title: N- and C-terminal Upf1 phosphorylations create binding platforms for SMG-6 and SMG-5:SMG-7 during NMD.
abstract: Nonsense-mediated mRNA decay (NMD) is a surveillance mechanism that detects and degrades mRNAs containing premature termination codons (PTCs). SMG-1-mediated Upf1 phosphorylation takes place in the decay inducing complex (DECID), which contains a ribosome, release factors, Upf1, SMG-1, an exon junction complex (EJC) and a PTC-mRNA. However, the significance and the consequence of Upf1 phosphorylation remain to be clarified. Here, we demonstrate that SMG-6 binds to a newly identified phosphorylation site in Upf1 at N-terminal threonine 28, whereas the SMG-5:SMG-7 complex binds to phosphorylated serine 1096 of Upf1. In addition, the binding of the SMG-5:SMG-7 complex to Upf1 resulted in the dissociation of the ribosome and release factors from the DECID complex. Importantly, the simultaneous binding of both the SMG-5:SMG-7 complex and SMG-6 to phospho-Upf1 are required for both NMD and Upf1 dissociation from mRNA. Thus, the SMG-1-mediated phosphorylation of Upf1 creates a binding platforms for the SMG-5:SMG-7 complex and for SMG-6, and triggers sequential remodeling of the mRNA surveillance complex for NMD induction and recycling of the ribosome, release factors and NMD factors.
authors.affiliation: Department of Molecular Biology, Yokohama City University, School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Okada-Katsuhata
authors.forename: Akio
authors.initials: A
authors.lastname: Yamashita
authors.forename: Kei
authors.initials: K
authors.lastname: Kutsuzawa
authors.forename: Natsuko
authors.initials: N
authors.lastname: Izumi
authors.forename: Fumiki
authors.initials: F
authors.lastname: Hirahara
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ohno
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D059365:Nonsense Mediated mRNA Decay; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D020365:RNA Helicases; D019098:Telomerase / Q000737:chemistry / Q000378:metabolism*; D013912:Threonine / Q000502:physiology; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D004722:Endoribonucleases
chemical_list: D048948:14-3-3 Proteins; D002352:Carrier Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D020365:RNA Helicases; D019098:Telomerase; D013912:Threonine; D015534:Trans-Activators; C515801:SMG5 protein, human; C494578:SMG7 protein, human; C514704:SMG1 protein, human; C512261:SMG6 protein, human; D004722:Endoribonucleases; C101828:UPF1 protein, human