FIGURE 7.

Effect of β-catenin/TCF4 transcriptional activity on alternative splicing of pG11. DLD-1 cells were co-transfected with the PTB-derived minigene pG11 and βCat-CA, empty pEGFP vector, or TCF-DN as indicated. The alternative exon 11-containing transcripts were specifically amplified by RT-PCR, and band intensities were quantified by densitometry using amplified Pol II levels as internal control. The stimulating effect of βCat-CA on exon 11 inclusion was further analyzed in cells previously transfected with either control or one of two SRp20-specific small interfering RNAs. Below the RT-PCR gel, a Western blot shows the degree of depletion of the endogenous SRp20 protein. Note that depletion of SRp20 prevented PTB exon 11 inclusion even in the presence of βCat-CA .