Figure 6. SR proteins mediate associations of exons 22, 23 and 24.

Biotinylated and non-biotinylated dystrophin exons labeled with ³²P-ATP (sense exons) or ³²P-UTP (antisense exons), were mixed with purified SR proteins. Following incubation, biotinylated RNAs were purified with streptavidin magnetic beads and the formation of RNA complexes was analyzed on 10% denaturing polyacrylamide gel. Asterisks and A indicate biotinylated and antisense exons respectively. Lanes 1 and 2, showing the relative migration of exons 22, 23 and 24, contain one-fourth of the RNA inputs assayed in lanes 8–11 and 13–14 respectively. Lane 15 and 16 contain one-fourth of the supernatants collected from reactions loaded in lanes 13–14. Background levels, probably generated by non-specific trapping of RNA or RNA/protein complexes into the magnetic beads, are shown in lanes 3, 4, and 12 and 17 respectively. Comparable results were obtained in three independent experiments.