Protein arginine methyltransferases (PRMTs) are enzymes that transfer methyl groups to the arginine residues of histones and other proteins. Arginine methylation is an important posttranslational modification process that plays functional roles in transcriptional control, splicing, DNA repair, and signaling [, , ]. PRMTs use S-adenosylmethionine(SAM or AdoMet)-dependent methylation to modify the guanidino nitrogens of the arginine side chain by adding one or two methyl groups []. According to their methylation status, the PRMT enzymes are classified into different group types. While the type-I PRMT enzymes catalyse the formation of monomethylarginine (MMA) and asymmetric dimethylarginine (aDMA), the type-II PRMT enzymes form MMA and symmetric dimethylarginine (sDMA). The enzymes PRMT1, PRMT3, PRMT4, PRMT6 and PRMT8 belong to the type-I and PRMT5, PRMT7 and PRMT9 to type-II.
