Fig. 2

Functions of circRNAs. a CircRNAs are formed from pre-mRNAs and have endogenous effects on linear RNA transcription. This effect can be promoting or suppressing the transcription of linear RNAs. b CircRNAs bind to RBPs to influence mRNA transcriptional levels. c EIciRNAs can enhance gene transcription via interacting with U1 snRNP and RNA polymerase II in the promoter region of the host gene. d CircRNAs function as miRNA sponges to bind to miRNAs and inhibit target mRNAs degradation. e circMbl can interact with MBL, and act as a negative feedback regulation between MBL and circMbl production. When MBL is in excess, it binds to the mbl pre-mRNA and causes it to backsplice into circMbl. When MBL protein concentration are reduced due to MBL binding to circMb1, the production of circMbl is reduced. f CircRNAs containing an open reading frame (ORF) driven by the IRES can translate a functional protein. g CircRNAs function as mRNA trap to influence mRNA splicing and protein translation