Figure 4

Roles of Argonaute proteins in gene silencing guided by small RNAs. Ago proteins can bind (a) siRNAs derived from long double-stranded precursor RNAs or (b) miRNAs derived from endogenous hairpin structures. On binding with perfect complementarity to a target mRNA, the Ago-siRNA or Ago-miRNA complex induces its cleavage and degradation (left). An Ago-miRNA complex binding imperfectly to the 3' UTR of the target mRNA induces translational inhibition (middle), or deadenylation and subsequent decapping and degradation of the target mRNA (right). m⁷G, 7-methylguanine.