We performed co-immunoprecipitation assays in myeloma cell lines to confirm the binding between A3B and the following representative A3B-interacting proteins: SAFB, SRSF7, Matrin-3, interleukin enhancer-binding factor 2 (ILF2), DHX9, RBMX, hnRNP A1, PTBP1, hnRNP K, hnRNP A3 and hnRNP C. Myeloma cell lysates were subjected to co-immunoprecipitation assays using anti-FLAG M2 affinity gel with or without RNase A. The anti-FLAG antibody specifically co-immunoprecipitated the interacting proteins that were detected by immunoblotting (Fig. 2 and Supplementary Fig. S6). Here, PTBP1 is linked to plasma cell myeloma.