Alphavirus nsP3 ADP-ribosylhydrolase Activity Disrupts Stress Granule Formation

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

To determine whether the arsenite-induced nsP3 HVD -associated structures shared SG properties, we treated the cells with cycloheximide. Cycloheximide is an elongation inhibitor that traps mRNAs along with translation factors in polysomes, thus decreasing the availability of mRNAs for SG formation and resulting in SG disassembly ( Fig. 1b ; [9] ). Therefore, bona fide SGs disappear upon cycloheximide treatment. After cycloheximide treatment, the nsP3 HVD no longer co-localized with translation factor eIF3b, suggesting that the nsP3 HVD -associated structures formed upon arsenite treatment were SGs (Fig. 1b, c) . On the other hand, the nsP3 HVD remained co-localized with G3BP1 in both unstressed and stressed conditions likely due to their ability to directly interact ( Fig. 1, Fig. S1c ). Taken together with work from others [36, [40] [41] [42] , these data suggest that expression of full-length nsP3 alters the association of individual SG components (e.g., release of eIF3b and retention of G3BP1 with nsP3), and it is likely that domain(s) other than HVD of nsP3 may be responsible for suppressing SG formation.