PRMT5 can methylate histone H4 at arginine-4 (H4R3)and histone H2A at arginine-4 (H2AR3) (Pal et al. 2004). Symmetric dimethylation of histone H4 arginine-4 (H4R3me2s) by PRMT5 is required for subsequent DNA methylation. The histone-binding protein Cooperator of PRMT5 (COPRS) guides PRMT5:WDR77 to methylate histone H4 arginine-4 (H4R3) rather than histone H3 arginine-9 (H3R8) (Lacroix et al. 2008). H4R3me2s serves as a direct binding target for the DNA methyltransferase DNMT3A, which interacts through the ADD domain, which contains a PHD motif (Zhao et al. 2009).