Fig. 2.

Functions of CirxRNAs. A: Regulating transcription. CiRNAs which mainly located in the nucleus can bind to RNA polymerase II at the promoters of their host genes to enhance gene expression. B :Regulating alternative splicing. Circularization and splicing compete against each other, the formation of circRNAs impact the alternative splicing of pre-mRNAs, eventually giving rise to alteration of gene expression. C: Regulating transcription. EIciRNAs can interact with U1 snRNP and then the EIciRNAs-U1 snRNP complexes associate with RNA polymerase II (Pol II) at the promoters of their host genes to enhance gene expression. D: Acting as sponges. EcircRNAs can bind to miRNAs and proteins to regulate gene expression. E: Translating into proteins. Some ecircRNAs can be encoded to proteins, thereby influence their downstreams