title: Evolutionarily conserved IMPACT impairs various stress responses that require GCN1 for activating the eIF2 kinase GCN2.
abstract: In response to a range of environmental stresses, phosphorylation of the alpha subunit of the translation initiation factor 2 (eIF2α) represses general protein synthesis coincident with increased translation of specific mRNAs, such as those encoding the transcription activators GCN4 and ATF4. The eIF2α kinase GCN2 is activated by amino acid starvation by a mechanism involving GCN2 binding to an activator protein GCN1, along with association with uncharged tRNA that accumulates during nutrient deprivation. We previously showed that mammalian IMPACT and its yeast ortholog YIH1 bind to GCN1, thereby preventing GCN1 association with GCN2 and stimulation of this eIF2α kinase during amino acid depletion. GCN2 activity is also enhanced by other stresses, including proteasome inhibition, UV irradiation and lack of glucose. Here, we provide evidence that IMPACT affects directly and specifically the activation of GCN2 under these stress conditions in mammalian cells. We show that activation of mammalian GCN2 requires its interaction with GCN1 and that IMPACT promotes the dissolution of the GCN2-GCN1 complex. To a similar extent as the overexpression of YIH1, overexpression of IMPACT in yeast cells inhibited growth under all stress conditions that require GCN2 and GCN1 for cell survival, including exposure to acetic acid, high levels of NaCl, H₂O₂ or benomyl. This study extends our understanding of the roles played by GCN1 in GCN2 activation induced by a variety of stress arrangements and suggests that IMPACT and YIH1 use similar mechanisms for regulating this eIF2α kinase.
authors: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
authors: Tavane D
authors: TD
authors: Cambiaghi
authors: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil.
authors: Catia M
authors: CM
authors: Pereira
authors: Institute of Natural and Mathematical Sciences, Massey University, New Zealand.
authors: Renuka
authors: R
authors: Shanmugam
authors: Institute of Natural and Mathematical Sciences, Massey University, New Zealand.
authors: Michael
authors: M
authors: Bolech
authors: Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, USA.
authors: Ronald C
authors: RC
authors: Wek
authors: Institute of Natural and Mathematical Sciences, Massey University, New Zealand.
authors: Evelyn
authors: E
authors: Sattlegger
authors: Department of Microbiology, Immunology and Parasitology, Escola Paulista de Medicina, Universidade Federal de São Paulo, Brazil. Electronic address: bacastilho@unifesp.br.
authors: Beatriz A
authors: BA
authors: Castilho
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D017124:Conserved Sequence / Q000235:genetics*; D004789:Enzyme Activation; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D019143:Evolution, Molecular; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D016601:RNA-Binding Proteins; D013312:Stress, Physiological / Q000502:physiology*; D015534:Trans-Activators
chemical_list: D002352:Carrier Proteins; D015852:Eukaryotic Initiation Factor-2; C504444:GCN1 protein, mouse; C107747:Impact protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D016601:RNA-Binding Proteins; D015534:Trans-Activators
keywords: GCN1; GCN2; IMPACT; Translational regulation; YIH1; eIF2