scholarly journals Mitochondrial transcription and translation: overview

2018 ◽  
Vol 62 (3) ◽  
pp. 309-320 ◽  
Author(s):  
Aaron R. D’Souza ◽  
Michal Minczuk
Keyword(s):  
Gene Expression ◽  
Mitochondrial Genome ◽  
Oxidative Phosphorylation ◽  
Mitochondrial Diseases ◽  
Mitochondrial Transcription ◽  
Inner Membrane ◽  
Atp Production

Mitochondria are the major source of ATP in the cell. Five multi-subunit complexes in the inner membrane of the organelle are involved in the oxidative phosphorylation required for ATP production. Thirteen subunits of these complexes are encoded by the mitochondrial genome often referred to as mtDNA. For this reason, the expression of mtDNA is vital for the assembly and functioning of the oxidative phosphorylation complexes. Defects of the mechanisms regulating mtDNA gene expression have been associated with deficiencies in assembly of these complexes, resulting in mitochondrial diseases. Recently, numerous factors involved in these processes have been identified and characterized leading to a deeper understanding of the mechanisms that underlie mitochondrial diseases.

scholarly journals Epilepsy in Mitochondrial Diseases—Current State of Knowledge on Aetiology and Treatment

Children ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 532
Author(s):  
Dorota Wesół-Kucharska ◽  
Dariusz Rokicki ◽  
Aleksandra Jezela-Stanek
Keyword(s):  
Oxidative Phosphorylation ◽  
Mitochondrial Dysfunction ◽  
Mitochondrial Disease ◽  
Clinical Picture ◽  
Poor Prognosis ◽  
Treatment Options ◽  
Mitochondrial Diseases ◽  
Energy Deficit ◽  
Atp Production ◽  
Current State

Mitochondrial diseases are a heterogeneous group of diseases resulting from energy deficit and reduced adenosine triphosphate (ATP) production due to impaired oxidative phosphorylation. The manifestation of mitochondrial disease is usually multi-organ. Epilepsy is one of the most common manifestations of diseases resulting from mitochondrial dysfunction, especially in children. The onset of epilepsy is associated with poor prognosis, while its treatment is very challenging, which further adversely affects the course of these disorders. Fortunately, our knowledge of mitochondrial diseases is still growing, which gives hope for patients to improve their condition in the future. The paper presents the pathophysiology, clinical picture and treatment options for epilepsy in patients with mitochondrial disease.

Dual Mutations Reveal Interactions Between Components of Oxidative Phosphorylation in Kluyveromyces lactis

Genetics ◽  
2001 ◽  
Vol 159 (3) ◽  
pp. 929-938
Author(s):  
G D Clark-Walker ◽  
X J Chen
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Atp Synthase ◽  
Kluyveromyces Lactis ◽  
Mitochondrial Protein ◽  
Proton Pumping ◽  
Nuclear Genes ◽  
Suppressor Activity ◽  
Inner Membrane ◽  
Atp Production

Abstract Loss of mtDNA or mitochondrial protein synthesis cannot be tolerated by wild-type Kluyveromyces lactis. The mitochondrial function responsible for ρ0-lethality has been identified by disruption of nuclear genes encoding electron transport and F0-ATP synthase components of oxidative phosphorylation. Sporulation of diploid strains heterozygous for disruptions in genes for the two components of oxidative phosphorylation results in the formation of nonviable spores inferred to contain both disruptions. Lethality of spores is thought to result from absence of a transmembrane potential, ΔΨ, across the mitochondrial inner membrane due to lack of proton pumping by the electron transport chain or reversal of F1F0-ATP synthase. Synergistic lethality, caused by disruption of nuclear genes, or ρ0-lethality can be suppressed by the atp2.1 mutation in the β-subunit of F1-ATPase. Suppression is viewed as occurring by an increased hydrolysis of ATP by mutant F1, allowing sufficient electrogenic exchange by the translocase of ADP in the matrix for ATP in the cytosol to maintain ΔΨ. In addition, lethality of haploid strains with a disruption of AAC encoding the ADP/ATP translocase can be suppressed by atp2.1. In this case suppression is considered to occur by mutant F1 acting in the forward direction to partially uncouple ATP production, thereby stimulating respiration and relieving detrimental hyperpolarization of the inner membrane. Participation of the ADP/ATP translocase in suppression of ρ0-lethality is supported by the observation that disruption of AAC abolishes suppressor activity of atp2.1.

The Multiple Levels of Mitonuclear Coregulation

2018 ◽  
Vol 52 (1) ◽  
pp. 511-533 ◽  
Author(s):  
R. Stefan Isaac ◽  
Erik McShane ◽  
L. Stirling Churchman
Keyword(s):  
Gene Expression ◽  
Oxidative Phosphorylation ◽  
Protein Degradation ◽  
Current Understanding ◽  
Mitochondrial Genomes ◽  
Expression Systems ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Optimal Function ◽  
Multiple Levels

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.

Targeting Dinitrophenol to Mitochondria: Limitations to the Development of a Self-limiting Mitochondrial Protonophore

2006 ◽  
Vol 26 (3) ◽  
pp. 231-243 ◽  
Author(s):  
Frances H. Blaikie ◽  
Stephanie E. Brown ◽  
Linda M. Samuelsson ◽  
Martin D. Brand ◽  
Robin A. J. Smith ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Membrane Potential ◽  
Oxidative Phosphorylation ◽  
Atp Synthesis ◽  
Proton Leak ◽  
Protonmotive Force ◽  
Inner Membrane ◽  
Atp Production ◽  
Mitochondrial Inner Membrane ◽  
Predominant Component

The protonmotive force (Δp) across the mitochondrial inner membrane drives ATP synthesis. In addition, the energy stored in Δp can be dissipated by proton leak through the inner membrane, contributing to basal metabolic rate and thermogenesis. Increasing mitochondrial proton leak pharmacologically should decrease the efficiency of oxidative phosphorylation and counteract obesity by enabling fatty acids to be oxidised with decreased ATP production. While protonophores such as 2,4-dinitrophenol (DNP) increase mitochondrial proton leak and have been used to treat obesity, a slight increase in DNP concentration above the therapeutically effective dose disrupts mitochondrial function and leads to toxicity. Therefore we set out to develop a less toxic protonophore that would increase proton leak significantly at high Δp but not at low Δp. Our design concept for a potential self-limiting protonophore was to couple the DNP moiety to the lipophilic triphenylphosphonium (TPP) cation and this was achieved by the preparation of 3-(3,5-dinitro-4-hydroxyphenyl)propyltriphenylphosphonium methanesulfonate (MitoDNP). TPP cations accumulate within mitochondria driven by the membrane potential (Δψ), the predominant component of Δp. Our hypothesis was that MitoDNP would accumulate in mitochondria at high Δψ where it would act as a protonophore, but that at lower Δψ the accumulation and uncoupling would be far less. We found that MitoDNP was extensively taken into mitochondria driven by Δψ. However MitoDNP did not uncouple mitochondria as judged by its inability to either increase respiration rate or decrease Δψ. Therefore MitoDNP did not act as a protonophore, probably because the efflux of deprotonated MitoDNP was inhibited.

scholarly journals Degradation of ATFS-1 by LONP-1 promotes deleterious mitochondrial genome heteroplasmy

2020 ◽  
Author(s):  
Qiyuan Yang ◽  
Pengpeng Liu ◽  
YunGuang Du ◽  
Kevin Luk ◽  
Nadine S. Anderson ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Mitochondrial Genome ◽  
Oxidative Phosphorylation ◽  
Mitochondrial Function ◽  
Mitochondrial Diseases ◽  
Mitochondrial Genomes ◽  
Wild Type ◽  
C Elegans ◽  
Promote Cell Survival ◽  
Transcription Program

AbstractThe accumulation of deleterious mitochondrial genomes (ΔmtDNAs) underlies inherited mitochondrial diseases and contributes to the aging-associated decline in mitochondrial function. Heteroplasmy occurs when a ΔmtDNA expands, ultimately causing a decline in oxidative phosphorylation (OXPHOS) function. In response to mitochondrial perturbations, the transcription factor ATFS-1 induces a transcription program to promote cell survival and recovery of mitochondrial function. Paradoxically, ATFS-1 is also required to maintain ΔmtDNAs in heteroplasmic worms. However, the mechanism(s) by which ATFS-1 promotes ΔmtDNA propagation relative to wild-type mtDNAs is unclear. Here, we show that mitochondrial-localized ATFS-1 binds almost exclusively to ΔmtDNAs in heteroplasmic worms and promotes binding of the mtDNA replicative polymerase (POLG). Interestingly, inhibition of the mtDNA-bound protease LONP-1 caused ATFS-1 and POLG to bind equally to ΔmtDNAs and wild-type mtDNAs. Furthermore, LONP-1 inhibition in C. elegans and human cybrid cells improved the heteroplasmy ratio and restored OXPHOS function. Our findings suggest that degradation of ATFS-1 within functional mitochondria by LONP-1 establishes the enriched interaction between ATFS-1 and ΔmtDNAs required to maintain heteroplasmy.One Sentence SummaryThe mitochondrial protease LONP1 regulates deleterious mitochondrial genome propagation.

scholarly journals Over Expression of NOS2 in Ragged-red Fibers from Patients with Mitochondrial Disorders due to Mutations in mtDNA

2018 ◽  
Vol 1 (1) ◽  
pp. 07-13
Author(s):  
Valeria Guglielmi ◽  
Matteo Marini ◽  
Giuliano Tomelleri ◽  
Gaetano Vattemi
Keyword(s):  
Nitric Oxide ◽  
Oxidative Phosphorylation ◽  
Subcellular Localization ◽  
Mitochondrial Diseases ◽  
Mitochondrial Respiratory Chain ◽  
Atp Production ◽  
Over Expression ◽  
Ragged Red Fibers ◽  
Muscle Biopsies ◽  
Inducible Nos

Mitochondrial diseases (MDs) are a group of heterogeneous disorders due to impaired oxidative phosphorylation causing defective ATP production. The histopathological hallmark is the presence ofragged-red fibers (RRFs), muscle fibers with excessive mitochondrial proliferation. Nitric oxide synthases (NOSs) are enzymes responsible of the synthesis of nitric oxide (NO), a ubiquitous signaling molecule involved in many physio-pathological processes. Three NOS isoenzymes have been identified so far including neuronal NOS (NOS1), inducible NOS (NOS2) and endothelial NOS (NOS3). Despite the expression and the subcellular localization of NOS1 and NOS3 have been previously investigated, a possible involvement of NOS2 in MDs has never been assessed. We evaluated the expression of NOS2 in muscle biopsies from 17 patients with mitochondrial respiratory chain dysfunction. Our data demonstrate that NOS2 is overexpressed in RRFs and the correspondence between NOS2 immunoreactivity and SDH staining suggests that the protein localizes to the mitochondria. Together with previous studies from the literature, these findings indicate a possible role NOSs in the pathogenic events leading to MDs

scholarly journals Nuclear and mitochondrial genome responses in HeLa cells treated with inhibitors of mitochondrial DNA expression.

2006 ◽  
Vol 53 (3) ◽  
pp. 485-495 ◽  
Author(s):  
Janusz Piechota ◽  
Roman Szczesny ◽  
Kamila Wolanin ◽  
Aleksander Chlebowski ◽  
Ewa Bartnik
Keyword(s):  
Mitochondrial Dna ◽  
Mitochondrial Genome ◽  
Oxidative Phosphorylation ◽  
Hela Cells ◽  
Transcription Initiation ◽  
Copy Number ◽  
Mitochondrial Haplotype ◽  
Mtdna Copy Number ◽  
Atp Production ◽  
Bioenergetic Metabolism

The influence of mutations in the mitochondrial DNA (mtDNA) on the bioenergetic metabolism of the cell is still poorly understood. Many of the mutations in the mtDNA affect the expression of the mitochondrial genome. Investigations on cells from patients are not easy, especially as the mitochondrial DNA is heteroplasmic and this state is changed in culture. Moreover, the nuclear background and the mitochondrial haplotype may affect the behaviour of cells. Transfer of patient mitochondria to rho zero cell lines is also not optimal as these cells in general have many nuclear changes which may also affect cell behaviour. Thus, we decided to use inhibitors of mitochondrial genome expression, such as thiamphenicol, ethidium bromide and dideoxycytidine to investigate the bioenergetic metabolism of HeLa cells. We found that oxidative phosphorylation and glycolysis participate equally in ATP production in HeLa cells and that decreased activity of the respiratory chain leads to increased glycolysis and the reduction of cell growth. Insufficient ATP production in the oxidative phosphorylation process was not compensated by increased proliferation of the mitochondria. However, we were able to show that there are some mechanisms compensating limited expression of the mitochondrial genome within the mitochondria. Experiments with dideoxycytidine revealed that 10-fold decrease of the mtDNA copy number resulted in almost normal activity of cytochrome c oxidase. We found that mtDNA depletion is compensated mostly on the level of RNA metabolism in the mitochondria. Thus, our results are in agreement with the hypothesis that transcription initiation rather than mtDNA copy number is a rate limiting factor for expression of the mitochondrial genome.

The Oral Intake of Organic Germanium, Ge-132, Elevates α-Tocopherol Levels in the Plas-ma and Modulates Hepatic Gene Expression Profiles to Promote Immune Activation in Mice

2014 ◽  
Vol 84 (3-4) ◽  
pp. 0183-0195 ◽  
Author(s):  
Takashi Nakamura ◽  
Tomoya Takeda ◽  
Yoshihiko Tokuji
Keyword(s):  
Gene Expression ◽  
Immune Activation ◽  
Expression Profiles ◽  
Water Soluble ◽  
Alpha Tocopherol ◽  
Hepatic Gene Expression ◽  
Tocopherol Concentration ◽  
Altered Expression ◽  
Atp Production ◽  
Transfer Protein

The common water-soluble organic germanium compound poly-trans-[(2-carboxyethyl) germasesquioxane] (Ge-132) exhibits activities related to immune responses and antioxidant induction. In this study, we evaluated the antioxidative effect of dietary Ge-132 in the plasma of mice. Male ICR mice (seven mice per group) received an AIN-76 diet with 0.05 % Ge-132; three groups received the Ge-132-containing diet for 0, 1 or 4 days. The plasma alpha-tocopherol (α-tocopherol) concentration increased from 6.85 to 9.60 μg/ml after 4 days of Ge-132 intake (p < 0.05). We evaluated the changes in hepatic gene expression related to antioxidative activity as well as in the entire expression profile after one day of Ge-132 intake, using DNA microarray technology. We identified 1,220 genes with altered expression levels greater than 1.5-fold (increased or decreased) as a result of Ge-132 intake, and α-tocopherol transfer protein (Ttpa) gene expression was increased 1.62-fold. Immune activation was identified as the category with the most changes (containing 60 Gene Ontology (GO) term biological processes (BPs), 41 genes) via functional clustering analysis of altered gene expression. Ge-132 affected genes in clusters related to ATP production (22 GO term BPs, 21 genes), lipid metabolism (4 GO term BPs, 38 genes) and apoptosis (5 GO term BPs). Many GO term BPs containing these categories were significantly affected by the Ge-132 intake. Oral Ge-132 intake may therefore have increased plasma α-tocopherol levels by up-regulating α-tocopherol transfer protein (Ttpa) gene expression.

scholarly journals Nanoscopic quantification of sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells derived from patients with mitochondrial diseases

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Weiwei Zou ◽  
Qixin Chen ◽  
Jesse Slone ◽  
Li Yang ◽  
Xiaoting Lou ◽  
...  
Keyword(s):  
Oxidative Phosphorylation ◽  
Optic Atrophy ◽  
Respiratory Function ◽  
Clinical Symptoms ◽  
Mitochondrial Dynamics ◽  
Cerebellar Atrophy ◽  
Mitochondrial Diseases ◽  
Living Cells ◽  
Mitochondrial Morphology ◽  
Mitochondrial Oxidative Phosphorylation

AbstractSLC25A46 mutations have been found to lead to mitochondrial hyper-fusion and reduced mitochondrial respiratory function, which results in optic atrophy, cerebellar atrophy, and other clinical symptoms of mitochondrial disease. However, it is generally believed that mitochondrial fusion is attributable to increased mitochondrial oxidative phosphorylation (OXPHOS), which is inconsistent with the decreased OXPHOS of highly-fused mitochondria observed in previous studies. In this paper, we have used the live-cell nanoscope to observe and quantify the structure of mitochondrial cristae, and the behavior of mitochondria and lysosomes in patient-derived SLC25A46 mutant fibroblasts. The results show that the cristae have been markedly damaged in the mutant fibroblasts, but there is no corresponding increase in mitophagy. This study suggests that severely damaged mitochondrial cristae might be the predominant cause of reduced OXPHOS in SLC25A46 mutant fibroblasts. This study demonstrates the utility of nanoscope-based imaging for realizing the sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells, which may be particularly valuable for the quick evaluation of pathogenesis of mitochondrial morphological abnormalities.

scholarly journals Quantitative proteomics revealed C6orf203/MTRES1 as a factor preventing stress-induced transcription deficiency in human mitochondria

2019 ◽  
Vol 47 (14) ◽  
pp. 7502-7517 ◽  
Author(s):  
Anna V Kotrys ◽  
Dominik Cysewski ◽  
Sylwia D Czarnomska ◽  
Zbigniew Pietras ◽  
Lukasz S Borowski ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rna Binding ◽  
Mitochondrial Gene ◽  
Binding Activity ◽  
Stress Conditions ◽  
Mitochondrial Rna ◽  
Mitochondrial Gene Expression ◽  
Compensatory Mechanisms ◽  
Temporary Reduction ◽  
Mitochondrial Transcription

AbstractMaintenance of mitochondrial gene expression is crucial for cellular homeostasis. Stress conditions may lead to a temporary reduction of mitochondrial genome copy number, raising the risk of insufficient expression of mitochondrial encoded genes. Little is known how compensatory mechanisms operate to maintain proper mitochondrial transcripts levels upon disturbed transcription and which proteins are involved in them. Here we performed a quantitative proteomic screen to search for proteins that sustain expression of mtDNA under stress conditions. Analysis of stress-induced changes of the human mitochondrial proteome led to the identification of several proteins with poorly defined functions among which we focused on C6orf203, which we named MTRES1 (Mitochondrial Transcription Rescue Factor 1). We found that the level of MTRES1 is elevated in cells under stress and we show that this upregulation of MTRES1 prevents mitochondrial transcript loss under perturbed mitochondrial gene expression. This protective effect depends on the RNA binding activity of MTRES1. Functional analysis revealed that MTRES1 associates with mitochondrial RNA polymerase POLRMT and acts by increasing mitochondrial transcription, without changing the stability of mitochondrial RNAs. We propose that MTRES1 is an example of a protein that protects the cell from mitochondrial RNA loss during stress.

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