Human HNRNPA1, HNRNPH1, HNRNPK, SFPQ, KHDRBS1, and CNBP genes were amplified from 293T complementary DNA and further cloned into the pGEX-6P-1 vector (GE Healthcare Life Sciences). Human PRMT1 and mouse PRMT4 genes were also cloned into the pGEX-6P-1 vector. All of these plasmids were transformed into E. coli BL21 Star (DE3). Bacteria were grown in LB medium at 37°C, 200 rpm until OD600 0.6 and induced with 0.4 mM IPTG at 25°C for 5 hours. Cells were harvested by centrifugation and resuspended in 50 mM tris-HCl (pH 8.0), 150 mM NaCl, and 1 mM DTT and further lysed by sonication. The cell lysate was clarified by centrifugation, and the supernatant was filtered through 0.4-μm syringe filter and applied to 5-ml GSTrap FF column (GE Healthcare) on ÄKTAxpress system for affinity purification. GST-tagged proteins were eluted with 50 mM tris-HCl (pH 8.0) and 10 mM reduced glutathione and frozen at −80°C.