| 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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| Project Status |
Completed (Fiscal Year 2002)
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| Budget Amount *help |
¥15,200,000 (Direct Cost: ¥15,200,000)
Fiscal Year 2002: ¥6,600,000 (Direct Cost: ¥6,600,000)
Fiscal Year 2001: ¥8,600,000 (Direct Cost: ¥8,600,000)
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| Keywords | nonsense mutation / mRNA degradation / mRNA surveillance / NMD / protein kinas / PIK remitted protein kinas / RNA helices / ATPase / mRNA分離 / リン脂質キナーゼ / ATPアーゼ |
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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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