DOT1L and acute myeloid leukemia: Firstly, DOT1L is the only known methyltrasferase that catalyze mono-, di-, and tri-methylation of H3K79, and only recently a histone demethylase that can catalyze the removal of di- and tri-methyl groups from the H3K79 lysine residue has been identified (74); therefore, most likely DOT1L plays an essential role in AML cells.