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. 2020 Apr 16;57(1):67–79. doi: 10.3892/ijo.2020.5049

Figure 1.

Figure 1

Figure 1

Figure 1

Mechanism of circRNA formation. circRNAs are formed via reverse splicing and include three main types, namely ecircRNA (exons only), ciRNA (introns only), and EIciRNA (introns inserted between two exons). (A) In pre-mRNA transcripts, non-adjacent exons close to each other can form lariat intermediates, and ecircRNA or EIciRNA may form via exon skipping. (B) Pre-mRNA is processed into mature mRNA by splicing, and ecircRNA forms via reverse splicing and cyclization. ecircRNA is transferred from the nucleus to the cytoplasm, where it exerts its function. (C) ciRNA is formed by a lariat intermediate containing exons. circRNA, circular RNA.