Fig. 7: The Pelota-mediated RQC anti-viral defense counteracted by the RNA polymerase of potyvirids.

A diagram illustrating the Pelota-mediated degradation of the viral RNA of potyvirids and the viral NIb counter-defense strategy. In host cells, Pelota is SUMOylated by interacting with the SUMO conjugating enzyme SCE1, which then forms an active Pelota-Hbs1 RNA surveillance complex. The potyvirids conserved G1-2A6-7 motifs are targets of the Pelota-Hbs1 surveillance complex, which triggers RQC to mediate viral RNA decay. The NIb protein from potyvirids contains two conserved SIM sites: SIM2 for SUMO modification and SIM3 for interacting with the SUMO-E2 enzyme, SCE1. NIb-SIM3 interferes with the Pelota-SCE1 interaction as a SUMOylation decoy, suppressing SUMOylation-dependent RQC, which leads to the inhibition of virus transcript degradation and the promotion of viral accumulation. S, SUMOylation. The arrow indicates activation, while the “T” sign represents attenuation or suppression.