Novel Drosophila Viruses Encode Host-Specific Suppressors of RNAi
(A) In vitro RNA cleavage (slicer) assays in lysates from D. melanogaster embryos (left panel) or D. immigrans embryos (right panel). Radioactively cap-labelled target RNA was incubated in embryo lysate together with a non-specific control siRNA (lanes 1 and 6) or a target specific siRNA (lanes 2–5, 7–10). Target cleavage was determined either in the absence of recombinant protein (lanes 2 and 7) or in the presence of 0.3 µM of MBP (lanes 3 and 8), MBP-DmelNV VP1 (lanes 4 and 9), or DimmNV VP1 (lanes 5 and 10). (B) Quantification of target cleavage in D. melanogaster and D. immigrans embryo lysate in the presence of MBP, DmelNV VP1, or DimmNV VP1 protein. The fraction of cleaved RNA was determined by dividing the intensity of the cleavage product by the total intensity of cleavage product and non-cleaved target. Data are normalized to MBP. Bars represent means and standard deviations of two independent experiments.