title: Discovery of the β-barrel-type RNA methyltransferase responsible for N6-methylation of N6-threonylcarbamoyladenosine in tRNAs.
abstract: Methylation is a versatile reaction involved in the synthesis and modification of biologically active molecules, including RNAs. N(6)-methyl-threonylcarbamoyl adenosine (m(6)t(6)A) is a post-transcriptional modification found at position 37 of tRNAs from bacteria, insect, plants, and mammals. Here, we report that in Escherichia coli, yaeB (renamed as trmO) encodes a tRNA methyltransferase responsible for the N(6)-methyl group of m(6)t(6)A in tRNA(Thr) specific for ACY codons. TrmO has a unique single-sheeted β-barrel structure and does not belong to any known classes of methyltransferases. Recombinant TrmO employs S-adenosyl-L-methionine (AdoMet) as a methyl donor to methylate t(6)A to form m(6)t(6)A in tRNA(Thr). Therefore, TrmO/YaeB represents a novel category of AdoMet-dependent methyltransferase (Class VIII). In a ΔtrmO strain, m(6)t(6)A was converted to cyclic t(6)A (ct(6)A), suggesting that t(6)A is a common precursor for both m(6)t(6)A and ct(6)A. Furthermore, N(6)-methylation of t(6)A enhanced the attenuation activity of the thr operon, suggesting that TrmO ensures efficient decoding of ACY. We also identified a human homolog, TRMO, indicating that m(6)t(6)A plays a general role in fine-tuning of decoding in organisms from bacteria to mammals.
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors: Satoshi
authors: S
authors: Kimura
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors: Kenjyo
authors: K
authors: Miyauchi
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors: Yoshiho
authors: Y
authors: Ikeuchi
authors: Genetics and Genomics Graduate Program University of Florida Genetics Institute Department of Microbiology, University of Florida, Gainesville, Florida 32611-0700, USA Institut de Génétique et Microbiologie, Université of Paris-Sud, Orsay, France.
authors: Patrick C
authors: PC
authors: Thiaville
authors: University of Florida Genetics Institute Department of Microbiology, University of Florida, Gainesville, Florida 32611-0700, USA.
authors: Valérie de
authors: Vd
authors: Crécy-Lagard
authors: Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan ts@chembio.t.u-tokyo.ac.jp.
authors: Tsutomu
authors: T
authors: Suzuki
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D003062:Codon; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008745:Methylation; D011506:Proteins / Q000378:metabolism; D012362:RNA, Transfer, Ser / Q000378:metabolism; D012363:RNA, Transfer, Thr / Q000737:chemistry / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000378:metabolism; D013379:Substrate Specificity; D012359:tRNA Methyltransferases / Q000235:genetics / Q000378:metabolism*
chemical_list: D003062:Codon; D029968:Escherichia coli Proteins; C111429:N6-methyl-N6-threonylcarbamoyladenosine; D011506:Proteins; D012362:RNA, Transfer, Ser; D012363:RNA, Transfer, Thr; C003268:N(6)-(N-threonylcarbonyl)adenosine; D012436:S-Adenosylmethionine; C498548:TRMO protein, human; C000592805:TrmO protein, E coli; D012359:tRNA Methyltransferases; D000241:Adenosine