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. Author manuscript; available in PMC: 2022 Sep 7.
Published in final edited form as: Cell Metab. 2021 Sep 7;33(9):1744–1762. doi: 10.1016/j.cmet.2021.08.006

Figure 2. miRNA biogenesis.

Figure 2.

Pri-miRNAs are hairpin-shaped precursor miRNA molecules transcribed by either RNA polymerase II (RNAPII) from independent genes or introns of protein-coding genes. The pri-miRNAs are cleaved by Drosha/DGCR8 into pre-miRNA and exported to the cytoplasm from the nuclei mediated by Exportin 5 (XPO5) binding. Dicer cleavage generates an miRNA duplex intermediate. Trans-activation-responsive RNA-binding protein (TRBP) and Argonaute (AGO) protein assemble into the RNA-induced silencing complex (RISC). One miRNA strand is transferred to AGO protein, resulting in the formation of RISC. AGO2 binds to one of the miRNA strands to form the mature miRNA, which will be selectively incorporated into exosomes. After miRNA maturation, the RNA-binding protein YBX1 also sorts miRNAs into exosomes.