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.

• MeSH
• antikodon genetika   MeSH
• buněčné jádro genetika   ultrastruktura   MeSH
• cytoplazma genetika   ultrastruktura   MeSH
• guanosin genetika   MeSH
• kodon genetika   MeSH
• konformace nukleové kyseliny * MeSH
• mitochondrie genetika   MeSH
• nukleosid Q genetika   MeSH
• posttranskripční úpravy RNA genetika   MeSH
• proteosyntéza genetika   MeSH
• RNA transferová genetika   ultrastruktura   MeSH
• Trypanosoma brucei brucei genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• antikodon MeSH
• guanosin MeSH
• kodon MeSH
• nukleosid Q MeSH
• RNA transferová MeSH

Organisms have evolved different strategies to seclude certain molecules to specific locations of the cell. This is most pronounced in eukaryotes with their extensive intracellular membrane systems. Intracellular compartmentalization is particularly critical in genome containing organelles, which because of their bacterial evolutionary ancestry still maintain protein-synthesis machinery that resembles more their evolutionary origin than the extant eukaryotic cell they once joined as an endosymbiont. Despite this, it is clear that genome-containing organelles such as the mitochondria are not in isolation and many molecules make it across the mitochondrial membranes from the cytoplasm. In this realm the import of tRNAs and the enzymes that modify them prove most consequential. In this review, we discuss two recent examples of how modifications typically found in cytoplasmic tRNAs affect mitochondrial translation in organisms that forcibly import all their tRNAs from the cytoplasm. In our view, the combination of tRNA import and the compartmentalization of modification enzymes must have played a critical role in the evolution of the organelle. © 2018 IUBMB Life, 70(12):1207-1213, 2018.

• Klíčová slova
• 1-methylguanosine, import, mitochondria, trypanosomes, wybutosine,
• MeSH
• cytoplazma genetika   MeSH
• genom mitochondriální genetika   MeSH
• intracelulární membrány MeSH
• mitochondriální membrány metabolismus   MeSH
• mitochondrie genetika   MeSH
• posttranskripční úpravy RNA genetika   MeSH
• proteosyntéza genetika   MeSH
• RNA transferová genetika   MeSH
• symbióza genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• RNA transferová MeSH

Trypanosoma brucei brucei has two distinct developmental stages, the procyclic stage in the insect and the bloodstream stage in the mammalian host. The significance of each developmental stage is punctuated by specific changes in metabolism. In the insect, T. b. brucei is strictly dependent on mitochondrial function and thus respiration to generate the bulk of its ATP, whereas in the mammalian host it relies heavily on glycolysis. These observations have raised questions about the importance of mitochondrial function in the bloodstream stage. Peculiarly, akinetoplastic strains of Trypanosoma brucei evansi that lack mitochondrial DNA do exist in the wild and are developmentally locked in the glycolysis-dependent bloodstream stage. Using RNAi we show that two mitochondrion-imported proteins, mitochondrial RNA polymerase and guide RNA associated protein 1, are still imported into the nucleic acids-lacking organelle of T. b. evansi, making the need for these proteins futile. We also show that, like in the T. b. brucei procyclic stage, the mitochondria of both bloodstream stage of T. b. brucei and T. b. evansi import various tRNAs, including those that undergo thiolation. However, we were unable to detect mitochondrial thiolation in the akinetoplastic organelle. Taken together, these data suggest a lack of connection between nuclear and mitochondrial communication in strains of T. b. evansi that lost mitochondrial genome and that do not required an insect vector for survival.

• MeSH
• adenosintrifosfát metabolismus   MeSH
• buněčné jádro genetika   metabolismus   MeSH
• DNA řízené RNA-polymerasy genetika   metabolismus   MeSH
• geneticky modifikované organismy MeSH
• glykolýza fyziologie   MeSH
• guide RNA, Kinetoplastida metabolismus   MeSH
• kinetoplastová DNA metabolismus   MeSH
• mezibuněčná komunikace MeSH
• mitochondrie genetika   metabolismus   MeSH
• oxidativní fosforylace MeSH
• proteiny genetika   metabolismus   MeSH
• RNA interference MeSH
• RNA transferová genetika   metabolismus   MeSH
• transport proteinů MeSH
• transport RNA MeSH
• Trypanosoma fyziologie   MeSH
• trypanozomiáza parazitologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• adenosintrifosfát MeSH
• DNA řízené RNA-polymerasy MeSH
• guide RNA, Kinetoplastida MeSH
• kinetoplastová DNA MeSH
• proteiny MeSH
• RNA transferová MeSH

Nfs-like proteins have cysteine desulfurase (CysD) activity, which removes sulfur (S) from cysteine, and provides S for iron-sulfur cluster assembly and the thiolation of tRNAs. These proteins also have selenocysteine lyase activity in vitro, and cleave selenocysteine into alanine and elemental selenium (Se). It was shown previously that the Nfs-like protein called Nfs from the parasitic protist Trypanosoma brucei is a genuine CysD. A second Nfs-like protein is encoded in the nuclear genome of T. brucei. We called this protein selenocysteine lyase (SCL) because phylogenetic analysis reveals that it is monophyletic with known eukaryotic selenocysteine lyases. The Nfs protein is located in the mitochondrion, whereas the SCL protein seems to be present in the nucleus and cytoplasm. Unexpectedly, downregulation of either Nfs or SCL protein leads to a dramatic decrease in both CysD and selenocysteine lyase activities concurrently in the mitochondrion and the cytosolic fractions. Because loss of Nfs causes a growth phenotype but loss of SCL does not, we propose that Nfs can fully complement SCL, whereas SCL can only partially replace Nfs under our growth conditions.

• MeSH
• cytosol enzymologie   MeSH
• fylogeneze MeSH
• kompartmentace buňky MeSH
• lyasy štěpící vazby C-S genetika   metabolismus   MeSH
• lyasy antagonisté a inhibitory   genetika   metabolismus   MeSH
• messenger RNA genetika   metabolismus   MeSH
• mitochondrie enzymologie   MeSH
• protozoální geny MeSH
• protozoální proteiny genetika   metabolismus   MeSH
• RNA interference MeSH
• RNA protozoální genetika   metabolismus   MeSH
• Trypanosoma brucei brucei enzymologie   genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• cysteine desulfurase MeSH Prohlížeč
• lyasy štěpící vazby C-S MeSH
• lyasy MeSH
• messenger RNA MeSH
• protozoální proteiny MeSH
• RNA protozoální MeSH
• selenocysteine lyase MeSH Prohlížeč