Mitochondrial Translation

Abstract

The translation elongation factor EF-Tu is a GTPase that delivers amino-acylated tRNAs to the ribosome during the elongation step of translation. EF-Tu/GDP is recycled by the guanine nucleotide exchange factor EF-Ts. Whereas EF-Ts is lacking in S. cerevisiae, both translation factors are found in S. pombe and H. sapiens mitochondria, consistent with the known similarity between fission yeast and human cell mitochondrial physiology. We constructed yeast mutants lacking these elongation factors. We show that mitochondrial translation is vital for S. pombe, as it is for human cells. In a genetic background allowing the loss of mitochondrial functions, a block in mitochondrial translation in S. pombe leads to a major depletion of mtDNA. The relationships between EF-Ts and EF-Tu from both yeasts and humans were investigated through functional complementation and coexpression experiments and by a search for suppressors of the absence of the S. pombe EF-Ts. We find that S. cerevisiae EF-Tu is functionally equivalent to the S. pombe EF-Tu/EF-Ts couple. Point mutations in the S. pombe EF-Tu can render it independent of its exchange factor, thereby mimicking the situation in S. cerevisiae.

Bot1p Is Required for Mitochondrial Translation, Respiratory Function, and Normal Cell Morphology in the Fission Yeast Schizosaccharomyces pombe

“…Indeed, pharmacological inhibition of the mitochondrial respiratory chain with the cytochrome c oxidase inhibitor KCN did not induce a similar alteration of the cell shape and instead produced uniformly small cells (F. Verde, unpublished data). Respiratory mutants were not previously reported as presenting a cell morphology alteration (7,13). In mutants of msp1, which encode a dynamin-related protein involved in mtDNA maintenance, an alteration of cell morphology is clearly not observed (18).…”

“…Nuclear genes also code for proteins that function in biogenesis of the translational machinery rather than in translation itself (2,9,37). In S. pombe mitochondrial protein translation is regulated by the guanine nucleotide exchange factor EF-Ts, conserved in higher eukaryotes, which controls the translation elongation factor EF-Tu (7). S. pombe is a petite-negative yeast and, similarly to mammalian cells, cannot survive the loss of mtDNA and mitochondrial protein synthesis (36).…”

Translation Initiation inSaccharomyces cerevisiaeMitochondria: Functional Interactions Among Mitochondrial Ribosomal Protein Rsm28p, Initiation Factor 2, Methionyl-tRNA-Formyltransferase and Novel Protein Rmd9p

“…The major mitochondrial translation products are indicated. (B) Lowtemperature cytochrome spectra were recorded after addition of dithionite to whole cells grown on complete galactose medium at 28°, as described (Chiron et al 2005). Absorption maxima for cytochromes a 1 a 3 , b, c 1 , and c are 602, 558, 552, and 546 nm, respectively.…”

Intricacies and surprises of nuclear–mitochondrial co-evolution

“…However, in S. cerevisiae and its close relatives, EF-Tu has become independent of its exchange factor and the gene for EF-Ts is lost from the genomes. Yet, unlike the situation with EF-Tu1 and -Tu2 in Caenorhabditis elegans, the changes in protein sequence required for such a gain of function are subtle, and no additional domain was recruited [9].…”