title: N7-Methylguanine at position 46 (m7G46) in tRNA from Thermus thermophilus is required for cell viability at high temperatures through a tRNA modification network.
abstract: N(7)-methylguanine at position 46 (m(7)G46) in tRNA is produced by tRNA (m(7)G46) methyltransferase (TrmB). To clarify the role of this modification, we made a trmB gene disruptant (DeltatrmB) of Thermus thermophilus, an extreme thermophilic eubacterium. The absence of TrmB activity in cell extract from the DeltatrmB strain and the lack of the m(7)G46 modification in tRNA(Phe) were confirmed by enzyme assay, nucleoside analysis and RNA sequencing. When the DeltatrmB strain was cultured at high temperatures, several modified nucleotides in tRNA were hypo-modified in addition to the lack of the m(7)G46 modification. Assays with tRNA modification enzymes revealed hypo-modifications of Gm18 and m(1)G37, suggesting that the m(7)G46 positively affects their formations. Although the lack of the m(7)G46 modification and the hypo-modifications do not affect the Phe charging activity of tRNA(Phe), they cause a decrease in melting temperature of class I tRNA and degradation of tRNA(Phe) and tRNA(Ile). (35)S-Met incorporation into proteins revealed that protein synthesis in DeltatrmB cells is depressed above 70 degrees C. At 80 degrees C, the DeltatrmB strain exhibits a severe growth defect. Thus, the m(7)G46 modification is required for cell viability at high temperatures via a tRNA modification network, in which the m(7)G46 modification supports introduction of other modifications.
authors.affiliation: Department of Materials Science and Biotechnology, Ehime University, Bunkyo 3, Matsuyama, Ehime 790-8577, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Tomikawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Yokogawa
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Kanai
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hori
mesh_terms: D049148:Aminoacylation; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry; D017353:Gene Deletion; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D006358:Hot Temperature; D008715:Methionine / Q000378:metabolism; D009691:Nucleic Acid Denaturation; D012323:RNA Processing, Post-Transcriptional; D012343:RNA, Transfer / Q000737:chemistry* / Q000378:metabolism; D012360:RNA, Transfer, Phe / Q000737:chemistry / Q000378:metabolism; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D012359:tRNA Methyltransferases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012360:RNA, Transfer, Phe; D006147:Guanine; C008450:7-methylguanine; D012343:RNA, Transfer; D008715:Methionine; D012359:tRNA Methyltransferases; C036814:tRNA (guanine-N7-)-methyltransferase