AP-1 regulates PTPROt promoter in K562 cells. K562 cells were transfected with either pGL3-basic or PTPt-P-luc (PTPROt promoter region from −1040 to +261 with respect to transcription start site cloned upstream of firefly luciferase in pGL3-basic⁵ ) in combination with expression vectors for c-fos, c-jun, or both. Luciferase activity was measured using a dual luciferase assay kit. (A) Normalized promoter activity (firefly/Renilla) is represented as fold change over the activity in the absence of c-fos and c-jun. (B) Overexpression of c-fos and c-jun was confirmed by Western blot analysis. K562 cells were transfected with pGL3-basic or PTPt-P-Luc along with control or c-jun–specific siRNA. Luciferase activity was measured using a dual luciferase assay kit. (C) Normalized promoter activity (firefly/Renilla) is represented as fold change in c-jun siRNA-transfected cells over control siRNA-transfected cells. (D) Knockdown of c-jun was confirmed by Western blot analysis. Each experiment was performed with 5 replicates and repeated twice. Error bars represent SD. P values were calculated using the Student t test.