IAS2 represses the IIIc exon in epithelial cells. (A) Schematic of single-exon minigene constructs used to study the inclusion of exon IIIb and the repression of exon IIIc in DT3 cells. The presence or absence of IAS2 and ISAR is indicated. The IIIb minigenes can direct the expression of two RNAs produced by alternative splicing: skipping of IIIb leads to the U-D RNA and the inclusion of IIIb leads to the U-IIIb-D RNA. The IIIc minigenes can direct the expression of two RNAs produced by alternative splicing: skipping of IIIc leads to the U-D RNA and the inclusion of IIIc leads to the U-IIIc-D. (B) DT3 cells were transfected with the minigene constructs in A, and total RNA was extracted and analyzed with either the Invader RNA assay (gray bars) or semiquantitative RT-PCR (white bars) for the presence of the RNA variants. Error bars represent one standard deviation. In B the percent inclusion of a product (e.g., U-IIIb-D) among transcripts was calculated as follows: percent product (e.g., U-IIIb-D) inclusion = {[product (e.g., U-IIIb-D)]/([U-D] + [U-IIIb-D])} × 100.
