1
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Wienecke AN, Barry ML, Pollard DA. Natural variation in codon bias and mRNA folding strength interact synergistically to modify protein expression in Saccharomyces cerevisiae. Genetics 2023; 224:iyad113. [PMID: 37310925 PMCID: PMC10411576 DOI: 10.1093/genetics/iyad113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 04/10/2023] [Accepted: 05/15/2023] [Indexed: 06/15/2023] Open
Abstract
Codon bias and mRNA folding strength (mF) are hypothesized molecular mechanisms by which polymorphisms in genes modify protein expression. Natural patterns of codon bias and mF across genes as well as effects of altering codon bias and mF suggest that the influence of these 2 mechanisms may vary depending on the specific location of polymorphisms within a transcript. Despite the central role codon bias and mF may play in natural trait variation within populations, systematic studies of how polymorphic codon bias and mF relate to protein expression variation are lacking. To address this need, we analyzed genomic, transcriptomic, and proteomic data for 22 Saccharomyces cerevisiae isolates, estimated protein accumulation for each allele of 1,620 genes as the log of protein molecules per RNA molecule (logPPR), and built linear mixed-effects models associating allelic variation in codon bias and mF with allelic variation in logPPR. We found that codon bias and mF interact synergistically in a positive association with logPPR, and this interaction explains almost all the effects of codon bias and mF. We examined how the locations of polymorphisms within transcripts influence their effects and found that codon bias primarily acts through polymorphisms in domain-encoding and 3' coding sequences, while mF acts most significantly through coding sequences with weaker effects from untranslated regions. Our results present the most comprehensive characterization to date of how polymorphisms in transcripts influence protein expression.
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Affiliation(s)
- Anastacia N Wienecke
- Biology Department, Western Washington University, Bellingham, WA 98225, USA
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Margaret L Barry
- Biology Department, Western Washington University, Bellingham, WA 98225, USA
| | - Daniel A Pollard
- Biology Department, Western Washington University, Bellingham, WA 98225, USA
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2
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Hajikarimlou M, Hooshyar M, Sunba N, Nazemof N, Moutaoufik MT, Phanse S, Said KB, Babu M, Holcik M, Samanfar B, Smith M, Golshani A. A Correlation between 3'-UTR of OXA1 Gene and Yeast Mitochondrial Translation. J Fungi (Basel) 2023; 9:jof9040445. [PMID: 37108900 PMCID: PMC10143089 DOI: 10.3390/jof9040445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 03/27/2023] [Accepted: 04/01/2023] [Indexed: 04/29/2023] Open
Abstract
Mitochondria possess their own DNA (mtDNA) and are capable of carrying out their transcription and translation. Although protein synthesis can take place in mitochondria, the majority of the proteins in mitochondria have nuclear origin. 3' and 5' untranslated regions of mRNAs (3'-UTR and 5'-UTR, respectively) are thought to play key roles in directing and regulating the activity of mitochondria mRNAs. Here we investigate the association between the presence of 3'-UTR from OXA1 gene on a prokaryotic reporter mRNA and mitochondrial translation in yeast. OXA1 is a nuclear gene that codes for mitochondrial inner membrane insertion protein and its 3'-UTR is shown to direct its mRNA toward mitochondria. It is not clear, however, if this mRNA may also be translated by mitochondria. In the current study, using a β-galactosidase reporter gene, we provide genetic evidence for a correlation between the presence of 3'-UTR of OXA1 on an mRNA and mitochondrial translation in yeast.
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Affiliation(s)
- Maryam Hajikarimlou
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Mohsen Hooshyar
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Noor Sunba
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Nazila Nazemof
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Mohamed Taha Moutaoufik
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, SK S4S 0A2, Canada
| | - Sadhena Phanse
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, SK S4S 0A2, Canada
| | - Kamaledin B Said
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Department of Pathology and Microbiology, College of Medicine, University of Hail, Hail P.O. Box 2240, Saudi Arabia
| | - Mohan Babu
- Department of Biochemistry, Research and Innovation Centre, University of Regina, Regina, SK S4S 0A2, Canada
| | - Martin Holcik
- Department of Health Sciences, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Bahram Samanfar
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre (ORDC), Ottawa, ON K2H 8S2, Canada
| | - Myron Smith
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Ashkan Golshani
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
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3
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Georgakopoulos-Soares I, Parada GE, Hemberg M. Secondary structures in RNA synthesis, splicing and translation. Comput Struct Biotechnol J 2022; 20:2871-2884. [PMID: 35765654 PMCID: PMC9198270 DOI: 10.1016/j.csbj.2022.05.041] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/19/2022] [Accepted: 05/21/2022] [Indexed: 11/30/2022] Open
Abstract
Even though the functional role of mRNA molecules is primarily decided by the nucleotide sequence, several properties are determined by secondary structure conformations. Examples of secondary structures include long range interactions, hairpins, R-loops and G-quadruplexes and they are formed through interactions of non-adjacent nucleotides. Here, we discuss advances in our understanding of how secondary structures can impact RNA synthesis, splicing, translation and mRNA half-life. During RNA synthesis, secondary structures determine RNA polymerase II (RNAPII) speed, thereby influencing splicing. Splicing is also determined by RNA binding proteins and their binding rates are modulated by secondary structures. For the initiation of translation, secondary structures can control the choice of translation start site. Here, we highlight the mechanisms by which secondary structures modulate these processes, discuss advances in technologies to detect and study them systematically, and consider the roles of RNA secondary structures in disease.
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Affiliation(s)
- Ilias Georgakopoulos-Soares
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, CA, USA
- Institute for Human Genetics, University of California San Francisco, San Francisco, CA, USA
| | - Guillermo E. Parada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, ON M5S 3E1, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5A 1A8, Canada
| | - Martin Hemberg
- Evergrande Center for Immunologic Diseases, Harvard Medical School and Brigham and Women’s Hospital, Boston, MA, USA
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4
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Hector RE, Mertens JA, Nichols NN. Increased expression of the fluorescent reporter protein ymNeonGreen in Saccharomyces cerevisiae by reducing RNA secondary structure near the start codon. BIOTECHNOLOGY REPORTS 2022; 33:e00697. [PMID: 35036336 PMCID: PMC8749125 DOI: 10.1016/j.btre.2021.e00697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 12/22/2021] [Accepted: 12/27/2021] [Indexed: 11/06/2022]
Abstract
Stable secondary RNA structure 3′ of the start codon inhibits ymNeonGreen expression. Removing secondary RNA structure increased expression in S. cerevisiae and E. coli. Expression was increased 2-fold in S. cerevisiae. Expression was increased 3.8-fold in E. coli. Increased expression in S. cerevisiae was promoter independent.
Expression of a new fluorescent reporter protein called mNeonGreen, that is not based on the jellyfish green fluorescent protein (GFP) sequence, shows increased brightness and folding speed compared to enhanced GFP. However, in vivo brightness of mNeonGreen and its yeast-optimized variant ymNeonGreen in S. cerevisiae is lower than expected, limiting the use of this high quantum yield, fast-folding reporter in budding yeast. This study shows that secondary RNA structure near the start codon in the ymNeonGreen ORF inhibits expression in S. cerevisiae. Removing secondary structure, without altering the ymNeonGreen protein sequence, led to a 2 and 4-fold increase in fluorescence when expressed in S. cerevisiae and E. coli, respectively. In S. cerevisiae, increased fluorescence was seen with strong and weak promoters and led to higher transcript levels suggesting greater transcript stability and improved expression in the absence of stable secondary RNA structure near the start codon.
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5
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Tabuchi T, Yokobayashi Y. Cell-free riboswitches. RSC Chem Biol 2021; 2:1430-1440. [PMID: 34704047 PMCID: PMC8496063 DOI: 10.1039/d1cb00138h] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 07/26/2021] [Indexed: 12/16/2022] Open
Abstract
The emerging community of cell-free synthetic biology aspires to build complex biochemical and genetic systems with functions that mimic or even exceed those in living cells. To achieve such functions, cell-free systems must be able to sense and respond to the complex chemical signals within and outside the system. Cell-free riboswitches can detect chemical signals via RNA-ligand interaction and respond by regulating protein synthesis in cell-free protein synthesis systems. In this article, we review synthetic cell-free riboswitches that function in both prokaryotic and eukaryotic cell-free systems reported to date to provide a current perspective on the state of cell-free riboswitch technologies and their limitations.
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Affiliation(s)
- Takeshi Tabuchi
- Nucleic Acid Chemistry and Engineering Unit, Okinawa Institute of Science and Technology Graduate University Onna Okinawa 904-0495 Japan
| | - Yohei Yokobayashi
- Nucleic Acid Chemistry and Engineering Unit, Okinawa Institute of Science and Technology Graduate University Onna Okinawa 904-0495 Japan
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6
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Jazurek-Ciesiolka M, Ciesiolka A, Komur AA, Urbanek-Trzeciak MO, Krzyzosiak WJ, Fiszer A. RAN Translation of the Expanded CAG Repeats in the SCA3 Disease Context. J Mol Biol 2020; 432:166699. [PMID: 33157084 DOI: 10.1016/j.jmb.2020.10.033] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 10/26/2020] [Accepted: 10/26/2020] [Indexed: 01/08/2023]
Abstract
Spinocerebellar ataxia type 3 (SCA3) is a progressive neurodegenerative disorder caused by a CAG repeat expansion in the ATXN3 gene encoding the ataxin-3 protein. Despite extensive research the exact pathogenic mechanisms of SCA3 are still not understood in depth. In the present study, to gain insight into the toxicity induced by the expanded CAG repeats in SCA3, we comprehensively investigated repeat-associated non-ATG (RAN) translation in various cellular models expressing translated or non-canonically translated ATXN3 sequences with an increasing number of CAG repeats. We demonstrate that two SCA3 RAN proteins, polyglutamine (polyQ) and polyalanine (polyA), are found only in the case of CAG repeats of pathogenic length. Despite having distinct cellular localization, RAN polyQ and RAN polyA proteins are very often coexpressed in the same cell, impairing nuclear integrity and inducing apoptosis. We provide for the first time mechanistic insights into SCA3 RAN translation indicating that ATXN3 sequences surrounding the repeat region have an impact on SCA3 RAN translation initiation and efficiency. We revealed that RAN translation of polyQ proteins starts at non-cognate codons upstream of the CAG repeats, whereas RAN polyA proteins are likely translated within repeats. Furthermore, integrated stress response activation enhances SCA3 RAN translation. Our findings suggest that the ATXN3 sequence context plays an important role in triggering SCA3 RAN translation and that SCA3 RAN proteins may cause cellular toxicity.
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Affiliation(s)
- Magdalena Jazurek-Ciesiolka
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
| | - Adam Ciesiolka
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Alicja A Komur
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Martyna O Urbanek-Trzeciak
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Wlodzimierz J Krzyzosiak
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland
| | - Agnieszka Fiszer
- Department of Medical Biotechnology, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland.
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7
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Singh J. Phase Separation of RNA Helicase Triggers Stress-Responsive Translational Switch. Trends Biochem Sci 2020; 45:726-728. [PMID: 32622749 DOI: 10.1016/j.tibs.2020.06.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Accepted: 06/22/2020] [Indexed: 10/24/2022]
Abstract
A swift response to stress requires global translational suppression, excepting stress proteins. Recently, Iserman et al. uncovered that stress-induced phase separation of the RNA helicase Ded1p results in translational suppression of housekeeping transcripts that contain complex 5' untranslated regions (UTRs). Stress-response transcripts with simpler 5' UTRs escape this global translational suppression.
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Affiliation(s)
- Jogender Singh
- Department of Biological Sciences, Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh 462066, India.
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8
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Iserman C, Desroches Altamirano C, Jegers C, Friedrich U, Zarin T, Fritsch AW, Mittasch M, Domingues A, Hersemann L, Jahnel M, Richter D, Guenther UP, Hentze MW, Moses AM, Hyman AA, Kramer G, Kreysing M, Franzmann TM, Alberti S. Condensation of Ded1p Promotes a Translational Switch from Housekeeping to Stress Protein Production. Cell 2020; 181:818-831.e19. [PMID: 32359423 PMCID: PMC7237889 DOI: 10.1016/j.cell.2020.04.009] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 11/16/2019] [Accepted: 04/06/2020] [Indexed: 11/24/2022]
Abstract
Cells sense elevated temperatures and mount an adaptive heat shock response that involves changes in gene expression, but the underlying mechanisms, particularly on the level of translation, remain unknown. Here we report that, in budding yeast, the essential translation initiation factor Ded1p undergoes heat-induced phase separation into gel-like condensates. Using ribosome profiling and an in vitro translation assay, we reveal that condensate formation inactivates Ded1p and represses translation of housekeeping mRNAs while promoting translation of stress mRNAs. Testing a variant of Ded1p with altered phase behavior as well as Ded1p homologs from diverse species, we demonstrate that Ded1p condensation is adaptive and fine-tuned to the maximum growth temperature of the respective organism. We conclude that Ded1p condensation is an integral part of an extended heat shock response that selectively represses translation of housekeeping mRNAs to promote survival under conditions of severe heat stress.
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Affiliation(s)
- Christiane Iserman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Christine Desroches Altamirano
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; BIOTEC and CMCB, Technische Universität Dresden, Tatzberg 47/48, 01307 Dresden, Germany
| | - Ceciel Jegers
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Ulrike Friedrich
- Center for Molecular Biology of the University of Heidelberg, German Cancer Research Center, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Taraneh Zarin
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Anatol W Fritsch
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; Center for Systems Biology Dresden, 01307 Dresden, Germany
| | - Matthäus Mittasch
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; Center for Systems Biology Dresden, 01307 Dresden, Germany
| | - Antonio Domingues
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; Center for Systems Biology Dresden, 01307 Dresden, Germany
| | - Lena Hersemann
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; Center for Systems Biology Dresden, 01307 Dresden, Germany
| | - Marcus Jahnel
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; BIOTEC and CMCB, Technische Universität Dresden, Tatzberg 47/48, 01307 Dresden, Germany
| | - Doris Richter
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; BIOTEC and CMCB, Technische Universität Dresden, Tatzberg 47/48, 01307 Dresden, Germany
| | - Ulf-Peter Guenther
- DKMS Life Science Lab GmbH, St. Petersburger Str. 2, 01069 Dresden, Germany
| | - Matthias W Hentze
- EMBL Heidelberg, Director's Research Unit, Meyerhofstr. 1, 69117 Heidelberg, Germany
| | - Alan M Moses
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Günter Kramer
- Center for Molecular Biology of the University of Heidelberg, German Cancer Research Center, DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany
| | - Moritz Kreysing
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; Center for Systems Biology Dresden, 01307 Dresden, Germany
| | - Titus M Franzmann
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; BIOTEC and CMCB, Technische Universität Dresden, Tatzberg 47/48, 01307 Dresden, Germany
| | - Simon Alberti
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany; BIOTEC and CMCB, Technische Universität Dresden, Tatzberg 47/48, 01307 Dresden, Germany.
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9
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Wang H, Sun L, Gaba A, Qu X. An in vitro single-molecule assay for eukaryotic cap-dependent translation initiation kinetics. Nucleic Acids Res 2020; 48:e6. [PMID: 31722415 PMCID: PMC7145701 DOI: 10.1093/nar/gkz1066] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 10/18/2019] [Accepted: 10/29/2019] [Indexed: 11/12/2022] Open
Abstract
Eukaryotic mRNAs are predominantly translated via the cap-dependent pathway. Initiation is a rate-limiting step in cap-dependent translation and is the main target of translational control mechanisms. There is a lack of high-resolution techniques for characterizing the cap-dependent initiation kinetics. Here, we report an in vitro single-molecule assay that allows characterization of both initiation and peptide chain elongation kinetics for cap-dependent translation. Surprisingly, the histogram of the first-round initiation time is highly asymmetrical and spans a large time range that is several-fold greater than the average peptide synthesis time in translation reactions with a firefly luciferase-encoding mRNA. Both the histogram and single-molecule trajectories reveal an unexpected high-degree of asynchrony in translation activity between mRNA molecules. Furthermore, by inserting a small stem-loop (ΔG = -4.8 kcal/mol) in the middle of the mRNA 5' untranslated region (UTR), our assay robustly detects small changes in budding yeast initiation kinetics, which could not be resolved by bulk luminescence kinetics. Lastly, we demonstrate the general applicability of this assay to distinct cell-free translation systems by using extracts prepared from budding yeast, wheat germ, and rabbit reticulocyte lysates. This assay should facilitate mechanistic studies of eukaryotic cap-dependent translation initiation and translational control.
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Affiliation(s)
- Hongyun Wang
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Lexi Sun
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.,Department of Physiology, Biophysics and Systems Biology, Weill Cornell Graduate School of Medical Sciences, Cornell University, New York, NY 10065, USA
| | - Anthony Gaba
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Xiaohui Qu
- Molecular Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
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10
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De Nijs Y, De Maeseneire SL, Soetaert WK. 5' untranslated regions: the next regulatory sequence in yeast synthetic biology. Biol Rev Camb Philos Soc 2019; 95:517-529. [PMID: 31863552 DOI: 10.1111/brv.12575] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 11/08/2019] [Accepted: 11/28/2019] [Indexed: 01/10/2023]
Abstract
When developing industrial biotechnology processes, Saccharomyces cerevisiae (baker's yeast or brewer's yeast) is a popular choice as a microbial host. Many tools have been developed in the fields of synthetic biology and metabolic engineering to introduce heterologous pathways and tune their expression in yeast. Such tools mainly focus on controlling transcription, whereas post-transcriptional regulation is often overlooked. Herein we discuss regulatory elements found in the 5' untranslated region (UTR) and their influence on protein synthesis. We provide not only an overall picture, but also a set of design rules on how to engineer a 5' UTR. The reader is also referred to currently available models that allow gene expression to be tuned predictably using different 5' UTRs.
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Affiliation(s)
- Yatti De Nijs
- Faculty of Bioscience Engineering, Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Department Biotechnology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Sofie L De Maeseneire
- Faculty of Bioscience Engineering, Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Department Biotechnology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
| | - Wim K Soetaert
- Faculty of Bioscience Engineering, Centre for Industrial Biotechnology and Biocatalysis (InBio.be), Department Biotechnology, Ghent University, Coupure Links 653, 9000, Ghent, Belgium
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11
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Weenink T, van der Hilst J, McKiernan RM, Ellis T. Design of RNA hairpin modules that predictably tune translation in yeast. Synth Biol (Oxf) 2018; 3:ysy019. [PMID: 32995525 PMCID: PMC7445769 DOI: 10.1093/synbio/ysy019] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Modular parts for tuning translation are prevalent in prokaryotic synthetic biology but lacking for eukaryotic synthetic biology. Working in Saccharomyces cerevisiae yeast, we here describe how hairpin RNA structures inserted into the 5′ untranslated region (5′UTR) of mRNAs can be used to tune expression levels by 100-fold by inhibiting translation. We determine the relationship between the calculated free energy of folding in the 5′UTR and in vivo protein abundance, and show that this enables rational design of hairpin libraries that give predicted expression outputs. Our approach is modular, working with different promoters and protein coding sequences, and outperforms promoter mutation as a way to predictably generate a library where a protein is induced to express at a range of different levels. With this new tool, computational RNA sequence design can be used to predictably fine-tune protein production for genes expressed in yeast.
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Affiliation(s)
- Tim Weenink
- Centre for Synthetic Biology, Imperial College London, London SW7 2AZ, UK.,Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Jelle van der Hilst
- Centre for Synthetic Biology, Imperial College London, London SW7 2AZ, UK.,Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Robert M McKiernan
- Centre for Synthetic Biology, Imperial College London, London SW7 2AZ, UK.,Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Tom Ellis
- Centre for Synthetic Biology, Imperial College London, London SW7 2AZ, UK.,Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
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12
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Ogawa A, Murashige Y, Takahashi H. Canonical translation-modulating OFF-riboswitches with a single aptamer binding to a small molecule that function in a higher eukaryotic cell-free expression system. Bioorg Med Chem Lett 2018; 28:2353-2357. [PMID: 29941191 DOI: 10.1016/j.bmcl.2018.06.041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 06/16/2018] [Accepted: 06/18/2018] [Indexed: 12/30/2022]
Abstract
We have found that OFF-riboswitches that ligand-dependently downregulate the canonical translation in a higher eukaryotic expression system (wheat germ extract) can be easily created by inserting a single aptamer into the 5' untranslated region (UTR) of mRNA, even if its ligand is as small as theophylline. The key is the position of the inserted aptamer: the 5' end (+0 position) is much better than other positions for inhibiting canonical translation with the aptamer-ligand complex. The data showed that ribosome loading is suppressed by a rigid structure in the 5' end, and this suppression is dependent on the structure's stability but not on its size. Although this preference of aptamer insertion point contradicts the results in a lower eukaryote, it accords with the fact that the 5'-end structural hindrance is more effective for blocking the ribosome in higher eukaryotes. Therefore, the present type of OFF-riboswitch would function in various higher eukaryotic expression systems.
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Affiliation(s)
- Atsushi Ogawa
- Proteo-Science Center, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan.
| | - Yuta Murashige
- Proteo-Science Center, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
| | - Hajime Takahashi
- Proteo-Science Center, Ehime University, 3 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
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13
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Zydowicz-Machtel P, Swiatkowska A, Popenda Ł, Gorska A, Ciesiołka J. Variants of the 5'-terminal region of p53 mRNA influence the ribosomal scanning and translation efficiency. Sci Rep 2018; 8:1533. [PMID: 29367734 PMCID: PMC5784139 DOI: 10.1038/s41598-018-20010-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 01/11/2018] [Indexed: 12/25/2022] Open
Abstract
The p53 protein is one of the major cell cycle regulators. The protein is expressed as at least twelve protein isoforms resulting from the use of alternative promoters, alternative splicing or downstream initiation codons. Importantly, there is growing evidence that translation initiation of p53 mRNA may be regulated by the structure and length of the naturally occurring variants of the 5′-terminal region of p53 mRNA transcripts. Here, several mRNA constructs were synthesized with variable length of the p53 5′-terminal regions and encoding luciferase reporter protein, and their translation was monitored continuously in situ in a rabbit reticulocyte lysate system. Moreover, four additional mRNA constructs were prepared. In two constructs, the structural context of AUG1 initiation codon was altered while in the other two constructs, characteristic hairpin motifs present in the p53 5′-terminal region were changed. Translation of the last two constructs was also performed in the presence of the cap analogue to test the function of the 5′-terminal region in cap-independent translation initiation. Superposition of several structural factors connected with the length of the 5′-terminal region, stable elements of the secondary structure, structural environment of the initiation codon and IRES elements greatly influenced the ribosomal scanning and translation efficiency.
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Affiliation(s)
- Paulina Zydowicz-Machtel
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland
| | - Agata Swiatkowska
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland
| | - Łukasz Popenda
- NanoBioMedical Centre, Adam Mickiewicz University in Poznan, Umultowska 85, 61-614, Poznan, Poland
| | - Agnieszka Gorska
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland
| | - Jerzy Ciesiołka
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704, Poznan, Poland.
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14
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Dacheux E, Malys N, Meng X, Ramachandran V, Mendes P, McCarthy JEG. Translation initiation events on structured eukaryotic mRNAs generate gene expression noise. Nucleic Acids Res 2017; 45:6981-6992. [PMID: 28521011 PMCID: PMC5499741 DOI: 10.1093/nar/gkx430] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 05/10/2017] [Indexed: 11/14/2022] Open
Abstract
Gene expression stochasticity plays a major role in biology, creating non-genetic cellular individuality and influencing multiple processes, including differentiation and stress responses. We have addressed the lack of knowledge about posttranscriptional contributions to noise by determining cell-to-cell variations in the abundance of mRNA and reporter protein in yeast. Two types of structural element, a stem–loop and a poly(G) motif, not only inhibit translation initiation when inserted into an mRNA 5΄ untranslated region, but also generate noise. The noise-enhancing effect of the stem–loop structure also remains operational when combined with an upstream open reading frame. This has broad significance, since these elements are known to modulate the expression of a diversity of eukaryotic genes. Our findings suggest a mechanism for posttranscriptional noise generation that will contribute to understanding of the generally poor correlation between protein-level stochasticity and transcriptional bursting. We propose that posttranscriptional stochasticity can be linked to cycles of folding/unfolding of a stem–loop structure, or to interconversion between higher-order structural conformations of a G-rich motif, and have created a correspondingly configured computational model that generates fits to the experimental data. Stochastic events occurring during the ribosomal scanning process can therefore feature alongside transcriptional bursting as a source of noise.
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Affiliation(s)
- Estelle Dacheux
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Naglis Malys
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Xiang Meng
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Vinoy Ramachandran
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
| | - Pedro Mendes
- Center for Quantitative Medicine, UConn Health, 263 Farmington Avenue, CT 06030-6033, USA
| | - John E G McCarthy
- Warwick Integrative Synthetic Biology Centre (WISB) and School of Life Sciences, University of Warwick, Gibbet Hill, Coventry CV4 7AL, UK
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15
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Błaszczyk L, Biesiada M, Saha A, Garfinkel DJ, Purzycka KJ. Structure of Ty1 Internally Initiated RNA Influences Restriction Factor Expression. Viruses 2017; 9:v9040074. [PMID: 28394277 PMCID: PMC5408680 DOI: 10.3390/v9040074] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 03/20/2017] [Accepted: 04/03/2017] [Indexed: 12/30/2022] Open
Abstract
The long-terminal repeat retrotransposon Ty1 is the most abundant mobile genetic element in many Saccharomyces cerevisiae isolates. Ty1 retrotransposons contribute to the genetic diversity of host cells, but they can also act as an insertional mutagen and cause genetic instability. Interestingly, retrotransposition occurs at a low level despite a high level of Ty1 RNA, even though S. cerevisiae lacks the intrinsic defense mechanisms that other eukaryotes use to prevent transposon movement. p22 is a recently discovered Ty1 protein that inhibits retrotransposition in a dose-dependent manner. p22 is a truncated form of Gag encoded by internally initiated Ty1i RNA that contains two closely-spaced AUG codons. Mutations of either AUG codon compromise p22 translation. We found that both AUG codons were utilized and that translation efficiency depended on the Ty1i RNA structure. Structural features that stimulated p22 translation were context dependent and present only in Ty1i RNA. Destabilization of the 5′ untranslated region (5′ UTR) of Ty1i RNA decreased the p22 level, both in vitro and in vivo. Our data suggest that protein factors such as Gag could contribute to the stability and translational activity of Ty1i RNA through specific interactions with structural motifs in the RNA.
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Affiliation(s)
- Leszek Błaszczyk
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland.
| | - Marcin Biesiada
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland.
| | - Agniva Saha
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA 30602, USA.
| | - David J Garfinkel
- Department of Biochemistry & Molecular Biology, University of Georgia, Athens, GA 30602, USA.
| | - Katarzyna J Purzycka
- Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan 61-704, Poland.
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16
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Mechanism and Regulation of Protein Synthesis in Saccharomyces cerevisiae. Genetics 2017; 203:65-107. [PMID: 27183566 DOI: 10.1534/genetics.115.186221] [Citation(s) in RCA: 93] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/24/2016] [Indexed: 12/18/2022] Open
Abstract
In this review, we provide an overview of protein synthesis in the yeast Saccharomyces cerevisiae The mechanism of protein synthesis is well conserved between yeast and other eukaryotes, and molecular genetic studies in budding yeast have provided critical insights into the fundamental process of translation as well as its regulation. The review focuses on the initiation and elongation phases of protein synthesis with descriptions of the roles of translation initiation and elongation factors that assist the ribosome in binding the messenger RNA (mRNA), selecting the start codon, and synthesizing the polypeptide. We also examine mechanisms of translational control highlighting the mRNA cap-binding proteins and the regulation of GCN4 and CPA1 mRNAs.
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17
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The molecular choreography of protein synthesis: translational control, regulation, and pathways. Q Rev Biophys 2016; 49:e11. [PMID: 27658712 DOI: 10.1017/s0033583516000056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Translation of proteins by the ribosome regulates gene expression, with recent results underscoring the importance of translational control. Misregulation of translation underlies many diseases, including cancer and many genetic diseases. Decades of biochemical and structural studies have delineated many of the mechanistic details in prokaryotic translation, and sketched the outlines of eukaryotic translation. However, translation may not proceed linearly through a single mechanistic pathway, but likely involves multiple pathways and branchpoints. The stochastic nature of biological processes would allow different pathways to occur during translation that are biased by the interaction of the ribosome with other translation factors, with many of the steps kinetically controlled. These multiple pathways and branchpoints are potential regulatory nexus, allowing gene expression to be tuned at the translational level. As research focus shifts toward eukaryotic translation, certain themes will be echoed from studies on prokaryotic translation. This review provides a general overview of the dynamic data related to prokaryotic and eukaryotic translation, in particular recent findings with single-molecule methods, complemented by biochemical, kinetic, and structural findings. We will underscore the importance of viewing the process through the viewpoints of regulation, translational control, and heterogeneous pathways.
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18
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Terai G, Kamegai S, Asai K. CDSfold: an algorithm for designing a protein-coding sequence with the most stable secondary structure. Bioinformatics 2015; 32:828-34. [DOI: 10.1093/bioinformatics/btv678] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 11/12/2015] [Indexed: 11/13/2022] Open
Abstract
Abstract
Motivation: An important problem in synthetic biology is to design a nucleotide sequence of an mRNA that confers a desirable expression level of a target protein. The secondary structure of protein-coding sequences (CDSs) is one potential factor that could have both positive and negative effects on protein production. To elucidate the role of secondary structure in CDSs, algorithms for manipulating secondary structure should be developed.
Results: We developed an algorithm for designing a CDS with the most stable secondary structure among all possible ones translated into the same protein, and implemented it as the program CDSfold. The algorithm runs the Zuker algorithm under the constraint of a given amino acid sequence. The time and space complexity is O(L3) and O(L2), respectively, where L is the length of the CDS to be designed. Although our algorithm is slower than the original Zuker algorithm, it could design a relatively long (2.7-kb) CDS in approximately 1 h.
Availability and implementation: The CDSfold program is freely available for non-commercial users as stand-alone and web-based software from http://cdsfold.trahed.jp/cdsfold/.
Contacts: terai-goro@aist.go.jp or asai@k.u-tokyo.ac.jp
Supplementary information: Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Goro Terai
- National Institute of Advanced Industrial Science and Technology (AIST), Koto-ku, Tokyo 135-0064, Japan,
- INTEC Inc., Koto-ku, Tokyo 136-8637, Japan and
| | - Satoshi Kamegai
- National Institute of Advanced Industrial Science and Technology (AIST), Koto-ku, Tokyo 135-0064, Japan,
- INTEC Inc., Koto-ku, Tokyo 136-8637, Japan and
| | - Kiyoshi Asai
- National Institute of Advanced Industrial Science and Technology (AIST), Koto-ku, Tokyo 135-0064, Japan,
- Graduate School of Frontier Sciences, University of Tokyo, Kashiwa 277-8562, Japan
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19
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Groher F, Suess B. Synthetic riboswitches - A tool comes of age. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:964-973. [PMID: 24844178 DOI: 10.1016/j.bbagrm.2014.05.005] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 04/29/2014] [Accepted: 05/08/2014] [Indexed: 12/14/2022]
Abstract
Within the last decade, it has become obvious that RNA plays an important role in regulating gene expression. This has led to a plethora of approaches aiming at exploiting the outstanding chemical properties of RNA to develop synthetic RNA regulators for conditional gene expression systems. Consequently, many different regulators have been developed to act on various stages of gene expression. They can be engineered to respond to almost any ligand of choice and are, therefore, of great interest for applications in synthetic biology. This review presents an overview of such engineered riboswitches, discusses their applicability and points out recent trends in their development. This article is part of a Special Issue entitled: Riboswitches.
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Affiliation(s)
- Florian Groher
- Department of Biology, Technical University Darmstadt, 64287 Darmstadt, Germany
| | - Beatrix Suess
- Department of Biology, Technical University Darmstadt, 64287 Darmstadt, Germany.
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20
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Alekhina OM, Vassilenko KS. Translation initiation in eukaryotes: versatility of the scanning model. BIOCHEMISTRY (MOSCOW) 2013; 77:1465-77. [PMID: 23379522 DOI: 10.1134/s0006297912130056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It is generally accepted that the initiation of translation in eukaryotes involves the binding of the 40S ribosomal subunit to the capped 5' end of an mRNA and subsequent scanning of 5' UTR in search of an initiation codon. However, until recently this has remained a mere hypothesis. This review describes the novel experimental evidence in support of this classical model. Data on the participation of various factors in the eukaryotic initiation process are summarized. The sequence of initiation events is described in light of the latest experimental data. The existing physical models of scanning are presented. Special attention is paid to discussion of alternative models of eukaryotic initiation of translation. It is demonstrated that the canonical mechanism of initiation is more versatile than previously thought.
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Affiliation(s)
- O M Alekhina
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
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21
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Deciphering the rules by which 5'-UTR sequences affect protein expression in yeast. Proc Natl Acad Sci U S A 2013; 110:E2792-801. [PMID: 23832786 DOI: 10.1073/pnas.1222534110] [Citation(s) in RCA: 178] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The 5'-untranslated region (5'-UTR) of mRNAs contains elements that affect expression, yet the rules by which these regions exert their effect are poorly understood. Here, we studied the impact of 5'-UTR sequences on protein levels in yeast, by constructing a large-scale library of mutants that differ only in the 10 bp preceding the translational start site of a fluorescent reporter. Using a high-throughput sequencing strategy, we obtained highly accurate measurements of protein abundance for over 2,000 unique sequence variants. The resulting pool spanned an approximately sevenfold range of protein levels, demonstrating the powerful consequences of sequence manipulations of even 1-10 nucleotides immediately upstream of the start codon. We devised computational models that predicted over 70% of the measured expression variability in held-out sequence variants. Notably, a combined model of the most prominent features successfully explained protein abundance in an additional, independently constructed library, whose nucleotide composition differed greatly from the library used to parameterize the model. Our analysis reveals the dominant contribution of the start codon context at positions -3 to -1, mRNA secondary structure, and out-of-frame upstream AUGs (uAUGs) to phenotypic diversity, thereby advancing our understanding of how protein levels are modulated by 5'-UTR sequences, and paving the way toward predictably tuning protein expression through manipulations of 5'-UTRs.
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22
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Suga K, Tanabe T, Umakoshi H. Heterogeneous cationic liposomes modified with 3β-{N-[(N',N'-dimethylamino)ethyl]carbamoyl}cholesterol can induce partial conformational changes in messenger RNA and regulate translation in an Escherichia coli cell-free translation system. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:1899-1907. [PMID: 23323854 DOI: 10.1021/la3050576] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The effect of cationic liposomes (CLs) on messenger RNA(mRNA) conformation and translation was studied, focusing on membrane heterogeneity. CLs, composed of 1,2-dioleoyl-sn-glycerol-3-phosphocholine/1,2-dioleoyl-3-timethylammonium propane (DOPC/DOTAP) and DOPC/3β-{N-[(N',N'-dimethylamino)ethyl]carbamoyl}cholesterol (DOPC/DC-Ch), inhibited mRNA translation in an Escherichia coli cell-free translation system. Analysis of the membrane fluidity and polarity indicated a heterogeneous DOPC/DC-Ch (70/30) membrane, while other CLs exhibited homogeneous disordered membranes. mRNA adsorbed onto DOPC/DC-Ch liposomes showed translational activity, while DOPC/DOTAP liposomes inhibited mRNA translation in proportion to its adsorption onto membranes. Dehydration of DOPC/DOTAP (70/30) and DOPC/DC-Ch (70/30) was observed in the presence of mRNA but not in the case of zwitterionic DOPC liposomes, indicating that mRNA binds in regions between the phosphate [-PO(2)(-)-] and carbonyl [-C=O-] moieties of lipids. UV resonance Raman spectroscopy suggests that adenine, cytosine, and guanine interact with DOPC/DOTAP (70/30) and DOPC/DC-Ch (70/30) but not with DOPC. Circular dichroism indicates that DOPC/DOTAP (70/30) extensively denatured the mRNA. In contrast, heterogeneous DOPC/DC-Ch (70/30) induced partial conformational changes but maintained the translational activity of mRNA.
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Affiliation(s)
- Keishi Suga
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
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23
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König SLB, Liyanage PS, Sigel RKO, Rueda D. Helicase-mediated changes in RNA structure at the single-molecule level. RNA Biol 2013; 10:133-48. [PMID: 23353571 DOI: 10.4161/rna.23507] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
RNA helicases are a diverse group of RNA-dependent ATPases known to play a large number of biological roles inside the cell, such as RNA unwinding, remodeling, export and degradation. Understanding how helicases mediate changes in RNA structure is therefore of fundamental interest. The advent of single-molecule spectroscopic techniques has unveiled with unprecedented detail the interplay of RNA helicases with their substrates. In this review, we describe the characterization of helicase-RNA interactions by single-molecule approaches. State-of-the-art techniques are presented, followed by a discussion of recent advancements in this exciting field.
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Kemp AJ, Betney R, Ciandrini L, Schwenger ACM, Romano MC, Stansfield I. A yeast tRNA mutant that causes pseudohyphal growth exhibits reduced rates of CAG codon translation. Mol Microbiol 2012; 87:284-300. [PMID: 23146061 PMCID: PMC3664417 DOI: 10.1111/mmi.12096] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/07/2012] [Indexed: 11/27/2022]
Abstract
In Saccharomyces cerevisiae, the SUP70 gene encodes the CAG-decoding tRNA(Gln)(CUG). A mutant allele, sup70-65, induces pseudohyphal growth on rich medium, an inappropriate nitrogen starvation response. This mutant tRNA is also a UAG nonsense suppressor via first base wobble. To investigate the basis of the pseudohyphal phenotype, 10 novel sup70 UAG suppressor alleles were identified, defining positions in the tRNA(Gln)(CUG) anticodon stem that restrict first base wobble. However, none conferred pseudohyphal growth, showing altered CUG anticodon presentation cannot itself induce pseudohyphal growth. Northern blot analysis revealed the sup70-65 tRNA(Gln)(CUG) is unstable, inefficiently charged, and 80% reduced in its effective concentration. A stochastic model simulation of translation predicted compromised expression of CAG-rich ORFs in the tRNA(Gln)(CUG)-depleted sup70-65 mutant. This prediction was validated by demonstrating that luciferase expression in the mutant was 60% reduced by introducing multiple tandem CAG (but not CAA) codons into this ORF. In addition, the sup70-65 pseudohyphal phenotype was partly complemented by overexpressing CAA-decoding tRNA(Gln)(UUG), an inefficient wobble-decoder of CAG. We thus show that introducing codons decoded by a rare tRNA near the 5' end of an ORF can reduce eukaryote translational expression, and that the mutant tRNA(CUG)(Gln) constitutive pseudohyphal differentiation phenotype correlates strongly with reduced CAG decoding efficiency.
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Affiliation(s)
- Alain J Kemp
- Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, UK
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25
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Suga K, Tanabe T, Tomita H, Shimanouchi T, Umakoshi H. Conformational change of single-stranded RNAs induced by liposome binding. Nucleic Acids Res 2011; 39:8891-900. [PMID: 21785134 PMCID: PMC3203612 DOI: 10.1093/nar/gkr568] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The interaction between single-stranded RNAs and liposomes was studied using UV, Fourier Transform Infrared spectroscopy (FTIR) and Circular Dichroism spectroscopy (CD). The effect of the surface characteristics of liposomes, which were composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and modified with cholesterol (Ch) or 1,2-dioleoyl-3-trimethylammonium propane (DOTAP), on the liposome–RNA interaction was investigated. The fluorescence of 6-(p-toluidino)naphthalene-2-sulfonate (TNS) embedded in the liposome surface (ε = 30–40) was decreased in the presence of tRNA, suggesting that single-stranded tRNA could bind onto the liposome. The dehydration of –PO2− –, guanine (G) and cytosine (C) of tRNA molecules in the presence of liposomes suggested both an electrostatic interaction (phosphate backbone of tRNA and trimethylammonium group of POPC, DOTAP) and a hydrophobic interaction (guanine or cytosine of tRNA and aliphatic tail of lipid). The tRNA conformation on the liposome was determined by CD spectroscopy. POPC/Ch (70/30) maintained tRNA conformation without any denaturation, while POPC/DOTAP(70/30) drastically denatured it. The mRNA translation was evaluated in an Escherichia coli cell-free translation system. POPC/Ch(70/30) enhanced expression of green fluorescent protein (GFP) (116%) while POPC/DOTAP(70/30) inhibited (37%), suggesting that the conformation of RNAs was closely related to the translation efficiency. Therefore, single-stranded RNAs could bind to liposomal membranes through electrostatic and hydrophobic attraction, after which conformational changes were induced depending on the liposome characteristics.
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Affiliation(s)
- Keishi Suga
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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26
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Vassilenko KS, Alekhina OM, Dmitriev SE, Shatsky IN, Spirin AS. Unidirectional constant rate motion of the ribosomal scanning particle during eukaryotic translation initiation. Nucleic Acids Res 2011; 39:5555-67. [PMID: 21415006 PMCID: PMC3141257 DOI: 10.1093/nar/gkr147] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
According to the model of translation initiation in eukaryotes, the 40S ribosomal subunit binds to capped 5'-end of mRNA and subsequently migrates along 5'-UTR in searching for initiation codon. However, it remains unclear whether the migration is the result of a random one-dimensional diffusion, or it is an energy-driven unidirectional movement. To address this issue, the method of continuous monitoring of protein synthesis in situ was used for high precision measurements of the times required for translation of mRNA with 5'-UTRs of different lengths and structures in mammalian and plant cell-free systems. For the first time, the relationship between the scanning time and the 5'-UTR length was determined and their linear correlation was experimentally demonstrated. The conclusion is made that the ribosome migration is an unidirectional motion with the rate being virtually independent of a particular mRNA sequence and secondary structure.
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Affiliation(s)
- Konstantin S. Vassilenko
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia and A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
| | - Olga M. Alekhina
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia and A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
| | - Sergey E. Dmitriev
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia and A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
| | - Ivan N. Shatsky
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia and A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia
| | - Alexander S. Spirin
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia and A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia,*To whom correspondence should be addressed. Tel: +7 495 514 0218; Fax: +7 495 514 0218;
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Ludwig AL, Hershey JWB, Hagerman PJ. Initiation of translation of the FMR1 mRNA Occurs predominantly through 5'-end-dependent ribosomal scanning. J Mol Biol 2011; 407:21-34. [PMID: 21237174 DOI: 10.1016/j.jmb.2011.01.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Revised: 01/04/2011] [Accepted: 01/04/2011] [Indexed: 01/17/2023]
Abstract
The fragile X mental retardation 1 (FMR1) gene contains a CGG repeat within its 5' untranslated region (5'UTR) that, when expanded to 55-200 CGG repeats (premutation allele), can result in the late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome. The CGG repeat is expected to form a highly stable secondary structure that is capable of inhibiting 5'-cap-dependent translation. Paradoxically, translation in vivo is only mildly impaired within the premutation range, suggesting that other modes of translation initiation may be operating. To address this issue, we translated in vitro a set of reporter mRNAs containing between 0 and 99 CGG repeats in either native (FMR1) or unrelated (heterologous) 5'UTR context. The 5'-cap dependence of translation was assessed by inserting a stable hairpin (HP) near the 5' end of the mRNAs. The results of the current studies indicate that translation initiation of the FMR1 mRNA occurs primarily by scanning, with little evidence of internal ribosome entry or shunting. Additionally, the efficiency of translation initiation depends on transcription start site selection, with the shorter 5'UTR (downstream transcription start site I) translating with greater efficiency compared to the longer mRNA (start site III) for all CGG-repeat elements studied. Lastly, an HP previously shown to block translation gave differing results depending on the 5'UTR context, in one case initiating translation from within the HP.
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Affiliation(s)
- Anna L Ludwig
- Department of Biochemistry and Molecular Medicine, University of California Davis School of Medicine, Davis, CA 95616, USA
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Mitchell SF, Walker SE, Algire MA, Park EH, Hinnebusch AG, Lorsch JR. The 5'-7-methylguanosine cap on eukaryotic mRNAs serves both to stimulate canonical translation initiation and to block an alternative pathway. Mol Cell 2010; 39:950-62. [PMID: 20864040 DOI: 10.1016/j.molcel.2010.08.021] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/20/2010] [Accepted: 08/02/2010] [Indexed: 10/19/2022]
Abstract
Translational control is frequently exerted at the stage of mRNA recruitment to the initiating ribosome. We have reconstituted mRNA recruitment to the 43S preinitiation complex (PIC) using purified S. cerevisiae components. We show that eIF3 and the eIF4 factors not only stabilize binding of mRNA to the PIC, they also dramatically increase the rate of recruitment. Although capped mRNAs require eIF3 and the eIF4 factors for efficient recruitment to the PIC, uncapped mRNAs can be recruited in the presence of eIF3 alone. The cap strongly inhibits this alternative recruitment pathway, imposing a requirement for the eIF4 factors for rapid and stable binding of natural mRNA. Our data suggest that the 5' cap serves as both a positive and negative element in mRNA recruitment, promoting initiation in the presence of the canonical group of mRNA handling factors while preventing binding to the ribosome via an aberrant, alternative pathway requiring only eIF3.
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Affiliation(s)
- Sarah F Mitchell
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Zheng H, Lin S, Zhang Q, Lei Y, Zhang Z. Functional analysis of 5' untranslated region of a TIR-NBS-encoding gene from triploid white poplar. Mol Genet Genomics 2009; 282:381-94. [PMID: 19618215 DOI: 10.1007/s00438-009-0471-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2009] [Accepted: 07/01/2009] [Indexed: 11/27/2022]
Abstract
Genome-wide analyses have identified a set of TIR-NBS-encoding genes in plants. However, the molecular mechanism underlying the expression of these genes is still unknown. In this study, we presented a TIR-NBS-encoding gene, PtDrl02, that displayed a low level of tissue-specific expression in a triploid white poplar [(Populus tomentosa x P. bolleana) x P. tomentosa], and analyzed the effects of the 5' untranslated region (UTR) on gene expression. The 5' UTR sequence repressed the reporter activity of beta-glucuronidase (GUS) gene under PtDrl02 promoter by 113.5-fold with a staining ratio of 2.97% in the transgenic tobacco plants. Quantitative RT-PCR assays revealed that the 5' UTR sequence decreased the transcript level of the GUS reporter gene by 13.3-fold, implying a regulatory role of 5' UTR in transcription and/or mRNA destabilization. The comparison of GUS activity with the transcript abundance indicated that the 5' UTR sequence decreased the translation efficiency of target gene by 88.3%. Additionally, the analysis of the transgenic P-985/UTRDelta/GUS plants showed that both the exon1 sequence and the leading intron within the 5' UTR region were responsible for the regulation of gene expression. Our results suggested a negative effect of the 5' UTR of PtDrl02 gene on gene expression.
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Affiliation(s)
- Huiquan Zheng
- National Engineering Laboratory for Tree Breeding, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants, Ministry of Education, Beijing Forestry University, Beijing 100083, People's Republic of China
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Development of bacteriocinogenic strains of Saccharomyces cerevisiae heterologously expressing and secreting the leaderless enterocin L50 peptides L50A and L50B from Enterococcus faecium L50. Appl Environ Microbiol 2009; 75:2382-92. [PMID: 19218405 DOI: 10.1128/aem.01476-08] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A segregationally stable expression and secretion vector for Saccharomyces cerevisiae, named pYABD01, was constructed by cloning the yeast gene region encoding the mating pheromone alpha-factor 1 secretion signal (MFalpha1(s)) into the S. cerevisiae high-copy-number expression vector pYES2. The structural genes of the two leaderless peptides of enterocin L50 (EntL50A and EntL50B) from Enterococcus faecium L50 were cloned, separately (entL50A or entL50B) and together (entL50AB), into pYABD01 under the control of the galactose-inducible promoter P(GAL1). The generation of recombinant S. cerevisiae strains heterologously expressing and secreting biologically active EntL50A and EntL50B demonstrates the suitability of the MFalpha1(s)-containing vector pYABD01 to direct processing and secretion of these antimicrobial peptides through the S. cerevisiae Sec system.
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Gochhait S, Bukhari SIA, Bairwa N, Vadhera S, Darvishi K, Raish M, Gupta P, Husain SA, Bamezai RNK. Implication of BRCA2 -26G>A 5' untranslated region polymorphism in susceptibility to sporadic breast cancer and its modulation by p53 codon 72 Arg>Pro polymorphism. Breast Cancer Res 2008; 9:R71. [PMID: 17945002 PMCID: PMC2242669 DOI: 10.1186/bcr1780] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2006] [Revised: 06/26/2007] [Accepted: 10/18/2007] [Indexed: 01/13/2023] Open
Abstract
Introduction The absence of mutation or promoter hypermethylation in the BRCA2 gene in the majority of breast cancer cases has indicated alternative ways of its involvement, deregulated expression being one possibility. We show how a polymorphism in the 5' untranslated region (UTR) of BRCA2 can serve as one such factor. Based on the hypothesis that variants of genes involved in the same pathway can influence the risk provided for breast cancer, the status of p53 codon 72 polymorphism was also investigated and a possible interaction between the polymorphisms was examined. Methods The luciferase reporter assay followed by RNA secondary structure analysis was used for the functional characterization of -26 5' UTR G>A polymorphism in BRCA2. The genotype and the allele frequency for the polymorphisms were determined and relative risk adjusted for age was calculated in a case-control study of 576 individuals (243 patients and 333 controls) from north India. Results -26 G>A polymorphism in the 5' UTR of BRCA2 was found to be functional whereby the A allele increased the reporter gene expression by twice that of the G allele in MCF-7 (P = 0.003) and HeLa (P = 0.013) cells. RNA secondary structure analysis by two different programs predicted the A allele to alter the stability of a loop in the vicinity of the translation start site. Its direct implication in breast cancer became evident by a case-control study in which the heterozygous genotype was found to be protective in nature (Pheterozygote advantage model = 0.0005, odds ratio [OR] = 0.5, 95% confidence interval [CI] = 0.4 to 0.8), which was further supported by trends observed in a genomic instability study. The p53 codon 72 Arg homozygous genotype was found to be over-represented in patients (P = 0.0005, OR = 2.3, 95% CI = 1.4 to 3.6). The interaction study indicated an increased protection under simultaneous presence of protector genotypes of both the polymorphic loci (P = 0.0001, OR = 0.2, 95% CI = 0.1 to 0.4). Conclusion Our study shows that -26 5' UTR polymorphism in BRCA2 can modulate the fine-tuned regulation of the multifunctional gene BRCA2 and renders risk or protection according to the genotype status in the sporadic form of breast cancer, which is further influenced by the germline genetic backgrounds of codon 72 polymorphism of p53.
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Affiliation(s)
- Sailesh Gochhait
- National Centre of Applied Human Genetics, School of Life Sciences, Jawaharlal Nehru University, Aruna Asafali Road, New Delhi-110067, India
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Mäkeläinen KJ, Mäkinen K. Testing of internal translation initiation via dicistronic constructs in yeast is complicated by production of extraneous transcripts. Gene 2007; 391:275-84. [PMID: 17331675 DOI: 10.1016/j.gene.2007.01.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Revised: 01/19/2007] [Accepted: 01/19/2007] [Indexed: 10/23/2022]
Abstract
Introduction of sequences of interest into an intercistronic spacer (ICS) of dual reporter plasmids is the main experimental set-up used to identify and study internal ribosome entry sites (IRESs). We studied internal initiation of translation in yeast using the dicistronic approach. Three viral sequences and a polylinker-derived reference sequence were inserted into the ICS of a dual reporter plasmid upstream of the firefly luciferase gene, luc. LUC expression was taken as a putative indication of internal translation initiation from the studied sequences. Interestingly, all sequences mediated 3' LUC expression. However, northern blot analysis revealed that in addition to the dicistronic mRNAs, transcripts containing only the LUC-encoding sequences were produced from the plasmids. Electroporation studies with in vitro synthesized mRNAs showed that expression from the 3' cistron of the dicistronic mRNAs was below the level of detection. This suggested that the observed LUC expression from yeast transformed with the dicistronic expression plasmids did not originate from dicistronic messages. Deletion of the promoter increased 3' LUC expression. Similarly, repression of transcription prevented 5' cistron expression whereas 3' LUC expression was stimulated. These results suggested that the observed LUC expression did not result from partially degraded or spliced dicistronic RNAs but rather from transcripts synthesized from cryptic promoters. Despite high LUC activity, northern blot analysis detected few transcripts from yeast transformed with the promoterless constructs. Therefore, our data indicate that the functional assay is more revealing than RNA analysis in the case of very sensitive reporter genes generally used in IRES studies. Furthermore, our studies show that there is a clear need for detailed analysis prior to concluding the mechanism of 3' cistron expression.
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Affiliation(s)
- Katri J Mäkeläinen
- Department of Applied Chemistry and Microbiology, Latokartanonkaari 11, P.O. Box 27, University of Helsinki, Helsinki 00014, Finland.
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Paulsen M, Lund C, Akram Z, Winther JR, Horn N, Møller LB. Evidence that translation reinitiation leads to a partially functional Menkes protein containing two copper-binding sites. Am J Hum Genet 2006; 79:214-29. [PMID: 16826513 PMCID: PMC1559486 DOI: 10.1086/505407] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 04/21/2006] [Indexed: 11/04/2022] Open
Abstract
Menkes disease (MD) is an X-linked recessive disorder of copper metabolism. It is caused by mutations in the ATP7A gene encoding a copper-translocating P-type ATPase, which contains six N-terminal copper-binding sites (CBS1-CBS6). Most patients die in early childhood. We investigated the functional effect of a large frameshift deletion in ATP7A (including exons 3 and 4) identified in a patient with MD with unexpectedly mild symptoms and long survival. The mutated transcript, ATP7A(Delta ex3+ex4), contains a premature termination codon after 46 codons. Although such transcripts are generally degraded by nonsense-mediated mRNA decay (NMD), it was established by real-time PCR quantification that the ATP7A(Delta ex3+ex4) transcript was protected from degradation. A combination of in vitro translation, recombinant expression, and immunocytochemical analysis provided evidence that the ATP7A(Delta ex3+ex4) transcript was protected from degradation because of reinitiation of protein translation. Our findings suggest that reinitiation takes place at two downstream internal codons. The putative N-terminally truncated proteins contain only CBS5 and CBS6. Cellular localization and copper-dependent trafficking of the major part of endogenous and recombinant ATP7A(Delta ex3+ex4) proteins were similar to the wild-type ATP7A protein. Furthermore, the ATP7A(Delta ex3+ex4) cDNA was able to rescue a yeast strain lacking the homologous gene, CCC2. In summary, we propose that reinitiation of the NMD-resistant ATP7A(Delta ex3+ex4) transcript leads to the synthesis of N-terminally truncated and at-least-partially functional Menkes proteins missing CBS1-CBS4. This finding--that a mutation that would have been assumed to be null is not--highlights the need to examine the biochemical phenotype of patients to deduce the efficacy of copper therapy.
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Marsden S, Nardelli M, Linder P, McCarthy JEG. Unwinding single RNA molecules using helicases involved in eukaryotic translation initiation. J Mol Biol 2006; 361:327-35. [PMID: 16828800 DOI: 10.1016/j.jmb.2006.06.016] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2006] [Revised: 06/07/2006] [Accepted: 06/09/2006] [Indexed: 02/07/2023]
Abstract
The small (40 S) subunit of the eukaryotic ribosome may have to scan more than 2000 nucleotides (>600 nm) from its 5'cap recruiting point on an mRNA molecule before initiating on a translation start codon. As with many other processes in living cells, including transcription, editing, mRNA splicing, pre-rRNA processing, RNA transport and RNA decay, scanning is facilitated by helicase activity. However, precise quantitative data on the molecular mechanism of scanning, including the roles of helicases, are lacking. Here, we describe a novel atomic force microscopy (AFM)-based procedure to examine the roles of two yeast helicases, eIF4A and Ded1, previously implicated in translation initiation by genetic and biochemical studies. Our results show that eIF4A, especially in the presence of its "cofactor" eIF4B, promotes ATP-dependent unwinding of localised secondary structure in long RNA molecules under tensional loading, albeit only at high protein:RNA ratios. Thus eIF4A can act to separate only a limited number of base-pairs, possibly via a steric unwinding mechanism. In contrast, Ded1 is more effective in reducing (by up to 50 pN at an AFM loading rate of 14 nNs(-1)) the force necessary to disrupt an RNA stem-loop, and thus shows significant kinetic competence to facilitate fast unwinding. These single molecule experiments indicate that Ded1 is likely to act as the more potent unwinding factor on natural mRNA substrates.
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Affiliation(s)
- Steven Marsden
- Manchester Interdisciplinary Biocentre, University of Manchester, 131 Princess Street, Manchester M1 7ND, UK
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Babendure JR, Babendure JL, Ding JH, Tsien RY. Control of mammalian translation by mRNA structure near caps. RNA (NEW YORK, N.Y.) 2006; 12:851-61. [PMID: 16540693 PMCID: PMC1440912 DOI: 10.1261/rna.2309906] [Citation(s) in RCA: 219] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The scanning model of RNA translation proposes that highly stable secondary structures within mRNAs can inhibit translation, while structures of lower thermal stability also affect translation if close enough to the 5' methyl G cap. However, only fragmentary information is available about the dependence of translation efficiency in live mammalian cells on the thermodynamic stability, location, and GC content of RNA structures in the 5'-untranslated region. We devised a two-color fluorescence assay for translation efficiency in single live cells and compared a wide range of hairpins with predicted thermal stabilities ranging from -10 to -50 kcal/mol and 5' G cap-to-hairpin distances of 1-46 bases. Translation efficiency decreased abruptly as hairpin stabilities increased from deltaG = -25 to -35 kcal/mol. Shifting a hairpin as little as nine bases relative to the 5' cap could modulate translation more than 50-fold. Increasing GC content diminished translation efficiency when predicted thermal stability and cap-to-hairpin distances were held constant. We additionally found naturally occurring 5'-untranslated regions affected translation differently in live cells compared with translation in in vitro lysates. Our study will assist scientists in designing experiments that deliberately modulate mammalian translation with designed 5' UTRs.
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Affiliation(s)
- Jeremy R Babendure
- Department of Pharmacology, University of California, San Diego, La Jolla 92093-0647, USA
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Bauer G, Suess B. Engineered riboswitches as novel tools in molecular biology. J Biotechnol 2006; 124:4-11. [PMID: 16442180 DOI: 10.1016/j.jbiotec.2005.12.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Revised: 10/26/2005] [Accepted: 12/01/2005] [Indexed: 10/25/2022]
Abstract
During the last years the great importance of RNA for regulating gene expression in all organisms has become obvious. Consequently, several recent approaches aim to utilize the outstanding chemical properties of RNA to develop artificial RNA regulators for conditional gene expression systems. A combination of rational design, in vitro selection and in vivo screening systems has been used to create a versatile set of RNA based molecular switches. These tools rely on diverse mechanisms and exhibit activity in several organisms. In this review, we summarize recent developments in the application of engineered riboswitches for gene regulation in vivo.
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Affiliation(s)
- Gesine Bauer
- Lehrstuhl für Mikrobiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
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37
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de Las Mercedes Dana M, Pintor-Toro JA. Post-transcriptional control of a glucoamylase gene from Trichoderma harzianum under stress conditions. Mol Microbiol 2005; 57:250-60. [PMID: 15948964 DOI: 10.1111/j.1365-2958.2005.04682.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have examined the regulation of Trichoderma harzianum glucoamylase gene (Gla66) in response to different growth conditions. Transcription of the Gla66 gene is initiated from two different sites, yielding two transcripts of 2.1 kb and 2.6 kb respectively. The 2.1 kb mRNA (ST) encodes for an extracellular glucoamylase of 66 kDa. This protein shows the domains conserved in other fungal glucoamylases: a signal peptide responsible for protein secretion and a catalytic domain, both joined by a linker region. The longest transcript (LT) is untranslated, it contains an unusually extended 5'-untranslated region and is transcribed under stress and growth limiting conditions. The translational control of LT could be defined by the presence of four upstream open reading frames (uORFs) in its 5'-leader sequence. The analysis of these uORFs in a yeast heterologous system shows that two of these uORFs prevent the Gla66 translation under unfavourable growth conditions, when the LT transcript is accumulated.
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Abstract
Great advances have been made in the past three decades in understanding the molecular mechanics underlying protein synthesis in bacteria, but our understanding of the corresponding events in eukaryotic organisms is only beginning to catch up. In this review we describe the current state of our knowledge and ignorance of the molecular mechanics underlying eukaryotic translation. We discuss the mechanisms conserved across the three kingdoms of life as well as the important divergences that have taken place in the pathway.
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Affiliation(s)
- Lee D Kapp
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, USA.
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Berthelot K, Muldoon M, Rajkowitsch L, Hughes J, McCarthy JEG. Dynamics and processivity of 40S ribosome scanning on mRNA in yeast. Mol Microbiol 2004; 51:987-1001. [PMID: 14763975 DOI: 10.1046/j.1365-2958.2003.03898.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The eukaryotic 40S ribosomal subunit locates the translation initiation codon on an mRNA via the so-called scanning process that follows 40S binding to the capped 5' end. This key step in translation is required for the expression of almost all eukaryotic genes, yet the mechanism and dynamics of scanning are unknown. We have performed quantitative studies in vivo and in vitro of the movement of yeast 40S ribosomes along 5' untranslated regions (UTRs) of different lengths. 40S subunits perform cap-dependent scanning with high processivity for more than 1700 nucleotides in cells of Saccharomyces cerevisiae. Moreover, the observed rates of expression indicate that scanning is performed by an untethered 40S subunit that has been released from the 5' cap complex. Unexpectedly, the capability to maintain scanning competence on a long 5' UTR is more dependent on the Ded1/Dbp1 type of helicase than on eIF4A or eIF4B. In a yeast cell-free extract, scanning shows reduced processivity, with an estimated net 5'-->3' rate of approximately 10 nucleotides per second at 26 degrees C. We have developed a biased bidirectional walking model of ribosomal scanning that provides a framework for understanding the above observations as well as other known quantitative and qualitative features of this process.
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Davies WL, Vandenberg JI, Sayeed RA, Trezise AEO. Cardiac Expression of the Cystic Fibrosis Transmembrane Conductance Regulator Involves Novel Exon 1 Usage to Produce a Unique Amino-terminal Protein. J Biol Chem 2004; 279:15877-87. [PMID: 14754881 DOI: 10.1074/jbc.m313628200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a chloride channel present in many cells. In cardiomyocytes, we report that multiple exon 1 usage and alternative splicing produces four CFTR transcripts, with different 5'-untranslated regions, CFTR(TRAD-139), CFTR(-1C/-1A), CFTR(-1C), and CFTR(-1B). CFTR transcripts containing the novel upstream exons (exons -1C, -1B, and -1A) represent more than 90% of cardiac expressed CFTR mRNA. Regulation of cardiac CFTR expression, in response to developmental and pathological stimuli, is exclusively due to the modulation of CFTR(-1C) and CFTR(-1C/-1A) expression. Upstream open reading frames have been identified in the 5'-untranslated regions of all CFTR transcripts that, in conjunction with adjacent stem-loop structures, modulate the efficiency of translation initiation at the AUG codon of the main CFTR coding region in CFTR(TRAD-139) and CFTR(-1C/-1A) transcripts. Exon -1A, only present in CFTR(-1C/-1A) transcripts, encodes an AUG codon that is in-frame with the main CFTR open reading frame, the efficient translation of which produces a novel CFTR protein isoform with a curtailed amino terminus. As the expression of this CFTR transcript parallels the spatial and temporal distribution of the cAMP-activated whole-cell current density in normal and diseased hearts, we suggest that CFTR(-1C/-1A) provides the molecular basis for the cardiac cAMP-activated chloride channel. Our findings provide further insight into the complex nature of in vivo CFTR expression, to which multiple mRNA transcripts, protein isoforms, and post-transcriptional regulatory mechanisms are now added.
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Affiliation(s)
- Wayne L Davies
- School of Biomedical Science, University of Queensland, Brisbane, Queensland 4072, Australia
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Hanson S, Berthelot K, Fink B, McCarthy JEG, Suess B. Tetracycline-aptamer-mediated translational regulation in yeast. Mol Microbiol 2003; 49:1627-37. [PMID: 12950926 DOI: 10.1046/j.1365-2958.2003.03656.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
We describe post-transcriptional gene regulation in yeast based on direct RNA-ligand interaction. Tetracycline-dependent translational regulation could be imposed via specific aptamers inserted at two different positions in the 5' untranslated region (5'UTR). Translation in vivo was suppressed up to ninefold upon addition of tetracycline. Repression via an aptamer located near the start codon (cap-distal) in the 5'UTR was more effective than repression via a cap-proximal position. On the other hand, suppression in a cell-free system reached maximally 50-fold and was most effective via a cap-proximal aptamer. Examination of the kinetics of tetracycline-dependent translational inhibition in vitro revealed that preincubation of tetracycline and mRNA before starting translation led not only to the fastest onset of inhibition but also the most effective repression. The differences between the behaviour of the regulatory system in vivo and in vitro are likely to be related to distinct properties of mRNP structure and mRNA accessibility in intact cells as opposed to cell-extracts. Tetracycline-dependent regulation was also observed after insertion of an uORF sequence upstream of the aptamer, indicating that our system also targets reinitiating ribosomes. Polysomal gradient analyses provided insight into the mechanism of regulation. Cap-proximal insertion inhibits binding of the 43S complex to the cap structure whereas start-codon-proximal aptamers interfere with formation of the 80S ribosome, probably by blocking the scanning preinitiation complex.
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Affiliation(s)
- Shane Hanson
- Lehrstuhl für Mikrobiologie, Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstrasse 5, 91058 Erlangen, Germany
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Melo EO, de Melo Neto OP, Martins de Sá C. Adenosine-rich elements present in the 5'-untranslated region of PABP mRNA can selectively reduce the abundance and translation of CAT mRNAs in vivo. FEBS Lett 2003; 546:329-34. [PMID: 12832063 DOI: 10.1016/s0014-5793(03)00620-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The poly(A)-binding protein (PABP) is a highly conserved eukaryotic protein whose synthesis is regulated at the post-transcriptional level. The binding of PABP to the poly(A)-rich element found in the 5'-untranslated region (5'UTR) of PABP mRNA specifically inhibits its own translation. In this report, we show that similar adenosine-rich elements in the 5'UTR of the chloramphenicol acetyl-transferase (CAT) gene can significantly reduce the reporter mRNA abundance and translation in human 293 cells. The reduction in mRNA level, but not CAT expression, is dependent on the size of the 5'UTR poly(A) element. Furthermore, one 5'UTR-tethered PABP molecule is enough to inhibit CAT expression without affecting its mRNA level. We propose that the control of PABP synthesis may involve mRNA decay and the repression of translation.
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Affiliation(s)
- Eduardo O Melo
- Departamento de Biologia Celular, Universidade de Brasília, Asa Norte, Brasília, DF 70910-900, Brazil.
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Bink HHJ, Schirawski J, Haenni AL, Pleij CWA. The 5'-proximal hairpin of turnip yellow mosaic virus RNA: its role in translation and encapsidation. J Virol 2003; 77:7452-8. [PMID: 12805444 PMCID: PMC164824 DOI: 10.1128/jvi.77.13.7452-7458.2003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The RNA genome of turnip yellow mosaic virus (TYMV) consists of more than 6,000 nucleotides. During a study of the roles of the two hairpins located in its 90-nucleotide 5' untranslated region, it was observed that stabilization of the 5'-proximal hairpin leads to a delay in the development of symptoms on plants. This delay in symptom development for both locally and systemically infected leaves was found to be dependent on a change in the free energy of the hairpin caused by introduced mutations. A protoplast transfection assay revealed that the accumulation of plus-strand full-length RNA and subgenomic RNA, as well as protein expression levels, was affected by hairpin stability. Stabilization of this hairpin inhibited translation. A model is proposed in which a destabilized 5'-proximal hairpin allows maximal translation of the viral proteins. It is suggested that this hairpin may exist in close proximity to the 5' cap as long as its stability is low enough to enable translation. However, at an acidic pH, the hairpin structure becomes more stable and is functionally transformed into the initiation signal for viral packaging. Slightly acidic conditions can be found in chloroplasts, where TYMV assembly is driven by a low pH generated by active photosynthesis.
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Affiliation(s)
- Hugo H J Bink
- Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands
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Janatova I, Costaglioli P, Wesche J, Masson JM, Meilhoc E. Development of a reporter system for the yeast Schwanniomyces occidentalis: influence of DNA composition and codon usage. Yeast 2003; 20:687-701. [PMID: 12794930 DOI: 10.1002/yea.997] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In this paper we report on searching for suitable reporters to monitor gene expression and protein secretion in the amylolytic yeast Schwanniomyces occidentalis. Several potential reporter and marker genes, formerly shown to be functional in other yeasts, were cloned downstream from the homologous invertase gene (INV) promoter and their activity was followed in conditions of repression and derepression of the INV promoter. However, neither beta-glucuronidase nor beta-lactamase nor phleomycin resistance-conferring gene, all originating from E. coli, were expressed in S. occidentalis cells to such a level to allow for monitoring of their activity. All the reporter genes tested have a higher percentage of GC (47-62%) in their DNA compared to the DNA composition of S. occidentalis genes that are more AT-rich (36% GC). The codon usage of all the reporter genes also varies from that of 16 so far sequenced S. occidentalis genes. This suggests that an appropriate composition of DNA and a codon usage similar to S. occidentalis genes might be very important parameters for an efficient expression of a heterologous gene in Schwanniomyces occidentalis. Indeed, two genes originating from Staphylococcus aureus, with an AT-content in their DNA similar to that of S. occidentalis, were functionally expressed in S. occidentalis cells. Both a phleomycin resistance-conferring gene and a chloramphenicol acetyltransferase-encoding gene thus represent suitable reporters of gene expression and protein secretion in S. occidentalis. Additionally, we show in this work that the transcription-regulating region and the signal peptide sequence of the S. occidentalis invertase gene were efficient to direct gene expression and subsequent protein secretion in Saccharomyces cerevisiae.
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Affiliation(s)
- Ivana Janatova
- Laboratory of Cell Reproduction, Institute of Microbiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
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Chartrand P, Meng XH, Huttelmaier S, Donato D, Singer RH. Asymmetric sorting of ash1p in yeast results from inhibition of translation by localization elements in the mRNA. Mol Cell 2002; 10:1319-30. [PMID: 12504008 DOI: 10.1016/s1097-2765(02)00694-9] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
ASH1 mRNA localizes at the bud tip of late-anaphase yeast, resulting in accumulation of Ash1p in the daughter nucleus. We show that disruption of the secondary structure, but not the protein coding, of all four ASH1 localization elements resulted in RNA and protein delocalization. Localization of both was incrementally restored by replacement of each of the four elements. However, transposition of the elements to the 3'UTR reinstated the RNA, but not the protein, localization. Interestingly, the mutant ASH1 mRNA was translated more efficiently, suggesting that asymmetry of Ash1p resulted from translational inhibition by the localization elements. In support of this, Ash1p asymmetry could be rescued by slowing its translation.
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Affiliation(s)
- Pascal Chartrand
- Department of Anatomy and Structural Biology, Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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46
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de la Cruz BJ, Prieto S, Scheffler IE. The role of the 5' untranslated region (UTR) in glucose-dependent mRNA decay. Yeast 2002; 19:887-902. [PMID: 12112242 DOI: 10.1002/yea.884] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
When S. cerevisiae are grown with glucose, SDH2 mRNA encoding the iron protein of the succinate dehydrogenase complex is unstable and present at low level. In yeast grown without glucose, SDH2 mRNA is stable and its level rises. Addition of glucose to a glucose-limited culture causes the SDH2 mRNA level to fall rapidly with a half-life of approximately 5-7 min. Previously the 5'UTR of the mRNA of SDH2 was shown to be necessary and sufficient to destabilize it in glucose (Lombardo et al., 1992). We now show that the SDH1 and SUC2 5'UTRs are capable of conferring glucose-sensitive mRNA instability. We also examine how changes in the SDH2 5'UTR affect glucose-triggered degradation. Finally, we show that changes in mRNA stability are correlated with changes in translational efficiency for these transcripts.
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Affiliation(s)
- Bernard J de la Cruz
- Department of Biology, University of California, San Diego, La Jolla, CA 92093-0322, USA.
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47
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Ramirez CV, Vilela C, Berthelot K, McCarthy JEG. Modulation of eukaryotic mRNA stability via the cap-binding translation complex eIF4F. J Mol Biol 2002; 318:951-62. [PMID: 12054793 DOI: 10.1016/s0022-2836(02)00162-6] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Decapping by Dcp1 in Saccharomyces cerevisiae is a key step in mRNA degradation. However, the cap also binds the eukaryotic initiation factor (eIF) complex 4F and its associated proteins. Characterisation of the relationship between decapping and interactions involving eIF4F is an essential step towards understanding polysome disassembly and mRNA decay. Three types of observation suggest how changes in the functional status of eIF4F modulate mRNA stability in vivo. First, partial disruption of the interaction between eIF4E and eIF4G, caused by mutations in eIF4E or the presence of the yeast 4E-binding protein p20, stabilised mRNAs. The interactions of eIF4G and p20 with eIF4E may therefore act to modulate the decapping process. Since we also show that the in vitro decapping rate is not directly affected by the nature of the body of the mRNA, this suggests that changes in eIF4F structure could play a role in triggering decapping during mRNA decay. Second, these effects were seen in the absence of extreme changes in global translation rates in the cell, and are therefore relevant to normal mRNA turnover. Third, a truncated form of eIF4E (Delta196) had a reduced capacity to inhibit Dcp1-mediated decapping in vitro, yet did not change cellular mRNA half-lives. Thus, the accessibility of the cap to Dcp1 in vivo is not simply controlled by competition with eIF4E, but is subject to switching between molecular states with different levels of access.
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Affiliation(s)
- Carmen Velasco Ramirez
- Posttranscriptional Control Group, Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology (UMIST), P.O. Box 88, M60 1QD, UK
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48
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Basnakian AG, Singh AB, Shah SV. Identification and expression of deoxyribonuclease (DNase) I alternative transcripts in the rat. Gene 2002; 289:87-96. [PMID: 12036587 DOI: 10.1016/s0378-1119(02)00479-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Deoxyribonuclease (DNase) I has been implicated in the induction of DNA fragmentation and cell death, however little is known about its regulation in vivo. In the present study, we describe that DNase I messenger RNA (mRNA) is alternatively spliced in rat kidney, and the activity of the DNase I correlates with the alternative splicing during the course of renal ischemia/reperfusion. Northern blot analysis with mRNA from control rat kidneys and kidneys subjected to ischemia/reperfusion in vivo yielded two bands of approximately 1.3 and 1.5 kb, suggesting the possibility of alternative splicing. However, prolonged reperfusion up to 16 h resulted in the predominant expression of 1.3 kb transcript. The disappearance of the 1.5 kDa band was associated with the increased DNase I activity in the kidney during ischemia/reperfusion. To study the alternative splicing of the DNase I mRNA, rat kidney cortex DNA complementary to RNA library was screened using rat DNase I probe. Twenty-one positive clones were obtained and were compared with the reported DNase I mRNA transcript cloned from rat parotid gland. All clones showed 100% homology with the reported DNase I coding sequence and part of 5'-untranslated region (5'-UTR), named exon 1a by us. Twelve out of 21 isolated clones had longer 5'-UTR than previously described, and DNase I pre-mRNA was alternatively spliced in this region. Six out of these 12 clones contained extra up to 153 bp in extreme 5' end, whereas, in six other clones, an internal 132 bp segment (exon 1b) of this additional sequence was absent, and only the extreme 5'UTR sequence (exon 1c) was found in these clones. The nucleotide analysis showed that alternating exon 1b has the possibility of a secondary structure with high internal homology and potential for at least one major stable stem-loop. Both newly identified segments, exons 1b and 1c, were also identified in genomic DNA. The long splice variant, containing exon 1b, is expressed only in the kidney among different tissues tested. Exon 1b inhibited translational activity of DNase I mRNA in vitro. Our data suggest that alternative splicing in 5'-UTR in the kidney may provide a prompt DNA-independent regulation of DNase I activity when DNA is damaged during ischemic injury.
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MESH Headings
- Alternative Splicing
- Animals
- Base Sequence
- Cloning, Molecular
- DNA/chemistry
- DNA/genetics
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Deoxyribonuclease I/genetics
- Exons/genetics
- Gene Expression Regulation, Enzymologic
- Kidney/blood supply
- Kidney/enzymology
- Kidney/metabolism
- Male
- Molecular Sequence Data
- Nucleic Acid Conformation
- Protein Biosynthesis
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Reperfusion Injury/physiopathology
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Nucleic Acid
- Transcription, Genetic
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Affiliation(s)
- Alexei G Basnakian
- Department of Internal Medicine, Division of Nephrology, University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot 501, Little Rock, AR 72205, USA.
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Rüegsegger U, Leber JH, Walter P. Block of HAC1 mRNA translation by long-range base pairing is released by cytoplasmic splicing upon induction of the unfolded protein response. Cell 2001; 107:103-14. [PMID: 11595189 DOI: 10.1016/s0092-8674(01)00505-0] [Citation(s) in RCA: 236] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Expression of the yeast transcription factor Hac1p, which controls the unfolded protein response, is regulated posttranscriptionally. Hac1p is only produced when an intron at the 3' end of its mRNA is removed by a nonconventional, regulated splicing reaction. We show that a previously unrecognized base-pairing interaction between the intron and the 5' untranslated region is required and sufficient to block mRNA translation. Unspliced HAC1 mRNA is stable, located in the cytosol, and is associated with polyribosomes, yet does not produce protein, indicating that the ribosomes engaged on the mRNA are stalled. We show that the polysomal, cytoplasmic pool of HAC1 mRNA is a substrate for splicing, suggesting that the stalled ribosomes may resume translation after the intron is removed.
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Affiliation(s)
- U Rüegsegger
- Howard Hughes Medical Institute, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA
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Ferreira PC, Ness F, Edwards SR, Cox BS, Tuite MF. The elimination of the yeast [PSI+] prion by guanidine hydrochloride is the result of Hsp104 inactivation. Mol Microbiol 2001; 40:1357-69. [PMID: 11442834 DOI: 10.1046/j.1365-2958.2001.02478.x] [Citation(s) in RCA: 212] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the yeast Saccharomyces cerevisiae, Sup35p (eRF3), a subunit of the translation termination complex, can take up a prion-like, self-propagating conformation giving rise to the non-Mendelian [PSI+] determinant. The replication of [PSI+] prion seeds can be readily blocked by growth in the presence of low concentrations of guanidine hydrochloride (GdnHCl), leading to the generation of prion-free [psi-] cells. Here, we provide evidence that GdnHCl blocks seed replication in vivo by inactivation of the molecular chaperone Hsp104. Although growth in the presence of GdnHCl causes a modest increase in HSP104 expression (20-90%), this is not sufficient to explain prion curing. Rather, we show that GdnHCl inhibits two different Hsp104-dependent cellular processes, namely the acquisition of thermotolerance and the refolding of thermally denatured luciferase. The inhibitory effects of GdnHCl protein refolding are partially suppressed by elevating the endogenous cellular levels of Hsp104 using a constitutive promoter. The kinetics of GdnHCl-induced [PSI+] curing could be mimicked by co-expression of an ATPase-negative dominant HSP104 mutant in an otherwise wild-type [PSI+] strain. We suggest that GdnHCl inactivates the ATPase activity of Hsp104, leading to a block in the replication of [PSI+] seeds.
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Affiliation(s)
- P C Ferreira
- Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
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