title: Ribosome Elongation Stall Directs Gene-specific Translation in the Integrated Stress Response.
abstract: Upon exposure to environmental stress, phosphorylation of the α subunit of eIF2 (eIF2α-P) represses global protein synthesis, coincident with preferential translation of gene transcripts that mitigate stress damage or alternatively trigger apoptosis. Because there are multiple mammalian eIF2 kinases, each responding to different stress arrangements, this translational control scheme is referred to as the integrated stress response (ISR). Included among the preferentially translated mRNAs induced by eIF2α-P is that encoding the transcription factor CHOP (DDIT3/GADD153). Enhanced levels of CHOP promote cell death when ISR signaling is insufficient to restore cell homeostasis. Preferential translation of CHOP mRNA occurs by a mechanism involving ribosome bypass of an inhibitory upstream ORF (uORF) situated in the 5'-leader of the CHOP mRNA. In this study, we used biochemical and genetic approaches to define the inhibitory features of the CHOP uORF and the biological consequences of loss of the CHOP uORF on CHOP expression during stress. We discovered that specific sequences within the CHOP uORF serve to stall elongating ribosomes and prevent ribosome reinitiation at the downstream CHOP coding sequence. As a consequence, deletion of the CHOP uORF substantially increases the levels and modifies the pattern of induction of CHOP expression in the ISR. Enhanced CHOP expression leads to increased expression of key CHOP target genes, culminating in increased cell death in response to stress.
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126 and.
authors.forename: Sara K
authors.initials: SK
authors.lastname: Young
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126 and.
authors.forename: Lakshmi Reddy
authors.initials: LR
authors.lastname: Palam
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas 77843-3258.
authors.forename: Cheng
authors.initials: C
authors.lastname: Wu
authors.affiliation: Department of Biology, Texas A&M University, College Station, Texas 77843-3258.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Sachs
authors.affiliation: From the Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126 and rwek@iu.edu.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Wek
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002470:Cell Survival; D002478:Cells, Cultured; D017124:Conserved Sequence; D015852:Eukaryotic Initiation Factor-2 / Q000502:physiology; D005347:Fibroblasts / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010441:Peptide Chain Elongation, Translational; D013312:Stress, Physiological; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism
chemical_list: C497250:Ddit3 protein, mouse; D015852:Eukaryotic Initiation Factor-2; D051742:Transcription Factor CHOP
keywords: CHOP; DDIT3; GADD153; endoplasmic reticulum stress (ER stress); eukaryotic initiation factor 2 (eIF2); stress response; translation control; translation initiation
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