Patent ID: 7893036

Claim:
A method of making an engineered ribonucleic acid (RNA) precursor comprising the steps of: (a) selecting a wild-type miRNA or stRNA precursor sequence; and (b) modifying the wild-type precursor sequence to produce an engineered RNA precursor comprising (i) a first stem portion comprising a sequence of about 18 to about 40 nucleotides that is substantially complementary to a sequence of a messenger RNA (mRNA) of a target gene of the mammalian cell; (ii) a second stem portion comprising a sequence of about 18 to about 40 nucleotides that is sufficiently complementary to the about 18 to about 40 nucleotide sequence of 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, such that the engineered RNA precursor, when expressed in a cell, is processed by the cell to produce a duplex siRNA that mediates RNA interference (RNAi) by selectively cleaving the mRNA, wherein the wild-type precursor sequence is modified by incorporating the sequence of the siRNA duplex.