METHODS AND COMPOSITIONS FOR THE SPECIFIC INHIBITION OF GENE EXPRESSION BY DOUBLE-STRANDED RNA
The invention is directed to compositions and methods for selectively reducing the expression of a gene product from a desired target gene in a cell, as well as for treating diseases caused by the expression of the gene. More particularly, the invention is directed to compositions that contain double stranded RNA (“dsRNA”), and methods for preparing them, that are capable of reducing the expression of target genes in eukaryotic cells. The dsRNA has a first oligonucleotide sequence that is between 25 and about 30 nucleotides in length and a second oligonucleotide sequence that anneals to the first sequence under biological conditions. In addition, a region of one of the sequences of the dsRNA having a sequence length of at least 19 nucleotides is sufficiently complementary to a nucleotide sequence of the RNA produced from the target gene to trigger the destruction of the target RNA by the RNAi machinery.
1 . A mammalian cell containing an isolated double stranded nucleic acid capable of reducing the expression of a target gene, wherein the double stranded nucleic acid comprises
a first oligonucleotide strand that is 25-30 nucleotides in length and contains 1-3 DNA bases on the 3′ end of the first oligonucleotide strand; and
a second oligonucleotide strand that is 25-30 nucleotides in length comprising an overhang domain and a primary domain wherein the overhang domain is comprised of modified RNA monomers and the primary domain is capable of hybridizing to the first oligonucleotide strand and is comprised of a combination of unmodified and modified monomers,
wherein said second oligonucleotide strand is sufficiently complementary to a target RNA along at least 19 nucleotides of said second oligonucleotide strand length to reduce target gene expression when said double stranded nucleic acid is introduced into a mammalian cell.