title: Phosphorylation of hUPF1 induces formation of mRNA surveillance complexes containing hSMG-5 and hSMG-7.
abstract: Eukaryotic mRNAs containing premature termination codons (PTCs) are degraded by a process known as nonsense-mediated mRNA decay (NMD). NMD has been suggested to require the recognition of PTC by an mRNA surveillance complex containing UPF1/SMG-2. In multicellular organisms, UPF1/SMG-2 is a phosphoprotein, and its phosphorylation contributes to NMD. Here we show that phosphorylated hUPF1, the human ortholog of UPF1/SMG-2, forms a complex with human orthologs of the C. elegans NMD proteins SMG-5 and SMG-7. The complex also associates with protein phosphatase 2A (PP2A), resulting in dephosphorylation of hUPF1. Overexpression of hSMG-5 mutants that retain interaction with P-hUPF1 but which cannot induce its dephosphorylation impair NMD, suggesting that NMD requires P-hUPF1 dephosphorylation. We also show that P-hUPF1 forms distinct complexes containing different isoforms of hUPF3A. We propose that sequential phosphorylation and dephosphorylation of hUPF1 by hSMG-1 and PP2A, respectively, contribute to the remodeling of the mRNA surveillance complex.
authors.affiliation: Department of Molecular Biology, Yokohama City University School of Medicine, Yokohama 236-0004, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Ohnishi
authors.forename: Akio
authors.initials: A
authors.lastname: Yamashita
authors.forename: Isao
authors.initials: I
authors.lastname: Kashima
authors.forename: Thomas
authors.initials: T
authors.lastname: Schell
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Anders
authors.forename: Andrew
authors.initials: A
authors.lastname: Grimson
authors.forename: Takahisa
authors.initials: T
authors.lastname: Hachiya
authors.forename: Matthias W
authors.initials: MW
authors.lastname: Hentze
authors.forename: Philip
authors.initials: P
authors.lastname: Anderson
authors.forename: Shigeo
authors.initials: S
authors.lastname: Ohno
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002458:Cell Fractionation; D018389:Codon, Nonsense; D006367:HeLa Cells; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D020365:RNA Helicases; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D018389:Codon, Nonsense; D046911:Macromolecular Substances; D012333:RNA, Messenger; C472410:SMG-5 protein, C elegans; C117551:SMG-7 protein, C elegans; D015534:Trans-Activators; D014157:Transcription Factors; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D020365:RNA Helicases; C101828:UPF1 protein, human