Methods and compositions for RNA interference
The present invention provides methods for attenuating gene expression in a cell, especially in a mammalian cell, using gene-targeted double stranded RNA (dsRNA), such as a hairpin RNA. The dsRNA contains a nucleotide sequence that hybridizes under physiologic conditions of the cell to the nucleotide sequence of at least a portion of the gene to be inhibited (the “target” gene).
1. A method for attenuating expression of a target gene in a mammalian cell, the method comprising:
introducing into a mammalian cell an expression vector comprising:
(i) an RNA polymerase promoter, and
(ii) a sequence encoding a short hairpin RNA molecule comprising a double-stranded region, wherein the double-stranded region consists of at least 20 nucleotides but not more than 29 nucleotides,
wherein the short hairpin RNA molecule is a substrate for Dicer-dependent cleavage and does not trigger a protein kinase RNA-activated (PK) response in the mammalian cell,
wherein the double-stranded region of the short hairpin RNA molecule comprises a sequence that is complementary to a portion of the target gene, and
wherein the short hairpin RNA molecule is stably expressed in the mammalian cell in an amount sufficient to attenuate expression of the target gene in a sequence specific manner, and is expressed in the cell without use of a PK inhibitor, whereby expression of the target gene is inhibited.
2. The method of claim 1 , wherein the expression vector further comprises LTR sequences located 5′ and 3′ of the sequence encoding the short hairpin RNA molecule.
3. The method of claim 1 , wherein the short hairpin RNA molecule comprises a double-stranded region consisting of at least 21 nucleotides.
4. The method of claim 1 , wherein the short hairpin RNA molecule comprises a double-stranded region consisting of at least 22 nucleotides.
5. The method of claim 1 , wherein the short hairpin RNA molecule comprises a double-stranded region consisting of at least 25 nucleotides.
6. The method of claim 1 , wherein the short hairpin RNA molecule comprises a double-stranded region consisting of 29 nucleotides.
7. The method of claim 1 , wherein the short hairpin RNA molecule has a total length of 70 nucleotides.
8. The method of claim 1 , wherein the RNA polymerase promoter comprises a pol II promoter or a pol III promoter.
9. The method of claim 8 , wherein the pol III promoter comprises a U6, an H1, or an SRP promoter.
10. The method of claim 8 , wherein the pol II promoter comprises a U1 or a CMV promoter.