Functional Diversity of Mitochondrial Peptidyl-tRNA Hydrolase ICT1 in Human Cells

Mitochondria are energy producing organelles of the eukaryotic cell, involved in the synthesis of key metabolites, calcium homeostasis and apoptosis. Protein biosynthesis in these organelles is a relic of its endosymbiotic origin. While mitochondrial translational factors have homologues among prokaryotes, they possess a number of unique traits. Remarkably as many as four mammalian mitochondrial proteins possess a clear similarity with translation termination factors. The review focuses on the ICT1, which combines several functions. It is a non-canonical termination factor for protein biosynthesis, a rescue factor for stalled mitochondrial ribosomes, a structural protein and a regulator of proliferation, cell cycle, and apoptosis. Such a diversity of roles demonstrates the high functionality of mitochondrial translation associated proteins and their relationship with numerous processes occurring in a living cell.

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Iron in Translation: From the Beginning to the End

Microorganisms ◽

10.3390/microorganisms9051058 ◽

2021 ◽

Vol 9 (5) ◽

pp. 1058

Author(s):

Antonia María Romero ◽

María Teresa Martínez-Pastor ◽

Sergi Puig

Keyword(s):

Translational Regulation ◽

Translation Termination ◽

Protein Biosynthesis ◽

Regulatory Protein ◽

Dynamic Control ◽

Essential Element ◽

Cellular Functions ◽

Yeast Saccharomyces Cerevisiae ◽

Eukaryotic Translation ◽

Responsive Element

Iron is an essential element for all eukaryotes, since it acts as a cofactor for many enzymes involved in basic cellular functions, including translation. While the mammalian iron-regulatory protein/iron-responsive element (IRP/IRE) system arose as one of the first examples of translational regulation in higher eukaryotes, little is known about the contribution of iron itself to the different stages of eukaryotic translation. In the yeast Saccharomyces cerevisiae, iron deficiency provokes a global impairment of translation at the initiation step, which is mediated by the Gcn2-eIF2α pathway, while the post-transcriptional regulator Cth2 specifically represses the translation of a subgroup of iron-related transcripts. In addition, several steps of the translation process depend on iron-containing enzymes, including particular modifications of translation elongation factors and transfer RNAs (tRNAs), and translation termination by the ATP-binding cassette family member Rli1 (ABCE1 in humans) and the prolyl hydroxylase Tpa1. The influence of these modifications and their correlation with codon bias in the dynamic control of protein biosynthesis, mainly in response to stress, is emerging as an interesting focus of research. Taking S. cerevisiae as a model, we hereby discuss the relevance of iron in the control of global and specific translation steps.

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Coupling of mitochondrial translation with the formation of respiratory complexes in yeast mitochondria.

Acta Biochimica Polonica ◽

10.18388/abp.2000_3952 ◽

2000 ◽

Vol 47 (4) ◽

pp. 973-991 ◽

Cited By ~ 6

Author(s):

A Chacińska ◽

M Boguta

Keyword(s):

Mitochondrial Dna ◽

Genomic Sequence ◽

Mitochondrial Translation ◽

Translation Process ◽

Cellular Compartment ◽

Respiratory Complexes ◽

Mitochondrial Ribosomes ◽

Eukaryotic Organisms ◽

Export System

In contrast to most other eukaryotic organisms, yeast can survive without respiration. This ability has been exploited to investigate nuclear genes required for expression of mitochondrial DNA. Availability of complete Saccharomyces cerevisiae genomic sequence has provided additional help in detailed molecular analysis. Seven of the eight major products encoded by mitochondrial DNA are hydrophobic subunits of respiratory complexes in the inner membrane. Localization of the translation process in the same cellular compartment ensures synthesis of mitochondrially encoded proteins near sites of their assembly into multimeric respiratory complexes. Association of mitochondrial ribosomes with the membrane is mediated by mRNA-specific translational activators, that are involved in the recognition of initiation codon. The newly synthesized mitochondrial proteins are transferred to membrane by a specific export system. This review discusses the role of membrane-localized factors responsible for quality control and turnover of mitochondrially synthesized subunits as well as for assembly of respiratory complexes.

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Monitoring mitochondrial translation by pulse SILAC

10.1101/2021.01.31.428997 ◽

2021 ◽

Author(s):

Koshi Imami ◽

Matthias Selbach ◽

Yasushi Ishihama

Keyword(s):

Oxidative Stress ◽

Amino Acids ◽

Membrane Proteins ◽

Translational Regulation ◽

Isotope Labeling ◽

Protein Complexes ◽

Complex Iii ◽

Mitochondrial Translation ◽

Mitochondrial Ribosomes ◽

Hydrophobic Nature

SummaryMitochondrial ribosomes are specialized to translate the 13 membrane proteins encoded in the mitochondrial genome, but it is challenging to quantify mitochondrial translation products due to their hydrophobic nature. Here, we introduce a proteomic method that combines biochemical isolation of mitochondria with pulse stable isotope labeling by amino acids in cell culture (pSILAC). Our method provides the highest protein coverage (quantifying 12 out of the 13 inner-membrane proteins; average 2-fold improvement over previous studies) with the shortest measurement time. We applied this method to uncover the global picture of (post)translational regulation of both mitochondrial- and nuclear-encoded proteins involved in the assembly of protein complexes that mediate oxidative phosphorylation (OXPHOS). The results allow us to infer the assembly order of complex components and/or partners, as exemplified by complex III. This method should be applicable to study mitochondrial translation programs in many contexts, including oxidative stress and mitochondrial disease.

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Dysregulated pathways for off-pump coronary artery bypass grafting

Open Life Sciences ◽

10.1515/biol-2017-0047 ◽

2017 ◽

Vol 12 (1) ◽

pp. 399-405

Author(s):

Xu Li ◽

Dao-Kang Xiang ◽

Yi-Zhu Shu ◽

Cheng-Hui Feng

Keyword(s):

Coronary Artery ◽

Coronary Artery Bypass Grafting ◽

Coronary Artery Bypass ◽

Translation Termination ◽

Artery Bypass ◽

Bypass Grafting ◽

Mitochondrial Translation ◽

Artery Bypass Grafting ◽

Off Pump ◽

Pump Coronary Artery Bypass

AbstractBackgroundThe objective of this paper was to identify dysregulated myocardial pathways with off-pump coronary artery bypass grafting (OPCABG) based on pathway interaction network (PIN).MethodologyTo achieve this goal, firstly, gene expression profiles, protein-protein interactions (PPIs) and pathway data were collected. Secondly, we constructed a PIN by integrating these data and Pearson correlation coefficient (PCC) algorithm. Next, for every pathway in the PIN, its activity was counted dependent on the principal component analysis (PCA) method to select the seed pathway. Ultimately, a minimum pathway set (MPS) was extracted from the PIN on the basis of the seed pathway and the area under the receiver operating characteristics curve (AUROC) index, and pathways in the MPS were denoted as dysregulated pathways.ResultsThe PIN had 1,189 nodes and 22,756 interactions, of which mitochondrial translation termination was the seed pathway. Starting with mitochondrial translation termination, a MPS (AUROC = 0.983) with 7 nodes and 26 edges was obtained. The 7 pathways were regarded as dysregulated myocardial pathways with OPCABG.ConclusionThe findings might provide potential biomarkers to diagnose early, serve as the evidence to perform the OPCABG and predict inflammatory response and myocardial reperfusion injury after OPCABG in the future.

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The ribosome receptors Mrx15 and Mba1 jointly organize cotranslational insertion and protein biogenesis in mitochondria

Molecular Biology of the Cell ◽

10.1091/mbc.e18-04-0227 ◽

2018 ◽

Vol 29 (20) ◽

pp. 2386-2396 ◽

Cited By ~ 14

Author(s):

Braulio Vargas Möller-Hergt ◽

Andreas Carlström ◽

Katharina Stephan ◽

Axel Imhof ◽

Martin Ott

Keyword(s):

Membrane Protein ◽

Mitochondrial Gene ◽

Ribosomal Subunit ◽

Mitochondrial Translation ◽

Protein Insertion ◽

Mitochondrial Ribosomes ◽

Protein Biogenesis ◽

Membrane Bound ◽

Highly Hydrophobic ◽

Soluble C

Mitochondrial gene expression in Saccharomyces cerevisiae is responsible for the production of highly hydrophobic subunits of the oxidative phosphorylation system. Membrane insertion occurs cotranslationally on membrane-bound mitochondrial ribosomes. Here, by employing a systematic mass spectrometry–based approach, we discovered the previously uncharacterized membrane protein Mrx15 that interacts via a soluble C-terminal domain with the large ribosomal subunit. Mrx15 contacts mitochondrial translation products during their synthesis and plays, together with the ribosome receptor Mba1, an overlapping role in cotranslational protein insertion. Taken together, our data reveal how these ribosome receptors organize membrane protein biogenesis in mitochondria.

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Mitochondrial translation, dynamics, and lysosomes combine to extend lifespan

The Journal of Cell Biology ◽

10.1083/jcb.202005084 ◽

2020 ◽

Vol 219 (6) ◽

Author(s):

Levi Ali ◽

Cole M. Haynes

Keyword(s):

Transcription Factor ◽

Mitochondrial Fission ◽

Mitochondrial Translation ◽

C Elegans ◽

Mitochondrial Ribosomes

In this issue, Liu et al. (2019. J. Cell. Biol.https://doi.org/10.1083/jcb.201907067) find that the inhibition of mitochondrial ribosomes in combination with impaired mitochondrial fission or fusion increases C. elegans lifespan by activating the transcription factor HLH-30, which promotes lysosomal biogenesis.

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CTELS: A Cell-Free System for the Analysis of Translation Termination Rate

Biomolecules ◽

10.3390/biom10060911 ◽

2020 ◽

Vol 10 (6) ◽

pp. 911 ◽

Cited By ~ 3

Author(s):

Kseniya A. Lashkevich ◽

Valeriya I. Shlyk ◽

Artem S. Kushchenko ◽

Vadim N. Gladyshev ◽

Elena Z. Alkalaeva ◽

...

Keyword(s):

Stop Codon ◽

Translation Termination ◽

Protein Biosynthesis ◽

Inhibitory Effect ◽

In Vitro Translation ◽

Nonsense Suppression ◽

Translation System ◽

Free System ◽

Termination Rate

Translation termination is the final step in protein biosynthesis when the synthesized polypeptide is released from the ribosome. Understanding this complex process is important for treatment of many human disorders caused by nonsense mutations in important genes. Here, we present a new method for the analysis of translation termination rate in cell-free systems, CTELS (for C-terminally extended luciferase-based system). This approach was based on a continuously measured luciferase activity during in vitro translation reaction of two reporter mRNA, one of which encodes a C-terminally extended luciferase. This extension occupies a ribosomal polypeptide tunnel and lets the completely synthesized enzyme be active before translation termination occurs, i.e., when it is still on the ribosome. In contrast, luciferase molecule without the extension emits light only after its release. Comparing the translation dynamics of these two reporters allows visualization of a delay corresponding to the translation termination event. We demonstrated applicability of this approach for investigating the effects of cis- and trans-acting components, including small molecule inhibitors and read-through inducing sequences, on the translation termination rate. With CTELS, we systematically assessed negative effects of decreased 3′ UTR length, specifically on termination. We also showed that blasticidin S implements its inhibitory effect on eukaryotic translation system, mostly by affecting elongation, and that an excess of eRF1 termination factor (both the wild-type and a non-catalytic AGQ mutant) can interfere with elongation. Analysis of read-through mechanics with CTELS revealed a transient stalling event at a “leaky” stop codon context, which likely defines the basis of nonsense suppression.

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Microtubule Retrograde Motors and Their Role in Retroviral Transport

Viruses ◽

10.3390/v12040483 ◽

2020 ◽

Vol 12 (4) ◽

pp. 483

Author(s):

Gianfranco Pietrantoni ◽

Rodrigo Ibarra-Karmy ◽

Gloria Arriagada

Keyword(s):

Host Cell ◽

Reverse Transcription ◽

Eukaryotic Cell ◽

Chromosomal Dna ◽

Viral Dna ◽

Preintegration Complex ◽

Retrograde Trafficking ◽

Microtubule Associated Proteins ◽

Associated Proteins ◽

Crowded Environment

Following entry into the host cell, retroviruses generate a dsDNA copy of their genomes via reverse transcription, and this viral DNA is subsequently integrated into the chromosomal DNA of the host cell. Before integration can occur, however, retroviral DNA must be transported to the nucleus as part of a ‘preintegration complex’ (PIC). Transporting the PIC through the crowded environment of the cytoplasm is challenging, and retroviruses have evolved different mechanisms to accomplish this feat. Within a eukaryotic cell, microtubules act as the roads, while the microtubule-associated proteins dynein and kinesin are the vehicles that viruses exploit to achieve retrograde and anterograde trafficking. This review will examine the various mechanisms retroviruses have evolved in order to achieve retrograde trafficking, confirming that each retrovirus has its own strategy to functionally subvert microtubule associated proteins.

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Detecting Protein-Protein Interactions in the Intact Cell of Bacillus subtilis (ATCC 6633)

Journal of Bacteriology ◽

10.1128/jb.185.14.4268-4275.2003 ◽

2003 ◽

Vol 185 (14) ◽

pp. 4268-4275 ◽

Cited By ~ 8

Author(s):

Michael S. Winters ◽

R. A. Day

Keyword(s):

Bacillus Subtilis ◽

Protein Interactions ◽

Ribosomal Proteins ◽

Intact Cell ◽

Protein Biosynthesis ◽

Polyacrylamide Gel Electrophoresis ◽

Protein Database ◽

Haloarcula Marismortui ◽

Associated Proteins ◽

Covalently Linked

ABSTRACT The salt bridge, paired group-specific reagent cyanogen (ethanedinitrile; C2N2) converts naturally occurring pairs of functional groups into covalently linked products. Cyanogen readily permeates cell walls and membranes. When the paired groups are shared between associated proteins, isolation of the covalently linked proteins allows their identity to be assigned. Examination of organisms of known genome sequence permits identification of the linked proteins by mass spectrometric techniques applied to peptides derived from them. The cyanogen-linked proteins were isolated by polyacrylamide gel electrophoresis. Digestion of the isolated proteins with proteases of known specificity afforded sets of peptides that could be analyzed by mass spectrometry. These data were compared with those derived theoretically from the Swiss Protein Database by computer-based comparisons (Protein Prospector; http://prospector.ucsf.edu ). Identification of associated proteins in the ribosome of Bacillus subtilis strain ATCC 6633 showed that there is an association homology with the association patterns of the ribosomal proteins of Haloarcula marismortui and Thermus thermophilus. In addition, other proteins involved in protein biosynthesis were shown to be associated with ribosomal proteins.

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Insulin stimulates mitochondrial protein synthesis and respiration in isolated perfused rat heart.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.259.3.e413 ◽

1990 ◽

Vol 259 (3) ◽

pp. E413

Author(s):

E E McKee ◽

B L Grier

Keyword(s):

Protein Synthesis ◽

Mitochondrial Protein ◽

Control Level ◽

Respiratory Control ◽

Mitochondrial Proteins ◽

Mitochondrial Protein Synthesis ◽

Mitochondrial Translation ◽

Rat Hearts ◽

Perfused Rat Hearts ◽

Perfused Hearts

The rates of synthesis of mitochondrial proteins by both the cytoplasmic and mitochondrial protein synthetic systems, as well as parameters of respiration, were measured and compared in mitochondria isolated from fresh, control perfused, and insulin-perfused rat hearts. The respiratory control ratio (RCR) in mitochondria from fresh hearts was 8.1 +/- 0.4 and decreased to 6.0 +/- 0.2 (P less than 0.001 vs. fresh) in mitochondria from control perfused hearts and to 6.7 +/- 0.2 (P less than 0.005 vs. fresh and P less than 0.02 vs. control perfused) for mitochondria from hearts perfused in the presence of insulin. A positive correlation between the RCR and the rate of mitochondrial translation was demonstrated in mitochondria from fresh hearts. In mitochondria isolated from control perfused hearts, the rate of protein synthesis decreased to 84 +/- 3% of the fresh rate after 30 min of perfusion and fell further to 64 +/- 3% after 3 h of perfusion. The inclusion of insulin in the perfusion buffer stimulated mitochondrial protein synthesis 1.2-fold by 1 h (P less than 0.005) and 1.34-fold by 3 h of perfusion (P less than 0.001). The addition of insulin to 1-h control perfused hearts shifted the rate of mitochondrial protein synthesis from the control level to the insulin-perfused level within 30 min of additional perfusion, whereas 1 h was required to shift the RCR values of these mitochondria from control levels to insulin-perfused levels. Thus, whereas RCR was a useful predictor of mitochondrial translation rates, it did not account for the effects of insulin on mitochondrial translation.(ABSTRACT TRUNCATED AT 250 WORDS)

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