Figure 3 .

Cytoplasmic synthesis of some mitochondrial proteins is localized to the organelles, while the synthesis of others is not. The figure depicts three examples: (1) The ATP2 mRNA is highly localized to mitochondria-bound polysomes (Garcia et al. 2007b), although factors required for this localization are unknown. (2) The BCS1 mRNA is also selectively found in mitochondria-bound polysomes, and its localization is partially dependent upon the mitochondrially localized RNA-binding protein Puf3 and the Puf3-binding sites in its 3′-UTR (Saint-Georges et al. 2008). (3) The COX4 mRNA is exclusively found on free polysomes, unassociated with mitochondria (Garcia et al. 2007b). The Atp2, Bcs1, and Cox4 proteins all traverse the outer membrane via the TOM complex pore.