trypanosoma; mitochondria; transfer RNA; transport of macromolecules; trypanosomes; tRNA; transport; parasites; organellar translation
Pusnik Mascha, Schneider André (2011), A Trypanosomal Pentatricopeptide Repeat Protein Stabilizes the Mitochondrial mRNAs of Cytochrome Oxidase Subunits 1 and 2., in Eukaryotic cell
, 11(1), 79-87.
Tschopp Florence, Charrière Fabien, Schneider André (2011), In vivo study in Trypanosoma brucei links mitochondrial transfer RNA import to mitochondrial protein import., in EMBO reports
, 12(8), 825-32.
Pusnik Mascha, Schmidt Oliver, Perry Andrew J, Oeljeklaus Silke, Niemann Moritz, Warscheid Bettina, Lithgow Trevor, Meisinger Chris, Schneider André (2011), Mitochondrial preprotein translocase of trypanosomatids has a bacterial origin., in Current biology : CB
, 21(20), 1738-43.
Niemann Moritz, Schneider André, Cristodero Marina (2011), Mitochondrial translation in trypanosomatids: a novel target for chemotherapy?, in Trends in parasitology
, 27(10), 429-33.
Schneider André (2011), Mitochondrial tRNA import and its consequences for mitochondrial translation., in Annual review of biochemistry
, 80, 1033-53.
Rettig Jochen, Wang Yimu, Schneider André, Ochsenreiter Torsten, Dual targeting of isoleucyl-tRNA synthetase in Trypanosoma brucei is mediated through alternative trans-splicing., in Nucleic acids research
SummaryMy research group is working on mitochondrial biogenesis using the parasitic protozoa Trypanosoma brucei as a model. T. brucei and its relatives belong to the earliest diverging branches of the eukaryotic evolutionary tree, which have bona fide mitochondria involved in oxidative phosphorylation. Their mitochondrion therefore shows many peculiarities. This proposal focuses on three of them: (i) a complete lack of mitochondrial tRNA genes that is compensated by import of cytosolic tRNAs, (ii) an apparently minimized mitochondrial protein import system, and (iii) a striking expansion - when compared to non-plant eukaryotes - of a protein family, the pentatricopeptide repeat (PPR) proteins, postulated to bind to specific organellar RNAs. Mitochondrial tRNA importWe have shown that cytosolic elongation factor 1a (eEF1a) is necessary to determine the specificity of mitochondrial tRNA import. We would now like to understand the mechanism by which the specificity is determined and whether eEF1a acts in concert with other proteins. Different tRNAs are imported to very different extents. We intend to investigate how these extents are determined. Furthermore, we plan to identify the components of the tRNA import machinery and to investigate the mechanism of the import process. Finally, we want to understand how imported eukaryotic-type tRNAs are integrated into the bacterial-type translation system of the mitochondrion. Here we will focus on the extended substrate specificities of some mitochondrial aminoacyl-tRNA synthetases and on the role of a trypanosomatid-specific insertion in mitochondrial elongation factor Tu. - We expect that studying the questions mentioned above will uncover conserved concepts of mitochondrial tRNA import that are valid in all systems.Mitochondrial protein importA genome analysis revealed two aspects where the protein import pathway of T. brucei appears simpler than what is found in other mitochondria. These are the apparent absence of a conventional outer membrane translocase and the existence of only a single inner membrane translocase. We propose to characterize the translocase that imports proteins across the outer membrane in T. brucei. Furthermore we would like to show that both insertion of membrane proteins and translocation of matrix proteins are mediated by a single inner membrane translocase. - The suggested studies are likely to give us more insight into the enigmatic evolutionary origin of mitochondrial protein import in general. PPR proteinsT. brucei contains almost an order of magnitude more PPR proteins than all other non-plant eukaryotes. We have characterized six trypanosomal PPR proteins that are predicted to bind mitochondrial rRNAs. We intend to test this binding directly and determine the minimal RNA sequences it requires. Furthermore, we intend to characterize interacting partners of PPRs proteins and, finally, would like to initiate structural studies. - We hope that these studies will help to determine whether PPR proteins indeed are sequence specific RNA binding proteins.Key experimental approachesWhile the three subprojects focus on different aspects of mitochondrial biogenesis they are linked by a set of shared experimental approaches. These are: Influence of RNAi-mediated ablation of putative tRNA or protein import factors on import of a newly synthesized tRNA or protein in vivo; In vitro import systems for tRNA and proteins; Blue native gels and tandem affinity purification of tagged proteins to characterize protein complexes and the production of recombinant proteins for various in vitro assays as well as for structural studies.