Figure 1

Cloning strategy for constructing vectors containing multiple siRNA expression cassettes. a) Detailed procedures for constructing the vectors containing a single siRNA expression cassette (p1-siRNA) or two siRNA cassettes (p2-siRNA). SK+: pBluescript II SK+; MCS: multiple cloning sites; mU6: mouse U6 promoter. The restriction sites in blue highlight the cloning sites for insertion of DNA duplex encoding siRNA. b) Schematic diagram showing the six vectors containing multiple siRNA expression cassettes: p1-siRNA, p2-siRNA, p3-siRNA, p4-siRNA, p5-siRNA and p6-siRNA. Each cassette contains a mouse U6 promoter (mU6), a pair of cloning sites for insertion of DNA duplex encoding siRNA (highlighted in blue) and a block which is included to prevent potential cross-interference among these cassettes. Detailed procedures for constructing p3-siRNA, p4-siRNA, p5-siRNA and p6-siRNA are provided (see Additional file 1).