Exploration de nouvelles propriétés de macromolécules clés de la traduction mitochondriale humaine – MITOMOT

Mitochondria are the powerhouse of eukaryotic cells. They have there own genome which codes for 13 proteins, all involved in the process of energy synthesis, and accordingly possess also a dedicated and specific translation machinery. Transfer RNAs and aminoacyl-tRNA synthetases, key macromolecules of this machinery, remain poorly characterized, despite their more and more important involvement in a large variety of neurodegenerative disorders, often severe and even fatal. Here, we will further characterize structural and functional properties of several human mitochondrial aminoacylation systems by in vitro approaches, in vivo, decipher the atypical mechanism of glutaminylation, explore the sub-mitochondrial organization of aminoacyl-tRNA synthetases and search for partner proteins. The incidence of the acquired new knowledge will be evaluated as well in the field of evolution of aminoacylation systems as in that of the molecular understanding of mitochondrial translation disorders. The endosymbiotic origin of mitochondria suggests strong similarities of aminoacylation systems with bacterial ones. This is however only apparent. Our work will allow to define the molecular deviations undergone by mitochondrial systems and to reveal the corresponding specific properties. Determination of protein partners of synthetases will allow an immediate evaluation of the impact of these partners on properties of mutated tRNAs and synthetases responsible of mitochondrial disorders. This may alleviate an important barrier in the understanding of these pathologies for which the involvement of "modifier" proteins has often been hypothesized. Finally, we open an unprecedented research field, with the structural and functional characterization (in vitro and in vivo) of a first (of a growing series) splice variant detected for a mitochondrial aminoacyl-tRNA synthetase. Such a variant, that co-exists in many human tissues with the full-length protein, opens all possibilities of interrelations between the translation machinery and other processes inside (but likely also outside) mitochondria. The consequences of the activity(ies) of splice-variants on understanding of mitochondrial pathologies are potentially very important. Biochemistry, structural biology, bioinformatics and cellular biology approaches will be combined by a network of 3 research teams of complementary skills, international experts in the field of translation, 3 teams who had already fruitful collaborations together.