Mitochondrial Aminoacyl-tRNA Synthetase and Disease: The Yeast Contribution for Functional Analysis of Novel Variants

Abstract

In most eukaryotes, mitochondrial protein synthesis is essential for oxidative phosphorylation (OXPHOS) as some subunits of the respiratory chain complexes are encoded by the mitochondrial DNA (mtDNA). Mutations affecting the mitochondrial translation apparatus have been identified as a major cause of mitochondrial diseases. These mutations include either heteroplasmic mtDNA mutations in genes encoding for the mitochondrial rRNA (mtrRNA) and tRNAs (mttRNAs) or mutations in nuclear genes encoding ribosomal proteins, initiation, elongation and termination factors, tRNA-modifying enzymes, and aminoacyl-tRNA synthetases (mtARSs). Aminoacyl-tRNA synthetases (ARSs) catalyze the attachment of specific amino acids to their cognate tRNAs. Differently from most mttRNAs, which are encoded by mitochondrial genome, mtARSs are encoded by nuclear genes and then imported into the mitochondria after translation in the cytosol. Due to the extensive use of next-generation sequencing (NGS), an increasing number of mtARSs variants associated with large clinical heterogeneity have been identified in recent years. Being most of these variants private or sporadic, it is crucial to assess their causative role in the disease by functional analysis in model systems. This review will focus on the contributions of the yeast Saccharomyces cerevisiae in the functional validation of mutations found in mtARSs genes associated with human disorders.

Disruption of Hars2 in Cochlear Hair Cells Causes Progressive Mitochondrial Dysfunction and Hearing Loss in Mice

“…Deficiency of ARSs, especially the mitochondrial ARSs (mtARSs) often affect tissues with high metabolic demands such as the brain, muscle, and inner ear ( Fine et al, 2019 ). Clinical features associated with mutations in mtARS-encoding genes typically include encephalopathy, leukodystrophy, cardiomyopathy, ovarian dysgenesis, and deafness ( Figuccia et al, 2021 ).…”

“…Characterized by enzyme kinetic assays, yeast complementation assays and studies of patient-derived cell cultures, most of the mtARS mutations have been shown to disrupt its aminoacylation activity ( Oprescu et al, 2017 ; Figuccia et al, 2021 ). Previous study on a Dars2 conditional knockout mouse showed that DARS2 depletion in heart and skeletal muscle causes severe dysfunction of mitochondrial protein synthesis in both tissues, which activates various stress responses predominantly in the cardiomyocytes ( Dogan et al, 2014 ).…”

Saccharomyces cerevisiae as a Tool for Studying Mutations in Nuclear Genes Involved in Diseases Caused by Mitochondrial DNA Instability

“…If the gene under analysis is fundamental for the maintenance of the mtDNA, its deletion in a haploid strain leads to mtDNA loss, thus resulting in a rho 0 strain, in which reintroduction of the wild-type gene does not recover the presence of mtDNA. To overcome this problem, several techniques can be used to maintain the mtDNA before the introduction of the mutant allele, as reviewed in [ 85 , 96 ]. The most used technique is the plasmid shuffling strategy, wherein one-step gene disruption is performed in an ura3 strain previously transformed with the yeast wild-type gene cloned in a centromeric plasmid harboring URA3 as a selection marker.…”

A Yeast-Based Repurposing Approach for the Treatment of Mitochondrial DNA Depletion Syndromes Led to the Identification of Molecules Able to Modulate the dNTP Pool

“…Yeast has proved to be not only an excellent model for the study of the mechanisms underlying mitochondrial pathology [19][20][21][22][23] but also for the discovery of new therapies. Highthroughput yeast-based assays have been successfully used by different groups [24,25] to identify drugs active against several human mitochondrial disorders [20,[26][27][28][29][30][31].…”