title: Partial suppression of the respiratory defect of qrs1/her2 glutamyl-tRNA amidotransferase mutants by overexpression of the mitochondrial pentatricopeptide Msc6p.
abstract: Recently, a large body of evidences indicates the existence in the mitochondrial matrix of foci that contain different proteins involved in mitochondrial RNA metabolism. Some of these proteins have a pentatricopeptide repeat motif that constitutes their RNA-binding structures. Here we report that MSC6, a mitochondrial pentatricopeptide protein of unknown function, is a multi copy suppressor of mutations in QRS1/HER2 a component of the trimeric complex that catalyzes the transamidation of glutamyl-tRNAQ to glutaminyl-tRNAQ. This is an essential step in mitochondrial translation because of the lack of a specific mitochondrial aminoacyl glutaminyl-tRNA synthetase. MSC6 over-expression did not abolish translation of an aberrant variant form of Cox2p detected in QRS1/HER2 mutants, arguing against a suppression mechanism that bypasses Qrs1p function. A slight decrement of the mitochondrial translation capacity as well as diminished growth on respiratory carbon sources media for respiratory activity was observed in the msc6 null mutant. Additionally, the msc6 null mutant did not display any impairment in RNA transcription, processing or turnover. We concluded that Msc6p is a mitochondrial matrix protein and further studies are required to indicate the specific function of Msc6p in mitochondrial translation.
authors.affiliation: Departamento de Microbiologia-Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Professor Lineu Prestes, 1374, São Paulo, 05508-900, Brazil.
authors.forename: Bruno S
authors.initials: BS
authors.lastname: Moda
authors.affiliation: Escola de Artes, Ciências e Humanidades-USP, Av. Arlindo Béttio, 1000 Ermelino Matarazzo, São Paulo, 03828-000, Brazil.
authors.forename: José Ribamar
authors.initials: JR
authors.lastname: Ferreira-Júnior
authors.affiliation: Departamento de Microbiologia-Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Professor Lineu Prestes, 1374, São Paulo, 05508-900, Brazil. mariohb@usp.br.
authors.forename: Mario H
authors.initials: MH
authors.lastname: Barros
mesh_terms: D000483:Alleles; D000604:Amino Acyl-tRNA Synthetases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins; D015870:Gene Expression; D015966:Gene Expression Regulation, Fungal; D005838:Genotype; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic
chemical_list: D045222:Electron Transport Chain Complex Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; D000604:Amino Acyl-tRNA Synthetases; C020659:glutaminyl-tRNA synthetase
keywords: Keywords; Mitochondria; Mitochondrial translation; Respiratory chain; Saccharomyces cerevisiae