Dom34 and Hbs1 were identified, allowing the docking of crystal structures and homology models. Moreover, the close structural similarity of Dom34 and Hbs1 to eukaryotic release factors (eRFs) enabled us to propose a model for the ribosome-bound eRF1-eRF3 complex. Collectively, our data provide structural insights into how stalled mRNA is recognized on the ribosome and how the eRF complex can simultaneously recognize stop codons and catalyze peptide release.
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Affiliation(s)
- Thomas Becker
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Munich, Germany.
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26
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Zhu X, Kim J, Su X, Lin H. Reconstitution of diphthine synthase activity in vitro. Biochemistry 2011; 49:9649-57. [PMID: 20873788 DOI: 10.1021/bi100812h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Diphthamide, the target of diphtheria toxin, is a unique posttranslational modification on eukaryotic and archaeal translation elongation factor 2 (EF2). Although diphthamide modification was discovered three decades ago, in vitro reconstitution of diphthamide biosynthesis using purified proteins has not been reported. The proposed biosynthesis pathway of diphthamide involves three steps. Our laboratory has recently showed that in Pyrococcus horikoshii (P. horikoshii), the first step uses a [4Fe-4S] enzyme PhDph2 to generate a 3-amino-3-carboxypropyl radical from S-adenosyl-L-methionine (SAM) to form a C−C bond. The second step is the trimethylation of an amino group to form the diphthine intermediate. This step is catalyzed by a methyltransferase called diphthine synthase or Dph5. Here we report the in vitro reconstitution of the second step using P. horikoshii Dph5 (PhDph5). Our results demonstrate that PhDph5 is sufficient to catalyze the mono-, di-, and trimethylation of P. horikoshii EF2 (PhEF2). Interestingly, the trimethylated product from the PhDph5-catalyzed reaction can easily eliminate the trimethylamino group. The potential implication of this unexpected finding on the diphthamide biosynthesis pathway is discussed.
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Affiliation(s)
- Xuling Zhu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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Towards a systems approach in the genetic analysis of archaea: Accelerating mutant construction and phenotypic analysis in Haloferax volcanii. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2010; 2010:426239. [PMID: 21234384 PMCID: PMC3017900 DOI: 10.1155/2010/426239] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 10/24/2010] [Indexed: 01/17/2023]
Abstract
With the availability of a genome sequence and increasingly sophisticated genetic tools, Haloferax volcanii is becoming a model for both Archaea and halophiles. In order for H. volcanii to reach a status equivalent to Escherichia coli, Bacillus subtilis, or Saccharomyces cerevisiae, a gene knockout collection needs to be constructed in order to identify the archaeal essential gene set and enable systematic phenotype screens. A streamlined gene-deletion protocol adapted for potential automation was implemented and used to generate 22 H. volcanii deletion strains and identify several potentially essential genes. These gene deletion mutants, generated in this and previous studies, were then analyzed in a high-throughput fashion to measure growth rates in different media and temperature conditions. We conclude that these high-throughput methods are suitable for a rapid investigation of an H. volcanii mutant library and suggest that they should form the basis of a larger genome-wide experiment.
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28
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Smulski CR, Longhi SA, Ayub MJ, Edreira MM, Simonetti L, Gómez KA, Basile JN, Chaloin O, Hoebeke J, Levin MJ. Interaction map of the Trypanosoma cruzi ribosomal P protein complex (stalk) and the elongation factor 2. J Mol Recognit 2010; 24:359-70. [PMID: 21360618 DOI: 10.1002/jmr.1089] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2010] [Revised: 08/12/2010] [Accepted: 08/12/2010] [Indexed: 11/06/2022]
Abstract
The large subunit of the eukaryotic ribosome possesses a long and protruding stalk formed by the ribosomal P proteins. This structure is involved in the translation step of protein synthesis through interaction with the elongation factor 2 (EF-2). The Trypanosoma cruzi stalk complex is composed of four proteins of about 11 kDa, TcP1α, TcP1β, TcP2α, TcP2β and a fifth TcP0 of about 34 kDa. In a previous work, a yeast two-hybrid (Y2H) protein-protein interaction map of T. cruzi ribosomal P proteins was generated. In order to gain new insight into the assembly of the stalk, a complete interaction map was generated by surface plasmon resonance (SPR) and the kinetics of each interaction was calculated. All previously detected interactions were confirmed and new interacting pairs were found, such as TcP1β-TcP2α and TcP1β-TcP2β. Moreover P2 but not P1 proteins were able to homo-oligomerize. In addition, the region comprising amino acids 210-270 on TcP0 was identified as the region interacting with P1/P2 proteins, using Y2H and SPR. The interaction domains on TcP2β were also mapped by SPR identifying two distinct regions. The assembly order of the pentameric complex was assessed by SPR showing the existence of a hierarchy in the association of the different P proteins forming the stalk. Finally, the TcEF-2 gene was identified, cloned, expressed and refolded. Using SPR analysis we showed that TcEF-2 bound with similar affinity to the four P1/P2 ribosomal P proteins of T. cruzi but with reduced affinity to TcP0.
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Affiliation(s)
- Cristian R Smulski
- Laboratorio de Biología Molecular de la Enfermedad de Chagas (LaBMECh), Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), National Research Council (CONICET), Buenos Aires, Argentina
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29
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Armache JP, Jarasch A, Anger AM, Villa E, Becker T, Bhushan S, Jossinet F, Habeck M, Dindar G, Franckenberg S, Marquez V, Mielke T, Thomm M, Berninghausen O, Beatrix B, Söding J, Westhof E, Wilson DN, Beckmann R. Localization of eukaryote-specific ribosomal proteins in a 5.5-Å cryo-EM map of the 80S eukaryotic ribosome. Proc Natl Acad Sci U S A 2010; 107:19754-9. [PMID: 20974910 PMCID: PMC2993421 DOI: 10.1073/pnas.1010005107] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Protein synthesis in all living organisms occurs on ribonucleoprotein particles, called ribosomes. Despite the universality of this process, eukaryotic ribosomes are significantly larger in size than their bacterial counterparts due in part to the presence of 80 r proteins rather than 54 in bacteria. Using cryoelectron microscopy reconstructions of a translating plant (Triticum aestivum) 80S ribosome at 5.5-Å resolution, together with a 6.1-Å map of a translating Saccharomyces cerevisiae 80S ribosome, we have localized and modeled 74/80 (92.5%) of the ribosomal proteins, encompassing 12 archaeal/eukaryote-specific small subunit proteins as well as the complete complement of the ribosomal proteins of the eukaryotic large subunit. Near-complete atomic models of the 80S ribosome provide insights into the structure, function, and evolution of the eukaryotic translational apparatus.
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Affiliation(s)
- Jean-Paul Armache
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Alexander Jarasch
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Andreas M. Anger
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Elizabeth Villa
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Thomas Becker
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Shashi Bhushan
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Fabrice Jossinet
- Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire du Centre National de la Recherche Scientifique, 15 Rue René Descartes, 67084 Strasbourg, France
| | - Michael Habeck
- Department of Empirical Inference, Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Spemannstrasse 35, 72076 Tübingen, Germany
| | - Gülcin Dindar
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Sibylle Franckenberg
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Viter Marquez
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Thorsten Mielke
- UltraStrukturNetzwerk, Max Planck Institute for Molecular Genetics, Ihnestrasse 73, 14195 Berlin, Germany
- Institut für Medizinische Physik und Biophysik, Charité, Ziegelstrasse 5-8, 10117 Berlin, Germany; and
| | - Michael Thomm
- Universität Regensburg, Lehrstuhl für Mikrobiologie, Universitätstrasse 31, 93053 Regensburg, Germany
| | - Otto Berninghausen
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Birgitta Beatrix
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Johannes Söding
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Eric Westhof
- Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire du Centre National de la Recherche Scientifique, 15 Rue René Descartes, 67084 Strasbourg, France
| | - Daniel N. Wilson
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
| | - Roland Beckmann
- Gene Center and Center for integrated Protein Science Munich, Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany
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Zhu X, Dzikovski B, Su X, Torelli AT, Zhang Y, Ealick SE, Freed JH, Lin H. Mechanistic understanding of Pyrococcus horikoshii Dph2, a [4Fe-4S] enzyme required for diphthamide biosynthesis. MOLECULAR BIOSYSTEMS 2010; 7:74-81. [PMID: 20931132 DOI: 10.1039/c0mb00076k] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Diphthamide, the target of diphtheria toxin, is a unique posttranslational modification on eukaryotic and archaeal translation elongation factor 2 (EF2). The proposed biosynthesis of diphthamide involves three steps and we have recently found that in Pyrococcus horikoshii (P. horikoshii), the first step uses an S-adenosyl-L-methionine (SAM)-dependent [4Fe-4S] enzyme, PhDph2, to catalyze the formation of a C-C bond. Crystal structure shows that PhDph2 is a homodimer and each monomer contains three conserved cysteine residues that can bind a [4Fe-4S] cluster. In the reduced state, the [4Fe-4S] cluster can provide one electron to reductively cleave the bound SAM molecule. However, different from classical radical SAM family of enzymes, biochemical evidence suggest that a 3-amino-3-carboxypropyl radical is generated in PhDph2. Here we present evidence supporting that the 3-amino-3-carboxypropyl radical does not undergo hydrogen abstraction reaction, which is observed for the deoxyadenosyl radical in classical radical SAM enzymes. Instead, the 3-amino-3-carboxypropyl radical is added to the imidazole ring in the pathway towards the formation of the product. Furthermore, our data suggest that the chemistry requires only one [4Fe-4S] cluster to be present in the PhDph2 dimer.
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Affiliation(s)
- Xuling Zhu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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31
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Abstract
Protein biosynthesis, or translation, occurs on the ribosome, a large RNA-protein assembly universally conserved in all forms of life. Over the last decade, structures of the small and large ribosomal subunits and of the intact ribosome have begun to reveal the molecular details of how the ribosome works. Both cryo-electron microscopy and X-ray crystallography continue to provide fresh insights into the mechanism of translation. In this review, we describe the most recent structural models of the bacterial ribosome that shed light on the movement of messenger RNA and transfer RNA on the ribosome after each peptide bond is formed, a process termed translocation. We also discuss recent structures that reveal the molecular basis for stop codon recognition during translation termination. Finally, we review recent advances in understanding how bacteria handle errors in both translocation and termination.
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Affiliation(s)
- Jack A Dunkle
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
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32
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Recognition of the amber UAG stop codon by release factor RF1. EMBO J 2010; 29:2577-85. [PMID: 20588254 DOI: 10.1038/emboj.2010.139] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Accepted: 05/28/2010] [Indexed: 11/08/2022] Open
Abstract
We report the crystal structure of a termination complex containing release factor RF1 bound to the 70S ribosome in response to an amber (UAG) codon at 3.6-A resolution. The amber codon is recognized in the 30S subunit-decoding centre directly by conserved elements of domain 2 of RF1, including T186 of the PVT motif. Together with earlier structures, the mechanisms of recognition of all three stop codons by release factors RF1 and RF2 can now be described. Our structure confirms that the backbone amide of Q230 of the universally conserved GGQ motif is positioned to contribute directly to the catalysis of the peptidyl-tRNA hydrolysis reaction through stabilization of the leaving group and/or transition state. We also observe synthetic-negative interactions between mutations in the switch loop of RF1 and in helix 69 of 23S rRNA, revealing that these structural features interact functionally in the termination process. These findings are consistent with our proposal that structural rearrangements of RF1 and RF2 are critical to accurate translation termination.
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33
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Diphthamide biosynthesis requires an organic radical generated by an iron-sulphur enzyme. Nature 2010; 465:891-6. [PMID: 20559380 PMCID: PMC3006227 DOI: 10.1038/nature09138] [Citation(s) in RCA: 158] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2009] [Accepted: 04/30/2010] [Indexed: 12/29/2022]
Abstract
Archaeal and eukaryotic translation elongation factor 2 contain a unique post-translationally modified histidine residue called diphthamide, which is the target of diphtheria toxin. The biosynthesis of diphthamide was proposed to involve three steps, with the first being the formation of a C-C bond between the histidine residue and the 3-amino-3-carboxypropyl group of S-adenosyl-l-methionine (SAM). However, further details of the biosynthesis remain unknown. Here we present structural and biochemical evidence showing that the first step of diphthamide biosynthesis in the archaeon Pyrococcus horikoshii uses a novel iron-sulphur-cluster enzyme, Dph2. Dph2 is a homodimer and each of its monomers can bind a [4Fe-4S] cluster. Biochemical data suggest that unlike the enzymes in the radical SAM superfamily, Dph2 does not form the canonical 5'-deoxyadenosyl radical. Instead, it breaks the C(gamma,Met)-S bond of SAM and generates a 3-amino-3-carboxypropyl radical. Our results suggest that P. horikoshii Dph2 represents a previously unknown, SAM-dependent, [4Fe-4S]-containing enzyme that catalyses unprecedented chemistry.
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34
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Wang WH, Palumbo AM, Tan YJ, Reid GE, Tepe JJ, Bruening ML. Identification of p65-Associated Phosphoproteins by Mass Spectrometry after On-Plate Phosphopeptide Enrichment Using Polymer-oxotitanium Films. J Proteome Res 2010; 9:3005-15. [DOI: 10.1021/pr901200m] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Wei-Han Wang
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Amanda M. Palumbo
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Yu-Jing Tan
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Gavin E. Reid
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Jetze J. Tepe
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
| | - Merlin L. Bruening
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824
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35
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Mary C, Scherrer A, Huck L, Lakkaraju AKK, Thomas Y, Johnson AE, Strub K. Residues in SRP9/14 essential for elongation arrest activity of the signal recognition particle define a positively charged functional domain on one side of the protein. RNA (NEW YORK, N.Y.) 2010; 16:969-79. [PMID: 20348448 PMCID: PMC2856890 DOI: 10.1261/rna.2040410] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The signal recognition particle (SRP) is a ubiquitous cytoplasmic ribonucleoprotein complex required for the cotranslational targeting of proteins to the endoplasmic reticulum (ER). In eukaryotes, SRP has to arrest the elongation of the nascent chains during targeting to ensure efficient translocation of the preprotein, and this function of SRP is dependent on SRP9/14. Here we present the results of a mutational study on the human protein h9/14 that identified and characterized regions and single residues essential for elongation arrest activity. Effects of the mutations were assessed both in cell-free translation/translocation assays and in cultured mammalian cells. We identified two patches of basic amino acid residues that are essential for activity, whereas the internal loop of SRP14 was found to be dispensable. One patch of important basic residues comprises the previously identified basic pentapetide KRDKK, which can be substituted by four lysines without loss of function. The other patch includes three lysines in the solvent-accessible alpha2 of h9. All essential residues are located in proximity in SRP9/14 and their basic character suggests that they serve as a positively charged platform for interactions with ribosomal RNA. In addition, they can all be lysines consistent with the hypothesis that they recognize their target(s) via electrostatic contacts, most likely with the phosphate backbone, as opposed to contacts with specific bases.
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Affiliation(s)
- Camille Mary
- Département de Biologie Cellulaire, Université de Genève, Sciences III, 1211 Genève 4, Switzerland
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36
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Lee KM, Yu CWH, Chan DSB, Chiu TYH, Zhu G, Sze KH, Shaw PC, Wong KB. Solution structure of the dimerization domain of ribosomal protein P2 provides insights for the structural organization of eukaryotic stalk. Nucleic Acids Res 2010; 38:5206-16. [PMID: 20385603 PMCID: PMC2926600 DOI: 10.1093/nar/gkq231] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The lateral stalk of ribosome is responsible for kingdom-specific binding of translation factors and activation of GTP hydrolysis that drives protein synthesis. In eukaryotes, the stalk is composed of acidic ribosomal proteins P0, P1 and P2 that constitute a pentameric P-complex in 1: 2: 2 ratio. We have determined the solution structure of the N-terminal dimerization domain of human P2 (NTD-P2), which provides insights into the structural organization of the eukaryotic stalk. Our structure revealed that eukaryotic stalk protein P2 forms a symmetric homodimer in solution, and is structurally distinct from the bacterial counterpart L12 homodimer. The two subunits of NTD-P2 form extensive hydrophobic interactions in the dimeric interface that buries 2400 Å2 of solvent accessible surface area. We have showed that P1 can dissociate P2 homodimer spontaneously to form a more stable P1/P2 1 : 1 heterodimer. By homology modelling, we identified three exposed polar residues on helix-3 of P2 are substituted by conserved hydrophobic residues in P1. Confirmed by mutagenesis, we showed that these residues on helix-3 of P1 are not involved in the dimerization of P1/P2, but instead play a vital role in anchoring P1/P2 heterodimer to P0. Based on our results, models of the eukaryotic stalk complex were proposed.
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Affiliation(s)
- Ka-Ming Lee
- Department of Biochemistry, Centre for Protein Science and Crystallography, The Chinese University of Hong Kong, Hong Kong, China
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37
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Elongation in translation as a dynamic interaction among the ribosome, tRNA, and elongation factors EF-G and EF-Tu. Q Rev Biophys 2010; 42:159-200. [PMID: 20025795 DOI: 10.1017/s0033583509990060] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The ribosome is a complex macromolecular machine that translates the message encoded in the messenger RNA and synthesizes polypeptides by linking the individual amino acids carried by the cognate transfer RNAs (tRNAs). The protein elongation cycle, during which the tRNAs traverse the ribosome in a coordinated manner along a path of more than 100 A, is facilitated by large-scale rearrangements of the ribosome. These rearrangements go hand in hand with conformational changes of tRNA as well as elongation factors EF-Tu and EF-G - GTPases that catalyze tRNA delivery and translocation, respectively. This review focuses on the structural data related to the dynamics of the ribosomal machinery, which are the basis, in conjunction with existing biochemical, kinetic, and fluorescence resonance energy transfer data, of our knowledge of the decoding and translocation steps of protein elongation.
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38
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Abstract
Following transcription, genomic information begins a long journey toward translation of its nucleotide sequence into the amino acids of a protein. In eukaryotes, synthesized pre-mRNAs become processed to mature mRNAs by 5'-end capping, splicing, 3'-end cleavage and polyadenylation in the nucleus, before being scrutinized for premature stop codons. Each step requires high precision and control to ensure that an intact and readable message is exported to the cytoplasm before finally becoming translated. Two important aspects of these processes are accurately managed by ribonucleoprotein machineries-the spliceosome and the ribosome. Recently, several natural products targeting these macromolecular assemblies have been reported. For the first time in eukaryotes, these molecules allow chemical disruption and dissection of the sophisticated machinery that regulates post-transcriptional events. Beyond their great potential as bioprobes for investigating mRNA regulation and protein synthesis, these compounds also show promise in opening new therapeutic approaches.
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39
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Grela P, Krokowski D, Gordiyenko Y, Krowarsch D, Robinson CV, Otlewski J, Grankowski N, Tchórzewski M. Biophysical Properties of the Eukaryotic Ribosomal Stalk. Biochemistry 2010; 49:924-33. [DOI: 10.1021/bi901811s] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Przemysław Grela
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
| | - Dawid Krokowski
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
| | - Yuliya Gordiyenko
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB21EW, United Kingdom
| | - Daniel Krowarsch
- Laboratory of Protein Engineering, University of Wroclaw, Tamka 2, 50-137 Wroclaw, Poland
| | - Carol V. Robinson
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB21EW, United Kingdom
| | - Jacek Otlewski
- Laboratory of Protein Engineering, University of Wroclaw, Tamka 2, 50-137 Wroclaw, Poland
| | - Nikodem Grankowski
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
| | - Marek Tchórzewski
- Department of Molecular Biology, Maria Curie-Skłodowska University, Akademicka 19, 20-033 Lublin, Poland
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40
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Abstract
Protein synthesis is one of the major targets in the cell for antibiotics. This review endeavors to provide a comprehensive "post-ribosome structure" A-Z of the huge diversity of antibiotics that target the bacterial translation apparatus, with an emphasis on correlating the vast wealth of biochemical data with more recently available ribosome structures, in order to understand function. The binding site, mechanism of action, and modes of resistance for 26 different classes of protein synthesis inhibitors are presented, ranging from ABT-773 to Zyvox. In addition to improving our understanding of the process of translation, insight into the mechanism of action of antibiotics is essential to the development of novel and more effective antimicrobial agents to combat emerging bacterial resistance to many clinically-relevant drugs.
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Affiliation(s)
- Daniel N Wilson
- Gene Center and Department of Chemistry and Biochemistry, University of Munich, LMU, Munich, Germany.
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41
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Lustig Y, Wachtel C, Safro M, Liu L, Michaeli S. 'RNA walk' a novel approach to study RNA-RNA interactions between a small RNA and its target. Nucleic Acids Res 2009; 38:e5. [PMID: 19854950 PMCID: PMC2800229 DOI: 10.1093/nar/gkp872] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In this study we describe a novel method to investigate the RNA–RNA interactions between a small RNA and its target that we termed ‘RNA walk’. The method is based on UV-induced AMT cross-linking in vivo followed by affinity selection of the hybrid molecules and mapping the intermolecular adducts by RT–PCR or real-time PCR. Domains carrying the cross-linked adducts fail to efficiently amplify by PCR compared with non-cross-linked domains. This method was calibrated and used to study the interaction between a special tRNA-like molecule (sRNA-85) that is part of the trypanosome signal recognition particle (SRP) complex and the ribosome. Four contact sites between sRNA-85 and rRNA were identified by ‘RNA walk’ and were further fine-mapped by primer extension. Two of the contact sites are expected; one contact site mimics the interaction of the mammalian Alu domain of SRP with the ribosome and the other contact sites include a canonical tRNA interaction. The two other cross-linked sites could not be predicted. We propose that ‘RNA walk, is a generic method to map target RNA small RNAs interactions in vivo.
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Affiliation(s)
- Yaniv Lustig
- The Mina and Everard Goodman Faculty of Life Sciences, Bar Ilan University, Ramat-Gan, Israel
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42
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Affiliation(s)
- Alexander S Spirin
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
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43
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Hellen CUT. IRES-induced conformational changes in the ribosome and the mechanism of translation initiation by internal ribosomal entry. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2009; 1789:558-70. [PMID: 19539793 DOI: 10.1016/j.bbagrm.2009.06.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 06/04/2009] [Accepted: 06/11/2009] [Indexed: 01/02/2023]
Abstract
Translation of the genomes of several positive-sense RNA viruses follows end-independent initiation on an internal ribosomal entry site (IRES) in the viral mRNA. There are four major IRES groups, and despite major differences in the mechanisms that they use, one unifying characteristic is that each mechanism involves essential non-canonical interactions of the IRES with components of the canonical translational apparatus. Thus the approximately 200nt.-long Type 4 IRESs (epitomized by Cricket paralysis virus) bind directly to the intersubunit space on the ribosomal 40S subunit, followed by joining to a 60S subunit to form active ribosomes by a factor-independent mechanism. The approximately 300nt.-long type 3 IRESs (epitomized by Hepatitis C virus) binds independently to eukaryotic initiation factor (eIF) 3, and to the solvent-accessible surface and E-site of the 40S subunit: addition of eIF2-GTP/initiator tRNA is sufficient to form a 48S complex that can join a 60S subunit in an eIF5/eIF5B-mediated reaction to form an active ribosome. Recent cryo-electron microscopy and biochemical analyses have revealed a second general characteristic of the mechanisms of initiation on Type 3 and Type 4 IRESs. Both classes of IRES induce similar conformational changes in the ribosome that influence entry, positioning and fixation of mRNA in the ribosomal decoding channel. HCV-like IRESs also stabilize binding of initiator tRNA in the peptidyl (P) site of the 40S subunit, whereas Type 4 IRESs induce changes in the ribosome that likely promote subsequent steps in the translation process, including subunit joining and elongation.
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Affiliation(s)
- Christopher U T Hellen
- Department of Cell Biology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Box 44, Brooklyn, NY 11203, USA.
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44
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Jang CJ, Lo MCY, Jan E. Conserved element of the dicistrovirus IGR IRES that mimics an E-site tRNA/ribosome interaction mediates multiple functions. J Mol Biol 2009; 387:42-58. [PMID: 19361441 DOI: 10.1016/j.jmb.2009.01.042] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 01/20/2009] [Accepted: 01/21/2009] [Indexed: 02/05/2023]
Abstract
The internal ribosome entry site within the intergenic region (IGR IRES) of the Dicistroviridae family mimics a tRNA to directly assemble 80 S ribosomes and initiate translation at a non-AUG codon from the ribosomal A-site. A comparison of IGR IRESs within this viral family reveals structural similarity but little sequence similarity. However, a few specific conserved elements exist, which likely have important roles in IRES function. In this study, we have generated a battery of mutations to characterize the role of a conserved loop (L1.1) region of the IGR IRES. Mutating specific nucleotides within the L1.1 region inhibited IGR IRES-mediated translation in rabbit reticulocyte lysates. By assaying different steps in IRES function, we found that the mutant L1.1 IRESs had reduced affinity for 80 S ribosomes but not 40 S subunits, indicating that the L1.1 region mediated either binding to preformed 80 S or 60 S joining. Furthermore, mutations in L1.1 altered the position of the ribosome on the mutant IRES, indicating that the tRNA-like anticodon/codon mimic within the ribosomal P-site is disrupted. Structural studies have revealed that the L1.1 region interacts with the L1 stalk of the 60 S subunit, which is similar to the interactions between the T-loop of the E-site tRNA and ribosomal protein rpL1. Our results demonstrate that the conserved L1.1 region directs multiple steps in IGR IRES-mediated translation including ribosome binding and positioning, which are functions that the E-site tRNA may normally mediate during translation.
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Affiliation(s)
- Christopher J Jang
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada
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Kurkcuoglu O, Doruker P, Sen TZ, Kloczkowski A, Jernigan RL. The ribosome structure controls and directs mRNA entry, translocation and exit dynamics. Phys Biol 2008; 5:046005. [PMID: 19029596 DOI: 10.1088/1478-3975/5/4/046005] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The protein-synthesizing ribosome undergoes large motions to effect the translocation of tRNAs and mRNA; here, the domain motions of this system are explored with a coarse-grained elastic network model using normal mode analysis. Crystal structures are used to construct various model systems of the 70S complex with/without tRNA, elongation factor Tu and the ribosomal proteins. Computed motions reveal the well-known ratchet-like rotational motion of the large subunits, as well as the head rotation of the small subunit and the high flexibility of the L1 and L7/L12 stalks, even in the absence of ribosomal proteins. This result indicates that these experimentally observed motions during translocation are inherently controlled by the ribosomal shape and only partially dependent upon GTP hydrolysis. Normal mode analysis further reveals the mobility of A- and P-tRNAs to increase in the absence of the E-tRNA. In addition, the dynamics of the E-tRNA is affected by the absence of the ribosomal protein L1. The mRNA in the entrance tunnel interacts directly with helicase proteins S3 and S4, which constrain the mRNA in a clamp-like fashion, as well as with protein S5, which likely orients the mRNA to ensure correct translation. The ribosomal proteins S7, S11 and S18 may also be involved in assuring translation fidelity by constraining the mRNA at the exit site of the channel. The mRNA also interacts with the 16S 3' end forming the Shine-Dalgarno complex at the initiation step; the 3' end may act as a 'hook' to reel in the mRNA to facilitate its exit.
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Affiliation(s)
- Ozge Kurkcuoglu
- Department of Chemical Engineering and Polymer Research Center, Bogazici University, 34342 Bebek, Istanbul, Turkey
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Abstract
The 'stalk' is a large ribosomal subunit domain that regulates translation. In the present study the role of the ribosomal stalk P proteins in modulating ribosomal activity has been investigated in human cells using RNA interference. A strong down-regulation of P2 mRNA and a drastic decrease in P2 protein in a stable human cell line was achieved using a doxycycline-inducible system. Interestingly, the amount of P1 protein was similarly decreased in these cells, in contrast with the expression of P1 mRNA. The loss of P1/P2 proteins produced a decrease in the growth rate of these cells, as well as an altered polysome pattern with reduced translation efficiency, but without affecting the free 40 S/60 S subunit ratio. A decrease in the ribosomal-subunit joining capacity was also observed. These data indicate that P1/P2 proteins modulate cytoplasmic translation by influencing the interaction between subunits, thereby regulating the rate of cell proliferation.
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Kim E, Graham LE. EEF2 analysis challenges the monophyly of Archaeplastida and Chromalveolata. PLoS One 2008; 3:e2621. [PMID: 18612431 PMCID: PMC2440802 DOI: 10.1371/journal.pone.0002621] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2008] [Accepted: 06/02/2008] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Classification of eukaryotes provides a fundamental phylogenetic framework for ecological, medical, and industrial research. In recent years eukaryotes have been classified into six major supergroups: Amoebozoa, Archaeplastida, Chromalveolata, Excavata, Opisthokonta, and Rhizaria. According to this supergroup classification, Archaeplastida and Chromalveolata each arose from a single plastid-generating endosymbiotic event involving a cyanobacterium (Archaeplastida) or red alga (Chromalveolata). Although the plastids within members of the Archaeplastida and Chromalveolata share some features, no nucleocytoplasmic synapomorphies supporting these supergroups are currently known. METHODOLOGY/PRINCIPAL FINDINGS This study was designed to test the validity of the Archaeplastida and Chromalveolata through the analysis of nucleus-encoded eukaryotic translation elongation factor 2 (EEF2) and cytosolic heat-shock protein of 70 kDa (HSP70) sequences generated from the glaucophyte Cyanophora paradoxa, the cryptophytes Goniomonas truncata and Guillardia theta, the katablepharid Leucocryptos marina, the rhizarian Thaumatomonas sp. and the green alga Mesostigma viride. The HSP70 phylogeny was largely unresolved except for certain well-established groups. In contrast, EEF2 phylogeny recovered many well-established eukaryotic groups and, most interestingly, revealed a well-supported clade composed of cryptophytes, katablepharids, haptophytes, rhodophytes, and Viridiplantae (green algae and land plants). This clade is further supported by the presence of a two amino acid signature within EEF2, which appears to have arisen from amino acid replacement before the common origin of these eukaryotic groups. CONCLUSIONS/SIGNIFICANCE Our EEF2 analysis strongly refutes the monophyly of the Archaeplastida and the Chromalveolata, adding to a growing body of evidence that limits the utility of these supergroups. In view of EEF2 phylogeny and other morphological evidence, we discuss the possibility of an alternative eukaryotic supergroup.
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Affiliation(s)
- Eunsoo Kim
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
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Pfingsten JS, Kieft JS. RNA structure-based ribosome recruitment: lessons from the Dicistroviridae intergenic region IRESes. RNA (NEW YORK, N.Y.) 2008; 14:1255-1263. [PMID: 18515544 PMCID: PMC2441983 DOI: 10.1261/rna.987808] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In eukaryotes, the canonical process of initiating protein synthesis on an mRNA depends on many large protein factors and the modified nucleotide cap on the 5' end of the mRNA. However, certain RNA sequences can bypass the need for these proteins and cap, using an RNA structure-based mechanism called internal initiation of translation. These RNAs are called internal ribosome entry sites (IRESes), and the cap-independent initiation pathway they support is critical for successful infection by many viruses of medical and economic importance. In this review, we briefly describe and compare mechanistic and structural groups of viral IRES RNAs, focusing on those IRESes that are capable of direct ribosome recruitment using specific RNA structures. We then discuss in greater detail some recent advances in our understanding of the intergenic region IRESes of the Dicistroviridae, which use the most streamlined ribosome-recruitment mechanism yet discovered. By combining these findings with knowledge of canonical translation and the behavior of other IRESes, mechanistic models of this RNA structure-based process are emerging.
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Affiliation(s)
- Jennifer S Pfingsten
- Howard Hughes Medical Institute, Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, USA.
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Chandramouli P, Topf M, Ménétret JF, Eswar N, Gutell RR, Sali A, Akey CW. Structure of the mammalian 80S ribosome at 8.7 A resolution. Structure 2008; 16:535-48. [PMID: 18400176 PMCID: PMC2775484 DOI: 10.1016/j.str.2008.01.007] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 01/03/2008] [Accepted: 01/26/2008] [Indexed: 01/12/2023]
Abstract
In this paper, we present a structure of the mammalian ribosome determined at approximately 8.7 A resolution by electron cryomicroscopy and single-particle methods. A model of the ribosome was created by docking homology models of subunit rRNAs and conserved proteins into the density map. We then modeled expansion segments in the subunit rRNAs and found unclaimed density for approximately 20 proteins. In general, many conserved proteins and novel proteins interact with expansion segments to form an integrated framework that may stabilize the mature ribosome. Our structure provides a snapshot of the mammalian ribosome at the beginning of translation and lends support to current models in which large movements of the small subunit and L1 stalk occur during tRNA translocation. Finally, details are presented for intersubunit bridges that are specific to the eukaryotic ribosome. We suggest that these bridges may help reset the conformation of the ribosome to prepare for the next cycle of chain elongation.
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Affiliation(s)
- Preethi Chandramouli
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany St., Boston, Massachusetts 02118, USA
| | - Maya Topf
- School of Crystallography, Birkbeck, University of London, Malet Street, London WC1E 7HX
| | - Jean-François Ménétret
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany St., Boston, Massachusetts 02118, USA
| | - Narayanan Eswar
- Department of Biopharmaceutical Sciences, California Institute for Quantitative Biomedical Research, QB3 at Mission Bay, University of California at San Francisco, 1700 4th Street, San Francisco, CA 94158, USA
| | - Robin R. Gutell
- The Institute for Cellular and Molecular Biology, The University of Texas at Austin, TX 78712, USA
| | - Andrej Sali
- Department of Biopharmaceutical Sciences, California Institute for Quantitative Biomedical Research, QB3 at Mission Bay, University of California at San Francisco, 1700 4th Street, San Francisco, CA 94158, USA
| | - Christopher W. Akey
- Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany St., Boston, Massachusetts 02118, USA
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A chemical genomic screen in Saccharomyces cerevisiae reveals a role for diphthamidation of translation elongation factor 2 in inhibition of protein synthesis by sordarin. Antimicrob Agents Chemother 2008; 52:1623-9. [PMID: 18285480 DOI: 10.1128/aac.01603-07] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Sordarin and its derivatives are antifungal compounds of potential clinical interest. Despite the highly conserved nature of the fungal and mammalian protein synthesis machineries, sordarin is a selective inhibitor of protein synthesis in fungal organisms. In cells sensitive to sordarin, its mode of action is through preventing the release of translation elongation factor 2 (eEF2) during the translocation step, thus blocking protein synthesis. To further investigate the cellular components required for the effects of sordarin in fungal cells, we have used the haploid deletion collection of Saccharomyces cerevisiae to systematically identify genes whose deletion confers sensitivity or resistance to the compound. Our results indicate that genes in a number of cellular pathways previously unknown to play a role in sordarin response are involved in its growth effects on fungal cells and reveal a specific requirement for the diphthamidation pathway of cells in causing eEF2 to be sensitive to the effects of sordarin on protein synthesis. Our results underscore the importance of the powerful genomic tools developed in yeast (Saccharomyces cerevisiae) to more comprehensively understanding the cellular mechanisms involved in the response to therapeutic agents.
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