Hetero-oligomerization between UGT2A1_i1 and UGT2A1_i2 demonstrated by coIP. A, the UGT2A1_i1_V5/UGT2A1_i2_FLAG complex was immunoprecipitated with an anti-FLAG antibody, then visualized with a HRP-labeled V5 antibody (lane 5). Homogenates from cells overexpressing UGT2A1_i1_V5 (lane 1) or UGT2A1_i2_FLAG (lane 2) alone were used as negative controls. Dynabeads without antibody conjugation were used as an additional negative control (lane 3). The UGT2A1_i1_V5/UGT2A1_i2_FLAG complex was immunoprecipitated with an anti-V5 antibody, and then visualized with an anti-V5-HRP antibody as a positive control (lane 4). B, the UGT2A1_i1_V5/UGT2A1_i2_FLAG complex was immunoprecipitated with an anti-V5 antibody, then visualized with a HRP-labeled FLAG antibody (lane 5). Homogenates from cells overexpressing UGT2A1_i1_V5 (lane 1) or UGT2A1_i2_FLAG (lane 2) alone were used as negative controls. Dynabeads without antibody conjugation were used as an additional negative control (lane 3). The UGT2A1_i1_V5/UGT2A1_i2_FLAG complex was immunoprecipitated with an anti-FLAG antibody, and then visualized with an anti-FLAG-HRP antibody as a positive control (lane 4). All coIP experiments were repeated four to six times to verify the protein-protein interactions between UGT2A1_i1 and UGT2A1_i2.