Enhancement of RNA Interference Effect in P19 EC Cells by an RNA-dependent RNA Polymerase

Background: RNA interference (RNAi) is a phenomenon uses double-stranded RNA (dsRNA) to specifically inhibit gene expression. The non-specific silencing caused by interferon response to dsRNA in mammalian cells limits the potential of utilizing RNAi to study gene function. Duplexes of 21-nucleotide short interfering dsRNA (siRNA) inhibit gene expression by RNAi. In some organisms, siRNA can also function as a primer converting mRNA into dsRNA that are further cleaved to produce more siRNA. This activity involves the enzyme RNA-dependent RNA polymerase (RdRP). There are no known RdRP involved in RNAi in mammals. By using an RdRP from Caenorhabditis elegance named ego-1, investigators intend to enhance RNAi effect in mammalian cells. The aims of this project were: 1) to investigate the efficiency of siRNA to enhanced green fluorescent protein (eGFP) gene silencing and 2) to enhance the RNAi effect. Methods: We used a vector-based siRNA to target eGFP. Also we used a vector expressing ego-1 to test for a possible amplification effect of RNAi. The expression of eGFP in the cells was detected by using fluorescent microscopy, flowcytometry and Western-blotting. Results: Transfection of the plasmid into P19 cells significantly decreased eGFP fluorescence. In addition, eGFP protein was reduced. Preliminary data suggested that the presence of ego-1 enhanced the RNAi effect. Conclusion: The results indicated that use of hairpin siRNA expression vectors for RNAi is a promising method to inhibition of gene expression in mammalian cells. Also, introducing RdRP enzyme to mammalian cells might amplify the RNAi effect in the cells.