Abstract
Mitochondria contain their own translation apparatus which enables them to produce the polypeptides encoded in their genome. The mitochondrially-encoded RNA components of the mitochondrial ribosome require various post-transcriptional processing steps. Additional protein factors are required to facilitate the biogenesis of the functional mitoribosome. We have characterized a mitochondrially-localized protein, YbeY, which interacts with the assembling mitoribosome through the small subunit. Loss of YbeY leads to a severe reduction in mitochondrial translation and a loss of cell viability, associated with less accurate mitochondrial tRNASer(AGY) processing from the primary transcript and a defect in the maturation of the mitoribosomal small subunit. Our results suggest that YbeY performs a dual, likely independent, function in mitochondria being involved in precursor RNA processing and mitoribosome biogenesis. Issue Section: Nucleic Acid Enzymes.
Highlights
Oxidative phosphorylation (OxPhos) is one of the major functions of mitochondria
YbeY has been shown to be an active RNase in various bacterial species [34,36,47] and in plant chloroplasts [48].In E. coli, similar to the mitochondria, the ribosomal RNAs are initially transcribed within a primary transcript and are later released through multiple hierarchical cleavage events
The proportion of misprocessed to correctly processed RNAs would be higher than that present in living cells, which may have influenced the proportion of misprocessed mt-tRNAs observed for mt-tRNAIle and mt-tRNALeu(UUR)
Summary
Oxidative phosphorylation (OxPhos) is one of the major functions of mitochondria. A majority of the components of the OxPhos complexes are encoded in the cell nucleus and imported into mitochondria upon translation in the cytoplasm. Thirteen structural polypeptides of the OxPhos complexes are translated within mitochondria These polypeptides are encoded in the human mitochondrial genome (mtDNA) along with the 22 tRNAs and two rRNAs that make up the RNA components of the intraorganellar translation apparatus. In the majority of cases, mRNAs and rRNAs in the precursors are flanked by tRNA molecules [1,2] The excision of these mt-tRNAs is performed by endonucleolytic enzymes RNase P at the 5 end, and RNase Z (ELAC2) at the 3 end [3,4]. This releases the mt-mRNAs and mt-rRNAs, with the latter undergoing further maturation and assembly into the mitochondrial ribosome
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