Figure 2

Expression of PTBP1 and its involvement in AXL regulation. (A) Identification of the PTBP1-binding region of AXL 5′-UTR. Luciferase reporter vectors pMIR-Report-AXL 5′-UTR (intact, lane 2) or pMIR-Report-AXL 5′-UTR (deletion mutants, lanes 3 and 4) were transfected into CL1-0 cells, and luciferase activity was measured 24 h later. (B) Inverse correlation between endogenous levels of AXL and PTBP1 proteins in the low invasive CL1-0 cells and the highly invasive CL1-5 and A549 cells. (C,D) Endogenous AXL mRNA and protein levels were up- and down-regulated by PTBP1 siRNA and PTBP1, respectively. In these experiments, A549 cells were transfected with PTBP1 siRNA and CL1-5 cells were transfected with PTBP1 or PTBP2. Expression levels of AXL mRNA and protein were measured, respectively, by quantitative real-time RT-PCR and Western blot 48 h after transfection. Actin was used as the internal control. The values were derived from three independent experiments. Error bars represent SD. *P < 0.05.