SGC2085 is an effective and selective coactivator-associated arginine methyltransferase 1 (CARM1) inhibitor (IC50: 50 nM).

With the exception of PRMT6 (IC50=5.2 μM), SGC2085 does not inhibit other PRMTs. SGC2085 also shows complete selectivity against a panel of 21 human protein methyltrans- ferases tested at three different concentrations (1,10, and 50 μM). To characterize the mechanism of action of SGC2085 in solution, IC50 values are determined at various concentrations of SAM and peptide substrate. Increasing concentration of substrate peptide or cofactor does not affect IC50 values, indicative of a noncompetitive mechanism of inhibition, which has been previously shown for other protein methyltransferase inhibitors binding at the substrate pocket[1]. No cellular activity is observed for SGC2085 when tested up to 10 μM (48 h exposure in HEK293 cells), while methylation of BAF155 is abrogated by 10 μM of the dual CARM1/PRMT6 inhibitor MS049. We assume that the absence of cellular activity for SGC2085 is due to poor permeability[1].

SGC2085 is dissolved in DMSO and diluted with the appropriate medium before use. HEK293 cells are grown in 12-well plates in DMEM supplemented with 10% FBS, penicillin (100 U/mL), and streptomycin (100 μg/mL). Thirty per cent confluent cells are treated with inhibitors or DMSO. After 48 h, media are removed and cells are lysed in 100 μL of total lysis buffer (20 mM Tris-HCl pH 8.0, 150 mM NaCl, 1 mM EDTA, 10 mM MgCl2, 0.5% Triton X-100, 12.5 U/mL benzonase), complete EDTA-free protease inhibitor cocktail. After 3 min incubation at room temperature, SDS is added to 1% final concentration. Lysates are run on SDS-PAGE, and immunoblotting is done as outlined below to determine the levels of unmethylated and methylated BAF155[1].