title: The 7472insC mitochondrial DNA mutation impairs the synthesis and extent of aminoacylation of tRNASer(UCN) but not its structure or rate of turnover.
abstract: The 7472insC mitochondrial DNA mutation in the tRNA(Ser(UCN)) gene is associated with sensorineural deafness combined, in some patients, with a wider neurological syndrome. In cultured cybrid cells it causes a 70% decrease in tRNA(Ser(UCN)) abundance and mild respiratory impairment, previously suggested to be due to decreased tRNA stability. When mitochondrial transcription was blocked by ethidium bromide treatment, the half-life of the mutant tRNA was not significantly different from that of wild-type tRNA(Ser(UCN)). Over-expression of mitochondrial translational elongation factor EF-Tu also had no effect on the mutant phenotype. However, during recovery from prolonged ethidium bromide treatment, the synthesis of the mutant tRNA(Ser(UCN)) was specifically impaired, without polarity effects on downstream tRNAs of the light strand transcription unit. We infer that the mutation acts posttranscriptionally to decrease tRNA(Ser(UCN)) abundance by affecting its synthesis rather than its stability. The extent of aminoacylation of the mutant tRNA was also decreased by approximately 25%. In contrast, the mutation had no detectable effect on tRNA(Ser(UCN)) base modification or structure other than the insertion of an extra guanosine templated by the mutation, which was structurally protected from nuclease digestion like the surrounding nucleotides. These findings indicate a common molecular process underlying sensorineural deafness caused by mitochondrial tRNA(Ser(UCN)) mutations.
authors.affiliation: Institute of Medical Technology and Tampere University Hospital, FIN-33014 University of Tampere, Finland.
authors.forename: Marina
authors.initials: M
authors.lastname: Toompuu
authors.forename: Takehiro
authors.initials: T
authors.lastname: Yasukawa
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Suzuki
authors.forename: Terhi
authors.initials: T
authors.lastname: Hakkinen
authors.forename: Johannes N
authors.initials: JN
authors.lastname: Spelbrink
authors.forename: Kimitsuna
authors.initials: K
authors.lastname: Watanabe
authors.forename: Howard T
authors.initials: HT
authors.lastname: Jacobs
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D004272:DNA, Mitochondrial; D004996:Ethidium / Q000494:pharmacology; D005838:Genotype; D006151:Guanosine / Q000737:chemistry; D006319:Hearing Loss, Sensorineural / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010641:Phenotype; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012313:RNA / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional; D012343:RNA, Transfer / Q000378:metabolism; D012362:RNA, Transfer, Ser / Q000737:chemistry*; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D004272:DNA, Mitochondrial; D009841:Oligonucleotides; D012362:RNA, Transfer, Ser; D006151:Guanosine; D012313:RNA; D004247:DNA; D012343:RNA, Transfer; D004996:Ethidium; D010100:Oxygen