Insertion of spliceosomal introns in proto‐splice sites: the case of secretory signal peptides

Analysis of the exon-intron structures of 2208 human genes has revealed that there is a statistically highly significant excess of phase 1 introns in the vicinity of the signal peptide cleavage sites. It is suggested that amino acid sequences surrounding signal peptide cleavage sites are significantly enriched in phase 1 proto-splice sites and this has favored insertion of spliceosomal introns in these sites.