Fig. 2

Three models for the biogenesis of ecircRNAs. a. Lariat-driven circularization, also known as the exon-skipping model. The remaining exons in the pre-mRNAs were allocated into the concomitant linear mRNAs. b. Intronic base pairing-driven circularization. The pairing across complement sequences in the flanking introns brought the splicing sites into proximity, facilitating the circularization of intervening exons. c. RBP-driven circularization. The interactions of RBPs binding to the flanking introns serve as a bridge to bring the introns into proximity, promoting the process of circularization. d, e. Some RBPs could bind to the intronic dsRNA to regulate the biogenesis of ecircRNAs. While some RBPs (such as NF90/NF110) stabilize the dsRNAs to promote the generation of ecircRNAs (d), some RBPs (such as DHX9 and ADAR1) destroy the stability of dsRNAs to suppress the generation of ecircRNAs (e)