Unexpected selection to retain high GC content and splicing enhancers within exons of multiexonic lncRNA loci

(A) Comparison of hexamer scores (as per Fairbrother et al. 2002) between human protein-coding and lncRNA exons. Red dots represent the ESEs previously identified by Fairbrother et al. (2002). Red and blue areas contain motifs that are enriched within exons or within introns, respectively, of both protein-coding and lncRNAs (ESEscore > |2.5|, Fairbrother et al. 2002). (B) Proportion of hexamers that are ESEs (Fairbrother et al. 2002; Zhang and Chasin 2004; Goren et al. 2006) at the 5′ and 3′ exon–intron boundaries within human protein-coding (blue), multiexonic lncRNAs (red), and monoexonic lncRNA (green) loci.