title: Dual targeting of isoleucyl-tRNA synthetase in Trypanosoma brucei is mediated through alternative trans-splicing.
abstract: Aminoacyl-tRNA synthetases catalyze the aminoacylation of tRNAs with their cognate amino acids. They are an essential part of each translation system and in eukaryotes are therefore found in both the cytosol and mitochondria. Thus, eukaryotes either have two distinct genes encoding the cytosolic and mitochondrial isoforms of each of these enzymes or a single gene encoding dually localized products. Trypanosomes require trans-splicing of a cap containing leader sequence onto the 5'-untranslated region of every mRNA. Recently we speculated that alternative trans-splicing could lead to the expression of proteins having amino-termini of different lengths that derive from the same gene. We now demonstrate that alternative trans-splicing, creating a long and a short spliced variant, is the mechanism for dual localization of trypanosomal isoleucyl-tRNA synthetase (IleRS). The protein product of the longer spliced variant possesses an amino-terminal presequence and is found exclusively in mitochondria. In contrast, the shorter spliced variant is translated to a cytosol-specific isoform lacking the presequence. Furthermore, we show that RNA stability is one mechanism determining the differential abundance of the two spliced isoforms.
authors: Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
authors: Jochen
authors: J
authors: Rettig
authors: Yimu
authors: Y
authors: Wang
authors: André
authors: A
authors: Schneider
authors: Torsten
authors: T
authors: Ochsenreiter
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology; D007533:Isoleucine-tRNA Ligase / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism; D020040:Trans-Splicing; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics*
chemical_list: D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D015800:Protozoan Proteins; D012333:RNA, Messenger; D007533:Isoleucine-tRNA Ligase