Fig. 1.

Gene silencing using siRNA or miRNA mimics. Once the siRNA or miRNA mimic has been introduced into the cytoplasm of the cell, it is unwound and the active antisense strand (green) is incorporated into the RISC. This leads to gene silencing via two distinct mechanisms, depending on the extent of base pairing between the antisense strand and the target mRNA. With siRNA on the left, the complete homology between the antisense and target mRNA (yellow) leads to site-specific cleavage and degradation of the mRNA. In contrast, the partial sequence identity between the active miRNA strand and its mRNA target leads to inhibition of translation, decapping, and subsequent mRNA degradation