scholarly journals MRM2 and MRM3 are involved in biogenesis of the large subunit of the mitochondrial ribosome

2014 ◽  
Vol 25 (17) ◽  
pp. 2542-2555 ◽  
Author(s):  
Joanna Rorbach ◽  
Pierre Boesch ◽  
Payam A. Gammage ◽  
Thomas J. J. Nicholls ◽  
Sarah F. Pearce ◽  
...  
Keyword(s):  
16S Rrna ◽  
Rna Processing ◽  
Large Subunit ◽  
Peptidyl Transferase ◽  
Mitochondrial Translation ◽  
Peptidyl Transferase Center ◽  
Mitochondrial Ribosome ◽  
Translation Apparatus ◽  
Rrna Maturation ◽  
And Function

Defects of the translation apparatus in human mitochondria are known to cause disease, yet details of how protein synthesis is regulated in this organelle remain to be unveiled. Ribosome production in all organisms studied thus far entails a complex, multistep pathway involving a number of auxiliary factors. This includes several RNA processing and modification steps required for correct rRNA maturation. Little is known about the maturation of human mitochondrial 16S rRNA and its role in biogenesis of the mitoribosome. Here we investigate two methyltransferases, MRM2 (also known as RRMJ2, encoded by FTSJ2) and MRM3 (also known as RMTL1, encoded by RNMTL1), that are responsible for modification of nucleotides of the 16S rRNA A-loop, an essential component of the peptidyl transferase center. Our studies show that inactivation of MRM2 or MRM3 in human cells by RNA interference results in respiratory incompetence as a consequence of diminished mitochondrial translation. Ineffective translation in MRM2- and MRM3-depleted cells results from aberrant assembly of the large subunit of the mitochondrial ribosome (mt-LSU). Our findings show that MRM2 and MRM3 are human mitochondrial methyltransferases involved in the modification of 16S rRNA and are important factors for the biogenesis and function of the large subunit of the mitochondrial ribosome.

scholarly journals Proteomic profiling of the mitochondrial ribosome identifies Atp25 as a composite mitochondrial precursor protein

2016 ◽  
Vol 27 (20) ◽  
pp. 3031-3039 ◽  
Author(s):  
Michael W. Woellhaf ◽  
Frederik Sommer ◽  
Michael Schroda ◽  
Johannes M. Herrmann
Keyword(s):  
Precursor Protein ◽  
Ribosomal Biogenesis ◽  
Proteomic Profiling ◽  
Mitochondrial Translation ◽  
Bacterial Ribosome ◽  
Mitochondrial Ribosome ◽  
Translation Apparatus ◽  
The Matrix ◽  
Processing Peptidase ◽  
And Function

Whereas the structure and function of cytosolic ribosomes are well characterized, we only have a limited understanding of the mitochondrial translation apparatus. Using SILAC-based proteomic profiling, we identified 13 proteins that cofractionated with the mitochondrial ribosome, most of which play a role in translation or ribosomal biogenesis. One of these proteins is a homologue of the bacterial ribosome-silencing factor (Rsf). This protein is generated from the composite precursor protein Atp25 upon internal cleavage by the matrix processing peptidase MPP, and in this respect, it differs from all other characterized mitochondrial proteins of baker’s yeast. We observed that cytosolic expression of Rsf, but not of noncleaved Atp25 protein, is toxic. Our results suggest that eukaryotic cells face the challenge of avoiding negative interference from the biogenesis of their two distinct translation machineries.

scholarly journals Visualizing formation of the active site in the mitochondrial ribosome

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Viswanathan Chandrasekaran ◽  
Nirupa Desai ◽  
Nicholas O Burton ◽  
Hanting Yang ◽  
Jon Price ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
Large Subunit ◽  
Mitochondrial Protein ◽  
Mitochondrial Protein Synthesis ◽  
Peptidyl Transferase ◽  
Mitochondrial Stress ◽  
Peptidyl Transferase Center ◽  
Cryo Electron Microscopy ◽  
Mitochondrial Ribosome ◽  
Specific Factors

Ribosome assembly is an essential and conserved process that is regulated at each step by specific factors. Using cryo-electron microscopy (cryo-EM), we visualize the formation of the conserved peptidyl transferase center (PTC) of the human mitochondrial ribosome. The conserved GTPase GTPBP7 regulates the correct folding of 16S ribosomal RNA (rRNA) helices and ensures 2ʹ-O-methylation of the PTC base U3039. GTPBP7 binds the RNA methyltransferase NSUN4 and MTERF4, which sequester H68-71 of the 16S rRNA and allow biogenesis factors to access the maturing PTC. Mutations that disrupt binding of their Caenorhabditis elegans orthologs to the large subunit potently activate mitochondrial stress and cause viability, development, and sterility defects. Next-generation RNA sequencing reveals widespread gene expression changes in these mutant animals that are indicative of mitochondrial stress response activation. We also answer the long-standing question of why NSUN4, but not its enzymatic activity, is indispensable for mitochondrial protein synthesis.

scholarly journals Stepwise maturation of the peptidyl transferase region of human mitoribosomes

2021 ◽  
Author(s):  
Tea Lenarcic ◽  
Mateusz Jaskolowski ◽  
Marc Leibundgut ◽  
Alain Scaiola ◽  
Tanja Schoenhut ◽  
...  
Keyword(s):  
Quality Control ◽  
16S Rrna ◽  
Active Site ◽  
Critical Role ◽  
Ribosomal Subunit ◽  
Structural Basis ◽  
Ribosome Assembly ◽  
Peptidyl Transferase ◽  
Mitochondrial Ribosomes ◽  
Mitochondrial Ribosome

Mitochondrial ribosomes are specialized for the synthesis of membrane proteins responsible for oxidative phosphorylation. Mammalian mitoribosomes diverged considerably from the ancestral bacterial ribosomes and feature dramatically reduced ribosomal RNAs. Structural basis of the mammalian mitochondrial ribosome assembly is currently not understood. Here we present eight distinct assembly intermediates of the human large mitoribosomal subunit involving 7 assembly factors. We discover that NSUN4-MTERF4 dimer plays a critical role in the process by stabilizing the 16S rRNA in a conformation that exposes the functionally important regions of rRNA for modification by MRM2 methyltransferase and quality control interactions with a conserved mitochondrial GTPase MTG2 that contacts the sarcin ricin loop and the immature active site. The successive action of these factors leads to the formation of the peptidyl transferase active site of the mitoribosome and the folding of the surrounding rRNA regions responsible for interactions with tRNAs and the small ribosomal subunit.

scholarly journals Mrpl36 Is Important for Generation of Assembly Competent Proteins during Mitochondrial Translation

2009 ◽  
Vol 20 (10) ◽  
pp. 2615-2625 ◽  
Author(s):  
Martin Prestele ◽  
Frank Vogel ◽  
Andreas S. Reichert ◽  
Johannes M. Herrmann ◽  
Martin Ott
Keyword(s):  
Protein Synthesis ◽  
Respiratory Chain ◽  
Large Subunit ◽  
Critical Role ◽  
Mitochondrial Translation ◽  
Respiratory Chain Complexes ◽  
Ribosomal Subunits ◽  
Terminal Domain ◽  
Chain Complexes ◽  
Mitochondrial Ribosome

The complexes of the respiratory chain represent mosaics of nuclear and mitochondrially encoded components. The processes by which synthesis and assembly of the various subunits are coordinated remain largely elusive. During evolution, many proteins of the mitochondrial ribosome acquired additional domains pointing at specific properties or functions of the translation machinery in mitochondria. Here, we analyzed the function of Mrpl36, a protein associated with the large subunit of the mitochondrial ribosome. This protein, homologous to the ribosomal protein L31 from bacteria, contains a mitochondria-specific C-terminal domain that is not required for protein synthesis per se; however, its absence decreases stability of Mrpl36. Cells lacking this C-terminal domain can still synthesize proteins, but these translation products fail to be properly assembled into respiratory chain complexes and are rapidly degraded. Surprisingly, overexpression of Mrpl36 seems to even increase the efficiency of mitochondrial translation. Our data suggest that Mrpl36 plays a critical role during translation that determines the rate of respiratory chain assembly. This important function seems to be carried out by a stabilizing activity of Mrpl36 on the interaction between large and small ribosomal subunits, which could influence accuracy of protein synthesis.

scholarly journals YbeY is required for ribosome small subunit assembly and tRNA processing in human mitochondria

2019 ◽  
Author(s):  
Aaron R. D’Souza ◽  
Lindsey Van Haute ◽  
Christopher A. Powell ◽  
Pedro Rebelo-Guiomar ◽  
Joanna Rorbach ◽  
...  
Keyword(s):  
Small Subunit ◽  
Dual Function ◽  
Mitochondrial Translation ◽  
Trna Processing ◽  
Mitochondrial Ribosome ◽  
Severe Reduction ◽  
Translation Apparatus ◽  
Additional Protein ◽  
Processing Steps ◽  
Issue Section

AbstractMitochondria contain their own translation apparatus which enables them to produce the polypeptides encoded in their genome. The mitochondrially-encoded RNA components of the mitochondrial ribosome require various post-transcriptional processing steps. Additional protein factors are required to facilitate the biogenesis of the functional mitoribosome. We have characterised a mitochondrially-localized protein, YbeY, which interacts with the assembling mitoribosome through the small subunit. Loss of YbeY leads to a severe reduction in mitochondrial translation and a loss of cell viability, caused by less accurate mitochondrial mt-tRNASer(AGY) processing from the primary transcript and an accumulation of immature mitochondrial small subunit. Our results suggest that YbeY performs a dual function in mitochondria coupling tRNA processing to mitoribosome biogenesis.Issue SectionNucleic Acid EnzymesAbstract Figure

scholarly journals Stepwise maturation of the peptidyl transferase region of human mitoribosomes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tea Lenarčič ◽  
Mateusz Jaskolowski ◽  
Marc Leibundgut ◽  
Alain Scaiola ◽  
Tanja Schönhut ◽  
...  
Keyword(s):  
Quality Control ◽  
16S Rrna ◽  
Active Site ◽  
Critical Role ◽  
Ribosomal Subunit ◽  
Structural Basis ◽  
Ribosome Assembly ◽  
Peptidyl Transferase ◽  
Mitochondrial Ribosomes ◽  
Mitochondrial Ribosome

AbstractMitochondrial ribosomes are specialized for the synthesis of membrane proteins responsible for oxidative phosphorylation. Mammalian mitoribosomes have diverged considerably from the ancestral bacterial ribosomes and feature dramatically reduced ribosomal RNAs. The structural basis of the mammalian mitochondrial ribosome assembly is currently not well understood. Here we present eight distinct assembly intermediates of the human large mitoribosomal subunit involving seven assembly factors. We discover that the NSUN4-MTERF4 dimer plays a critical role in the process by stabilizing the 16S rRNA in a conformation that exposes the functionally important regions of rRNA for modification by the MRM2 methyltransferase and quality control interactions with the conserved mitochondrial GTPase MTG2 that contacts the sarcin-ricin loop and the immature active site. The successive action of these factors leads to the formation of the peptidyl transferase active site of the mitoribosome and the folding of the surrounding rRNA regions responsible for interactions with tRNAs and the small ribosomal subunit.

scholarly journals PTCD1 Is Required for 16S rRNA Maturation Complex Stability and Mitochondrial Ribosome Assembly

Cell Reports ◽  
2018 ◽  
Vol 23 (1) ◽  
pp. 127-142 ◽  
Author(s):  
Kara L. Perks ◽  
Giulia Rossetti ◽  
Irina Kuznetsova ◽  
Laetitia A. Hughes ◽  
Judith A. Ermer ◽  
...  
Keyword(s):  
16S Rrna ◽  
Ribosome Assembly ◽  
Complex Stability ◽  
Mitochondrial Ribosome ◽  
Rrna Maturation

scholarly journals A late-stage assembly checkpoint of the human mitochondrial ribosome large subunit

2021 ◽  
Author(s):  
Pedro Rebelo-Guiomar ◽  
Simone Pellegrino ◽  
Kyle Dent ◽  
Aldema Sas- Chen ◽  
Leonor Miller-Fleming ◽  
...  
Keyword(s):  
Late Stage ◽  
Ribosome Biogenesis ◽  
Essential Gene ◽  
Large Subunit ◽  
Mitochondrial Translation ◽  
Cellular Processes ◽  
Mitochondrial Ribosome ◽  
Severe Impairment ◽  
Control Step ◽  
Rna Domains

The epitranscriptome plays a key regulatory role in cellular processes in health and disease, including ribosome biogenesis. Here, analysis of the human mitochondrial transcriptome shows that 2'-O-methylation is limited to residues of the mitoribosomal large subunit (mtLSU) 16S mt-rRNA, modified by MRM1, MRM2, and MRM3. Ablation of MRM2 leads to a severe impairment of the oxidative phosphorylation system, caused by defective mitochondrial translation and accumulation of mtLSU assembly intermediates. Structures of these particles (2.58 Å) present disordered RNA domains, partial occupancy of bL36m and bound MALSU1:L0R8F8:mtACP anti-association module. Additionally, we present five mtLSU assembly states with different intersubunit interface configurations. Complementation studies demonstrate that the methyltransferase activity of MRM2 is dispensable for mitoribosome biogenesis. The Drosophila melanogaster orthologue, DmMRM2, is an essential gene, with its knock- down leading to developmental arrest. This work identifies a key late-stage quality control step during mtLSU assembly, ultimately contributing to the maintenance of mitochondrial homeostasis.

scholarly journals Mitochondrial Proteostasis Requires Genes Encoded in a Neurodevelopmental Syndrome Locus that are Necessary for Synapse Function

2020 ◽  
Author(s):  
Avanti Gokhale ◽  
Chelsea E. Lee ◽  
Stephanie A. Zlatic ◽  
Amanda A. H. Freeman ◽  
Nicole Shearing ◽  
...  
Keyword(s):  
Neurodevelopmental Disorders ◽  
Fragile X ◽  
Mitochondrial Protein ◽  
Protein Translation ◽  
Synapse Development ◽  
Mitochondrial Translation ◽  
Mitochondrial Ribosome ◽  
Number Variation ◽  
And Function ◽  
And Behavior

AbstractEukaryotic cells maintain proteostasis through mechanisms that require cytoplasmic and mitochondrial translation. Genetic defects affecting cytoplasmic translation perturb synapse development, neurotransmission, and are causative of neurodevelopmental disorders such as Fragile X syndrome. In contrast, there is little indication that mitochondrial proteostasis, either in the form of mitochondrial protein translation and/or degradation, is required for synapse development and function. Here we focus on two genes deleted in a recurrent copy number variation causing neurodevelopmental disorders, the 22q11.2 microdeletion syndrome. We demonstrate that SLC25A1 and MRPL40, two genes present in this microdeleted segment and whose products localize to mitochondria, interact and are necessary for mitochondrial protein translation and proteostasis. Our Drosophila studies show that mitochondrial ribosome function is necessary for synapse neurodevelopment, function, and behavior. We propose that mitochondrial proteostasis perturbations, either by genetic or environmental factors, are a novel pathogenic mechanism for neurodevelopmental disorders.

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