Figure 1.

Schematic diagram of the classification of circRNAs. According to the biogenesis characteristics from genomic regions, circRNAs are often divided into four types as follows: (A) ecircRNA (Lasso-driven cyclization); (B) IciRNAs (individual introns form rings directly); (C) ciRNA (introns are cyclized by base complementary pairing); and (D) EIcircRNAs (cyclization mediated by RBPs and trans-acting factors). circRNA, circular RNA; ciRNA, intronic circRNA; ecircRNA, exonic circRNA; EIcircRNAs, exonic-intron circRNAs; IciRNAs, intergenic circRNAs; RBP, RNA binding protein.