PTBP1 enhances AS of Axl exon 10 through its interaction with upstream intron 9 sequences. (A) The primer position used to detect the binding segment of PTBP1 and Axl pre-mRNA in the CLRIP experiment. The CLRIP assay was used to detect the binding segments of endogenous (B) and exogenous (C) PTBP1 to Axl pre-mRNA. "T" means Cytoplasmic and Nuclear lysate, "C" means Cytoplasmic lysate, "N" means Nuclear lysate. (D) The RNA fragment sequence used in the RNA pulldown assay and its position in the Axl pre-mRNA, the red font represents the mutated base. (E) RNA pulldown assay was used to detect the binding of PTBP1 to the biotinylated RNA fragments. (F) The mutated sequence of the Axl-minigene site-directed mutagenesis and its position in the Axl pre-mRNA, the red font is the mutated base. (G) RT-PCR was used to detect the effect of PTBP1 over-expression on the expression of Axl-S and Axl-L isoforms in different groups of HepG2 cells. Data are presented as mean ± S.D. (N=3), one-way ANOVA followed by Tukey's post-hoc test was performed for statistical analysis. The “*, ***” indicate “P<0.05, 0.001” versus the control group, respectively. The “###” indicates “P<0.001” versus the “PTBP1+WT” group.