Fig. 1. Canonical miRNA biogenesis and generation of the functionally active miRISC complex. AAAA_n — poly(A) tails at the 3' ends of the mRNA and miRNA molecules; DGCR8 — DiGeorge syndrome critical region 8; Dicer, Drosha — RNase III family endoribonucleases; miRISC — RNA-induced silencing complex bound to the miRNA strand; Ran — Ras-related nuclear protein (GTP-binding nuclear protein); RISC — RNA-induced silencing complex; XPO5 — exportin-5; pre-miRNA — miRNA precursor. The 5' cap is marked with gray circle in the primary miRNA image

Fig. 2. Reported mechanisms underlying miRNA-mediated silencing. А. Inhibition of the target mRNA “closed-loop” formation. Under exposure to the RISC complex, PABPC dissociates from the target mRNA poly(A) tail, making it impossible to interact with eIF4G and preventing formation of the “closed-loop” essential for initiation of mRNA translation. B. Target mRNA decay (on the left) and inhibition of mRNA translation initiation through prevention of the eukaryotic translation initiation factor 4F complex assembly (on the right). Target mRNA is marked with black line; the GW182 protein representing a scaffold for proteins CCR4-NOT and PAN2-PAN3 is marked with yellow line; the guide strand of miRNA being part of the miRISC complex is marked with light-blue line. Gray arrows point to engagement of the CCR4-NOT complex by the AGO proteins with subsequent recruitment of the DCP1 and DCP2 decapping proteins by the CCR4-NOT complex. Modified from [17]