Arava 2015 Abstract MiP2015
|Localized translation near mitochondria: novel factors revive old model.
Most mitochondrial proteins are encoded in the nucleus, and need to be imported into this organelle. The predominating, textbooks model for targeting to mitochondria asserts that proteins are translated throughout the cytoplasm and transported after their complete synthesis (i.e. post-translationally). However, recent mRNA localization studies revealed that many mRNAs that encode mitochondrial proteins are localized to the vicinity of mitochondria in a manner that involves translation. These results revived neglected model in which translation of mitochondrial mRNAs is localized to the mitochondria vicinity and import occurs cotranslationally. We are exploring the proteins that coordinate such localized translation. We previously established the involvement of the mitochondrial protein receptor Tom20 and the Hsp70-member Ssa1 in association of translating ribosomes with the mitochondria [1,2]. Herein we further elaborate on a role in localized translation for an additional factor, the conserved ribosome-associated Nascent-chain Associated Complex (NAC). NAC was shown to contribute to ribosomes’ association with mitochondria, yet its mitochondrial receptor was unknown. We performed several genome-wide protein complementation assays and detected an outer membrane protein (OM14) of an unknown function as associated with NAC. Mitochondria deleted of OM14 had significantly lower amounts of associated NAC, and ribosomes deleted of NAC had reduced levels of associated OM14. Importantly, mitochondrial import assays revealed a significant decrease in import efficiency into OM14 deleted mitochondria and OM14-dependent import necessitated NAC.
Our results identify OM14 as a mitochondrial receptor for ribosomes-associated NAC and reveal its importance for import. These studies re-establish localized translation as an additional mode for protein targeting to mitochondria.
Labels: MiParea: mt-Membrane, mtDNA;mt-genetics, nDNA;cell genetics
Event: B1, Oral MiP2015
1-Dept Biology, Technion – Israel Inst Technol; 2-Dept Mol Genetics Weizmann Inst Sc, Israel. - [email protected]
References and acknowledgements
- Eliyahu E, Pnueli L, Melamed D, Scherrer T, Gerber AP, Pines O, Rapaport D, Arava Y (2010) Tom20 mediates localization of mRNAs to mitochondria in a translation-dependent manner. Mol Cell Biol 30:284-94.
- Eliyahu E, Lesnik C, Arava Y (2012) The protein chaperone Ssa1 affects mRNA localization to the mitochondria. FEBS Lett 586:64-9.
- Lesnik C, Cohen Y, Atir-Lande A, Schuldiner M, Arava Y (2014) OM14 is a mitochondrial receptor for cytosolic ribosomes that supports co-translational import into mitochondria. Nature Commun 5:5711.
- Lesnik C, Golani-Armon A, Arava Y (2015) Localized translation near the mitochondrial outer membrane: An update. RNA Biology in press.