title: Eukaryotic wobble uridine modifications promote a functionally redundant decoding system.
abstract: The translational decoding properties of tRNAs are modulated by naturally occurring modifications of their nucleosides. Uridines located at the wobble position (nucleoside 34 [U(34)]) in eukaryotic cytoplasmic tRNAs often harbor a 5-methoxycarbonylmethyl (mcm(5)) or a 5-carbamoylmethyl (ncm(5)) side chain and sometimes an additional 2-thio (s(2)) or 2'-O-methyl group. Although a variety of models explaining the role of these modifications have been put forth, their in vivo functions have not been defined. In this study, we utilized recently characterized modification-deficient Saccharomyces cerevisiae cells to test the wobble rules in vivo. We show that mcm(5) and ncm(5) side chains promote decoding of G-ending codons and that concurrent mcm(5) and s(2) groups improve reading of both A- and G-ending codons. Moreover, the observation that the mcm(5)U(34)- and some ncm(5)U(34)-containing tRNAs efficiently read G-ending codons challenges the notion that eukaryotes do not use U-G wobbling.
authors.affiliation: Department of Molecular Biology, Umeå University, 901 87 Umeå, Sweden.
authors.forename: Marcus J O
authors.initials: MJ
authors.lastname: Johansson
authors.forename: Anders
authors.initials: A
authors.lastname: Esberg
authors.forename: Bo
authors.initials: B
authors.lastname: Huang
authors.forename: Glenn R
authors.initials: GR
authors.lastname: Björk
authors.forename: Anders S
authors.initials: AS
authors.lastname: Byström
mesh_terms: D000926:Anticodon / Q000737:chemistry* / Q000235:genetics*; D001483:Base Sequence; D003062:Codon / Q000235:genetics; D005800:Genes, Fungal; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics; D012343:RNA, Transfer / Q000737:chemistry / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D046249:Transfer RNA Aminoacylation; D014529:Uridine / Q000737:chemistry*
chemical_list: D000926:Anticodon; D003062:Codon; D012331:RNA, Fungal; D012343:RNA, Transfer; D014529:Uridine