The increase in exon skipping correlates with the proportion of U’s and the proximity of the first U-rich motif to the exon–intron boundary. Spearman correlation tests showing significant correlations between the increase in exon skipping upon TIA1/TIAL1 silencing and proportion of U’s within the first 30 nt of the second intron of the splicing cassettes (A), and the proximity of the first U-rich motif to the exon–intron boundary (B). The correlations suggest that exons followed by extended TIA1/TIAL1 binding sites (longer stretches of U’s) and/or by binding sites that are located closer to the 5′ splice sites are more sensitive to the reduced levels of TIA1/TIAL1. EIB, exon–intron boundary; n = 27 alternative splicing cassettes.
