Fig. 7. Schematic depiction of the proposed subcellular distribution mechanism for tRNAs that read NAG codons in L.tarentolae. Precursor tRNAs are transcribed from genes in the nucleus and are exported into the cytosol with the mcm⁵U modification at the wobble position. Cytosolic tRNA is matured by 2-thiolation of the modification intermediate and localized in the cytosol. A portion of the modification intermediate is imported into the mitochondrion, where 2′-O-methylation of mcm⁵U follows.