Figure 3. Alternative exons have lower H3K36me3 signal than constitutive exons.

(a-e) Mean log₂ ChIP signal of each C. elegans trio exon (a-c) or the average tag count for each mouse trio exon (d, e) is shown for the indicated histone modification. (f) Cartoon of alternative and constitutive trios of exons used in the analysis; colours correspond to data bars in (a-e). Exon sizes in alternative and constitutive sets were length matched. In (a) and (d) the alternative central exons (red) have significantly lower H3K36me3 signal than their matched constitutive central exons or than their constitutive neighbours (p<0.01). The matched central exons do not show reduced H3K36me3 relative to their neighbours. There is also no significant difference in signals for the alternative exons compared to the matched exons for other histone modifications. The higher signals for exon 1 in (b) and (e) are due to closer proximity to the TSS. For C. elegans trios, n=54, and for mouse n=190. Bars are 95% confidence intervals. (g, h) Cumulative GC content of constitutive and alternative exons in the alternative trios. (g) C. elegans (h) mouse. Alternative exons are similar in GC content to constitutive exons.