JMJD6 (UniProt/Swiss-Prot entry Q6NYC1) can act both as a histone arginine demethylase and a lysyl-hydroxylase. As an arginine demethylase it is able to demethylate histone H3 at Arg2 (H3R2me) and histone H4 at Arg3 (H4R3me), thereby playing an important role in the histone code. JMJD6 can also catalyze the 5-hydroxylation on specific lysine residues of target proteins such as U2AF2/U2AF65 thereby acting as a regulator of RNA splicing. It is required for differentiation of multiple organs during embryogenesis and is a key regulator of hematopoietic differentiation.