Fig. 3

A, RT-PCR products from the synthetic splicing system containing a chimeric exon. B, Schematic representations of the chimeric exon cloned into the pSPL3 vector (top) and the three different resulting RT-PCR products. The wild-type sequence is above the line, and the mutant sequence is below. 1, Full length transcript containing the vector-supplied exon 1 (V1), the vector-supplied terminal exon (Vt) of the splicing vector pSPL3, and the full sequence of the chimeric exon. 2, The product of the vector-supplied first and terminal exons spliced to a smaller fragment of the chimeric exon. The arrow indicates the position of the cryptic splice site used to generate the truncated transcript. 3, Transcript containing only V1 and Vt. M = 100 bp marker, WT = vector with chimeric exon containing wild-type splice donor sequence, Mut = vector with chimeric exon containing mutant splice donor sequence. Mut1 and Mut2 are from duplicate transfections of the mutant version of the construct.