Human AlkB homolog 1 contains distinct AP lyase and 6mA demethylase active sites

Abstract

Bacterial AlkB and its human homologs are members of the Fe(II)/2-oxoglutarate dependent oxygenases that are known to be involved in DNA repair. AlkB homolog 1 (ALKBH1) directly repairs alkylation damage, acting as a demethylase at 3-methyl cytosine sites in single-stranded DNA. However, its exact functional role is not understood. It was recently discovered that ALKBH1 has the additional ability to demethylate at 6-methyl adenine (6mA) sites in mouse embryonic stem cells. This present study confirmed 6mA demethylase activity in E. coli-produced ALKBH1 through activity assays analyzed via gel electrophoresis. ALKBH1 also possesses apurinic/apyrimidinic (AP) lyase activity, and this study compared both the 6mA demethylase and AP lyase activities of variants to assess the possibility of distinct active sites for these two functions. Comparing the two distinct functions of ALKBH1 may give further insight into its biological significance, and have important implications for DNA repair and expression.