MtRF1 recognises non-canonical stop codons in human mitochondria
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ABSTRACT:
PROVIDER: PRJNA896508 | ENA |
REPOSITORIES: ENA
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Project description:The genetic code that specifies the identity of amino acids incorporated into proteins during protein synthesis is almost universally conserved. Mitochondrial translation deviates from the standard genetic code which includes the reassignment of two arginine codons into stop codons {Jukes, 1993 #438}. Translation termination at these non-canonical stop codons requires a protein factor to release the newly synthesized polypeptide chain, however, the identity of this factor is not known currently{Nadler, 2021 #406}. Here, we used gene editing and ribo-profiling in combination with cryo-electron microscopy to establish that the unusual mitochondrial release factor 1 (mtRF1) detects the non-canonical stop codons. We show that loss of mtRF1 leads to stalling of mitochondrial ribosomes on non-canonical stop codons and consequent reduced translation of cytochrome C oxidase subunit 1 that results in decreased mitochondrial respiration. We show that binding of mtRF1 to the decoding center of the ribosome stabilizes a highly unusual distortion in the mRNA conformation and that the ribosomal RNA importantly participates in the specific recognition of the non-canonical stop codons.
2023-03-21 | GSE216979 | GEO
Project description:The genetic code that specifies the identity of amino acids incorporated into proteins during protein synthesis is almost universally conserved. Mitochondrial translation, however, exhibits deviations from the standard genetic code including reassigning of two arginine codons to stop codons. Translation termination at these non-canonical stop codons requires a protein factor to release the newly synthesized polypeptide chain. Currently it is not known how, and by which release factor, these stop codons are recognized. Here, we used biochemical experiments on knockout mutants in human cells in combination with cryo-electron microscopy to establish that the unusual mitochondrial release factor 1 (mtRF1) detects the non-canonical stop codons. We show that loss of this factor leads to stalling of mitochondrial ribosomes on non-canonical stop codons. As a result, reduced levels of cytochrome C oxidase subunit 1 of the oxidative phosphorylation complex IV are synthesized leading to a defect in mitochondrial respiration. We further show that binding of mtRF1 to the decoding center of the ribosome stabilizes a highly unusual distortion in the mRNA conformation and that the ribosomal RNA importantly participates in the specific recognition of the non-canonical stop codons.
2023-05-09 | GSE216779 | GEO
Project description:Mitochondrial translation system highly diverged from its bacterial counterpart. This includes deviation from the universal genetic code, with AGA and AGG having no cognate tRNAs in human mitochondria. Their locations at the end of COX1 and ND6 open reading frames, respectively, suggests they function as stop codons. However, while canonical stop codons, UAA and UAG, are recognized by mtRF1a in mitochondria, the release mechanism at AGA and AGG remains a debated issue. Here, we show that upon the loss of another member of the mitochondrial release factor family, mtRF1, mitoribosomes accumulate specifically at AGA and AGG codons. Stalling of mitoribosomes alters COX1 transcript and protein levels, but not ND6 production. Finally, we set up an in vitro reconstituted mitochondrial translation system, which confirms the specific release activity of mtRF1 on AGA and AGG codons. Together, our study uncovers the mechanism of translation termination in mitochondria and provides first insights into the consequences of its failure.
2022-11-16 | PXD034342 | Pride
Project description:Molecular basis of non-canonical stop codon recognition by mtRF1 in human mitochondria
| PRJNA895374 | ENA
Project description:Stop codon readthrough (SCR) has important biological implications but remains largely uncharacterized. Here, we identify 1,009 SCR events in plants using a proteogenomic strategy. Plant SCR candidates tend to have shorter transcript lengths and fewer exons and splice variants than non-SCR transcripts. Mass spectrometry evidence shows that stop codons involved in SCR events can be recoded as 20 standard amino acids, some of which are also supported by suppressor transfer RNA analysis. We also observe multiple functional signals in 34 maize extended proteins and characterize the structural and subcellular localization changes in the extended protein of BASIC TRANSCRIPTION FACTOR 3. Furthermore, the SCR events exhibit non-conserved signature and the extensions likely undergo protein-coding selection. Overall, our study not only characterizes that SCR events are commonly present in plants but also identifies the unprecedented recoding plasticity of stop codons, which provides important insights into the flexibility of genetic decoding.
2024-02-02 | PXD038762 | Pride
Project description:Stop codon readthrough (SCR) has important biological implications but remains largely uncharacterized. Here, we identify 1,009 SCR events in plants using a proteogenomic strategy. Plant SCR candidates tend to have shorter transcript lengths and fewer exons and splice variants than non-SCR transcripts. Mass spectrometry evidence shows that stop codons involved in SCR events can be recoded as 20 standard amino acids, some of which are also supported by suppressor transfer RNA analysis. We also observe multiple functional signals in 34 maize extended proteins and characterize the structural and subcellular localization changes in the extended protein of BASIC TRANSCRIPTION FACTOR 3. Furthermore, the SCR events exhibit non-conserved signature and the extensions likely undergo protein-coding selection. Overall, our study not only characterizes that SCR events are commonly present in plants but also identifies the unprecedented recoding plasticity of stop codons, which provides important insights into the flexibility of genetic decoding.
2024-02-02 | PXD035958 | Pride
Project description:Here, we use a novel technique for locating regions of N6-adenosine methylation (m6A) throughout the transcriptome and present a profile of m6A sites in the mouse brain. Our use of methylated RNA immunoprecipitation combined with RNA-seq (MeRIP-Seq) identifies thousands of RNAs which contain m6A sites. In addition, we find that regions of m6A formation are particularly enriched near stop codons, which might provide clues into the potential funciton of this highly prevalent RNA modificaiton. Examination of m6A sites in murine brain RNA and human embryonic kidney cells.
2012-12-31 | E-GEOD-34734 | biostudies-arrayexpress
Project description:Here, we use a novel technique for locating regions of N6-adenosine methylation (m6A) throughout the transcriptome and present a profile of m6A sites in the mouse brain. Our use of methylated RNA immunoprecipitation combined with RNA-seq (MeRIP-Seq) identifies thousands of RNAs which contain m6A sites. In addition, we find that regions of m6A formation are particularly enriched near stop codons, which might provide clues into the potential funciton of this highly prevalent RNA modificaiton.
2012-05-17 | GSE29714 | GEO
Project description:The genetic code of mammalian cells can be expanded to allow the incorporation of non-canonical amino acids (ncAAs) by suppressing in-frame amber stop codons (UAG) with an orthogonal pyrrolysyl-tRNA synthetase (PylRS)/tRNAPylCUA (PylT) pair. However, the feasibility of this approach is substantially hampered by unpredictable variations in incorporation efficiencies at different stop codon positions within target proteins. Here, we apply a proteomics-based approach to quantify ncAA incorporation rates at hundreds of endogenous amber stop codons in mammalian cells. With these data, we compute iPASS (Identification of Permissive Amber Sites for Suppression; available at www.bultmannlab.eu/tools/iPASS), a linear regression model to predict relative ncAA incorporation efficiencies depending on the surrounding sequence context. To verify iPASS, we develop a dual-fluorescence reporter for high-throughput flow-cytometry analysis that reproducibly yields context-specific ncAA incorporation efficiencies. We show that nucleotides up- and downstream of UAG synergistically influence ncAA incorporation efficiency independent of cell line and ncAA identity. Additionally, we demonstrate iPASS-guided optimization of ncAA incorporation rates by synonymous exchange of codons flanking the amber stop codon. This combination of in silico analysis followed by validation in living mammalian cells substantially simplifies identification as well as adaptation of sites within a target protein to confer high ncAA incorporation rates.
2021-02-23 | PXD019815 | Pride
Project description:Readthrough of a translation termination codon is regulated by ribosomal A site recognition and insertion of near-cognate tRNAs. Small molecules exist that mediate the incorporation of amino acids at the stop codon and the production of full-length, often functional protein but defining the actual amino acid that is incorporated remains a challenging area. We report on the development of a human cell model that can be used to determine whether rules can be developed using mass spectrometry that defines the type of amino acid that is placed at a premature termination codon during readthrough mediated by an aminoglycoside. The first premature termination codon we analysed contained the relatively common cancer-associated termination signal at codon 213 in the p53 gene. Although we could detect a tryptic peptide with the incorporation of an R at codon 213 in the presence of the aminoglycoside, there were no other tryptic peptides detected across codon 213 that could be recovered so we needed to create a more robust artificial premature stop codon model. P53 expression plasmids were developed that incorporate a string of single synthetic UGA (opal) stop codons at S127P128A129 within the relatively abundant tryptic p53 peptide 122-SVTCTYSPALNK-132. The treatment of cells stably expressing the p53-UGA129 mutation, treated with Gentamycin, followed by immunoprecipitation and trypsinization of p53, resulted in the identification R, W, or C within the tryptic peptide at codon-UGA129; as expected based on the two base pairing of the respective anticodons to UGA with R being the most abundant using all three codons. By contrast, incorporating the amber or ochre premature stop codons, UAA129 or UAG129 resulted in the incorporation of a Y or Q amino acid, again as expected based on the two base pairings to the anticodons, with Q being the most abundant. The incorporation of these amino acids at codons 127, 128, or 129 generally results in a p53 protein that is predicted to be ‘unfolded’ or inactive as defined by Molecular Dynamic Simulations. As such, the data also highlight the need in the future to not only produce novel small molecules that can read through premature termination codons but also the need to design methods to insert the required amino acid at the position that could result in a ‘wild-type’ functional protein.
2024-10-29 | PXD039307 | Pride