Yeast as a model of human mitochondrial tRNA base substitutions: investigation of the molecular basis of respiratory defects.
We investigate the relationships between acylation defects and structure alterations due to base substitutions in yeast mitochondrial (mt) tRNA(UUR)(Leu). The studied substitutions are equivalent to the A3243G and T3250C human pathogenetic tRNA mutations. Our data show that both mutations can produce tRNA(UUR)(Leu) acylation defects, although to a different extent. For mutant A14G (equivalent to MELAS A3243G base substitution), the presence of the tRNA and its defective aminoacylation could be observed only in the nuclear context of W303, a strain where the protein synthesis defects caused by tRNA base substitutions are far less severe than in previously studied strains. For mutant T20C (equivalent to the MM/CPEO human T3250C mutation), the acylation defect was less severe, and a thermosensitive acylation could be detected also in the MCC123 strain. The correlation between the severity of the in vivo phenotypes of yeast tRNA mutants and those obtained in in vitro studies of human tRNA mutants supports the view that yeast is a suitable model to study the cellular and molecular effects of tRNA mutations involved in human pathologies. Furthermore, the yeast model offers the possibility of modulating the severity of yeast respiratory phenotypes by studying the tRNA mutants in different nuclear contexts. The nucleotides at positions 14 and 20 are both highly conserved in yeast and human mt tRNAs; however, the different effect of their mutations can be explained by structure analyses and quantum mechanics calculations that can shed light on the molecular mechanisms responsible for the experimentally determined defects of the mutants.
Department of Cell and Developmental Biology, Pasteur Institute-Fondazione Cenci Bolognetti, University Sapienza, 00185 Rome, Italy.
Arianna
A
Montanari
Céline
C
Besagni
Cristina
C
De Luca
Veronica
V
Morea
Romina
R
Oliva
Anna
A
Tramontano
Monique
M
Bolotin-Fukuhara
Laura
L
Frontali
Silvia
S
Francisci
D000107:Acetylation; D001483:Base Sequence; D019069:Cell Respiration / Q000235:genetics; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D009690:Nucleic Acid Conformation; D010641:Phenotype; D012313:RNA / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000077278:RNA, Mitochondrial; D012356:RNA, Transfer, Leu / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D012331:RNA, Fungal; D000077278:RNA, Mitochondrial; D012356:RNA, Transfer, Leu; D012313:RNA