Fig. 5.

Putative interactions and sequence properties of flanking introns. a Scheme indicating the relevant regions (red) of introns flanking circularized exons (yellow). b Screen of sequence complementarity using BLAST. The scores for circular and linear control intron pairs largely overlap. c Screen of intron interactions represented by the MFE of constrained RNAcofold calculations. The difference between both groups is significant. Still there is some overlap. d Relation of GC-content and MFEs. Both measures appear to be linked (correlation ρ=0.5, Spearman’s rank correlation). e Screen of GC-content. A significant increase is found compared to the control. f Screen of CpG dinucleotides. A significant increase is found compared to the control which rarely exhibits CpG. g Screen of cytosine-content. A significant increase is found compared to the control. It explains the observed effects for GC-content and CpG frequency. h Screen of average base methylation. The number of methylated bases in introns flanking circRNAs is slightly but significantly increased compared to linear control introns. *p-value <0.001