| 1. |
- Gruschke, Steffi, et al.
(författare)
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Cbp3-Cbp6 interacts with the yeast mitochondrial ribosomal tunnel exit and promotes cytochrome b synthesis and assembly
- 2011
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Ingår i: Journal of Cell Biology. - : Rockefeller University Press. - 0021-9525 .- 1540-8140. ; 193:6, s. 1101-1114
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondria contain their own genetic system to express a small number of hydrophobic polypeptides, including cytochrome b, an essential subunit of the bc(1) complex of the respiratory chain. In this paper, we show in yeast that Cbp3, a bc(1) complex assembly factor, and Cbp6, a regulator of cytochrome b translation, form a complex that associates with the polypeptide tunnel exit of mitochondrial ribosomes and that exhibits two important functions in the biogenesis of cytochrome b. On the one hand, the interaction of Cbp3 and Cbp6 with mitochondrial ribosomes is necessary for efficient translation of cytochrome b messenger ribonucleic acid or transcript. On the other hand, the Cbp3-Cbp6 complex interacts directly with newly synthesized cytochrome b in an assembly intermediate that is not ribosome bound and that contains the assembly factor Cbp4. Our results suggest that synthesis of cytochrome b occurs preferentially on those ribosomes that have the Cbp3-Cbp6 complex bound to their tunnel exit, an arrangement that may ensure tight coordination of cytochrome b synthesis and assembly.
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| 2. |
- Gruschke, Steffi, et al.
(författare)
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Proteins at the Polypeptide Tunnel Exit of the Yeast Mitochondrial Ribosome
- 2010
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 285:25, s. 19022-19028
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative phosphorylation in mitochondria requires the synthesis of proteins encoded in the mitochondrial DNA. The mitochondrial translation machinery differs significantly from that of the bacterial ancestor of the organelle. This is especially evident from many mitochondria-specific ribosomal proteins. An important site of the ribosome is the polypeptide tunnel exit. Here, nascent chains are exposed to an aqueous environment for the first time. Many biogenesis factors interact with the tunnel exit of pro- and eukaryotic ribosomes to help the newly synthesized proteins to mature. To date, nothing is known about the organization of the tunnel exit of mitochondrial ribosomes. We therefore undertook a comprehensive approach to determine the composition of the yeast mitochondrial ribosomal tunnel exit. Mitochondria contain homologues of the ribosomal proteins located at this site in bacterial ribosomes. Here, we identified proteins located in their proximity by chemical cross-linking and mass spectrometry. Our analysis revealed a complex network of interacting proteins including proteins and protein domains specific to mitochondrial ribosomes. This network includes Mba1, the membrane-bound ribosome receptor of the inner membrane, as well as Mrpl3, Mrpl13, and Mrpl27, which constitute ribosomal proteins exclusively found in mitochondria. This unique architecture of the tunnel exit is presumably an adaptation of the translation system to the specific requirements of the organelle.
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| 3. |
- Heublein, Manfred, et al.
(författare)
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The novel component Kgd4 recruits the E3 subunit to the mitochondrial alpha-ketoglutarate dehydrogenase
- 2014
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Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 25:21, s. 3342-3349
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial citric acid cycle is a central hub of cellular metabolism, providing intermediates for biosynthetic pathways and channeling electrons to the respiratory chain complexes. In this study, we elucidated the composition and organization of the multienzyme complex alpha-ketoglutarate dehydrogenase (alpha-KGDH). In addition to the three classical E1-E3 subunits, we identified a novel component, Kgd4 (Ymr31/MRPS36), which was previously assigned to be a subunit of the mitochondrial ribosome. Biochemical analyses demonstrate that this protein plays an evolutionarily conserved role in the organization of mitochondrial alpha-KGDH complexes of fungi and animals. By binding to both the E1-E2 core and the E3 subunit, Kgd4 acts as a molecular adaptor that is necessary to a form a stable alpha-KGDH enzyme complex. Our work thus reveals a novel subunit of a key citric acid-cycle enzyme and shows how this large complex is organized.
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| 4. |
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| 5. |
- Kohler, Verena, 1992-, et al.
(författare)
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Nuclear Hsp104 safeguards the dormant translation machinery during quiescence
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- The resilience of cellular proteostasis declines with age, which drives protein aggregation and compromises viability. The nucleus has emerged as a key quality control compartment that handles misfolded proteins produced by the cytosolic protein biosynthesis system. Here, we find that age-associated metabolic cues target the yeast protein disaggregase Hsp104 to the nucleus to maintain a functional nuclear proteome during quiescence. The switch to respiratory metabolism and the accompanying decrease in translation rates direct cytosolic Hsp104 to the nucleus to interact with latent translation initiation factor eIF2 and to suppress protein aggregation. Hindering Hsp104 from entering the nucleus in quiescent cells results in delayed re-entry into the cell cycle due to compromised resumption of protein synthesis. In sum, we report that cytosolic-nuclear partitioning of the Hsp104 disaggregase is a critical mechanism to protect the latent protein synthesis machinery during quiescence in yeast, ensuring the rapid restart of translation once nutrients are replenished.
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| 6. |
- Lahiri, Shibojyoti, et al.
(författare)
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MALDI-IMS combined with shotgun proteomics identify and localize new factors in male infertility.
- 2021
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Ingår i: Life science alliance. - 2575-1077. ; 4:3
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Tidskriftsartikel (refereegranskat)abstract
- Spermatogenesis is a complex multi-step process involving intricate interactions between different cell types in the male testis. Disruption of these interactions results in infertility. Combination of shotgun tissue proteomics with MALDI imaging mass spectrometry is markedly potent in revealing topological maps of molecular processes within tissues. Here, we use a combinatorial approach on a characterized mouse model of hormone induced male infertility to uncover misregulated pathways. Comparative testicular proteome of wild-type and mice overexpressing human P450 aromatase (AROM+) with pathologically increased estrogen levels unravels gross dysregulation of spermatogenesis and emergence of pro-inflammatory pathways in AROM+ testis. In situ MS allowed us to localize misregulated proteins/peptides to defined regions within the testis. Results suggest that infertility is associated with substantial loss of proteomic heterogeneity, which define distinct stages of seminiferous tubuli in healthy animals. Importantly, considerable loss of mitochondrial factors, proteins associated with late stages of spermatogenesis and steroidogenic factors characterize AROM+ mice. Thus, the novel proteomic approach pinpoints in unprecedented ways the disruption of normal processes in testis and provides a signature for male infertility.
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| 7. |
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| 8. |
- Salvatori, Roger, 1988, et al.
(författare)
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Mapping protein networks in yeast mitochondria using proximity-dependent biotin identification coupled to proteomics
- 2020
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Ingår i: STAR PROTOCOLS. - : Elsevier BV. - 2666-1667. ; 1:3
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Tidskriftsartikel (refereegranskat)abstract
- Proximity-dependent biotin identification (BioID) permits biotinylation of proteins interacting directly, indirectly, or just localized in proximity of a protein of interest (bait). Here, we describe how BioID coupled to proteomics and network biology can be used to map protein proximities in yeast mitochondria, aiding in visualization of complex protein-protein interaction landscapes. For complete information on the use and execution of this protocol, please refer to Singh et al., 2020.
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| 9. |
- Salvatori, Roger, et al.
(författare)
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Molecular Wiring of a Mitochondrial Translational Feedback Loop
- 2020
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 77:4, s. 887-900
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Tidskriftsartikel (refereegranskat)abstract
- The mitochondrial oxidative phosphorylation system comprises complexes assembled from subunits derived from mitochondrial and nuclear gene expression. Both genetic systems are coordinated by feedback loops, which control the synthesis of specific mitochondrial encoded subunits. Here, we studied how this occurs in the case of cytochrome b, a key subunit of mitochondrial complex III. Our data suggest the presence of a molecular rheostat consisting of two translational activators, Cbp3-Cbp6 and Cbs1, which operates at the mitoribosomal tunnel exit to connect translational output with assembly efficiency. When Cbp3-Cbp6 is engaged in assembly of cytochrome b, Cbs1 binds to the tunnel exit to sequester the cytochrome b-encoding mRNA, repressing its translation. After mediating complex III assembly, binding of Cbp3-Cbp6 to the tunnel exit replaces Cbs1 and the bound mRNA to permit cytochrome b synthesis. Collectively, the data indicate the molecular wiring of a feedback loop to regulate synthesis of a mitochondrial encoded protein.
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| 10. |
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| 11. |
- Stabell, Marianne, et al.
(författare)
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The Drosophila G9a gene encodes a multi-catalytic histone methyltransferase required for normal development.
- 2006
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Ingår i: Nucleic Acids Res. - 1362-4962. ; 34:16, s. 4609-21
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Tidskriftsartikel (refereegranskat)abstract
- Mammalian G9a is a histone H3 Lys-9 (H3-K9) methyltransferase localized in euchromatin and acts as a co-regulator for specific transcription factors. G9a is required for proper development in mammals as g9a-/g9a- mice show growth retardation and early lethality. Here we describe the cloning, the biochemical and genetical analyses of the Drosophila homolog dG9a. We show that dG9a shares the structural organization of mammalian G9a, and that it is a multi-catalytic histone methyltransferase with specificity not only for lysines 9 and 27 on H3 but also for H4. Surprisingly, it is not the H4-K20 residue that is the target for this methylation. Spatiotemporal expression analyses reveal that dG9a is abundantly expressed in the gonads of both sexes, with no detectable expression in gonadectomized adults. In addition we find a low but clearly observable level of dG9a transcript in developing embryos, larvae and pupae. Genetic and RNAi experiments reveal that dG9a is involved in ecdysone regulatory pathways.
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| 12. |
- Vargas Möller-Hergt, Braulio, et al.
(författare)
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The ribosome receptors Mrx15 and Mba1 jointly organize cotranslational insertion and protein biogenesis in mitochondria
- 2018
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Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 29:20, s. 2359-2507
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Tidskriftsartikel (refereegranskat)abstract
- 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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