Reflections on the inhibition of RNAi by cell death signaling.

Mutations and most transgenes that induce ectopic cell death in Drosophila will produce an inhibitory effect on RNA interference (RNAi) in adjacent cells. When extensive cell death is sporadically induced using a heat shock promoted-head involution defective (hs-hid) transgene, molecular attributes of this inhibition can be studied. For a Green Fluorescent Protein (GFP) RNAi construct, cell death causes a greater accumulation of the mature mRNA and the double stranded RNA with an accompanying reduction in the homologous siRNAs. Endogenous transposable element expression is increased and there is an overall reduction in their corresponding siRNAs. The implications of this finding for the conduct of RNAi and potential reasons for its existence are discussed.