| Protein arginine N-methyltransferases (PRMTs) constitute a family of eukaryotic enzymes that catalyze the sequential transfer of methyl groups from S-adenosyl-L-methionine to the guanidino nitrogens of arginine residues within proteins. Type I PRMTs catalyze the formation of asymmetric ω-NG, N G-dimethylarginine residues, whereas type II PRMTs catalyze the formation of symmetric ω-NG, N′G-dimethylarginine residues. The methylation of arginine residues has been implicated in the regulation of signal transduction, gene transcription, and RNA transport. Many known type I methyl-accepting substrates are modified within glycine- and arginine-rich domains and interact with RNA. The methylation of these proteins appears to be affected by the presence of RNA, but in the case of SAM68 binding to its WW- and SH3-containing ligands, modulates protein-protein interactions.; Several PRMTs catalyze the type I methyl-transfer reaction, including PRMT1, PRMT3, PRMT4, and the recently discovered PRMT6, whereas PRMT5 represents the only known type II enzyme. The predominant PRMT in mammalian cells is associated with the PRMT1 catalytic polypeptide chain. Compared to the broad substrate specificity exhibited by PRMT1, PRMT3 contains a zinc finger domain that contributes to its narrow substrate specificity. The discovery of PRMT6 and PRMT7, described herein, opens wide the study of an emerging PRMT family. |
