Figure 2.

Multiple functions of circRNAs. (A) A subset of circRNAs are involved in protein coding. Protein coding by circRNAs is also possible with an IRES. (B) A majority of circRNAs function as miRNA sponges that interact with miRNA-Ago2 (representative protein) complexes to suppress the functions of miRNAs. (C) circRNAs bind with RBPs to form RNA-protein complexes, thus affecting their functions and translocation. (D) For transcriptional regulation, elcircRNAs and ciRNAs induce the transcription of parental genes by binding transcription complexes to the host promoters. circRNA, circular RNA; IRES, internal ribosome entry site; miRNA, microRNA; Ago2, argonaute 2; RBP, RNA-binding protein; elciRNA, exon-intron circRNA; ciRNA, circular intronic RNA; ecircRNA, exonic circRNA; snRNP, small nuclear ribonucleoprotein; Pol II, RNA polymerase II.