3′-splice-site switching by SXL. (Top) Schematics of the sex-specific alternative splicing of the wild-type pre-mRNA substrate. The boxes represent exons, and the lines represent introns. The alternative 3′-splice sites (NSS and FS), the NSS Py tract (SXL-binding site), and the translation stop codon (STOP) are shown. (Bottom) SXL-mediated splice-site switching for the wild-type (M-tra), and the U1,3,5C and U2,4C mutants (underlined) of the NSS Py tract of tra. Precursor RNAs were spliced in an HeLa nuclear extract in the absence (−) or presence of different concentrations of GST–SXL (0.08 μM, 0.25 μM, 0.76 μM, and 2.3 μM), and the spliced products were analyzed by primer extension assay using radiolabeled NSS or FS splice junction primers indicated by the arrows.
