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. 2022 Apr 27;23(9):4855. doi: 10.3390/ijms23094855

Figure 1.

Figure 1

Biogenesis of miRNAs. The initiation process is started in the nucleus by RNA polymerase II which transcribes protein-coding genes into pri-miRNAs with a large cap and polyadenylation. The pri-miRNAs are processed by a complex of Drosha and RNA-binding protein DGCR8 to produce the stem-looped structures of 59–89 nucleotides (nt) known as pre-miRNAs. Then, pre-miRNAs are transported into the cytoplasm by exportin-5/Ran-GTP, and further processing occurs to generate mature miRNAs where Dicer cleaves stem-looped structures into double-strand miRNAs. One functional miRNA strand (red) is loaded with Ago2 into the RISC, and that complex, miRISC, binds to the complementary sequences of target mRNA in the 3′UTR. The result of these interactions is degradation and suppression of translation of the specific mRNA. pri-miRNAs, primary miRNAs; pre-miRNAs, processor miRNA; Dicer, RNase III nuclease; RISC, RNA-induced silencing complex; Ago2, and Argonaute 2. The image is adapted from Strubberg and Madison [18].