RNA interference is mediated by 21- and 22-nucleotide RNAs

TLDR

Double‑stranded RNA induces sequence‑specific post‑transcriptional gene silencing via RNA interference in many organisms. The study demonstrates that 21‑ and 22‑nt RNA fragments are the sequence‑specific mediators of RNAi using a Drosophila in vitro system. Short interfering RNAs are generated by RNase III‑like processing of long dsRNA and act as 21‑ or 22‑nt mediators of RNAi in the Drosophila in vitro system. Chemically synthesized siRNA duplexes with 3′ overhangs efficiently cleave target RNA at a central site, and the direction of dsRNA processing determines whether sense or antisense RNA is cleaved by the siRNA–protein complex.

Abstract

Double-stranded RNA (dsRNA) induces sequence-specific posttranscriptional gene silencing in many organisms by a process known as RNA interference (RNAi). Using a Drosophila in vitro system, we demonstrate that 21- and 22-nt RNA fragments are the sequence-specific mediators of RNAi. The short interfering RNAs (siRNAs) are generated by an RNase III–like processing reaction from long dsRNA. Chemically synthesized siRNA duplexes with overhanging 3′ ends mediate efficient target RNA cleavage in the lysate, and the cleavage site is located near the center of the region spanned by the guiding siRNA. Furthermore, we provide evidence that the direction of dsRNA processing determines whether sense or antisense target RNA can be cleaved by the siRNA–protein complex.