| abstract |
Double stranded RNA (dsRNA) induces sequence-specific post-transcriptional gene quenching in many organisms in a manner known as RNA interference (RNAi). Using the in vivo Drosophila system, short RNA fragments containing 19 to 23 nucleotides have been shown to be sequence-specific mediators of RNAi. Short interfering RNAs (siRNAs) were generated by processing of long dsRNA reactions similar to the Reaction III reaction. Chemically synthesized siRNA duplexes extending beyond the 3'-end mediate efficient cleavage of the target RNA in the lysate and cleavage sites are located near the center of the region covered by the control siRNA. Further, evidence is provided that the direction of dsRNA processing determines whether the prepared siRNA complex cleaves positive or negative target RNA. |