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Preferential import of queuosine-modified tRNAs into Trypanosoma brucei mitochondrion is critical for organellar protein synthesis.

ABSTRACT: Transfer RNAs (tRNAs) are key players in protein synthesis. To be fully active, tRNAs undergo extensive post-transcriptional modifications, including queuosine (Q), a hypermodified 7-deaza-guanosine present in the anticodon of several tRNAs in bacteria and eukarya. Here, molecular and biochemical approaches revealed that in the protozoan parasite Trypanosoma brucei, Q-containing tRNAs have a preference for the U-ending codons for asparagine, aspartate, tyrosine and histidine, analogous to what has been described in other systems. However, since a lack of tRNA genes in T. brucei mitochondria makes it essential to import a complete set from the cytoplasm, we surprisingly found that Q-modified tRNAs are preferentially imported over their unmodified counterparts. In turn, their absence from mitochondria has a pronounced effect on organellar translation and affects function. Although Q modification in T. brucei is globally important for codon selection, it is more so for mitochondrial protein synthesis. These results provide a unique example of the combined regulatory effect of codon usage and wobble modifications on protein synthesis; all driven by tRNA intracellular transport dynamics.

SUBMITTER: Kulkarni S

PROVIDER: S-EPMC8373054 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Trypanosomatids are unicellular parasitic protozoa. Many of the species of this genera cause severe diseases in human, such as Leishmaniasis, African trypanosomiasis and Chagas disease. These parasites possess a single reticular mitochondrion with a concatenated structure of mitochondrial DNA known as kinetoplast or kDNA. kDNA encodes few essential mitochondrial proteins but no tRNAs. Therefore, trypanosomatid mitochondrion import a full set of nucleus-encoded tRNAs for mitochondrial translation. Recent advances indicated that mitochondrial protein translocases, particularly the subunits of the ATOM complex, are involved in the import of a tRNA in Trypanosoma brucei. However, the global picture and the role of the translocase components of the mitochondrial inner membrane (TbTims) are not well understood. Here we investigated the relative abundance of 16 different tRNAs in the cytosolic and mitochondrial fractions isolated from the six TbTims knockdown cell lines. We found that knockdown of TbTim17, one of the primary components of the TbTIM complex, reduced the abundance of all of these tRNAs into mitochondria and increased their abundance in the cytosol. Depletion of TbTim62, a TbTim17 associated proteins, also reduced the relative abundance of most of these tRNAs into mitochondria except for tRNAleu, tRNAmet, and tRNAglu. Whereas, knockdown of other TbTims, like TbTim50 and two small TbTims, TbTim10 and TbTim8/13, didn't have any effect on tRNA abundance either in the cytosol or mitochondria. Depletion of any of these TbTims showed minimal effect on the levels of total tRNAs in T. brucei. Absolute quantification of tRNA levels revealed that TbTim17 knockdown reduced the levels of different tRNAs in mitochondria from 3-6% to 0.8-1.4%, which is equivalent to ~70% reduction in average. Whereas, TbTim62 depletion showed somewhat selective effect. Overall, our results suggest that TbTim17 and TbTim62 are essential for tRNA import that further makes a connection between the tRNA and protein import into mitochondria in T. brucei.

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Preferential import of queuosine-modified tRNAs into Trypanosoma brucei mitochondrion is critical for organellar protein synthesis.

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