Arginine methylation is a prevalent post-translational modification found on both nuclear and cytoplasmic proteins. The methylation of arginine residues is catalyzed by the protein arginine Nmethyltransferase (PRMT) family of enzymes. Proteins that are arginine methylated are involved in a number of different cellular processes, including transcriptional regulation, RNA metabolism and DNA damage repair (Bedford and Richard, 2005). Most PRMTs methylate glycine- and arginine-rich patches (GAR motifs) within their substrates.

Reference
Wiki: Arginine methylation