Mechanisms of miRNA-Mediated Gene Regulation from Common Downregulation to mRNA-Specific Upregulation

Figure 2

miRNA-mediated upregulation according to cell cycle phase. miR-334 and miR-27a bind to the 3′UTR of KLF4 and Myt1 mRNA in proliferating and cancerous cells and subsequently downregulate mRNA expression by both translational inhibition and mRNA degradation. miRNP-mediated repression requires factors including AGO, GW182, deadenylases, and nucleases. However, in G0 cells and immature oocytes, GW182 is downregulated and FXR1 is associated with AGO2 bearing miRNP and leads to gene expression upregulation. miR-206 is associated with KLF4 mRNA in G0 cells and xmiR-16 is associated with Myt1 mRNA in immature Xenopus oocyte. miR-206 and xmiR-16 activate KLF4 and Myt1 expression, respectively, by binding to their 3′UTRs and recruiting special factors such as FXR1, since AGO2 is associated with gene expression activation in these cells and lacks slicer activity.