title: NSUN3 methylase initiates 5-formylcytidine biogenesis in human mitochondrial tRNA(Met).
abstract: In human mitochondria, the AUA codon encodes methionine via a mitochondrial transfer RNA for methionine (mt-tRNA(Met)) that contains 5-formylcytidine (f(5)C) at the first position of the anticodon (position 34). f(5)C34 is required for deciphering the AUA codon during protein synthesis. Until now, the biogenesis and physiological role of f(5)C34 were unknown. We demonstrate that biogenesis of f(5)C34 is initiated by S-adenosylmethionine (AdoMet)-dependent methylation catalyzed by NSUN3, a putative methyltransferase in mitochondria. NSUN3-knockout cells showed strong reduction in mitochondrial protein synthesis and reduced oxygen consumption, leading to deficient mitochondrial activity. We reconstituted formation of 5-methylcytidine (m(5)C) at position 34 (m(5)C34) on mt-tRNA(Met) with recombinant NSUN3 in the presence of AdoMet, demonstrating that NSUN3-mediated m(5)C34 formation initiates f(5)C34 biogenesis. We also found two disease-associated point mutations in mt-tRNA(Met) that impaired m(5)C34 formation by NSUN3, indicating that a lack of f(5)C34 has pathological consequences.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Nakano
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
authors.forename: Layla
authors.initials: L
authors.lastname: Kawarada
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Iwata
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Asano
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Tokyo, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D003562:Cytidine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D006801:Humans; D008780:Methyltransferases / Q000378:metabolism*; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D000077278:RNA, Mitochondrial; D012358:RNA, Transfer, Met / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000077278:RNA, Mitochondrial; D012358:RNA, Transfer, Met; C086073:5-formylcytidine; D003562:Cytidine; D012313:RNA; D008780:Methyltransferases