The interactions between satellite panicum mosaic virus (SPMV) capsid protein (CP) and its 824 nucleotide (nt) single stranded RNA were investigated by gel mobility shift assay and Northwestern blot assay. SPMV CP has specificity for its RNA at high affinity, but little affinity for non-viral RNA. The SPMV CP also bound a 350 nt satellite RNA (satRNA) that, like SPMV, is dependent on panicum mosaic virus for its replication. SPMV CP has the novel property of encapsidating SPMV RNA and satRNA. Competition gel mobility shift assays performed with a non-viral RNA and unlabeled SPMV RNA and satRNA revealed that these RNA:protein interactions were in part sequence specific.
