In vivo studies of mitochondrial tRNA mutations in S. cerevisiae

Yeast mitochondria were taken as a versatile tool to investigate the pathogenecity and the mechanism of mitochondrial dysfunction due to point mutations in tRNA genes correlated in humans with neurodegenerative diseases. The biolistic mutants LysG38A, equivalent to the G8328A mutation correlated in humans with mitochondrial encephalomyopathy, and IleT33A, equivalent to the human position 4290 of tRNAIle, were constructed and characterized. The analysis of two other yeast mutants in the anticodon region revealed that mutations involving the same position even on different tRNA genes may cause similar defects. Moreover, the efficiency of the mt-tRNA-synthetases as well as the EF-Tu to suppress the defective phenotype was tested. Finally, the importance of the nuclear background in which the mitochondrial mutation is expressed was investigated by changing the nuclear context of each mutant and quantifying the expression level of the TUF1 gene in different wild-type and/or rho° strains. The results here described may allow the possibility to investigate the pathogenic potential of some tRNA human mutations and to search for nuclear genes that can either suppress or modify the defective phenotype