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Nieto-Panqueva F, Rubalcava-Gracia D, Hamel PP, González-Halphen D. The constraints of allotopic expression. Mitochondrion 2023; 73:30-50. [PMID: 37739243 DOI: 10.1016/j.mito.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Revised: 08/28/2023] [Accepted: 09/18/2023] [Indexed: 09/24/2023]
Abstract
Allotopic expression is the functional transfer of an organellar gene to the nucleus, followed by synthesis of the gene product in the cytosol and import into the appropriate organellar sub compartment. Here, we focus on mitochondrial genes encoding OXPHOS subunits that were naturally transferred to the nucleus, and critically review experimental evidence that claim their allotopic expression. We emphasize aspects that may have been overlooked before, i.e., when modifying a mitochondrial gene for allotopic expression━besides adapting the codon usage and including sequences encoding mitochondrial targeting signals━three additional constraints should be considered: (i) the average apparent free energy of membrane insertion (μΔGapp) of the transmembrane stretches (TMS) in proteins earmarked for the inner mitochondrial membrane, (ii) the final, functional topology attained by each membrane-bound OXPHOS subunit; and (iii) the defined mechanism by which the protein translocator TIM23 sorts cytosol-synthesized precursors. The mechanistic constraints imposed by TIM23 dictate the operation of two pathways through which alpha-helices in TMS are sorted, that eventually determine the final topology of membrane proteins. We used the biological hydrophobicity scale to assign an average apparent free energy of membrane insertion (μΔGapp) and a "traffic light" color code to all TMS of OXPHOS membrane proteins, thereby predicting which are more likely to be internalized into mitochondria if allotopically produced. We propose that the design of proteins for allotopic expression must make allowance for μΔGapp maximization of highly hydrophobic TMS in polypeptides whose corresponding genes have not been transferred to the nucleus in some organisms.
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Affiliation(s)
- Felipe Nieto-Panqueva
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Diana Rubalcava-Gracia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico; Division of Molecular Metabolism, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Patrice P Hamel
- Department of Molecular Genetics and Department of Biological Chemistry and Pharmacology, Ohio State University, Columbus, OH, USA; Vellore Institute of Technology (VIT), School of BioScience and Technology, Vellore, Tamil Nadu, India
| | - Diego González-Halphen
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
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2
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Lear SK, Nunez JA, Shipman SL. High-throughput colocalization pipeline quantifies efficacy of mitochondrial targeting signals across different protein types. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.03.535288. [PMID: 37066162 PMCID: PMC10103990 DOI: 10.1101/2023.04.03.535288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/18/2023]
Abstract
Efficient metabolic engineering and the development of mitochondrial therapeutics often rely upon the specific and strong import of foreign proteins into mitochondria. Fusing a protein to a mitochondria-bound signal peptide is a common method to localize proteins to mitochondria, but this strategy is not universally effective with particular proteins empirically failing to localize. To help overcome this barrier, this work develops a generalizable and open-source framework to design proteins for mitochondrial import and quantify their specific localization. By using a Python-based pipeline to quantitatively assess the colocalization of different proteins previously used for precise genome editing in a high-throughput manner, we reveal signal peptide-protein combinations that localize well in mitochondria and, more broadly, general trends about the overall reliability of commonly used mitochondrial targeting signals.
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Affiliation(s)
- Sierra K Lear
- Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, USA
- Graduate Program in Bioengineering, University of California, San Francisco and Berkeley, CA, USA
| | - Jose A Nunez
- Department of Mechanical Engineering, University of California, Santa Barbara, CA, USA
| | - Seth L Shipman
- Gladstone Institute of Data Science and Biotechnology, San Francisco, CA, USA
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA
- Chan Zuckerberg Biohub - San Francisco, San Francisco, CA, USA
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3
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Proteomics as a Tool for the Study of Mitochondrial Proteome, Its Dysfunctionality and Pathological Consequences in Cardiovascular Diseases. Int J Mol Sci 2023; 24:ijms24054692. [PMID: 36902123 PMCID: PMC10003354 DOI: 10.3390/ijms24054692] [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: 01/12/2023] [Revised: 02/20/2023] [Accepted: 02/23/2023] [Indexed: 03/04/2023] Open
Abstract
The focus of this review is on the proteomic approaches applied to the study of the qualitative/quantitative changes in mitochondrial proteins that are related to impaired mitochondrial function and consequently different types of pathologies. Proteomic techniques developed in recent years have created a powerful tool for the characterization of both static and dynamic proteomes. They can detect protein-protein interactions and a broad repertoire of post-translation modifications that play pivotal roles in mitochondrial regulation, maintenance and proper function. Based on accumulated proteomic data, conclusions can be derived on how to proceed in disease prevention and treatment. In addition, this article will present an overview of the recently published proteomic papers that deal with the regulatory roles of post-translational modifications of mitochondrial proteins and specifically with cardiovascular diseases connected to mitochondrial dysfunction.
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4
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The Mitochondrial Genome in Aging and Disease and the Future of Mitochondrial Therapeutics. Biomedicines 2022; 10:biomedicines10020490. [PMID: 35203698 PMCID: PMC8962324 DOI: 10.3390/biomedicines10020490] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 02/10/2022] [Accepted: 02/16/2022] [Indexed: 11/29/2022] Open
Abstract
Mitochondria are intracellular organelles that utilize nutrients to generate energy in the form of ATP by oxidative phosphorylation. Mitochondrial DNA (mtDNA) in humans is a 16,569 base pair double-stranded circular DNA that encodes for 13 vital proteins of the electron transport chain. Our understanding of the mitochondrial genome’s transcription, translation, and maintenance is still emerging, and human pathologies caused by mtDNA dysfunction are widely observed. Additionally, a correlation between declining mitochondrial DNA quality and copy number with organelle dysfunction in aging is well-documented in the literature. Despite tremendous advancements in nuclear gene-editing technologies and their value in translational avenues, our ability to edit mitochondrial DNA is still limited. In this review, we discuss the current therapeutic landscape in addressing the various pathologies that result from mtDNA mutations. We further evaluate existing gene therapy efforts, particularly allotopic expression and its potential to become an indispensable tool for restoring mitochondrial health in disease and aging.
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Karakaidos P, Rampias T. Mitonuclear Interactions in the Maintenance of Mitochondrial Integrity. Life (Basel) 2020; 10:life10090173. [PMID: 32878185 PMCID: PMC7555762 DOI: 10.3390/life10090173] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Accepted: 08/28/2020] [Indexed: 12/27/2022] Open
Abstract
In eukaryotic cells, mitochondria originated in an α-proteobacterial endosymbiont. Although these organelles harbor their own genome, the large majority of genes, originally encoded in the endosymbiont, were either lost or transferred to the nucleus. As a consequence, mitochondria have become semi-autonomous and most of their processes require the import of nuclear-encoded components to be functional. Therefore, the mitochondrial-specific translation has evolved to be coordinated by mitonuclear interactions to respond to the energetic demands of the cell, acquiring unique and mosaic features. However, mitochondrial-DNA-encoded genes are essential for the assembly of the respiratory chain complexes. Impaired mitochondrial function due to oxidative damage and mutations has been associated with numerous human pathologies, the aging process, and cancer. In this review, we highlight the unique features of mitochondrial protein synthesis and provide a comprehensive insight into the mitonuclear crosstalk and its co-evolution, as well as the vulnerabilities of the animal mitochondrial genome.
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Bertgen L, Mühlhaus T, Herrmann JM. Clingy genes: Why were genes for ribosomal proteins retained in many mitochondrial genomes? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1861:148275. [PMID: 32712152 DOI: 10.1016/j.bbabio.2020.148275] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 07/14/2020] [Accepted: 07/19/2020] [Indexed: 11/18/2022]
Abstract
Why mitochondria still retain their own genome is a puzzle given the enormous effort to maintain a mitochondrial translation machinery. Most mitochondrially encoded proteins are membrane-embedded subunits of the respiratory chain. Their hydrophobicity presumably impedes their import into mitochondria. However, many mitochondrial genomes also encode protein subunits of the mitochondrial ribosome. These proteins lack transmembrane domains and hydrophobicity cannot explain why their genes remained in mitochondria. In this review, we provide an overview about mitochondrially encoded subunits of mitochondrial ribosomes of fungi, plants and protists. Moreover, we discuss and evaluate different hypotheses which were put forward to explain why (ribosomal) proteins remained mitochondrially encoded. It seems likely that the synthesis of ribosomal proteins in the mitochondrial matrix is used to regulate the assembly of the mitochondrial ribosome within mitochondria and to avoid problems that mitochondrial proteins might pose for cytosolic proteostasis and for the assembly of cytosolic ribosomes.
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Affiliation(s)
- Lea Bertgen
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Straße 13, 67663 Kaiserslautern, Germany
| | - Timo Mühlhaus
- Computational Systems Biology, University of Kaiserslautern, Erwin-Schrödinger-Straße 23, 67663 Kaiserslautern, Germany
| | - Johannes M Herrmann
- Cell Biology, University of Kaiserslautern, Erwin-Schrödinger-Straße 13, 67663 Kaiserslautern, Germany.
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Lewis CJ, Dixit B, Batiuk E, Hall CJ, O'Connor MS, Boominathan A. Codon optimization is an essential parameter for the efficient allotopic expression of mtDNA genes. Redox Biol 2020; 30:101429. [PMID: 31981894 PMCID: PMC6976934 DOI: 10.1016/j.redox.2020.101429] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Revised: 12/29/2019] [Accepted: 01/10/2020] [Indexed: 11/29/2022] Open
Abstract
Mutations in mitochondrial DNA can be inherited or occur de novo leading to several debilitating myopathies with no curative option and few or no effective treatments. Allotopic expression of recoded mitochondrial genes from the nucleus has potential as a gene therapy strategy for such conditions, however progress in this field has been hampered by technical challenges. Here we employed codon optimization as a tool to re-engineer the protein-coding genes of the human mitochondrial genome for robust, efficient expression from the nucleus. All 13 codon-optimized constructs exhibited substantially higher protein expression than minimally-recoded genes when expressed transiently, and steady-state mRNA levels for optimized gene constructs were 5-180 fold enriched over recoded versions in stably-selected wildtype cells. Eight of thirteen mitochondria-encoded oxidative phosphorylation (OxPhos) proteins maintained protein expression following stable selection, with mitochondrial localization of expression products. We also assessed the utility of this strategy in rescuing mitochondrial disease cell models and found the rescue capacity of allotopic expression constructs to be gene specific. Allotopic expression of codon optimized ATP8 in disease models could restore protein levels and respiratory function, however, rescue of the pathogenic phenotype for another gene, ND1 was only partially successful. These results imply that though codon-optimization alone is not sufficient for functional allotopic expression of most mitochondrial genes, it is an essential consideration in their design.
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Affiliation(s)
- Caitlin J Lewis
- Department of Mitochondrial Research, SENS Research Foundation, Mountain View, CA, 94041, USA
| | - Bhavna Dixit
- Department of Mitochondrial Research, SENS Research Foundation, Mountain View, CA, 94041, USA
| | - Elizabeth Batiuk
- Department of Mitochondrial Research, SENS Research Foundation, Mountain View, CA, 94041, USA
| | - Carter J Hall
- Department of Mitochondrial Research, SENS Research Foundation, Mountain View, CA, 94041, USA
| | - Matthew S O'Connor
- Department of Mitochondrial Research, SENS Research Foundation, Mountain View, CA, 94041, USA.
| | - Amutha Boominathan
- Department of Mitochondrial Research, SENS Research Foundation, Mountain View, CA, 94041, USA.
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Rubalcava-Gracia D, García-Rincón J, Pérez-Montfort R, Hamel PP, González-Halphen D. Key within-membrane residues and precursor dosage impact the allotopic expression of yeast subunit II of cytochrome c oxidase. Mol Biol Cell 2019; 30:2358-2366. [PMID: 31318312 PMCID: PMC6741066 DOI: 10.1091/mbc.e18-12-0788] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Experimentally relocating mitochondrial genes to the nucleus for functional expression (allotopic expression) is a challenging process. The high hydrophobicity of mitochondria-encoded proteins seems to be one of the main factors preventing this allotopic expression. We focused on subunit II of cytochrome c oxidase (Cox2) to study which modifications may enable or improve its allotopic expression in yeast. Cox2 can be imported from the cytosol into mitochondria in the presence of the W56R substitution, which decreases the protein hydrophobicity and allows partial respiratory rescue of a cox2-null strain. We show that the inclusion of a positive charge is more favorable than substitutions that only decrease the hydrophobicity. We also searched for other determinants enabling allotopic expression in yeast by examining the COX2 gene in organisms where it was transferred to the nucleus during evolution. We found that naturally occurring variations at within-membrane residues in the legume Glycine max Cox2 could enable yeast COX2 allotopic expression. We also evidence that directing high doses of allotopically synthesized Cox2 to mitochondria seems to be counterproductive because the subunit aggregates at the mitochondrial surface. Our findings are relevant to the design of allotopic expression strategies and contribute to the understanding of gene retention in organellar genomes.
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Affiliation(s)
- Diana Rubalcava-Gracia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
| | - Juan García-Rincón
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
| | - Ruy Pérez-Montfort
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
| | - Patrice Paul Hamel
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210
| | - Diego González-Halphen
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de México 04510, Mexico
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Petrů M, Wideman J, Moore K, Alcock F, Palmer T, Doležal P. Evolution of mitochondrial TAT translocases illustrates the loss of bacterial protein transport machines in mitochondria. BMC Biol 2018; 16:141. [PMID: 30466434 PMCID: PMC6251230 DOI: 10.1186/s12915-018-0607-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Accepted: 11/01/2018] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Bacteria and mitochondria contain translocases that function to transport proteins across or insert proteins into their inner and outer membranes. Extant mitochondria retain some bacterial-derived translocases but have lost others. While BamA and YidC were integrated into general mitochondrial protein transport pathways (as Sam50 and Oxa1), the inner membrane TAT translocase, which uniquely transports folded proteins across the membrane, was retained sporadically across the eukaryote tree. RESULTS We have identified mitochondrial TAT machinery in diverse eukaryotic lineages and define three different types of eukaryote-encoded TatABC-derived machineries (TatAC, TatBC and TatC-only). Here, we investigate TatAC and TatC-only machineries, which have not been studied previously. We show that mitochondria-encoded TatAC of the jakobid Andalucia godoyi represent the minimal functional pathway capable of substituting for the Escherichia coli TatABC complex and can transport at least one substrate. However, selected TatC-only machineries, from multiple eukaryotic lineages, were not capable of supporting the translocation of this substrate across the bacterial membrane. Despite the multiple losses of the TatC gene from the mitochondrial genome, the gene was never transferred to the cell nucleus. Although the major constraint preventing nuclear transfer of mitochondrial TatC is likely its high hydrophobicity, we show that in chloroplasts, such transfer of TatC was made possible due to modifications of the first transmembrane domain. CONCLUSIONS At its origin, mitochondria inherited three inner membrane translocases Sec, TAT and Oxa1 (YidC) from its bacterial ancestor. Our work shows for the first time that mitochondrial TAT has likely retained its unique function of transporting folded proteins at least in those few eukaryotes with TatA and TatC subunits encoded in the mitochondrial genome. However, mitochondria, in contrast to chloroplasts, abandoned the machinery multiple times in evolution. The overall lower hydrophobicity of the Oxa1 protein was likely the main reason why this translocase was nearly universally retained in mitochondrial biogenesis pathways.
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Affiliation(s)
- Markéta Petrů
- Department of Parasitology, Faculty of Science, BIOCEV, Charles University, Průmyslová 595, 252 50, Vestec, Czech Republic
| | - Jeremy Wideman
- Wissenschaftskolleg zu Berlin, Wallotstrasse 19, 14193, Berlin, Germany
- Department of Biochemistry and Molecular Biology, Dalhousie University, PO Box 15000, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Kristoffer Moore
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Felicity Alcock
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Tracy Palmer
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Pavel Doležal
- Department of Parasitology, Faculty of Science, BIOCEV, Charles University, Průmyslová 595, 252 50, Vestec, Czech Republic.
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Abstract
Together, the nuclear and mitochondrial genomes encode the oxidative phosphorylation (OXPHOS) complexes that reside in the mitochondrial inner membrane and enable aerobic life. Mitochondria maintain their own genome that is expressed and regulated by factors distinct from their nuclear counterparts. For optimal function, the cell must ensure proper stoichiometric production of OXPHOS subunits by coordinating two physically separated and evolutionarily distinct gene expression systems. Here, we review our current understanding of mitonuclear coregulation primarily at the levels of transcription and translation. Additionally, we discuss other levels of coregulation that may exist but remain largely unexplored, including mRNA modification and stability and posttranslational protein degradation.
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Affiliation(s)
- R Stefan Isaac
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; , ,
| | - Erik McShane
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; , ,
| | - L Stirling Churchman
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; , ,
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11
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Rubalcava-Gracia D, Vázquez-Acevedo M, Funes S, Pérez-Martínez X, González-Halphen D. Mitochondrial versus nuclear gene expression and membrane protein assembly: the case of subunit 2 of yeast cytochrome c oxidase. Mol Biol Cell 2018; 29:820-833. [PMID: 29437907 PMCID: PMC5905295 DOI: 10.1091/mbc.e17-09-0560] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 01/12/2018] [Accepted: 02/01/2018] [Indexed: 12/24/2022] Open
Abstract
Deletion of the yeast mitochondrial gene COX2, encoding subunit 2 (mtCox2) of cytochrome c oxidase (CcO), results in a respiratory-incompetent Δcox2 strain. For a cytosol-synthesized Cox2 to restore respiratory growth, it must carry the W56R mutation (cCox2W56R). Nevertheless, only a fraction of cCox2W56R is matured in mitochondria, allowing ∼60% steady-state accumulation of CcO. This can be attributed either to the point mutation or to an inefficient biogenesis of cCox2W56R. We generated a strain expressing the mutant protein mtCox2W56R inside mitochondria which should follow the canonical biogenesis of mitochondria-encoded Cox2. This strain exhibited growth rates, CcO steady-state levels, and CcO activity similar to those of the wild type; therefore, the efficiency of Cox2 biogenesis is the limiting step for successful allotopic expression. Upon coexpression of cCox2W56R and mtCox2, each protein assembled into CcO independently from its genetic origin, resulting in a mixed population of CcO with most complexes containing the mtCox2 version. Notably, the presence of the mtCox2 enhances cCox2W56R incorporation. We provide proof of principle that an allotopically expressed Cox2 may complement a phenotype due to a mutant mitochondrial COX2 gene. These results are relevant to developing a rational design of genes for allotopic expression intended to treat human mitochondrial diseases.
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Affiliation(s)
- Diana Rubalcava-Gracia
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Miriam Vázquez-Acevedo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Xochitl Pérez-Martínez
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
| | - Diego González-Halphen
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 Ciudad México, D. F., Mexico
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12
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Szafranski P. Intercompartmental Piecewise Gene Transfer. Genes (Basel) 2017; 8:genes8100260. [PMID: 28984842 PMCID: PMC5664110 DOI: 10.3390/genes8100260] [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] [Received: 08/31/2017] [Revised: 09/25/2017] [Accepted: 09/28/2017] [Indexed: 11/16/2022] Open
Abstract
Gene relocation from the residual genomes of organelles to the nuclear genome still continues, although as a scaled down evolutionary phenomenon, limited in occurrence mostly to protists (sensu lato) and land plants. During this process, the structural integrity of transferred genes is usually preserved. However, the relocation of mitochondrial genes that code for respiratory chain and ribosomal proteins is sometimes associated with their fragmentation into two complementary genes. Herein, this review compiles cases of piecewise gene transfer from the mitochondria to the nucleus, and discusses hypothesized mechanistic links between the fission and relocation of those genes.
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Affiliation(s)
- Przemyslaw Szafranski
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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13
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Yamada Y, Ishikawa T, Harashima H. Validation of the use of an artificial mitochondrial reporter DNA vector containing a Cytomegalovirus promoter for mitochondrial transgene expression. Biomaterials 2017; 136:56-66. [DOI: 10.1016/j.biomaterials.2017.05.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 05/07/2017] [Accepted: 05/08/2017] [Indexed: 01/17/2023]
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14
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Sánchez-Vásquez L, Vázquez-Acevedo M, de la Mora J, Vega-deLuna F, Cardol P, Remacle C, Dreyfus G, González-Halphen D. Near-neighbor interactions of the membrane-embedded subunits of the mitochondrial ATP synthase of a chlorophycean alga. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:497-509. [DOI: 10.1016/j.bbabio.2017.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/25/2017] [Accepted: 04/29/2017] [Indexed: 12/24/2022]
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15
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Mitochondrial Nucleoid: Shield and Switch of the Mitochondrial Genome. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2017; 2017:8060949. [PMID: 28680532 PMCID: PMC5478868 DOI: 10.1155/2017/8060949] [Citation(s) in RCA: 77] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 03/06/2017] [Accepted: 04/03/2017] [Indexed: 11/18/2022]
Abstract
Mitochondria preserve very complex and distinctively unique machinery to maintain and express the content of mitochondrial DNA (mtDNA). Similar to chromosomes, mtDNA is packaged into discrete mtDNA-protein complexes referred to as a nucleoid. In addition to its role as a mtDNA shield, over 50 nucleoid-associated proteins play roles in mtDNA maintenance and gene expression through either temporary or permanent association with mtDNA or other nucleoid-associated proteins. The number of mtDNA(s) contained within a single nucleoid is a fundamental question but remains a somewhat controversial issue. Disturbance in nucleoid components and mutations in mtDNA were identified as significant in various diseases, including carcinogenesis. Significant interest in the nucleoid structure and its regulation has been stimulated in relation to mitochondrial diseases, which encompass diseases in multicellular organisms and are associated with accumulation of numerous mutations in mtDNA. In this review, mitochondrial nucleoid structure, nucleoid-associated proteins, and their regulatory roles in mitochondrial metabolism are briefly addressed to provide an overview of the emerging research field involving mitochondrial biology.
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16
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Barros MH, Tzagoloff A. Aep3p-dependent translation of yeast mitochondrial ATP8. Mol Biol Cell 2017; 28:1426-1434. [PMID: 28404747 PMCID: PMC5449143 DOI: 10.1091/mbc.e16-11-0775] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 03/29/2017] [Accepted: 04/04/2017] [Indexed: 12/14/2022] Open
Abstract
Yeast Aep3p, previously reported to stabilize mitochondrial ATP8 mRNA, also activates its translation. Temperature-sensitive aep3 mutants are specifically defective in translating ATP8 at the restrictive temperature. The respiratory deficiency of aep3 mutants is rescued by expression in the cytoplasm of allotopic ATP8. Translation of mitochondrial gene products in Saccharomyces cerevisiae depends on mRNA-specific activators that bind to the 5’ untranslated regions and promote translation on mitochondrial ribosomes. Here we find that Aep3p, previously shown to stabilize the bicistronic ATP8-ATP6 mRNA and facilitate initiation of translation from unformylated methionine, also activates specifically translation of ATP8. This is supported by several lines of evidence. Temperature-sensitive aep3 mutants are selectively blocked in incorporating [35S]methionine into Atp8p at nonpermissive but not at the permissive temperature. This phenotype is not a consequence of defective transcription or processing of the pre-mRNA. Neither is it explained by turnover of Aep3p, as evidenced by the failure of aep3 mutants to express a recoded ARG8m when this normally nuclear gene is substituted for ATP8 in mitochondrial DNA. Finally, translational of ATP8 mRNA in aep3 mutants is partially rescued by recoded allotopic ATP8 (nATP8) in a high-expression plasmid or in a CEN plasmid in the presence of recessive mutations in genes involved in stability and polyadenylation of RNA.
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Affiliation(s)
- Mario H Barros
- Departamento de Microbiologia, Universidade de Sao Paulo, Sao Paulo 05508-900, Brazil
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17
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Szafranski P. Evolutionarily recent, insertional fission of mitochondrial cox2 into complementary genes in bilaterian Metazoa. BMC Genomics 2017; 18:269. [PMID: 28359330 PMCID: PMC5374615 DOI: 10.1186/s12864-017-3626-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 03/14/2017] [Indexed: 11/21/2022] Open
Abstract
Background Mitochondrial genomes (mtDNA) of multicellular animals (Metazoa) with bilateral symmetry (Bilateria) are compact and usually carry 13 protein-coding genes for subunits of three respiratory complexes and ATP synthase. However, occasionally reported exceptions to this typical mtDNA organization prompted speculation that, as in protists and plants, some bilaterian mitogenomes may continue to lose their canonical genes, or may even acquire new genes. To shed more light on this phenomenon, a PCR-based screen was conducted to assess fast-evolving mtDNAs of apocritan Hymenoptera (Arthropoda, Insecta) for genomic rearrangements that might be associated with the modification of mitochondrial gene content. Results Sequencing of segmental inversions, identified in the screen, revealed that the cytochrome oxidase subunit II gene (cox2) of Campsomeris (Dielis) (Scoliidae) was split into two genes coding for COXIIA and COXIIB. The COXII-derived complementary polypeptides apparently form a heterodimer, have reduced hydrophobicity compared with the majority of mitogenome-encoded COX subunits, and one of them, COXIIB, features increased content of Cys residues. Analogous cox2 fragmentation is known only in two clades of protists (chlorophycean algae and alveolates), where it has been associated with piecewise relocation of this gene into the nucleus. In Campsomeris mtDNA, cox2a and cox2b loci are separated by a 3-kb large cluster of several antiparallel overlapping ORFs, one of which, qnu, seems to encode a nuclease that may have played a role in cox2 fission. Conclusions Although discontinuous mitochondrial protein genes encoding fragmented, complementary polypeptides are known in protists and some plants, split cox2 of Campsomeris is the first case of such a gene arrangement found in animals. The reported data also indicate that bilaterian animal mitogenomes may be carrying lineage-specific genes more often than previously thought, and suggest a homing endonuclease-based mechanism for insertional mitochondrial gene fission. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3626-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Przemyslaw Szafranski
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, ABBR, R851C, Houston, TX, 77030, USA.
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Coutinho E, Batista C, Sousa F, Queiroz J, Costa D. Mitochondrial Gene Therapy: Advances in Mitochondrial Gene Cloning, Plasmid Production, and Nanosystems Targeted to Mitochondria. Mol Pharm 2017; 14:626-638. [PMID: 28199112 DOI: 10.1021/acs.molpharmaceut.6b00823] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mitochondrial gene therapy seems to be a valuable and promising strategy to treat mitochondrial disorders. The use of a therapeutic vector based on mitochondrial DNA, along with its affinity to the site of mitochondria, can be considered a powerful tool in the reestablishment of normal mitochondrial function. In line with this and for the first time, we successfully cloned the mitochondrial gene ND1 that was stably maintained in multicopy pCAG-GFP plasmid, which is used to transform E. coli. This mitochondrial-gene-based plasmid was encapsulated into nanoparticles. Furthermore, the functionalization of nanoparticles with polymers, such as cellulose or gelatin, enhances their overall properties and performance for gene therapy. The fluorescence arising from rhodamine nanoparticles in mitochondria and a fluorescence microscopy study show pCAG-GFP-ND1-based nanoparticles' cell internalization and mitochondria targeting. The quantification of GFP expression strongly supports this finding. This work highlights the viability of gene therapy based on mitochondrial DNA instigating further in vitro research and clinical translation.
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Affiliation(s)
- Eduarda Coutinho
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior , Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - Cátia Batista
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior , Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - Fani Sousa
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior , Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - João Queiroz
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior , Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - Diana Costa
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior , Av. Infante D. Henrique, 6200-506 Covilhã, Portugal
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19
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Björkholm P, Ernst AM, Hagström E, Andersson SGE. Why mitochondria need a genome revisited. FEBS Lett 2016; 591:65-75. [PMID: 27928819 DOI: 10.1002/1873-3468.12510] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 11/15/2016] [Accepted: 11/21/2016] [Indexed: 01/13/2023]
Abstract
In this paper, we experimentally address the debate about why functional transfer of mitochondrial genes to the nucleus has been halted in some organismal groups and why cytosolic expression of mitochondrial proteins has proven remarkably difficult. By expressing all 13 human mitochondrial-encoded genes with strong mitochondrial-targeting sequences in the cytosol of human cells, we show that all proteins, except ATP8, are transported to the endoplasmic reticulum (ER). These results confirm and extend previous findings based on three mitochondrial genes lacking mitochondrial-targeting sequences that also were relocated to the ER during cytosolic expression. We conclude that subcellular protein targeting constitutes a major barrier to functional transfer of mitochondrial genes to the nuclear genome.
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Affiliation(s)
- Patrik Björkholm
- Department of Molecular Evolution, Cell and Molecular Biology, Uppsala University, Sweden
| | - Andreas M Ernst
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Erik Hagström
- Department of Molecular Evolution, Cell and Molecular Biology, Uppsala University, Sweden
| | - Siv G E Andersson
- Department of Molecular Evolution, Cell and Molecular Biology, Uppsala University, Sweden
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20
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Plazzi F, Puccio G, Passamonti M. Comparative Large-Scale Mitogenomics Evidences Clade-Specific Evolutionary Trends in Mitochondrial DNAs of Bivalvia. Genome Biol Evol 2016; 8:2544-64. [PMID: 27503296 PMCID: PMC5010914 DOI: 10.1093/gbe/evw187] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2016] [Indexed: 12/28/2022] Open
Abstract
Despite the figure of complete bivalve mitochondrial genomes keeps growing, an assessment of the general features of these genomes in a phylogenetic framework is still lacking, despite the fact that bivalve mitochondrial genomes are unusual under different aspects. In this work, we constructed a dataset of one hundred mitochondrial genomes of bivalves to perform the first systematic comparative mitogenomic analysis, developing a phylogenetic background to scaffold the evolutionary history of the class' mitochondrial genomes. Highly conserved domains were identified in all protein coding genes; however, four genes (namely, atp6, nad2, nad4L, and nad6) were found to be very divergent for many respects, notwithstanding the overall purifying selection working on those genomes. Moreover, the atp8 gene was newly annotated in 20 mitochondrial genomes, where it was previously declared as lacking or only signaled. Supernumerary mitochondrial proteins were compared, but it was possible to find homologies only among strictly related species. The rearrangement rate on the molecule is too high to be used as a phylogenetic marker, but here we demonstrate for the first time in mollusks that there is correlation between rearrangement rates and evolutionary rates. We also developed a new index (HERMES) to estimate the amount of mitochondrial evolution. Many genomic features are phylogenetically congruent and this allowed us to highlight three main phases in bivalve history: the origin, the branching of palaeoheterodonts, and the second radiation leading to the present-day biodiversity.
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Affiliation(s)
- Federico Plazzi
- Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi, 3 - 40126 Bologna, Italy
| | - Guglielmo Puccio
- Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi, 3 - 40126 Bologna, Italy
| | - Marco Passamonti
- Department of Biological, Geological and Environmental Sciences, University of Bologna, via Selmi, 3 - 40126 Bologna, Italy
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21
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Johnston IG, Williams BP. Evolutionary Inference across Eukaryotes Identifies Specific Pressures Favoring Mitochondrial Gene Retention. Cell Syst 2016; 2:101-11. [PMID: 27135164 DOI: 10.1016/j.cels.2016.01.013] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Revised: 12/14/2015] [Accepted: 01/27/2016] [Indexed: 11/18/2022]
Abstract
Since their endosymbiotic origin, mitochondria have lost most of their genes. Although many selective mechanisms underlying the evolution of mitochondrial genomes have been proposed, a data-driven exploration of these hypotheses is lacking, and a quantitatively supported consensus remains absent. We developed HyperTraPS, a methodology coupling stochastic modeling with Bayesian inference, to identify the ordering of evolutionary events and suggest their causes. Using 2015 complete mitochondrial genomes, we inferred evolutionary trajectories of mtDNA gene loss across the eukaryotic tree of life. We find that proteins comprising the structural cores of the electron transport chain are preferentially encoded within mitochondrial genomes across eukaryotes. A combination of high GC content and high protein hydrophobicity is required to explain patterns of mtDNA gene retention; a model that accounts for these selective pressures can also predict the success of artificial gene transfer experiments in vivo. This work provides a general method for data-driven inference of the ordering of evolutionary and progressive events, here identifying the distinct features shaping mitochondrial genomes of present-day species.
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Affiliation(s)
- Iain G Johnston
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK.
| | - Ben P Williams
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
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22
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Tischner C, Wenz T. Keep the fire burning: Current avenues in the quest of treating mitochondrial disorders. Mitochondrion 2015; 24:32-49. [DOI: 10.1016/j.mito.2015.06.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Revised: 06/18/2015] [Accepted: 06/24/2015] [Indexed: 12/18/2022]
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23
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Skippington E, Barkman TJ, Rice DW, Palmer JD. Miniaturized mitogenome of the parasitic plant Viscum scurruloideum is extremely divergent and dynamic and has lost all nad genes. Proc Natl Acad Sci U S A 2015; 112:E3515-24. [PMID: 26100885 PMCID: PMC4500244 DOI: 10.1073/pnas.1504491112] [Citation(s) in RCA: 183] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite the enormous diversity among parasitic angiosperms in form and structure, life-history strategies, and plastid genomes, little is known about the diversity of their mitogenomes. We report the sequence of the wonderfully bizarre mitogenome of the hemiparasitic aerial mistletoe Viscum scurruloideum. This genome is only 66 kb in size, making it the smallest known angiosperm mitogenome by a factor of more than three and the smallest land plant mitogenome. Accompanying this size reduction is exceptional reduction of gene content. Much of this reduction arises from the unexpected loss of respiratory complex I (NADH dehydrogenase), universally present in all 300+ other angiosperms examined, where it is encoded by nine mitochondrial and many nuclear nad genes. Loss of complex I in a multicellular organism is unprecedented. We explore the potential relationship between this loss in Viscum and its parasitic lifestyle. Despite its small size, the Viscum mitogenome is unusually rich in recombinationally active repeats, possessing unparalleled levels of predicted sublimons resulting from recombination across short repeats. Many mitochondrial gene products exhibit extraordinary levels of divergence in Viscum, indicative of highly relaxed if not positive selection. In addition, all Viscum mitochondrial protein genes have experienced a dramatic acceleration in synonymous substitution rates, consistent with the hypothesis of genomic streamlining in response to a high mutation rate but completely opposite to the pattern seen for the high-rate but enormous mitogenomes of Silene. In sum, the Viscum mitogenome possesses a unique constellation of extremely unusual features, a subset of which may be related to its parasitic lifestyle.
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Affiliation(s)
| | - Todd J Barkman
- Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008
| | - Danny W Rice
- Department of Biology, Indiana University, Bloomington, IN 47405
| | - Jeffrey D Palmer
- Department of Biology, Indiana University, Bloomington, IN 47405;
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24
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Nuclear expression of mitochondrial ND4 leads to the protein assembling in complex I and prevents optic atrophy and visual loss. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2015; 2:15003. [PMID: 26029714 PMCID: PMC4444999 DOI: 10.1038/mtm.2015.3] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 01/05/2015] [Accepted: 01/09/2015] [Indexed: 12/13/2022]
Abstract
Leber hereditary optic neuropathy is due to mitochondrial DNA mutations; in ~70% of all cases, a point mutation in the mitochondrial NADH dehydrogenase subunit 4, ND4, gene leads to central vision loss. We optimized allotopic expression (nuclear transcription of a gene that is normally transcribed inside the mitochondria) aimed at designing a gene therapy for ND4; its coding sequence was associated with the cis-acting elements of the human COX10 mRNA to allow the efficient mitochondrial delivery of the protein. After ocular administration to adult rats of a recombinant adeno-associated viral vector containing the human ND4 gene, we demonstrated that: (i) the sustained expression of human ND4 did not lead to harmful effects, instead the human protein is efficiently imported inside the mitochondria and assembled in respiratory chain complex I; (ii) the presence of the human protein in the experimental model of Leber hereditary optic neuropathy significantly prevents retinal ganglion cell degeneration and preserves both complex I function in optic nerves and visual function. Hence, the use of optimized allotopic expression is relevant for treating mitochondrial disorders due to mutations in the organelle genome.
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25
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Affiliation(s)
- Shinya Yoshikawa
- Picobiology Institute, Graduate
School of Life Science, University of Hyogo, Kamigohri Akoh Hyogo, 678-1297, Japan
| | - Atsuhiro Shimada
- Picobiology Institute, Graduate
School of Life Science, University of Hyogo, Kamigohri Akoh Hyogo, 678-1297, Japan
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26
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Pereira L, Soares P, Triska P, Rito T, van der Waerden A, Li B, Radivojac P, Samuels DC. Global human frequencies of predicted nuclear pathogenic variants and the role played by protein hydrophobicity in pathogenicity potential. Sci Rep 2014; 4:7155. [PMID: 25412673 PMCID: PMC4239565 DOI: 10.1038/srep07155] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 11/05/2014] [Indexed: 11/30/2022] Open
Abstract
Mitochondrial proteins are coded by nuclear (nDNA) and mitochondrial (mtDNA) genes, implying a complex cross-talk between the two genomes. Here we investigated the diversity displayed in 104 nuclear-coded mitochondrial proteins from 1,092 individuals from the 1000 Genomes dataset, in order to evaluate if these genes are under the effects of purifying selection and how that selection compares with their mitochondrial encoded counterparts. Only the very rare variants (frequency < 0.1%) in these nDNA genes are indistinguishable from a random set from all possible variants in terms of predicted pathogenicity score, but more frequent variants display distinct signs of purifying selection. Comparisons of selection strength indicate stronger selection in the mtDNA genes compared to this set of nDNA genes, accounted for by the high hydrophobicity of the proteins coded by the mtDNA. Most of the predicted pathogenic variants in the nDNA genes were restricted to a single continental population. The proportion of individuals having at least one potential pathogenic mutation in this gene set was significantly lower in Europeans than in Africans and Asians. This difference may reflect demographic asymmetries, since African and Asian populations experienced main expansions in middle Holocene, while in Europeans the main expansions occurred earlier in the post-glacial period.
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Affiliation(s)
- Luísa Pereira
- 1] Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto 4200-465, Portugal [2] Faculdade de Medicina da Universidade do Porto, Porto 4200-319, Portugal
| | - Pedro Soares
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto 4200-465, Portugal
| | - Petr Triska
- 1] Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto 4200-465, Portugal [2] Instituto de Ciências Biomédicas da Universidade do Porto (ICBAS), Porto 4050-313, Portugal
| | - Teresa Rito
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto 4200-465, Portugal
| | - Agnes van der Waerden
- Instituto de Patologia e Imunologia Molecular da Universidade do Porto (IPATIMUP), Porto 4200-465, Portugal
| | - Biao Li
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405, USA
| | - Predrag Radivojac
- School of Informatics and Computing, Indiana University, Bloomington, IN 47405, USA
| | - David C Samuels
- Center for Human Genetics Research, Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232-0700, USA
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27
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Yin LF, Wang F, Zhang Y, Kuang H, Schnabel G, Li GQ, Luo CX. Evolutionary analysis revealed the horizontal transfer of the Cyt b gene from Fungi to Chromista. Mol Phylogenet Evol 2014; 76:155-61. [DOI: 10.1016/j.ympev.2014.03.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 03/06/2014] [Accepted: 03/15/2014] [Indexed: 01/21/2023]
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28
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Gene therapy for mitochondrial diseases: Leber Hereditary Optic Neuropathy as the first candidate for a clinical trial. C R Biol 2014; 337:193-206. [PMID: 24702846 DOI: 10.1016/j.crvi.2013.11.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 11/28/2013] [Indexed: 12/30/2022]
Abstract
Mitochondrial disorders cannot be ignored anymore in most medical disciplines; indeed their minimum estimated prevalence is superior to 1 in 5000 births. Despite the progress made in the last 25 years on the identification of gene mutations causing mitochondrial pathologies, only slow progress was made towards their effective treatments. Ocular involvement is a frequent feature in mitochondrial diseases and corresponds to severe and irreversible visual handicap due to retinal neuron loss and optic atrophy. Interestingly, three clinical trials for Leber Congenital Amaurosis due to RPE65 mutations are ongoing since 2007. Overall, the feasibility and safety of ocular Adeno-Associated Virus delivery in adult and younger patients and consistent visual function improvements have been demonstrated. The success of gene-replacement therapy for RPE65 opens the way for the development of similar approaches for a broad range of eye disorders, including those with mitochondrial etiology such as Leber Hereditary Optic Neuropathy (LHON).
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29
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Vázquez-Acevedo M, Rubalcava-Gracia D, González-Halphen D. In vitro import and assembly of the nucleus-encoded mitochondrial subunit III of cytochrome c oxidase (Cox3). Mitochondrion 2014; 19 Pt B:314-22. [PMID: 24561572 DOI: 10.1016/j.mito.2014.02.005] [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: 12/10/2013] [Revised: 01/24/2014] [Accepted: 02/12/2014] [Indexed: 11/17/2022]
Abstract
The cox3 gene, encoding subunit III of cytochrome c oxidase (Cox3) is in mitochondrial genomes except in chlorophycean algae, where it is localized in the nucleus. Therefore, algae like Chlamydomonas reinhardtii, Polytomella sp. and Volvox carteri, synthesize the Cox3 polypeptide in the cytosol, import it into mitochondria, and integrate it into the cytochrome c oxidase complex. In this work, we followed the in vitro internalization of the Cox3 precursor by isolated, import-competent mitochondria of Polytomella sp. In this colorless alga, the precursor Cox3 protein is synthesized with a long, cleavable, N-terminal mitochondrial targeting sequence (MTS) of 98 residues. In an import time course, a transient Cox3 intermediate was identified, suggesting that the long MTS is processed more than once. The first processing step is sensitive to the metalo-protease inhibitor 1,10-ortophenantroline, suggesting that it is probably carried out by the matrix-located Mitochondrial Processing Protease. Cox3 is readily imported through an energy-dependent import pathway and integrated into the inner mitochondrial membrane, becoming resistant to carbonate extraction. Furthermore, the imported Cox3 protein was assembled into cytochrome c oxidase, as judged by the presence of a labeled band co-migrating with complex IV in Blue Native Electrophoresis. A model for the biogenesis of Cox3 in chlorophycean algae is proposed. This is the first time that the in vitro mitochondrial import of a cytosol-synthesized Cox3 subunit is described.
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Affiliation(s)
- Miriam Vázquez-Acevedo
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, México 04510, D.F., Mexico
| | - Diana Rubalcava-Gracia
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, México 04510, D.F., Mexico
| | - Diego González-Halphen
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-243, México 04510, D.F., Mexico.
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30
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Reithinger JH, Yim C, Park K, Björkholm P, von Heijne G, Kim H. A short C-terminal tail prevents mis-targeting of hydrophobic mitochondrial membrane proteins to the ER. FEBS Lett 2013; 587:3480-6. [PMID: 24055247 DOI: 10.1016/j.febslet.2013.08.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 08/28/2013] [Indexed: 10/26/2022]
Abstract
Sdh3/Shh3, a subunit of mitochondrial succinate dehydrogenase, contains transmembrane domains with a hydrophobicity comparable to that of endoplasmic reticulum (ER) proteins. Here, we show that a C-terminal reporter fusion to Sdh3/Shh3 results in partial mis-targeting of the protein to the ER. This mis-targeting is mediated by the signal recognition particle (SRP) and depends on the length of the C-terminal tail. These results imply that if nuclear-encoded mitochondrial proteins contain strongly hydrophobic transmembrane domains and a long C-terminal tail, they have the potential to be recognized by SRP and mis-targeted to the ER.
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Affiliation(s)
- Johannes H Reithinger
- School of Biological Sciences, Seoul National University, Seoul 151-747, South Korea; Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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31
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de Paula WBM, Lucas CH, Agip ANA, Vizcay-Barrena G, Allen JF. Energy, ageing, fidelity and sex: oocyte mitochondrial DNA as a protected genetic template. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120263. [PMID: 23754815 PMCID: PMC3685464 DOI: 10.1098/rstb.2012.0263] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Oxidative phosphorylation couples ATP synthesis to respiratory electron transport. In eukaryotes, this coupling occurs in mitochondria, which carry DNA. Respiratory electron transport in the presence of molecular oxygen generates free radicals, reactive oxygen species (ROS), which are mutagenic. In animals, mutational damage to mitochondrial DNA therefore accumulates within the lifespan of the individual. Fertilization generally requires motility of one gamete, and motility requires ATP. It has been proposed that oxidative phosphorylation is nevertheless absent in the special case of quiescent, template mitochondria, that these remain sequestered in oocytes and female germ lines and that oocyte mitochondrial DNA is thus protected from damage, but evidence to support that view has hitherto been lacking. Here we show that female gametes of Aurelia aurita, the common jellyfish, do not transcribe mitochondrial DNA, lack electron transport, and produce no free radicals. In contrast, male gametes actively transcribe mitochondrial genes for respiratory chain components and produce ROS. Electron microscopy shows that this functional division of labour between sperm and egg is accompanied by contrasting mitochondrial morphology. We suggest that mitochondrial anisogamy underlies division of any animal species into two sexes with complementary roles in sexual reproduction. We predict that quiescent oocyte mitochondria contain DNA as an unexpressed template that avoids mutational accumulation by being transmitted through the female germ line. The active descendants of oocyte mitochondria perform oxidative phosphorylation in somatic cells and in male gametes of each new generation, and the mutations that they accumulated are not inherited. We propose that the avoidance of ROS-dependent mutation is the evolutionary pressure underlying maternal mitochondrial inheritance and the developmental origin of the female germ line.
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Affiliation(s)
- Wilson B M de Paula
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
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32
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Cruz-Torres V, Vázquez-Acevedo M, García-Villegas R, Pérez-Martínez X, Mendoza-Hernández G, González-Halphen D. The cytosol-synthesized subunit II (Cox2) precursor with the point mutation W56R is correctly processed in yeast mitochondria to rescue cytochrome oxidase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:2128-39. [PMID: 22985601 DOI: 10.1016/j.bbabio.2012.09.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 09/01/2012] [Accepted: 09/07/2012] [Indexed: 01/07/2023]
Abstract
Deletion of the yeast mitochondrial gene COX2 encoding subunit 2 (Cox2) of cytochrome c oxidase (CcO) results in loss of respiration (Δcox2 strain). Supekova et al. (2010) [1] transformed a Δcox2 strain with a vector expressing Cox2 with a mitochondrial targeting sequence (MTS) and the point mutation W56R (Cox2(W56R)), restoring respiratory growth. Here, the CcO carrying the allotopically-expressed Cox2(W56R) was characterized. Yeast mitochondria from the wild-type (WT) and the Δcox2+Cox2(W56R) strains were subjected to Blue Native electrophoresis. In-gel activity of CcO and spectroscopic quantitation of cytochromes revealed that only 60% of CcO is present in the complemented strain, and that less CcO is found associated in supercomplexes as compared to WT. CcOs from the WT and the mutant exhibited similar subunit composition, although activity was 20-25% lower in the enzyme containing Cox2(W56R) than in the one with Cox2(WT). Tandem mass spectrometry confirmed that W(56) was substituted by R(56) in Cox2(W56R). In addition, Cox2(W56R) exhibited the same N-terminus than Cox2(WT), indicating that the MTS of Oxa1 and the leader sequence of 15 residues were removed from Cox2(W56R) during maturation. Thus, Cox2(W56R) is identical to Cox2(WT) except for the point mutation W56R. Mitochondrial Cox1 synthesis is strongly reduced in Δcox2 mutants, but the Cox2(W56R) complemented strain led to full restoration of Cox1 synthesis. We conclude that the cytosol-synthesized Cox2(W56R) follows a rate-limiting process of import, maturation or assembly that yields lower steady-state levels of CcO. Still, the allotopically-expressed Cox2(W56R) restores CcO activity and allows mitochondrial Cox1 synthesis to advance at WT levels.
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Affiliation(s)
- Valentín Cruz-Torres
- Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México D.F., Mexico
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Cuenca A, Petersen G, Seberg O, Jahren AH. Genes and processed paralogs co-exist in plant mitochondria. J Mol Evol 2012; 74:158-69. [PMID: 22484699 DOI: 10.1007/s00239-012-9496-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Accepted: 03/23/2012] [Indexed: 10/28/2022]
Abstract
RNA-mediated gene duplication has been proposed to create processed paralogs in the plant mitochondrial genome. A processed paralog may retain signatures left by the maturation process of its RNA precursor, such as intron removal and no need of RNA editing. Whereas it is well documented that an RNA intermediary is involved in the transfer of mitochondrial genes to the nucleus, no direct evidence exists for insertion of processed paralogs in the mitochondria (i.e., processed and un-processed genes have never been found simultaneously in the mitochondrial genome). In this study, we sequenced a region of the mitochondrial gene nad1, and identified a number of taxa were two different copies of the region co-occur in the mitochondria. The two nad1 paralogs differed in their (a) presence or absence of a group II intron, and (b) number of edited sites. Thus, this work provides the first evidence of co-existence of processed paralogs and their precursors within the plant mitochondrial genome. In addition, mapping the presence/absence of the paralogs provides indirect evidence of RNA-mediated gene duplication as an essential process shaping the mitochondrial genome in plants.
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Affiliation(s)
- Argelia Cuenca
- Botanical Garden, Natural History Museum of Denmark, University of Copenhagen, Sølvgade 83 Opg. S, 1307, Copenhagen K, Denmark.
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Herrmann JM, Woellhaf MW, Bonnefoy N. Control of protein synthesis in yeast mitochondria: the concept of translational activators. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:286-94. [PMID: 22450032 DOI: 10.1016/j.bbamcr.2012.03.007] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 03/01/2012] [Accepted: 03/08/2012] [Indexed: 12/18/2022]
Abstract
Mitochondria contain their own genome which codes for a small number of proteins. Most mitochondrial translation products are part of the membrane-embedded reaction centers of the respiratory chain complexes. In the yeast Saccharomyces cerevisiae, the expression of these proteins is regulated by translational activators that bind mitochondrial mRNAs, in most cases to their 5'-untranslated regions, and each mitochondrial mRNA appears to have its own translational activator(s). Recent studies showed that these translational activators can be part of feedback control loops which only permit translation if the downstream assembly of nascent translation products can occur. In several cases, the accumulation of a non-assembled protein prevents further synthesis of this protein but not translation in general. These control loops prevent the synthesis of potentially harmful assembly intermediates of the reaction centers of mitochondrial enzymes. Since such regulatory feedback loops only work if translation occurs in the compartment in which the complexes of the respiratory chain are assembled, these control mechanisms require the presence of a translation machinery in mitochondria. This might explain why eukaryotic cells maintained DNA in mitochondria during the last two billion years of evolution. This review gives an overview of the mitochondrial translation system and summarizes the current knowledge on translational activators and their role in the regulation of mitochondrial protein synthesis. This article is part of a Special Issue entitled: Protein import and quality control in mitochondria and plastids.
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Affiliation(s)
- Johannes M Herrmann
- Cell Biology, Erwin-Schrödinger-Strasse 13, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
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Modulation of mitochondrial respiratory capacity by carrier-mediated transfer of RNA in vivo. Mitochondrion 2012; 12:262-70. [DOI: 10.1016/j.mito.2011.10.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 09/05/2011] [Accepted: 10/10/2011] [Indexed: 11/22/2022]
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Hydrogenosomes and Mitosomes: Mitochondrial Adaptations to Life in Anaerobic Environments. CELLULAR ORIGIN, LIFE IN EXTREME HABITATS AND ASTROBIOLOGY 2012. [DOI: 10.1007/978-94-007-1896-8_5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Abstract
Depending on the organism, mitochondria consist approximately of 500-1,400 different proteins. By far most of these proteins are encoded by nuclear genes and synthesized on cytosolic ribosomes. Targeting signals direct these proteins into mitochondria and there to their respective subcompartment: the outer membrane, the intermembrane space (IMS), the inner membrane, and the matrix. Membrane-embedded translocation complexes allow the translocation of proteins across and, in the case of membrane proteins, the insertion into mitochondrial membranes. A small number of proteins are encoded by the mitochondrial genome: Most mitochondrial translation products represent hydrophobic proteins of the inner membrane which-together with many nuclear-encoded proteins-form the respiratory chain complexes. This chapter gives an overview on the mitochondrial protein translocases and the mechanisms by which they drive the transport and assembly of mitochondrial proteins.
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Adhya S, Mahato B, Jash S, Koley S, Dhar G, Chowdhury T. Mitochondrial gene therapy: The tortuous path from bench to bedside. Mitochondrion 2011; 11:839-44. [DOI: 10.1016/j.mito.2011.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 05/12/2011] [Accepted: 06/10/2011] [Indexed: 01/25/2023]
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Cwerman-Thibault H, Sahel JA, Corral-Debrinski M. Mitochondrial medicine: to a new era of gene therapy for mitochondrial DNA mutations. J Inherit Metab Dis 2011; 34:327-44. [PMID: 20571866 DOI: 10.1007/s10545-010-9131-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 05/12/2010] [Accepted: 05/17/2010] [Indexed: 01/01/2023]
Abstract
Mitochondrial disorders can no longer be ignored in most medical disciplines. Such disorders include specific and widespread organ involvement, with tissue degeneration or tumor formation. Primary or secondary actors, mitochondrial dysfunctions also play a role in the aging process. Despite progresses made in identification of their molecular bases, nearly everything remains to be done as regards therapy. Research dealing with mitochondrial physiology and pathology has >20 years of history around the world. We are involved, as are many other laboratories, in the challenge of finding ways to fight these diseases. However, our main limitation is the scarcety of animal models required for both understanding the molecular mechanisms underlying the diseases and evaluating therapeutic strategies. This is especially true for diseases due to mutations in mitochondrial DNA (mtDNA), since an authentic genetic model of mtDNA mutations is technically a very difficult task due to both the inability of manipulating the mitochondrial genome of living mammalian cells and to its multicopy nature. This has led researchers in the field to consider the prospect of gene therapy approaches that can roughly be divided into three groups: (1) import of wild-type copies or relevant sections of DNA or RNA into mitochondria, (2) manipulation of mitochondrial genetic content, and (3) rescue of a defect by expression of an engineered gene product from the nucleus (allotopic or xenotropic expression). We briefly introduce these concepts and indicate where promising progress has been made in the last decade.
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RNA-mediated restoration of mitochondrial function in cells harboring a Kearns Sayre Syndrome mutation. Mitochondrion 2011; 11:564-74. [PMID: 21406250 DOI: 10.1016/j.mito.2011.03.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 03/03/2011] [Indexed: 11/20/2022]
Abstract
Mutations in mitochondrial DNA (mtDNA) generate multi-system disorders due to failure of ATP production. A cybrid containing a 1.9-kb mtDNA deletion from a patient with Kearns Sayre Syndrome is respiration-defective and grows glycolytically. When treated with a ribonucleoprotein (RNP) complex of polycistronic RNA 1 (pcRNA1) containing mtDNA-encoded genes and a multi-subunit carrier complex R8, full-length pcRNA1 was transported to mitochondria. Translation of the pcRNA1-encoded mRNAs was observed in mitochondria from RNP-treated cells. Respiration of the cybrid was rescued to approximately 90% of normal within hours, switching the cells to aerobic growth. These findings have implications for the development of effective mitochondrial gene therapy.
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Mitochondrial RNA import: from diversity of natural mechanisms to potential applications. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 287:145-90. [PMID: 21414588 DOI: 10.1016/b978-0-12-386043-9.00004-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mitochondria, owing to their bacterial origin, still contain their own DNA. However, the majority of bacterial genes were lost or transferred to the nuclear genome and the biogenesis of the "present-day" mitochondria mainly depends on the expression of the nuclear genome. Thus, most mitochondrial proteins and a small number of mitochondrial RNAs (mostly tRNAs) expressed from nuclear genes need to be imported into the organelle. During evolution, macromolecule import systems were universally established. The processes of protein mitochondrial import are very well described in the literature. By contrast, deciphering the mitochondrial RNA import phenomenon is still a real challenge. The purpose of this review is to present a general survey of our present knowledge in this field in different model organisms, protozoa, plants, yeast, and mammals. Questions still under debate and major challenges are discussed. Mitochondria are involved in numerous human diseases. The targeting of macromolecule to mitochondria represents a promising way to fight mitochondrial disorders and recent developments in this area of research are presented.
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Leister D, Kleine T. Role of intercompartmental DNA transfer in producing genetic diversity. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 291:73-114. [PMID: 22017974 DOI: 10.1016/b978-0-12-386035-4.00003-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In eukaryotic cells, genes are found in three compartments-the nucleus, mitochondria, and plastids-and extensive gene transfer has occurred between them. Most organellar genes in the nucleus migrated there long ago, but transfer is ongoing and ubiquitous. It now generates mostly noncoding nuclear DNA, can also disrupt gene functions, and reshape genes by adding novel exons. Plastid or nuclear sequences have also contributed to the formation of mitochondrial tRNA genes. It is now clear that organelle-to-nucleus DNA transfer involves the escape of DNA molecules from the organelles at times of stress or at certain developmental stages, and their subsequent incorporation at sites of double-stranded breaks in nuclear DNA by nonhomologous recombination. Intercompartmental DNA transfer thus appears to be an inescapable phenomenon that has had a broad impact on eukaryotic evolution, affecting DNA repair, gene and genome evolution, and redirecting proteins to different target compartments.
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Affiliation(s)
- Dario Leister
- Lehrstuhl für Molekularbiologie der Pflanzen, Department Biologie I, Ludwig-Maximilians-Universität München-LMU, Planegg-Martinsried, Germany
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Tong J, Dolezal P, Selkrig J, Crawford S, Simpson AGB, Noinaj N, Buchanan SK, Gabriel K, Lithgow T. Ancestral and derived protein import pathways in the mitochondrion of Reclinomonas americana. Mol Biol Evol 2010; 28:1581-91. [PMID: 21081480 DOI: 10.1093/molbev/msq305] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The evolution of mitochondria from ancestral bacteria required that new protein transport machinery be established. Recent controversy over the evolution of these new molecular machines hinges on the degree to which ancestral bacterial transporters contributed during the establishment of the new protein import pathway. Reclinomonas americana is a unicellular eukaryote with the most gene-rich mitochondrial genome known, and the large collection of membrane proteins encoded on the mitochondrial genome of R. americana includes a bacterial-type SecY protein transporter. Analysis of expressed sequence tags shows R. americana also has components of a mitochondrial protein translocase or "translocase in the inner mitochondrial membrane complex." Along with several other membrane proteins encoded on the mitochondrial genome Cox11, an assembly factor for cytochrome c oxidase retains sequence features suggesting that it is assembled by the SecY complex in R. americana. Despite this, protein import studies show that the RaCox11 protein is suited for import into mitochondria and functional complementation if the gene is transferred into the nucleus of yeast. Reclinomonas americana provides direct evidence that bacterial protein transport pathways were retained, alongside the evolving mitochondrial protein import machinery, shedding new light on the process of mitochondrial evolution.
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Affiliation(s)
- Janette Tong
- Department of Biochemistry & Molecular Biology, Monash University, Clayton, Australia
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Figueroa-Martínez F, Vázquez-Acevedo M, Cortés-Hernández P, García-Trejo JJ, Davidson E, King MP, González-Halphen D. What limits the allotopic expression of nucleus-encoded mitochondrial genes? The case of the chimeric Cox3 and Atp6 genes. Mitochondrion 2010; 11:147-54. [PMID: 20854934 DOI: 10.1016/j.mito.2010.09.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2010] [Revised: 08/17/2010] [Accepted: 09/10/2010] [Indexed: 10/19/2022]
Abstract
Allotopic expression is potentially a gene therapy for mtDNA-related diseases. Some OXPHOS proteins like ATP6 (subunit a of complex V) and COX3 (subunit III of complex IV) that are typically mtDNA-encoded, are naturally nucleus-encoded in the alga Chlamydomonas reinhardtii. The mitochondrial proteins whose genes have been relocated to the nucleus exhibit long mitochondrial targeting sequences ranging from 100 to 140 residues and a diminished overall mean hydrophobicity when compared with their mtDNA-encoded counterparts. We explored the allotopic expression of the human gene products COX3 and ATP6 that were re-designed for mitochondrial import by emulating the structural properties of the corresponding algal proteins. In vivo and in vitro data in homoplasmic human mutant cells carrying either a T8993G mutation in the mitochondrial atp6 gene or a 15bp deletion in the mtDNA-encoded cox3 gene suggest that these human mitochondrial proteins re-designed for nuclear expression are targeted to the mitochondria, but fail to functionally integrate into their corresponding OXPHOS complexes.
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Perales-Clemente E, Fernández-Silva P, Acín-Pérez R, Pérez-Martos A, Enríquez JA. Allotopic expression of mitochondrial-encoded genes in mammals: achieved goal, undemonstrated mechanism or impossible task? Nucleic Acids Res 2010; 39:225-34. [PMID: 20823090 PMCID: PMC3017613 DOI: 10.1093/nar/gkq769] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Mitochondrial-DNA diseases have no effective treatments. Allotopic expression—synthesis of a wild-type version of the mutated protein in the nuclear-cytosolic compartment and its importation into mitochondria—has been proposed as a gene-therapy approach. Allotopic expression has been successfully demonstrated in yeast, but in mammalian mitochondria results are contradictory. The evidence available is based on partial phenotype rescue, not on the incorporation of a functional protein into mitochondria. Here, we show that reliance on partial rescue alone can lead to a false conclusion of successful allotopic expression. We recoded mitochondrial mt-Nd6 to the universal genetic code, and added the N-terminal mitochondrial-targeting sequence of cytochrome c oxidase VIII (C8) and the HA epitope (C8Nd6HA). The protein apparently co-localized with mitochondria, but a significant part of it seemed to be located outside mitochondria. Complex I activity and assembly was restored, suggesting successful allotopic expression. However, careful examination of transfected cells showed that the allotopically-expressed protein was not internalized in mitochondria and that the selected clones were in fact revertants for the mt-Nd6 mutation. These findings demonstrate the need for extreme caution in the interpretation of functional rescue experiments and for clear-cut controls to demonstrate true rescue of mitochondrial function by allotopic expression.
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Affiliation(s)
- Ester Perales-Clemente
- Centro Nacional de Investigaciónes Cardiovasculares Carlos III, Melchor Fernández Almagro, Madrid, Spain
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Allen JF. Why chloroplasts and mitochondria contain genomes. Comp Funct Genomics 2010; 4:31-6. [PMID: 18629105 PMCID: PMC2447392 DOI: 10.1002/cfg.245] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2002] [Accepted: 11/25/2002] [Indexed: 11/05/2022] Open
Abstract
Chloroplasts and mitochondria originated as bacterial symbionts. The larger, host
cells acquired genetic information from their prokaryotic guests by lateral gene
transfer. The prokaryotically-derived genes of the eukaryotic cell nucleus now
function to encode the great majority of chloroplast and mitochondrial proteins,
as well as many proteins of the nucleus and cytosol. Genes are copied and moved
between cellular compartments with relative ease, and there is no established obstacle
to successful import of any protein precursor from the cytosol. Yet chloroplasts and
mitochondria have not abdicated all genes and gene expression to the nucleus and
to cytosolic translation. What, then, do chloroplast- and mitochondrially-encoded
proteins have in common that confers a selective advantage on the cytoplasmic
location of their genes? The proposal advanced here is that co-location of chloroplast
and mitochondrial genes with their gene products is required for rapid and direct
regulatory coupling. Redox control of gene expression is suggested as the common
feature of those chloroplast and mitochondrial proteins that are encoded in situ.
Recent evidence is consistent with this hypothesis, and its underlying assumptions
and predictions are described.
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Affiliation(s)
- John F Allen
- Plant Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, Lund SE-221 00, Sweden.
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Repositioning of transmembrane alpha-helices during membrane protein folding. J Mol Biol 2010; 397:190-201. [PMID: 20109468 DOI: 10.1016/j.jmb.2010.01.042] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 01/19/2010] [Accepted: 01/19/2010] [Indexed: 11/30/2022]
Abstract
We have determined the optimal placement of individual transmembrane helices in the Pyrococcus horikoshii Glt(Ph) glutamate transporter homolog in the membrane. The results are in close agreement with theoretical predictions based on hydrophobicity, but do not, in general, match the known three-dimensional structure, suggesting that transmembrane helices can be repositioned relative to the membrane during folding and oligomerization. Theoretical analysis of a database of membrane protein structures provides additional support for this idea. These observations raise new challenges for the structure prediction of membrane proteins and suggest that the classical two-stage model often used to describe membrane protein folding needs to be modified.
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Ott M, Herrmann JM. Co-translational membrane insertion of mitochondrially encoded proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1803:767-75. [PMID: 19962410 DOI: 10.1016/j.bbamcr.2009.11.010] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2009] [Revised: 11/18/2009] [Accepted: 11/25/2009] [Indexed: 11/29/2022]
Abstract
The components of the mitochondrial proteome represent a mosaic of dual genetic origin: while most mitochondrial proteins are encoded by nuclear genes and imported into the organelle following synthesis in the cytosol, a small number of proteins is encoded by the mitochondrial genome. Though small in number, mitochondrial translation products are vital for cellular functionality as these proteins represent the core subunits of the respiratory chain and the ATPase which produce the vast majority of the cellular ATP. Mitochondrial translation products are almost exclusively highly hydrophobic polypeptides which are inserted into the inner membrane in the course of their synthesis. The machinery that mediates membrane insertion in mitochondria is deduced from that of their bacterial ancestors and hence shows profound similarities to the insertion machinery of prokaryotes. However, the specialization on the production of a very small set of translation products drove a severe reduction in the complexity of this system. The insertase Oxa1 forms the central component of the insertion machinery. Oxa1 directly binds to mitochondrial ribosomes and, together with the inner membrane protein Mba1, aligns the polypeptide exit tunnel of the ribosome with the insertion site at the inner membrane. The specific hallmarks and the critical components of this machinery are discussed in this review article.
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Affiliation(s)
- Martin Ott
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
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Sologub MY, Kochetkov SN, Temiakov DE. Transcription and its regulation in mammalian and human mitochondria. Mol Biol 2009. [DOI: 10.1134/s0026893309020034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Protein complexes in bacterial and yeast mitochondrial membranes differ in their sensitivity towards dissociation by SDS. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:2012-8. [PMID: 18817900 DOI: 10.1016/j.bbapap.2008.08.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 08/20/2008] [Accepted: 08/22/2008] [Indexed: 11/22/2022]
Abstract
Previously, a 2D gel electrophoresis approach was developed for the Escherichia coli inner membrane, which detects membrane protein complexes that are stable in sodium dodecyl sulfate (SDS) at room temperature, and dissociate under the influence of trifluoroethanol [R. E. Spelbrink et al., J. Biol. Chem. 280 (2005), 28742-8]. Here, the method was applied to the evolutionarily related mitochondrial inner membrane that was isolated from the yeast Saccharomyces cerevisiae. Surprisingly, only very few proteins were found to be dissociated by trifluoroethanol of which Lpd1p, a component of multiple protein complexes localized in the mitochondrial matrix, is the most prominent. Usage of either milder or more stringent conditions did not yield any additional proteins that were released by fluorinated alcohols. This strongly suggests that membrane protein complexes in yeast are less stable in SDS solution than their E. coli counterparts, which might be due to the overall reduced hydrophobicity of mitochondrial transmembrane proteins.
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