Alphavirus nsP3 ADP-ribosylhydrolase Activity Disrupts Stress Granule Formation

Aravinth Kumar Jayabalan; Diane E. Griffin; Anthony K. L. Leung

Similar colocalization of mutant nsP3, eIF3b and G3BP1 were observed with different SG inducers such as clotrimazole and thapsigargin (Fig. S4b-c) , suggesting that the requirement of ADPribosylhydrolase activity for suppression of SG formation during viral infection is not stress-specific. To test whether these mutant nsP3/eIF3b/G3BP1 foci are sensitive to change in translation similar to SGs, we treated the infected cells with cycloheximide. Similar to the studies expressing nsP3 protein alone ( Fig. 2c) , the translation initiation factor eIF3b was diffusely distributed in the cytoplasm rather than in foci (Fig. S4d) . However, mutant nsP3 and G3BP1 remained as foci during viral infection, suggesting that G3BP1 associates with additional viral proteins besides nsP3 in these foci (e.g., [56] ). Taken together, these data suggest that the ADP-ribosylhydrolase activity of nsP3 can alter the association between individual SG components during viral infection.