Genome‐wide analysis of mRNAs targeted to yeast mitochondria

Abstract

It is agreed that nuclear-encoded mitochondrial proteins are post-translationally targeted to mitochondria, even if, in some cases, a co-translational phase can assist the import of precursor proteins. We used yeast DNA microarrays to analyse the mRNA populations associated with free and mitochondrion-bound polysomes. As expected, many mRNAs, known to encode mitochondrial proteins, are localized to free cytoplasmic polysomes, but many are localized to mitochondrion-bound polysomes. Furthermore, the 3′-UTR of six randomly chosen mitochondrion-bound mRNAs contains sufficient information to target, in vivo, non-translatable RNA to the vicinity of mitochondria. Interestingly, genes producing mRNAs that are targeted to mitochondria are mainly of ancient bacterial origin, whereas those producing mRNAs that are translated in the cytoplasm are mainly of eukaryotic origin. These observations, which support the recent hypotheses concerning the dual origin of the mitochondrial proteome, provide new insights into the biogenesis of mitochondria.

A glycolytic enzyme, enolase, is recruited as a cofactor of tRNA targeting toward mitochondria in Saccharomyces cerevisiae

“…As expected, the Atp1 p.m.RNA was found to be associated with mitochondria to an extent of up to 45%. This value is in agreement with the previously reported one (Marc et al 2002) and reflects the fact that a portion of mitochondria-bound polysomes were released during mitochondria isolation. Up to 35% of the preMsk1 p.m.RNA was found to be mitochondriaassociated, which is comparable to the Atp1 p.m.RNA.…”

“…It has been shown that the mRNAs of numerous mitochondrially addressed proteins are translated in the vicinity of the mitochondria to facilitate their compartmentalization (Marc et al 2002). This may also be the case for preMsk1p, which is essential for mitochondrial translocation of tRK1.…”

“…Real-time RT-PCR was next used to measure the amounts of mRNAs coding for Eno1/2p, preMsk1p, and two control proteins, Krs1p (cytosolic lysyl-tRNA synthetase) and Atp1p (previously reported to be perimitochondrially translated ( Fig. 6; Marc et al 2002). The percentage of mitochondria-associated mRNAs, compared with either cytosolic polysomes or total cell mRNA, was calculated.…”

Plant organellar protein targeting: a traffic plan still under construction

“…In fact, mammalian mitochondria appear to possess specific receptors for binding ribosomes [49]. Genes of ancient bacterial origin comprise a significant proportion of these mitochondrion-associated mRNAs, while genes of eukaryotic origin that encode organellar proteins generally contain presequences and seem to be primarily translated on cytoplasmic polysomes [50]. The ribosomal recruitment of mRNAs requires specific features of the 3′ untranslated region of the transcripts [51].…”

Interactions amongCOX1,COX2, andCOX3mRNA-specific Translational Activator Proteins on the Inner Surface of the Mitochondrial Inner Membrane ofSaccharomyces cerevisiae

“…In general, these strategies seem to reinforce targeting information present within the protein products themselves. In S. cerevisiae, for example, nuclearly coded mRNAs for several mitochondrial proteins bearing mitochondrial import signals seem to be translated preferentially by cytoplasmic ribosomes tightly associated with the organelles, facilitating their localization (Marc et al, 2002). This targeting is dependent upon signals in the mRNA 3Ј-untranslated regions.…”