Interaction of nucleic acids with core-like and subcore-like particles of bluetongue virus

Bluetongue virus (BTV) core-like particles (CLPs) were synthesized by coexpression of VP3 and VP7 using a dual recombinant baculovirus. Purified CLPs were shown to bind single-stranded RNA in three different assay systems: gel retardation, nitrocellulose binding, and sucrose gradient sedimentation. CLPs showed equal affinity for BTV-specific and non-BTV RNA and also bound DNA. RNAase protection experiments demonstrated that bound RNA was accessible to immobilized ribonuclease, suggesting that the RNA was predominantly present on the outside of the CLPs. By using individually purified VP7 and VP3 in separate assays, the binding activity was shown to reside on VP3. These results indicate further functional homologies between BTV VP3 and the rotavirus inner-core VP2 protein.