Project description:Pbp1 (polyA-binding protein - binding protein 1) is a stress granule marker and polyglutamine expansions in its mammalian ortholog ataxin-2 have been linked to neurodegenerative conditions. Pbp1 was recently shown to form intracellular assemblies that function in the negative regulation of TORC1 signaling under respiratory conditions. Furthermore, it was observed that loss of Pbp1 leads to mitochondrial dysfunction. Here, we show that loss of Pbp1 leads to a specific decrease in mitochondrial proteins whose encoding mRNAs are targets of the RNA-binding protein Puf3, suggesting a functional relationship between Pbp1 and Puf3. We found that Pbp1 stabilizes and promotes the translation of Puf3-target mRNAs in respiratory conditions, such as those involved in the assembly of cytochrome c oxidase. We further show that Pbp1 and Puf3 associate through their respective low complexity domains, which is required for target mRNA stabilization and translation. Our findings reveal a key role for Pbp1-containing assemblies in enabling the translation of mRNAs critical for mitochondrial biogenesis and respiration under metabolically challenging conditions. They may further explain prior associations of Pbp1/ataxin-2 with stress granule biology and RNA metabolism.
Project description:Mitochondrial biogenesis relies on both the nuclear and mitochondrial genomes, and imbalance in their expression can lead to inborn errors of metabolism, inflammation, and aging. Here, we investigate N6AMT1, a nucleo-cytosolic methyltransferase that exhibits genetic codependency with mitochondria. We determine transcriptional and translational profiles of N6AMT1 and report that it is required for the cytosolic translation of TRMT10C (MRPP1) and PRORP (MRPP3), two subunits of the mitochondrial RNAse P enzyme. In the absence of N6AMT1, or when its catalytic activity is abolished, RNA processing within mitochondria is impaired, leading to the accumulation of unprocessed and double-stranded RNA, thus preventing mitochondrial protein synthesis and oxidative phosphorylation, and leading to an immune response. Our work sheds light on the function of N6AMT1 in protein synthesis and highlights a cytosolic program required for proper mitochondrial biogenesis.
Project description:Mitochondrial biogenesis relies on both the nuclear and mitochondrial genomes, and imbalance in their expression can lead to inborn errors of metabolism, inflammation, and aging. Here, we investigate N6AMT1, a nucleo-cytosolic methyltransferase that exhibits genetic codependency with mitochondria. We determine transcriptional and translational profiles of N6AMT1 and report that it is required for the cytosolic translation of TRMT10C (MRPP1) and PRORP (MRPP3), two subunits of the mitochondrial RNAse P enzyme. In the absence of N6AMT1, or when its catalytic activity is abolished, RNA processing within mitochondria is impaired, leading to the accumulation of unprocessed and double-stranded RNA, thus preventing mitochondrial protein synthesis and oxidative phosphorylation, and leading to an immune response. Our work sheds light on the function of N6AMT1 in protein synthesis and highlights a cytosolic program required for proper mitochondrial biogenesis.
Project description:Mitochondrial oxidative phosphorylation (OXPHOS) fuels cellular ATP demands. OXPHOS defects lead to severe human disorders with unexplained tissue specific pathologies. Mitochondrial gene expression is essential for OXPHOS biogenesis since core subunits of the complexes are mitochondrial-encoded. COX14 is required for translation of COX1, the central mitochondrial-encoded subunit of complex IV. Here we generated a COX14 mutant mouse corresponding to a patient with complex IV deficiency. COX14M19I mice display broad tissue-specific pathologies. A hallmark phenotype is severe liver inflammation linked to release of mitochondrial RNA into the cytosol sensed by RIG-1 pathway. We find that mitochondrial RNA release is triggered by increased reactive oxygen species production in the deficiency of complex IV. Additionally, we generated a COA3Y72C mouse, affected in an assembly factor in early COX1 biogenesis, which displayed a similar yet milder inflammatory phenotype. Our study provides mechanistic insight into how defective mitochondrial gene expression causes tissue-specific inflammation.
Project description:Atomic vacancies rich MoS2 nanoflowers stimulate mitochondrial function by reducing cellualr ROS generation and upregulating the expression of genes required for mitochondrial biogenesis.
Project description:Ribosome biogenesis relies on a number of specific factors. Some of them are remarkably conserved, suggesting that they play essential roles even in distant evolutionary contexts. This is namely the case for the UPF0054 protein YBEY found in all bacteria, but also in many Eukarya. Proposed to act as an endoribonuclease processing the 3’ end of 16S rRNA, YBEY is critically required for translation in model bacteria and plant chloroplasts. However, ribosomal RNA processing pathways are poorly conserved between distant phyla, suggesting that YBEY may have another important function in ribosome biogenesis. We studied the human YBEY homologue and found that it localises in mitochondria. The human mitochondrial rRNAs are flanked by tRNA genes and thereby processed by mitochondrial RNase P and RNase Z, making other ribonucleases superfluous. Yet, CRISPR-mediated knockout of the YBEY gene resulted in a decrease of the mitochondrial small ribosomal subunits (SSU), abolished translation in the organelles and, as a result, led to the inability of the knockout cells to respire. Mapping the ends of the mitochondrial rRNAs revealed no processing defects. Similarly, although human YBEY did show robust RNase activity in vitro and in vivo, mutations in key catalytic residues did not abolish its ability to complement the knockout phenotypes. The analysis of the mitoribosomes identified a distinct set of SSU proteins, mostly located in the head and the platform, to be significantly depleted in the absence of YBEY, including uS11m, required for translation initiation. Importantly, uS11m was the only SSU protein found to directly interact with YBEY in vitro, in vivo and in situ, and forming a stable stoichiometric complex with YBEY. The sum of our data supports the model where YBEY functions primarily as an essential ribosome biogenesis factor by recruiting uS11m in order to complete the assembly of translationally active SSUs.
Project description:Caloric restriction (CR) without malnutrition appears to mitigate many detrimental effects of aging, in particular the age-related decline in skeletal muscle mitochondrial function. Although the mechanisms responsible for this protective effect remain unclear, CR is commonly believed to increase mitochondrial biogenesis; a concept that is now demanding closer scrutiny. Here we show that lifelong CR in mice prevents age-related loss of mitochondrial function, measured in isolated mitochondria and permeabilized muscle fibers. We find that these beneficial effects of CR occur without increasing mitochondrial abundance. Furthermore, whole-genome expression profiling and large-scale proteomic surveys revealed expression patterns inconsistent with increased mitochondrial biogenesis. These observations, combined with lower protein synthesis rates support an alternative hypothesis that CR preserves mitochondrial function not by increasing mitochondrial biogenesis, but rather by decreasing mitochondrial oxidant emission, increasing antioxidant scavenging, thereby minimizing oxidative damage to cellular components. Cross-sectional comparison of skeletal muscle from young (8mo), old (24mo) and old caloric restricted mice, obtained from the colony maintained on behalf of the National Institute on Aging.
Project description:Mitochondrial oxidative phosphorylation (OXPHOS) fuels cellular ATP demands. OXPHOS defects lead to severe human disorders with unexplained tissue specific pathologies. Mitochondrial gene expression is essential for OXPHOS biogenesis since core subunits of the complexes are mitochondrial-encoded. COX14 is required for translation of COX1, the central mitochondrial-encoded subunit of complex IV. Here we describe a COX14 mutant mouse corresponding to a patient with complex IV deficiency. COX14M19I mice display broad tissue-specific pathologies. A hallmark phenotype is severe liver inflammation linked to release of mitochondrial RNA into the cytosol sensed by RIG-1 pathway. We find that mitochondrial RNA release is triggered by increased reactive oxygen species production in the deficiency of complex IV. Additionally, we describe a COA3Y72C mouse, affected in an assembly factor that cooperates with COX14 in early COX1 biogenesis, which displays a similar yet milder inflammatory phenotype. Our study provides insight into a link between defective mitochondrial gene expression and tissue-specific inflammation.
Project description:Mitochondrial biogenesis relies on both the nuclear and the mitochondrial genomes, and the mechanisms that support their coordinated expression are not fully understood. Improper mitochondrial DNA expression can lead to inborn error of metabolism, inflammation, and aging. Here, we investigate N6AMT1, a nucleo-cytosolic multi-substrate methyltransferase. We analyze genetic dependency, transcription, translation, and proteomic profiles of N6AMT1-depleted cells and report that N6AMT1 is necessary for the cytosolic translation of factors involved in mitochondrial RNA metabolism, including subunits of the mitochondrial RNase P. In the absence of N6AMT1, RNA processing and translation within mitochondria are impaired, while double-stranded RNA accumulates in mitochondrial RNA granules causing an interferon response. Our work highlights a cytosolic program required for proper mitochondrial biogenesis, with consequences on innate immunity.