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. 2019 Oct 6;20(19):4940. doi: 10.3390/ijms20194940

Figure 1.

Figure 1

MicroRNA biogenesis and modulation of miRNA activity. miRNA genes are transcribed to produce primary miRNA transcripts (pri-miRNA) by RNA polymerase II. Drosha–DGCR8 complex cleaves the pri-miRNA into a precursor miRNA transcript (pre-miRNA) which is then transported from the nucleus into the cytoplasm via nuclear pore by exportin 5. In the cytoplasm, the pre-miRNA is further modified by the DICER and TRBP complex to form a mature miRNA duplex. The miRNA duplex is incorporated into an Argonaute (Ago) with RNA-induced silencing complex (RISC) and the duplex is unwound by helicase into two single-stranded miRNAs. The mature single-stranded miRNA can then bind to the target mRNA and exert its inhibitory function through translational block or degradation of the mRNA depending on the level of nucleotide complementarity. Reproduced with permission from Bhardwaj, A.; Singh, S.; Singh, A.P. MicroRNA-based cancer therapeutics: Big hope from small RNAs. Mol. Cell Pharmacol. 2010 [26].