Figure 1.

Schematic diagram showing the proposed models of circular RNA (circRNA) biogenesis

(A) Transfer RNA splicing-driven circularization. (B) Intron-pairing-driven circularization. Intron pairing brings the corresponding splice signals close to each other to facilitate cyclization. (C) Lariat-driven circularization. Exon skipping results in the production of a mature linear mRNA and an intron lariat containing the middle exon. This lariat is re-spliced to generate a mature circular RNA and a double lariat structure, which subsequently undergoes debranching and degradation. (D) RNA-binding protein (RBP)-driven circularization. RBPs bring the corresponding splice signals close to each other to facilitate cyclization. (E) Small nuclear ribonucleoprotein-dependent circularization. (F) Ribosomal RNA splicing-driven circularization.