Methods for producing interfering RNA molecules in mammalian cells and therapeutic uses for such molecules

A method for testing the expression and function of a small interfering RNA (siRNA) molecule, comprising:

• co-introducing into a mammalian cell i) one or more vectors comprising a first cassette comprising a mammalian U6 RNA pol III promoter operatively linked to a first nucleic acid encoding a sense strand of a double stranded siRNA molecule, wherein the first nucleic acid is positioned at the first nucleotide of the transcript of the mammalian U6 RNA pol III promoter in the first cassette and a second cassette comprising a mammalian U6 RNA pol III promoter operatively linked to a second nucleic acid encoding an antisense strand of the double stranded siRNA molecule, wherein the second nucleic acid is positioned at the first nucleotide of the transcript of the mammalian U6 RNA pol III promoter in the second cassette, wherein the first cassette and the second cassette are in a same vector or are in separate vectors and wherein the double stranded siRNA molecule is specific for a target gene, and ii) a vector comprising the target gene and a suitable second promoter;
• growing the mammalian cell under conditions suitable for expression of the nucleic acid sequences and the target gene;
• determining if the double stranded siRNA molecule is expressed and if expression of the target gene is reduced, wherein the sense strand and the antisense strand of the double stranded siRNA molecule are not capped if the double stranded RNA molecule is expressed, whereby the expression and function of the siRNA molecule is tested.