FIG. 1.

Schematic representations of various minigenes. (A) The parent RK3 minigene with the Rous sarcoma virus long terminal repeat promoter (RSV) and the bovine growth hormone polyadenylation signal (BGH). Between the two are the constitutive exons C1 and C2 and the alternative exons K-SAM and BEK. Positions of primers used for RT-PCR are shown. Possible splicing patterns are shown, together with corresponding RNAs. (B) Structures of modified K-SAM exons found in other minigenes in the RK3 framework. ESS are stippled. Part of the CAT sequence is shown, and ESS sequences used to replace CAT sequences are underlined. Point mutations within the K-SAM exon ESS in RK12-S6A and -S6G are marked by asterisks. EcoRI and SalI sites used to remove fragments for in vitro transcription are marked.