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Factors beyond Enolase 2 and Mitochondrial Lysyl-tRNA Synthetase Precursor Are Required for tRNA Import into Yeast Mitochondria

M. V. Baleva1,2, M. Meyer3, N. Entelis1, I. Tarassov1, P. Kamenski2,4, and B. Masquida1*

1GMGM, CNRS – University of Strasbourg, UMR 7156, 67081 Strasbourg, France; E-mail: b.masquida@unistra.fr

2Lomonosov Moscow State University, Faculty of Biology, 119991 Moscow, Russia; E-mail: piotr.kamenski@gmail.com

3IGBMC, CNRS – University of Strasbourg, UMR 7104, 67404 Illkirch, France

4Immanuil Kant Baltic Federal University, Institute of Living Systems, 236038 Kaliningrad, Russia

* To whom correspondence should be addressed.

Received April 7, 2017; Revision received June 16, 2017
In yeast, the import of tRNALys with CUU anticodon (tRK1) relies on a complex mechanism where interaction with enolase 2 (Eno2p) dictates a deep conformational change of the tRNA. This event is believed to mask the tRNA from the cytosolic translational machinery to re-direct it towards the mitochondria. Once near the mitochondrial outer membrane, the precursor of the mitochondrial lysyl-tRNA synthetase (preMsk1p) takes over enolase to carry the tRNA within the mitochondrial matrix, where it is supposed to participate in translation following correct refolding. Biochemical data presented in this report focus on the role of enolase. They show that despite the inability of Eno2p alone to form a complex with tRK1, mitochondrial import can be recapitulated in vitro using fractions of yeast extracts sharing either recombinant or endogenous yeast Eno2p as one of the main components. Taken together, our data suggest the existence of a protein complex containing Eno2p that is involved in RNA mitochondrial import.
KEY WORDS: RNA mitochondrial import, RNA chaperone, tRNA–enolase interaction, enolase, moonlighting protein

DOI: 10.1134/S0006297917110104