A novel system for rapid screening of effective siRNA target sites by one step transfection with a single vector

siRNA technique has been widely used to study the gene functions and to develop disease therapeutics. One of the challenges of RNAi application is to obtain the most effective target specific siRNA sequences. Currently the process to select and validate optimal siRNA sites for a given gene, which is usually based on screening by using Western blot, Northern blot or Q-PCR, remains empirical and time consuming. Although few fluorescence-based siRNA sequence selection systems have proven useful, the rapid and efficient screening of siRNA target sites is still challenging. In the paper, we developed a quick and efficient method to screen siRNA target sites with a novel single vector system, which contains the following cassettes: (1) an eGFP reporter gene expression cassette followed by a multiple cloning site and SV40 pA for insertion of a target sequence; (2) siRNA expression cassette containing a dual PoI III promoter driving in opposite directions; and (3) an internal loading control, mCherry reporter gene. Based on this one-step transfection with single vector system, we could rapidly screen effective, target specific siRNA fragments in an unbiased manner by judging the fluorescence intensity ratio of eGFP to mCherry. The generation of this novel vector system will promote the application of siRNA in basic research and disease therapy.