At least three types of PRMT enzymes have been identified in mammalian cells. These enzymes have been shown to have essential regulatory functions by methylation of key proteins in several fundamental areas. These protein include nuclear proteins (Histone-2A, 3, 4), IL enhancer binding factor, nuclear factors (NF-45, -90, ILF3, Nucleolin, STAT1, Poly(A)-binding protein II), cell cycle proteins (phosphoprotein phosphatase 2A), signal transduction proteins (FGF2, Fibrillarin, FN, INFAR1, Jak, MBP, Src-adaptor Sam68), etc.