Differential GC Content between Exons and Introns Establishes Distinct Strategies of Splice-Site Recognition

摘要

SummaryDuring evolution segments of homeothermic genomes underwent a GC content increase. Our analyses reveal that two exon-intron architectures have evolved from an ancestral state of low GC content exons flanked by short introns with a lower GC content. One group underwent a GC content elevation that abolished the differential exon-intron GC content, with introns remaining short. The other group retained the overall low GC content as well as the differential exon-intron GC content, and is associated with longer introns. We show that differential exon-intron GC content regulates exon inclusion level in this group, in which disease-associated mutations often lead to exon skipping. This group's exons also display higher nucleosome occupancy compared to flanking introns and exons of the other group, thus “marking” them for spliceosomal recognition. Collectively, our results reveal that differential exon-intron GC content is a previously unidentified determinant of exon selection and argue that the two GC content architectures reflect the two mechanisms by which splicing signals are recognized: exon definition and intron definition.Graphical AbstractFigure optionsView in workspaceDownload full-size imageDownload as PowerPoint slideHighlights? Splicing unit recognition evolved in accordance with GC content architecture ? Exon-intron differential GC content is a determinant of exon selection ? These exons are epigenetically “marked” by nucleosomes ? Disease-associated mutations lead to exon skipping, arguably via exon definition.