Patent ID: 8383599

Claim:
A population of mammalian cells stably transfected or stably transduced with a library of expression constructs, wherein each expression construct encodes a short hairpin RNA, each expression construct 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 (PKR) response in the mammalian cells, wherein the double-stranded region of the short hairpin RNA molecule comprises a sequence that is complementary to a portion of a target gene in the mammalian cells, wherein the target gene is an endogenous gene of the mammalian cells, and wherein said population of mammalian cells comprises cells in which the short hairpin RNA molecule is stably expressed in an amount sufficient to attenuate expression of the target gene in a sequence specific manner without use of a PKR inhibitor.