Long dsRNAs have been used successfully for RNAi studies in Drosophila and Caenorhabditis elegans, but RNA interference has been difficult to achieve in mammalian cell cultures. "It turns out that there's an antiviral response in mammalian cells where when you introduce long double-stranded RNAs, the cells apoptose and die," explains David Brown, senior R&D scientist at Austin, Texas-based Ambion. "That was a problem." Last May, however, researchers at the Max Planck Institute for Biophysical Chemistry in G¨ottingen, Germany, reported that transfection of mammalian cells with the shorter siRNAs avoided this antiviral response and did in fact lead to a reduction in mRNA levels for the gene targeted by the siRNAs.3
Chemical synthesis of siRNAs, however, can be expensive, especially for labs that do not have access to a core synthesis facility. One chemically synthesized siRNA can cost hundreds of dollars, making the prospect of using this technique for gene knockout ...
