Fig. 3.
Tracts capable of self-base-pairing splice exon 9 more efficiently. (A)Replacing the TG tract with dinucleotide repeats of different composition resulted in an inverse correlation between the ability to self-pair and exon 9 skipping. (CG)12 and (TA)12 tracts showed a level of skipping intermediate between (TG)12 and random sequences, whereas (CA)12 and A24 tracts skipped exon 9 100% of the time. The fact that sequences capable of intratract base-pairing spliced more efficiently than those which were not suggested a role for RNA secondary structure in the influence of these sequences on splicing. (B) Effect of replacing (TG)12 with artificial, thermostable hairpin elements of the same length as (TG)12. (TG)12 is shown for reference. Two artificially created hairpins, pin 1 and pin 2, contained the loop-forming motif TTCG flanked by randomized but complementary sequences (see Table 1 for sequences). (TG)5-TTCG-(TG)5 was generated by a 2-bp mutation in the (TG)12 construct.