Dicers at RISC: The Mechanism of RNAi

The pathway of RNA interference starts when Dicer cuts dsRNA into small interfering RNAs (siRNAs) that subsequently target homologous mRNAs for destruction. microRNA processing from stem loop precursors similarly requires Dicer activity. Two papers in this issue of Cell now demonstrate that Dicer is also essential for the execution phase of RNAi and explore the distinct requirements for Dicers in the siRNA and miRNA pathways.