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Nucleic Acids Res. 2014 Aug;42(14):9350-65. doi: 10.1093/nar/gku618. Epub 2014 Jul 24.

Discovery of the β-barrel-type RNA methyltransferase responsible for N6-methylation of N6-threonylcarbamoyladenosine in tRNAs.

Author information

1
Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
2
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.
3
University of Florida Genetics Institute Department of Microbiology, University of Florida, Gainesville, Florida 32611-0700, USA.
4
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.

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.

PMID:
25063302
PMCID:
PMC4132733
DOI:
10.1093/nar/gku618
[Indexed for MEDLINE]
Free PMC Article
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