Targeted mRNA degradation by double-stranded RNA in vitro

Double-stranded RNA (dsRNA) directs gene-specific, post-transcriptional sil encing in many organisms, including vertebrates, and has provided a new too l for studying gene function. The biochemical mechanisms underlying this ds RNA interference (RNAi) are unknown. Here we report the development of a ce ll-free system from syncytial blastoderm Drosophila embryos that recapitula tes many of the features of RNAi. The interference observed in this reactio n is sequence specific, is promoted by dsRNA but not single-stranded RNA, f unctions by specific mRNA degradation, and requires a minimum length of dsR NA. Furthermore, preincubation of dsRNA potentiates its activity. These res ults demonstrate that RNAi can be mediated by sequence-specific processes i n soluble reactions.