title: A network of SMG-8, SMG-9 and SMG-1 C-terminal insertion domain regulates UPF1 substrate recruitment and phosphorylation.
abstract: Mammalian nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance mechanism that degrades mRNAs containing premature translation termination codons. Phosphorylation of the essential NMD effector UPF1 by the phosphoinositide-3-kinase-like kinase (PIKK) SMG-1 is a key step in NMD and occurs when SMG-1, its two regulatory factors SMG-8 and SMG-9, and UPF1 form a complex at a terminating ribosome. Electron cryo-microscopy of the SMG-1-8-9-UPF1 complex shows the head and arm architecture characteristic of PIKKs and reveals different states of UPF1 docking. UPF1 is recruited to the SMG-1 kinase domain and C-terminal insertion domain, inducing an opening of the head domain that provides access to the active site. SMG-8 and SMG-9 interact with the SMG-1 C-insertion and promote high-affinity UPF1 binding to SMG-1-8-9, as well as decelerated SMG-1 kinase activity and enhanced stringency of phosphorylation site selection. The presence of UPF2 destabilizes the SMG-1-8-9-UPF1 complex leading to substrate release. Our results suggest an intricate molecular network of SMG-8, SMG-9 and the SMG-1 C-insertion domain that governs UPF1 substrate recruitment and phosphorylation by SMG-1 kinase, an event that is central to trigger mRNA decay.
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France Unit of Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, UMI 3265, 71 Avenue des Martyrs, 38042 Grenoble, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Deniaud
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France Unit of Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, UMI 3265, 71 Avenue des Martyrs, 38042 Grenoble, France.
authors.forename: Manikandan
authors.initials: M
authors.lastname: Karuppasamy
authors.affiliation: European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bock
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France Unit of Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, UMI 3265, 71 Avenue des Martyrs, 38042 Grenoble, France.
authors.forename: Simonas
authors.initials: S
authors.lastname: Masiulis
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France Unit of Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, UMI 3265, 71 Avenue des Martyrs, 38042 Grenoble, France.
authors.forename: Karine
authors.initials: K
authors.lastname: Huard
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France Unit of Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, UMI 3265, 71 Avenue des Martyrs, 38042 Grenoble, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Garzoni
authors.affiliation: Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Kerschgens
authors.affiliation: Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors.forename: Matthias W
authors.initials: MW
authors.lastname: Hentze
authors.affiliation: Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany.
authors.forename: Andreas E
authors.initials: AE
authors.lastname: Kulozik
authors.affiliation: European Molecular Biology Laboratory, Structural and Computational Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Beck
authors.affiliation: Department of Pediatric Oncology, Hematology and Immunology, University of Heidelberg, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 350, 69120 Heidelberg, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Neu-Yilik
authors.affiliation: European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France Unit of Virus Host-Cell Interactions, University Grenoble Alpes-EMBL-CNRS, UMI 3265, 71 Avenue des Martyrs, 38042 Grenoble, France School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK schaffitzel@embl.fr.
authors.forename: Christiane
authors.initials: C
authors.lastname: Schaffitzel
mesh_terms: D001665:Binding Sites; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D020365:RNA Helicases; C514704:SMG1 protein, human