Abstract
Human mitochondrial (mt) tRNA(Lys) has a taurine-containing modified uridine, 5-taurinomethyl-2-thiouridine (taum5s2U), at its anticodon wobble position. We previously found that the mt tRNA(Lys), carrying the A8344G mutation from cells of patients with myoclonus epilepsy associated with ragged-red fibers (MERRF), lacks the taum5s2U modification. Here we describe the identification and characterization of a tRNA-modifying enzyme MTU1 (mitochondrial tRNA-specific 2-thiouridylase 1) that is responsible for the 2-thiolation of the wobble position in human and yeast mt tRNAs. Disruption of the yeast MTU1 gene eliminated the 2-thio modification of mt tRNAs and impaired mitochondrial protein synthesis, which led to reduced respiratory activity. Furthermore, when MTO1 or MSS1, which are responsible for the C5 substituent of the modified uridine, was disrupted along with MTU1, a much more severe reduction in mitochondrial activity was observed. Thus, the C5 and 2-thio modifications act synergistically in promoting efficient cognate codon decoding. Partial inactivation of MTU1 in HeLa cells by small interference RNA also reduced their oxygen consumption and resulted in mitochondria with defective membrane potentials, which are similar phenotypic features observed in MERRF.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Cell Respiration
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GTP Phosphohydrolases / genetics
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GTP Phosphohydrolases / metabolism
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism
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HeLa Cells
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Humans
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Mass Spectrometry
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Mitochondria / enzymology*
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Mitochondria / genetics
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Mitochondria / metabolism
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Mitochondria / pathology
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Mitochondrial Diseases / enzymology
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Mitochondrial Diseases / genetics
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Mitochondrial Proteins / chemistry
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Mitochondrial Proteins / genetics
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Mitochondrial Proteins / metabolism*
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Molecular Sequence Data
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Mutation / genetics
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Oxygen Consumption
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Phenotype
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RNA / biosynthesis
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RNA / genetics*
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RNA / metabolism*
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RNA Interference
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RNA, Mitochondrial
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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RNA, Transfer, Lys / biosynthesis
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RNA, Transfer, Lys / genetics
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RNA, Transfer, Lys / metabolism
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RNA-Binding Proteins
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Saccharomyces cerevisiae / enzymology*
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / growth & development
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
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Sequence Alignment
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Taurine / metabolism
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tRNA Methyltransferases / chemistry
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tRNA Methyltransferases / genetics
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tRNA Methyltransferases / metabolism*
Substances
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Carrier Proteins
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MTO1 protein, S cerevisiae
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Mitochondrial Proteins
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RNA, Mitochondrial
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RNA, Small Interfering
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RNA, Transfer, Lys
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RNA-Binding Proteins
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Saccharomyces cerevisiae Proteins
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Taurine
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RNA
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tRNA Methyltransferases
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SLM3 protein, S cerevisiae
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TRMU protein, human
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GTP Phosphohydrolases
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GTP-Binding Proteins
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MSS1 protein, S cerevisiae