2002 Fiscal Year Final Research Report Summary
Molecular mechanism of mammalian mRNA surveillance
| Project/Area Number |
13480211
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional biochemistry
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| Research Institution | Yokohama City University |
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Principal Investigator |
OHNO Shigeo Yokohama City University School of Medicine Department of Molecular Biology, Professor, 医学部, 教授 (10142027)
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| Co-Investigator(Kenkyū-buntansha) |
AKIMOTO Kazunori Yokohama City University School of Medicine Department of Molecular Biology, Assistant Professor, 医学部, 助手 (70285104)
HIRAI Syu-ichi Yokohama City University School of Medicine Department of Molecular Biology, Associate Professor, 医学部, 助教授 (80228759)
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| Project Period (FY) |
2001 – 2002
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| Keywords | nonsense mutation / mRNA degradation / mRNA surveillance / NMD / protein kinas / PIK remitted protein kinas / RNA helices / ATPase |
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| Research Abstract |
Nonsense-mediated mRNA decay (NMD) is a conserved surveillance mechanism that eliminates imperfect mRNAs containing premature translation termination codons (PTCs) and code for nonfunctional or potentially harmful polypeptides. We show that a novel phosphatidylinositol 3-kinase-related protein kinas, hSMG-1, is a human orthologue of a product of Caenorhabditis elegance smg-1, one of seven smg genes involved in NMD. hSMG-1 phosphorylates hUPF1/SMG-2 in vivo and in vitro at specific serine residues in SQ motifs. hSMG-1 can associate with hUPF1/SMG-2 and other components of the surveillance complex. In particular, over expression of the PTC-dependent b-goblin mRNA degradation, whereas that of wild-type hSMG-1 enhances it. We also show that inhibitors of hSMG-1 induce the accumulation of truncated p53 proteins in human cancer cell lines with p53 PTC mutation. Taken together, we conclude that hSMG-1 plays a critical role in *D through the direct phosphorylation of hUPF1/SMG-2 in the evolutionally conserved mRNA surveillance complex. We also show that human homologues of C. elegance SMG-5 and SMG-7 form a stable complex that selectively associates with phosphorylated hUPF1 (P-hUPF1). The complex also associates with PP2A, resulting in its dephosphorylation. Overexpression of hSMG-5 mutants that remain able to interact with P-hUPF1, but cannot induce its dephosphorylation impair NMD, indicating that dephosphorylation of P-hUPF1 is required for NMD. We also show that P-hUPF1 forms distinct complexes containing different is forms of hUPF3A. We propose that sequential phosporylation and dephosphorylation of hUPF1 by hSMG-1 and PP2A, respectively, contribute to the assembly cycles of the mRNA surveillance complex.
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[Publications] Ohnishi, T., Yamashita, A., Kashima, I., Schell, T., Anders, K. R. Grimson, A., Hachiya, T., Matthias W. Hentze, M. W., Anderson, P., and Ohno, S.: "Phosphorylated hUPF1 selectively associates with hSMG5 and hSMG7 for PP2A-mediated dephosphorylation required for mammalian Nonsense-Mediated mRNA Decay."submitted for publication.
Description
「研究成果報告書概要(欧文)」より
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[Publications] Yamashita, A., Ohnishi, T., Kashima, I., Taya, Y. and Ohno, S.: "Human SMG-1, a novel phosphatidylinositol 3-kinase-related protein kinas, associates with components of the mRNA surveillance complex and is involved in the regulation of nonsense-mediated mRNA decay."Genes & Development 15. 2215-2228 (2001)
Description
「研究成果報告書概要(欧文)」より
