Reconstitution of the RNAi response in human cells using drosophila gene products

While mammalian somatic cells are incapable of mounting an effective RNA interference (RNAi) response to viral infections, plants and invertebrates are able to generate high levels of functional short interfering RNAs (siRNAs) of viral origin that can effectively control many infections. In Drosophila, the RNAi response is mediated by the Dicer 2 enzyme (dDcr2) acting in concert with two co-factors called Loqs-PD and R2D2. To examine whether a functional RNAi response could be reconstituted in human somatic cells by expression of these insect proteins, we expressed dDcr2, in the presence or absence of Loqs-PD and/or R2D2, in a previously described human cell line, NoDice/?PKR, that lacks functional forms of both the human Dicer (dcr) and EIF2AK2 (pkr) gene. Upon expression of dDcr2, Loqs-PD and R2D2 in these human cells, we observed the production of ~21-nt long siRNAs, derived from a co-transfected double stranded RNA (dsRNA) expression vector, that were loaded into the human RNA-induced silencing complex (RISC) and were able to significantly reduce the expression of a cognate indicator gene. We conclude that it is possible to at least partly rescue the ability of mammalian somatic cells to express functional siRNAs by using gene products of invertebrate origin. Overall design: Combinations of Drosophila Dicer2 and cofactors were transfected into 425-PKR cells to determine whether they were sufficient for genesis of siRNAs in mammalian cells.