Dear Editor,

DNA N6-methyladenine (6mA) modifi-cation, which was found in bacteria, archaea, viruses, and eukaryotes ranging from unicellular protists, fungi, and ciliates to multicellular plants and animals, has been proposed to be potentially associated with some important biological processes such as gene expression regulation and oncogenic pathways (Wion and Casadesus, 2006; Boulias and Greer, 2022). Yet, recent studies highlighted the arguments on the rarity, source, and origin of 6mA in invertebrates and vertebrates (Boulias and Greer, 2022). Removal of 6mA was suggested to be achieved by AlkB family dealkylating enzymes including ALKBH1 and ALKBH4 in mammals and NMAD-1 in Caenorhabditis elegans (Greer et al., 2015; Wu et al., 2016; Xiao et al., 2018; Xie et al., 2018). Silencing genes encoding these candidate enzymes induced global 6mA accumulation in vivo; however, in vitro catalytic activities and specificities of these enzymes remain to be characterized. AlkB family members are Fe(II)/α-ketoglutarate (α-KG)-dependent dioxygenases, which catalyze demethylation of various substrates including DNAs, RNAs, and proteins (Li et al., 2013; Fedeles et al., 2015; Kweon et al., 2019). C. elegans NMAD-1 was shown to exhibit in vitro catalytic activity on DNA 6mA and to be essential for DNA repair and replication during meiosis in the germline, but its substrate was unidentified (Wang et al., 2019). Remarkably, ALKBH4, the closest mammalian ortholog of NMAD-1, was shown to mediate demethylation of DNA 6mA and Lys84 mono-methylated actin (K84me1), suggesting alternative functional roles (Li et al., 2013; Kweon et al., 2019). Intriguingly, ALKBH4-dependent actin K84me1 demethylation facilitates the binding of non-muscle myosin II to unmethylated actin and thus regulates actomyosin function, indicating an important role of ALKBH4 in cytokinesis (Li et al., 2013). Whether the actin methylation exists in