Nucleic acid protection assays dsRNA binding proteins can compete with Dicer (an endoribonuclease of the RNAse III family), reducing its ability to cleave long dsRNAs into 21 bp-long 'interfering' RNAs [27] . A dsRNA ladder (New England Biolabs) with sizes ranging from 500 to 21 bp was used as a template for Dicer cleavage. A competition assay with Dicer (Mobitech), was carried in the presence of 150 ng of expressed BTV-8 or GIV NS4, in a final volume of 20 ml containing 8 ml of the Dicer reaction, 2 mg of dsRNA, 1 mM ATP, 2.5 mM MgCl2. The reaction was incubated at room temperature for 20 minutes, followed by addition of a 1.5 U of Dicer, then incubated for a further 6 hours at 37uC. The reaction products were analysed by 3% agarose gel electrophoresis.