A pathogenic point mutation reduces stability of mitochondrial mutant tRNA(Ile).
Point mutations in mitochondrial tRNA genes are responsible for individual subgroups of mitochondrial encephalomyopathies. We have recently reported that point mutations in the tRNA(Leu)(UUR) and tRNA(Lys) genes cause a defect in the normal modification at the first nucleotide of the anticodon. As part of a systematic analysis of pathogenic mutant mitochondrial tRNAs, we purified tRNA(Ile) with a point mutation at nucleotide 4269 to determine its nucleotide sequence, including modified nucleotides. We found that, instead of causing a defect in the post-transcriptional modification, a pathogenic point mutation in the mitochondrial tRNA(Ile) reduced the stability of the mutant tRNA molecule, resulting in a low steady-state level of aminoacyl-tRNA. The reduced stability was confirmed by examining the life-span of the mutant tRNA(Ile) both in vitro and in vivo, as well as by monitoring its melting profile. Our finding indicates that the mutant tRNA(Ile) itself is intrinsically unstable.
Yasukawa
T
T
Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Hino
N
N
Suzuki
T
T
Watanabe
K
K
Ueda
T
T
Ohta
S
S
D000215:Acylation; D000926:Anticodon / Q000235:genetics; D001483:Base Sequence; D002457:Cell Extracts; D004996:Ethidium / Q000494:pharmacology; D006207:Half-Life; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics* / Q000473:pathology*; D017237:Mitochondrial Encephalomyopathies / Q000235:genetics* / Q000473:pathology; D008969:Molecular Sequence Data; D009691:Nucleic Acid Denaturation; D017354:Point Mutation / Q000235:genetics*; D012323:RNA Processing, Post-Transcriptional; D020871:RNA Stability; D012355:RNA, Transfer, Ile / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D017423:Sequence Analysis, RNA; D013696:Temperature; D014158:Transcription, Genetic / Q000187:drug effects
D000926:Anticodon; D002457:Cell Extracts; D012355:RNA, Transfer, Ile; D004996:Ethidium