The IVT dsRNA was synthesized in vitro using an E. coli T7 polymerase produced by expression in BL21 (Rosetta2) competent
cells and purified using His-SELECT-HF (Sigma, St. Louis, MO). A
plasmid containing the DvSnf7 sequence was linearized with a
restriction enzyme that cut at the end of the DvSnf7 transcript and
used in an in vitro transcription reaction containing 32 mM MgCl2,
10 mM DTT, 200 mM each ATP, CTP, GTP and UTP, 10 U/ml IPP,
0.05 mg/ml T7 polymerase and 5% DMSO to produce a 968 nucleotide RNA. Following transcription, the RNA was heated to ~70 C
and then allowed to cool at room temperature ensuring the
inverted repeats contained within the RNA were annealed to each
other and form a hairpin loop. This dsRNA was treated with DNase
to remove any remaining plasmid and purified using phenol:-
chloroform. The pellet was resuspended in UltraPure Water (Life
Technologies, Grand Island, NY), quantified using a NanoDrop
spectrophotometer, and stored at e 80 C.