As shown in Figure 3B, the amount of p19 protein in VIp19 is considerably lower compared with that in V2Ip19. Taking into account the lower mRNA level, double p19 with an IRES can produce more than double the amount of p19 protein than that of a single p19
(Figure 3B). We speculate that the amount of p19 protein produced from VIp19 is not enough to bind the siRNAs produced from dsVenus. In contrast, double p19 with an IRES (V2Ip19) can efficiently suppress siRNAs. These results indicate that supplying p19 with a double IRES is effective in protecting the mRNA from silencing.