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Fig 2 | Molecular Cancer

Fig 2

From: CircRNA: functions and properties of a novel potential biomarker for cancer

Fig 2

Biosynthesis of circular RNAs from introns. a. Circular RNA from group I introns. First, an exogenous guanosine(G) attacks the 5′-terminus of the intron as nucleophile. The 5′-exon is cut off due to the transesterification. Second, the 3′-hydroxyl of the free exon attacks the 5′-terminus of the 3′-exon as nucleophile, producing a linear intron. Third, a 2′-hydroxyl close to the 3′-terminus of the linear intron attacks a phosphodiester bond close to the 5′-terminus, producing an RNA lariat circularized with 2′,5′-phosphodiester and releasing the 5′-terminal sequence. Finally, the 3′- tail of the RNA lariat is removed. b. Circular RNA from group II introns. First, the RNA precursor releases the 3′-exon. Finally, the 2′-hydroxyl of the 3′-terminus attacks the 5′-terminus of the intron, producing an circular RNA circularized with 2′,5′-phosphodiester. c. Circular intron RNA(ciRNA). First, a pre-mRNA is spliced by a spliceosome, producing an RNA lariat circularized with 2′,5′-phosphodiester. Finally, the 3′- tail of the RNA lariat is removed

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