Figure 3.

The presence of multiple intronic repeats allows a variety of mature RNAs to be generated from a single gene. (A) Schematic of a 4-exon gene, with intronic repeat elements depicted as red arrows. Depending on which repeats base pair to one another (denoted by blue arcs), distinct mature RNAs are produced. (B) If the repeats flanking exon 2 base pair to one another, backsplicing (denoted in purple) is induced and a circular RNA composed of exon 2 is generated. (C) If, however, the repeats in the second intron base pair to one another, canonical splicing occurs and a linear mRNA is produced. (D) If the repeats flanking exon 3 base pair to one another, a circular RNA composed of exon 3 is generated. Finally, base pairing between the first and last repeats would yield a circular RNA composed of exons 2 and 3 (not shown).