Zinc ions stimulate the cooperative RNA binding of hordeiviral γb protein

A small regulatory γb protein of the Poa semilatent hordeivirus (PSLV) contains two zinc finger-like motifs separated by a basic motif in the N-terminal part and a C-terminal coiled-coil motif. Interactions of the recombinant PSLV γb protein and its mutants with various RNAs (ssRNA, dsRNA, ssRNA oligonucleotides) and ssDNA were studied in gel-shift assays. The results demonstrated that zinc ions are essential for effective nucleic-acid-binding activity of the γb protein, suggesting the important role of zinc finger motifs in these interactions. Deletion of the C-proximal coiled-coil region did not affect highly cooperative RNA–protein binding, indicating that the N-terminal part of the protein contributes to the protein–protein interactions needed for the protein–RNA cooperativity.