Аннотация:Mitochondria are known to contain their own genome and to be able to transcribe and to translate their genetic material. However, the vast majority of the macromolecules that functions in the mitochondria are imported there from the cytoplasm. These include, mainly, proteins and RNAs. Protein import into mitochondria is a well-understood process and occurs by more or less universal mechanisms in all eukaryotic cells. In contrast, little is known about RNA import into mitochondria. The most commonly imported RNA species are transfer RNAs. tRNA import is observed in protozoan, fungi, plant and marsupials. Besides tRNAs, 5S rRNA and RNA components of RNases P and MRP are also imported in mammalian cells. The pools of imported tRNAs are very different for different organisms: from three in the case of Saccharomyces cerevisiae or Marchantia polyporpha to the totality of mitochondrial tRNA species of Trypanosomatidae. The mechanisms of tRNA import into mitochondria are poorly understood. It is clear, however, that they are not universal among all the species.
The group of Robert Martin and Ivan Tarassov at the University of Strasbourg, France (where the author worked for many years) in collaboration with the team of Igor Krasheninnikov at Moscow University, Russia (where the author works now) study tRNA import into yeast mitochondria for almost two decades. Our experiments are focused on lysine tRNA import (two glutamine tRNA species are also imported but the mechanism of this process is clearly different from that in case of lysine tRNA). For the moment, we already know a lot of things about how tRNA is imported into yeast mitochondria. We have determined the nucleotides of the imported tRNA that are necessary for its import. We have revealed the structural and energetic requirements of the tRNA import process. We have described the function of the imported tRNA in the matrix of yeast mitochondria. Finally, we know how the tRNA targeting to the mitochondria occurs. The main role in the latter is reserved by the soluble cytosolic proteins. We have identified three of them as “protein factors” of tRNA import process. In this work, we describe the role of each of these protein factors in detail.