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Sökning: WFRF:(Amunts Alexey)

  • Resultat 21-28 av 28
  • Föregående 12[3]
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21.
  • Petrov, Anton S., et al. (författare)
  • Structural Patching Fosters Divergence of Mitochondrial Ribosomes
  • 2019
  • Ingår i: Molecular biology and evolution. - 0737-4038 .- 1537-1719. ; 36:2, s. 207-219
  • Tidskriftsartikel (refereegranskat)abstract
    • Mitochondrial ribosomes (mitoribosomes) are essential components of all mitochondria that synthesize proteins encoded by the mitochondrial genome. Unlike other ribosomes, mitoribosomes are highly variable across species. The basis for this diversity is not known. Here, we examine the composition and evolutionary history of mitoribosomes across the phylogenetic tree by combining three-dimensional structural information with a comparative analysis of the secondary structures of mitochondrial rRNAs (mt-rRNAs) and available proteomic data. We generate a map of the acquisition of structural variation and reconstruct the fundamental stages that shaped the evolution of the mitoribosomal large subunit and led to this diversity. Our analysis suggests a critical role for ablation and expansion of rapidly evolving mt-rRNA. These changes cause structural instabilities that are patched by the acquisition of pre-existing compensatory elements, thus providing opportunities for rapid evolution. This mechanism underlies the incorporation of mt-tRNA into the central protuberance of the mammalian mitoribosome, and the altered path of the polypeptide exit tunnel of the yeast mitoribosome. We propose that since the toolkits of elements utilized for structural patching differ between mitochondria of different species, it fosters the growing divergence of mitoribosomes.
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22.
  • Sighel, Denise, et al. (författare)
  • Inhibition of mitochondrial translation suppresses glioblastoma stem cell growth
  • 2021
  • Ingår i: Cell reports. - 2211-1247 .- 2211-1247. ; 35:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Glioblastoma stem cells (GSCs) resist current glioblastoma (GBM) therapies. GSCs rely highly on oxidative phosphorylation (OXPHOS), whose function requires mitochondrial translation. Here we explore the therapeutic potential of targeting mitochondrial translation and report the results of high-content screening with putative blockers of mitochondrial ribosomes. We identify the bacterial antibiotic quinupristin/dalfopristin (Q/D) as an effective suppressor of GSC growth. Q/D also decreases the clonogenicity of GSCs in vitro, consequently dysregulating the cell cycle and inducing apoptosis. Cryoelectron microscopy (cryo-EM) reveals that Q/D binds to the large mitoribosomal subunit, inhibiting mitochondrial protein synthesis and functionally dysregulating OXPHOS complexes. These data suggest that targeting mitochondrial translation could be explored to therapeutically suppress GSC growth in GBM and that Q/D could potentially be repurposed for cancer treatment.
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23.
  • Tobiasson, Victor, et al. (författare)
  • Ciliate mitoribosome illuminates evolutionary steps of mitochondrial translation
  • 2020
  • Ingår i: eLIFE. - 2050-084X. ; 9
  • Tidskriftsartikel (refereegranskat)abstract
    • To understand the steps involved in the evolution of translation, we used Tetrahymena thermophila, a ciliate with high coding capacity of the mitochondrial genome, as the model organism and characterized its mitochondrial ribosome (mitoribosome) using cryo-EM. The structure of the mitoribosome reveals an assembly of 94-ribosomal proteins and four-rRNAs with an additional protein mass of ~700 kDa on the small subunit, while the large subunit lacks 5S rRNA. The structure also shows that the small subunit head is constrained, tRNA binding sites are formed by mitochondria-specific protein elements, conserved protein bS1 is excluded, and bacterial RNA polymerase binding site is blocked. We provide evidence for anintrinsic protein targeting system through visualization of mitochondria-specific mL105 by the exit tunnel that would facilitate the recruitment of a nascent polypeptide. Functional protein uS3m is encoded by three complementary genes from the nucleus and mitochondrion, establishing a link between genetic drift and mitochondrial translation. Finally, we reannotated nine open reading frames in the mitochondrial genome that code for mitoribosomal proteins.
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25.
  • Tobiasson, Victor, et al. (författare)
  • Interconnected assembly factors regulate the biogenesis of mitoribosomal large subunit
  • 2021
  • Ingår i: EMBO Journal. - 0261-4189 .- 1460-2075. ; 40:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Mitoribosomes consist of ribosomal RNA and protein components, coordinated assembly of which is critical for function. We used mitoribosomes from Trypanosoma brucei with reduced RNA and increased protein mass to provide insights into the biogenesis of the mitoribosomal large subunit. Structural characterization of a stable assembly intermediate revealed 22 assembly factors, some of which have orthologues/counterparts/homologues in mammalian genomes. These assembly factors form a protein network that spans a distance of 180 angstrom, shielding the ribosomal RNA surface. The central protuberance and L7/L12 stalk are not assembled entirely and require removal of assembly factors and remodeling of the mitoribosomal proteins to become functional. The conserved proteins GTPBP7 and mt-EngA are bound together at the subunit interface in proximity to the peptidyl transferase center. A mitochondrial acyl-carrier protein plays a role in docking the L1 stalk, which needs to be repositioned during maturation. Additional enzymatically deactivated factors scaffold the assembly while the exit tunnel is blocked. Together, this extensive network of accessory factors stabilizes the immature sites and connects the functionally important regions of the mitoribosomal large subunit.
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26.
  • Tobiasson, Victor, 1994- (författare)
  • On the Origin and Evolution of the Mitochondrial Ribosome
  • 2022
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The ribosome is among the most ancient, intricate and well studied macromolecular complexes in biology. Predating the earliest divergence of life, its core molecular structure has remained mostly unchanged for more than three billion years. In stark contrast to its monolithic ancestor, the mitochondrial ribosome represents one of the most architecturally diverse protein complexes investigated. This work is an attempt at reconciling these two paradigms. In this thesis I first briefly cover the evolutionary history of the mitochondrial ribosome: from its ancient origins, through the process of Eukaryogenesis and the development of mitochondria, to its current state. Following this I present a comprehensive and integrated comparative analysis of the current mitoribosomal structures. Using these structural observations as a starting point I then summarise the current knowledge regarding the evolutionary trends of mitochondrial ribosomes. Finally I review and discuss potential genetic mechanisms and evolutionary pressures which could have produced such a vibrant diversity of structures. Together with this analysis I present monosome structures from the ciliate Tetrahymena thermophila and chlorophycean Polytomella magna together with an assembly intermediate of the large subunit from Trypanosoma brucei. Together, I hope to demonstrate the impact of the unique mitochondrial environment on the evolution of the mitochondrial ribosome. 
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27.
  • Tobiasson, Victor, et al. (författare)
  • Structure of a mitochondrial ribosome with fragmented rRNA in complexwith membrane-targeting elements
  • Annan publikation (övrigt vetenskapligt)abstract
    • Mitoibosomes of green alga belong to a diverged type with extreme fragmentation in rRNA andprotein material. We present a 2.9-Å resolution structure of an algal mitoribosome with reducedrRNA that is split in to 13 fragments. The architecture features a fragmentation pattern that hassimilarities with apicomplexan parasites. The unique phenomena of the rRNA include permutationand incorporation of a non-canonical and reduced mt-5S rRNA. On the protein level, elevenperipherally associated HEAT-repeat proteins involved in rRNA binding, and a specific trimer ofmL116 binds 3’ termini of three rRNA fragments. In the exit tunnel, mL128 constricts the path,and mL105 a homolog of a membrane targeting component mediates contacts with an innermembrane-bound insertase. Although overall protein content at the tunnel exit site of themitoribosome varies among eukaryotes, we find that the mechanisms of the constriction andmembrane tethering are shared between the algal and mammalian lineages. Therefore, our datareveals characteristics of fragmented rRNA an unexpected convergent evolution in the regulationof protein synthesis in mitochondria.
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  • Resultat 21-28 av 28
  • Föregående 12[3]

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