Protein arginine methyltransferases are a class of enzymes. They transfer a methyl group from the cofactor S-adenosylmethionine (SAM) onto the arginine omega nitrogens of substrate proteins, including histones. There are three subclasses based on their product specificity: type I, II, and III PRMTs asymmetrically dimethylate, symmetrically dimethylate, and monomethylate their...