Identification of putative ERRα binding sites on OTUB1 promoter. (A) An empty vector or an ERRα expression plasmid was co-transfected with constructs containing different lengths of OTUB1 promoter (-1000/+1000, +339/+1000, +485/+1000, +658/+1000, +900/+1000) cloned in a luciferase reporter plasmid into HCT116 cells for 48 h. The cells were then lysed and assayed for luciferase activity. Data were normalized to Renilla activity. (B) Diagram of the OTUB1 locus showing ERRE-S1~4 in the promoter and the mutation sequences. (C) An empty vector or ERRα expression plasmid was co-transfected with wild-type or mutated OTUB1-luciferase constructs into HCT116 cells for 48 h. The luciferase activity was then assayed. Data were normalized to Renilla activity. The data represent the mean of three independent experiments, and the error bars represent the SD. **, P < 0.01; ***, P < 0.001.