1
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Bulygin KN, Timofeev IO, Malygin AA, Graifer DM, Meschaninova MI, Venyaminova AG, Krumkacheva OA, Fedin MV, Yu Frolova L, Karpova GG, Bagryanskaya EG. Two alternative conformations of mRNA in the human ribosome during elongation and termination of translation as revealed by EPR spectroscopy. Comput Struct Biotechnol J 2021; 19:4702-4710. [PMID: 34504663 PMCID: PMC8390954 DOI: 10.1016/j.csbj.2021.08.024] [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: 03/14/2021] [Revised: 08/12/2021] [Accepted: 08/16/2021] [Indexed: 11/29/2022] Open
Abstract
DEER reveals the conformational variability of mRNA at the certain translation steps. Elongation and termination complexes exist in 2 conformations in dynamic equilibrium. The conformations of mRNA in 40S channel undergo no major change during termination.
The conformation of mRNA in the region of the human 80S ribosome decoding site was monitored using 11-mer mRNA analogues that bore nitroxide spin labels attached to the terminal nucleotide bases. Intramolecular spin–spin distances were measured by DEER/PELDOR spectroscopy in model complexes mimicking different states of the 80S ribosome during elongation and termination of translation. The measurements revealed that in all studied complexes, mRNA exists in two alternative conformations, whose ratios are different in post-translocation, pre-translocation and termination complexes. We found that the presence of a tRNA molecule at the ribosomal A site decreases the relative share of the more extended mRNA conformation, whereas the binding of eRF1 (alone or in a complex with eRF3) results in the opposite effect. In the termination complexes, the ratios of mRNA conformations are practically the same, indicating that a part of mRNA bound in the ribosome channel does not undergo significant structural alterations in the course of completion of the translation. Our results contribute to the understanding of mRNA molecular dynamics in the mammalian ribosome channel during translation.
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Affiliation(s)
- Konstantin N Bulygin
- Institute of Chemical Biology and Fundamental Medicine SB RAS, pr. Lavrentjeva 8, Novosibirsk 630090, Russia
| | - Ivan O Timofeev
- International Tomography Center SB RAS, Institutskaya Str. 3a, Novosibirsk 630090, Russia
| | - Alexey A Malygin
- Institute of Chemical Biology and Fundamental Medicine SB RAS, pr. Lavrentjeva 8, Novosibirsk 630090, Russia
| | - Dmitri M Graifer
- Institute of Chemical Biology and Fundamental Medicine SB RAS, pr. Lavrentjeva 8, Novosibirsk 630090, Russia
| | - Maria I Meschaninova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, pr. Lavrentjeva 8, Novosibirsk 630090, Russia
| | - Alya G Venyaminova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, pr. Lavrentjeva 8, Novosibirsk 630090, Russia
| | - Olesya A Krumkacheva
- International Tomography Center SB RAS, Institutskaya Str. 3a, Novosibirsk 630090, Russia
| | - Matvey V Fedin
- International Tomography Center SB RAS, Institutskaya Str. 3a, Novosibirsk 630090, Russia
| | - Ludmila Yu Frolova
- Engelhardt Institute of Molecular Biology RAS, Vavilova Str. 32, Moscow 119991, Russia
| | - Galina G Karpova
- Institute of Chemical Biology and Fundamental Medicine SB RAS, pr. Lavrentjeva 8, Novosibirsk 630090, Russia
| | - Elena G Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, pr. Lavrentjeva 9, Novosibirsk 630090, Russia
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2
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Shetty S, Varshney U. Regulation of translation by one-carbon metabolism in bacteria and eukaryotic organelles. J Biol Chem 2021; 296:100088. [PMID: 33199376 PMCID: PMC7949028 DOI: 10.1074/jbc.rev120.011985] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 11/15/2020] [Accepted: 11/16/2020] [Indexed: 12/20/2022] Open
Abstract
Protein synthesis is an energetically costly cellular activity. It is therefore important that the process of mRNA translation remains in excellent synchrony with cellular metabolism and its energy reserves. Unregulated translation could lead to the production of incomplete, mistranslated, or misfolded proteins, squandering the energy needed for cellular sustenance and causing cytotoxicity. One-carbon metabolism (OCM), an integral part of cellular intermediary metabolism, produces a number of one-carbon unit intermediates (formyl, methylene, methenyl, methyl). These OCM intermediates are required for the production of amino acids such as methionine and other biomolecules such as purines, thymidylate, and redox regulators. In this review, we discuss how OCM impacts the translation apparatus (composed of ribosome, tRNA, mRNA, and translation factors) and regulates crucial steps in protein synthesis. More specifically, we address how the OCM metabolites regulate the fidelity and rate of translation initiation in bacteria and eukaryotic organelles such as mitochondria. Modulation of the fidelity of translation initiation by OCM opens new avenues to understand alternative translation mechanisms involved in stress tolerance and drug resistance.
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Affiliation(s)
- Sunil Shetty
- Biozentrum, University of Basel, Basel, Switzerland
| | - Umesh Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India; Jawaharlal Nehru Centre for Advanced Scientific Studies, Jakkur, Bangalore, India.
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3
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Powers KT, Szeto JYA, Schaffitzel C. New insights into no-go, non-stop and nonsense-mediated mRNA decay complexes. Curr Opin Struct Biol 2020; 65:110-118. [PMID: 32688260 DOI: 10.1016/j.sbi.2020.06.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 06/10/2020] [Accepted: 06/18/2020] [Indexed: 11/26/2022]
Abstract
Eukaryotes possess a variety of translational control mechanisms which function in the surveillance of mRNAs, discriminating between normal and aberrant translation elongation and termination, triggering mRNA decay. The three major evolutionarily conserved eukaryotic pathways are No-Go, Non-Stop and Nonsense-Mediated mRNA Decay. Recent findings suggest that stalling of the ribosome, due to mRNA secondary structure or translation into poly(A)-stretches, leads to ribosome collisions which are detected by No-Go/Non-Stop mRNA decay factors. Subsequent ribosome ubiquitination at the interface of two collided ribosomes is considered the signal for mRNA decay. Similarly, translation termination at a premature stop codon is slower than normal, leading to recruitment and activation of nonsense-mediated mRNA decay factors, including SMG1-8-9. Here, we detail new insights into the molecular mechanisms of these pathways.
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Affiliation(s)
- Kyle T Powers
- University of Bristol, School of Biochemistry, University Walk, Bristol, BS8 1TD, United Kingdom
| | - Jenn-Yeu Alvin Szeto
- University of Bristol, School of Biochemistry, University Walk, Bristol, BS8 1TD, United Kingdom
| | - Christiane Schaffitzel
- University of Bristol, School of Biochemistry, University Walk, Bristol, BS8 1TD, United Kingdom.
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4
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Release factor-dependent ribosome rescue by BrfA in the Gram-positive bacterium Bacillus subtilis. Nat Commun 2019; 10:5397. [PMID: 31776341 PMCID: PMC6881298 DOI: 10.1038/s41467-019-13408-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 11/07/2019] [Indexed: 12/14/2022] Open
Abstract
Rescue of the ribosomes from dead-end translation complexes, such as those on truncated (non-stop) mRNA, is essential for the cell. Whereas bacteria use trans-translation for ribosome rescue, some Gram-negative species possess alternative and release factor (RF)-dependent rescue factors, which enable an RF to catalyze stop-codon-independent polypeptide release. We now discover that the Gram-positive Bacillus subtilis has an evolutionarily distinct ribosome rescue factor named BrfA. Genetic analysis shows that B. subtilis requires the function of either trans-translation or BrfA for growth, even in the absence of proteotoxic stresses. Biochemical and cryo-electron microscopy (cryo-EM) characterization demonstrates that BrfA binds to non-stop stalled ribosomes, recruits homologous RF2, but not RF1, and induces its transition into an open active conformation. Although BrfA is distinct from E. coli ArfA, they use convergent strategies in terms of mode of action and expression regulation, indicating that many bacteria may have evolved as yet unidentified ribosome rescue systems. In bacteria, the conserved trans-translation system serves as the primary pathway of ribosome rescue, but many species can also use alternative rescue pathways. Here the authors report that in B. subtilis, the rescue factor BrfA binds to non-stop stalled ribosomes, recruits RF2 but not RF1, and induces transition of the ribosome into an open active conformation.
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Fujii K, Susanto TT, Saurabh S, Barna M. Decoding the Function of Expansion Segments in Ribosomes. Mol Cell 2019; 72:1013-1020.e6. [PMID: 30576652 DOI: 10.1016/j.molcel.2018.11.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 10/30/2018] [Accepted: 11/15/2018] [Indexed: 10/27/2022]
Abstract
Expansion segments (ESs) are enigmatic insertions within the eukaryotic ribosome, the longest of which resemble tentacle-like extensions that vary in length and sequence across evolution, with a largely unknown function. By selectively engineering rRNA in yeast, we find that one of the largest ESs, ES27L, has an unexpected function in translation fidelity. Ribosomes harboring a deletion in the distal portion of ES27L have increased amino acid misincorporation, as well as readthrough and frameshifting errors. By employing quantitative mass spectrometry, we further find that ES27L acts as an RNA scaffold to facilitate binding of a conserved enzyme, methionine amino peptidase (MetAP). We show that MetAP unexpectedly controls the accuracy of ribosome decoding, which is coupled to an increase in its enzymatic function through its interaction with ES27L. These findings reveal that variable ESs of the ribosome serve important functional roles and act as platforms for the binding of proteins that modulate translation across evolution.
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Affiliation(s)
- Kotaro Fujii
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Teodorus Theo Susanto
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - Saumya Saurabh
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | - Maria Barna
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA; Department of Genetics, Stanford University, Stanford, CA 94305, USA.
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6
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Prabhakar A, Puglisi EV, Puglisi JD. Single-Molecule Fluorescence Applied to Translation. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a032714. [PMID: 29891562 DOI: 10.1101/cshperspect.a032714] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Single-molecule fluorescence methods have illuminated the dynamics of the translational machinery. Structural and bulk biochemical experiments have provided detailed atomic and global mechanistic views of translation, respectively. Single-molecule studies of translation have bridged these views by temporally connecting the conformational and compositional states defined from structural data within the mechanistic framework of translation produced from biochemical studies. Here, we discuss the context for applying different single-molecule fluorescence experiments, and present recent applications to studying prokaryotic and eukaryotic translation. We underscore the power of observing single translating ribosomes to delineate and sort complex mechanistic pathways during initiation and elongation, and discuss future applications of current and improved technologies.
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Affiliation(s)
- Arjun Prabhakar
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305.,Program in Biophysics, Stanford University, Stanford, California 94305
| | - Elisabetta Viani Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305
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7
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Shi X, Joseph S. Mechanism of Translation Termination: RF1 Dissociation Follows Dissociation of RF3 from the Ribosome. Biochemistry 2016; 55:6344-6354. [PMID: 27779391 DOI: 10.1021/acs.biochem.6b00921] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Release factors 1 and 2 (RF1 and RF2, respectively) bind to ribosomes that have a stop codon in the A site and catalyze the release of the newly synthesized protein. Following peptide release, the dissociation of RF1 and RF2 from the ribosome is accelerated by release factor 3 (RF3). The mechanism for RF3-promoted dissociation of RF1 and RF2 is unclear. It was previously proposed that RF3 hydrolyzes GTP and dissociates from the ribosome after RF1 dissociation. Here we monitored directly the dissociation kinetics of RF1 and RF3 using Förster resonance energy transfer-based assays. In contrast to the previous model, our data show that RF3 hydrolyzes GTP and dissociates from the ribosome before RF1 dissociation. We propose that RF3 stabilizes the ratcheted state of the ribosome, which consequently accelerates the dissociation of RF1 and RF2.
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Affiliation(s)
- Xinying Shi
- Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, La Jolla, California 92093-0314, United States
| | - Simpson Joseph
- Department of Chemistry and Biochemistry, University of California, San Diego , 9500 Gilman Drive, La Jolla, California 92093-0314, United States
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8
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Probing the Translation Dynamics of Ribosomes Using Zero-Mode Waveguides. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 139:1-43. [PMID: 26970189 DOI: 10.1016/bs.pmbts.2015.10.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In order to coordinate the complex biochemical and structural feat of converting triple-nucleotide codons into their corresponding amino acids, the ribosome must physically manipulate numerous macromolecules including the mRNA, tRNAs, and numerous translation factors. The ribosome choreographs binding, dissociation, physical movements, and structural rearrangements so that they synergistically harness the energy from biochemical processes, including numerous GTP hydrolysis steps and peptide bond formation. Due to the dynamic and complex nature of translation, the large cast of ligands involved, and the large number of possible configurations, tracking the global time evolution or dynamics of the ribosome complex in translation has proven to be challenging for bulk methods. Conventional single-molecule fluorescence experiments on the other hand require low concentrations of fluorescent ligands to reduce background noise. The significantly reduced bimolecular association rates under those conditions limit the number of steps that can be observed within the time window available to a fluorophore. The advent of zero-mode waveguide (ZMW) technology has allowed the study of translation at near-physiological concentrations of labeled ligands, moving single-molecule fluorescence microscopy beyond focused model systems into studying the global dynamics of translation in realistic setups. This chapter reviews the recent works using the ZMW technology to dissect the mechanism of translation initiation and elongation in prokaryotes, including complex processes such as translational stalling and frameshifting. Given the success of the technology, similarly complex biological processes could be studied in near-physiological conditions with the controllability of conventional in vitro experiments.
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9
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Rudorf S, Lipowsky R. Protein Synthesis in E. coli: Dependence of Codon-Specific Elongation on tRNA Concentration and Codon Usage. PLoS One 2015; 10:e0134994. [PMID: 26270805 PMCID: PMC4535986 DOI: 10.1371/journal.pone.0134994] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 07/15/2015] [Indexed: 11/18/2022] Open
Abstract
To synthesize a protein, a ribosome moves along a messenger RNA (mRNA), reads it codon by codon, and takes up the corresponding ternary complexes which consist of aminoacylated transfer RNAs (aa-tRNAs), elongation factor Tu (EF-Tu), and GTP. During this process of translation elongation, the ribosome proceeds with a codon-specific rate. Here, we present a general theoretical framework to calculate codon-specific elongation rates and error frequencies based on tRNA concentrations and codon usages. Our theory takes three important aspects of in-vivo translation elongation into account. First, non-cognate, near-cognate and cognate ternary complexes compete for the binding sites on the ribosomes. Second, the corresponding binding rates are determined by the concentrations of free ternary complexes, which must be distinguished from the total tRNA concentrations as measured in vivo. Third, for each tRNA species, the difference between total tRNA and ternary complex concentration depends on the codon usages of the corresponding cognate and near-cognate codons. Furthermore, we apply our theory to two alternative pathways for tRNA release from the ribosomal E site and show how the mechanism of tRNA release influences the concentrations of free ternary complexes and thus the codon-specific elongation rates. Using a recently introduced method to determine kinetic rates of in-vivo translation from in-vitro data, we compute elongation rates for all codons in Escherichia coli. We show that for some tRNA species only a few tRNA molecules are part of ternary complexes and, thus, available for the translating ribosomes. In addition, we find that codon-specific elongation rates strongly depend on the overall codon usage in the cell, which could be altered experimentally by overexpression of individual genes.
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Affiliation(s)
- Sophia Rudorf
- Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
- * E-mail: (SR); (RL)
| | - Reinhard Lipowsky
- Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Potsdam, Germany
- * E-mail: (SR); (RL)
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10
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Wong TY, Schwartzbach SD. Protein Mis-Termination Initiates Genetic Diseases, Cancers, and Restricts Bacterial Genome Expansion. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART C, ENVIRONMENTAL CARCINOGENESIS & ECOTOXICOLOGY REVIEWS 2015; 33:255-285. [PMID: 26087060 DOI: 10.1080/10590501.2015.1053461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Protein termination is an important cellular process. Protein termination relies on the stop-codons in the mRNA interacting properly with the releasing factors on the ribosome. One third of inherited diseases, including cancers, are associated with the mutation of the stop-codons. Many pathogens and viruses are able to manipulate their stop-codons to express their virulence. The influence of stop-codons is not limited to the primary reading frame of the genes. Stop-codons in the second and third reading frames are referred as premature stop signals (PSC). Stop-codons and PSCs together are collectively referred as stop-signals. The ratios of the stop-signals (referred as translation stop-signals ratio or TSSR) of genetically related bacteria, despite their great differences in gene contents, are much alike. This nearly identical Genomic-TSSR value of genetically related bacteria may suggest that bacterial genome expansion is limited by their unique stop-signals bias. We review the protein termination process and the different types of stop-codon mutation in plants, animals, microbes, and viruses, with special emphasis on the role of PSCs in directing bacterial evolution in their natural environments. Knowing the limit of genomic boundary could facilitate the formulation of new strategies in controlling the spread of diseases and combat antibiotic-resistant bacteria.
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Affiliation(s)
- Tit-Yee Wong
- a Department of Biological Sciences , University of Memphis , Memphis , Tennessee , USA
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11
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Structural basis for translational surveillance by the large ribosomal subunit-associated protein quality control complex. Proc Natl Acad Sci U S A 2014; 111:15981-6. [PMID: 25349383 DOI: 10.1073/pnas.1413882111] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
All organisms have evolved mechanisms to manage the stalling of ribosomes upon translation of aberrant mRNA. In eukaryotes, the large ribosomal subunit-associated quality control complex (RQC), composed of the listerin/Ltn1 E3 ubiquitin ligase and cofactors, mediates the ubiquitylation and extraction of ribosome-stalled nascent polypeptide chains for proteasomal degradation. How RQC recognizes stalled ribosomes and performs its functions has not been understood. Using single-particle cryoelectron microscopy, we have determined the structure of the RQC complex bound to stalled 60S ribosomal subunits. The structure establishes how Ltn1 associates with the large ribosomal subunit and properly positions its E3-catalytic RING domain to mediate nascent chain ubiquitylation. The structure also reveals that a distinguishing feature of stalled 60S particles is an exposed, nascent chain-conjugated tRNA, and that the Tae2 subunit of RQC, which facilitates Ltn1 binding, is responsible for selective recognition of stalled 60S subunits. RQC components are engaged in interactions across a large span of the 60S subunit surface, connecting the tRNA in the peptidyl transferase center to the distally located nascent chain tunnel exit. This work provides insights into a mechanism linking translation and protein degradation that targets defective proteins immediately after synthesis, while ignoring nascent chains in normally translating ribosomes.
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12
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Meyer KD, Jaffrey SR. The dynamic epitranscriptome: N6-methyladenosine and gene expression control. Nat Rev Mol Cell Biol 2014; 15:313-26. [PMID: 24713629 DOI: 10.1038/nrm3785] [Citation(s) in RCA: 707] [Impact Index Per Article: 70.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
N(6)-methyladenosine (m(6)A) is a modified base that has long been known to be present in non-coding RNAs, ribosomal RNA, polyadenylated RNA and at least one mammalian mRNA. However, our understanding of the prevalence of this modification has been fundamentally redefined by transcriptome-wide m(6)A mapping studies, which have shown that m(6)A is present in a large subset of the transcriptome in specific regions of mRNA. This suggests that mRNA may undergo post-transcriptional methylation to regulate its fate and function, which is analogous to methyl modifications in DNA. Thus, the pattern of methylation constitutes an mRNA 'epitranscriptome'. The identification of adenosine methyltransferases ('writers'), m(6)A demethylating enzymes ('erasers') and m(6)A-binding proteins ('readers') is helping to define cellular pathways for the post-transcriptional regulation of mRNAs.
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Affiliation(s)
- Kate D Meyer
- Department of Pharmacology, Weill Cornell Medical College, Cornell University, New York City, New York 10065, USA
| | - Samie R Jaffrey
- Department of Pharmacology, Weill Cornell Medical College, Cornell University, New York City, New York 10065, USA
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13
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Kobayashi K, Ishitani R, Nureki O. Recent structural studies on Dom34/aPelota and Hbs1/aEF1α: important factors for solving general problems of ribosomal stall in translation. Biophysics (Nagoya-shi) 2013; 9:131-40. [PMID: 27493551 PMCID: PMC4629679 DOI: 10.2142/biophysics.9.131] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Accepted: 08/12/2013] [Indexed: 12/01/2022] Open
Abstract
In the translation process, translating ribosomes usually move on an mRNA until they reach the stop codon. However, when ribosomes translate an aberrant mRNA, they stall. Then, ribosomes are rescued from the aberrant mRNA, and the aberrant mRNA is subsequently degraded. In eukaryotes, Pelota (Dom34 in yeast) and Hbs1 are responsible for solving general problems of ribosomal stall in translation. In archaea, aPelota and aEF1α, homologous to Pelota and Hbs1, respectively, are considered to be involved in that process. In recent years, great progress has been made in determining structures of Dom34/aPelota and Hbs1/aEF1α. In this review, we focus on the functional roles of Dom34/aPelota and Hbs1/aEF1α in ribosome rescue, based on recent structural studies of them. We will also present questions to be answered by future work.
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Affiliation(s)
- Kan Kobayashi
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Ryuichiro Ishitani
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
| | - Osamu Nureki
- Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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14
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Santos N, Zhu J, Donohue JP, Korostelev AA, Noller HF. Crystal structure of the 70S ribosome bound with the Q253P mutant form of release factor RF2. Structure 2013; 21:1258-63. [PMID: 23769667 DOI: 10.1016/j.str.2013.04.028] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/26/2013] [Accepted: 04/26/2013] [Indexed: 11/25/2022]
Abstract
Bacterial translation termination is mediated by release factors RF1 and RF2, which recognize stop codons and catalyze hydrolysis of the peptidyl-tRNA ester bond. The catalytic mechanism has been debated. We proposed that the backbone amide NH group, rather than the side chain, of the glutamine of the universally conserved GGQ motif participates in catalysis by H-bonding to the tetrahedral transition-state intermediate and by product stabilization. This was supported by complete loss of RF1 catalytic activity when glutamine is replaced by proline, the only residue that lacks a backbone NH group. Here, we present the 3.4 Å crystal structure of the ribosome complex containing the RF2 Q253P mutant and find that its fold, including the GGP sequence, is virtually identical to that of wild-type RF2. This rules out proline-induced misfolding and further supports the proposal that catalytic activity requires interaction of the Gln-253 backbone amide with the 3' end of peptidyl-tRNA.
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Affiliation(s)
- Natalia Santos
- Center for Molecular Biology of RNA and Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
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15
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Kryuchkova P, Grishin A, Eliseev B, Karyagina A, Frolova L, Alkalaeva E. Two-step model of stop codon recognition by eukaryotic release factor eRF1. Nucleic Acids Res 2013; 41:4573-86. [PMID: 23435318 PMCID: PMC3632111 DOI: 10.1093/nar/gkt113] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Release factor eRF1 plays a key role in the termination of protein synthesis in eukaryotes. The eRF1 consists of three domains (N, M and C) that perform unique roles in termination. Previous studies of eRF1 point mutants and standard/variant code eRF1 chimeras unequivocally demonstrated a direct involvement of the highly conserved N-domain motifs (NIKS, YxCxxxF and GTx) in stop codon recognition. In the current study, we extend this work by investigating the role of the 41 invariant and conserved N-domain residues in stop codon decoding by human eRF1. Using a combination of the conservative and non-conservative amino acid substitutions, we measured the functional activity of >80 mutant eRF1s in an in vitro reconstituted eukaryotic translation system and selected 15 amino acid residues essential for recognition of different stop codon nucleotides. Furthermore, toe-print analyses provide evidence of a conformational rearrangement of ribosomal complexes that occurs during binding of eRF1 to messenger RNA and reflects stop codon decoding activity of eRF1. Based on our experimental data and molecular modelling of the N-domain at the ribosomal A site, we propose a two-step model of stop codon decoding in the eukaryotic ribosome.
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Affiliation(s)
- Polina Kryuchkova
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
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16
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An Introduction to the Structure and Function of the Ribosome. EcoSal Plus 2013; 5. [PMID: 26442932 DOI: 10.1128/ecosal.2.5.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
E. coli continues to serve as a key model for the structure and function of the ribosome, structures of ribosome from other organisms and domains of life have also greatly contributed to our knowledge of protein synthesis. Many structural models of the ribosome in a number of steps of the protein synthesis cycle have been solved by cryo-electron microscopy (cryo-EM) and x-ray crystallography. This chapter introduces the structure and dynamics of the ribosome based on these structures and ends with a brief discussion of the many questions that the structures leave unanswered. Protein synthesis is a multistep process, and the structural features of the ribosome along with the large number of cofactors reflect the complexity of translation. Numerous protein factors in addition to the ribosome contribute to translation in bacteria during the steps of initiation, elongation, termination, and recycling. These protein factors make intimate contacts to key regions of the ribosome, and this aspect is discussed in the chapter in light of our present understanding of the structure and function of the ribosome. The intact ribosome contains three binding sites for substrate tRNAs that are termed as the aminoacyl-tRNA site (A site), peptidyl-tRNA site (P site), and exit-tRNA site (E site). These three binding sites span the interface between the 30S and 50S subunits. The central activity of the ribosome is catalysis of peptide bond formation. The region of the ribosome responsible for catalyzing the reaction is called the peptidyl transferase center (PTC).
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Single-particle EM reveals extensive conformational variability of the Ltn1 E3 ligase. Proc Natl Acad Sci U S A 2013; 110:1702-7. [PMID: 23319619 DOI: 10.1073/pnas.1210041110] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Ltn1 is a 180-kDa E3 ubiquitin ligase that associates with ribosomes and marks certain aberrant, translationally arrested nascent polypeptide chains for proteasomal degradation. In addition to its evolutionarily conserved large size, Ltn1 is characterized by the presence of a conserved N terminus, HEAT/ARM repeats predicted to comprise the majority of the protein, and a C-terminal catalytic RING domain, although the protein's exact structure is unknown. We used numerous single-particle EM strategies to characterize Ltn1's structure based on negative stain and vitreous ice data. Two-dimensional classifications and subsequent 3D reconstructions of electron density maps show that Ltn1 has an elongated form and presents a continuum of conformational states about two flexible hinge regions, whereas its overall architecture is reminiscent of multisubunit cullin-RING ubiquitin ligase complexes. We propose a model of Ltn1 function based on its conformational variability and flexibility that describes how these features may play a role in cotranslational protein quality control.
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Zhou J, Korostelev A, Lancaster L, Noller HF. Crystal structures of 70S ribosomes bound to release factors RF1, RF2 and RF3. Curr Opin Struct Biol 2012; 22:733-42. [PMID: 22999888 DOI: 10.1016/j.sbi.2012.08.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 08/22/2012] [Accepted: 08/22/2012] [Indexed: 11/29/2022]
Abstract
Termination is a crucial step in translation, most notably because premature termination can lead to toxic truncated polypeptides. Most interesting is the fact that stop codons are read by a completely different mechanism from that of sense codons. In recent years, rapid progress has been made in the structural biology of complexes of bacterial ribosomes bound to translation termination factors, much of which has been discussed in earlier reviews [1-5]. Here, we present a brief overview of the structures of bacterial translation termination complexes. The first part summarizes what has been learned from crystal structures of complexes containing the class I release factors RF1 and RF2. In the second part, we discuss the results and implications of two recent X-ray structures of complexes of ribosomes bound to the translational GTPase RF3. These structures have provided many insights and a number of surprises. While structures alone do not tell us how these complicated molecular assemblies work, is it nevertheless clear that it will not be possible to understand their mechanisms without detailed structural information.
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Affiliation(s)
- Jie Zhou
- Center for Molecular Biology of RNA and Department of Molecular, Cell and Developmental Biology, University of California at Santa Cruz, Santa Cruz, CA 95064, USA
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19
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Wang L, Pulk A, Wasserman MR, Feldman MB, Altman RB, Cate JHD, Blanchard SC. Allosteric control of the ribosome by small-molecule antibiotics. Nat Struct Mol Biol 2012; 19:957-63. [PMID: 22902368 PMCID: PMC3645490 DOI: 10.1038/nsmb.2360] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 07/13/2012] [Indexed: 12/15/2022]
Abstract
Protein synthesis is targeted by numerous, chemically distinct antibiotics that bind and inhibit key functional centers of the ribosome. Using single-molecule imaging and X-ray crystallography, we show that the aminoglycoside neomycin blocks aminoacyl-transfer RNA (aa-tRNA) selection and translocation as well as ribosome recycling by binding to helix 69 (H69) of 23S ribosomal RNA within the large subunit of the Escherichia coli ribosome. There, neomycin prevents the remodeling of intersubunit bridges that normally accompanies the process of subunit rotation to stabilize a partially rotated ribosome configuration in which peptidyl (P)-site tRNA is constrained in a previously unidentified hybrid position. Direct measurements show that this neomycin-stabilized intermediate is incompatible with the translation factor binding that is required for distinct protein synthesis reactions. These findings reveal the functional importance of reversible intersubunit rotation to the translation mechanism and shed new light on the allosteric control of ribosome functions by small-molecule antibiotics.
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MESH Headings
- Anti-Bacterial Agents/chemistry
- Anti-Bacterial Agents/pharmacology
- Crystallography, X-Ray
- Escherichia coli/chemistry
- Escherichia coli/drug effects
- Escherichia coli/metabolism
- Escherichia coli Proteins/metabolism
- Models, Molecular
- Neomycin/chemistry
- Neomycin/pharmacology
- Protein Biosynthesis/drug effects
- RNA, Bacterial/chemistry
- RNA, Bacterial/metabolism
- RNA, Ribosomal/chemistry
- RNA, Ribosomal/metabolism
- RNA, Transfer, Amino Acyl/metabolism
- Ribosome Subunits, Large, Bacterial/chemistry
- Ribosome Subunits, Large, Bacterial/drug effects
- Ribosome Subunits, Large, Bacterial/metabolism
- Ribosome Subunits, Small, Bacterial/chemistry
- Ribosome Subunits, Small, Bacterial/drug effects
- Ribosome Subunits, Small, Bacterial/metabolism
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Affiliation(s)
- Leyi Wang
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York, USA
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20
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Duarte I, Nabuurs SB, Magno R, Huynen M. Evolution and diversification of the organellar release factor family. Mol Biol Evol 2012; 29:3497-512. [PMID: 22688947 PMCID: PMC3472500 DOI: 10.1093/molbev/mss157] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Translation termination is accomplished by proteins of the Class I release factor family (RF) that recognize stop codons and catalyze the ribosomal release of the newly synthesized peptide. Bacteria have two canonical RFs: RF1 recognizes UAA and UAG, RF2 recognizes UAA and UGA. Despite that these two release factor proteins are sufficient for de facto translation termination, the eukaryotic organellar RF protein family, which has evolved from bacterial release factors, has expanded considerably, comprising multiple subfamilies, most of which have not been functionally characterized or formally classified. Here, we integrate multiple sources of information to analyze the remarkable differentiation of the RF family among organelles. We document the origin, phylogenetic distribution and sequence structure features of the mitochondrial and plastidial release factors: mtRF1a, mtRF1, mtRF2a, mtRF2b, mtRF2c, ICT1, C12orf65, pRF1, and pRF2, and review published relevant experimental data. The canonical release factors (mtRF1a, mtRF2a, pRF1, and pRF2) and ICT1 are derived from bacterial ancestors, whereas the others have resulted from gene duplications of another release factor. These new RF family members have all lost one or more specific motifs relevant for bona fide release factor function but are mostly targeted to the same organelle as their ancestor. We also characterize the subset of canonical release factor proteins that bear nonclassical PxT/SPF tripeptide motifs and provide a molecular-model-based rationale for their retained ability to recognize stop codons. Finally, we analyze the coevolution of canonical RFs with the organellar genetic code. Although the RF presence in an organelle and its stop codon usage tend to coevolve, we find three taxa that encode an RF2 without using UGA stop codons, and one reverse scenario, where mamiellales green algae use UGA stop codons in their mitochondria without having a mitochondrial type RF2. For the latter, we put forward a “stop-codon reinvention” hypothesis that involves the retargeting of the plastid release factor to the mitochondrion.
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Affiliation(s)
- Isabel Duarte
- Centre for Molecular and Biomolecular Informatics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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21
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Klinge S, Voigts-Hoffmann F, Leibundgut M, Ban N. Atomic structures of the eukaryotic ribosome. Trends Biochem Sci 2012; 37:189-98. [DOI: 10.1016/j.tibs.2012.02.007] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Revised: 02/10/2012] [Accepted: 02/16/2012] [Indexed: 12/20/2022]
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22
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Vivanco-Domínguez S, Bueno-Martínez J, León-Avila G, Iwakura N, Kaji A, Kaji H, Guarneros G. Protein synthesis factors (RF1, RF2, RF3, RRF, and tmRNA) and peptidyl-tRNA hydrolase rescue stalled ribosomes at sense codons. J Mol Biol 2012; 417:425-39. [PMID: 22326347 DOI: 10.1016/j.jmb.2012.02.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 01/17/2012] [Accepted: 02/03/2012] [Indexed: 10/14/2022]
Abstract
During translation, ribosomes stall on mRNA when the aminoacyl-tRNA to be read is not readily available. The stalled ribosomes are deleterious to the cell and should be rescued to maintain its viability. To investigate the contribution of some of the cellular translation factors on ribosome rescuing, we provoked stalling at AGA codons in mutants that affected the factors and then analyzed the accumulation of oligopeptidyl (peptides of up to 6 amino acid residues, oligopep-)-tRNA or polypeptidyl (peptides of more than 300 amino acids in length, polypep-)-tRNA associated with ribosomes. Stalling was achieved by starvation for aminoacyl-tRNA(Arg4) upon induced expression of engineered lacZ (β-galactosidase) reporter gene harboring contiguous AGA codons close to the initiation codon or at internal codon positions together with minigene ATGAGATAA accompanied by reduced peptidyl-tRNA hydrolase (Pth). Our results showed accumulations of peptidyl-tRNA associated with ribosomes in mutants for release factors (RF1, RF2, and RF3), ribosome recycling factor (RRF), Pth, and transfer-messenger RNA (tmRNA), implying that each of these factors cooperate in rescuing stalled ribosomes. The role of these factors in ribosome releasing from the stalled complex may vary depending on the length of the peptide in the peptidyl-tRNA. RF3 and RRF rescue stalled ribosomes by "drop-off" of peptidyl-tRNA, while RF1, RF2 (in the absence of termination codon), or Pth may rescue by hydrolyzing the associated peptidyl-tRNA. This is followed by the disassembly of the ribosomal complex of tRNA and mRNA by RRF and elongation factor G.
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Affiliation(s)
- Serafín Vivanco-Domínguez
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, P.O. Box 14-740, Mexico City, 07000, Mexico
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23
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Napthine S, Yek C, Powell ML, Brown TDK, Brierley I. Characterization of the stop codon readthrough signal of Colorado tick fever virus segment 9 RNA. RNA (NEW YORK, N.Y.) 2012; 18:241-252. [PMID: 22190746 PMCID: PMC3264911 DOI: 10.1261/rna.030338.111] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 11/06/2011] [Indexed: 05/31/2023]
Abstract
Termination codon readthrough is utilized as a mechanism of expression of a growing number of viral and cellular proteins, but in many cases the mRNA signals that promote readthrough are poorly characterized. Here, we investigated the readthrough signal of Colorado tick fever virus (CTFV) segment 9 RNA (Seg-9). CTFV is the type-species of the genus Coltivirus within the family Reoviridae and is a tick-borne, double-stranded, segmented RNA virus. Seg-9 encodes a 36-kDa protein VP9, and by readthrough of a UGA stop codon, a 65-kDa product, VP9'. Using a reporter system, we defined the minimal sequence requirements for readthrough and confirmed activity in both mammalian and insect cell-free translation systems, and in transfected mammalian cells. Mutational analysis revealed that readthrough was UGA specific, and that the local sequence context around the UGA influenced readthrough efficiency. Readthrough was also dependent upon a stable RNA stem-loop structure beginning eight bases downstream from the UGA codon. Mutational analysis of this stem-loop revealed a requirement for the stem region but not for substructures identified within the loop. Unexpectedly, we were unable to detect a ribosomal pause during translation of the CTFV signal, suggesting that the mechanism of readthrough, at least at this site, is unlikely to be dependent upon RNA secondary-structure induced ribosomal pausing at the recoded stop codon.
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Affiliation(s)
- Sawsan Napthine
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Christina Yek
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Michael L. Powell
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - T. David K. Brown
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
| | - Ian Brierley
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge CB2 1QP, United Kingdom
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Quality control of mRNA decoding on the bacterial ribosome. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2012; 86:95-128. [PMID: 22243582 DOI: 10.1016/b978-0-12-386497-0.00003-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The ribosome is a major player in providing accurate gene expression in the cell. The fidelity of substrate selection is tightly controlled throughout the translation process, including the initiation, elongation, and termination phases. Although each phase of translation involves different players, that is, translation factors and tRNAs, the general principles of selection appear surprisingly similar for very different substrates. At essentially every step of translation, differences in complex stabilities as well as induced fit are sources of selectivity. A view starts to emerge of how the ribosome uses local and global conformational switches to govern induced-fit mechanisms that ensure fidelity. This review describes the mechanisms of tRNA and mRNA selection at all phases of protein synthesis in bacteria.
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25
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In vitro and in vivo single-molecule fluorescence imaging of ribosome-catalyzed protein synthesis. Curr Opin Chem Biol 2011; 15:853-63. [PMID: 22104181 DOI: 10.1016/j.cbpa.2011.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Revised: 11/01/2011] [Accepted: 11/01/2011] [Indexed: 11/22/2022]
Abstract
Combined with the availability of highly purified, fluorescently labeled in vitro translation systems, the advent of single-molecule fluorescence imaging has ushered in a new era in high-resolution mechanistic studies of ribosome-catalyzed protein synthesis, or translation. Together with ensemble biochemical investigations of translation and structural studies of functional ribosomal complexes, in vitro single-molecule fluorescence imaging of protein synthesis is providing unique mechanistic insight into this fundamental biological process. More recently, rapidly evolving breakthroughs in fluorescence-based molecular imaging in live cells with sub-diffraction-limit spatial resolution and ever-increasing temporal resolution provide great promise for conducting mechanistic studies of translation and its regulation in living cells. Here we review the remarkable recent progress that has been made in these fields, highlight important mechanistic insights that have been gleaned from these studies thus far, and discuss what we envision lies ahead as these approaches continue to evolve and expand to address increasingly complex mechanistic and regulatory aspects of translation.
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26
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Wittinghofer A, Vetter IR. Structure-function relationships of the G domain, a canonical switch motif. Annu Rev Biochem 2011; 80:943-71. [PMID: 21675921 DOI: 10.1146/annurev-biochem-062708-134043] [Citation(s) in RCA: 333] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
GTP-binding (G) proteins constitute a class of P-loop (phosphate-binding loop) proteins that work as molecular switches between the GDP-bound OFF and the GTP-bound ON state. The common principle is the 160-180-residue G domain with an α,β topology that is responsible for nucleotide-dependent conformational changes and drives many biological functions. Although the G domain uses a universally conserved switching mechanism, its structure, function, and GTPase reaction are modified for many different pathways and processes.
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27
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Klaholz BP. Molecular recognition and catalysis in translation termination complexes. Trends Biochem Sci 2011; 36:282-92. [DOI: 10.1016/j.tibs.2011.02.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 02/01/2011] [Accepted: 02/04/2011] [Indexed: 11/16/2022]
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28
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Chadani Y, Ono K, Kutsukake K, Abo T. Escherichia coli YaeJ protein mediates a novel ribosome-rescue pathway distinct from SsrA- and ArfA-mediated pathways. Mol Microbiol 2011; 80:772-85. [DOI: 10.1111/j.1365-2958.2011.07607.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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O'Connor M, Gregory ST. Inactivation of the RluD pseudouridine synthase has minimal effects on growth and ribosome function in wild-type Escherichia coli and Salmonella enterica. J Bacteriol 2011; 193:154-62. [PMID: 21037010 PMCID: PMC3019933 DOI: 10.1128/jb.00970-10] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Accepted: 10/18/2010] [Indexed: 11/20/2022] Open
Abstract
The Escherichia coli rluD gene encodes a pseudouridine synthase responsible for the pseudouridine (Ψ) modifications at positions 1911, 1915, and 1917 in helix 69 of 23S rRNA. It has been reported that deletion of rluD in K-12 strains of E. coli is associated with extremely slow growth, increased readthrough of stop codons, and defects in 50S ribosomal subunit assembly and 30S-50S subunit association. Suppressor mutations in the prfB and prfC genes encoding release factor 2 (RF2) and RF3 that restore the wild type-growth rate and also correct the ribosomal defects have now been isolated. These suppressors link helix 69 Ψ residues with the termination phase of protein synthesis. However, further genetic analysis reported here also reveals that the slow growth and other defects associated with inactivation of rluD in E. coli K-12 strains are due to a defective RF2 protein, with a threonine at position 246, which is present in all K-12 strains. This is in contrast to the more typical alanine found at this position in most bacterial RF2s, including those of other E. coli strains. Inactivation of rluD in E. coli strains containing the prfB allele from E. coli B or in Salmonella enterica, both carrying an RF2 with Ala246, has negligible effects on growth, termination, or ribosome function. The results indicate that, in contrast to those in wild bacteria, termination functions in E. coli K-12 strains carrying a partially defective RF2 protein are especially susceptible to perturbation of ribosome-RF interactions, such as that caused by loss of h69 Ψ modifications.
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Affiliation(s)
- Michael O'Connor
- School of Biological Sciences, University of Missouri-Kansas City, 5007 Rockhill Rd, Kansas City, Missouri 64110, USA.
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30
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Multifactorial determinants of protein expression in prokaryotic open reading frames. J Mol Biol 2010; 402:905-18. [PMID: 20727358 DOI: 10.1016/j.jmb.2010.08.010] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 07/27/2010] [Accepted: 08/05/2010] [Indexed: 01/21/2023]
Abstract
A quantitative description of the relationship between protein expression levels and open reading frame (ORF) nucleotide sequences is important for understanding natural systems, designing synthetic systems, and optimizing heterologous expression. Codon identity, mRNA secondary structure, and nucleotide composition within ORFs markedly influence expression levels. Bioinformatic analysis of ORF sequences in 816 bacterial genomes revealed that these features show distinct regional trends. To investigate their effects on protein expression, we designed 285 synthetic genes and determined corresponding expression levels in vitro using Escherichia coli extracts. We developed a mathematical function, parameterized using this synthetic gene data set, which enables computation of protein expression levels from ORF nucleotide sequences. In addition to its practical application in the design of heterologous expression systems, this equation provides mechanistic insight into the factors that control translation efficiency. We found that expression is strongly dependent on the presence of high AU content and low secondary structure in the ORF 5' region. Choice of high-frequency codons contributes to a lesser extent. The 3' terminal AU content makes modest, but detectable contributions. We present a model for the effect of these factors on the three phases of ribosomal function: initiation, elongation, and termination.
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Young DJ, Edgar CD, Poole ES, Tate WP. The codon specificity of eubacterial release factors is determined by the sequence and size of the recognition loop. RNA (NEW YORK, N.Y.) 2010; 16:1623-33. [PMID: 20584893 PMCID: PMC2905760 DOI: 10.1261/rna.2117010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The two codon-specific eubacterial release factors (RF1: UAA/UAG and RF2: UAA/UGA) have specific tripeptide motifs (PXT/SPF) within an exposed recognition loop shown in recent structures to interact with stop codons during protein synthesis termination. The motifs have been inferred to be critical for codon specificity, but this study shows that they are insufficient to determine specificity alone. Swapping the motifs or the entire loop between factors resulted in a loss of codon recognition rather than a switch of codon specificity. From a study of chimeric eubacterial RF1/RF2 recognition loops and an atypical shorter variant in Caenorhabditis elegans mitochondrial RF1 that lacks the classical tripeptide motif PXT, key determinants throughout the whole loop have been defined. It reveals that more than one configuration of the recognition loop based on specific sequence and size can achieve the same desired codon specificity. This study has provided unexpected insight into why a combination of the two factors is necessary in eubacteria to exclude recognition of UGG as stop.
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Affiliation(s)
- David J Young
- Department of Biochemistry, University of Otago, Dunedin 9054, New Zealand
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Antonicka H, Østergaard E, Sasarman F, Weraarpachai W, Wibrand F, Pedersen AMB, Rodenburg RJ, van der Knaap MS, Smeitink JA, Chrzanowska-Lightowlers ZM, Shoubridge EA. Mutations in C12orf65 in patients with encephalomyopathy and a mitochondrial translation defect. Am J Hum Genet 2010; 87:115-22. [PMID: 20598281 DOI: 10.1016/j.ajhg.2010.06.004] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 05/20/2010] [Accepted: 06/04/2010] [Indexed: 10/19/2022] Open
Abstract
We investigated the genetic basis for a global and uniform decrease in mitochondrial translation in fibroblasts from patients in two unrelated pedigrees who developed Leigh syndrome, optic atrophy, and ophthalmoplegia. Analysis of the assembly of the oxidative phosphorylation complexes showed severe decreases of complexes I, IV, and V and a smaller decrease in complex III. The steady-state levels of mitochondrial mRNAs, tRNAs, and rRNAs were not reduced, nor were those of the mitochondrial translation elongation factors or the protein components of the mitochondrial ribosome. Using homozygosity mapping, we identified a 1 bp deletion in C12orf65 in one patient, and DNA sequence analysis showed a different 1 bp deletion in the second patient. Both mutations predict the same premature stop codon. C12orf65 belongs to a family of four mitochondrial class I peptide release factors, which also includes mtRF1a, mtRF1, and Ict1, all characterized by the presence of a GGQ motif at the active site. However, C12orf65 does not exhibit peptidyl-tRNA hydrolase activity in an in vitro assay with bacterial ribosomes. We suggest that it might play a role in recycling abortive peptidyl-tRNA species, released from the ribosome during the elongation phase of translation.
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Young DJ, Edgar CD, Murphy J, Fredebohm J, Poole ES, Tate WP. Bioinformatic, structural, and functional analyses support release factor-like MTRF1 as a protein able to decode nonstandard stop codons beginning with adenine in vertebrate mitochondria. RNA (NEW YORK, N.Y.) 2010; 16:1146-55. [PMID: 20421313 PMCID: PMC2874167 DOI: 10.1261/rna.1970310] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Vertebrate mitochondria use stop codons UAA and UAG decoded by the release factor (RF) MTRF1L and two reassigned arginine codons, AGA and AGG. A second highly conserved RF-like factor, MTRF1, which evolved from a gene duplication of an ancestral mitochondrial RF1 and not a RF2, is a good candidate for recognizing the nonstandard codons. MTRF1 differs from other RFs by having insertions in the two external loops important for stop codon recognition (tip of helix alpha5 and recognition loop) and by having key substitutions that are involved in stop codon interactions in eubacterial RF/ribosome structures. These changes may allow recognition of the larger purine base in the first position of AGA/G and, uniquely for RFs, only of G at position 2. In contrast, residues that support A and G recognition in the third position in RF1 are conserved as would be required for recognition of AGA and AGG. Since an assay with vertebrate mitochondrial ribosomes has not been established, we modified Escherichia coli RF1 at the helix alpha5 and recognition loop regions to mimic MTRF1. There was loss of peptidyl-tRNA hydrolysis activity with standard stop codons beginning with U (e.g., UAG), but a gain of activity with codons beginning with A (AAG in particular). A lower level of activity with AGA could be enhanced by solvent modification. These observations imply that MTRF1 has the characteristics to recognize A as the first base of a stop codon as would be required to decode the nonstandard codons AGA and AGG.
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Affiliation(s)
- David J Young
- Department of Biochemistry, University of Otago, Dunedin 9054, New Zealand
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Harigaya Y, Parker R. No-go decay: a quality control mechanism for RNA in translation. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:132-41. [PMID: 21956910 DOI: 10.1002/wrna.17] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Eukaryotic cells have evolved multiple quality control mechanisms that recognize and eliminate defective mRNA during the process of translation. One mechanism, referred to as No-go decay (NGD), targets mRNAs with elongation stalls for degradation initiated by endonucleolytic cleavage in the vicinity of the stalled ribosome. NGD is promoted by the evolutionarily conserved Dom34 and Hbs1 proteins, which are related to the translation termination factors eRF1 and eRF3, respectively. NGD is likely to occur by Dom34/Hbs1 interacting with the A site in the ribosome leading to release of the peptide or peptidyl-tRNA. The process of NGD and/or the function of Dom34/Hbs1 appear to be important in several different biological contexts.
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Affiliation(s)
- Yuriko Harigaya
- Department of Molecular and Cellular Biology, Howard Hughes Medical Institute, University of Arizona, Tucson, AZ 85721-0106, USA
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35
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Pisarev AV, Skabkin MA, Pisareva VP, Skabkina OV, Rakotondrafara AM, Hentze MW, Hellen CUT, Pestova TV. The role of ABCE1 in eukaryotic posttermination ribosomal recycling. Mol Cell 2010; 37:196-210. [PMID: 20122402 DOI: 10.1016/j.molcel.2009.12.034] [Citation(s) in RCA: 249] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Revised: 11/23/2009] [Accepted: 12/23/2009] [Indexed: 01/20/2023]
Abstract
After termination, eukaryotic 80S ribosomes remain associated with mRNA, P-site deacylated tRNA, and release factor eRF1 and must be recycled by dissociating these ligands and separating ribosomes into subunits. Although recycling of eukaryotic posttermination complexes (post-TCs) can be mediated by initiation factors eIF3, eIF1, and eIF1A (Pisarev et al., 2007), this energy-free mechanism can function only in a narrow range of low Mg(2+) concentrations. Here, we report that ABCE1, a conserved and essential member of the ATP-binding cassette (ABC) family of proteins, promotes eukaryotic ribosomal recycling over a wide range of Mg(2+) concentrations. ABCE1 dissociates post-TCs into free 60S subunits and mRNA- and tRNA-bound 40S subunits. It can hydrolyze ATP, GTP, UTP, and CTP. NTP hydrolysis by ABCE1 is stimulated by post-TCs and is required for its recycling activity. Importantly, ABCE1 dissociates only post-TCs obtained with eRF1/eRF3 (or eRF1 alone), but not post-TCs obtained with puromycin in eRF1's absence.
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Affiliation(s)
- Andrey V Pisarev
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
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36
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Baudin-Baillieu A, Fabret C, Liang XH, Piekna-Przybylska D, Fournier MJ, Rousset JP. Nucleotide modifications in three functionally important regions of the Saccharomyces cerevisiae ribosome affect translation accuracy. Nucleic Acids Res 2010; 37:7665-77. [PMID: 19820108 PMCID: PMC2794176 DOI: 10.1093/nar/gkp816] [Citation(s) in RCA: 104] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Important regions of rRNA are rich in nucleotide modifications that can have strong effects on ribosome biogenesis and translation efficiency. Here, we examine the influence of pseudouridylation and 2′-O-methylation on translation accuracy in yeast, by deleting the corresponding guide snoRNAs. The regions analyzed were: the decoding centre (eight modifications), and two intersubunit bridge domains—the A-site finger and Helix 69 (six and five modifications). Results show that a number of modifications influence accuracy with effects ranging from 0.3- to 2.4-fold of wild-type activity. Blocking subsets of modifications, especially from the decoding region, impairs stop codon termination and reading frame maintenance. Unexpectedly, several Helix 69 mutants possess ribosomes with increased fidelity. Consistent with strong positional and synergistic effects is the finding that single deletions can have a more pronounced phenotype than multiple deficiencies in the same region. Altogether, the results demonstrate that rRNA modifications have significant roles in translation accuracy.
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37
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Fraser CS. The molecular basis of translational control. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:1-51. [PMID: 20374738 DOI: 10.1016/s1877-1173(09)90001-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Our current understanding of eukaryotic protein synthesis has emerged from many years of biochemical, genetic and biophysical approaches. Significant insight into the molecular details of the mechanism has been obtained, although there are clearly many aspects of the process that remain to be resolved. Importantly, our understanding of the mechanism has identified a number of key stages in the pathway that contribute to the regulation of general and gene-specific translation. Not surprisingly, translational control is now widely accepted to play a role in aspects of cell stress, growth, development, synaptic function, aging, and disease. This chapter reviews the mechanism of eukaryotic protein synthesis and its relevance to translational control.
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Affiliation(s)
- Christopher S Fraser
- Department of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616, USA
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38
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Munro JB, Sanbonmatsu KY, Spahn CMT, Blanchard SC. Navigating the ribosome's metastable energy landscape. Trends Biochem Sci 2009; 34:390-400. [PMID: 19647434 DOI: 10.1016/j.tibs.2009.04.004] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 04/28/2009] [Accepted: 04/28/2009] [Indexed: 12/30/2022]
Abstract
The molecular mechanisms by which tRNA molecules enter and transit the ribosome during mRNA translation remains elusive. However, recent genetic, biochemical and structural studies offer important new findings into the ordered sequence of events underpinning the translocation process that help place the molecular mechanism within reach. In particular, new structural and kinetic insights have been obtained regarding tRNA movements through 'hybrid state' configurations. These dynamic views reveal that the macromolecular ribosome particle, like many smaller proteins, has an intrinsic capacity to reversibly sample an ensemble of similarly stable native states. Such perspectives suggest that substrates, factors and environmental cues contribute to translation regulation by helping the dynamic system navigate through a highly complex and metastable energy landscape.
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Affiliation(s)
- James B Munro
- Department of Physiology and Biophysics, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10021, USA
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39
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Garai A, Chowdhury D, Chowdhury D, Ramakrishnan TV. Stochastic kinetics of ribosomes: single motor properties and collective behavior. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:011908. [PMID: 19658730 DOI: 10.1103/physreve.80.011908] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Revised: 06/04/2009] [Indexed: 05/28/2023]
Abstract
Syntheses of protein molecules in a cell are carried out by ribosomes. A ribosome can be regarded as a molecular motor which utilizes the input chemical energy to move on a messenger RNA (mRNA) track that also serves as a template for the polymerization of the corresponding protein. The forward movement, however, is characterized by an alternating sequence of translocation and pause. Using a quantitative model, which captures the mechanochemical cycle of an individual ribosome, we derive an exact analytical expression for the distribution of its dwell times at the successive positions on the mRNA track. Inverse of the average dwell time satisfies a "Michaelis-Menten-type" equation and is consistent with the general formula for the average velocity of a molecular motor with an unbranched mechanochemical cycle. Extending this formula appropriately, we also derive the exact force-velocity relation for a ribosome. Often many ribosomes simultaneously move on the same mRNA track, while each synthesizes a copy of the same protein. We extend the model of a single ribosome by incorporating steric exclusion of different individuals on the same track. We draw the phase diagram of this model of ribosome traffic in three-dimensional spaces spanned by experimentally controllable parameters. We suggest new experimental tests of our theoretical predictions.
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Affiliation(s)
- Ashok Garai
- Department of Physics, Indian Institute of Technology, Kanpur 208016, India
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40
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Passos DO, Doma MK, Shoemaker CJ, Muhlrad D, Green R, Weissman J, Hollien J, Parker R. Analysis of Dom34 and its function in no-go decay. Mol Biol Cell 2009; 20:3025-32. [PMID: 19420139 DOI: 10.1091/mbc.e09-01-0028] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Eukaryotic mRNAs are subject to quality control mechanisms that degrade defective mRNAs. In yeast, mRNAs with stalls in translation elongation are targeted for endonucleolytic cleavage by No-Go decay (NGD). The cleavage triggered by No-Go decay is dependent on Dom34p and Hbs1p, and Dom34 has been proposed to be the endonuclease responsible for mRNA cleavage. We created several Dom34 mutants and examined their effects on NGD in yeast. We identified mutations in several loops of the Dom34 structure that affect NGD. In contrast, mutations inactivating the proposed nuclease domain do not affect NGD in vivo. Moreover, we observed that overexpression of the Rps30a protein, a high copy suppressor of dom34Delta cold sensitivity, can restore some mRNA cleavage in a dom34Delta strain. These results identify important functional regions of Dom34 and suggest that the proposed endonuclease activity of Dom34 is not required for mRNA cleavage in NGD. We also provide evidence that the process of NGD is conserved in insect cells. On the basis of these results and the process of translation termination, we suggest a multistep model for the process of NGD.
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Affiliation(s)
- Dario O Passos
- University of Arizona, Department of Molecular and Cellular Biology and Howard Hughes Medical Institute, Tucson, AZ 85721, USA
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41
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Nakajima E, Goto Y, Sako Y, Murakami H, Suga H. Ribosomal Synthesis of Peptides with C-Terminal Lactams, Thiolactones, and Alkylamides. Chembiochem 2009; 10:1186-92. [DOI: 10.1002/cbic.200900058] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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42
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Andér M, Åqvist J. Does Glutamine Methylation Affect the Intrinsic Conformation of the Universally Conserved GGQ Motif in Ribosomal Release Factors? Biochemistry 2009; 48:3483-9. [DOI: 10.1021/bi900117r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Martin Andér
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
| | - Johan Åqvist
- Department of Cell and Molecular Biology, Uppsala University, Biomedical Center, Box 596, SE-751 24 Uppsala, Sweden
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43
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Ribosome: an Ancient Cellular Nano-Machine for Genetic Code Translation. NATO SCIENCE FOR PEACE AND SECURITY SERIES B: PHYSICS AND BIOPHYSICS 2009. [DOI: 10.1007/978-90-481-2368-1_8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Rorbach J, Richter R, Wessels HJ, Wydro M, Pekalski M, Farhoud M, Kühl I, Gaisne M, Bonnefoy N, Smeitink JA, Lightowlers RN, Chrzanowska-Lightowlers ZMA. The human mitochondrial ribosome recycling factor is essential for cell viability. Nucleic Acids Res 2008; 36:5787-99. [PMID: 18782833 PMCID: PMC2566884 DOI: 10.1093/nar/gkn576] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The molecular mechanism of human mitochondrial translation has yet to be fully described. We are particularly interested in understanding the process of translational termination and ribosome recycling in the mitochondrion. Several candidates have been implicated, for which subcellular localization and characterization have not been reported. Here, we show that the putative mitochondrial recycling factor, mtRRF, is indeed a mitochondrial protein. Expression of human mtRRF in fission yeast devoid of endogenous mitochondrial recycling factor suppresses the respiratory phenotype. Further, human mtRRF is able to associate with Escherichia coli ribosomes in vitro and can associate with mitoribosomes in vivo. Depletion of mtRRF in human cell lines is lethal, initially causing profound mitochondrial dysmorphism, aggregation of mitoribosomes, elevated mitochondrial superoxide production and eventual loss of OXPHOS complexes. Finally, mtRRF was shown to co-immunoprecipitate a large number of mitoribosomal proteins attached to other mitochondrial proteins, including putative members of the mitochondrial nucleoid.
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Affiliation(s)
- Joanna Rorbach
- Mitochondrial Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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