Publications

• Human AlkB homolog ABH8 is a tRNA methyltransferase required for wobble uridine modification and DNA damage survival.

  Fu D., Brophy J.A., Chan C.T., Atmore K.A., Begley U., Paules R.S., Dedon P.C., Begley T.J., Samson L.D.

  tRNA nucleosides are extensively modified to ensure their proper function in translation. However, many of the enzymes responsible for tRNA modifications in mammals await identification. Here, we show that human AlkB homolog 8 (ABH8) catalyzes tRNA methylation to generate 5-methylcarboxymethyl uri ... >> More

  tRNA nucleosides are extensively modified to ensure their proper function in translation. However, many of the enzymes responsible for tRNA modifications in mammals await identification. Here, we show that human AlkB homolog 8 (ABH8) catalyzes tRNA methylation to generate 5-methylcarboxymethyl uridine (mcm(5)U) at the wobble position of certain tRNAs, a critical anticodon loop modification linked to DNA damage survival. We find that ABH8 interacts specifically with tRNAs containing mcm(5)U and that purified ABH8 complexes methylate RNA in vitro. Significantly, ABH8 depletion in human cells reduces endogenous levels of mcm(5)U in RNA and increases cellular sensitivity to DNA-damaging agents. Moreover, DNA-damaging agents induce ABH8 expression in an ATM-dependent manner. These results expand the role of mammalian AlkB proteins beyond that of direct DNA repair and support a regulatory mechanism in the DNA damage response pathway involving modulation of tRNA modification. << Less

  Mol. Cell. Biol. 30:2449-2459(2010) [PubMed] [EuropePMC]

• Novel methyltransferase for modified uridine residues at the wobble position of tRNA.

  Kalhor H.R., Clarke S.

  We have identified a novel tRNA methyltransferase in Saccharomyces cerevisiae that we designate Trm9. This enzyme, the product of the YML014w gene, catalyzes the esterification of modified uridine nucleotides, resulting in the formation of 5-methylcarbonylmethyluridine in tRNA(Arg3) and 5-methylca ... >> More

  We have identified a novel tRNA methyltransferase in Saccharomyces cerevisiae that we designate Trm9. This enzyme, the product of the YML014w gene, catalyzes the esterification of modified uridine nucleotides, resulting in the formation of 5-methylcarbonylmethyluridine in tRNA(Arg3) and 5-methylcarbonylmethyl-2-thiouridine in tRNA(Glu). In intact yeast cells, disruption of the TRM9 gene results in the complete loss of these modified wobble bases and increased sensitivity at 37 degrees C to paromomycin, a translational inhibitor. These results suggest a role for this potentially reversible methyl esterification reaction when cells are under stress. << Less

  Mol. Cell. Biol. 23:9283-9292(2003) [PubMed] [EuropePMC]

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

  Songe-Moller L., van den Born E., Leihne V., Vagbo C.B., Kristoffersen T., Krokan H.E., Kirpekar F., Falnes P.O., Klungland A.

  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 ... >> More

  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. << Less

  Mol. Cell. Biol. 30:1814-1827(2010) [PubMed] [EuropePMC]