G3BP is dispensable for translational arrest, required for SG formation. (A) U2OS-WT or ΔΔG3BP1/2 cells were untreated or exposed to 500 µM AS (1 h) or 0.4 M sorbitol (30 min) and lysed in SDS and resolved using SDS-PAGE/Western blotting. Blots were probed as indicated. M_r (kD) are shown. (B) ΔΔG3BP1/2 cells stably expressing the indicated constructs, analyzed by Western blot and probed as indicated. M_r (kD) are shown. (C) ΔΔG3BP1/2 cells stably expressing the indicated proteins, treated as indicated, stained, and scored for SGs and quantified. Data shown are mean ± SEM; n = 3. (D) U2OS-WT (dark bars) or ΔΔG3BP1/2 cells (light bars) were transiently transfected with indicated plasmids, untreated or exposed to 500 µM AS for 1 h, and then stained and scored for SGs. Data shown are mean ± SEM and analyzed using the unpaired t test. ***, P < 0.005; n = 3. (E) U2OS-WT (dark bars) or ΔΔG3BP1/2 cells (light bars) were transiently transfected with indicated plasmids and then stained and scored for p-eIF2α–positive transfectants. Data represent mean. n = 2.