Elongation factor 1a mediates the specificity of mitochondrial tRNA import in T. brucei

• Published in: The EMBO journal Vol. 26; no. 20; pp. 4302 - 4312
• Main Authors: Bouzaidi-Tiali, Nabile, Aeby, Eric, Charrière, Fabien, Pusnik, Mascha, Schneider, André
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 17-10-2007; Blackwell Publishing Ltd; Nature Publishing Group
• Subjects: Animals; Base Sequence; Biochemistry - methods; Cellular biology; Cytosol - metabolism; elongation factor1a; Inhibitor drugs; Mitochondria - metabolism; mitochondrial biogenesis; Models, Biological; Molecular biology; Molecular Sequence Data; Nucleic Acid Conformation; Peptide Elongation Factor 1 - physiology; RNA Interference; RNA, Transfer - chemistry; RNA, Transfer - metabolism; Selenocysteine - chemistry; selenocysteine tRNA; Subcellular Fractions - metabolism; tRNA; Trypanosoma - metabolism; Trypanosoma brucei; Trypanosoma brucei brucei - metabolism; trypanosomes
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/sj.emboj.7601857

Mitochondrial tRNA import is widespread in eukaryotes. Yet, the mechanism that determines its specificity is unknown. Previous in vivo experiments using the tRNAsMet, tRNAIle and tRNALys have suggested that the T‐stem nucleotide pair 51:63 is the main localization determinant of tRNAs in Trypanosoma brucei. In the cytosol‐specific initiator tRNAMet, this nucleotide pair is identical to the main antideterminant that prevents interaction with cytosolic elongation factor (eEF1a). Here we show that ablation of cytosolic eEF1a, but not of initiation factor 2, inhibits mitochondrial import of newly synthesized tRNAs well before translation or growth is affected. tRNASec is the only other cytosol‐specific tRNA in T. brucei. It has its own elongation factor and does not bind eEF1a. However, a mutant of the tRNASec expected to bind to eEF1a is imported into mitochondria. This import requires eEF1a and aminoacylation of the tRNA. Thus, for a tRNA to be imported into the mitochondrion of T. brucei, it needs to bind eEF1a, and it is this interaction that mediates the import specificity.