Fig. 2. PRMT9 interacts with SAP145 and SAP49.

(a) TAP-tag purification of PRMT9 protein complex from HeLa cells. HeLa cells were transiently transfected with either empty TAP-tag vector (TAP-Ctrl) or TAP-tag PRMT9 (TAP-PRMT9). A standard TAP procedure was applied. The eluted protein complex was separated by SDS-PAGE and silver-stained. The indicated gel slices were processed for protein identification using mass spectrometry. Actin, heat shock protein 70 (HSP70), and 40S Ribosomal Protein S3 (RS3) are likely non-specific interacting proteins.

(b) PRMT9 and SAP145 co-immunoprecipitate. Reciprocal Co-IP was performed in HeLa cells. Total cell lysates were immunoprecipitated with rabbit control IgG, αSAP145 antibody (left), and mouse control IgG, αPRMT9 antibody (right). The eluted protein samples were detected by western blotting with αPRMT9 and αSAP145 antibodies. The input samples were detected with αPRMT9 and αSAP145 antibodies, respectively.

(c) PRMT9 and SAP49 co-immunoprecipitate. HeLa cells were transiently transfected with either GFP control vector or GFP-SAP49 plasmids. Total cell lysates were immunoprecipitated with αGFP antibody. The eluted protein samples were detected by western blotting with αPRMT9 and αGFP antibodies. The input samples were detected with αPRMT9.

(d) Among all the PRMTs, only PRMT9 interacts with SAP145. HeLa cells were transiently transfected with control GFP vector and GFP-PRMTs (1 through 9). The total cell lysates were immunoprecipitated with αGFP antibody. The eluted protein samples were detected by western blotting with αSAP145, αRPS2 and αGFP antibodies. The input samples were detected with αSAP145 and αRPS2 antibodies.