Figure 1.

Biogenesis of circular RNAs. A signature, 7-nt GU rich motif near the 5′ splice site and an 11-nt C-rich motif at the branchpoint site, is critical for RNA lariats to escape debranching, thereby generating ciRNAs and ecircRNAs (after another backsplicing step). Backsplicing occurs in the presence of flanking inverted repeat elements (e.g., Alu elements) and/or with the aid of RNA-binding proteins (RBP). EIciRNAs and ecircRNA are both circRNAs, which require backsplicing in biogenesis. SA, splicing acceptor. SD, splicing donor. BP, branching point. BSJ, backsplice joint. Colored boxes depict exons. Black lines depict introns.