FIG. 4.

TIA-1/TIAR proteins promote inclusion of exon 23a. (a) Overexpression of TIAR in HeLa cells increases exon 23a inclusion. HeLa cells were cotransfected with the wild-type (left panel) or mutant (see Fig. 3a for mutant sequence) (middle panel) NF1 reporter construct and increasing amounts (0.5 and 1 μg) of TIAR. RT-PCR was carried out using total RNA isolated from the transfected cells and the oligonucleotides indicated in the diagram in Fig. 1. The percentage of NF1 exon 23a inclusion is displayed in the bar graphs. The expression of transfected TIAR was verified by Western blot analysis. Overexpression of TIAR in CA77 cells increases exon 23a inclusion (right panel). (b) siRNA knockdown of TIA-1 and TIAR in HeLa cells reduces inclusion of exon 23a. HeLa cells were transfected with a control siRNA (250 pmol), an siRNA against TIA-1 (125 pmol TIA-1 plus 125 pmol control siRNA), an siRNA against TIAR (125 pmol TIAR plus 125 pmol control siRNA), or siRNAs against both TIA-1 and TIAR (125 pmol TIA-1 plus 125 pmol TIAR siRNA). Results of RT-PCR and Western blot analysis are shown. U170K protein served as a loading control for the Western blot analysis. WT, wild type. Error bars indicate standard deviations.