Structural and functional role of bases 32 and 33 in the anticodon loop of yeast mitochondrial tRNA^Ile

Abstract

Previous work has demonstrated the usefulness of the yeast model to investigate the molecular mechanisms underlying defects due to base substitutions in mitochondrial tRNA genes, and to identify suppressing molecules endowed with potential clinical relevance. The present paper extends these investigations to two human equivalent yeast mutations located at positions 32 and 33 in the anticodon loop of tRNA Ile . Notwithstanding the proximity of the two T>C base substitutions, the effects of these mutations have been found to be quite different in yeast, as they are in human. The T32C substitution has a very severe effect in yeast, consisting in a complete inhibition of growth on nonfermentable substrates. Conversely, respiratory defects caused by the T33C mutation could only be observed in a defined genetic context. Analyses of available sequences and selected tRNA threedimensional structures were performed to provide explanations for the different behavior of these adjacent mutations. Examination of the effects of previously identified suppressors demonstrated that overexpression of the TUF1 gene did not rescue the defective phenotypes determined by either mutation, possibly as a consequence of the lack of interactions between EF-Tu and the tRNA anticodon arm in known structures. On the contrary, both the cognate IleRS and the noncognate LeuRS and ValRS are endowed with suppressing activities toward both mutations. This allows us to extend to the tRNA Ile mutants the crosssuppression activity of aminoacyl-tRNA synthetases previously demonstrated for tRNA Leu and tRNA Val mutants.

Positive and purifying selection in mitochondrial genomes of a bird with mitonuclear discordance

“…Regulation in replication, transcription and translation can play a major role in rapid adaptive evolution (Wittenhagen & Kelley 2003;Burton & Barreto 2012;Bailey et al 2014). Transfer RNA mutations in anticodon stem/loops might disrupt secondary structure and change function (Wittenhagen & Kelley 2003;Montanari et al 2011). Our results show such mutations in E. australis.…”

“…Transfer RNA mutations in anticodon stem/loops might disrupt secondary structure and change function (Wittenhagen & Kelley ; Montanari et al . ). Our results show such mutations in E. australis .…”

Gcn5 histone acetyltransferase is present in the mitoplasts

“…Laboratory yeast strains are genetically and physiologically heterogeneous, with differences in growth behaviours (Montanari et al, 2008; 2011; De Luca et al, 2006; 2009). W303-1A has been selected in French laboratories due to its good sporulation and formation of complete tetrads, which is useful for genetic analysis in which high respiration is necessary.…”

Strain‐specific nuclear genetic background differentially affects mitochondria‐related phenotypes in Saccharomyces cerevisiae

“…In the course of our studies on mt tRNA mutants (De Luca et al 2009 ; Montanari et al 2010 , 2011 ), we have previously observed important phenotypic differences among S. cerevisiae strains, indicating that a better definition of the involved genetic variability will be essential to define the relationship between the mt efficiency and the characteristics of different nuclear backgrounds.…”