Characterization of the human AlkB homologue 8 (hABH8)

Abstract

The human genome encodes 8 homologues of the E.coli protein AlkB, hABH1-8. AlkB, hABH2, and hABH3 repair DNA and RNA by oxidative demetylation in the presence of Fe2+ and 2-oxoglutarate (2OG). The functions of the remaining six human homologues are yet to be characterized. hABH8 differs from the other AlkB proteins by having a methyltransferase and a RNA recognition motif in addition to the AlkB domain. The methyltransferase domain has sequence similarity to the S.cerevisiae protein Trm9 which has been shown to methylate tRNA, so hABH8 is likely to use RNA as substrate. Plasmids were made that encode hABH8 mutants, containing amino acid changes or deletions. These mutants were tested together with the wild-type protein both in vitro and in vivo to check whether hABH8 has a regulatory role in selenoprotein synthesis, without any results. In addition, protein-protein and RNA-protein interaction studies were performed. The protein-protein interaction assays confirmed previous results obtained from a Yeast-Two-Hybrid screen identifying a possible interaction partner of hABH8. The RNA-protein interaction studies indicated a connection between hABH8 and specific tRNA isoacceptors. Although there are indications of hABH8 being involved in tRNA modification, further studies are needed to determinate the complete function of hABH8.