FIG. 3.

Two AU-rich sequence elements flanking exon 23a are important for regulated splicing of NF1 exon 23a. (a) A diagram indicating mutated AU-rich sequences in the reporter. nt, nucleotides. (b) Left, the wild-type or mutant (mut) reporters were cotransfected with empty vector or mHuC cDNA in HeLa cells. Inclusion of exon 23a from the NF1 pre-mRNA was detected by RT-PCR. A Western blot showing expression of the Xpress-tagged mHuC is included. U170K protein is shown as a loading control for the Western blot analysis. Right, the wild-type or mutant reporters were transfected into CA77 cells. Error bars indicate standard deviations. dn, down; dl, double.