RNA INTERFERENCE MEDIATING SMALL RNA MOLECULES
Double-stranded RNA (dsRNA) induces sequence-specific post-transcriptional gene silencing in many organisms by a process known as RNA interference (RNAi). Using a Drosophila in vitro system, we demonstrate that 19-23 nt short 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 produced siRNP complex.
1 . Isolated double-stranded RNA molecule, wherein each RNA strand has a length from 19-25 nucleotides, wherein said RNA molecule is capable of target-specific RNA interference by cleaving target RNA at a single site thereof.
2 . The double-stranded RNA molecule of claim 1 , wherein each RNA strand has a length of 19-23 nucleotides.
3 . The double-stranded RNA molecule of claim 1 , wherein the single site is located 11 or 12 nt downstream of the first nucleotide complementary to a guide sequence of the double-stranded RNA molecule.
4 . Composition comprising a single double-stranded RNA molecule wherein each RNA strand has a length from 19-25 nucleotides, wherein said RNA molecule is capable of target-specific nucleic acid modifications.
5 . The composition of claim 4 , wherein the composition comprises a single species of double-stranded RNA molecule.
6 . The composition of claim 4 , wherein said RNA molecule is capable of RNA interference.
7 . The composition of claim 4 , wherein each RNA strand has a length of 19-23 nucleotides.