Fig. 3

In this figure, exons are represented by rectangles in different colors, and introns are represented by black lines. Five biological functions of circRNAs are proposed: a As an RNA binding protein (RBP) sponge. To regulate the function of RBPs, some circRNAs can interact with RBPs, such as Argonaute, polymerase II, myosin, and so on. b As a miRNA sponge. Some circRNA and miRNA binding sites are conserved. By combining with miRNAs competitively, these circRNAs can block binding between the target and the miRNAs. miRNA inhibition of target protein translation. c Regulation of parental gene transcription. The biogenesis of circRNAs is generally associated with the transcription of its parental genes. Therefore, circRNA can competitively affect the biogenesis and processing of mRNA. d Rolling circle translation. Some circRNAs contain internal ribosome entry sites, which can be combined with ribosomes. These circRNAs can encode proteins. e To affect alternative splicing. CircRNA biogenesis can compete with previous mRNA splicing, resulting in reduced linear mRNA [98]