Abstract
Mitochondrial genomes code for several core components of respiratory chain complexes. Thus, mitochondrial translation is of great importance for the organelle as well as for the whole cell. In yeast, mitochondrial translation initiation factor 3, Aim23p, is not essential for the organellar protein synthesis; however, its absence leads to a significant quantitative imbalance of the mitochondrial translation products. This fact points to a possible specific action of Aim23p on the biosynthesis of some mitochondrial protein species. In this work, we examined such peculiar effects of Aim23p in relation to yeast mitochondrial COX2 mRNA translation. We show that Aim23p is indispensable to this process. According to our data, this is mediated by Aimp23p interaction with the known specific factor of the COX2 mRNA translation, Pet111p. If there is no Aim23p in the yeast cells, an increased amount of Pet111p ensures proper COX2 mRNA translation. Our results demonstrate the additional non-canonical function of initiation factor 3 in yeast mitochondrial translation.
Highlights
Mitochondria originated from the ancient free-living bacterial species, according to the endosymbiotic theory [1]
Upon the deletion of the gene studied, failure to grow in the absence of arginine indicates that a protein product of this gene facilitates the translation of target mRNA acting through its untranslated regions (UTRs)
This study was conducted to describe the mechanisms of mRNA-specific action of Aim23p in yeast mitochondrial translation
Summary
Mitochondria originated from the ancient free-living bacterial species, according to the endosymbiotic theory [1]. Many specific features of this process have been discovered, especially as a result of mitochondrial ribosomes structural studies [2,3]. Many of these features, both structural [4] and mechanistic [5], appear at the initiation step. Aim23p is generally organized in the same way as mammalian mtIF3 according to computer modelling: both proteins consist of core part (which is similar to bacterial IF3) flanked by mitochondria-specific N- and C-terminal extensions [7,8]. E. coli IF3 can partially fulfil the functions of Aim23p in yeast mitochondria [5], which is valuable evidence of the latter being bona fide initiation factor 3
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