VPg, coat protein and five non-structural proteins of potato A potyvirus bind RNA in a sequence-unspecific manner

The potato A potyvirus (PVA)-encoded proteins P1, HC-Pro, P3, CI, VPg, NIaPro, NIb and coat protein (CP) were expressed as 6 x His-tagged recombinant proteins in Escherichia coli and purified to homogeneity. RNA binding was tested using purified proteins in Northwestern and liquid assays. PVA proteins except P3 bound to positive- and negative-sense transcripts prepared from the nontranslated 5'- and 3'-regions of PVA genomic RNA and to full-length transcripts of PVA RNA. RNA binding by these proteins showed no sequence specificity since they also bound to various non-PVA control RNAs. Binding properties of P1, HC-Pro, CI and NIaPro are consistent with previous studies carried out on a few other potyviruses, but the binding of VPg, NIb and CP to RNA reveal novel interactions between RNA and potyvirus proteins. Furthermore, the RNA-binding properties of all major proteins of a potyvirus have not been reported previously.