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Rao Y, Ahmed N, Pritchard J, O'Brien EP. Incorporating mutational heterogeneity to identify genes that are enriched for synonymous mutations in cancer. BMC Bioinformatics 2023; 24:462. [PMID: 38062391 PMCID: PMC10704839 DOI: 10.1186/s12859-023-05521-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 10/05/2023] [Indexed: 12/18/2023] Open
Abstract
BACKGROUND Synonymous mutations, which change the DNA sequence but not the encoded protein sequence, can affect protein structure and function, mRNA maturation, and mRNA half-lives. The possibility that synonymous mutations might be enriched in cancer has been explored in several recent studies. However, none of these studies control for all three types of mutational heterogeneity (patient, histology, and gene) that are known to affect the accurate identification of non-synonymous cancer-associated genes. Our goal is to adopt the current standard for non-synonymous mutations in an investigation of synonymous mutations. RESULTS Here, we create an algorithm, MutSigCVsyn, an adaptation of MutSigCV, to identify cancer-associated genes that are enriched for synonymous mutations based on a non-coding background model that takes into account the mutational heterogeneity across these levels. Using MutSigCVsyn, we first analyzed 2572 cancer whole-genome samples from the Pan-cancer Analysis of Whole Genomes (PCAWG) to identify non-synonymous cancer drivers as a quality control. Indicative of the algorithm accuracy we find that 58.6% of these candidate genes were also found in Cancer Census Gene (CGC) list, and 66.2% were found within the PCAWG cancer driver list. We then applied it to identify 30 putative cancer-associated genes that are enriched for synonymous mutations within the same samples. One of the promising gene candidates is the B cell lymphoma 2 (BCL-2) gene. BCL-2 regulates apoptosis by antagonizing the action of proapoptotic BCL-2 family member proteins. The synonymous mutations in BCL2 are enriched in its anti-apoptotic domain and likely play a role in cancer cell proliferation. CONCLUSION Our study introduces MutSigCVsyn, an algorithm that accounts for mutational heterogeneity at patient, histology, and gene levels, to identify cancer-associated genes that are enriched for synonymous mutations using whole genome sequencing data. We identified 30 putative candidate genes that will benefit from future experimental studies on the role of synonymous mutations in cancer biology.
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Affiliation(s)
- Yiyun Rao
- Huck Institute of the Life Sciences, Pennsylvania State University, University Park, State College, PA, 16802, USA
| | - Nabeel Ahmed
- Huck Institute of the Life Sciences, Pennsylvania State University, University Park, State College, PA, 16802, USA
- Moderna, Inc., Cambridge, USA
| | - Justin Pritchard
- Department of Biomedical Engineering, Pennsylvania State University, University Park, State College, PA, 16802, USA.
| | - Edward P O'Brien
- Department of Chemistry, Pennsylvania State University, University Park, State College, PA, 16802, USA.
- Institute for Computational and Data Sciences, Pennsylvania State University, University Park, State College, PA, 16802, USA.
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2
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Davyt M, Bharti N, Ignatova Z. Effect of mRNA/tRNA mutations on translation speed: Implications for human diseases. J Biol Chem 2023; 299:105089. [PMID: 37495112 PMCID: PMC10470029 DOI: 10.1016/j.jbc.2023.105089] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 07/28/2023] Open
Abstract
Recent discoveries establish tRNAs as central regulators of mRNA translation dynamics, and therefore cotranslational folding and function of the encoded protein. The tRNA pool, whose composition and abundance change in a cell- and tissue-dependent manner, is the main factor which determines mRNA translation velocity. In this review, we discuss a group of pathogenic mutations, in the coding sequences of either protein-coding genes or in tRNA genes, that alter mRNA translation dynamics. We also summarize advances in tRNA biology that have uncovered how variations in tRNA levels on account of genetic mutations affect protein folding and function, and thereby contribute to phenotypic diversity in clinical manifestations.
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Affiliation(s)
- Marcos Davyt
- Institute of Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Nikhil Bharti
- Institute of Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany
| | - Zoya Ignatova
- Institute of Biochemistry and Molecular Biology, University of Hamburg, Hamburg, Germany.
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3
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Halder R, Nissley DA, Sitarik I, Jiang Y, Rao Y, Vu QV, Li MS, Pritchard J, O'Brien EP. How soluble misfolded proteins bypass chaperones at the molecular level. Nat Commun 2023; 14:3689. [PMID: 37344452 DOI: 10.1038/s41467-023-38962-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 05/24/2023] [Indexed: 06/23/2023] Open
Abstract
Subpopulations of soluble, misfolded proteins can bypass chaperones within cells. The extent of this phenomenon and how it happens at the molecular level are unknown. Through a meta-analysis of the experimental literature we find that in all quantitative protein refolding studies there is always a subpopulation of soluble but misfolded protein that does not fold in the presence of one or more chaperones, and can take days or longer to do so. Thus, some misfolded subpopulations commonly bypass chaperones. Using multi-scale simulation models we observe that the misfolded structures that bypass various chaperones can do so because their structures are highly native like, leading to a situation where chaperones do not distinguish between the folded and near-native-misfolded states. More broadly, these results provide a mechanism by which long-time scale changes in protein structure and function can persist in cells because some misfolded states can bypass components of the proteostasis machinery.
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Affiliation(s)
- Ritaban Halder
- Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA
| | - Daniel A Nissley
- Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA
- Department of Statistics, University of Oxford, Oxford, OX1 3LB, UK
| | - Ian Sitarik
- Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA
| | - Yang Jiang
- Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA
| | - Yiyun Rao
- Molecular, Cellular and Integrative Biosciences Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA
| | - Quyen V Vu
- Institute of Physics, Polish Academy of Sciences; Al. Lotnikow 32/46, 02-668, Warsaw, Poland
| | - Mai Suan Li
- Institute of Physics, Polish Academy of Sciences; Al. Lotnikow 32/46, 02-668, Warsaw, Poland
- Institute for Computational Sciences and Technology; Quang Trung Software City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City, Vietnam
| | - Justin Pritchard
- Department of Biomedical Engineering, Pennsylvania State University, State College, PA, 16802, USA
- Huck Institute for the Life Sciences, Pennsylvania State University, State College, PA, 16802, USA
| | - Edward P O'Brien
- Department of Chemistry, Pennsylvania State University, University Park, PA, 16802, USA.
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, 16802, USA.
- Institute for Computational and Data Sciences, Pennsylvania State University, University Park, PA, 16802, USA.
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4
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Densi A, Iyer RS, Bhat PJ. Synonymous and Nonsynonymous Substitutions in Dictyostelium discoideum Ammonium Transporter amtA Are Necessary for Functional Complementation in Saccharomyces cerevisiae. Microbiol Spectr 2023; 11:e0384722. [PMID: 36840598 PMCID: PMC10100761 DOI: 10.1128/spectrum.03847-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 01/24/2023] [Indexed: 02/24/2023] Open
Abstract
Ammonium transporters are present in all three domains of life. They have undergone extensive horizontal gene transfer (HGT), gene duplication, and functional diversification and therefore offer an excellent paradigm to study protein evolution. We attempted to complement a mep1Δmep2Δmep3Δ strain of Saccharomyces cerevisiae (triple-deletion strain), which otherwise cannot grow on ammonium as a sole nitrogen source at concentrations of <3 mM, with amtA of Dictyostelium discoideum, an orthologue of S. cerevisiae MEP2. We observed that amtA did not complement the triple-deletion strain of S. cerevisiae for growth on low-ammonium medium. We isolated two mutant derivatives of amtA (amtA M1 and amtA M2) from a PCR-generated mutant plasmid library that complemented the triple-deletion strain of S. cerevisiae. amtA M1 bears three nonsynonymous and two synonymous substitutions, which are necessary for its functionality. amtA M2 bears two nonsynonymous substitutions and one synonymous substitution, all of which are necessary for functionality. Interestingly, AmtA M1 transports ammonium but does not confer methylamine toxicity, while AmtA M2 transports ammonium and confers methylamine toxicity, demonstrating functional diversification. Preliminary biochemical analyses indicated that the mutants differ in their conformations as well as their mechanisms of ammonium transport. These intriguing results clearly point out that protein evolution cannot be fathomed by studying nonsynonymous and synonymous substitutions in isolation. The above-described observations have significant implications for various facets of biological processes and are discussed in detail. IMPORTANCE Functional diversification following gene duplication is one of the major driving forces of protein evolution. While the role of nonsynonymous substitutions in the functional diversification of proteins is well recognized, knowledge of the role of synonymous substitutions in protein evolution is in its infancy. Using functional complementation, we isolated two functional alleles of the D. discoideum ammonium transporter gene (amtA), which otherwise does not function in S. cerevisiae as an ammonium transporters. One of them is an ammonium transporter, while the other is an ammonium transporter that also confers methylammonium (ammonium analogue) toxicity, suggesting functional diversification. Surprisingly, both alleles require a combination of synonymous and nonsynonymous substitutions for their functionality. These results bring out a hitherto-unknown pathway of protein evolution and pave the way for not only understanding protein evolution but also interpreting single nucleotide polymorphisms (SNPs).
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Affiliation(s)
- Asha Densi
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Revathi S. Iyer
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Paike Jayadeva Bhat
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
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5
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Nissley DA, Jiang Y, Trovato F, Sitarik I, Narayan KB, To P, Xia Y, Fried SD, O’Brien EP. Universal protein misfolding intermediates can bypass the proteostasis network and remain soluble and less functional. Nat Commun 2022; 13:3081. [PMID: 35654797 PMCID: PMC9163053 DOI: 10.1038/s41467-022-30548-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 05/05/2022] [Indexed: 01/12/2023] Open
Abstract
Some misfolded protein conformations can bypass proteostasis machinery and remain soluble in vivo. This is an unexpected observation, as cellular quality control mechanisms should remove misfolded proteins. Three questions, then, are: how do long-lived, soluble, misfolded proteins bypass proteostasis? How widespread are such misfolded states? And how long do they persist? We address these questions using coarse-grain molecular dynamics simulations of the synthesis, termination, and post-translational dynamics of a representative set of cytosolic E. coli proteins. We predict that half of proteins exhibit misfolded subpopulations that bypass molecular chaperones, avoid aggregation, and will not be rapidly degraded, with some misfolded states persisting for months or longer. The surface properties of these misfolded states are native-like, suggesting they will remain soluble, while self-entanglements make them long-lived kinetic traps. In terms of function, we predict that one-third of proteins can misfold into soluble less-functional states. For the heavily entangled protein glycerol-3-phosphate dehydrogenase, limited-proteolysis mass spectrometry experiments interrogating misfolded conformations of the protein are consistent with the structural changes predicted by our simulations. These results therefore provide an explanation for how proteins can misfold into soluble conformations with reduced functionality that can bypass proteostasis, and indicate, unexpectedly, this may be a wide-spread phenomenon.
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Affiliation(s)
- Daniel A. Nissley
- grid.29857.310000 0001 2097 4281Department of Chemistry, Pennsylvania State University, University Park, PA 16802 USA
| | - Yang Jiang
- grid.29857.310000 0001 2097 4281Department of Chemistry, Pennsylvania State University, University Park, PA 16802 USA
| | - Fabio Trovato
- grid.29857.310000 0001 2097 4281Department of Chemistry, Pennsylvania State University, University Park, PA 16802 USA
| | - Ian Sitarik
- grid.29857.310000 0001 2097 4281Department of Chemistry, Pennsylvania State University, University Park, PA 16802 USA
| | - Karthik B. Narayan
- grid.29857.310000 0001 2097 4281Department of Chemistry, Pennsylvania State University, University Park, PA 16802 USA
| | - Philip To
- grid.21107.350000 0001 2171 9311Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218 USA
| | - Yingzi Xia
- grid.21107.350000 0001 2171 9311Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218 USA
| | - Stephen D. Fried
- grid.21107.350000 0001 2171 9311Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218 USA ,grid.21107.350000 0001 2171 9311Thomas C. Jenkins Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218 USA
| | - Edward P. O’Brien
- grid.29857.310000 0001 2097 4281Department of Chemistry, Pennsylvania State University, University Park, PA 16802 USA ,grid.29857.310000 0001 2097 4281Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802 USA ,grid.29857.310000 0001 2097 4281Institute for Computational and Data Sciences, Pennsylvania State University, University Park, PA 16802 USA
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6
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Fedorov AN. Biosynthetic Protein Folding and Molecular Chaperons. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:S128-S19. [PMID: 35501992 DOI: 10.1134/s0006297922140115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The problem of linear polypeptide chain folding into a unique tertiary structure is one of the fundamental scientific challenges. The process of folding cannot be fully understood without its biological context, especially for big multidomain and multisubunit proteins. The principal features of biosynthetic folding are co-translational folding of growing nascent polypeptide chains and involvement of molecular chaperones in the process. The review summarizes available data on the early events of nascent chain folding, as well as on later advanced steps, including formation of elements of native structure. The relationship between the non-uniformity of translation rate and folding of the growing polypeptide is discussed. The results of studies on the effect of biosynthetic folding features on the parameters of folding as a physical process, its kinetics and mechanisms, are presented. Current understanding and hypotheses on the relationship of biosynthetic folding with the fundamental physical parameters and current views on polypeptide folding in the context of energy landscapes are discussed.
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Affiliation(s)
- Alexey N Fedorov
- Federal Research Center "Fundamentals of Biotechnology", Russian Academy of Sciences, Moscow, 119071, Russia.
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7
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Gao Y, Thiele W, Saleh O, Scossa F, Arabi F, Zhang H, Sampathkumar A, Kühn K, Fernie A, Bock R, Schöttler MA, Zoschke R. Chloroplast translational regulation uncovers nonessential photosynthesis genes as key players in plant cold acclimation. THE PLANT CELL 2022; 34:2056-2079. [PMID: 35171295 PMCID: PMC9048916 DOI: 10.1093/plcell/koac056] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 02/12/2022] [Indexed: 05/04/2023]
Abstract
Plants evolved efficient multifaceted acclimation strategies to cope with low temperatures. Chloroplasts respond to temperature stimuli and participate in temperature sensing and acclimation. However, very little is known about the involvement of chloroplast genes and their expression in plant chilling tolerance. Here we systematically investigated cold acclimation in tobacco seedlings over 2 days of exposure to low temperatures by examining responses in chloroplast genome copy number, transcript accumulation and translation, photosynthesis, cell physiology, and metabolism. Our time-resolved genome-wide investigation of chloroplast gene expression revealed substantial cold-induced translational regulation at both the initiation and elongation levels, in the virtual absence of changes at the transcript level. These cold-triggered dynamics in chloroplast translation are widely distinct from previously described high light-induced effects. Analysis of the gene set responding significantly to the cold stimulus suggested nonessential plastid-encoded subunits of photosynthetic protein complexes as novel players in plant cold acclimation. Functional characterization of one of these cold-responsive chloroplast genes by reverse genetics demonstrated that the encoded protein, the small cytochrome b6f complex subunit PetL, crucially contributes to photosynthetic cold acclimation. Together, our results uncover an important, previously underappreciated role of chloroplast translational regulation in plant cold acclimation.
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Affiliation(s)
- Yang Gao
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Wolfram Thiele
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Omar Saleh
- Institut für Biologie, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Federico Scossa
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
- Council for Agricultural Research and Economics, Research Center for Genomics and Bioinformatics (CREA-GB), Rome, 00178, Italy
| | - Fayezeh Arabi
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Hongmou Zhang
- Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, 12489, Germany
| | - Arun Sampathkumar
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Kristina Kühn
- Institut für Biologie, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), 06120, Germany
| | - Alisdair Fernie
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Ralph Bock
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
| | - Mark A Schöttler
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, 14476, Germany
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8
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Ferrero-Serrano Á, Sylvia MM, Forstmeier PC, Olson AJ, Ware D, Bevilacqua PC, Assmann SM. Experimental demonstration and pan-structurome prediction of climate-associated riboSNitches in Arabidopsis. Genome Biol 2022; 23:101. [PMID: 35440059 PMCID: PMC9017077 DOI: 10.1186/s13059-022-02656-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 03/20/2022] [Indexed: 11/23/2022] Open
Abstract
Background Genome-wide association studies (GWAS) aim to correlate phenotypic changes with genotypic variation. Upon transcription, single nucleotide variants (SNVs) may alter mRNA structure, with potential impacts on transcript stability, macromolecular interactions, and translation. However, plant genomes have not been assessed for the presence of these structure-altering polymorphisms or “riboSNitches.” Results We experimentally demonstrate the presence of riboSNitches in transcripts of two Arabidopsis genes, ZINC RIBBON 3 (ZR3) and COTTON GOLGI-RELATED 3 (CGR3), which are associated with continentality and temperature variation in the natural environment. These riboSNitches are also associated with differences in the abundance of their respective transcripts, implying a role in regulating the gene's expression in adaptation to local climate conditions. We then computationally predict riboSNitches transcriptome-wide in mRNAs of 879 naturally inbred Arabidopsis accessions. We characterize correlations between SNPs/riboSNitches in these accessions and 434 climate descriptors of their local environments, suggesting a role of these variants in local adaptation. We integrate this information in CLIMtools V2.0 and provide a new web resource, T-CLIM, that reveals associations between transcript abundance variation and local environmental variation. Conclusion We functionally validate two plant riboSNitches and, for the first time, demonstrate riboSNitch conditionality dependent on temperature, coining the term “conditional riboSNitch.” We provide the first pan-genome-wide prediction of riboSNitches in plants. We expand our previous CLIMtools web resource with riboSNitch information and with 1868 additional Arabidopsis genomes and 269 additional climate conditions, which will greatly facilitate in silico studies of natural genetic variation, its phenotypic consequences, and its role in local adaptation. Supplementary Information The online version contains supplementary material available at 10.1186/s13059-022-02656-4.
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Affiliation(s)
- Ángel Ferrero-Serrano
- Department of Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA.
| | - Megan M Sylvia
- Department of Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA
| | - Peter C Forstmeier
- Department of Biochemistry, Microbiology, and Molecular Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA
| | - Andrew J Olson
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA
| | - Doreen Ware
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, 11724, USA.,USDA ARS NAA Robert W. Holley Center for Agriculture and Health, Ithaca, NY, 14853, USA
| | - Philip C Bevilacqua
- Department of Biochemistry, Microbiology, and Molecular Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA.,Department of Chemistry, Pennsylvania State University, University Park, State College, PA, 16802, USA.,Center for RNA Molecular Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA
| | - Sarah M Assmann
- Department of Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA. .,Center for RNA Molecular Biology, Pennsylvania State University, University Park, State College, PA, 16802, USA.
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9
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The folding and misfolding mechanisms of multidomain proteins. MEDICINE IN DRUG DISCOVERY 2022. [DOI: 10.1016/j.medidd.2022.100126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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10
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Tao P, Xiao Y. Role of cotranslational folding for β-sheet-enriched proteins: A perspective from molecular dynamics simulations. Phys Rev E 2022; 105:024402. [PMID: 35291071 DOI: 10.1103/physreve.105.024402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
The formations of correct three-dimensional structures of proteins are essential to their functions. Cotranslational folding is vital for proteins to form correct structures in vivo. Although some experiments have shown that cotranslational folding can improve the efficiency of folding, its microscopic mechanism is not yet clear. Previously, we built a model of the ribosomal exit tunnel and investigated the cotranslational folding of a three-helix protein by using all-atom molecular dynamics simulations. Here we study the cotranslational folding of three β-sheet-enriched proteins using the same method. The results show that cotranslational folding can enhance the helical population in most cases and reduce non-native long-range contacts before emerging from the ribosomal exit tunnel. After exiting the tunnel, all proteins fall into local minimal states and the structural ensembles of cotranslational folding show more helical conformations than those of free folding. In particular, for one of the three proteins, the GTT WW domain, we find that one local minimum state of the cotranslational folding is the known folding intermediate, which is not found in free folding. This result suggests that the cotranslational folding may increase the folding efficiency by accelerating the sampling more than by avoiding the misfolded state, which is presently a mainstream viewpoint.
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Affiliation(s)
- Peng Tao
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China
| | - Yi Xiao
- School of Physics, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China
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11
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Sorokina I, Mushegian AR, Koonin EV. Is Protein Folding a Thermodynamically Unfavorable, Active, Energy-Dependent Process? Int J Mol Sci 2022; 23:521. [PMID: 35008947 PMCID: PMC8745595 DOI: 10.3390/ijms23010521] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 12/30/2021] [Accepted: 12/31/2021] [Indexed: 02/04/2023] Open
Abstract
The prevailing current view of protein folding is the thermodynamic hypothesis, under which the native folded conformation of a protein corresponds to the global minimum of Gibbs free energy G. We question this concept and show that the empirical evidence behind the thermodynamic hypothesis of folding is far from strong. Furthermore, physical theory-based approaches to the prediction of protein folds and their folding pathways so far have invariably failed except for some very small proteins, despite decades of intensive theory development and the enormous increase of computer power. The recent spectacular successes in protein structure prediction owe to evolutionary modeling of amino acid sequence substitutions enhanced by deep learning methods, but even these breakthroughs provide no information on the protein folding mechanisms and pathways. We discuss an alternative view of protein folding, under which the native state of most proteins does not occupy the global free energy minimum, but rather, a local minimum on a fluctuating free energy landscape. We further argue that ΔG of folding is likely to be positive for the majority of proteins, which therefore fold into their native conformations only through interactions with the energy-dependent molecular machinery of living cells, in particular, the translation system and chaperones. Accordingly, protein folding should be modeled as it occurs in vivo, that is, as a non-equilibrium, active, energy-dependent process.
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Affiliation(s)
| | - Arcady R. Mushegian
- Division of Molecular and Cellular Biosciences, National Science Foundation, Alexandria, VA 22314, USA;
- Clare Hall College, University of Cambridge, Cambridge CB3 9AL, UK
| | - Eugene V. Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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12
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Tirincsi A, Sicking M, Hadzibeganovic D, Haßdenteufel S, Lang S. The Molecular Biodiversity of Protein Targeting and Protein Transport Related to the Endoplasmic Reticulum. Int J Mol Sci 2021; 23:143. [PMID: 35008565 PMCID: PMC8745461 DOI: 10.3390/ijms23010143] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 12/19/2021] [Accepted: 12/20/2021] [Indexed: 12/15/2022] Open
Abstract
Looking at the variety of the thousands of different polypeptides that have been focused on in the research on the endoplasmic reticulum from the last five decades taught us one humble lesson: no one size fits all. Cells use an impressive array of components to enable the safe transport of protein cargo from the cytosolic ribosomes to the endoplasmic reticulum. Safety during the transit is warranted by the interplay of cytosolic chaperones, membrane receptors, and protein translocases that together form functional networks and serve as protein targeting and translocation routes. While two targeting routes to the endoplasmic reticulum, SRP (signal recognition particle) and GET (guided entry of tail-anchored proteins), prefer targeting determinants at the N- and C-terminus of the cargo polypeptide, respectively, the recently discovered SND (SRP-independent) route seems to preferentially cater for cargos with non-generic targeting signals that are less hydrophobic or more distant from the termini. With an emphasis on targeting routes and protein translocases, we will discuss those functional networks that drive efficient protein topogenesis and shed light on their redundant and dynamic nature in health and disease.
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Affiliation(s)
- Andrea Tirincsi
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Mark Sicking
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Drazena Hadzibeganovic
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
| | - Sarah Haßdenteufel
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7610001, Israel
| | - Sven Lang
- Department of Medical Biochemistry and Molecular Biology, Saarland University, 66421 Homburg, Germany; (A.T.); (M.S.); (D.H.)
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13
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Combinations of slow-translating codon clusters can increase mRNA half-life in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2021; 118:2026362118. [PMID: 34911752 DOI: 10.1073/pnas.2026362118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/18/2021] [Indexed: 11/18/2022] Open
Abstract
The presence of a single cluster of nonoptimal codons was found to decrease a transcript's half-life through the interaction of the ribosome-associated quality control machinery with stalled ribosomes in Saccharomyces cerevisiae The impact of multiple nonoptimal codon clusters on a transcript's half-life, however, is unknown. Using a kinetic model, we predict that inserting a second nonoptimal cluster near the 5' end can lead to synergistic effects that increase a messenger RNA's (mRNA's) half-life in S. cerevisiae Specifically, the 5' end cluster suppresses the formation of ribosome queues, reducing the interaction of ribosome-associated quality control factors with stalled ribosomes. We experimentally validate this prediction by introducing two nonoptimal clusters into three different genes and find that their mRNA half-life increases up to fourfold. The model also predicts that in the presence of two clusters, the cluster closest to the 5' end is the primary determinant of mRNA half-life. These results suggest the "translational ramp," in which nonoptimal codons are located near the start codon and increase translational efficiency, may have the additional biological benefit of allowing downstream slow-codon clusters to be present without decreasing mRNA half-life. These results indicate that codon usage bias plays a more nuanced role in controlling cellular protein levels than previously thought.
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14
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Vu QV, Jiang Y, Li MS, O'Brien EP. The driving force for co-translational protein folding is weaker in the ribosome vestibule due to greater water ordering. Chem Sci 2021; 12:11851-11857. [PMID: 34659725 PMCID: PMC8442680 DOI: 10.1039/d1sc01008e] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 08/02/2021] [Indexed: 01/12/2023] Open
Abstract
Interactions between the ribosome and nascent chain can destabilize folded domains in the ribosome exit tunnel's vestibule, the last 3 nm of the exit tunnel where tertiary folding can occur. Here, we test if a contribution to this destabilization is a weakening of hydrophobic association, the driving force for protein folding. Using all-atom molecular dynamics simulations, we calculate the potential-of-mean force between two methane molecules along the center line of the ribosome exit tunnel and in bulk solution. Associated methanes, we find, are half as stable in the ribosome's vestibule as compared to bulk solution, demonstrating that the hydrophobic effect is weakened by the presence of the ribosome. This decreased stability arises from a decrease in the amount of water entropy gained upon the association of the methanes. And this decreased entropy gain originates from water molecules being more ordered in the vestibule as compared to bulk solution. Therefore, the hydrophobic effect is weaker in the vestibule because waters released from the first solvation shell of methanes upon association do not gain as much entropy in the vestibule as they do upon release in bulk solution. These findings mean that nascent proteins pass through a ribosome vestibule environment that can destabilize folded structures, which has the potential to influence co-translational protein folding pathways, energetics, and kinetics.
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Affiliation(s)
- Quyen V. Vu
- Institute of Physics, Polish Academy of SciencesAl. Lotnikow 32/4602-668 WarsawPoland
| | - Yang Jiang
- Department of Chemistry, Penn State UniversityUniversity ParkPennsylvaniaUSA
| | - Mai Suan Li
- Institute of Physics, Polish Academy of SciencesAl. Lotnikow 32/4602-668 WarsawPoland,Institute for Computational Sciences and TechnologyQuang Trung Software City, Tan Chanh Hiep Ward, District 12Ho Chi Minh CityVietnam
| | - Edward P. O'Brien
- Department of Chemistry, Penn State UniversityUniversity ParkPennsylvaniaUSA,Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Penn State UniversityUniversity ParkPennsylvaniaUSA,Institute for Computational and Data Sciences, Penn State UniversityUniversity ParkPennsylvaniaUSA
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15
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Komar AA. A Code Within a Code: How Codons Fine-Tune Protein Folding in the Cell. BIOCHEMISTRY (MOSCOW) 2021; 86:976-991. [PMID: 34488574 DOI: 10.1134/s0006297921080083] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The genetic code sets the correspondence between the sequence of a given nucleotide triplet in an mRNA molecule, called a codon, and the amino acid that is added to the growing polypeptide chain during protein synthesis. With four bases (A, G, U, and C), there are 64 possible triplet codons: 61 sense codons (encoding amino acids) and 3 nonsense codons (so-called, stop codons that define termination of translation). In most organisms, there are 20 common/standard amino acids used in protein synthesis; thus, the genetic code is redundant with most amino acids (with the exception of Met and Trp) are being encoded by more than one (synonymous) codon. Synonymous codons were initially presumed to have entirely equivalent functions, however, the finding that synonymous codons are not present at equal frequencies in mRNA suggested that the specific codon choice might have functional implications beyond coding for amino acid. Observation of nonequivalent use of codons in mRNAs implied a possibility of the existence of auxiliary information in the genetic code. Indeed, it has been found that genetic code contains several layers of such additional information and that synonymous codons are strategically placed within mRNAs to ensure a particular translation kinetics facilitating and fine-tuning co-translational protein folding in the cell via step-wise/sequential structuring of distinct regions of the polypeptide chain emerging from the ribosome at different points in time. This review summarizes key findings in the field that have identified the role of synonymous codons and their usage in protein folding in the cell.
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Affiliation(s)
- Anton A Komar
- Center for Gene Regulation in Health and Disease and Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH 44115, USA. .,Department of Biochemistry and Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, OH 44106, USA.,Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.,DAPCEL, Inc., Cleveland, OH 44106, USA
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16
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Yadav V, Ullah Irshad I, Kumar H, Sharma AK. Quantitative Modeling of Protein Synthesis Using Ribosome Profiling Data. Front Mol Biosci 2021; 8:688700. [PMID: 34262940 PMCID: PMC8274658 DOI: 10.3389/fmolb.2021.688700] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 05/25/2021] [Indexed: 12/12/2022] Open
Abstract
Quantitative prediction on protein synthesis requires accurate translation initiation and codon translation rates. Ribosome profiling data, which provide steady-state distribution of relative ribosome occupancies along a transcript, can be used to extract these rate parameters. Various methods have been developed in the past few years to measure translation-initiation and codon translation rates from ribosome profiling data. In the review, we provide a detailed analysis of the key methods employed to extract the translation rate parameters from ribosome profiling data. We further discuss how these approaches were used to decipher the role of various structural and sequence-based features of mRNA molecules in the regulation of gene expression. The utilization of these accurate rate parameters in computational modeling of protein synthesis may provide new insights into the kinetic control of the process of gene expression.
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Affiliation(s)
- Vandana Yadav
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | | | - Hemant Kumar
- School of Basic Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar, India
| | - Ajeet K Sharma
- Department of Physics, Indian Institute of Technology Jammu, Jammu, India
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17
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Sharma AK. Translational autoregulation of RF2 protein in E. coli through programmed frameshifting. Phys Rev E 2021; 103:062412. [PMID: 34271674 DOI: 10.1103/physreve.103.062412] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 06/04/2021] [Indexed: 11/07/2022]
Abstract
Various feedback mechanisms regulate the expression of different genes to ensure the required protein levels inside a cell. In this paper, we develop a kinetic model for one such mechanism that autoregulates RF2 protein synthesis in E. coli through programmed frameshifting. The model finds that the programmed frameshifting autoregulates RF2 protein synthesis by two independent mechanisms. First, it increases the rate of RF2 synthesis from each mRNA transcript at low RF2 concentration. Second, programmed frameshifting can dramatically increase the lifetime of RF2 transcripts when RF2 protein levels are lower than a threshold. This sharp increase in mRNA lifetime is caused by a first-order phase transition from a low to a high ribosome density on an RF2 transcript. The high ribosome density prevents the transcript's degradation by shielding it from nucleases, which increases its average lifetime and hence RF2 protein levels. Our study identifies this quality control mechanism that regulates the cellular protein levels by breaking the hierarchy of processes involved in gene expression.
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Affiliation(s)
- Ajeet K Sharma
- Department of Physics, Indian Institute of Technology, Jammu 181221, India
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18
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Maciuba K, Rajasekaran N, Chen X, Kaiser CM. Co-translational folding of nascent polypeptides: Multi-layered mechanisms for the efficient biogenesis of functional proteins. Bioessays 2021; 43:e2100042. [PMID: 33987870 PMCID: PMC8262109 DOI: 10.1002/bies.202100042] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 04/02/2021] [Accepted: 04/07/2021] [Indexed: 11/09/2022]
Abstract
The coupling of protein synthesis and folding is a crucial yet poorly understood aspect of cellular protein folding. Over the past few years, it has become possible to experimentally follow and define protein folding on the ribosome, revealing principles that shape co-translational folding and distinguish it from refolding in solution. Here, we highlight some of these recent findings from biochemical and biophysical studies and their potential significance for cellular protein biogenesis. In particular, we focus on nascent chain interactions with the ribosome, interactions within the nascent protein, modulation of translation elongation rates, and the role of mechanical force that accompanies nascent protein folding. The ability to obtain mechanistic insight in molecular detail has set the stage for exploring the intricate process of nascent protein folding. We believe that the aspects discussed here will be generally important for understanding how protein synthesis and folding are coupled and regulated.
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Affiliation(s)
- Kevin Maciuba
- CMDB Graduate Program, Johns Hopkins University, Baltimore, Maryland, USA
| | | | - Xiuqi Chen
- CMDB Graduate Program, Johns Hopkins University, Baltimore, Maryland, USA
| | - Christian M Kaiser
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Biophysics, Johns Hopkins University, Baltimore, Maryland, USA
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19
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do Couto Bordignon P, Pechmann S. Inferring translational heterogeneity from Saccharomyces cerevisiae ribosome profiling. FEBS J 2021; 288:4541-4559. [PMID: 33539640 DOI: 10.1111/febs.15748] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 01/27/2021] [Accepted: 02/02/2021] [Indexed: 11/30/2022]
Abstract
Translation of mRNAs into proteins by the ribosome is the most important step of protein biosynthesis. Accordingly, translation is tightly controlled and heavily regulated to maintain cellular homeostasis. Ribosome profiling (Ribo-seq) has revolutionized the study of translation by revealing many of its underlying mechanisms. However, equally many aspects of translation remain mysterious, in part also due to persisting challenges in the interpretation of data obtained from Ribo-seq experiments. Here, we show that some of the variability observed in Ribo-seq data has biological origins and reflects programmed heterogeneity of translation. Through a comparative analysis of Ribo-seq data from Saccharomyces cerevisiae, we systematically identify short 3-codon sequences that are differentially translated (DT) across mRNAs, that is, identical sequences that are translated sometimes fast and sometimes slowly beyond what can be attributed to variability between experiments. Remarkably, the thus identified DT sequences link to mechanisms known to regulate translation elongation and are enriched in genes important for protein and organelle biosynthesis. Our results thus highlight examples of translational heterogeneity that are encoded in the genomic sequences and tuned to optimizing cellular homeostasis. More generally, our work highlights the power of Ribo-seq to understand the complexities of translation regulation.
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20
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Liu Y, Yang Q, Zhao F. Synonymous but Not Silent: The Codon Usage Code for Gene Expression and Protein Folding. Annu Rev Biochem 2021; 90:375-401. [PMID: 33441035 DOI: 10.1146/annurev-biochem-071320-112701] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Codon usage bias, the preference for certain synonymous codons, is found in all genomes. Although synonymous mutations were previously thought to be silent, a large body of evidence has demonstrated that codon usage can play major roles in determining gene expression levels and protein structures. Codon usage influences translation elongation speed and regulates translation efficiency and accuracy. Adaptation of codon usage to tRNA expression determines the proteome landscape. In addition, codon usage biases result in nonuniform ribosome decoding rates on mRNAs, which in turn influence the cotranslational protein folding process that is critical for protein function in diverse biological processes. Conserved genome-wide correlations have also been found between codon usage and protein structures. Furthermore, codon usage is a major determinant of mRNA levels through translation-dependent effects on mRNA decay and translation-independent effects on transcriptional and posttranscriptional processes. Here, we discuss the multifaceted roles and mechanisms of codon usage in different gene regulatory processes.
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Affiliation(s)
- Yi Liu
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA;
| | - Qian Yang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA;
| | - Fangzhou Zhao
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA;
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21
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Zhao T, Chen YM, Li Y, Wang J, Chen S, Gao N, Qian W. Disome-seq reveals widespread ribosome collisions that promote cotranslational protein folding. Genome Biol 2021; 22:16. [PMID: 33402206 PMCID: PMC7784341 DOI: 10.1186/s13059-020-02256-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 12/20/2020] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The folding of proteins is challenging in the highly crowded and sticky environment of a cell. Regulation of translation elongation may play a crucial role in ensuring the correct folding of proteins. Much of our knowledge regarding translation elongation comes from the sequencing of mRNA fragments protected by single ribosomes by ribo-seq. However, larger protected mRNA fragments have been observed, suggesting the existence of an alternative and previously hidden layer of regulation. RESULTS In this study, we performed disome-seq to sequence mRNA fragments protected by two stacked ribosomes, a product of translational pauses during which the 5'-elongating ribosome collides with the 3'-paused one. We detected widespread ribosome collisions that are related to slow ribosome release when stop codons are at the A-site, slow peptide bond formation from proline, glycine, asparagine, and cysteine when they are at the P-site, and slow leaving of polylysine from the exit tunnel of ribosomes. The structure of disomes obtained by cryo-electron microscopy suggests a different conformation from the substrate of the ribosome-associated protein quality control pathway. Collisions occurred more frequently in the gap regions between α-helices, where a translational pause can prevent the folding interference from the downstream peptides. Paused or collided ribosomes are associated with specific chaperones, which can aid in the cotranslational folding of the nascent peptides. CONCLUSIONS Therefore, cells use regulated ribosome collisions to ensure protein homeostasis.
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Affiliation(s)
- Taolan Zhao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China. .,Key Laboratory of Genetic Network Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Yan-Ming Chen
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.,Key Laboratory of Genetic Network Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yu Li
- Peking University-Tsinghua University-National Institute of Biological Sciences Joint Graduate Program, School of Life Science, Tsinghua University, Beijing, 100084, China.,State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China
| | - Jia Wang
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.,Key Laboratory of Genetic Network Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Siyu Chen
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.,Key Laboratory of Genetic Network Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Sciences, Peking University, Beijing, 100871, China.
| | - Wenfeng Qian
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China. .,Key Laboratory of Genetic Network Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
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22
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Pechmann S. Programmed Trade-offs in Protein Folding Networks. Structure 2020; 28:1361-1375.e4. [PMID: 33053320 DOI: 10.1016/j.str.2020.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/25/2020] [Accepted: 09/23/2020] [Indexed: 12/14/2022]
Abstract
Molecular chaperones as specialized protein quality control enzymes form the core of cellular protein homeostasis. How chaperones selectively interact with their substrate proteins thus allocate their overall limited capacity remains poorly understood. Here, I present an integrated analysis of sequence and structural determinants that define interactions of protein domains as the basic protein folding unit with the Saccharomyces cerevisiae Hsp70 Ssb. Structural homologs of single-domain proteins that differentially interact with Ssb for de novo folding were found to systematically differ in complexity of their folding landscapes, selective use of nonoptimal codons, and presence of short discriminative sequences, thus highlighting pervasive trade-offs in chaperone-assisted protein folding landscapes. However, short discriminative sequences were found to contribute by far the strongest signal toward explaining Ssb interactions. This observation suggested that some chaperone interactions may be directly programmed in the amino acid sequences rather than responding to folding challenges, possibly for regulatory advantages.
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Affiliation(s)
- Sebastian Pechmann
- Département de biochimie, Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montréal, QC H3T 1J4, Canada.
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23
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A ribosome-associated chaperone enables substrate triage in a cotranslational protein targeting complex. Nat Commun 2020; 11:5840. [PMID: 33203865 PMCID: PMC7673040 DOI: 10.1038/s41467-020-19548-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 10/20/2020] [Indexed: 12/22/2022] Open
Abstract
Protein biogenesis is essential in all cells and initiates when a nascent polypeptide emerges from the ribosome exit tunnel, where multiple ribosome-associated protein biogenesis factors (RPBs) direct nascent proteins to distinct fates. How distinct RPBs spatiotemporally coordinate with one another to affect accurate protein biogenesis is an emerging question. Here, we address this question by studying the role of a cotranslational chaperone, nascent polypeptide-associated complex (NAC), in regulating substrate selection by signal recognition particle (SRP), a universally conserved protein targeting machine. We show that mammalian SRP and SRP receptors (SR) are insufficient to generate the biologically required specificity for protein targeting to the endoplasmic reticulum. NAC co-binds with and remodels the conformational landscape of SRP on the ribosome to regulate its interaction kinetics with SR, thereby reducing the nonspecific targeting of signalless ribosomes and pre-emptive targeting of ribosomes with short nascent chains. Mathematical modeling demonstrates that the NAC-induced regulations of SRP activity are essential for the fidelity of cotranslational protein targeting. Our work establishes a molecular model for how NAC acts as a triage factor to prevent protein mislocalization, and demonstrates how the macromolecular crowding of RPBs at the ribosome exit site enhances the fidelity of substrate selection into individual protein biogenesis pathways.
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24
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Validation of DBFOLD: An efficient algorithm for computing folding pathways of complex proteins. PLoS Comput Biol 2020; 16:e1008323. [PMID: 33196646 PMCID: PMC7704049 DOI: 10.1371/journal.pcbi.1008323] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Revised: 11/30/2020] [Accepted: 10/17/2020] [Indexed: 11/19/2022] Open
Abstract
Atomistic simulations can provide valuable, experimentally-verifiable insights into protein folding mechanisms, but existing ab initio simulation methods are restricted to only the smallest proteins due to severe computational speed limits. The folding of larger proteins has been studied using native-centric potential functions, but such models omit the potentially crucial role of non-native interactions. Here, we present an algorithm, entitled DBFOLD, which can predict folding pathways for a wide range of proteins while accounting for the effects of non-native contacts. In addition, DBFOLD can predict the relative rates of different transitions within a protein’s folding pathway. To accomplish this, rather than directly simulating folding, our method combines equilibrium Monte-Carlo simulations, which deploy enhanced sampling, with unfolding simulations at high temperatures. We show that under certain conditions, trajectories from these two types of simulations can be jointly analyzed to compute unknown folding rates from detailed balance. This requires inferring free energies from the equilibrium simulations, and extrapolating transition rates from the unfolding simulations to lower, physiologically-reasonable temperatures at which the native state is marginally stable. As a proof of principle, we show that our method can accurately predict folding pathways and Monte-Carlo rates for the well-characterized Streptococcal protein G. We then show that our method significantly reduces the amount of computation time required to compute the folding pathways of large, misfolding-prone proteins that lie beyond the reach of existing direct simulation. Our algorithm, which is available online, can generate detailed atomistic models of protein folding mechanisms while shedding light on the role of non-native intermediates which may crucially affect organismal fitness and are frequently implicated in disease. Many proteins must adopt a specific structure in order to function. Computational simulations have been used to shed light on the mechanisms of protein folding, but unfortunately, realistic simulations can typically only be run for small proteins, due to severe limits in computational speed. Here, we present a method to solve this problem, whereby instead of directly simulating folding from an unfolded state, we run simulations that allow for computation of equilibrium folding free energies, alongside high temperature simulations to compute unfolding rates. From these quantities, folding rates can be computed using detailed balance. Importantly, our method can account for the effects of nonnative contacts which transiently form during folding and must be broken prior to adoption of the native state. Such contacts, which are often excluded from simple models of folding, may crucially affect real protein folding pathways and are often observed in folding intermediates implicated in disease.
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25
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Ahmed N, Friedrich UA, Sormanni P, Ciryam P, Altman NS, Bukau B, Kramer G, O'Brien EP. Pairs of amino acids at the P- and A-sites of the ribosome predictably and causally modulate translation-elongation rates. J Mol Biol 2020; 432:166696. [PMID: 33152326 DOI: 10.1016/j.jmb.2020.10.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 08/30/2020] [Accepted: 10/19/2020] [Indexed: 12/31/2022]
Abstract
Variation in translation-elongation kinetics along a transcript's coding sequence plays an important role in the maintenance of cellular protein homeostasis by regulating co-translational protein folding, localization, and maturation. Translation-elongation speed is influenced by molecular factors within mRNA and protein sequences. For example, the presence of proline in the ribosome's P- or A-site slows down translation, but the effect of other pairs of amino acids, in the context of all 400 possible pairs, has not been characterized. Here, we study Saccharomyces cerevisiae using a combination of bioinformatics, mutational experiments, and evolutionary analyses, and show that many different pairs of amino acids and their associated tRNA molecules predictably and causally encode translation rate information when these pairs are present in the A- and P-sites of the ribosome independent of other factors known to influence translation speed including mRNA structure, wobble base pairing, tripeptide motifs, positively charged upstream nascent chain residues, and cognate tRNA concentration. The fast-translating pairs of amino acids that we identify are enriched four-fold relative to the slow-translating pairs across Saccharomyces cerevisiae's proteome, while the slow-translating pairs are enriched downstream of domain boundaries. Thus, the chemical identity of amino acid pairs contributes to variability in translation rates, elongation kinetics are causally encoded in the primary structure of proteins, and signatures of evolutionary selection indicate their potential role in co-translational processes.
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Affiliation(s)
- Nabeel Ahmed
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA
| | - Ulrike A Friedrich
- Center for Molecular Biology of the Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany; German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Pietro Sormanni
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
| | - Prajwal Ciryam
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, UK
| | - Naomi S Altman
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA; Department of Statistics, Pennsylvania State University, University Park, PA, 16802, USA
| | - Bernd Bukau
- Center for Molecular Biology of the Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany; German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Günter Kramer
- Center for Molecular Biology of the Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Im Neuenheimer Feld 282, 69120 Heidelberg, Germany; German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Edward P O'Brien
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA; Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA; Institute for Computational and Data Sciences, Pennsylvania State University, University Park, PA 16802, USA.
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26
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Effect of Protein Structure on Evolution of Cotranslational Folding. Biophys J 2020; 119:1123-1134. [PMID: 32857962 DOI: 10.1016/j.bpj.2020.06.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 06/14/2020] [Accepted: 06/23/2020] [Indexed: 12/31/2022] Open
Abstract
Cotranslational folding depends on the folding speed and stability of the nascent protein. It remains difficult, however, to predict which proteins cotranslationally fold. Here, we simulate evolution of model proteins to investigate how native structure influences evolution of cotranslational folding. We developed a model that connects protein folding during and after translation to cellular fitness. Model proteins evolved improved folding speed and stability, with proteins adopting one of two strategies for folding quickly. Low contact order proteins evolve to fold cotranslationally. Such proteins adopt native conformations early on during the translation process, with each subsequently translated residue establishing additional native contacts. On the other hand, high contact order proteins tend not to be stable in their native conformations until the full chain is nearly extruded. We also simulated evolution of slowly translating codons, finding that slower translation speeds at certain positions enhances cotranslational folding. Finally, we investigated real protein structures using a previously published data set that identified evolutionarily conserved rare codons in Escherichia coli genes and associated such codons with cotranslational folding intermediates. We found that protein substructures preceding conserved rare codons tend to have lower contact orders, in line with our finding that lower contact order proteins are more likely to fold cotranslationally. Our work shows how evolutionary selection pressure can cause proteins with local contact topologies to evolve cotranslational folding.
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27
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Rojano-Nisimura AM, Haning K, Janovsky J, Vasquez KA, Thompson JP, Contreras LM. Codon Selection Affects Recruitment of Ribosome-Associating Factors during Translation. ACS Synth Biol 2020; 9:329-342. [PMID: 31769967 DOI: 10.1021/acssynbio.9b00344] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An intriguing aspect of protein synthesis is how cotranslational events are managed inside the cell. In this study, we developed an in vivo bimolecular fluorescence complementation assay coupled to SecM stalling (BiFC-SecM) to study how codon usage influences the interactions of ribosome-associating factors that occur cotranslationally. We profiled ribosomal associations of a number of proteins, and observed differential association of chaperone proteins TF, DnaK, GroEL, and translocation factor Ffh as a result of introducing synonymous codon substitutions that change the affinity of the translating sequence to the ribosomal anti-Shine-Dalgarno (aSD) sequence. The use of pausing sequences within proteins regulates their transit within the translating ribosome. Our results indicate that the dynamics between cellular factors and the new polypeptide chain are affected by how codon composition is designed. Furthermore, associating factors may play a role in processes including protein quality control (folding and degradation) and cellular respiration.
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Affiliation(s)
- Alejandra M. Rojano-Nisimura
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Stop A4800, Austin, Texas 78712, United States
| | - Katie Haning
- McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E. Dean Keeton Street Stop C0400, Austin, Texas 78712, United States
| | - Justin Janovsky
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Stop A4800, Austin, Texas 78712, United States
| | - Kevin A. Vasquez
- McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E. Dean Keeton Street Stop C0400, Austin, Texas 78712, United States
| | - Jeffrey P. Thompson
- McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E. Dean Keeton Street Stop C0400, Austin, Texas 78712, United States
| | - Lydia M. Contreras
- McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 E. Dean Keeton Street Stop C0400, Austin, Texas 78712, United States
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28
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Gershenson A, Gosavi S, Faccioli P, Wintrode PL. Successes and challenges in simulating the folding of large proteins. J Biol Chem 2020; 295:15-33. [PMID: 31712314 PMCID: PMC6952611 DOI: 10.1074/jbc.rev119.006794] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Computational simulations of protein folding can be used to interpret experimental folding results, to design new folding experiments, and to test the effects of mutations and small molecules on folding. However, whereas major experimental and computational progress has been made in understanding how small proteins fold, research on larger, multidomain proteins, which comprise the majority of proteins, is less advanced. Specifically, large proteins often fold via long-lived partially folded intermediates, whose structures, potentially toxic oligomerization, and interactions with cellular chaperones remain poorly understood. Molecular dynamics based folding simulations that rely on knowledge of the native structure can provide critical, detailed information on folding free energy landscapes, intermediates, and pathways. Further, increases in computational power and methodological advances have made folding simulations of large proteins practical and valuable. Here, using serpins that inhibit proteases as an example, we review native-centric methods for simulating the folding of large proteins. These synergistic approaches range from Gō and related structure-based models that can predict the effects of the native structure on folding to all-atom-based methods that include side-chain chemistry and can predict how disease-associated mutations may impact folding. The application of these computational approaches to serpins and other large proteins highlights the successes and limitations of current computational methods and underscores how computational results can be used to inform experiments. These powerful simulation approaches in combination with experiments can provide unique insights into how large proteins fold and misfold, expanding our ability to predict and manipulate protein folding.
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Affiliation(s)
- Anne Gershenson
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003; Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, Massachusetts 01003.
| | - Shachi Gosavi
- Simons Centre for the Study of Living Machines, National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bangalore-560065, India.
| | - Pietro Faccioli
- Dipartimento di Fisica, Universitá degli Studi di Trento, 38122 Povo (Trento), Italy; Trento Institute for Fundamental Physics and Applications, 38123 Povo (Trento), Italy.
| | - Patrick L Wintrode
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland 21201.
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29
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Abstract
Large proteins composed of multiple domains are abundant in all proteomes, but their folding and structural dynamics remain poorly understood. Using single-molecule force spectroscopy, we have defined how stabilizing interfaces among the domains of elongation factor G (EF-G) shape its folding pathway. Contrary to the expectation that multidomain proteins fold sequentially as they emerge from the ribosome, we find that folding cannot be completed until the full protein has been synthesized. This posttranslational folding mechanism results in a propensity for misfolding. It is dictated by an energetic coupling among domains that enables conformational flexibility crucial for EF-G function. EF-G thus provides an example of how distinct biological ends—robust folding and functionally important flexibility—come into conflict during protein biogenesis. Large proteins with multiple domains are thought to fold cotranslationally to minimize interdomain misfolding. Once folded, domains interact with each other through the formation of extensive interfaces that are important for protein stability and function. However, multidomain protein folding and the energetics of domain interactions remain poorly understood. In elongation factor G (EF-G), a highly conserved protein composed of 5 domains, the 2 N-terminal domains form a stably structured unit cotranslationally. Using single-molecule optical tweezers, we have defined the steps leading to fully folded EF-G. We find that the central domain III of EF-G is highly dynamic and does not fold upon emerging from the ribosome. Surprisingly, a large interface with the N-terminal domains does not contribute to the stability of domain III. Instead, it requires interactions with its folded C-terminal neighbors to be stably structured. Because of the directionality of protein synthesis, this energetic dependency of domain III on its C-terminal neighbors disrupts cotranslational folding and imposes a posttranslational mechanism on the folding of the C-terminal part of EF-G. As a consequence, unfolded domains accumulate during synthesis, leading to the extensive population of misfolded species that interfere with productive folding. Domain III flexibility enables large-scale conformational transitions that are part of the EF-G functional cycle during ribosome translocation. Our results suggest that energetic tuning of domain stabilities, which is likely crucial for EF-G function, complicates the folding of this large multidomain protein.
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30
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Fazzari M, Frasca A, Bifari F, Landsberger N. Aminoglycoside drugs induce efficient read-through of CDKL5 nonsense mutations, slightly restoring its kinase activity. RNA Biol 2019; 16:1414-1423. [PMID: 31232219 DOI: 10.1080/15476286.2019.1632633] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The X-linked CDKL5 gene codes for a kinase whose mutations have been associated with a suite of neurodevelopmental disorders generally characterized by early-onset epileptic encephalopathy and severe intellectual disability. The impact of these mutations on CDKL5 functions and brain development remain mainly unknown, although the importance of maintaining the catalytic activity is generally recognized. Since no cure exists for CDKL5 disorders, the demand for innovative therapies is a real emergency. The recent discovery that CDKL5 is dosage sensitive poses concerns on conventional protein and gene augmentative therapies. Thus, RNA-based therapeutic approaches might be preferred. We studied the efficacy of read-through therapy on CDKL5 premature termination codons (PTCs) that correspond roughly to 15% of all mutations. Our results provide the first demonstration that all tested CDKL5 nonsense mutations are efficiently suppressed by aminoglycoside drugs. The functional characterization of the restored full-length CDKL5 reveals that read-through proteins fully recover their subcellular localization, but only partially rescue their catalytic activity. Since read-through can cause amino acid substitution, CDKL5 patients carrying the PTC outside the catalytic domain might benefit more from a nonsense suppression therapy. Eventually, we demonstrate that non-aminoglycoside drugs, such as Ataluren (PTC124) and GJ072, are unable to induce read-through activity on CDKL5 PTCs. Although these drugs might be more effective in vivo, these results question the validity of the Ataluren phase 2 clinical trial that is currently ongoing on CDKL5 patients.
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Affiliation(s)
- Maria Fazzari
- Department of Medical Biotechnology and Translational Medicine, University of Milan , Segrate , Italy
| | - Angelisa Frasca
- Department of Medical Biotechnology and Translational Medicine, University of Milan , Segrate , Italy
| | - Francesco Bifari
- Department of Medical Biotechnology and Translational Medicine, University of Milan , Segrate , Italy
| | - Nicoletta Landsberger
- Department of Medical Biotechnology and Translational Medicine, University of Milan , Segrate , Italy
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31
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Kramer G, Shiber A, Bukau B. Mechanisms of Cotranslational Maturation of Newly Synthesized Proteins. Annu Rev Biochem 2019; 88:337-364. [DOI: 10.1146/annurev-biochem-013118-111717] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The timely production of functional proteins is of critical importance for the biological activity of cells. To reach the functional state, newly synthesized polypeptides have to become enzymatically processed, folded, and assembled into oligomeric complexes and, for noncytosolic proteins, translocated across membranes. Key activities of these processes occur cotranslationally, assisted by a network of machineries that transiently engage nascent polypeptides at distinct phases of translation. The sequence of events is tuned by intrinsic features of the nascent polypeptides and timely association of factors with the translating ribosome. Considering the dynamics of translation, the heterogeneity of cellular proteins, and the diversity of interaction partners, it is a major cellular achievement that these processes are temporally and spatially so precisely coordinated, minimizing the generation of damaged proteins. This review summarizes the current progress we have made toward a comprehensive understanding of the cotranslational interactions of nascent chains, which pave the way to their functional state.
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Affiliation(s)
- Günter Kramer
- Center for Molecular Biology of Heidelberg University (ZMBH) and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;,
| | - Ayala Shiber
- Center for Molecular Biology of Heidelberg University (ZMBH) and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;,
| | - Bernd Bukau
- Center for Molecular Biology of Heidelberg University (ZMBH) and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;,
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32
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Sharma AK, Sormanni P, Ahmed N, Ciryam P, Friedrich UA, Kramer G, O’Brien EP. A chemical kinetic basis for measuring translation initiation and elongation rates from ribosome profiling data. PLoS Comput Biol 2019; 15:e1007070. [PMID: 31120880 PMCID: PMC6559674 DOI: 10.1371/journal.pcbi.1007070] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 06/11/2019] [Accepted: 05/06/2019] [Indexed: 01/23/2023] Open
Abstract
Analysis methods based on simulations and optimization have been previously developed to estimate relative translation rates from next-generation sequencing data. Translation involves molecules and chemical reactions, hence bioinformatics methods consistent with the laws of chemistry and physics are more likely to produce accurate results. Here, we derive simple equations based on chemical kinetic principles to measure the translation-initiation rate, transcriptome-wide elongation rate, and individual codon translation rates from ribosome profiling experiments. Our methods reproduce the known rates from ribosome profiles generated from detailed simulations of translation. By applying our methods to data from S. cerevisiae and mouse embryonic stem cells, we find that the extracted rates reproduce expected correlations with various molecular properties, and we also find that mouse embryonic stem cells have a global translation speed of 5.2 AA/s, in agreement with previous reports that used other approaches. Our analysis further reveals that a codon can exhibit up to 26-fold variability in its translation rate depending upon its context within a transcript. This broad distribution means that the average translation rate of a codon is not representative of the rate at which most instances of that codon are translated, and it suggests that translational regulation might be used by cells to a greater degree than previously thought.
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Affiliation(s)
- Ajeet K. Sharma
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Pietro Sormanni
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Nabeel Ahmed
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Prajwal Ciryam
- Centre for Misfolding Diseases, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ulrike A. Friedrich
- Center for Molecular Biology of the Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
- German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Günter Kramer
- Center for Molecular Biology of the Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany
- German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Edward P. O’Brien
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Institute for CyberScience, Pennsylvania State University, University Park, Pennsylvania, United States of America
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33
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Ahmed N, Sormanni P, Ciryam P, Vendruscolo M, Dobson CM, O'Brien EP. Identifying A- and P-site locations on ribosome-protected mRNA fragments using Integer Programming. Sci Rep 2019; 9:6256. [PMID: 31000737 PMCID: PMC6472398 DOI: 10.1038/s41598-019-42348-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 03/29/2019] [Indexed: 01/21/2023] Open
Abstract
Identifying the A- and P-site locations on ribosome-protected mRNA fragments from Ribo-Seq experiments is a fundamental step in the quantitative analysis of transcriptome-wide translation properties at the codon level. Many analyses of Ribo-Seq data have utilized heuristic approaches applied to a narrow range of fragment sizes to identify the A-site. In this study, we use Integer Programming to identify the A-site by maximizing an objective function that reflects the fact that the ribosome’s A-site on ribosome-protected fragments must reside between the second and stop codons of an mRNA. This identifies the A-site location as a function of the fragment’s size and its 5′ end reading frame in Ribo-Seq data generated from S. cerevisiae and mouse embryonic stem cells. The correctness of the identified A-site locations is demonstrated by showing that this method, as compared to others, yields the largest ribosome density at established stalling sites. By providing greater accuracy and utilization of a wider range of fragment sizes, our approach increases the signal-to-noise ratio of underlying biological signals associated with translation elongation at the codon length scale.
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Affiliation(s)
- Nabeel Ahmed
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA
| | - Pietro Sormanni
- Department of Chemistry, University of Cambridge, Cambridge, UK
| | - Prajwal Ciryam
- Department of Chemistry, University of Cambridge, Cambridge, UK.,Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | | | | | - Edward P O'Brien
- Bioinformatics and Genomics Graduate Program, The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA. .,Institute of Cyber Science, Pennsylvania State University, University Park, PA, USA. .,Department of Chemistry, Pennsylvania State University, University Park, PA, USA.
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34
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Biddle JW, Nguyen M, Gunawardena J. Negative reciprocity, not ordered assembly, underlies the interaction of Sox2 and Oct4 on DNA. eLife 2019; 8:41017. [PMID: 30762521 PMCID: PMC6375704 DOI: 10.7554/elife.41017] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Accepted: 01/13/2019] [Indexed: 01/30/2023] Open
Abstract
The mode of interaction of transcription factors (TFs) on eukaryotic genomes remains a matter of debate. Single-molecule data in living cells for the TFs Sox2 and Oct4 were previously interpreted as evidence of ordered assembly on DNA. However, the quantity that was calculated does not determine binding order but, rather, energy expenditure away from thermodynamic equilibrium. Here, we undertake a rigorous biophysical analysis which leads to the concept of reciprocity. The single-molecule data imply that Sox2 and Oct4 exhibit negative reciprocity, with expression of Sox2 increasing Oct4’s genomic binding but expression of Oct4 decreasing Sox2’s binding. Models show that negative reciprocity can arise either from energy expenditure or from a mixture of positive and negative cooperativity at distinct genomic loci. Both possibilities imply unexpected complexity in how TFs interact on DNA, for which single-molecule methods provide novel detection capabilities. The bodies of humans and other animals contain many types of cells that perform different roles in the body. Most cells in the body carry the same DNA, which is arranged into sections known as genes. The marked differences between cell types arise because different sets of genes are switched on or ‘expressed’. Proteins called transcription factors control which genes are expressed by binding to DNA and recruiting groups of accessory proteins. However, it is not clear how they interact with each other and with the accessory proteins to decide whether to express a gene. For instance, it is thought that some accessory proteins may provide energy for this process, but it is unknown whether the energy is used continuously or only for a short time. Insights from physics suggest that the former could have more powerful effects. In 2014, a team of researchers reported using a microscopy approach, known as single-molecule imaging, to follow two transcription factors called Sox2 and Oct4 in cells from mice. After analyzing the data, the researchers concluded that Sox2 and Oct4 had a specific order of binding to DNA, with Sox2 often binding first and then assisting Oct4 to bind. Now Biddle et al. report that the claim made in the 2014 study is unsupported because of errors in the way the data were analyzed. In particular, Biddle et al. argue that what the earlier study actually calculated is not an order of binding but a measure of whether energy is being continuously used when Sox2 and Oct4 bind to DNA. Biddle et al. reanalyzed the data from the 2014 work and concluded that Sox2 increases the extent of Oct4 binding to DNA, while Oct4 decreases the amount of Sox2 binding to DNA. Mathematical models suggest this may be due to the continuous use of energy as the two proteins bind to DNA. Alternatively, it could also happen if Sox2 and Oct4 helped each other to bind at some sites on DNA and hindered each other from binding in other places, even if energy is only used for a short time. These findings reveal that there is unexpected complexity in how transcription factors bind to DNA. The next step following on from this work is to carry out experiments that test the two possible explanations for how Sox2 and Oct4 interact on DNA. Including physics in the analysis may help describe more accurately the biology of how transcription factors determine gene expression. Understanding this process will shed new light on many important biological questions and may aid the development of gene therapy and other new medical techniques.
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Affiliation(s)
- John W Biddle
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - Maximilian Nguyen
- Department of Systems Biology, Harvard Medical School, Boston, United States
| | - Jeremy Gunawardena
- Department of Systems Biology, Harvard Medical School, Boston, United States
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35
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A small single-domain protein folds through the same pathway on and off the ribosome. Proc Natl Acad Sci U S A 2018; 115:12206-12211. [PMID: 30409803 DOI: 10.1073/pnas.1810517115] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In vivo, proteins fold and function in a complex environment subject to many stresses that can modulate a protein's energy landscape. One aspect of the environment pertinent to protein folding is the ribosome, since proteins have the opportunity to fold while still bound to the ribosome during translation. We use a combination of force and chemical denaturant (chemomechanical unfolding), as well as point mutations, to characterize the folding mechanism of the src SH3 domain both as a stalled ribosome nascent chain and free in solution. Our results indicate that src SH3 folds through the same pathway on and off the ribosome. Molecular simulations also indicate that the ribosome does not affect the folding pathway for this small protein. Taken together, we conclude that the ribosome does not alter the folding mechanism of this small protein. These results, if general, suggest the ribosome may exert a bigger influence on the folding of multidomain proteins or protein domains that can partially fold before the entire domain sequence is outside the ribosome exit tunnel.
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36
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Abstract
Stress conditions curtail the energetically costly process of messenger RNA translation. In this issue of Science Signaling, Torrent et al. report key evidence for a direct link between codon usage and translation regulation in response to stress.
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Affiliation(s)
- Sebastian Pechmann
- Department of Biochemistry, Université de Montréal, C.P. 6128, Succ. Centre-ville, Montréal, Québec H3C 3J7, Canada.
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