Patent ID: 8557785

Claim:
A method of inducing ribonucleic acid interference (RNAi) of a target gene in a cell, the method comprising introducing into a host cell in vitro an isolated nucleic acid molecule comprising a regulatory sequence operably linked to a nucleic acid sequence that encodes an engineered ribonucleic acid (RNA) precursor; and culturing the cell under conditions sufficient for the cell to express the RNA precursor and to form a small interfering ribonucleic acid (siRNA) within the cell, thereby inducing RNAi of the target gene in the cell, wherein the precursor comprises (i) a first stem portion consisting of a sequence of 18 to about 30 nucleotides that is complementary to a sequence of a messenger RNA (mRNA) of the target gene; (ii) a second stem portion consisting of a sequence of 18 to about 30 nucleotides that is sufficiently complementary to the first stem portion to hybridize with the first stem portion to form a duplex stem; and (iii) a loop portion that connects the two stem portions, wherein the loop portion consists of 2 to 9 nucleotides.