Alphavirus nsP3 ADP-ribosylhydrolase Activity Disrupts Stress Granule Formation

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

Next, we tested whether the ADP-ribose binding and hydrolase activities of nsP3 MD are responsible for suppressing SG formation (Fig. 2) . Three classes of MD mutants were used [38] : (1) no ADP-ribose binding and little hydrolase activity (D10A, G32E, and G112E); (2) weak ADP-ribose binding and weak hydrolase activity (G32S); and (3) weak hydrolase activity but stronger ADP-ribosebinding than wild-type (WT) (Y114A). As with WT nsP3, all overexpressed full-length nsP3 MD mutants appeared in G3BP1-positive foci with or without arsenite (Fig. 2a, S2a ). However, unlike WT, all full length nsP3 mutants co-localized with SG components G3BP1 and eIF3b upon arsenite treatment ( Fig. 2a, b ). Given that all tested mutants have deficiencies in ADP-ribosylhydrolase activity, their inability to prevent SG formation is likely due to the absence of this enzymatic activity.