Figure 3. Exon 6B is derived from an intronic Alu element.

(A) Alignment of SMN intron 6 region spanning exon 6B. Numbering starts from the beginning of intron 6. Exon 6B and putative binding sites for hnRNP C are highlighted in grey and green, respectively. Black arrows indicate splice site (ss) positions and red arrow indicates position and direction of Alu insertion. AluY sequences (reverse and complement) are obtained from Dfam (Accession: DF0000002). (B) Genomic view of RNA-Seq of HeLa cells with and without hnRNP C depletion as previously described by Zarnack et al.³⁵. Exon positions are shown at the bottom. (C) Estimated exon inclusion for all internal exons of SMN based on sequencing data from (B). Error bars represent standard error of 4 sequencing libraries. Statistical significance: **p < 0.01.