Mammalian ALKBH8 possesses tRNA methyltransferase activity required for the biogenesis of multiple wobble uridine modifications implicated in translational decoding

Mol Cell Biol. 2010 Apr;30(7):1814-27. doi: 10.1128/MCB.01602-09. Epub 2010 Feb 1.


Uridines in the wobble position of tRNA are almost invariably modified. Modifications can increase the efficiency of codon reading, but they also prevent mistranslation by limiting wobbling. In mammals, several tRNAs have 5-methoxycarbonylmethyluridine (mcm5U) or derivatives thereof in the wobble position. Through analysis of tRNA from Alkbh8-/- mice, we show here that ALKBH8 is a tRNA methyltransferase required for the final step in the biogenesis of mcm5U. We also demonstrate that the interaction of ALKBH8 with a small accessory protein, TRM112, is required to form a functional tRNA methyltransferase. Furthermore, prior ALKBH8-mediated methylation is a prerequisite for the thiolation and 2'-O-ribose methylation that form 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) and 5-methoxycarbonylmethyl-2'-O-methyluridine (mcm5Um), respectively. Despite the complete loss of all of these uridine modifications, Alkbh8-/- mice appear normal. However, the selenocysteine-specific tRNA (tRNASec) is aberrantly modified in the Alkbh8-/- mice, and for the selenoprotein Gpx1, we indeed observed reduced recoding of the UGA stop codon to selenocysteine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AlkB Homolog 8, tRNA Methyltransferase
  • Amino Acid Sequence
  • Animals
  • Dioxygenases / genetics
  • Dioxygenases / metabolism*
  • Gene Targeting
  • Humans
  • Mice
  • Mice, Knockout
  • Molecular Sequence Data
  • Molecular Structure
  • Nucleic Acid Conformation
  • Protein Biosynthesis*
  • RNA, Transfer / chemistry
  • RNA, Transfer / genetics*
  • RNA, Transfer / metabolism
  • Sequence Alignment
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
  • Thiouridine / analogs & derivatives
  • Thiouridine / chemistry
  • Thiouridine / metabolism
  • Uridine / analogs & derivatives
  • Uridine / chemistry
  • Uridine / genetics*
  • Uridine / metabolism
  • tRNA Methyltransferases / genetics
  • tRNA Methyltransferases / metabolism*


  • 5-carbomethoxymethyl-2-thiouridine
  • Thiouridine
  • 5-methoxycarbonylmethyluridine
  • RNA, Transfer
  • Dioxygenases
  • ALKBH8 protein, mouse
  • AlkB Homolog 8, tRNA Methyltransferase
  • tRNA Methyltransferases
  • Uridine