Quantitative PCR analysis revealed that, IFN-ß, IL-6 and PKR transcripts were potently induced in poly I:C treated GADD34 DC/ DC MEFs (Fig. 4D ), thus excluding any major transcriptional alterations in these cells, as confirmed by the normal levels of cystatin C mRNA, which remained constant in all conditions studied. Moreover, using confocal immunofluorescence microscopy, we could not detect intracellular IFN-b in poly I:C-stimulated GADD34 DC/DC MEFs, in contrast to WT cells, which abundantly expressed the cytokine, despite the global translation arrest (Fig.  S8) . Thus, we could attribute the deficit in cytokine secretion of the GADD34 DC/DC MEFs to a profound inability of these cells to synthesize cytokines, rather than to a defect in transcription or general protein secretion.