ABSTRACT
This review focuses on the posttranscriptional processes which govern mitochondrial biogenesis, with a special emphasis on the asymmetric localization-translation of nuclear-encoded mRNAs as an important regulatory step of the protein import process. We review how spatio-temporal mRNA regulons help to elicit timely, versatile, and coordinated intracellular processes to assemble mitochondrial structures. Our current knowledge on the mitochondrial import of respiratory chain assembly factors and the role of the ribonucleic acid (RNA) binding protein Puf3 are presented. A connection with the target of rapamycine signalling pathway may explain how respiratory chain assembly senses environmental conditions via the protein import machinery.
Subject(s)
Mitochondria/metabolism , Mitochondrial Proteins/metabolism , RNA Processing, Post-Transcriptional , RNA, Messenger/metabolism , Animals , Humans , Mitochondrial Proteins/genetics , Models, Biological , Protein Biosynthesis , Protein Transport , RNA, Messenger/genetics , RNA-Binding Proteins/metabolismABSTRACT
Although a considerable amount of data have been gathered on mitochondrial translocases, which control the import of a large number of nuclear-encoded proteins, the preceding steps taking place in the cytosol are poorly characterized. The localization of messenger RNAs (mRNAs) on the surface of mitochondria was recently shown to involve specific classes of protein and could be an important regulatory step. By using an improved statistical fluorescent in situ hybridization technique, we analysed the elements of the ATP2 open reading frame that control its mRNA asymmetric localization. The amino-terminal mitochondrial targeting peptide (MTS) and translation of two elements in the coding sequence, R1 and R2, were required for anchoring of ATP2 mRNA to mitochondria. Unexpectedly, any MTS can replace ATP2 MTS, whereas R1 and R2 are specifically required to maintain perimitochondrial mRNA localization. These data connect the well-known MTS-translocase interaction step with a site-specific translation step and offer a mechanistic description for a co-translational import process.
