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Coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes is assisted by mtCLPXP in Arabidopsis thaliana

ABSTRACT: Protein homeostasis in eukaryotic organelles and their progenitor prokaryotes is regulated by a series of ATP-dependent proteases including the caseinolytic protease complex (ClpXP). In chloroplasts, ClpXP has essential roles in organelle biogenesis and maintenance , but the significance of the plant mitochondrial ClpXP remains unknown and factors that aid coordination of nuclear and mitochondrial encoded subunits for complex assembly in mitochondria await discovery. In this study, we generated knock-out lines of the single copy mitochondrial Clp protease subunit, CLPP2, in Arabidopsis thaliana. They have higher abundance of transcripts from mitochondrial genes encoding OXPHOS protein complexes, while transcripts for nuclear genes encoding other subunits of the same complexes showed no change in transcript abundance. In contrast, the protein abundance of specific nuclear-encoded subunits in OXPHOS complexes I and V increased in knockouts, without accumulation of mitochondrial-encoded counterparts in the same complex. Protein complexes mainly or wholly encoded in the nucleus were unaffected. Analysis of protein import, assembly and function of Complex I revealed that while function was retained, protein homeostasis was disrupted through slower assembly, leading to accumulation of soluble subcomplexes of nuclear-encoded subunits after import. It is proposed that CLPP contributes to the mitochondrial protein degradation network through supporting coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE141942 | GEO | 2019/12/13

REPOSITORIES: GEO

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Coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes is assisted by mtCLPP in Arabidopsis thaliana.

Project description:Protein homeostasis in eukaryotic organelles and their progenitor prokaryotes is regulated by a series of proteases including the caseinolytic protease (CLPP). CLPP has essential roles in chloroplast biogenesis and maintenance, but the significance of the plant mitochondrial CLPP remains unknown and factors that aid coordination of nuclear and mitochondrial encoded subunits for complex assembly in mitochondria await discovery. We generated knock-out lines of the single copy mitochondrial CLP protease subunit, CLPP2, in Arabidopsis thaliana. Mutants have higher abundance of transcripts from mitochondrial genes encoding OXPHOS protein complexes, while transcripts for nuclear genes encoding other subunits of the same complexes showed no change in transcript abundance. In contrast, the protein abundance of specific nuclear-encoded subunits in OXPHOS complexes I and V increased in knockouts, without accumulation of mitochondrial-encoded counterparts in the same complex. Protein complexes mainly or entirely encoded in the nucleus were unaffected. Analysis of protein import, assembly and function of Complex I revealed that while function was retained, protein homeostasis was disrupted through slower assembly, leading to accumulation of soluble subcomplexes of nuclear-encoded subunits. Therefore, CLPP2 contributes to the mitochondrial protein degradation network through supporting coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes.

2020-09-14 | PXD016746 | Pride

The mitochondrial CLPXP complex supports the coordination and assembly of mitochondrial and nuclear encoded protein complexes in Arabidopsis thaliana

Project description:The mitochondrial CLPXP complex supports the coordination and assembly of mitochondrial and nuclear encoded protein complexes in Arabidopsis thaliana. Protein labeling using iTRAQ reagents and application of optimized ChaFRADIC technology to enrich N-Terminal peptides.

2020-09-14 | PXD016263 | Pride

Regulators of mitonuclear balance link mitochondrial metabolism to mtDNA expression

Project description:Mitochondrial oxidative phosphorylation (OXPHOS) complexes are assembled from proteins encoded by both nuclear and mitochondrial DNA. These dual-origin enzymes pose a complex gene regulatory challenge for cells requiring coordinated gene expression across organelles. To identify genes involved in dual-origin protein complex synthesis, we performed FACS-based genome-wide screens analyzing mutant cells with unbalanced levels of mitochondrial- and nuclear-encoded subunits of Complex IV. We identified novel genes involved in OXPHOS biogenesis, including two uncharacterized genes: PREPL and NME6. We found that PREPL specifically impacts Complex IV biogenesis by acting at the intersection of mitochondrial lipid metabolism and protein synthesis, while NME6, an uncharacterized nucleoside diphosphate kinase (NDPK), controls OXPHOS biogenesis through multiple mechanisms reliant on its NDPK domain. First, NME6 forms a complex with RCC1L, which together perform NDPK activity to maintain local mitochondrial pyrimidine triphosphate levels essential for mitochondrial RNA abundance. Second, NME6 modulates the activity of mitoribosome regulatory complexes, altering mitoribosome assembly and mitochondrial RNA pseudouridylation. Taken together, we propose that NME6 acts as a link between compartmentalized mitochondrial metabolites and mitochondrial gene expression.

2023-08-17 | GSE224818 | GEO

Regulators of mitonuclear balance link mitochondrial metabolism to mtDNA expression

2023-08-17 | GSE224817 | GEO

Regulators of mitonuclear balance link mitochondrial metabolism to mtDNA expression

Project description:Mitochondrial oxidative phosphorylation (OXPHOS) complexes are assembled from proteins encoded by both nuclear and mitochondrial DNA. These dual-origin enzymes pose a complex gene regulatory challenge for cells requiring coordinated gene expression across organelles. To identify genes involved in dual-origin protein complex synthesis, we performed fluorescence-activated cell-sorting-based genome-wide screens analysing mutant cells with unbalanced levels of mitochondrial- and nuclear-encoded subunits of Complex IV. We identified genes involved in OXPHOS biogenesis, including two uncharacterized genes: PREPL and NME6. We found that PREPL specifically impacts Complex IV biogenesis by acting at the intersection of mitochondrial lipid metabolism and protein synthesis, whereas NME6, an uncharacterized nucleoside diphosphate kinase, controls OXPHOS biogenesis through multiple mechanisms reliant on its NDPK domain. Firstly, NME6 forms a complex with RCC1L, which together perform nucleoside diphosphate kinase activity to maintain local mitochondrial pyrimidine triphosphate levels essential for mitochondrial RNA abundance. Secondly, NME6 modulates the activity of mitoribosome regulatory complexes, altering mitoribosome assembly and mitochondrial RNA pseudouridylation. Taken together, we propose that NME6 acts as a link between compartmentalized mitochondrial metabolites and mitochondrial gene expression.

2023-08-17 | GSE224503 | GEO

Regulators of mitonuclear balance link mitochondrial metabolism to mtDNA expression

2023-08-17 | GSE240576 | GEO

Comparative analysis of transcripts from mia40-4int mutant and wild-type Saccharomyces cerevisiae strains quantified in RNA-seq experiment

Project description:The vast majority of the mitochondrial proteome originates from nuclear genes and is transported into the organelle after synthesis in the cytosol. Complex machineries, which maintain the specificity of protein import and sorting exist. Dysfunctions of mitochondrial protein sorting pathways result in diminishing specific substrate proteins, followed by systemic pathology of the organelle and organismal death. Cellular responses that are caused by slowdown in the transport of mitochondrial proteins are unknown. Here we have used RNA-seq transcription profiling of Saccharomyces cerevisiae to uncover the changes in the cellular transcriptome in the response to mitochondrial protein import dysfunction caused by mutation in the MIA40 gene. Mia40 is a key component of the mitochondrial intermembrane import and assembly (MIA) pathway. Mia40-4int mutant used in this study is not viable at high temperatures, while in the low, permissive temperature it expresses growth rate comparable to the wild-type strain. Even during the permissive temperature culture mutant cells are characterized by decreased accumulation of MIA substrate proteins. Thus permissive growth conditions were used in the present experiment to emphasise primary responses to mitochondrial protein import defect.

2015-07-31 | E-MTAB-3588 | biostudies-arrayexpress

Fidelity of translation initiation is required for coordinated respiratory complex assembly

Project description:Mammalian mitochondrial ribosomes are unique molecular machines that translate 11 leaderless mRNAs. To date it is not clear how mitoribosomes recognize and initiate translation in the absence of untranslated regions in the mitochondrial mRNAs. Translation initiation in mitochondria shares similarities with prokaryotic systems, such as the formation of a ternary complex of fMet-tRNAMet, mRNA and the 28S subunit, but differs in the requirements for initiation factors. Mitochondria have two initiation factors, MTIF2 that closes the decoding centre and stabilizes the binding of the fMet-tRNAMet to the leaderless mRNAs, and MTIF3 whose role is not clear. We knocked out Mtif3 in mice and show that this protein is essential for embryo development and heart- and skeletal muscle-specific loss of MTIF3 causes premature death. We identify increased but uncoordinated mitochondrial protein synthesis in mice lacking MTIF3 that results in loss of specific respiratory complexes. Therefore, we show that coordinated assembly of OXPHOS complexes requires stoichiometric levels of nuclear and mitochondrially-encoded protein subunits in vivo. Our ribosome profiling and transcriptomic analyses show that MTIF3 is required for recognition and regulation of translation initiation of mitochondrial mRNAs, but not dissociation of the ribosome subunits.

2020-01-13 | GSE131154 | GEO

Regulators of mitonuclear balance link mitochondrial metabolism to mtDNA expression

2023-08-23 | PXD044812 | Pride

Profiling of mRNA localization of nuclear-encoded mitochondrial proteins in zebrafish.

Project description:Current evidence suggests that nuclear-encoded mitochondrial proteins can be locally translated at the mitochondrial surface and co-translationally or post-translationally imported into mitochondria. mRNA localization on the mitochondrial membrane, a prerequisite for localized translation, remains uncharacterized in higher eukaryotic organisms. We employed fractionation-sequencing to profile mitochondria-associated mRNAs in zebrafish larvae. Our transcriptome-wide analysis reveals the localization of mRNAs of only 12% of the nuclear-encoded mitochondrial proteins to the mitochondrial surface, which suggests that post-translational import is the dominant mode of protein import to mitochondria. Additionally, the mRNAs which were localized to the mitochondrial membrane consisted mostly of those encoding proteins involved in mitochondrial dynamics, suggesting their site-specific translation. Finally, we show that the loss of function of the MIA pathway responsible for the post-translational import of a subclass of mitochondrial proteins, triggers mitochondrial localization of mRNAs encoding proteins that are imported to mitochondria via other pathways. Thus, our study suggests that mRNA targeting and localized translation could be relevant in higher eukaryotes to combat stress conditions affecting mitochondrial biogenesis in general.

2023-10-28 | GSE160355 | GEO

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