Figures (1)  Tables (0)

    • Figure 1. 

      AGO1-centered regulatory framework governing the dynamics of miRNA's stability. During assembly of the RISC, AGO1 recognizes the 5' terminal nucleotide of miRNAs and sequesters both ends of the miRNA molecule, thereby shielding them from exonucleolytic degradation. Upon target recognition, AGO1 recruits HESO1 and URT1 to uridylate and degrade RISC-cleaved mRNA fragments. The HEN1-catalyzed 3'-end methylation of miRNAs is critical to block mis-uridylation by HESO1/URT1 and 3'-to-5' trimming activities. However, dysfunction of HEN1 or nibbling by SDNs leads to unmethylated miRNAs, which further results subsequent miRNA 3'-end tailing and trimming (pTDTT). Target RNA pairing with a central bulge abrogates the endonuclease activity of AGO1 and induces a conformational change in the protein. This altered state is recognized by HWS, which, in turn, triggers degradation of the AGO1-miRNA-bulged target ternary complex (pTDMD). The figure was created with BioGDPcom[50]. RISC, RNA-induced silencing complex; pTDTT, target-directed miRNA tailing and trimming in plants; pTDMD, target mimicry-directed miRNA degradation in plants.