eIF3d controls the persistent integrated stress response
All cells respond to intrinsic and extrinsic stresses by reducing global protein synthesis and activating select gene programs necessary for survival. Here, we show the fundamental integrated stress response (ISR) is driven by the non-canonical cap-binding protein eIF3d which acts as a master effector to control core stress response orchestrators, the translation factor eIF2? and the transcription factor ATF4. We find that during persistent stress, eIF3d activates translation of the protein kinase GCN2, inducing eIF2? phosphorylation and inhibiting global protein synthesis. In parallel, eIF3d upregulates the m6A demethylase enzyme ALKBH5 to drive 5' UTR-specific demethylation of stress response genes, including ATF4. Ultimately, this cascade converges on ATF4 expression by increasing mRNA engagement of translation machinery and enhancing ribosome bypass of upstream open reading frames. Our results reveal that eIF3d acts as a critical life-or-death decision point during adaptation to chronic stress and uncover a synergistic signaling mechanism in which translational cascades dynamically complement transcriptional amplification to control essential cellular processes. Overall design: We performed RNA-Seq or m6A-eCLIP analysis of HEK293T expressing WT or phosphomimetic eIF3d during chronic ER stress. We also performed eIF3d-Subunit-Seq analysis of HEK293T during chronic ER stress. Grant:  National Institutes of Health (1R35GM142527).