Activating transcription factor 4 (ATF4) is a master transcriptional regulator of the integrated stress response, leading cells toward adaptation or death. ATF4's induction under stress was thought to be due to delayed translation reinitiation, where the reinitiation-permissive upstream open reading frame 1 (uORF1) plays a key role. Accumulating evidence challenging this mechanism as the sole source of ATF4 translation control prompted us to investigate additional regulatory routes. We identified a highly conserved stem-loop in the uORF2/ATF4 overlap, immediately preceded by a near-cognate CUG, which introduces another layer of regulation in the form of ribosome queuing. These elements explain how the inhibitory uORF2 can be translated under stress, confirming prior observations but contradicting the original regulatory model. We also identified two highly conserved, potentially modified adenines performing antagonistic roles. Finally, we demonstrated that the canonical ATF4 translation start site is substantially leaky scanned. Thus, ATF4's translational control is more complex than originally described, underpinning its key role in diverse biological processes.

• Keywords
• ATF4, CP: Molecular biology, integrated stress response, ribosome, ribosome queuing, translation reinitiation, translational control, unfolded protein response,
• MeSH
• Stress, Physiological MeSH
• HEK293 Cells MeSH
• Humans MeSH
• Open Reading Frames * genetics   MeSH
• Protein Biosynthesis * MeSH
• Ribosomes * metabolism   MeSH
• Base Sequence MeSH
• Activating Transcription Factor 4 * metabolism   genetics   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• ATF4 protein, human MeSH Browser
• Activating Transcription Factor 4 * MeSH