GADD34 expression is required for global translation recovery in response to thapsigargin but not to poly I:C We next evaluated the relevance of GADD34 induction, by treating WT and GADD34 DC/DC fibroblasts with poly I:C or with drugs known to induce ER stress, such as thapsigargin and the Nglycosylation inhibitor tunicamycin [52] . As expected, in WT cells eIF2a phosphorylation was rapidly increased in response to all ISR-inducing stimuli and decreased concomitantly with the expression of GADD34 over time ( Fig. 3A and S4 ) [52] . Consequently eIF2a phosphorylation was greatly increased in GADD34 DC/DC MEFs in all the conditions tested ( Fig. 3A and  S4A ).