title: Ribosome Reinitiation Directs Gene-specific Translation and Regulates the Integrated Stress Response.
abstract: In the integrated stress response, phosphorylation of eIF2α (eIF2α-P) reduces protein synthesis to conserve resources and facilitate preferential translation of transcripts that promote stress adaptation. Preferentially translated GADD34 (PPP1R15A) and constitutively expressed CReP (PPP1R15B) function to dephosphorylate eIF2α-P and restore protein synthesis. The 5'-leaders of GADD34 and CReP contain two upstream ORFs (uORFs). Using biochemical and genetic approaches we show that features of these uORFs are central for their differential expression. In the absence of stress, translation of an inhibitory uORF in GADD34 acts as a barrier that prevents reinitiation at the GADD34 coding region. Enhanced eIF2α-P during stress directs ribosome bypass of the uORF, facilitating translation of the GADD34 coding region. CReP expression occurs independent of eIF2α-P via an uORF that allows for translation reinitiation at the CReP coding region independent of stress. Importantly, alterations in the GADD34 uORF affect the status of eIF2α-P, translational control, and cell adaptation to stress. These results show that properties of uORFs that permit ribosome reinitiation are critical for directing gene-specific translational control in the integrated stress response.
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126.
authors.forename: Sara K
authors.initials: SK
authors.lastname: Young
authors.affiliation: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Willy
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: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5126. Electronic address: rwek@iu.edu.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Wek
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004247:DNA; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010766:Phosphorylation; D014176:Protein Biosynthesis / Q000502:physiology*; D054645:Protein Phosphatase 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D015852:Eukaryotic Initiation Factor-2; D004247:DNA; C513256:Ppp1r15a protein, mouse; D054645:Protein Phosphatase 1
keywords: CReP; GADD34; Integrated Stress Response; endoplasmic reticulum stress (ER stress); eukaryotic initiation factor 2 (eIF2); ribosome reinitiation; stress response; translation control; translation initiation; uORF