Western blot was performed using TRIM21 Polyclonal Antibody (Product # PA5-22294) and a 54 kDa band corresponding to TRIM21 was observed across all cell lines tested and was observed to be upregulated upon treatment of HeLa cells with IFNa and HCT116 with cisplatin. Whole cell extracts (30 µg lysate) of HeLa (Lane 1), HeLa treated with with IFNa (10 ng/mL, 16 hours) (Lane 2), HCT 116 (Lane 3), HCT 116 treated with with cisplatin (3.75 µg/mL, 24 hours) (Lane 4), HT-29 (Lane 5) and RT-4 (Lane 6) were electrophoresed using NuPAGE™ 4-12% Bis-Tris Protein Gel (Product # NP0321BOX), 10 well. Resolved proteins were then transferred onto a nitrocellulose membrane (Product # IB23001) by iBlot® 2 Dry Blotting System (Product # IB21001). The blot was probed with the primary antibody (1:1000 dilution) and detected by chemiluminescence with Goat anti-Rabbit IgG (Heavy Chain) Superclonal™ Recombinant Secondary Antibody, HRP (Product # A27036, 1:20,000 dilution) using the iBright™ FL1500 Imaging System (Product # A44115). Chemiluminescent detection was performed using SuperSignal™ West Pico PLUS Chemiluminescent Substrate (Product # 34580). Upregulation of TRIM21 expression upon cell treatment demonstrates specificity of the antibody. Some uncharacterized bands were observed between 15-20 kDa.