Figure 2.

Functional summary of circRNAs. (A) Transcriptional regulation: In the nucleus, EIciRNA and ciRNA can regulate transcription by directly interacting with RNA polymerase II and U1 snRNP. (B) miRNA molecular sponging: ecircRNA that contains miRNA-binding sites can block the binding between miRNA and its target mRNA and prevent the inhibitory effect of miRNA on the target protein. (C) Regulation of translation: circRNAs contain an internal ribosome entry site, which can bind to the ribosome to regulate translation. (D) RBP sponging: circRNAs with an RBP-binding site can act as a protein sponge, thereby regulating protein activity. (E) circRNAs may function as protein scaffold. circRNA, circular RNA; RBP; RNA-binding protein; ecircRNA, exonic circular RNA; ciRNA, circular intronic RNA; EIciRNA, exon-intron circular RNA.