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Isolation of mRNAs Associated with Yeast Mitochondria to Study Mechanisms of Localized Translation
Published on: March 15, 2014
Genome-wide analysis of mRNAs targeted to yeast mitochondria
Philippe Marc1, Antoine Margeot, Frederic Devaux
1Laboratoire de Génétique Moléculaire (UMR CNRS 8541), Ecole Normale Supérieure, 46 rue d'Ulm, F-75005 Paris, France.
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.
Insights
Researchers found that messenger RNAs (mRNAs) encoding mitochondrial proteins can be localized to mitochondrion-bound polysomes, suggesting a direct role in mitochondrial biogenesis. This localization is linked to the ancient bacterial origins of these genes.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Nuclear-encoded mitochondrial proteins are typically targeted post-translationally, though co-translational import can assist.
- The precise mechanisms and localization of mRNA involved in mitochondrial protein synthesis are not fully understood.
Purpose of the Study:
- To investigate the localization of mRNAs encoding mitochondrial proteins.
- To determine if specific mRNA populations associate with mitochondrion-bound polysomes.
- To explore the functional significance of mRNA localization in mitochondrial biogenesis.
Main Methods:
- Yeast DNA microarrays were employed to analyze mRNA populations.
- mRNA localization was studied in free and mitochondrion-bound polysomes.
- In vivo assays were performed using non-translatable RNA to assess targeting information within 3'-UTRs.
Main Results:
- A significant population of mRNAs encoding mitochondrial proteins were found associated with mitochondrion-bound polysomes.
- The 3'-untranslated region (3'-UTR) of mitochondrion-bound mRNAs contained sequences sufficient for targeting RNA to the vicinity of mitochondria.
- Genes with mitochondrion-targeted mRNAs are predominantly of ancient bacterial origin, unlike cytoplasmically translated genes of eukaryotic origin.
Conclusions:
- These findings support hypotheses of a dual origin for the mitochondrial proteome.
- mRNA localization to mitochondrion-bound polysomes plays a role in mitochondrial biogenesis.
- The differential origin of targeted genes provides new insights into mitochondrial evolution and protein import.
