Methylates (mono and asymmetric dimethylation) the guanidino nitrogens of arginyl residues present in a glycine and arginine-rich domain. Type I arginine methyltransferase active on both histones and non-histone proteins. Mediates the methylation of MED36A. Interacts with FIB2 and PRMT11. Belongs to the class I-like SAM-binding methyltransferase superfamily. Protein arginine N-methyltransferase family.