51
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Darnell AM, Subramaniam AR, O'Shea EK. Translational Control through Differential Ribosome Pausing during Amino Acid Limitation in Mammalian Cells. Mol Cell 2019; 71:229-243.e11. [PMID: 30029003 DOI: 10.1016/j.molcel.2018.06.041] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/07/2018] [Accepted: 06/26/2018] [Indexed: 12/22/2022]
Abstract
Limitation for amino acids is thought to regulate translation in mammalian cells primarily by signaling through the kinases mTORC1 and GCN2. We find that a selective loss of arginine tRNA charging during limitation for arginine regulates translation through ribosome pausing at two of six arginine codons. Surprisingly, limitation for leucine, an essential and abundant amino acid in protein, results in little or no ribosome pausing. Chemical and genetic perturbation of mTORC1 and GCN2 signaling revealed that their robust response to leucine limitation prevents ribosome pausing, while an insufficient response to arginine limitation leads to loss of tRNA charging and ribosome pausing. Ribosome pausing decreases protein production and triggers premature ribosome termination without reducing mRNA levels. Together, our results suggest that amino acids that are not optimally sensed by the mTORC1 and GCN2 pathways still regulate translation through an evolutionarily conserved mechanism based on codon-specific ribosome pausing.
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Affiliation(s)
- Alicia M Darnell
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Arvind R Subramaniam
- Basic Sciences Division and Computational Biology Program of Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
| | - Erin K O'Shea
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA; Howard Hughes Medical Institute, Harvard University, Cambridge, MA 02138, USA; Department of Chemistry and Chemical Biology and Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, MA 02138, USA.
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52
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Mohammad F, Green R, Buskirk AR. A systematically-revised ribosome profiling method for bacteria reveals pauses at single-codon resolution. eLife 2019; 8:e42591. [PMID: 30724162 PMCID: PMC6377232 DOI: 10.7554/elife.42591] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 02/05/2019] [Indexed: 12/17/2022] Open
Abstract
In eukaryotes, ribosome profiling provides insight into the mechanism of protein synthesis at the codon level. In bacteria, however, the method has been more problematic and no consensus has emerged for how to best prepare profiling samples. Here, we identify the sources of these problems and describe new solutions for arresting translation and harvesting cells in order to overcome them. These improvements remove confounding artifacts and improve the resolution to allow analyses of ribosome behavior at the codon level. With a clearer view of the translational landscape in vivo, we observe that filtering cultures leads to translational pauses at serine and glycine codons through the reduction of tRNA aminoacylation levels. This observation illustrates how bacterial ribosome profiling studies can yield insight into the mechanism of protein synthesis at the codon level and how these mechanisms are regulated in response to changes in the physiology of the cell.
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Affiliation(s)
- Fuad Mohammad
- Department of Molecular Biology and GeneticsJohns Hopkins University School of MedicineBaltimoreUnited States
| | - Rachel Green
- Department of Molecular Biology and GeneticsJohns Hopkins University School of MedicineBaltimoreUnited States
- Howard Hughes Medical Institute, Johns Hopkins University School of MedicineBaltimoreUnited States
| | - Allen R Buskirk
- Department of Molecular Biology and GeneticsJohns Hopkins University School of MedicineBaltimoreUnited States
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53
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Abstract
Ribosome profiling accesses the translational step of gene expression via deep sequencing of ribosome-protected mRNA footprints. Pairing of ribosome profiling and transcriptomics data provides a translational efficiency for each gene. Here, the translatome and transcriptome of the model cyanobacterium
Synechocystis
were compared under carbon-replete and carbon starvation conditions. The latter may be experienced when cyanobacteria are cultivated in poorly mixed bioreactors or engineered to be product-secreting cell factories. A small fraction of genes (<200), including stress response genes, showed changes in translational efficiency during carbon starvation, indicating condition-dependent translation-level regulation. We observed ribosome occupancy in untranslated regions, possibly due to an alternative translation initiation mechanism in
Synechocystis.
The higher proportion of ribosomes residing in untranslated regions during carbon starvation may be a mechanism to quickly inactivate superfluous ribosomes. This work provides the first ribosome profiling data for cyanobacteria and reveals new regulation strategies for coping with nutrient limitation.
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54
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Dao Duc K, Saleem ZH, Song YS. Theoretical analysis of the distribution of isolated particles in totally asymmetric exclusion processes: Application to mRNA translation rate estimation. Phys Rev E 2018; 97:012106. [PMID: 29448386 DOI: 10.1103/physreve.97.012106] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Indexed: 11/07/2022]
Abstract
The Totally Asymmetric Exclusion Process (TASEP) is a classical stochastic model for describing the transport of interacting particles, such as ribosomes moving along the messenger ribonucleic acid (mRNA) during translation. Although this model has been widely studied in the past, the extent of collision between particles and the average distance between a particle to its nearest neighbor have not been quantified explicitly. We provide here a theoretical analysis of such quantities via the distribution of isolated particles. In the classical form of the model in which each particle occupies only a single site, we obtain an exact analytic solution using the matrix ansatz. We then employ a refined mean-field approach to extend the analysis to a generalized TASEP with particles of an arbitrary size. Our theoretical study has direct applications in mRNA translation and the interpretation of experimental ribosome profiling data. In particular, our analysis of data from Saccharomyces cerevisiae suggests a potential bias against the detection of nearby ribosomes with a gap distance of less than approximately three codons, which leads to some ambiguity in estimating the initiation rate and protein production flux for a substantial fraction of genes. Despite such ambiguity, however, we demonstrate theoretically that the interference rate associated with collisions can be robustly estimated and show that approximately 1% of the translating ribosomes get obstructed.
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Affiliation(s)
- Khanh Dao Duc
- Computer Science Division, University of California, Berkeley, California 94720, USA
| | - Zain H Saleem
- Department of Mathematics, University of Pennsylvania, Pennsylvania 19104, USA
| | - Yun S Song
- Computer Science Division and Department of Statistics, University of California, Berkeley, California 94720, USA
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55
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Du MZ, Wei W, Qin L, Liu S, Zhang AY, Zhang Y, Zhou H, Guo FB. Co-adaption of tRNA gene copy number and amino acid usage influences translation rates in three life domains. DNA Res 2018; 24:623-633. [PMID: 28992099 PMCID: PMC5726483 DOI: 10.1093/dnares/dsx030] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 06/15/2017] [Indexed: 12/01/2022] Open
Abstract
Although more and more entangled participants of translation process were realized, how they cooperate and co-determine the final translation efficiency still lacks details. Here, we reasoned that the basic translation components, tRNAs and amino acids should be consistent to maximize the efficiency and minimize the cost. We firstly revealed that 310 out of 410 investigated genomes of three domains had significant co-adaptions between the tRNA gene copy numbers and amino acid compositions, indicating that maximum efficiency constitutes ubiquitous selection pressure on protein translation. Furthermore, fast-growing and larger bacteria are found to have significantly better co-adaption and confirmed the effect of this pressure. Within organism, highly expressed proteins and those connected to acute responses have higher co-adaption intensity. Thus, the better co-adaption probably speeds up the growing of cells through accelerating the translation of special proteins. Experimentally, manipulating the tRNA gene copy number to optimize co-adaption between enhanced green fluorescent protein (EGFP) and tRNA gene set of Escherichia coli indeed lifted the translation rate (speed). Finally, as a newly confirmed translation rate regulating mechanism, the co-adaption reflecting translation rate not only deepens our understanding on translation process but also provides an easy and practicable method to improve protein translation rates and productivity.
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Affiliation(s)
| | - Wen Wei
- School of Life Science and Technology
| | - Lei Qin
- School of Life Science and Technology
| | - Shuo Liu
- School of Life Science and Technology
| | - An-Ying Zhang
- School of Life Science and Technology.,Centre for Informational Biology
| | - Yong Zhang
- School of Life Science and Technology.,Centre for Informational Biology
| | - Hong Zhou
- School of Life Science and Technology.,Centre for Informational Biology
| | - Feng-Biao Guo
- School of Life Science and Technology.,Centre for Informational Biology.,Key Laboratory for Neuroinformation of the Ministry of Education, University of Electronic Science and Technology of China, Chengdu, China
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56
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Abrahams L, Hurst LD. Adenine Enrichment at the Fourth CDS Residue in Bacterial Genes Is Consistent with Error Proofing for +1 Frameshifts. Mol Biol Evol 2018; 34:3064-3080. [PMID: 28961919 PMCID: PMC5850271 DOI: 10.1093/molbev/msx223] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Beyond selection for optimal protein functioning, coding sequences (CDSs) are under selection at the RNA and DNA levels. Here, we identify a possible signature of “dual-coding,” namely extensive adenine (A) enrichment at bacterial CDS fourth sites. In 99.07% of studied bacterial genomes, fourth site A use is greater than expected given genomic A-starting codon use. Arguing for nucleotide level selection, A-starting serine and arginine second codons are heavily utilized when compared with their non-A starting synonyms. Several models have the ability to explain some of this trend. In part, A-enrichment likely reduces 5′ mRNA stability, promoting translation initiation. However T/U, which may also reduce stability, is avoided. Further, +1 frameshifts on the initiating ATG encode a stop codon (TGA) provided A is the fourth residue, acting either as a frameshift “catch and destroy” or a frameshift stop and adjust mechanism and hence implicated in translation initiation. Consistent with both, genomes lacking TGA stop codons exhibit weaker fourth site A-enrichment. Sequences lacking a Shine–Dalgarno sequence and those without upstream leader genes, that may be more error prone during initiation, have greater utilization of A, again suggesting a role in initiation. The frameshift correction model is consistent with the notion that many genomic features are error-mitigation factors and provides the first evidence for site-specific out of frame stop codon selection. We conjecture that the NTG universal start codon may have evolved as a consequence of TGA being a stop codon and the ability of NTGA to rapidly terminate or adjust a ribosome.
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Affiliation(s)
- Liam Abrahams
- Department of Biology and Biochemistry, The Milner Centre for Evolution, University of Bath, Bath, United Kingdom
| | - Laurence D Hurst
- Department of Biology and Biochemistry, The Milner Centre for Evolution, University of Bath, Bath, United Kingdom
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57
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Zarai Y, Margaliot M, Sontag ED, Tuller T. Controllability Analysis and Control Synthesis for the Ribosome Flow Model. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2018; 15:1351-1364. [PMID: 28541906 PMCID: PMC5778923 DOI: 10.1109/tcbb.2017.2707420] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The ribosomal density along different parts of the coding regions of the mRNA molecule affects various fundamental intracellular phenomena including: protein production rates, global ribosome allocation and organismal fitness, ribosomal drop off, co-translational protein folding, mRNA degradation, and more. Thus, regulating translation in order to obtain a desired ribosomal profile along the mRNA molecule is an important biological problem. We study this problem by using a dynamical model for mRNA translation, called the ribosome flow model (RFM). In the RFM, the mRNA molecule is modeled as an ordered chain of $n$ sites. The RFM includes $n$ state-variables describing the ribosomal density profile along the mRNA molecule, and the transition rates from each site to the next are controlled by $n+1$ positive constants. To study the problem of controlling the density profile, we consider some or all of the transition rates as time-varying controls. We consider the following problem: given an initial and a desired ribosomal density profile in the RFM, determine the time-varying values of the transition rates that steer the system to the desired density profile, if they exist. More specifically, we consider two control problems. In the first, all transition rates can be regulated separately, and the goal is to steer the ribosomal density profile and the protein production rate from a given initial value to a desired value. In the second problem, one or more transition rates are jointly regulated by a single scalar control, and the goal is to steer the production rate to a desired value within a certain set of feasible values. In the first case, we show that the system is controllable, i.e., the control is powerful enough to steer the system to any desired value in finite time, and provide simple closed-form expressions for constant positive control functions (or transition rates) that asymptotically steer the system to the desired value. In the second case, we show that the system is controllable, and provide a simple algorithm for determining the constant positive control value that asymptotically steers the system to the desired value. We discuss some of the biological implications of these results.
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58
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Rojas J, Castillo G, Leiva LE, Elgamal S, Orellana O, Ibba M, Katz A. Codon usage revisited: Lack of correlation between codon usage and the number of tRNA genes in enterobacteria. Biochem Biophys Res Commun 2018; 502:450-455. [PMID: 29859934 DOI: 10.1016/j.bbrc.2018.05.168] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 05/25/2018] [Indexed: 01/01/2023]
Abstract
It is widely believed that if a high number of genes are found for any tRNA in a rapidly replicating bacteria, then the cytoplasmic levels of that tRNA will be high and an open reading frame containing a higher frequency of the complementary codon will be translated faster. This idea is based on correlations between the number of tRNA genes, tRNA concentration and the frequency of codon usage observed in a limited number of strains as well as from the fact that artificially changing the number of tRNA genes alters translation efficiency and consequently the amount of properly folded protein synthesized. tRNA gene number may greatly vary in a genome due to duplications, deletions and lateral transfer which in turn would alter the levels and functionality of many proteins. Such changes are potentially deleterious for fitness and as a result it is expected that changes in tRNA gene numbers should be accompanied by a modification of the frequency of codon usage. In contrast to this model, when comparing the number of tRNA genes and the frequency of codon usage of several Salmonella enterica and Escherichia coli strains we found that changes in the number of tRNA genes are not correlated to changes in codon usage. Furthermore, these changes are not correlated with a change in the efficiency of codon translation. These results suggest that once a genome gains or loses tRNA genes, it responds by modulating the concentrations of tRNAs rather than modifying its frequency of codon usage.
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Affiliation(s)
- Joaquín Rojas
- Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
| | - Gabriel Castillo
- Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
| | - Lorenzo Eugenio Leiva
- Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
| | - Sara Elgamal
- Department of Microbiology and The Center for RNA Biology, Ohio State University, Columbus, OH, 43210, USA
| | - Omar Orellana
- Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
| | - Michael Ibba
- Department of Microbiology and The Center for RNA Biology, Ohio State University, Columbus, OH, 43210, USA
| | - Assaf Katz
- Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile.
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59
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Abstract
RNA is the fundamental information transfer system in the cell. The ability to follow single messenger RNAs (mRNAs) from transcription to degradation with fluorescent probes gives quantitative information about how the information is transferred from DNA to proteins. This review focuses on the latest technological developments in the field of single-mRNA detection and their usage to study gene expression in both fixed and live cells. By describing the application of these imaging tools, we follow the journey of mRNA from transcription to decay in single cells, with single-molecule resolution. We review current theoretical models for describing transcription and translation that were generated by single-molecule and single-cell studies. These methods provide a basis to study how single-molecule interactions generate phenotypes, fundamentally changing our understating of gene expression regulation.
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Affiliation(s)
- Evelina Tutucci
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461;,
| | - Nathan M. Livingston
- Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Robert H. Singer
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461;,
- Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, New York 10461
- Cellular Imaging Consortium, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147
| | - Bin Wu
- Center for Cell Dynamics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland 21205;,
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60
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tRNA tracking for direct measurements of protein synthesis kinetics in live cells. Nat Chem Biol 2018; 14:618-626. [PMID: 29769736 PMCID: PMC6124642 DOI: 10.1038/s41589-018-0063-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 04/09/2018] [Indexed: 11/30/2022]
Abstract
Our ability to directly relate results from test tube biochemical experiments to the kinetics in living cells is very limited. Here we present experimental and analytical tools to directly study the kinetics of fast biochemical reactions in live cells. Dye-labeled molecules are electroporated into bacterial cells and tracked using super-resolved single-molecule microscopy. Trajectories are analyzed by machine-learning algorithms to directly monitor transitions between bound and free states. In particular, we measure the dwell-time of tRNAs on ribosomes, and hence achieve direct measurements of translation rates inside living cells at codon resolution. We find elongation rates with tRNAPhe in perfect agreement with previous indirect estimates, and that once fMet-tRNAfMet has bound to the 30S ribosomal subunit, initiation of translation is surprisingly fast and does not limit the overall rate of protein synthesis. The experimental and analytical tools for direct kinetics measurements in live cells have applications far beyond bacterial protein synthesis.
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61
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Codon usage of highly expressed genes affects proteome-wide translation efficiency. Proc Natl Acad Sci U S A 2018; 115:E4940-E4949. [PMID: 29735666 DOI: 10.1073/pnas.1719375115] [Citation(s) in RCA: 114] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although the genetic code is redundant, synonymous codons for the same amino acid are not used with equal frequencies in genomes, a phenomenon termed "codon usage bias." Previous studies have demonstrated that synonymous changes in a coding sequence can exert significant cis effects on the gene's expression level. However, whether the codon composition of a gene can also affect the translation efficiency of other genes has not been thoroughly explored. To study how codon usage bias influences the cellular economy of translation, we massively converted abundant codons to their rare synonymous counterpart in several highly expressed genes in Escherichia coli This perturbation reduces both the cellular fitness and the translation efficiency of genes that have high initiation rates and are naturally enriched with the manipulated codon, in agreement with theoretical predictions. Interestingly, we could alleviate the observed phenotypes by increasing the supply of the tRNA for the highly demanded codon, thus demonstrating that the codon usage of highly expressed genes was selected in evolution to maintain the efficiency of global protein translation.
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62
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Artsimovitch I. Rebuilding the bridge between transcription and translation. Mol Microbiol 2018; 108:467-472. [PMID: 29608805 DOI: 10.1111/mmi.13964] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/01/2018] [Indexed: 12/21/2022]
Abstract
In Bacteria, ribosomes may bind to the nascent RNA emerging from the transcribing RNA polymerase and initiate translation. Transcription-translation coupling plays diverse roles in cellular physiology, including attenuation control, mRNA surveillance and maintenance of genome integrity. While the existence of coupling is broadly accepted, its mechanism and ubiquity are debated. Structural evidence supports mutually exclusive modes of RNA polymerase-ribosome contacts. In a model based on nuclear magnetic resonance data, NusG binds to a ribosomal protein S10 and acts as an adapter between RNA polymerase and the 30S subunit. Recent single-particle cryo electron microscopy analyses of RNA polymerase bound to 30S and 70S ribosomes revealed extensive, and very distinct, contacts which are incompatible with bridging by NusG. Saxena et al. provide the first evidence for NusG-mediated coupling in vivo. Their results demonstrate that Escherichia coli NusG interacts with the 70S ribosomes through a previously established interface and that these interactions are required for survival when translation elongation is hindered to weaken coupling. Future studies will address a likely possibility that distinct bridging mechanisms underpin context-dependent coupling in the cell.
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Affiliation(s)
- Irina Artsimovitch
- Department of Microbiology, The Center for RNA Biology, The Ohio State University, Columbus, Ohio, 43210, USA
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63
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Identification and functional characterization of bacterial small non-coding RNAs and their target: A review. GENE REPORTS 2018. [DOI: 10.1016/j.genrep.2018.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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64
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The impact of ribosomal interference, codon usage, and exit tunnel interactions on translation elongation rate variation. PLoS Genet 2018; 14:e1007166. [PMID: 29337993 PMCID: PMC5786338 DOI: 10.1371/journal.pgen.1007166] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 01/26/2018] [Accepted: 12/25/2017] [Indexed: 11/19/2022] Open
Abstract
Previous studies have shown that translation elongation is regulated by multiple factors, but the observed heterogeneity remains only partially explained. To dissect quantitatively the different determinants of elongation speed, we use probabilistic modeling to estimate initiation and local elongation rates from ribosome profiling data. This model-based approach allows us to quantify the extent of interference between ribosomes on the same transcript. We show that neither interference nor the distribution of slow codons is sufficient to explain the observed heterogeneity. Instead, we find that electrostatic interactions between the ribosomal exit tunnel and specific parts of the nascent polypeptide govern the elongation rate variation as the polypeptide makes its initial pass through the tunnel. Once the N-terminus has escaped the tunnel, the hydropathy of the nascent polypeptide within the ribosome plays a major role in modulating the speed. We show that our results are consistent with the biophysical properties of the tunnel.
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65
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Abstract
Bacteria produce different amounts of their proteins in response to different conditions. The ability to accurately quantitate the rates of protein synthesis across the genome is an important step toward understanding both underlying regulation and bacterial physiology at a systems level. Ribosome profiling (deep sequencing of ribosome-protected mRNA fragments) enables accurate and high-throughput measurement of such synthesis rates. Ribosomes protect RNAs from nuclease digestion; thus, by collecting and sequencing protected footprints, one can obtain information on the position of every ribosome at the time of cell collection. Assuming ribosomes go on to translate full-length proteins, the density of ribosomes across an ORF can be used to determine protein synthesis rates. Here we outline a step-by-step protocol and discuss the steps where variability and bias may be introduced, including ways to minimize it.
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Affiliation(s)
- Grace E Johnson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States
| | - Gene-Wei Li
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States.
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66
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Buskirk AR, Green R. Ribosome pausing, arrest and rescue in bacteria and eukaryotes. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0183. [PMID: 28138069 DOI: 10.1098/rstb.2016.0183] [Citation(s) in RCA: 115] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 12/17/2022] Open
Abstract
Ribosomes translate genetic information into polypeptides in several basic steps: initiation, elongation, termination and recycling. When ribosomes are arrested during elongation or termination, the cell's capacity for protein synthesis is reduced. There are numerous quality control systems in place to distinguish between paused ribosomes that need some extra input to proceed and terminally stalled ribosomes that need to be rescued. Here, we discuss similarities and differences in the systems for resolution of pauses and rescue of arrested ribosomes in bacteria and eukaryotes, and how ribosome profiling has transformed our ability to decipher these molecular events.This article is part of the themed issue 'Perspectives on the ribosome'.
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Affiliation(s)
- Allen R Buskirk
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Howard Hughes Medical Institute, Baltimore, MD, USA
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Howard Hughes Medical Institute, Baltimore, MD, USA
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67
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Donovan J, Rath S, Kolet-Mandrikov D, Korennykh A. Rapid RNase L-driven arrest of protein synthesis in the dsRNA response without degradation of translation machinery. RNA (NEW YORK, N.Y.) 2017; 23:1660-1671. [PMID: 28808124 PMCID: PMC5648034 DOI: 10.1261/rna.062000.117] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 08/06/2017] [Indexed: 05/20/2023]
Abstract
Mammalian cells respond to double-stranded RNA (dsRNA) by activating a translation-inhibiting endoribonuclease, RNase L. Consensus in the field indicates that RNase L arrests protein synthesis by degrading ribosomal RNAs (rRNAs) and messenger RNAs (mRNAs). However, here we provide evidence for a different and far more efficient mechanism. By sequencing abundant RNA fragments generated by RNase L in human cells, we identify site-specific cleavage of two groups of noncoding RNAs: Y-RNAs, whose function is poorly understood, and cytosolic tRNAs, which are essential for translation. Quantitative analysis of human RNA cleavage versus nascent protein synthesis in lung carcinoma cells shows that RNase L stops global translation when tRNAs, as well as rRNAs and mRNAs, are still intact. Therefore, RNase L does not have to degrade the translation machinery to stop protein synthesis. Our data point to a rapid mechanism that transforms a subtle RNA cleavage into a cell-wide translation arrest.
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Affiliation(s)
- Jesse Donovan
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Sneha Rath
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - David Kolet-Mandrikov
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
| | - Alexei Korennykh
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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68
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Simms CL, Yan LL, Zaher HS. Ribosome Collision Is Critical for Quality Control during No-Go Decay. Mol Cell 2017; 68:361-373.e5. [PMID: 28943311 DOI: 10.1016/j.molcel.2017.08.019] [Citation(s) in RCA: 186] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 05/08/2017] [Accepted: 08/21/2017] [Indexed: 10/18/2022]
Abstract
No-go decay (NGD) is a eukaryotic quality control mechanism that evolved to cope with translational arrests. The process is characterized by an endonucleolytic cleavage near the stall sequence, but the mechanistic details are unclear. Our analysis of cleavage sites indicates that cleavage requires multiple ribosomes on the mRNA. We also show that reporters harboring stall sequences near the initiation codon, which cannot accommodate multiple ribosomes, are not subject to NGD. Consistent with our model, we uncover an inverse correlation between ribosome density per mRNA and cleavage efficiency. Furthermore, promoting global ribosome collision in vivo resulted in ubiquitination of ribosomal proteins, suggesting that collision is sensed by the cell to initiate downstream quality control processes. Collectively, our data suggest that NGD and subsequent quality control are triggered by ribosome collision. This model provides insight into the regulation of quality control processes and the manner by which they reduce off-target effects.
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Affiliation(s)
- Carrie L Simms
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Liewei L Yan
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Hani S Zaher
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
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69
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Faure G, Ogurtsov AY, Shabalina SA, Koonin EV. Adaptation of mRNA structure to control protein folding. RNA Biol 2017; 14:1649-1654. [PMID: 28722509 DOI: 10.1080/15476286.2017.1349047] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
Comparison of mRNA and protein structures shows that highly structured mRNAs typically encode compact protein domains suggesting that mRNA structure controls protein folding. This function is apparently performed by distinct structural elements in the mRNA, which implies 'fine tuning' of mRNA structure under selection for optimal protein folding. We find that, during evolution, changes in the mRNA folding energy follow amino acid replacements, reinforcing the notion of an intimate connection between the structures of a mRNA and the protein it encodes, and the double encoding of protein sequence and folding in the mRNA.
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Affiliation(s)
- Guilhem Faure
- a National Center for Biotechnology Information, National Library of Medicine , National Institutes of Health , Bethesda , MD , USA
| | - Aleksey Y Ogurtsov
- a National Center for Biotechnology Information, National Library of Medicine , National Institutes of Health , Bethesda , MD , USA
| | - Svetlana A Shabalina
- a National Center for Biotechnology Information, National Library of Medicine , National Institutes of Health , Bethesda , MD , USA
| | - Eugene V Koonin
- a National Center for Biotechnology Information, National Library of Medicine , National Institutes of Health , Bethesda , MD , USA
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70
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Abstract
The ribosome flow model on a ring (RFMR) is a deterministic model for ribosome flow along a circularized mRNA. We derive a new spectral representation for the optimal steady-state production rate and the corresponding optimal steady-state ribosomal density in the RFMR. This representation has several important advantages. First, it provides a simple and numerically stable algorithm for determining the optimal values even in very long rings. Second, it enables efficient computation of the sensitivity of the optimal production rate to small changes in the transition rates along the mRNA. Third, it implies that the optimal steady-state production rate is a strictly concave function of the transition rates. Maximizing the optimal steady-state production rate with respect to the rates under an affine constraint on the rates thus becomes a convex optimization problem that admits a unique solution. This solution can be determined numerically using highly efficient algorithms. This optimization problem is important, for example, when re-engineering heterologous genes in a host organism. We describe the implications of our results to this and other aspects of translation.
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71
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Zarai Y, Margaliot M, Tuller T. A deterministic mathematical model for bidirectional excluded flow with Langmuir kinetics. PLoS One 2017; 12:e0182178. [PMID: 28832591 PMCID: PMC5568237 DOI: 10.1371/journal.pone.0182178] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/13/2017] [Indexed: 11/30/2022] Open
Abstract
In many important cellular processes, including mRNA translation, gene transcription, phosphotransfer, and intracellular transport, biological "particles" move along some kind of "tracks". The motion of these particles can be modeled as a one-dimensional movement along an ordered sequence of sites. The biological particles (e.g., ribosomes or RNAPs) have volume and cannot surpass one another. In some cases, there is a preferred direction of movement along the track, but in general the movement may be bidirectional, and furthermore the particles may attach or detach from various regions along the tracks. We derive a new deterministic mathematical model for such transport phenomena that may be interpreted as a dynamic mean-field approximation of an important model from mechanical statistics called the asymmetric simple exclusion process (ASEP) with Langmuir kinetics. Using tools from the theory of monotone dynamical systems and contraction theory we show that the model admits a unique steady-state, and that every solution converges to this steady-state. Furthermore, we show that the model entrains (or phase locks) to periodic excitations in any of its forward, backward, attachment, or detachment rates. We demonstrate an application of this phenomenological transport model for analyzing ribosome drop off in mRNA translation.
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Affiliation(s)
- Yoram Zarai
- Dept. of Biomedical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Michael Margaliot
- School of Electrical Engineering and the Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Tamir Tuller
- Dept. of Biomedical Engineering and the Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv 69978, Israel
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72
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Ferrin MA, Subramaniam AR. Kinetic modeling predicts a stimulatory role for ribosome collisions at elongation stall sites in bacteria. eLife 2017; 6. [PMID: 28498106 PMCID: PMC5446239 DOI: 10.7554/elife.23629] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Accepted: 05/10/2017] [Indexed: 02/01/2023] Open
Abstract
Ribosome stalling on mRNAs can decrease protein expression. To decipher ribosome kinetics at stall sites, we induced ribosome stalling at specific codons by starving the bacterium Escherichia coli for the cognate amino acid. We measured protein synthesis rates from a reporter library of over 100 variants that encoded systematic perturbations of translation initiation rate, the number of stall sites, and the distance between stall sites. Our measurements are quantitatively inconsistent with two widely-used kinetic models for stalled ribosomes: ribosome traffic jams that block initiation, and abortive (premature) termination of stalled ribosomes. Rather, our measurements support a model in which collision with a trailing ribosome causes abortive termination of the stalled ribosome. In our computational analysis, ribosome collisions selectively stimulate abortive termination without fine-tuning of kinetic rate parameters at ribosome stall sites. We propose that ribosome collisions serve as a robust timer for translational quality control pathways to recognize stalled ribosomes.
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Affiliation(s)
- Michael A Ferrin
- Basic Sciences Division and Computational Biology Program of Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, United States
| | - Arvind R Subramaniam
- Basic Sciences Division and Computational Biology Program of Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, United States
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73
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Bonnin P, Kern N, Young NT, Stansfield I, Romano MC. Novel mRNA-specific effects of ribosome drop-off on translation rate and polysome profile. PLoS Comput Biol 2017; 13:e1005555. [PMID: 28558053 PMCID: PMC5469512 DOI: 10.1371/journal.pcbi.1005555] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 06/13/2017] [Accepted: 05/08/2017] [Indexed: 11/19/2022] Open
Abstract
The well established phenomenon of ribosome drop-off plays crucial roles in translational accuracy and nutrient starvation responses during protein translation. When cells are under stress conditions, such as amino acid starvation or aminoacyl-tRNA depletion due to a high level of recombinant protein expression, ribosome drop-off can substantially affect the efficiency of protein expression. Here we introduce a mathematical model that describes the effects of ribosome drop-off on the ribosome density along the mRNA and on the concomitant protein synthesis rate. Our results show that ribosome premature termination may lead to non-intuitive ribosome density profiles, such as a ribosome density which increases from the 5' to the 3' end. Importantly, the model predicts that the effects of ribosome drop-off on the translation rate are mRNA-specific, and we quantify their resilience to drop-off, showing that the mRNAs which present ribosome queues are much less affected by ribosome drop-off than those which do not. Moreover, among those mRNAs that do not present ribosome queues, resilience to drop-off correlates positively with the elongation rate, so that sequences using fast codons are expected to be less affected by ribosome drop-off. This result is consistent with a genome-wide analysis of S. cerevisiae, which reveals that under favourable growth conditions mRNAs coding for proteins involved in the translation machinery, known to be highly codon biased and using preferentially fast codons, are highly resilient to ribosome drop-off. Moreover, in physiological conditions, the translation rate of mRNAs coding for regulatory, stress-related proteins, is less resilient to ribosome drop-off. This model therefore allows analysis of variations in the translational efficiency of individual mRNAs by accounting for the full range of known ribosome behaviours, as well as explaining mRNA-specific variations in ribosome density emerging from ribosome profiling studies.
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Affiliation(s)
- Pierre Bonnin
- Institute for Complex Systems and Mathematical Biology, Physics Department, University of Aberdeen, Aberdeen, UK
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK
| | - Norbert Kern
- Université Montpellier 2, Laboratoire Charles Coulomb UMR 5221, Montpellier, France
| | - Neil T. Young
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK
| | - Ian Stansfield
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK
| | - M. Carmen Romano
- Institute for Complex Systems and Mathematical Biology, Physics Department, University of Aberdeen, Aberdeen, UK
- Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, UK
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74
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Schuller AP, Wu CCC, Dever TE, Buskirk AR, Green R. eIF5A Functions Globally in Translation Elongation and Termination. Mol Cell 2017; 66:194-205.e5. [PMID: 28392174 PMCID: PMC5414311 DOI: 10.1016/j.molcel.2017.03.003] [Citation(s) in RCA: 279] [Impact Index Per Article: 39.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 02/10/2017] [Accepted: 03/03/2017] [Indexed: 12/11/2022]
Abstract
The eukaryotic translation factor eIF5A, originally identified as an initiation factor, was later shown to promote translation elongation of iterated proline sequences. Using a combination of ribosome profiling and in vitro biochemistry, we report a much broader role for eIF5A in elongation and uncover a critical function for eIF5A in termination. Ribosome profiling of an eIF5A-depleted strain reveals a global elongation defect, with abundant ribosomes stalling at many sequences, not limited to proline stretches. Our data also show ribosome accumulation at stop codons and in the 3' UTR, suggesting a global defect in termination in the absence of eIF5A. Using an in vitro reconstituted translation system, we find that eIF5A strongly promotes the translation of the stalling sequences identified by profiling and increases the rate of peptidyl-tRNA hydrolysis more than 17-fold. We conclude that eIF5A functions broadly in elongation and termination, rationalizing its high cellular abundance and essential nature.
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Affiliation(s)
- Anthony P Schuller
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Colin Chih-Chien Wu
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Thomas E Dever
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Allen R Buskirk
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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75
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When mRNA translation meets decay. Biochem Soc Trans 2017; 45:339-351. [DOI: 10.1042/bst20160243] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 12/19/2016] [Accepted: 01/11/2017] [Indexed: 12/26/2022]
Abstract
Messenger RNA (mRNA) translation and mRNA degradation are important determinants of protein output, and they are interconnected. Previously, it was thought that translation of an mRNA, as a rule, prevents its degradation. mRNA surveillance mechanisms, which degrade mRNAs as a consequence of their translation, were considered to be exceptions to this rule. Recently, however, it has become clear that many mRNAs are degraded co-translationally, and it has emerged that codon choice, by influencing the rate of ribosome elongation, affects the rate of mRNA decay. In this review, we discuss the links between translation and mRNA stability, with an emphasis on emerging data suggesting that codon optimality may regulate mRNA degradation.
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76
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Synonymous Codons: Choose Wisely for Expression. Trends Genet 2017; 33:283-297. [PMID: 28292534 DOI: 10.1016/j.tig.2017.02.001] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/16/2017] [Accepted: 02/17/2017] [Indexed: 11/22/2022]
Abstract
The genetic code, which defines the amino acid sequence of a protein, also contains information that influences the rate and efficiency of translation. Neither the mechanisms nor functions of codon-mediated regulation were well understood. The prevailing model was that the slow translation of codons decoded by rare tRNAs reduces efficiency. Recent genome-wide analyses have clarified several issues. Specific codons and codon combinations modulate ribosome speed and facilitate protein folding. However, tRNA availability is not the sole determinant of rate; rather, interactions between adjacent codons and wobble base pairing are key. One mechanism linking translation efficiency and codon use is that slower decoding is coupled to reduced mRNA stability. Changes in tRNA supply mediate biological regulationfor instance,, changes in tRNA amounts facilitate cancer metastasis.
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77
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Dai X, Zhu M, Warren M, Balakrishnan R, Patsalo V, Okano H, Williamson JR, Fredrick K, Wang YP, Hwa T. Reduction of translating ribosomes enables Escherichia coli to maintain elongation rates during slow growth. Nat Microbiol 2016; 2:16231. [PMID: 27941827 PMCID: PMC5346290 DOI: 10.1038/nmicrobiol.2016.231] [Citation(s) in RCA: 175] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 10/17/2016] [Indexed: 01/13/2023]
Abstract
Bacteria growing under different conditions experience a broad range of demand on the rate of protein synthesis, which profoundly affects cellular resource allocation. During fast growth, protein synthesis has long been known to be modulated by adjusting the ribosome content, with the vast majority of ribosomes engaged at a near-maximal rate of elongation. Here, we systematically characterize protein synthesis by Escherichia coli, focusing on slow-growth conditions. We establish that the translational elongation rate decreases as growth slows, exhibiting a Michaelis-Menten dependence on the abundance of the cellular translational apparatus. However, an appreciable elongation rate is maintained even towards zero growth, including the stationary phase. This maintenance, critical for timely protein synthesis in harsh environments, is accompanied by a drastic reduction in the fraction of active ribosomes. Interestingly, well-known antibiotics such as chloramphenicol also cause a substantial reduction in the pool of active ribosomes, instead of slowing down translational elongation as commonly thought.
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Affiliation(s)
- Xiongfeng Dai
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Manlu Zhu
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Mya Warren
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
| | - Rohan Balakrishnan
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
- Department of Microbiology and Ohio State Biochemistry Program, the Ohio State University, Columbus OH 43210
| | - Vadim Patsalo
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Hiroyuki Okano
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
| | - James R. Williamson
- Department of Integrative Structural and Computational Biology, Department of Chemistry, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Kurt Fredrick
- Department of Microbiology and Ohio State Biochemistry Program, the Ohio State University, Columbus OH 43210
| | - Yi-Ping Wang
- State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871, China
| | - Terence Hwa
- Department of Physics, University of California at San Diego, La Jolla CA 92093-0374
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78
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Mechanistic insights into the alternative translation termination by ArfA and RF2. Nature 2016; 541:550-553. [PMID: 27906160 DOI: 10.1038/nature20822] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2016] [Accepted: 11/25/2016] [Indexed: 01/07/2023]
Abstract
During cellular translation of messenger RNAs by ribosomes, the translation apparatus sometimes pauses or stalls at the elongation and termination steps. With the exception of programmed stalling, which is usually used by cells for regulatory purposes, ribosomes stalled on mRNAs need to be terminated and recycled to maintain adequate translation capacity. Much ribosome stalling originates in aberrant mRNAs that lack a stop codon. Transcriptional errors, misprocessing of primary transcripts, and undesired mRNA cleavage all contribute to the formation of non-stop mRNAs. Ribosomes stalled at the 3' end of non-stop mRNAs do not undergo normal termination owing to the lack of specific stop-codon recognition by canonical peptide release factors at the A-site decoding centre. In bacteria, the transfer-messenger RNA (tmRNA)-SmpB-mediated trans-translation rescue system reroutes stalled ribosomes to the normal elongation cycle and translation termination. Two additional rescue systems, ArfA-RF2 (refs 13, 14, 15, 16) and ArfB (formerly known as YaeJ), are also present in many bacterial species, but their mechanisms are not fully understood. Here, using cryo-electron microscopy, we characterize the structure of the Escherichia coli 70S ribosome bound with ArfA, the release factor RF2, a short non-stop mRNA and a cognate P-site tRNA. The C-terminal loop of ArfA occupies the mRNA entry channel on the 30S subunit, whereas its N terminus is sandwiched between the decoding centre and the switch loop of RF2, leading to marked conformational changes in both the decoding centre and RF2. Despite the distinct conformation of RF2, its conserved catalytic GGQ motif is precisely positioned next to the CCA-end of the P-site tRNA. These data illustrate a stop-codon surrogate mechanism for ArfA in facilitating the termination of non-stop ribosomal complexes by RF2.
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79
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Zarai Y, Margaliot M, Tuller T. On the Ribosomal Density that Maximizes Protein Translation Rate. PLoS One 2016; 11:e0166481. [PMID: 27861564 PMCID: PMC5115748 DOI: 10.1371/journal.pone.0166481] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 10/28/2016] [Indexed: 12/28/2022] Open
Abstract
During mRNA translation, several ribosomes attach to the same mRNA molecule simultaneously translating it into a protein. This pipelining increases the protein translation rate. A natural and important question is what ribosomal density maximizes the protein translation rate. Using mathematical models of ribosome flow along both a linear and a circular mRNA molecules we prove that typically the steady-state protein translation rate is maximized when the ribosomal density is one half of the maximal possible density. We discuss the implications of our results to endogenous genes under natural cellular conditions and also to synthetic biology.
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Affiliation(s)
- Yoram Zarai
- School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Michael Margaliot
- School of Electrical Engineering and the Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv 69978, Israel
| | - Tamir Tuller
- Dept. of Biomedical Engineering and the Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv 69978, Israel
- * E-mail:
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80
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Bergkessel M, Basta DW, Newman DK. The physiology of growth arrest: uniting molecular and environmental microbiology. Nat Rev Microbiol 2016; 14:549-62. [PMID: 27510862 PMCID: PMC10069271 DOI: 10.1038/nrmicro.2016.107] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Most bacteria spend the majority of their time in prolonged states of very low metabolic activity and little or no growth, in which electron donors, electron acceptors and/or nutrients are limited, but cells are poised to undergo rapid division cycles when resources become available. These non-growing states are far less studied than other growth states, which leaves many questions regarding basic bacterial physiology unanswered. In this Review, we discuss findings from a small but diverse set of systems that have been used to investigate how growth-arrested bacteria adjust metabolism, regulate transcription and translation, and maintain their chromosomes. We highlight major questions that remain to be addressed, and suggest that progress in answering them will be aided by recent methodological advances and by dialectic between environmental and molecular microbiology perspectives.
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81
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Avcilar-Kucukgoze I, Bartholomäus A, Cordero Varela JA, Kaml RFX, Neubauer P, Budisa N, Ignatova Z. Discharging tRNAs: a tug of war between translation and detoxification in Escherichia coli. Nucleic Acids Res 2016; 44:8324-34. [PMID: 27507888 PMCID: PMC5041488 DOI: 10.1093/nar/gkw697] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 07/28/2016] [Indexed: 01/13/2023] Open
Abstract
Translation is a central cellular process and is optimized for speed and fidelity. The speed of translation of a single codon depends on the concentration of aminoacyl-tRNAs. Here, we used microarray-based approaches to analyze the charging levels of tRNAs in Escherichia coli growing at different growth rates. Strikingly, we observed a non-uniform aminoacylation of tRNAs in complex media. In contrast, in minimal medium, the level of aminoacyl-tRNAs is more uniform and rises to approximately 60%. Particularly, the charging level of tRNA(Ser), tRNA(Cys), tRNA(Thr) and tRNA(His) is below 50% in complex medium and their aminoacylation levels mirror the degree that amino acids inhibit growth when individually added to minimal medium. Serine is among the most toxic amino acids for bacteria and tRNAs(Ser) exhibit the lowest charging levels, below 10%, at high growth rate although intracellular serine concentration is plentiful. As a result some serine codons are among the most slowly translated codons. A large fraction of the serine is most likely degraded by L-serine-deaminase, which competes with the seryl-tRNA-synthetase that charges the tRNAs(Ser) These results indicate that the level of aminoacylation in complex media might be a competition between charging for translation and degradation of amino acids that inhibit growth.
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Affiliation(s)
- Irem Avcilar-Kucukgoze
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14467 Potsdam, Germany
| | - Alexander Bartholomäus
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14467 Potsdam, Germany Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
| | - Juan A Cordero Varela
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14467 Potsdam, Germany
| | | | - Peter Neubauer
- Bioprocess Engineering, Technical University Berlin, Ackerstr. 76, 13355 Berlin, Germany
| | - Nediljko Budisa
- Biocatalysis, Technical University Berlin, Müller-Breslau-Str. 10, 10623 Berlin, Germany
| | - Zoya Ignatova
- Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14467 Potsdam, Germany Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Pl. 6, 20146 Hamburg, Germany
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82
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Gamble CE, Brule CE, Dean KM, Fields S, Grayhack EJ. Adjacent Codons Act in Concert to Modulate Translation Efficiency in Yeast. Cell 2016; 166:679-690. [PMID: 27374328 PMCID: PMC4967012 DOI: 10.1016/j.cell.2016.05.070] [Citation(s) in RCA: 145] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Revised: 04/14/2016] [Accepted: 05/19/2016] [Indexed: 12/18/2022]
Abstract
Translation elongation efficiency is largely thought of as the sum of decoding efficiencies for individual codons. Here, we find that adjacent codon pairs modulate translation efficiency. Deploying an approach in Saccharomyces cerevisiae that scored the expression of over 35,000 GFP variants in which three adjacent codons were randomized, we have identified 17 pairs of adjacent codons associated with reduced expression. For many pairs, codon order is obligatory for inhibition, implying a more complex interaction than a simple additive effect. Inhibition mediated by adjacent codons occurs during translation itself as GFP expression is restored by increased tRNA levels or by non-native tRNAs with exact-matching anticodons. Inhibition operates in endogenous genes, based on analysis of ribosome profiling data. Our findings suggest translation efficiency is modulated by an interplay between tRNAs at adjacent sites in the ribosome and that this concerted effect needs to be considered in predicting the functional consequences of codon choice.
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Affiliation(s)
- Caitlin E Gamble
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, WA 98195, USA; Program in Molecular and Cellular Biology, University of Washington, Seattle, WA 98195, USA
| | - Christina E Brule
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA
| | - Kimberly M Dean
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA
| | - Stanley Fields
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
| | - Elizabeth J Grayhack
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642, USA; Center for RNA Biology, University of Rochester, Rochester, NY 14642, USA.
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83
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Katz A, Elgamal S, Rajkovic A, Ibba M. Non-canonical roles of tRNAs and tRNA mimics in bacterial cell biology. Mol Microbiol 2016; 101:545-58. [PMID: 27169680 DOI: 10.1111/mmi.13419] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/09/2016] [Indexed: 12/27/2022]
Abstract
Transfer RNAs (tRNAs) are the macromolecules that transfer activated amino acids from aminoacyl-tRNA synthetases to the ribosome, where they are used for the mRNA guided synthesis of proteins. Transfer RNAs are ancient molecules, perhaps even predating the existence of the translation machinery. Albeit old, these molecules are tremendously conserved, a characteristic that is well illustrated by the fact that some bacterial tRNAs are efficient and specific substrates of eukaryotic aminoacyl-tRNA synthetases and ribosomes. Considering their ancient origin and high structural conservation, it is not surprising that tRNAs have been hijacked during evolution for functions outside of translation. These roles beyond translation include synthetic, regulatory and information functions within the cell. Here we provide an overview of the non-canonical roles of tRNAs and their mimics in bacteria, and discuss some of the common themes that arise when comparing these different functions.
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Affiliation(s)
- Assaf Katz
- Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
| | - Sara Elgamal
- Department of Microbiology and The Center for RNA Biology, Ohio State University, Columbus, Ohio, 43210, USA
| | - Andrei Rajkovic
- Department of Microbiology and The Center for RNA Biology, Ohio State University, Columbus, Ohio, 43210, USA
| | - Michael Ibba
- Department of Microbiology and The Center for RNA Biology, Ohio State University, Columbus, Ohio, 43210, USA
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84
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Induction of a stable sigma factor SigR by translation-inhibiting antibiotics confers resistance to antibiotics. Sci Rep 2016; 6:28628. [PMID: 27346454 PMCID: PMC4921905 DOI: 10.1038/srep28628] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 06/06/2016] [Indexed: 12/22/2022] Open
Abstract
Antibiotic-producing streptomycetes are rich sources of resistance mechanisms against endogenous and exogenous antibiotics. An ECF sigma factor σR (SigR) is known to govern the thiol-oxidative stress response in Streptomyces coelicolor. Amplification of this response is achieved by producing an unstable isoform of σR called σR′. In this work, we present evidence that antibiotics induce the SigR regulon via a redox-independent pathway, leading to antibiotic resistance. The translation-inhibiting antibiotics enhanced the synthesis of stable σR, eliciting a prolonged response. WblC/WhiB7, a WhiB-like DNA-binding protein, is responsible for inducing sigRp1 transcripts encoding the stable σR. The amount of WblC protein and its binding to the sigRp1 promoter in vivo increased upon antibiotic treatment. A similar phenomenon appears to exist in Mycobacterium tuberculosis as well. These findings reveal a novel antibiotic-induced resistance mechanism conserved among actinomycetes, and also give an explicit example of overlap in cellular damage and defense mechanisms between thiol-oxidative and anti- translational stresses.
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85
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Rodnina MV. The ribosome in action: Tuning of translational efficiency and protein folding. Protein Sci 2016; 25:1390-406. [PMID: 27198711 DOI: 10.1002/pro.2950] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Revised: 05/17/2016] [Accepted: 05/18/2016] [Indexed: 12/28/2022]
Abstract
The cellular proteome is shaped by the combined activities of the gene expression and quality control machineries. While transcription plays an undoubtedly important role, in recent years also translation emerged as a key step that defines the composition and quality of the proteome and the functional activity of proteins in the cell. Among the different post-transcriptional control mechanisms, translation initiation and elongation provide multiple checkpoints that can affect translational efficiency. A multitude of specific signals in mRNAs can determine the frequency of translation initiation, choice of the open reading frame, global and local elongation velocities, and the folding of the emerging protein. In addition to specific signatures in the mRNAs, also variations in the global pools of translation components, including ribosomes, tRNAs, mRNAs, and translation factors can alter translational efficiencies. The cellular outcomes of phenomena such as mRNA codon bias are sometimes difficult to understand due to the staggering complexity of covariates that affect codon usage, translation, and protein folding. Here we summarize the experimental evidence on how the ribosome-together with the other components of the translational machinery-can alter translational efficiencies of mRNA at the initiation and elongation stages and how translation velocity affects protein folding. We seek to explain these findings in the context of mechanistic work on the ribosome. The results argue in favour of a new understanding of translation control as a hub that links mRNA homeostasis to production and quality control of proteins in the cell.
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Affiliation(s)
- Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, 37077, Germany
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86
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Jacobson GN, Clark PL. Quality over quantity: optimizing co-translational protein folding with non-'optimal' synonymous codons. Curr Opin Struct Biol 2016; 38:102-10. [PMID: 27318814 PMCID: PMC5010456 DOI: 10.1016/j.sbi.2016.06.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 05/31/2016] [Accepted: 06/01/2016] [Indexed: 12/28/2022]
Abstract
Protein folding occurs on a time scale similar to peptide bond formation by the ribosome, which has long sparked speculation that altering translation rate could alter the folding mechanism or even the final folded structure of a protein in vivo. Recent results have provided strong support for this model: synonymous substitutions to codons with different usage frequency, which are often translated at different rates, have been shown to significantly alter the co-translational folding mechanism of some proteins, leading to altered cell function. Here we review recent progress towards understanding the connections between synonymous codon usage, translation rate and co-translational protein folding mechanisms.
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Affiliation(s)
- Giselle N Jacobson
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Patricia L Clark
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA; Department of Chemical & Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
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87
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Radhakrishnan A, Green R. Connections Underlying Translation and mRNA Stability. J Mol Biol 2016; 428:3558-64. [PMID: 27261255 DOI: 10.1016/j.jmb.2016.05.025] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 05/03/2016] [Accepted: 05/18/2016] [Indexed: 10/21/2022]
Abstract
Gene expression and regulation in organisms minimally depends on transcription by RNA polymerase and on the stability of the RNA product (for both coding and non-coding RNAs). For coding RNAs, gene expression is further influenced by the amount of translation by the ribosome and by the stability of the protein product. The stabilities of these two classes of RNA, non-coding and coding, vary considerably: tRNAs and rRNAs tend to be long lived while mRNAs tend to be more short lived. Even among mRNAs, however, there is a considerable range in stability (ranging from seconds to hours in bacteria and up to days in metazoans), suggesting a significant role for stability in the regulation of gene expression. Here, we review recent experiments from bacteria, yeast and metazoans indicating that the stability of most mRNAs is broadly impacted by the actions of ribosomes that translate them. Ribosomal recognition of defective mRNAs triggers "mRNA surveillance" pathways that target the mRNA for degradation [Shoemaker and Green (2012) ]. More generally, even the stability of perfectly functional mRNAs appears to be dictated by overall rates of translation by the ribosome [Herrick et al. (1990), Presnyak et al. (2015) ]. Given that mRNAs are synthesized for the purpose of being translated into proteins, it is reassuring that such intimate connections between mRNA and the ribosome can drive biological regulation. In closing, we consider the likelihood that these connections between protein synthesis and mRNA stability are widespread or whether other modes of regulation dominate the mRNA stability landscape in higher organisms.
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Affiliation(s)
- Aditya Radhakrishnan
- Program in Molecular Biophysics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins School of Medicine, Department of Molecular Biology and Genetics, Baltimore, MD 21205, USA
| | - Rachel Green
- Howard Hughes Medical Institute, Johns Hopkins School of Medicine, Department of Molecular Biology and Genetics, Baltimore, MD 21205, USA.
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88
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Veshaguri S, Christensen SM, Kemmer GC, Ghale G, Møller MP, Lohr C, Christensen AL, Justesen BH, Jørgensen IL, Schiller J, Hatzakis NS, Grabe M, Pomorski TG, Stamou D. Direct observation of proton pumping by a eukaryotic P-type ATPase. Science 2016; 351:1469-73. [PMID: 27013734 DOI: 10.1126/science.aad6429] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 02/23/2016] [Indexed: 12/12/2022]
Abstract
In eukaryotes, P-type adenosine triphosphatases (ATPases) generate the plasma membrane potential and drive secondary transport systems; however, despite their importance, their regulation remains poorly understood. We monitored at the single-molecule level the activity of the prototypic proton-pumping P-type ATPase Arabidopsis thaliana isoform 2 (AHA2). Our measurements, combined with a physical nonequilibrium model of vesicle acidification, revealed that pumping is stochastically interrupted by long-lived (~100 seconds) inactive or leaky states. Allosteric regulation by pH gradients modulated the switch between these states but not the pumping or leakage rates. The autoinhibitory regulatory domain of AHA2 reduced the intrinsic pumping rates but increased the dwell time in the active pumping state. We anticipate that similar functional dynamics underlie the operation and regulation of many other active transporters.
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Affiliation(s)
- Salome Veshaguri
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Sune M Christensen
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Gerdi C Kemmer
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Garima Ghale
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Mads P Møller
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Christina Lohr
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Andreas L Christensen
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Bo H Justesen
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Ida L Jørgensen
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Jürgen Schiller
- Institute of Medical Physics and Biophysics, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Nikos S Hatzakis
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Thomas Günther Pomorski
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Dimitrios Stamou
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
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89
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Sin C, Chiarugi D, Valleriani A. Quantitative assessment of ribosome drop-off in E. coli. Nucleic Acids Res 2016; 44:2528-37. [PMID: 26935582 PMCID: PMC4824120 DOI: 10.1093/nar/gkw137] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 02/24/2016] [Indexed: 11/14/2022] Open
Abstract
Premature ribosome drop-off is one of the major errors in translation of mRNA by ribosomes. However, repeated analyses of Ribo-seq data failed to quantify its strength inE. coli Relying on a novel highly sensitive data analysis method we show that a significant rate of ribosome drop-off is measurable and can be quantified also when cells are cultured under non-stressing conditions. Moreover, we find that the drop-off rate is highly variable, depending on multiple factors. In particular, under environmental stress such as amino acid starvation or ethanol intoxication, the drop-off rate markedly increases.
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Affiliation(s)
- Celine Sin
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14476 Potsdam, Germany
| | - Davide Chiarugi
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14476 Potsdam, Germany
| | - Angelo Valleriani
- Department of Theory and Bio-Systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14476 Potsdam, Germany
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90
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Kuwahara H, Arold ST, Gao X. Beyond initiation-limited translational bursting: the effects of burst size distributions on the stability of gene expression. Integr Biol (Camb) 2015; 7:1622-32. [DOI: 10.1039/c5ib00107b] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Hiroyuki Kuwahara
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
- Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
| | - Stefan T. Arold
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
- Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
| | - Xin Gao
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
- Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955, Saudi Arabia
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91
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Ferguson A, Wang L, Altman RB, Terry DS, Juette MF, Burnett BJ, Alejo JL, Dass RA, Parks MM, Vincent CT, Blanchard SC. Functional Dynamics within the Human Ribosome Regulate the Rate of Active Protein Synthesis. Mol Cell 2015; 60:475-86. [PMID: 26593721 PMCID: PMC4660248 DOI: 10.1016/j.molcel.2015.09.013] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 07/24/2015] [Accepted: 09/16/2015] [Indexed: 01/09/2023]
Abstract
The regulation of protein synthesis contributes to gene expression in both normal physiology and disease, yet kinetic investigations of the human translation mechanism are currently lacking. Using single-molecule fluorescence imaging methods, we have quantified the nature and timing of structural processes in human ribosomes during single-turnover and processive translation reactions. These measurements reveal that functional complexes exhibit dynamic behaviors and thermodynamic stabilities distinct from those observed for bacterial systems. Structurally defined sub-states of pre- and post-translocation complexes were sensitive to specific inhibitors of the eukaryotic ribosome, demonstrating the utility of this platform to probe drug mechanism. The application of three-color single-molecule fluorescence resonance energy transfer (smFRET) methods further revealed a long-distance allosteric coupling between distal tRNA binding sites within ribosomes bearing three tRNAs, which contributed to the rate of processive translation.
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Affiliation(s)
- Angelica Ferguson
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA; Tri-Institutional Training Program in Chemical Biology, Weill Cornell Medical College, Rockefeller University, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA
| | - Leyi Wang
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Roger B Altman
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Daniel S Terry
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Manuel F Juette
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Benjamin J Burnett
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Jose L Alejo
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Randall A Dass
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - Matthew M Parks
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA
| | - C Theresa Vincent
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA; Department of Pharmacology and Physiology, Karolinska Institute, 171 77 Stockholm, Sweden
| | - Scott C Blanchard
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA; Tri-Institutional Training Program in Chemical Biology, Weill Cornell Medical College, Rockefeller University, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
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92
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Koutmou KS, Radhakrishnan A, Green R. Synthesis at the Speed of Codons. Trends Biochem Sci 2015; 40:717-718. [PMID: 26526516 DOI: 10.1016/j.tibs.2015.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 10/15/2015] [Accepted: 10/16/2015] [Indexed: 10/22/2022]
Abstract
The possibility that different mRNA sequences encoding identical peptides are translated dissimilarly has long been of great interest. Recent work by Yu and co-workers provides striking evidence that mRNA sequences influence the rate of protein synthesis, and lends support to the emerging idea that mRNA sequence informs protein folding.
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Affiliation(s)
- Kristin S Koutmou
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Aditya Radhakrishnan
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Rachel Green
- Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, Baltimore, MD, USA.
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93
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Ribosome profiling reveals the what, when, where and how of protein synthesis. Nat Rev Mol Cell Biol 2015; 16:651-64. [PMID: 26465719 DOI: 10.1038/nrm4069] [Citation(s) in RCA: 309] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Ribosome profiling, which involves the deep sequencing of ribosome-protected mRNA fragments, is a powerful tool for globally monitoring translation in vivo. The method has facilitated discovery of the regulation of gene expression underlying diverse and complex biological processes, of important aspects of the mechanism of protein synthesis, and even of new proteins, by providing a systematic approach for experimental annotation of coding regions. Here, we introduce the methodology of ribosome profiling and discuss examples in which this approach has been a key factor in guiding biological discovery, including its prominent role in identifying thousands of novel translated short open reading frames and alternative translation products.
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94
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Zhang Y, Mandava CS, Cao W, Li X, Zhang D, Li N, Zhang Y, Zhang X, Qin Y, Mi K, Lei J, Sanyal S, Gao N. HflX is a ribosome-splitting factor rescuing stalled ribosomes under stress conditions. Nat Struct Mol Biol 2015; 22:906-13. [PMID: 26458047 DOI: 10.1038/nsmb.3103] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 09/04/2015] [Indexed: 12/16/2022]
Abstract
Adverse cellular conditions often lead to nonproductive translational stalling and arrest of ribosomes on mRNAs. Here, we used fast kinetics and cryo-EM to characterize Escherichia coli HflX, a GTPase with unknown function. Our data reveal that HflX is a heat shock-induced ribosome-splitting factor capable of dissociating vacant as well as mRNA-associated ribosomes with deacylated tRNA in the peptidyl site. Structural data demonstrate that the N-terminal effector domain of HflX binds to the peptidyl transferase center in a strikingly similar manner as that of the class I release factors and induces dramatic conformational changes in central intersubunit bridges, thus promoting subunit dissociation. Accordingly, loss of HflX results in an increase in stalled ribosomes upon heat shock. These results suggest a primary role of HflX in rescuing translationally arrested ribosomes under stress conditions.
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Affiliation(s)
- Yanqing Zhang
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | | | - Wei Cao
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Xiaojing Li
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Dejiu Zhang
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Ningning Li
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yixiao Zhang
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Xiaoxiao Zhang
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yan Qin
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Kaixia Mi
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Jianlin Lei
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Suparna Sanyal
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Ning Gao
- Ministry of Education Key Laboratory of Protein Sciences, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
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95
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Cary GA, Vinh DBN, May P, Kuestner R, Dudley AM. Proteomic Analysis of Dhh1 Complexes Reveals a Role for Hsp40 Chaperone Ydj1 in Yeast P-Body Assembly. G3 (BETHESDA, MD.) 2015; 5:2497-511. [PMID: 26392412 PMCID: PMC4632068 DOI: 10.1534/g3.115.021444] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 09/16/2015] [Indexed: 12/18/2022]
Abstract
P-bodies (PB) are ribonucleoprotein (RNP) complexes that aggregate into cytoplasmic foci when cells are exposed to stress. Although the conserved mRNA decay and translational repression machineries are known components of PB, how and why cells assemble RNP complexes into large foci remain unclear. Using mass spectrometry to analyze proteins immunoisolated with the core PB protein Dhh1, we show that a considerable number of proteins contain low-complexity sequences, similar to proteins highly represented in mammalian RNP granules. We also show that the Hsp40 chaperone Ydj1, which contains an low-complexity domain and controls prion protein aggregation, is required for the formation of Dhh1-GFP foci on glucose depletion. New classes of proteins that reproducibly coenrich with Dhh1-GFP during PB induction include proteins involved in nucleotide or amino acid metabolism, glycolysis, transfer RNA aminoacylation, and protein folding. Many of these proteins have been shown to form foci in response to other stresses. Finally, analysis of RNA associated with Dhh1-GFP shows enrichment of mRNA encoding the PB protein Pat1 and catalytic RNAs along with their associated mitochondrial RNA-binding proteins. Thus, global characterization of PB composition has uncovered proteins important for PB assembly and evidence suggesting an active role for RNA in PB function.
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Affiliation(s)
- Gregory A Cary
- Institute for Systems Biology, Seattle, Washington 98109 Molecular and Cellular Biology Program, University of Washington, Seattle, Washington 98195
| | - Dani B N Vinh
- Institute for Systems Biology, Seattle, Washington 98109
| | - Patrick May
- Institute for Systems Biology, Seattle, Washington 98109 Luxembourg Centre for Systems Biomedicine, Université du Luxembourg, Esch-sur-Alzette, Luxembourg L-4362
| | - Rolf Kuestner
- Institute for Systems Biology, Seattle, Washington 98109
| | - Aimée M Dudley
- Molecular and Cellular Biology Program, University of Washington, Seattle, Washington 98195 Pacific Northwest Diabetes Research Institute, Seattle, Washington 98122
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96
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Ying BW, Honda T, Tsuru S, Seno S, Matsuda H, Kazuta Y, Yomo T. Evolutionary Consequence of a Trade-Off between Growth and Maintenance along with Ribosomal Damages. PLoS One 2015; 10:e0135639. [PMID: 26292224 PMCID: PMC4546238 DOI: 10.1371/journal.pone.0135639] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 07/24/2015] [Indexed: 12/15/2022] Open
Abstract
Microorganisms in nature are constantly subjected to a limited availability of resources and experience repeated starvation and nutrition. Therefore, microbial life may evolve for both growth fitness and sustainability. By contrast, experimental evolution, as a powerful approach to investigate microbial evolutionary strategies, often targets the increased growth fitness in controlled, steady-state conditions. Here, we address evolutionary changes balanced between growth and maintenance while taking nutritional fluctuations into account. We performed a 290-day-long evolution experiment with a histidine-requiring Escherichia coli strain that encountered repeated histidine-rich and histidine-starved conditions. The cells that experienced seven rounds of starvation and re-feed grew more sustainably under prolonged starvation but dramatically lost growth fitness under rich conditions. The improved sustainability arose from the evolved capability to use a trace amount of histidine for cell propagation. The reduced growth rate was attributed to mutations genetically disturbing the translation machinery, that is, the ribosome, ultimately slowing protein translation. This study provides the experimental demonstration of slow growth accompanied by an enhanced affinity to resources as an evolutionary adaptation to oscillated environments and verifies that it is possible to evolve for reduced growth fitness. Growth economics favored for population increase under extreme resource limitations is most likely a common survival strategy adopted by natural microbes.
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Affiliation(s)
- Bei-Wen Ying
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305–8572, Japan
| | - Tomoya Honda
- Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, California, 92093, United States of America
| | - Saburo Tsuru
- Graduate School of Information Science and Technology, Osaka University, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
| | - Shigeto Seno
- Graduate School of Information Science and Technology, Osaka University, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
| | - Hideo Matsuda
- Graduate School of Information Science and Technology, Osaka University, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
| | - Yasuaki Kazuta
- ERATO, JST, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
| | - Tetsuya Yomo
- Graduate School of Information Science and Technology, Osaka University, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
- ERATO, JST, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
- Graduate School of Frontier Biosciences, Osaka University, 1–5 Yamadaoka, Suita, Osaka, 565–0871, Japan
- * E-mail:
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97
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Abstract
In this issue of Cell, Pelechano et al. report that sequencing of mRNA decay intermediates shows surprisingly tight coupling of a major decay pathway to the movement of the last translating ribosome, revealing stress- and starvation-dependent modulation of translation elongation.
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Affiliation(s)
- Edward W J Wallace
- Department of Biochemistry & Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
| | - D Allan Drummond
- Department of Biochemistry & Molecular Biology, The University of Chicago, Chicago, IL 60637, USA.
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98
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Pelechano V, Wei W, Steinmetz LM. Widespread Co-translational RNA Decay Reveals Ribosome Dynamics. Cell 2015; 161:1400-12. [PMID: 26046441 DOI: 10.1016/j.cell.2015.05.008] [Citation(s) in RCA: 186] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Revised: 03/25/2015] [Accepted: 04/20/2015] [Indexed: 12/19/2022]
Abstract
It is generally assumed that mRNAs undergoing translation are protected from decay. Here, we show that mRNAs are, in fact, co-translationally degraded. This is a widespread and conserved process affecting most genes, where 5'-3' transcript degradation follows the last translating ribosome, producing an in vivo ribosomal footprint. By sequencing the ends of 5' phosphorylated mRNA degradation intermediates, we obtain a genome-wide drug-free measurement of ribosome dynamics. We identify general translation termination pauses in both normal and stress conditions. In addition, we describe novel codon-specific ribosomal pausing sites in response to oxidative stress that are dependent on the RNase Rny1. Our approach is simple and straightforward and does not require the use of translational inhibitors or in vitro RNA footprinting that can alter ribosome protection patterns.
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Affiliation(s)
- Vicent Pelechano
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, 69117 Heidelberg, Germany
| | - Wu Wei
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA 94304, USA; Department of Genetics, School of Medicine, Stanford University, Stanford, CA 94305, USA
| | - Lars M Steinmetz
- European Molecular Biology Laboratory (EMBL), Genome Biology Unit, 69117 Heidelberg, Germany; Stanford Genome Technology Center, Stanford University, Palo Alto, CA 94304, USA; Department of Genetics, School of Medicine, Stanford University, Stanford, CA 94305, USA.
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99
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Latif H, Szubin R, Tan J, Brunk E, Lechner A, Zengler K, Palsson BO. A streamlined ribosome profiling protocol for the characterization of microorganisms. Biotechniques 2015; 58:329-32. [PMID: 26054770 DOI: 10.2144/000114302] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 03/06/2015] [Indexed: 11/23/2022] Open
Abstract
Ribosome profiling is a powerful tool for characterizing in vivo protein translation at the genome scale, with multiple applications ranging from detailed molecular mechanisms to systems-level predictive modeling. Though highly effective, this intricate technique has yet to become widely used in the microbial research community. Here we present a streamlined ribosome profiling protocol with reduced barriers to entry for microbial characterization studies. Our approach provides simplified alternatives during harvest, lysis, and recovery of monosomes and also eliminates several time-consuming steps, in particular size-selection steps during library construction. Furthermore, the abundance of rRNAs and tRNAs in the final library is drastically reduced. Our streamlined workflow enables greater throughput, cuts the time from harvest to the final library in half (down to 3-4 days), and generates a high fraction of informative reads, all while retaining the high quality standards of the existing protocol.
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Affiliation(s)
- Haythem Latif
- Bioengineering Department, University of California, San Diego, La Jolla, CA
| | - Richard Szubin
- Bioengineering Department, University of California, San Diego, La Jolla, CA
| | - Justin Tan
- Bioengineering Department, University of California, San Diego, La Jolla, CA
| | - Elizabeth Brunk
- Fuels Synthesis Division, Joint BioEnergy Institute, Emeryville, CA.,Department of Chemical & Biomolecular Engineering, Department of Bioengineering, University of California, Berkeley, Berkeley, CA
| | - Anna Lechner
- QB3 Institute, University of California, Emeryville, CA
| | - Karsten Zengler
- Bioengineering Department, University of California, San Diego, La Jolla, CA.,Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark
| | - Bernhard O Palsson
- Bioengineering Department, University of California, San Diego, La Jolla, CA.,Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark
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Hess AK, Saffert P, Liebeton K, Ignatova Z. Optimization of translation profiles enhances protein expression and solubility. PLoS One 2015; 10:e0127039. [PMID: 25965266 PMCID: PMC4428881 DOI: 10.1371/journal.pone.0127039] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 04/11/2015] [Indexed: 12/12/2022] Open
Abstract
mRNA is translated with a non-uniform speed that actively coordinates co-translational folding of protein domains. Using structure-based homology we identified the structural domains in epoxide hydrolases (EHs) and introduced slow-translating codons to delineate the translation of single domains. These changes in translation speed dramatically improved the solubility of two EHs of metagenomic origin in Escherichia coli. Conversely, the importance of transient attenuation for the folding, and consequently solubility, of EH was evidenced with a member of the EH family from Agrobacterium radiobacter, which partitions in the soluble fraction when expressed in E. coli. Synonymous substitutions of codons shaping the slow-transiting regions to fast-translating codons render this protein insoluble. Furthermore, we show that low protein yield can be enhanced by decreasing the free folding energy of the initial 5’-coding region, which can disrupt mRNA secondary structure and enhance ribosomal loading. This study provides direct experimental evidence that mRNA is not a mere messenger for translation of codons into amino acids but bears an additional layer of information for folding, solubility and expression level of the encoded protein. Furthermore, it provides a general frame on how to modulate and fine-tune gene expression of a target protein.
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Affiliation(s)
- Anne-Katrin Hess
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Paul Saffert
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | | | - Zoya Ignatova
- Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
- Biochemistry, Department of Chemistry and Biochemistry, University of Hamburg, Hamburg, Germany
- * E-mail: (ZI); (KL)
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