The import of yeast tRNALys (tRK1) into human mitochondria in the presence of cytosolic extract suggests that human cell possesses machinery for tRK1 import. Here, we show that precursor of mitochondrial lysyl-tRNA synthetase (preKARS2) interact with tRK1 and its derivatives containing tRK1 import determinants, and facilitates their import into isolated mitochondria and in vivo, when preKARS2 was overexpressed or downregulated. tRK1 import efficiency increased upon addition of glycolytic enzyme enolase, previously found as an actor of RNA import in yeast. We found that tRK1 and its derivatives translocate into mitochondrial matrix in polynucleotide phosphorylase (PNPase) dependent manner. Furthermore, a point mutation preventing trimerization of PNPase affect import of 5S rRNA and MRP RNA into mitochondria and subsequently mitochondrial translation. Overexpression of the wild-type PNPase induced an increase of 5S rRNA import into mitochondria and rescued translation.

L'importation de ARNtLys CUU (tRK1) de levure dans les mitochondries humaines indique que la cellule humaine possède la machinerie pour importation d'ARNt. Dans la présente étude, nous montrons que le précurseur de la lysyl-ARNt synthétase mitochondriale peut interagir avec tRK1 et ses dérivés contenant les déterminants d'import mitochondrial, et facilite leur internalisation par les mitochondries humaines. L'efficacité de l'importation augmentait à l'addition de l'énolase, d'enzyme glycolytique fonctionnant comme ARN chaperon. La translocation de tRK1 et de ses dérivés dans la matrice mitochondriale dépend également d'une autre protéine, la polynucléotide phosphorylase (PNPase). Mutation ponctuelle pathogénique qui prévient la trimérisation de PNPase diminue l'importation des ARNr 5S et ARN MRP dans les mitochondries ceci affectant la traduction mitochondriale. La surexpression de PNPase induit une augmentation des ARN importé et complémente le déficit de traduction mitochondriale. / The import of yeast tRNALys (tRK1) into human mitochondria in the presence of cytosolic extract suggests that human cell possesses machinery for tRK1 import. Here, we show that precursor of mitochondrial lysyl-tRNA synthetase (preKARS2) interact with tRK1 and its derivatives containing tRK1 import determinants, and facilitates their import into isolated mitochondria and in vivo, when preKARS2 was overexpressed or downregulated. tRK1 import efficiency increased upon addition of glycolytic enzyme enolase, previously found as an actor of RNA import in yeast. We found that tRK1 and its derivatives translocate into mitochondrial matrix in polynucleotide phosphorylase (PNPase) dependent manner. Furthermore, a point mutation preventing trimerization of PNPase affect import of 5S rRNA and MRP RNA into mitochondria and subsequently mitochondrial translation. Overexpression of the wild-type PNPase induced an increase of 5S rRNA import into mitochondria and rescued translation.