FIGURE 2.

Schematic diagram of circRNA synthesis in vivo and in vitro. (A) EcircRNAs are the major circRNAs and are mainly produced by a process called backsplicing in vivo. EIciRNAs and ciRNAs are produced by other cyclization reactions and located in the nucleus. EcircRNAs are mainly located in the cytoplasm and have various functions. In the cytosol, circRNAs can act as miRNA sponges, protein sponges, protein scaffolds, translation templates, and regulators of mRNA. (B) Linear RNA precursor is produced from in vitro transcription, and researchers have developed several methods for linear RNA precursor ligation to synthesize circRNA in vitro.