NUCLEIC ACID-BINDING PROPERTIES OF A BACTERIALLY EXPRESSED POTATO-VIRUS-Y HELPER COMPONENT-PROTEINASE

The potyvirus helper component-proteinase (HC-Pro) is a multifunctiona l protein previously reported to have affinity for polyribonucleotides . To investigate further the ability of HC-Pro to bind nucleic acids, the potato virus Y (PW) LYE84 isolate HC-Pro gene was amplified, clone d in an Escherichia coli expression vector and sequenced. HC-Pro was e xpressed as a fusion with the maltose-binding protein and purified by affinity chromatography. Electrophoretic mobility-shift assays demonst rated that HC-fro acts as a sequence nonspecific RNA-binding protein a nd suggest that more than one molecule of protein was bound per molecu le of RNA. The HC-Pro RNA-binding activity was stable in 400 mM-NaCl a nd temperature sensitive. The recombinant protein preferentially bound ssRNA over DNA or dsRNA and showed little, if any, affinity for poly( A). The possible implications of the RNA-binding activity of HC-Pro in potyvirus replication and movement are discussed.