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Moran JC, Brivanlou A, Brischigliaro M, Fontanesi F, Rouskin S, Barrientos A. The human mitochondrial mRNA structurome reveals mechanisms of gene expression. Science 2024; 385:eadm9238. [PMID: 39024447 DOI: 10.1126/science.adm9238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 05/24/2024] [Indexed: 07/20/2024]
Abstract
The human mitochondrial genome encodes crucial oxidative phosphorylation system proteins, pivotal for aerobic energy transduction. They are translated from nine monocistronic and two bicistronic transcripts whose native structures remain unexplored, posing a gap in understanding mitochondrial gene expression. In this work, we devised the mitochondrial dimethyl sulfate mutational profiling with sequencing (mitoDMS-MaPseq) method and applied detection of RNA folding ensembles using expectation-maximization (DREEM) clustering to unravel the native mitochondrial messenger RNA (mt-mRNA) structurome in wild-type (WT) and leucine-rich pentatricopeptide repeat-containing protein (LRPPRC)-deficient cells. Our findings elucidate LRPPRC's role as a holdase contributing to maintaining mt-mRNA folding and efficient translation. mt-mRNA structural insights in WT mitochondria, coupled with metabolic labeling, unveil potential mRNA-programmed translational pausing and a distinct programmed ribosomal frameshifting mechanism. Our data define a critical layer of mitochondrial gene expression regulation. These mt-mRNA folding maps provide a reference for studying mt-mRNA structures in diverse physiological and pathological contexts.
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Affiliation(s)
- J Conor Moran
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA
- University of Miami Medical Scientist Training Program, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA
| | - Amir Brivanlou
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Michele Brischigliaro
- Department of Neurology, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA
| | - Flavia Fontanesi
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA
| | - Silvi Rouskin
- Department of Microbiology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA
| | - Antoni Barrientos
- Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA
- Department of Neurology, University of Miami Miller School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA
- The Miami Veterans Affairs (VA) Medical System, 1201 NW 16th Street, Miami, FL 33125, USA
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2
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Hughes LA, Rackham O, Filipovska A. Illuminating mitochondrial translation through mouse models. Hum Mol Genet 2024; 33:R61-R79. [PMID: 38779771 PMCID: PMC11112386 DOI: 10.1093/hmg/ddae020] [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: 11/10/2023] [Revised: 01/22/2024] [Accepted: 01/31/2024] [Indexed: 05/25/2024] Open
Abstract
Mitochondria are hubs of metabolic activity with a major role in ATP conversion by oxidative phosphorylation (OXPHOS). The mammalian mitochondrial genome encodes 11 mRNAs encoding 13 OXPHOS proteins along with 2 rRNAs and 22 tRNAs, that facilitate their translation on mitoribosomes. Maintaining the internal production of core OXPHOS subunits requires modulation of the mitochondrial capacity to match the cellular requirements and correct insertion of particularly hydrophobic proteins into the inner mitochondrial membrane. The mitochondrial translation system is essential for energy production and defects result in severe, phenotypically diverse diseases, including mitochondrial diseases that typically affect postmitotic tissues with high metabolic demands. Understanding the complex mechanisms that underlie the pathologies of diseases involving impaired mitochondrial translation is key to tailoring specific treatments and effectively targeting the affected organs. Disease mutations have provided a fundamental, yet limited, understanding of mitochondrial protein synthesis, since effective modification of the mitochondrial genome has proven challenging. However, advances in next generation sequencing, cryoelectron microscopy, and multi-omic technologies have revealed unexpected and unusual features of the mitochondrial protein synthesis machinery in the last decade. Genome editing tools have generated unique models that have accelerated our mechanistic understanding of mitochondrial translation and its physiological importance. Here we review the most recent mouse models of disease pathogenesis caused by defects in mitochondrial protein synthesis and discuss their value for preclinical research and therapeutic development.
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Affiliation(s)
- Laetitia A Hughes
- Telethon Kids Institute, Northern Entrance, Perth Children’s Hospital, 15 Hospital Avenue, Nedlands, WA 6009, Australia
- Harry Perkins Institute of Medical Research, 6 Verdun Street, Nedlands, WA 6009, Australia
- ARC Centre of Excellence in Synthetic Biology, 35 Stirling Highway, Crawley, WA 6009, The University of Western Australia, Crawley, WA 6009, Australia
| | - Oliver Rackham
- Telethon Kids Institute, Northern Entrance, Perth Children’s Hospital, 15 Hospital Avenue, Nedlands, WA 6009, Australia
- Harry Perkins Institute of Medical Research, 6 Verdun Street, Nedlands, WA 6009, Australia
- ARC Centre of Excellence in Synthetic Biology, 35 Stirling Highway, Crawley, WA 6009, The University of Western Australia, Crawley, WA 6009, Australia
- Curtin Medical School, Curtin University, Kent Street, Bentley, WA 6102, Australia
- Curtin Health Innovation Research Institute, Curtin University, Kent Street, Bentley, WA 6102, Australia
| | - Aleksandra Filipovska
- Telethon Kids Institute, Northern Entrance, Perth Children’s Hospital, 15 Hospital Avenue, Nedlands, WA 6009, Australia
- ARC Centre of Excellence in Synthetic Biology, 35 Stirling Highway, Crawley, WA 6009, The University of Western Australia, Crawley, WA 6009, Australia
- Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, 19 Innovation Walk, Clayton, Clayton, VIC 3168, Australia
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3
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McShane E, Couvillion M, Ietswaart R, Prakash G, Smalec BM, Soto I, Baxter-Koenigs AR, Choquet K, Churchman LS. A kinetic dichotomy between mitochondrial and nuclear gene expression processes. Mol Cell 2024; 84:1541-1555.e11. [PMID: 38503286 PMCID: PMC11236289 DOI: 10.1016/j.molcel.2024.02.028] [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: 09/05/2023] [Revised: 12/12/2023] [Accepted: 02/27/2024] [Indexed: 03/21/2024]
Abstract
Oxidative phosphorylation (OXPHOS) complexes, encoded by both mitochondrial and nuclear DNA, are essential producers of cellular ATP, but how nuclear and mitochondrial gene expression steps are coordinated to achieve balanced OXPHOS subunit biogenesis remains unresolved. Here, we present a parallel quantitative analysis of the human nuclear and mitochondrial messenger RNA (mt-mRNA) life cycles, including transcript production, processing, ribosome association, and degradation. The kinetic rates of nearly every stage of gene expression differed starkly across compartments. Compared with nuclear mRNAs, mt-mRNAs were produced 1,100-fold more, degraded 7-fold faster, and accumulated to 160-fold higher levels. Quantitative modeling and depletion of mitochondrial factors LRPPRC and FASTKD5 identified critical points of mitochondrial regulatory control, revealing that the mitonuclear expression disparities intrinsically arise from the highly polycistronic nature of human mitochondrial pre-mRNA. We propose that resolving these differences requires a 100-fold slower mitochondrial translation rate, illuminating the mitoribosome as a nexus of mitonuclear co-regulation.
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Affiliation(s)
- Erik McShane
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Mary Couvillion
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Robert Ietswaart
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Gyan Prakash
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Brendan M Smalec
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Iliana Soto
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Autum R Baxter-Koenigs
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Karine Choquet
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - L Stirling Churchman
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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4
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Baleva MV, Piunova U, Chicherin I, Vasilev R, Levitskii S, Kamenski P. Mitochondrial Protein SLIRP Affects Biosynthesis of Cytochrome c Oxidase Subunits in HEK293T Cells. Int J Mol Sci 2023; 25:93. [PMID: 38203264 PMCID: PMC10779364 DOI: 10.3390/ijms25010093] [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: 11/18/2023] [Revised: 12/16/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
Mitochondria carry out various vital roles in eukaryotic cells, including ATP energy synthesis, the regulation of apoptosis, Fe-S cluster formation, and the metabolism of fatty acids, amino acids, and nucleotides. Throughout evolution, mitochondria lost most of their ancestor's genome but kept the replication, transcription, and translation machinery. Protein biosynthesis in mitochondria is specialized in the production of highly hydrophobic proteins encoded by mitochondria. These proteins are components of oxidative phosphorylation chain complexes. The coordination of protein synthesis must be precise to ensure the correct assembly of nuclear-encoded subunits for these complexes. However, the regulatory mechanisms of mitochondrial translation in human cells are not yet fully understood. In this study, we examined the contribution of the SLIRP protein in regulating protein biosynthesis in mitochondria. Using a click-chemistry approach, we discovered that deletion of the SLIRP gene disturbs mitochondrial translation, leading to the dysfunction of complexes I and IV, but it has no significant effect on complexes III and V. We have shown that this protein interacts only with the small subunit of the mitochondrial ribosome, which may indicate its involvement in the regulation of the mitochondrial translation initiation stage.
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Affiliation(s)
| | | | | | | | - Sergey Levitskii
- Faculty of Biology, Lomonosov Moscow State University, 1/12 Leninskie Gory, 119234 Moscow, Russia; (M.V.B.); (U.P.); (I.C.); (R.V.)
| | - Piotr Kamenski
- Faculty of Biology, Lomonosov Moscow State University, 1/12 Leninskie Gory, 119234 Moscow, Russia; (M.V.B.); (U.P.); (I.C.); (R.V.)
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Conor Moran J, Brivanlou A, Brischigliaro M, Fontanesi F, Rouskin S, Barrientos A. The human mitochondrial mRNA structurome reveals mechanisms of gene expression. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.31.564750. [PMID: 37961485 PMCID: PMC10635011 DOI: 10.1101/2023.10.31.564750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The mammalian mitochondrial genome encodes thirteen oxidative phosphorylation system proteins, crucial in aerobic energy transduction. These proteins are translated from 9 monocistronic and 2 bicistronic transcripts, whose native structures remain unexplored, leaving fundamental molecular determinants of mitochondrial gene expression unknown. To address this gap, we developed a mitoDMS-MaPseq approach and used DREEM clustering to resolve the native human mitochondrial mt-mRNA structurome. We gained insights into mt-mRNA biology and translation regulatory mechanisms, including a unique programmed ribosomal frameshifting for the ATP8/ATP6 transcript. Furthermore, absence of the mt-mRNA maintenance factor LRPPRC led to a mitochondrial transcriptome structured differently, with specific mRNA regions exhibiting increased or decreased structuredness. This highlights the role of LRPPRC in maintaining mRNA folding to promote mt-mRNA stabilization and efficient translation. In conclusion, our mt-mRNA folding maps reveal novel mitochondrial gene expression mechanisms, serving as a detailed reference and tool for studying them in different physiological and pathological contexts.
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Remes C, Khawaja A, Pearce SF, Dinan AM, Gopalakrishna S, Cipullo M, Kyriakidis V, Zhang J, Dopico XC, Yukhnovets O, Atanassov I, Firth AE, Cooperman B, Rorbach J. Translation initiation of leaderless and polycistronic transcripts in mammalian mitochondria. Nucleic Acids Res 2023; 51:891-907. [PMID: 36629253 PMCID: PMC9881170 DOI: 10.1093/nar/gkac1233] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 11/11/2022] [Accepted: 12/09/2022] [Indexed: 01/12/2023] Open
Abstract
The synthesis of mitochondrial OXPHOS complexes is central to cellular metabolism, yet many molecular details of mitochondrial translation remain elusive. It has been commonly held view that translation initiation in human mitochondria proceeded in a manner similar to bacterial systems, with the mitoribosomal small subunit bound to the initiation factors, mtIF2 and mtIF3, along with initiator tRNA and an mRNA. However, unlike in bacteria, most human mitochondrial mRNAs lack 5' leader sequences that can mediate small subunit binding, raising the question of how leaderless mRNAs are recognized by mitoribosomes. By using novel in vitro mitochondrial translation initiation assays, alongside biochemical and genetic characterization of cellular knockouts of mitochondrial translation factors, we describe unique features of translation initiation in human mitochondria. We show that in vitro, leaderless mRNA transcripts can be loaded directly onto assembled 55S mitoribosomes, but not onto the mitoribosomal small subunit (28S), in a manner that requires initiator fMet-tRNAMet binding. In addition, we demonstrate that in human cells and in vitro, mtIF3 activity is not required for translation of leaderless mitochondrial transcripts but is essential for translation of ATP6 in the case of the bicistronic ATP8/ATP6 transcript. Furthermore, we show that mtIF2 is indispensable for mitochondrial protein synthesis. Our results demonstrate an important evolutionary divergence of the mitochondrial translation system and further our fundamental understanding of a process central to eukaryotic metabolism.
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Affiliation(s)
- Cristina Remes
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anas Khawaja
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Sarah F Pearce
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Adam M Dinan
- Department of Pathology, University of Cambridge, Cambridge, UK
| | - Shreekara Gopalakrishna
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Miriam Cipullo
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Vasileios Kyriakidis
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Jingdian Zhang
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Xaquin Castro Dopico
- Department of Microbiology, Tumor & Cell Biology, Karolinska Institutet, Stockholm 171 77, Sweden
| | - Olessya Yukhnovets
- RWTH Aachen, I. Physikalisches Institut (IA), Aachen, Germany
- Forschungszentrum Jülich, Institute of Complex Systems ICS-5, Jülich, Germany
| | - Ilian Atanassov
- Proteomics Core Facility, Max-Planck-Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, 50931 Cologne, Germany
| | - Andrew E Firth
- Department of Pathology, University of Cambridge, Cambridge, UK
| | - Barry Cooperman
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Joanna Rorbach
- Department of Medical Biochemistry and Biophysics, Division of Molecular Metabolism, Karolinska Institutet, Stockholm 17165, Sweden
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
- STIAS: Stellenbosch Institute for Advanced Study at Stellenbosch University, Marais Rd, Stellenbosch 7600, South Africa
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7
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Chrzanowska-Lightowlers ZM, Lightowlers RN. Translation in Mitochondrial Ribosomes. Methods Mol Biol 2023; 2661:53-72. [PMID: 37166631 DOI: 10.1007/978-1-0716-3171-3_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Mitochondrial protein synthesis is essential for the life of aerobic eukaryotes. Without it, oxidative phosphorylation cannot be coupled. Evolution has shaped a battery of factors and machinery that are key to production of just a handful of critical proteins. In this general concept chapter, we attempt to briefly summarize our current knowledge of the overall process in mitochondria from a variety of species, breaking this down to the four parts of translation: initiation, elongation, termination, and recycling. Where appropriate, we highlight differences between species and emphasize gaps in our understanding. Excitingly, with the current revolution in cryoelectron microscopy and mitochondrial genome editing, it is highly likely that many of these gaps will be resolved in the near future. However, the absence of a faithful in vitro reconstituted system to study mitochondrial translation is still problematic.
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Affiliation(s)
- Zofia M Chrzanowska-Lightowlers
- Wellcome Centre for Mitochondrial Research, Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle upon Tyne, UK.
| | - Robert N Lightowlers
- Wellcome Centre for Mitochondrial Research, Newcastle University Biosciences Institute, Faculty of Medical Sciences, Newcastle upon Tyne, UK
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8
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Soto I, Couvillion M, Hansen KG, McShane E, Moran JC, Barrientos A, Churchman LS. Balanced mitochondrial and cytosolic translatomes underlie the biogenesis of human respiratory complexes. Genome Biol 2022; 23:170. [PMID: 35945592 PMCID: PMC9361522 DOI: 10.1186/s13059-022-02732-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Accepted: 07/18/2022] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Oxidative phosphorylation (OXPHOS) complexes consist of nuclear and mitochondrial DNA-encoded subunits. Their biogenesis requires cross-compartment gene regulation to mitigate the accumulation of disproportionate subunits. To determine how human cells coordinate mitochondrial and nuclear gene expression processes, we tailored ribosome profiling for the unique features of the human mitoribosome. RESULTS We resolve features of mitochondrial translation initiation and identify a small ORF in the 3' UTR of MT-ND5. Analysis of ribosome footprints in five cell types reveals that average mitochondrial synthesis levels correspond precisely to cytosolic levels across OXPHOS complexes, and these average rates reflect the relative abundances of the complexes. Balanced mitochondrial and cytosolic synthesis does not rely on rapid feedback between the two translation systems, and imbalance caused by mitochondrial translation deficiency is associated with the induction of proteotoxicity pathways. CONCLUSIONS Based on our findings, we propose that human OXPHOS complexes are synthesized proportionally to each other, with mitonuclear balance relying on the regulation of OXPHOS subunit translation across cellular compartments, which may represent a proteostasis vulnerability.
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Affiliation(s)
- Iliana Soto
- Blavatnik Institute, Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA
| | - Mary Couvillion
- Blavatnik Institute, Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA
| | - Katja G Hansen
- Blavatnik Institute, Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA
| | - Erik McShane
- Blavatnik Institute, Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA
| | - J Conor Moran
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Antoni Barrientos
- Department of Neurology, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - L Stirling Churchman
- Blavatnik Institute, Department of Genetics, Harvard Medical School, Boston, MA, 02115, USA.
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9
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Bharmal MHM, Gega A, Schrader JM. A combination of mRNA features influence the efficiency of leaderless mRNA translation initiation. NAR Genom Bioinform 2021; 3:lqab081. [PMID: 34568822 PMCID: PMC8459731 DOI: 10.1093/nargab/lqab081] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 08/03/2021] [Accepted: 08/27/2021] [Indexed: 12/30/2022] Open
Abstract
Bacterial translation is thought to initiate by base pairing of the 16S rRNA and the Shine-Dalgarno sequence in the mRNA's 5' untranslated region (UTR). However, transcriptomics has revealed that leaderless mRNAs, which completely lack any 5' UTR, are broadly distributed across bacteria and can initiate translation in the absence of the Shine-Dalgarno sequence. To investigate the mechanism of leaderless mRNA translation initiation, synthetic in vivo translation reporters were designed that systematically tested the effects of start codon accessibility, leader length, and start codon identity on leaderless mRNA translation initiation. Using these data, a simple computational model was built based on the combinatorial relationship of these mRNA features that can accurately classify leaderless mRNAs and predict the translation initiation efficiency of leaderless mRNAs. Thus, start codon accessibility, leader length, and start codon identity combine to define leaderless mRNA translation initiation in bacteria.
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Affiliation(s)
| | - Alisa Gega
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
| | - Jared M Schrader
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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10
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Baleva MV, Piunova UE, Chicherin IV, Krasavina DG, Levitskii SA, Kamenski PA. Yeast Translational Activator Mss51p and Human ZMYND17 - Two Proteins with a Common Origin, but Different Functions. BIOCHEMISTRY. BIOKHIMIIA 2021; 86:1151-1161. [PMID: 34565318 DOI: 10.1134/s0006297921090108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/19/2021] [Accepted: 07/19/2021] [Indexed: 11/23/2022]
Abstract
Despite its similarity to protein biosynthesis in bacteria, translation in the mitochondria of modern eukaryotes has several unique features, such as the necessity for coordination of translation of mitochondrial mRNAs encoding proteins of the electron transport chain complexes with translation of other protein components of these complexes in the cytosol. In the mitochondria of baker's yeast Saccharomyces cerevisiae, this coordination is carried out by a system of translational activators that predominantly interact with the 5'-untranslated regions of mitochondrial mRNAs. No such system has been found in human mitochondria, except a single identified translational activator, TACO1. Here, we studied the role of the ZMYND17 gene, an ortholog of the yeast gene for the translational activator Mss51p, on the mitochondrial translation in human cells. Deletion of the ZMYND17 gene did not affect translation in the mitochondria, but led to the decrease in the cytochrome c oxidase activity and increase in the amount of free F1 subunit of ATP synthase. We also investigated the evolutionary history of Mss51p and ZMYND17 and suggested a possible mechanism for the divergence of functions of these orthologous proteins.
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Affiliation(s)
- Maria V Baleva
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Uliyana E Piunova
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Ivan V Chicherin
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Darya G Krasavina
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Sergey A Levitskii
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia.
| | - Piotr A Kamenski
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
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11
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Friedlander JE, Shen N, Zeng A, Korm S, Feng H. Failure to Guard: Mitochondrial Protein Quality Control in Cancer. Int J Mol Sci 2021; 22:ijms22158306. [PMID: 34361072 PMCID: PMC8348654 DOI: 10.3390/ijms22158306] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 07/20/2021] [Accepted: 07/27/2021] [Indexed: 02/07/2023] Open
Abstract
Mitochondria are energetic and dynamic organelles with a crucial role in bioenergetics, metabolism, and signaling. Mitochondrial proteins, encoded by both nuclear and mitochondrial DNA, must be properly regulated to ensure proteostasis. Mitochondrial protein quality control (MPQC) serves as a critical surveillance system, employing different pathways and regulators as cellular guardians to ensure mitochondrial protein quality and quantity. In this review, we describe key pathways and players in MPQC, such as mitochondrial protein translocation-associated degradation, mitochondrial stress responses, chaperones, and proteases, and how they work together to safeguard mitochondrial health and integrity. Deregulated MPQC leads to proteotoxicity and dysfunctional mitochondria, which contributes to numerous human diseases, including cancer. We discuss how alterations in MPQC components are linked to tumorigenesis, whether they act as drivers, suppressors, or both. Finally, we summarize recent advances that seek to target these alterations for the development of anti-cancer drugs.
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Affiliation(s)
- Joseph E. Friedlander
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; (J.E.F.); (N.S.); (A.Z.); (S.K.)
| | - Ning Shen
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; (J.E.F.); (N.S.); (A.Z.); (S.K.)
- Department of Medicine, Section of Hematology and Medical Oncology, Boston University School of Medicine, Boston, MA 02118, USA
| | - Aozhuo Zeng
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; (J.E.F.); (N.S.); (A.Z.); (S.K.)
| | - Sovannarith Korm
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; (J.E.F.); (N.S.); (A.Z.); (S.K.)
| | - Hui Feng
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA; (J.E.F.); (N.S.); (A.Z.); (S.K.)
- Department of Medicine, Section of Hematology and Medical Oncology, Boston University School of Medicine, Boston, MA 02118, USA
- Correspondence: ; Tel.: +1-617-358-4688; Fax: +1-617-358-1599
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12
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Landwehr V, Milanov M, Angebauer L, Hong J, Jüngert G, Hiersemenzel A, Siebler A, Schmit F, Öztürk Y, Dannenmaier S, Drepper F, Warscheid B, Koch HG. The Universally Conserved ATPase YchF Regulates Translation of Leaderless mRNA in Response to Stress Conditions. Front Mol Biosci 2021; 8:643696. [PMID: 34026826 PMCID: PMC8138138 DOI: 10.3389/fmolb.2021.643696] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 04/13/2021] [Indexed: 12/14/2022] Open
Abstract
The universally conserved P-loop GTPases control diverse cellular processes, like signal transduction, ribosome assembly, cell motility, and intracellular transport and translation. YchF belongs to the Obg-family of P-loop GTPases and is one of the least characterized member of this family. It is unique because it preferentially hydrolyses ATP rather than GTP, but its physiological role is largely unknown. Studies in different organisms including humans suggest a possible role of YchF in regulating the cellular adaptation to stress conditions. In the current study, we explored the role of YchF in the model organism Escherichia coli. By western blot and promoter fusion experiments, we demonstrate that YchF levels decrease during stress conditions or when cells enter stationary phase. The decline in YchF levels trigger increased stress resistance and cells lacking YchF are resistant to multiple stress conditions, like oxidative stress, replication stress, or translational stress. By in vivo site directed cross-linking we demonstrate that YchF interacts with the translation initiation factor 3 (IF3) and with multiple ribosomal proteins at the surface of the small ribosomal subunit. The absence of YchF enhances the anti-association activity of IF3, stimulates the translation of leaderless mRNAs, and increases the resistance against the endoribonuclease MazF, which generates leaderless mRNAs during stress conditions. In summary, our data identify YchF as a stress-responsive regulator of leaderless mRNA translation.
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Affiliation(s)
- Victoria Landwehr
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Martin Milanov
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Larissa Angebauer
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Jiang Hong
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Gabriela Jüngert
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Anna Hiersemenzel
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Ariane Siebler
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Fränk Schmit
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Yavuz Öztürk
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Stefan Dannenmaier
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Friedel Drepper
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Bettina Warscheid
- Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Signalling Research Centers BIOSS and CIBSS, University Freiburg, Freiburg, Germany
| | - Hans-Georg Koch
- Institute for Biochemistry and Molecular Biology, Zentrum für Biochemie und Molekulare Medizin, Faculty of Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Spemann Graduate School of Biology and Medicine, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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13
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Gonçalves AM, Pereira-Santos AR, Esteves AR, Cardoso SM, Empadinhas N. The Mitochondrial Ribosome: A World of Opportunities for Mitochondrial Dysfunction Toward Parkinson's Disease. Antioxid Redox Signal 2021; 34:694-711. [PMID: 32098485 DOI: 10.1089/ars.2019.7997] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Significance: Mitochondrial ribosomes (mitoribosomes) are organelles that translate mitochondrial messenger RNA in the matrix and, in mammals, have evolved to translate 13 polypeptides of the pathway that performs oxidative phosphorylation (OXPHOS). Although a number of devastating diseases result from defects in this mitochondrial translation apparatus, most are associated with genetic mutations and little is known about allelopathic defects caused by antibiotics, toxins, or nonproteinogenic amino acids. Recent Advances: The levels of mitochondrial ribosomal subunits 12S and 16S ribosomal RNA (rRNA) in cells/tissues from patients carrying mutations in these genes have been associated with alterations in mitochondrial translation efficiency and with impaired OXPHOS activities, as well as with the severity of clinical phenotypes. In recent decades, important studies revealed a prominent role of mitochondrial dysfunction in Parkinson's disease (PD); however, the involvement of mitoribosomes remains largely unknown. Critical Issues: Considering that mitoribosomal structure and function can determine the efficiency of OXPHOS and that an impaired mitochondrial respiratory chain is a common finding in PD, we argue that the mitoribosome may be key to disease onset and progression. With this review, we comprehensively integrate the available knowledge on the composition, assembly, and role of the mitoribosome in mitochondrial efficiency, reflecting on its possible involvement in the etiopathogenesis of this epidemic disease as an appealing research avenue. Future Directions: If a direct correlation between mitoribosome failure and PD pathology is demonstrated, these mitochondrial organelles will provide valuable early clinical markers and potentially attractive targets for the development of innovative PD-directed therapeutic agents.
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Affiliation(s)
- Ana Mafalda Gonçalves
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,CIBB-Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Ana Raquel Pereira-Santos
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,CIBB-Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal
| | - Ana Raquel Esteves
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,CIBB-Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal
| | - Sandra M Cardoso
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,CIBB-Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Nuno Empadinhas
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,CIBB-Centre for Innovative Biomedicine and Biotechnology, University of Coimbra, Coimbra, Portugal.,IIIUC-Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
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14
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Mechanisms and regulation of protein synthesis in mitochondria. Nat Rev Mol Cell Biol 2021; 22:307-325. [PMID: 33594280 DOI: 10.1038/s41580-021-00332-2] [Citation(s) in RCA: 159] [Impact Index Per Article: 53.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/13/2021] [Indexed: 02/06/2023]
Abstract
Mitochondria are cellular organelles responsible for generation of chemical energy in the process called oxidative phosphorylation. They originate from a bacterial ancestor and maintain their own genome, which is expressed by designated, mitochondrial transcription and translation machineries that differ from those operating for nuclear gene expression. In particular, the mitochondrial protein synthesis machinery is structurally and functionally very different from that governing eukaryotic, cytosolic translation. Despite harbouring their own genetic information, mitochondria are far from being independent of the rest of the cell and, conversely, cellular fitness is closely linked to mitochondrial function. Mitochondria depend heavily on the import of nuclear-encoded proteins for gene expression and function, and hence engage in extensive inter-compartmental crosstalk to regulate their proteome. This connectivity allows mitochondria to adapt to changes in cellular conditions and also mediates responses to stress and mitochondrial dysfunction. With a focus on mammals and yeast, we review fundamental insights that have been made into the biogenesis, architecture and mechanisms of the mitochondrial translation apparatus in the past years owing to the emergence of numerous near-atomic structures and a considerable amount of biochemical work. Moreover, we discuss how cellular mitochondrial protein expression is regulated, including aspects of mRNA and tRNA maturation and stability, roles of auxiliary factors, such as translation regulators, that adapt mitochondrial translation rates, and the importance of inter-compartmental crosstalk with nuclear gene expression and cytosolic translation and how it enables integration of mitochondrial translation into the cellular context.
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15
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Lee M, Matsunaga N, Akabane S, Yasuda I, Ueda T, Takeuchi-Tomita N. Reconstitution of mammalian mitochondrial translation system capable of correct initiation and long polypeptide synthesis from leaderless mRNA. Nucleic Acids Res 2021; 49:371-382. [PMID: 33300043 PMCID: PMC7797035 DOI: 10.1093/nar/gkaa1165] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 11/12/2020] [Accepted: 11/16/2020] [Indexed: 12/31/2022] Open
Abstract
Mammalian mitochondria have their own dedicated protein synthesis system, which produces 13 essential subunits of the oxidative phosphorylation complexes. We have reconstituted an in vitro translation system from mammalian mitochondria, utilizing purified recombinant mitochondrial translation factors, 55S ribosomes from pig liver mitochondria, and a tRNA mixture from either Escherichia coli or yeast. The system is capable of translating leaderless mRNAs encoding model proteins (DHFR and nanoLuciferase) or some mtDNA-encoded proteins. We show that a leaderless mRNA, encoding nanoLuciferase, is faithfully initiated without the need for any auxiliary factors other than IF-2mt and IF-3mt. We found that the ribosome-dependent GTPase activities of both the translocase EF-G1mt and the recycling factor EF-G2mt are insensitive to fusidic acid (FA), the translation inhibitor that targets bacterial EF-G homologs, and consequently the system is resistant to FA. Moreover, we demonstrate that a polyproline sequence in the protein causes 55S mitochondrial ribosome stalling, yielding ribosome nascent chain complexes. Analyses of the effects of the Mg concentration on the polyproline-mediated ribosome stalling suggested the unique regulation of peptide elongation by the mitoribosome. This system will be useful for analyzing the mechanism of translation initiation, and the interactions between the nascent peptide chain and the mitochondrial ribosome.
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Affiliation(s)
- Muhoon Lee
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Noriko Matsunaga
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Shiori Akabane
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan.,Department of Life Science, Rikkyo University, Tokyo, 171-8501, Japan
| | - Ippei Yasuda
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Takuya Ueda
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan.,Department of Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, Tokyo, Shinjuku 162-8480, Japan
| | - Nono Takeuchi-Tomita
- Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
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16
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Shetty S, Varshney U. Regulation of translation by one-carbon metabolism in bacteria and eukaryotic organelles. J Biol Chem 2021; 296:100088. [PMID: 33199376 PMCID: PMC7949028 DOI: 10.1074/jbc.rev120.011985] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 11/15/2020] [Accepted: 11/16/2020] [Indexed: 12/20/2022] Open
Abstract
Protein synthesis is an energetically costly cellular activity. It is therefore important that the process of mRNA translation remains in excellent synchrony with cellular metabolism and its energy reserves. Unregulated translation could lead to the production of incomplete, mistranslated, or misfolded proteins, squandering the energy needed for cellular sustenance and causing cytotoxicity. One-carbon metabolism (OCM), an integral part of cellular intermediary metabolism, produces a number of one-carbon unit intermediates (formyl, methylene, methenyl, methyl). These OCM intermediates are required for the production of amino acids such as methionine and other biomolecules such as purines, thymidylate, and redox regulators. In this review, we discuss how OCM impacts the translation apparatus (composed of ribosome, tRNA, mRNA, and translation factors) and regulates crucial steps in protein synthesis. More specifically, we address how the OCM metabolites regulate the fidelity and rate of translation initiation in bacteria and eukaryotic organelles such as mitochondria. Modulation of the fidelity of translation initiation by OCM opens new avenues to understand alternative translation mechanisms involved in stress tolerance and drug resistance.
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Affiliation(s)
- Sunil Shetty
- Biozentrum, University of Basel, Basel, Switzerland
| | - Umesh Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India; Jawaharlal Nehru Centre for Advanced Scientific Studies, Jakkur, Bangalore, India.
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17
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Schmitt E, Coureux PD, Kazan R, Bourgeois G, Lazennec-Schurdevin C, Mechulam Y. Recent Advances in Archaeal Translation Initiation. Front Microbiol 2020; 11:584152. [PMID: 33072057 PMCID: PMC7531240 DOI: 10.3389/fmicb.2020.584152] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 08/24/2020] [Indexed: 12/20/2022] Open
Abstract
Translation initiation (TI) allows accurate selection of the initiation codon on a messenger RNA (mRNA) and defines the reading frame. In all domains of life, translation initiation generally occurs within a macromolecular complex made up of the small ribosomal subunit, the mRNA, a specialized methionylated initiator tRNA, and translation initiation factors (IFs). Once the start codon is selected at the P site of the ribosome and the large subunit is associated, the IFs are released and a ribosome competent for elongation is formed. However, even if the general principles are the same in the three domains of life, the molecular mechanisms are different in bacteria, eukaryotes, and archaea and may also vary depending on the mRNA. Because TI mechanisms have evolved lately, their studies bring important information about the evolutionary relationships between extant organisms. In this context, recent structural data on ribosomal complexes and genome-wide studies are particularly valuable. This review focuses on archaeal translation initiation highlighting its relationships with either the eukaryotic or the bacterial world. Eukaryotic features of the archaeal small ribosomal subunit are presented. Ribosome evolution and TI mechanisms diversity in archaeal branches are discussed. Next, the use of leaderless mRNAs and that of leadered mRNAs having Shine-Dalgarno sequences is analyzed. Finally, the current knowledge on TI mechanisms of SD-leadered and leaderless mRNAs is detailed.
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Affiliation(s)
- Emmanuelle Schmitt
- Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole Polytechnique, CNRS-UMR7654, Institut Polytechnique de Paris, Palaiseau, France
| | - Pierre-Damien Coureux
- Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole Polytechnique, CNRS-UMR7654, Institut Polytechnique de Paris, Palaiseau, France
| | - Ramy Kazan
- Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole Polytechnique, CNRS-UMR7654, Institut Polytechnique de Paris, Palaiseau, France
| | - Gabrielle Bourgeois
- Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole Polytechnique, CNRS-UMR7654, Institut Polytechnique de Paris, Palaiseau, France
| | - Christine Lazennec-Schurdevin
- Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole Polytechnique, CNRS-UMR7654, Institut Polytechnique de Paris, Palaiseau, France
| | - Yves Mechulam
- Laboratoire de Biologie Structurale de la Cellule, BIOC, Ecole Polytechnique, CNRS-UMR7654, Institut Polytechnique de Paris, Palaiseau, France
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18
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Borowski LS, Szczesny RJ. Loading messenger RNAs onto ribosomes in human mitochondria: lessons learned from a bacterial toxin. FEBS J 2020; 288:434-436. [PMID: 32588551 DOI: 10.1111/febs.15435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 05/30/2020] [Indexed: 11/30/2022]
Abstract
Mitochondria are peculiar organelles because their function depends on genetic information that is present in two genomes: nuclear and mitochondrial. The expression of mitochondrially encoded information requires dedicated machinery. Many efforts have been made to identify this machinery and describe its relevant mechanisms. Recently, Bruni et al. reported a cellular model that they established to investigate the pathway for loading messenger RNAs onto ribosomes in human mitochondria. Their study revealed a role for monosome formation in the stability of mitochondrial mRNAs. Comment on: https://doi.org/10.1111/febs.15342.
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Affiliation(s)
- Lukasz S Borowski
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland.,Faculty of Biology, Institute of Genetics and Biotechnology, University of Warsaw, Poland
| | - Roman J Szczesny
- Institute of Biochemistry and Biophysics Polish Academy of Sciences, Warsaw, Poland
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19
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Bruni F, Proctor-Kent Y, Lightowlers RN, Chrzanowska-Lightowlers ZM. Messenger RNA delivery to mitoribosomes - hints from a bacterial toxin. FEBS J 2020; 288:437-451. [PMID: 32329962 PMCID: PMC7891357 DOI: 10.1111/febs.15342] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 04/06/2020] [Accepted: 04/21/2020] [Indexed: 11/28/2022]
Abstract
In mammalian mitochondria, messenger RNA is processed and matured from large primary transcripts in structures known as RNA granules. The identity of the factors and process transferring the matured mRNA to the mitoribosome for translation is unclear. Nascent mature transcripts are believed to associate initially with the small mitoribosomal subunit prior to recruitment of the large subunit to form the translationally active monosome. When the small subunit fails to assemble, however, the stability of mt‐mRNA is only marginally affected, and under these conditions, the LRPPRC/SLIRP RNA‐binding complex has been implicated in maintaining mt‐mRNA stability. Here, we exploit the activity of a bacterial ribotoxin, VapC20, to show that in the absence of the large mitoribosomal subunit, mt‐mRNA species are selectively lost. Further, if the small subunit is also depleted, the mt‐mRNA levels are recovered. As a consequence of these data, we suggest a natural pathway for loading processed mt‐mRNA onto the mitoribosome.
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Affiliation(s)
- Francesco Bruni
- The Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, UK.,Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Italy
| | - Yasmin Proctor-Kent
- The Wellcome Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, UK
| | - Robert N Lightowlers
- The Wellcome Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, UK
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20
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Assembly of Mitochondrial Complex I Requires the Low-Complexity Protein AMC1 in Chlamydomonas reinhardtii. Genetics 2020; 214:895-911. [PMID: 32075865 DOI: 10.1534/genetics.120.303029] [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: 11/11/2019] [Accepted: 02/05/2020] [Indexed: 11/18/2022] Open
Abstract
Complex I is the first enzyme involved in the mitochondrial electron transport chain. With >40 subunits of dual genetic origin, the biogenesis of complex I is highly intricate and poorly understood. We used Chlamydomonas reinhardtii as a model system to reveal factors involved in complex I biogenesis. Two insertional mutants, displaying a complex I assembly defect characterized by the accumulation of a 700 kDa subcomplex, were analyzed. Genetic analyses showed these mutations were allelic and mapped to the gene AMC1 (Cre16.g688900) encoding a low-complexity protein of unknown function. The complex I assembly and activity in the mutant was restored by complementation with the wild-type gene, confirming AMC1 is required for complex I biogenesis. The N terminus of AMC1 targets a reporter protein to yeast mitochondria, implying that AMC1 resides and functions in the Chlamydomonas mitochondria. Accordingly, in both mutants, loss of AMC1 function results in decreased abundance of the mitochondrial nd4 transcript, which encodes the ND4 membrane subunit of complex I. Loss of ND4 in a mitochondrial nd4 mutant is characterized by a membrane arm assembly defect, similar to that exhibited by loss of AMC1. These results suggest AMC1 is required for the production of mitochondrially-encoded complex I subunits, specifically ND4. We discuss the possible modes of action of AMC1 in mitochondrial gene expression and complex I biogenesis.
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21
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Ayyub SA, Varshney U. Translation initiation in mammalian mitochondria- a prokaryotic perspective. RNA Biol 2019; 17:165-175. [PMID: 31696767 DOI: 10.1080/15476286.2019.1690099] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
ATP is generated in mitochondria of eukaryotic cells by oxidative phosphorylation (OXPHOS). The OXPHOS complex, which is crucial for cellular metabolism, comprises of both nuclear and mitochondrially encoded subunits. Also, the occurrence of several pathologies because of mutations in the mitochondrial translation apparatus indicates the importance of mitochondrial translation and its regulation. The mitochondrial translation apparatus is similar to its prokaryotic counterpart due to a common origin of evolution. However, mitochondrial translation has diverged from prokaryotic translation in many ways by reductive evolution. In this review, we focus on mammalian mitochondrial translation initiation, a highly regulated step of translation, and present a comparison with prokaryotic translation.
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Affiliation(s)
- Shreya Ahana Ayyub
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Umesh Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.,Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, India
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22
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Koripella RK, Sharma MR, Haque ME, Risteff P, Spremulli LL, Agrawal RK. Structure of Human Mitochondrial Translation Initiation Factor 3 Bound to the Small Ribosomal Subunit. iScience 2019; 12:76-86. [PMID: 30677741 PMCID: PMC6352543 DOI: 10.1016/j.isci.2018.12.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/11/2018] [Accepted: 12/27/2018] [Indexed: 11/20/2022] Open
Abstract
The human mitochondrial translational initiation factor 3 (IF3mt) carries mitochondrial-specific amino acid extensions at both its N and C termini (N- and C-terminal extensions [NTE and CTE, respectively]), when compared with its eubacterial counterpart. Here we present 3.3- to 3.5-Å-resolution cryoelectron microscopic structures of the mammalian 28S mitoribosomal subunit in complex with human IF3mt. Unique contacts observed between the 28S subunit and N-terminal domain of IF3mt explain its unusually high affinity for the 28S subunit, whereas the position of the mito-specific NTE suggests NTE's role in binding of initiator tRNA to the 28S subunit. The location of the C-terminal domain (CTD) clarifies its anti-association activity, whereas the orientation of the mito-specific CTE provides a mechanistic explanation for its role in destabilizing initiator tRNA in the absence of mRNA. Furthermore, our structure hints at a possible role of the CTD in recruiting leaderless mRNAs for translation initiation. Our findings highlight unique features of IF3mt in mitochondrial translation initiation. High-resolution cryo-EM study of the mammalian 28S mitoribosome-IF3mt complex Interaction between the 28S and IF3mt's NTD explains NTD's unusual high affinity Provides insights into role of IF3mt's N-terminal extension in initiator tRNA binding Provides insights into roles of IF3mt's CTD and C-terminal extension in mRNA sensing
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Affiliation(s)
- Ravi K Koripella
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA
| | - Manjuli R Sharma
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA
| | - Md Emdadul Haque
- Department of Chemistry, Campus Box 3290, University of North Carolina, Chapel Hill, NC, USA
| | - Paul Risteff
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA
| | - Linda L Spremulli
- Department of Chemistry, Campus Box 3290, University of North Carolina, Chapel Hill, NC, USA
| | - Rajendra K Agrawal
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA; Department of Biomedical Sciences, School of Public Health, University at Albany, SUNY, Albany, NY, USA.
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23
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Unique features of mammalian mitochondrial translation initiation revealed by cryo-EM. Nature 2018; 560:263-267. [PMID: 30089917 DOI: 10.1038/s41586-018-0373-y] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/17/2018] [Indexed: 11/09/2022]
Abstract
Mitochondria maintain their own specialized protein synthesis machinery, which in mammals is used exclusively for the synthesis of the membrane proteins responsible for oxidative phosphorylation1,2. The initiation of protein synthesis in mitochondria differs substantially from bacterial or cytosolic translation systems. Mitochondrial translation initiation lacks initiation factor 1, which is essential in all other translation systems from bacteria to mammals3,4. Furthermore, only one type of methionyl transfer RNA (tRNAMet) is used for both initiation and elongation4,5, necessitating that the initiation factor specifically recognizes the formylated version of tRNAMet (fMet-tRNAMet). Lastly, most mitochondrial mRNAs do not possess 5' leader sequences to promote mRNA binding to the ribosome2. There is currently little mechanistic insight into mammalian mitochondrial translation initiation, and it is not clear how mRNA engagement, initiator-tRNA recruitment and start-codon selection occur. Here we determine the cryo-EM structure of the complete translation initiation complex from mammalian mitochondria at 3.2 Å. We describe the function of an additional domain insertion that is present in the mammalian mitochondrial initiation factor 2 (mtIF2). By closing the decoding centre, this insertion stabilizes the binding of leaderless mRNAs and induces conformational changes in the rRNA nucleotides involved in decoding. We identify unique features of mtIF2 that are required for specific recognition of fMet-tRNAMet and regulation of its GTPase activity. Finally, we observe that the ribosomal tunnel in the initiating ribosome is blocked by insertion of the N-terminal portion of mitochondrial protein mL45, which becomes exposed as the ribosome switches to elongation mode and may have an additional role in targeting of mitochondrial ribosomes to the protein-conducting pore in the inner mitochondrial membrane.
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24
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Müller D, Telieps T, Eugster A, Weinzierl C, Jolink M, Ziegler AG, Bonifacio E. Novel minor HLA DR associated antigens in type 1 diabetes. Clin Immunol 2018; 194:87-91. [PMID: 29990590 DOI: 10.1016/j.clim.2018.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 06/04/2018] [Accepted: 07/01/2018] [Indexed: 12/12/2022]
Abstract
Type 1 diabetes is an autoimmune disease leading to insulin deficiency. Autoantibodies to beta cell proteins are already present in the asymptomatic phase of type 1 diabetes. Recent findings have suggested a number of additional minor autoantigens in patients with type 1 diabetes. We have established luciferase immunoprecipitation systems (LIPS) for anti-MTIF3, anti-PPIL2, anti-NUP50 and anti-MLH1 and analyzed samples from 500 patients with type 1 diabetes at onset of clinical disease and 200 healthy individuals who had a family history of type 1 diabetes but no evidence of beta cell autoantibodies. We show significantly higher frequencies of anti-MTIF3, anti-PPIL2 and anti-MLH1 in recent onset type 1 diabetes patients in comparison to controls. In addition, antibodies to NUP50 were associated with HLA-DRB1*03 and antibodies to MLH1 were associated with HLA-DRB1*04 genotypes.
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Affiliation(s)
- Denise Müller
- DFG Research Center for Regenerative Therapies Dresden, Faculty of Medicine, Technische Universität Dresden, Dresden, Germany
| | - Tanja Telieps
- Helmholtz Zentrum München, Institute for Diabetes and Obesity, Neuherberg, Germany
| | - Anne Eugster
- DFG Research Center for Regenerative Therapies Dresden, Faculty of Medicine, Technische Universität Dresden, Dresden, Germany
| | - Christina Weinzierl
- Institute of Diabetes Research, Helmholtz Zentrum München, and Forschergruppe Diabetes, Klinikum rechts der Isar, Technische Universität München, Neuherberg, Germany
| | - Manja Jolink
- Institute of Diabetes Research, Helmholtz Zentrum München, and Forschergruppe Diabetes, Klinikum rechts der Isar, Technische Universität München, Neuherberg, Germany
| | - Anette-Gabriele Ziegler
- Institute of Diabetes Research, Helmholtz Zentrum München, and Forschergruppe Diabetes, Klinikum rechts der Isar, Technische Universität München, Neuherberg, Germany; Forschergruppe Diabetes e.V, Neuherberg, Germany; German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Ezio Bonifacio
- DFG Research Center for Regenerative Therapies Dresden, Faculty of Medicine, Technische Universität Dresden, Dresden, Germany; Helmholtz Zentrum München, Institute for Diabetes and Obesity, Neuherberg, Germany; German Center for Diabetes Research (DZD), Neuherberg, Germany; Paul Langerhans Institute Dresden, German Center for Diabetes Research (DZD), Technische Universität Dresden, Dresden, Germany.
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25
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Cahoon AB, Qureshi AA. Leaderless mRNAs are circularized in Chlamydomonas reinhardtii mitochondria. Curr Genet 2018; 64:1321-1333. [DOI: 10.1007/s00294-018-0848-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 05/27/2018] [Accepted: 05/28/2018] [Indexed: 11/28/2022]
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26
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Abstract
Transcription of the mitochondrial genome yields three large polycistronic transcripts that undergo multiple endonucleolytic processing steps, before resulting in functional mRNAs, tRNAs, and rRNAs. Cleavage of the large precursor transcripts is mainly performed by the RNase P complex and RNase Z that cleave mitochondrial pre-tRNAs at their 5' and 3' ends respectively. Most likely there are additional enzymes involved that still await identification and characterization. Defects in mitochondrial RNA processing have been associated with human disease. There are published cases of patients carrying mutations in either HSD17B10/MRPP2 (encoding a subunit of RNase P complex) or ELAC2 (coding for RNase Z). In addition, several mtDNA mutations within tRNA genes have been shown to affect RNA processing. Here, we describe detailed protocols for analyzing RNA processing of mitochondrial tRNAs, in particular their 3'-ends that are processed by RNase Z. These protocols should serve as a guide to extract RNA for quantitative real-time PCR and RNAseq analysis.
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27
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Gao F, Wesolowska M, Agami R, Rooijers K, Loayza-Puch F, Lawless C, Lightowlers RN, Chrzanowska-Lightowlers ZMA. Using mitoribosomal profiling to investigate human mitochondrial translation. Wellcome Open Res 2017; 2:116. [PMID: 29387808 PMCID: PMC5771143 DOI: 10.12688/wellcomeopenres.13119.2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2017] [Indexed: 11/30/2022] Open
Abstract
Background: Gene expression in human mitochondria has various idiosyncratic features. One of these was recently revealed as the unprecedented recruitment of a mitochondrially-encoded tRNA as a structural component of the large mitoribosomal subunit. In porcine particles this is mt-tRNA
Phe whilst in humans it is mt-tRNA
Val. We have previously shown that when a mutation in mt-tRNA
Val causes very low steady state levels, there is preferential recruitment of mt-tRNA
Phe. We have investigated whether this altered mitoribosome affects intra-organellar protein synthesis. Methods: By using mitoribosomal profiling we have revealed aspects of mitoribosome behaviour with its template mt-mRNA under both normal conditions as well as those where the mitoribosome has incorporated mt-tRNA
Phe. Results: Analysis of the mitoribosome residency on transcripts under control conditions reveals that although mitochondria employ only 22 mt-tRNAs for protein synthesis, the use of non-canonical wobble base pairs at codon position 3 does not cause any measurable difference in mitoribosome occupancy irrespective of the codon. Comparison of the profile of aberrant mt-tRNA
Phe containing mitoribosomes with those of controls that integrate mt-tRNA
Val revealed that the impaired translation seen in the latter was not due to stalling on triplets encoding either of these amino acids. The alterations in mitoribosome interactions with start codons was not directly attributable to the either the use of non-cognate initiation codons or the presence or absence of 5’ leader sequences, except in the two bicistronic RNA units,
RNA7 and
RNA14 where the initiation sites are internal. Conclusions: These data report the power of mitoribosomal profiling in helping to understand the subtleties of mammalian mitochondrial protein synthesis. Analysis of profiles from the mutant mt-tRNA
Val cell line suggest that despite mt-tRNA
Phe being preferred in the porcine mitoribosome, its integration into the human counterpart results in a suboptimal structure that modifies its interaction with mt-mRNAs.
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Affiliation(s)
- Fei Gao
- The Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
| | - Maria Wesolowska
- The Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.,Immunocore Ltd, Oxford, UK
| | - Reuven Agami
- The Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Koos Rooijers
- The Netherlands Cancer Institute, Amsterdam, Netherlands.,Hubrecht Institute, Utrecht, Netherlands
| | | | - Conor Lawless
- The Wellcome Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Robert N Lightowlers
- The Wellcome Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
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28
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Gao F, Wesolowska M, Agami R, Rooijers K, Loayza-Puch F, Lawless C, Lightowlers RN, Chrzanowska-Lightowlers ZMA. Using mitoribosomal profiling to investigate human mitochondrial translation. Wellcome Open Res 2017. [PMID: 29387808 DOI: 10.12688/wellcomeopenres.13119.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Background: Gene expression in human mitochondria has various idiosyncratic features. One of these was recently revealed as the unprecedented recruitment of a mitochondrially-encoded tRNA as a structural component of the large mitoribosomal subunit. In porcine particles this is mt-tRNA Phe whilst in humans it is mt-tRNA Val. We have previously shown that when a mutation in mt-tRNA Val causes very low steady state levels, there is preferential recruitment of mt-tRNA Phe. We have investigated whether this altered mitoribosome affects intra-organellar protein synthesis. Methods: By using mitoribosomal profiling we have revealed aspects of mitoribosome behaviour with its template mt-mRNA under both normal conditions as well as those where the mitoribosome has incorporated mt-tRNA Phe. Results: Analysis of the mitoribosome residency on transcripts under control conditions reveals that although mitochondria employ only 22 mt-tRNAs for protein synthesis, the use of non-canonical wobble base pairs at codon position 3 does not cause any measurable difference in mitoribosome occupancy irrespective of the codon. Comparison of the profile of aberrant mt-tRNA Phe containing mitoribosomes with those of controls that integrate mt-tRNA Val revealed that the impaired translation seen in the latter was not due to stalling on triplets encoding either of these amino acids. The alterations in mitoribosome interactions with start codons was not directly attributable to the either the use of non-cognate initiation codons or the presence or absence of 5' leader sequences, except in the two bicistronic RNA units, RNA7 and RNA14 where the initiation sites are internal. Conclusions: These data report the power of mitoribosomal profiling in helping to understand the subtleties of mammalian mitochondrial protein synthesis. Analysis of profiles from the mutant mt-tRNA Val cell line suggest that despite mt-tRNA Phe being preferred in the porcine mitoribosome, its integration into the human counterpart results in a suboptimal structure that modifies its interaction with mt-mRNAs.
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Affiliation(s)
- Fei Gao
- The Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK
| | - Maria Wesolowska
- The Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, UK.,Immunocore Ltd, Oxford, UK
| | - Reuven Agami
- The Netherlands Cancer Institute, Amsterdam, Netherlands
| | - Koos Rooijers
- The Netherlands Cancer Institute, Amsterdam, Netherlands.,Hubrecht Institute, Utrecht, Netherlands
| | | | - Conor Lawless
- The Wellcome Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
| | - Robert N Lightowlers
- The Wellcome Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, UK
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29
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Akulich KA, Andreev DE, Terenin IM, Smirnova VV, Anisimova AS, Makeeva DS, Arkhipova VI, Stolboushkina EA, Garber MB, Prokofjeva MM, Spirin PV, Prassolov VS, Shatsky IN, Dmitriev SE. Four translation initiation pathways employed by the leaderless mRNA in eukaryotes. Sci Rep 2016; 6:37905. [PMID: 27892500 PMCID: PMC5124965 DOI: 10.1038/srep37905] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 11/02/2016] [Indexed: 01/09/2023] Open
Abstract
mRNAs lacking 5′ untranslated regions (leaderless mRNAs) are molecular relics of an ancient translation initiation pathway. Nevertheless, they still represent a significant portion of transcriptome in some taxons, including a number of eukaryotic species. In bacteria and archaea, the leaderless mRNAs can bind non-dissociated 70 S ribosomes and initiate translation without protein initiation factors involved. Here we use the Fleeting mRNA Transfection technique (FLERT) to show that translation of a leaderless reporter mRNA is resistant to conditions when eIF2 and eIF4F, two key eukaryotic translation initiation factors, are inactivated in mammalian cells. We report an unconventional translation initiation pathway utilized by the leaderless mRNA in vitro, in addition to the previously described 80S-, eIF2-, or eIF2D-mediated modes. This mechanism is a bacterial-like eIF5B/IF2-assisted initiation that has only been reported for hepatitis C virus-like internal ribosome entry sites (IRESs). Therefore, the leaderless mRNA is able to take any of four different translation initiation pathways in eukaryotes.
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Affiliation(s)
- Kseniya A Akulich
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia.,School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Dmitry E Andreev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Ilya M Terenin
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia.,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Victoria V Smirnova
- School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119234, Russia.,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Aleksandra S Anisimova
- School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119234, Russia.,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Desislava S Makeeva
- School of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, 119234, Russia.,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Valentina I Arkhipova
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Elena A Stolboushkina
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Maria B Garber
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia
| | - Maria M Prokofjeva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Pavel V Spirin
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Vladimir S Prassolov
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Ivan N Shatsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia
| | - Sergey E Dmitriev
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia.,Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119234, Russia.,Department of Biochemistry, Biological Faculty, Lomonosov Moscow State University, Moscow, 119991, Russia
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30
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Abstract
Oxidative phosphorylation (OXPHOS) is the mechanism whereby ATP, the major energy source for the cell, is produced by harnessing cellular respiration in the mitochondrion. This is facilitated by five multi-subunit complexes housed within the inner mitochondrial membrane. These complexes, with the exception of complex II, are of a dual genetic origin, requiring expression from nuclear and mitochondrial genes. Mitochondrially encoded mRNA is translated on the mitochondrial ribosome (mitoribosome) and the recent release of the near atomic resolution structure of the mammalian mitoribosome has highlighted its peculiar features. However, whereas some aspects of mitochondrial translation are understood, much is to be learnt about the presentation of mitochondrial mRNA to the mitoribosome, the biogenesis of the machinery, the exact role of the membrane, the constitution of the translocon/insertion machinery and the regulation of translation in the mitochondrion. This review addresses our current knowledge of mammalian mitochondrial gene expression, highlights key questions and indicates how defects in this process can result in profound mitochondrial disease.
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31
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Affiliation(s)
- Martin Ott
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden;
| | - Alexey Amunts
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden;
- Science for Life Laboratory, Stockholm University, SE-171 21 Solna, Sweden;
| | - Alan Brown
- Laboratory of Molecular Biology, Medical Research Council, Cambridge CB2 0QH, United Kingdom;
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32
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Potluri P, Procaccio V, Scheffler IE, Wallace DC. High throughput gene complementation screening permits identification of a mammalian mitochondrial protein synthesis (ρ(-)) mutant. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1857:1336-1343. [PMID: 26946086 DOI: 10.1016/j.bbabio.2016.02.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 02/24/2016] [Accepted: 02/25/2016] [Indexed: 12/26/2022]
Abstract
To identify nuclear DNA (nDNA) oxidative phosphorylation (OXPHOS) gene mutations using cultured cells, we have developed a complementation system based on retroviral transduction with a full length cDNA expression library and selection for OXHOS function by growth in galactose. We have used this system to transduce the Chinese hamster V79-G7 OXPHOS mutant cell line with a defect in mitochondrial protein synthesis. The complemented cells were found to have acquired the cDNA for the bS6m polypeptide of the small subunit of the mitochondrial ribosome. bS6m is a 14 kDa polypeptide located on the outside of the mitochondrial 28S ribosomal subunit and interacts with the rRNA. The V79-G7 mutant protein was found to harbor a methionine to threonine missense mutation at codon 13. The hamster bS6m null mutant could also be complemented by its orthologs from either mouse or human. bS6m protein tagged at its C-terminus by HA, His or GFP localized to the mitochondrion and was fully functional. Through site-directed mutagenesis we identified the probable RNA interacting residues of the bS6m peptide and tested the functional significance of mammalian specific C-terminal region. The N-terminus of the bS6m polypeptide functionally corresponds to that of the prokaryotic small ribosomal subunit, but deletion of C-terminal residues along with the zinc ion coordinating cysteine had no functional effect. Since mitochondrial diseases can result from hundreds to thousands of different nDNA gene mutations, this one step viral complementation cloning may facilitate the molecular diagnosis of a range of nDNA mitochondrial disease mutations. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
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Affiliation(s)
- Prasanth Potluri
- Center for Mitochondrial and Epigenomic Medicine, The Children's Hospital of Philadelphia, Department of Pathology and Laboratory of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Vincent Procaccio
- Dépt. de Biochimie et Génétique, Centre Hospitalier Universitaire d'Angers, Angers, France
| | - Immo E Scheffler
- Division of Biological Sciences, University of California - San Diego, La Jolla, CA, United States
| | - Douglas C Wallace
- Center for Mitochondrial and Epigenomic Medicine, The Children's Hospital of Philadelphia, Department of Pathology and Laboratory of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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33
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Leaderless Transcripts and Small Proteins Are Common Features of the Mycobacterial Translational Landscape. PLoS Genet 2015; 11:e1005641. [PMID: 26536359 PMCID: PMC4633059 DOI: 10.1371/journal.pgen.1005641] [Citation(s) in RCA: 163] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 10/10/2015] [Indexed: 11/19/2022] Open
Abstract
RNA-seq technologies have provided significant insight into the transcription networks of mycobacteria. However, such studies provide no definitive information on the translational landscape. Here, we use a combination of high-throughput transcriptome and proteome-profiling approaches to more rigorously understand protein expression in two mycobacterial species. RNA-seq and ribosome profiling in Mycobacterium smegmatis, and transcription start site (TSS) mapping and N-terminal peptide mass spectrometry in Mycobacterium tuberculosis, provide complementary, empirical datasets to examine the congruence of transcription and translation in the Mycobacterium genus. We find that nearly one-quarter of mycobacterial transcripts are leaderless, lacking a 5’ untranslated region (UTR) and Shine-Dalgarno ribosome-binding site. Our data indicate that leaderless translation is a major feature of mycobacterial genomes and is comparably robust to leadered initiation. Using translational reporters to systematically probe the cis-sequence requirements of leaderless translation initiation in mycobacteria, we find that an ATG or GTG at the mRNA 5’ end is both necessary and sufficient. This criterion, together with our ribosome occupancy data, suggests that mycobacteria encode hundreds of small, unannotated proteins at the 5’ ends of transcripts. The conservation of small proteins in both mycobacterial species tested suggests that some play important roles in mycobacterial physiology. Our translational-reporter system further indicates that mycobacterial leadered translation initiation requires a Shine Dalgarno site in the 5’ UTR and that ATG, GTG, TTG, and ATT codons can robustly initiate translation. Our combined approaches provide the first comprehensive view of mycobacterial gene structures and their non-canonical mechanisms of protein expression. The current paradigm for bacterial translation is based on an mRNA that includes an untranslated leader sequence containing the ribosome-binding site upstream of the initiation codon. We applied genome-scale approaches to map the protein-coding regions in the genomes of Mycobacterium smegmatis and Mycobacterium tuberculosis. We found that nearly one-quarter of mycobacterial transcripts are leaderless in mycobacterial species, thus indicating that ribosomes must recognize these mRNAs by a novel mechanism and suggesting that there are alternative modes of bacterial translation beyond the Escherichia coli paradigm. Our translational profiling showed that many mycobacterial proteins are mis-annotated, and also found many new genes encoding small proteins that had been previously overlooked, which are likely to play novel roles in diverse cellular processes. We also developed a new reporter system that provides mechanistic insights into translation initiation through deep sequencing. Our data show that leaderless translation is a robust process that is conserved in mycobacteria, that leaderless translation only requires that the mRNA begin with a start codon, and predict that mycobacteria encode hundreds of small proteins. This work will help us understand gene structure, genome organization and protein expression in bacteria, and how the translational machinery differs in different organisms.
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34
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Abstract
Understanding regulation of mitochondrial DNA (mtDNA) expression is of considerable interest given that mitochondrial dysfunction is important in human pathology and aging. Similar to the situation in bacteria, there is no compartmentalization between transcription and translation in mitochondria; hence, both processes are likely to have a direct molecular crosstalk. Accumulating evidence suggests that there are important mechanisms for regulation of mammalian mtDNA expression at the posttranscriptional level. Regulation of mRNA maturation, mRNA stability, translational coordination, ribosomal biogenesis, and translation itself all form the basis for controlling oxidative phosphorylation capacity. Consequently, a wide variety of inherited human mitochondrial diseases are caused by mutations of nuclear genes regulating various aspects of mitochondrial translation. Furthermore, mutations of mtDNA, associated with human disease and aging, often affect tRNA genes critical for mitochondrial translation. Recent advances in molecular understanding of mitochondrial translation regulation will most likely provide novel avenues for modulating mitochondrial function for treating human disease.
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Affiliation(s)
- B Martin Hällberg
- Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Stockholm, Sweden; Röntgen-Ångström-Cluster, Karolinska Institutet Outstation, Centre for Structural Systems Biology, DESY Campus, 22603 Hamburg, Germany; European Molecular Biology Laboratory, Hamburg Unit, 22603 Hamburg, Germany.
| | - Nils-Göran Larsson
- Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, 509 31 Cologne, Germany; Department of Laboratory Medicine, Karolinska Institutet, 171 77 Stockholm, Sweden.
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35
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Wilson WC, Hornig-Do HT, Bruni F, Chang JH, Jourdain AA, Martinou JC, Falkenberg M, Spåhr H, Larsson NG, Lewis RJ, Hewitt L, Baslé A, Cross HE, Tong L, Lebel RR, Crosby AH, Chrzanowska-Lightowlers ZMA, Lightowlers RN. A human mitochondrial poly(A) polymerase mutation reveals the complexities of post-transcriptional mitochondrial gene expression. Hum Mol Genet 2014; 23:6345-55. [PMID: 25008111 PMCID: PMC4222368 DOI: 10.1093/hmg/ddu352] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The p.N478D missense mutation in human mitochondrial poly(A) polymerase (mtPAP) has previously been implicated in a form of spastic ataxia with optic atrophy. In this study, we have investigated fibroblast cell lines established from family members. The homozygous mutation resulted in the loss of polyadenylation of all mitochondrial transcripts assessed; however, oligoadenylation was retained. Interestingly, this had differential effects on transcript stability that were dependent on the particular species of transcript. These changes were accompanied by a severe loss of oxidative phosphorylation complexes I and IV, and perturbation of de novo mitochondrial protein synthesis. Decreases in transcript polyadenylation and in respiratory chain complexes were effectively rescued by overexpression of wild-type mtPAP. Both mutated and wild-type mtPAP localized to the mitochondrial RNA-processing granules thereby eliminating mislocalization as a cause of defective polyadenylation. In vitro polyadenylation assays revealed severely compromised activity by the mutated protein, which generated only short oligo(A) extensions on RNA substrates, irrespective of RNA secondary structure. The addition of LRPPRC/SLIRP, a mitochondrial RNA-binding complex, enhanced activity of the wild-type mtPAP resulting in increased overall tail length. The LRPPRC/SLIRP effect although present was less marked with mutated mtPAP, independent of RNA secondary structure. We conclude that (i) the polymerase activity of mtPAP can be modulated by the presence of LRPPRC/SLIRP, (ii) N478D mtPAP mutation decreases polymerase activity and (iii) the alteration in poly(A) length is sufficient to cause dysregulation of post-transcriptional expression and the pathogenic lack of respiratory chain complexes.
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Affiliation(s)
- William C Wilson
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health
| | - Hue-Tran Hornig-Do
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health
| | - Francesco Bruni
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health
| | - Jeong Ho Chang
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Alexis A Jourdain
- Department of Cell Biology, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Jean-Claude Martinou
- Department of Cell Biology, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
| | - Maria Falkenberg
- Department of Biochemistry and Cell Biology, University of Göteborg, Box 440, 40530 Göteborg, Sweden
| | - Henrik Spåhr
- Max Planck Institute for Biology of Ageing, Gleueler Strasse 50a, D-50931 Cologne, Germany
| | - Nils-Göran Larsson
- Max Planck Institute for Biology of Ageing, Gleueler Strasse 50a, D-50931 Cologne, Germany
| | | | | | - Arnaud Baslé
- Institute for Cell and Molecular Biosciences and
| | - Harold E Cross
- Department of Ophthalmology, University of Arizona School of Medicine, Tucson, AZ 85711, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Robert R Lebel
- Center for Behavior, Development, and Genetics, Medical Genetics, SUNY Upstate Medical University, Syracuse, NY 13210, USA and
| | - Andrew H Crosby
- Molecular Genetics, University of Exeter Medical School, Royal Devon and Exeter Hospital, Barrack Road, Exeter EX2 5DW, UK
| | - Zofia M A Chrzanowska-Lightowlers
- Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University Medical School, Newcastle upon Tyne NE2 4HH, UK,
| | - Robert N Lightowlers
- Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University Medical School, Newcastle upon Tyne NE2 4HH, UK,
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36
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Lightowlers RN, Rozanska A, Chrzanowska-Lightowlers ZM. Mitochondrial protein synthesis: figuring the fundamentals, complexities and complications, of mammalian mitochondrial translation. FEBS Lett 2014; 588:2496-503. [PMID: 24911204 PMCID: PMC4099522 DOI: 10.1016/j.febslet.2014.05.054] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 05/28/2014] [Accepted: 05/29/2014] [Indexed: 12/28/2022]
Abstract
Mitochondrial protein synthesis is essential for all mammals, being responsible for providing key components of the oxidative phosphorylation complexes. Although only thirteen different polypeptides are made, the molecular details of this deceptively simple process remain incomplete. Central to this process is a non-canonical ribosome, the mitoribosome, which has evolved to address its unique mandate. In this review, we integrate the current understanding of the molecular aspects of mitochondrial translation with recent advances in structural biology. We identify numerous key questions that we will need to answer if we are to increase our knowledge of the molecular mechanisms underlying mitochondrial protein synthesis.
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Affiliation(s)
- Robert N Lightowlers
- The Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
| | - Agata Rozanska
- The Wellcome Trust Centre for Mitochondrial Research, Institute for Cell and Molecular Biosciences, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK
| | - Zofia M Chrzanowska-Lightowlers
- The Wellcome Trust Centre for Mitochondrial Research, Institute of Neuroscience, Newcastle University, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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Jackson CB, Zbinden C, Gallati S, Schaller A. Heterologous expression from the human D-Loop in organello. Mitochondrion 2014; 17:67-75. [PMID: 24911383 DOI: 10.1016/j.mito.2014.05.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 05/29/2014] [Accepted: 05/30/2014] [Indexed: 12/20/2022]
Abstract
We report the expression of a linear reporter construct in isolated human mitochondria. The reporter construct contained the entire human D-Loop with adjacent tRNA (MTT) genes (mt.15956-647), the human ND1 gene with an in frame GFP gene and adjacent endogenous MTT genes and heterologous rat MTT genes. Natural competence of isolated human mitochondria of HepG2 cells was used to import reporter constructs. The import efficiency of various fluorescently labelled PCR-generated import substrates in the range of 250bp up to 3.5kb was assessed by quantitative PCR and evaluated by confocal microscopy. Heterologous expression of the imported construct was confirmed at RNA level by a circular RNA (cRNA)-RT-PCR assay for the expression of tRNAs and by in organello [α-(32)P]-UTP labelling and subsequent hybridisation to reporter-specific sequences for monitoring mRNA expression. Heterologous expression of rat mitochondrial tRNA(Leu(UUR)) (rMT-TL1) was confirmed by co-/post-transcriptional trinucleotide (CCA) addition. Interestingly, the rat-specific MT-TL1 was correctly processed in isolated human mitochondria at the 3' end, but showed an aberrant 5' end processing. Correct 3' end processing of the heterologous expressed mitochondrial rat tRNA(Ser2) (MT-TS2) was detected. These findings demonstrate the feasibility of genetic manipulation of human mitochondria, providing a tool for characterisation of cis-acting elements of the human mitochondrial genome and for the study of human mitochondrial tRNA processing in organello.
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Affiliation(s)
- C B Jackson
- Division of Human Genetics, Departments of Paediatrics Clinical Research, Inselspital, University of Berne, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Berne, Switzerland.
| | - C Zbinden
- Division of Human Genetics, Departments of Paediatrics Clinical Research, Inselspital, University of Berne, Switzerland.
| | - S Gallati
- Division of Human Genetics, Departments of Paediatrics Clinical Research, Inselspital, University of Berne, Switzerland.
| | - A Schaller
- Division of Human Genetics, Departments of Paediatrics Clinical Research, Inselspital, University of Berne, Switzerland.
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Kuzmenko AV, Levitskii SA, Vinogradova EN, Atkinson GC, Hauryliuk V, Zenkin N, Kamenski PA. Protein biosynthesis in mitochondria. BIOCHEMISTRY (MOSCOW) 2014; 78:855-66. [PMID: 24228873 DOI: 10.1134/s0006297913080014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Translation, that is biosynthesis of polypeptides in accordance with information encoded in the genome, is one of the most important processes in the living cell, and it has been in the spotlight of international research for many years. The mechanisms of protein biosynthesis in bacteria and in the eukaryotic cytoplasm are now understood in great detail. However, significantly less is known about translation in eukaryotic mitochondria, which is characterized by a number of unusual features. In this review, we summarize current knowledge about mitochondrial translation in different organisms while paying special attention to the aspects of this process that differ from cytoplasmic protein biosynthesis.
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Affiliation(s)
- A V Kuzmenko
- Department of Molecular Biology, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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Abstract
SIGNIFICANCE The mitochondrial genetic system is responsible for the production of a few core-subunits of the respiratory chain and ATP synthase, the membrane protein complexes driving oxidative phosphorylation (OXPHOS). Efficiency and accuracy of mitochondrial protein synthesis determines how efficiently new OXPHOS complexes can be made. RECENT ADVANCES The system responsible for expression of the mitochondrial-encoded subunits developed from that of the bacterial ancestor of mitochondria. Importantly, many aspects of genome organization, transcription, and translation have diverged during evolution. Recent research has provided new insights into the architecture, regulation, and organelle-specific features of mitochondrial translation. Mitochondrial ribosomes contain a number of proteins absent from prokaryotic ribosomes, implying that in mitochondria, ribosomes were tailored to fit the requirements of the organelle. In addition, mitochondrial gene expression is regulated post-transcriptionally by a number of mRNA-specific translational activators. At least in yeast, these factors can regulate translation in respect to OXPHOS complex assembly to adjust the level of newly synthesized proteins to amounts that can be successfully assembled into respiratory chain complexes. CRITICAL ISSUES Mitochondrial gene expression is determining aging in eukaryotes, and a number of recent reports indicate that efficiency of translation directly influences this process. FUTURE DIRECTIONS Here we will summarize recent advances in our understanding of mitochondrial protein synthesis by comparing the knowledge acquired in the systems most commonly used to study mitochondrial biogenesis. However, many steps have not been understood mechanistically. Innovative biochemical and genetic approaches have to be elaborated to shed light on these important processes.
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Affiliation(s)
- Kirsten Kehrein
- 1 Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University , Stockholm, Sweden
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Haack T, Kopajtich R, Freisinger P, Wieland T, Rorbach J, Nicholls T, Baruffini E, Walther A, Danhauser K, Zimmermann F, Husain R, Schum J, Mundy H, Ferrero I, Strom T, Meitinger T, Taylor R, Minczuk M, Mayr J, Prokisch H. ELAC2 mutations cause a mitochondrial RNA processing defect associated with hypertrophic cardiomyopathy. Am J Hum Genet 2013; 93:211-23. [PMID: 23849775 PMCID: PMC3738821 DOI: 10.1016/j.ajhg.2013.06.006] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Revised: 05/22/2013] [Accepted: 06/05/2013] [Indexed: 11/16/2022] Open
Abstract
The human mitochondrial genome encodes RNA components of its own translational machinery to produce the 13 mitochondrial-encoded subunits of the respiratory chain. Nuclear-encoded gene products are essential for all processes within the organelle, including RNA processing. Transcription of the mitochondrial genome generates large polycistronic transcripts punctuated by the 22 mitochondrial (mt) tRNAs that are conventionally cleaved by the RNase P-complex and the RNase Z activity of ELAC2 at 5' and 3' ends, respectively. We report the identification of mutations in ELAC2 in five individuals with infantile hypertrophic cardiomyopathy and complex I deficiency. We observed accumulated mtRNA precursors in affected individuals muscle and fibroblasts. Although mature mt-tRNA, mt-mRNA, and mt-rRNA levels were not decreased in fibroblasts, the processing defect was associated with impaired mitochondrial translation. Complementation experiments in mutant cell lines restored RNA processing and a yeast model provided additional evidence for the disease-causal role of defective ELAC2, thereby linking mtRNA processing to human disease.
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MESH Headings
- Amino Acid Sequence
- Cardiomyopathy, Hypertrophic/genetics
- Cardiomyopathy, Hypertrophic/metabolism
- Cardiomyopathy, Hypertrophic/pathology
- Cell Nucleus/genetics
- Cell Nucleus/metabolism
- Electron Transport/genetics
- Endoribonucleases/genetics
- Endoribonucleases/metabolism
- Female
- Fibroblasts/metabolism
- Fibroblasts/pathology
- Genetic Complementation Test
- Humans
- Infant
- Male
- Mitochondria/genetics
- Mitochondria/metabolism
- Molecular Sequence Data
- Muscles/metabolism
- Muscles/pathology
- Mutation
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Pedigree
- RNA Processing, Post-Transcriptional
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Mitochondrial
- RNA, Ribosomal/genetics
- RNA, Ribosomal/metabolism
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Tobias B. Haack
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Robert Kopajtich
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Peter Freisinger
- Department of Pediatrics, Klinikum Reutlingen, 72764 Reutlingen, Germany
| | - Thomas Wieland
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Joanna Rorbach
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, UK
| | | | - Enrico Baruffini
- Department of Life Sciences, University of Parma, 43124 Parma, Italy
| | - Anett Walther
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Katharina Danhauser
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
| | - Franz A. Zimmermann
- Department of Pediatrics, Paracelsus Medical University Salzburg, 5020 Salzburg, Austria
| | - Ralf A. Husain
- Department of Neuropediatrics, Jena University Hospital, 07740 Jena, Germany
| | - Jessica Schum
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Helen Mundy
- Centre for Inherited Metabolic Disease, Evelina Children’s Hospital, Guys and St Thomas’ NHS Foundation Trust, London SE1 7EH, UK
| | - Ileana Ferrero
- Department of Life Sciences, University of Parma, 43124 Parma, Italy
| | - Tim M. Strom
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | - Thomas Meitinger
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Munich, 81675 Munich, Germany
- Munich Heart Alliance, 80802 Munich, Germany
| | - Robert W. Taylor
- Wellcome Trust Centre for Mitochondrial Research, Institute for Ageing and Health, The Medical School, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Michal Minczuk
- MRC Mitochondrial Biology Unit, Hills Road, Cambridge CB2 0XY, UK
| | - Johannes A. Mayr
- Department of Pediatrics, Paracelsus Medical University Salzburg, 5020 Salzburg, Austria
| | - Holger Prokisch
- Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany
- Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
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Christian BE, Spremulli LL. Mechanism of protein biosynthesis in mammalian mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2011; 1819:1035-54. [PMID: 22172991 DOI: 10.1016/j.bbagrm.2011.11.009] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2011] [Revised: 11/03/2011] [Accepted: 11/08/2011] [Indexed: 01/25/2023]
Abstract
Protein synthesis in mammalian mitochondria produces 13 proteins that are essential subunits of the oxidative phosphorylation complexes. This review provides a detailed outline of each phase of mitochondrial translation including initiation, elongation, termination, and ribosome recycling. The roles of essential proteins involved in each phase are described. All of the products of mitochondrial protein synthesis in mammals are inserted into the inner membrane. Several proteins that may help bind ribosomes to the membrane during translation are described, although much remains to be learned about this process. Mutations in mitochondrial or nuclear genes encoding components of the translation system often lead to severe deficiencies in oxidative phosphorylation, and a summary of these mutations is provided. This article is part of a Special Issue entitled: Mitochondrial Gene Expression.
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Affiliation(s)
- Brooke E Christian
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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Scharff LB, Childs L, Walther D, Bock R. Local absence of secondary structure permits translation of mRNAs that lack ribosome-binding sites. PLoS Genet 2011; 7:e1002155. [PMID: 21731509 PMCID: PMC3121790 DOI: 10.1371/journal.pgen.1002155] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 05/05/2011] [Indexed: 02/05/2023] Open
Abstract
The initiation of translation is a fundamental and highly regulated process in gene expression. Translation initiation in prokaryotic systems usually requires interaction between the ribosome and an mRNA sequence upstream of the initiation codon, the so-called ribosome-binding site (Shine-Dalgarno sequence). However, a large number of genes do not possess Shine-Dalgarno sequences, and it is unknown how start codon recognition occurs in these mRNAs. We have performed genome-wide searches in various groups of prokaryotes in order to identify sequence elements and/or RNA secondary structural motifs that could mediate translation initiation in mRNAs lacking Shine-Dalgarno sequences. We find that mRNAs without a Shine-Dalgarno sequence are generally less structured in their translation initiation region and show a minimum of mRNA folding at the start codon. Using reporter gene constructs in bacteria, we also provide experimental support for local RNA unfoldedness determining start codon recognition in Shine-Dalgarno–independent translation. Consistent with this, we show that AUG start codons reside in single-stranded regions, whereas internal AUG codons are usually in structured regions of the mRNA. Taken together, our bioinformatics analyses and experimental data suggest that local absence of RNA secondary structure is necessary and sufficient to initiate Shine-Dalgarno–independent translation. Thus, our results provide a plausible mechanism for how the correct translation initiation site is recognized in the absence of a ribosome-binding site. Protein biosynthesis (translation) is a highly regulated process in gene expression. In all organisms, initiation of translation depends on molecular recognition of the messenger RNA by ribosomes. In prokaryotes (bacteria, mitochondria, and chloroplasts), this recognition is mediated by a specific sequence motif in the 5′ untranslated region of the mRNA, called “ribosome-binding site” or “Shine-Dalgarno sequence.” However, many messenger RNAs lack Shine-Dalgarno sequences, and it is currently unknown how the correct translation initiation site is recognized in these mRNAs. Here, we provide insights into the mechanism of translation initiation in the absence of a ribosome-binding site. We have performed genome-wide searches for Shine-Dalgarno–independent translation in bacterial and organellar genomes and report that a large fraction of transcripts is translated in a Shine-Dalgarno–independent manner in all prokaryotic systems. We find that Shine-Dalgarno–independent translation initiation is strongly correlated with the presence of a local minimum in RNA secondary structure around the translational start codon. The significance of RNA unfoldedness as the key determinant of start codon recognition in Shine-Dalgarno–independent translation initiation was confirmed experimentally by employing reporter gene fusions in the bacterium Escherichia coli. In conclusion, our work suggests an intriguing mechanism for translation initiation on mRNAs that lack a ribosome-binding site.
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Affiliation(s)
- Lars B Scharff
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
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43
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Rorbach J, Nicholls TJJ, Minczuk M. PDE12 removes mitochondrial RNA poly(A) tails and controls translation in human mitochondria. Nucleic Acids Res 2011; 39:7750-63. [PMID: 21666256 PMCID: PMC3177208 DOI: 10.1093/nar/gkr470] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Polyadenylation of mRNA in human mitochondria is crucial for gene expression and perturbation of poly(A) tail length has been linked to a human neurodegenerative disease. Here we show that 2′-phosphodiesterase (2′-PDE), (hereafter PDE12), is a mitochondrial protein that specifically removes poly(A) extensions from mitochondrial mRNAs both in vitro and in mitochondria of cultured cells. In eukaryotes, poly(A) tails generally stabilize mature mRNAs, whereas in bacteria they increase mRNA turnover. In human mitochondria, the effects of increased PDE12 expression were transcript dependent. An excess of PDE12 led to an increase in the level of three mt-mRNAs (ND1, ND2 and CytB) and two (CO1 and CO2) were less abundant than in mitochondria of control cells and there was no appreciable effect on the steady-state level of the remainder of the mitochondrial transcripts. The alterations in poly(A) tail length accompanying elevated PDE12 expression were associated with severe inhibition of mitochondrial protein synthesis, and consequently respiratory incompetence. Therefore, we propose that mRNA poly(A) tails are important in regulating protein synthesis in human mitochondria, as it is the case for nuclear-encoded eukaryotic mRNA.
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Affiliation(s)
- Joanna Rorbach
- MRC Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge CB2 0XY, UK
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44
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Chrzanowska-Lightowlers ZMA, Horvath R, Lightowlers RN. 175th ENMC International Workshop: Mitochondrial protein synthesis in health and disease, 25-27th June 2010, Naarden, The Netherlands. Neuromuscul Disord 2010; 21:142-7. [PMID: 21111623 DOI: 10.1016/j.nmd.2010.10.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Z M A Chrzanowska-Lightowlers
- Mitochondrial Research Group, Institute for Ageing and Health, Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
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