Yeast mitochondrial Gln-tRNA(Gln) is generated by a GatFAB-mediated transamidation pathway involving Arc1p-controlled subcellular sorting of cytosolic GluRS.
It is impossible to predict which pathway, direct glutaminylation of tRNA(Gln) or tRNA-dependent transamidation of glutamyl-tRNA(Gln), generates mitochondrial glutaminyl-tRNA(Gln) for protein synthesis in a given species. The report that yeast mitochondria import both cytosolic glutaminyl-tRNA synthetase and tRNA(Gln) has challenged the widespread use of the transamidation pathway in organelles. Here we demonstrate that yeast mitochondrial glutaminyl-tRNA(Gln) is in fact generated by a transamidation pathway involving a novel type of trimeric tRNA-dependent amidotransferase (AdT). More surprising is the fact that cytosolic glutamyl-tRNA synthetase ((c)ERS) is imported into mitochondria, where it constitutes the mitochondrial nondiscriminating ERS that generates the mitochondrial mischarged glutamyl-tRNA(Gln) substrate for the AdT. We show that dual localization of (c)ERS is controlled by binding to Arc1p, a tRNA nuclear export cofactor that behaves as a cytosolic anchoring platform for (c)ERS. Expression of Arc1p is down-regulated when yeast cells are switched from fermentation to respiratory metabolism, thus allowing increased import of (c)ERS to satisfy a higher demand of mitochondrial glutaminyl-tRNA(Gln) for mitochondrial protein synthesis. This novel strategy that enables a single protein to be localized in both the cytosol and mitochondria provides a new paradigm for regulation of the dynamic subcellular distribution of proteins between membrane-separated compartments.
Frechin
Mathieu
M
UPR 9002, Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, Strasbourg, France.
Senger
Bruno
B
Brayé
Mélanie
M
Kern
Daniel
D
Martin
Robert Pierre
RP
Becker
Hubert Dominique
HD
D003593:Cytoplasm / Q000201:enzymology; D015966:Gene Expression Regulation, Fungal; D005975:Glutamate-tRNA Ligase / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology*; D011485:Protein Binding; D021381:Protein Transport; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*
C102145:ARC1 protein, S cerevisiae; D012346:RNA, Transfer, Amino Acyl; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D018698:Glutamic Acid; D014166:Transferases; D005975:Glutamate-tRNA Ligase