What is RNA interference (RNAi)?
RNA interference (RNAi) is a mechanism of gene silencing occurring in a broad range of eukaryotic organisms. This process involves the digestion of cytoplasmic double-stranded RNA (dsRNA) into smaller fragments of a defined length. Dicer, a cytoplasmic RNase present in eukaryotic cells, catalyzes this ATP-dependent reaction, generating 21-25 nt dsRNA molecules with phosphorylated 5 ends, and 3 dinucleotide overhangs carrying an intact hydroxyl group. Dicer chops dsRNA into two types of smaller RNA microRNA (miRNA) and small interfering RNA (siRNA). The guide strand of these small RNA molecules couple to a protein complex called RISC (RNA-induced silencing complex), which then catalyzes the mRNA-specific gene silencing event (RNA interference or gene knock down). This occurs via one of two mechanisms. RISC-siRNA complexes induce sequence-specific mRNA degradation. In contrast, RISC-miRNA complexes lead to the sequence-specific inhibition of mRNA translation. Endogenously expressed siRNA
