SAP155 siRNA interfered with FIR mRNA splicing. (a) SAP155 siRNA interfered with endogenous FIR pre‐mRNA splicing. (b) Constructs of FIR splicing variants are shown. Each FIR splicing variant was extracted from the DNA gel, subcloned into a suitable plasmid, and DNA sequenced. Scheme of each FIR splicing variant is shown. SAP155 siRNA induced the alternative splicing of FIR‐pre mRNA. (c) FIR splicing variant, Δ3, mRNA was increased by SAP155 siRNA in HeLa, RKO, DLD1 and HCT116 cells.