FIG. 7.

Proposed model for IR alternative splicing regulation by SRp20 and CUG-BP1. (A) Predicted secondary structure of exon 11 (uppercase letters) and intron 10 (lowercase letters) RNA is shown. A 180-nt region of the pre-mRNA including the 3′ end of intron 10, exon 11, and the 5′ splice site of intron 11 was folded using the M-fold server (50). The CUG-BP1 binding site is indicated in red, SRp20 in green, SF2/ASF in yellow, and the pY tract and 3′splice site in purple. (B) Mutations in the RNA secondary structure. The exon sequence is shown in uppercase letters. Stabilizing mutations are shown above the sequence and destabilizing mutations below the sequence. Exon 11 inclusion is given on the right. (C) Proposed model for stabilization of RNA secondary structure by CUG-BP1 and its antagonism by SRp20 and SF2/ASF, allowing splice site recognition by the U1 and U2 snRNPs. Exon 11 is shown in sky blue.