Inhibition of portein α/β-dependent nuclear import in Xenopus oocytes

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17570155
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Cell biology
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: IWABUCHI Mari Tokyo Institute of Technology, Graduate School of Bioscience & Biotechnology, Assistant professor(COF) (40275350)
• Project Period (FY): 2005 – 2006
• Keywords: importin α / nuclear transport / ooeyte / annulate lamellae / cell-death

Research Abstract

Full-grown animal oocytes are characterized by the presence in the cytoplasm of well-developed annulate lamellae (AL), a membranous organelle containing the nuclear pore complex (NPC)-like structure (ALPC) and nucleoporins. Although abundant ALPC in the cytoplasm may be involved in the regulation for nuclear transport of karyophilic molecules, physiological roles of AL have long been unclear. We found that in full-grown Xenopus oocytes arrested at G2/meiosis I boundary, the majority of importin α, but not importin β, is tethered to AL. This depletion of importin α in oocytes makes nuclear import of classical NLS (cNLS)-cargos less active than that in matured eggs. Injection of importin α into oocytes accelerates cNLS-cargo import, but surprisingly, the injected oocytes suffer degeneration leading to cell-death. We found that elevated level of importin α induced processing of both cytoskeletal and nuclear proteins such as alpha-fodrin and lamins, which was consequence of caspase activation. These results indicate that importin α needs to be immobilized by AL for full-grown oocytes to survive during the long-lasting arrest in G2 phase, providing the first evidence for an active role of AL in oocytes.

Research Products

• [Journal Article] Oocyte extracts for the study of meiotic M-M transition (2006)
  • Author(s): Ohsumi, K., Yamamoto, T.M.and Iwabuchi, M.
  • Journal Title: Methods in Molecular Biology 322 Pages: 445-458
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Oocyte extracts for the study of meiotic M-M transition. (2006)
  • Author(s): Ohsumi, K., Yamamoto, T. M, Iwabuchi, M.
  • Journal Title: Methods in Molecular Biology 322 Pages: 445-458
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] APC/C-Cdc20-mediated degradation of cyclin B participates in CSF arrest inunfertilized Xenopus eggs (2005)
  • Author(s): Yamamoto, T, M., Iwabuchi, M., Ohsumi, K., and Kishimoto, T.
  • Journal Title: Developmental Biology 279 Pages: 345-355
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] Nucleosome assembly protein-1 is a linker histone chaperone in Xenopus eggs (2005)
  • Author(s): Shintomi, K., Iwabuchi, M., Saeki, H., Ura, K., Kishimoto, T.and Ohsumi, K
  • Journal Title: Proc.Natl.Acad.Sci.U.S.A. 102 Pages: 8210-8215
  • Description: 「研究成果報告書概要(和文)」より
• [Journal Article] APC/C-Cdc20-mediated degradation of cyclin B participates in CSF arrest in unfertilized Xenopus eggs. (2005)
  • Author(s): Yamamoto, T, M., Iwabuchi, M., Ohsumi, K., Kishimoto, T.
  • Journal Title: Developmental Biology 279 Pages: 345-355
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Nucleosome assembly protein-i is a linker histone chaperone in Xenopus eggs. (2005)
  • Author(s): Shintomi, K., Iwabuchi, M., Saeki, H., Ura, K., Kishimoto, T. Ohsumi, K.
  • Journal Title: Proc. Nat!. Acad. Sci.(USA). 102 Pages: 8210-8215
  • Description: 「研究成果報告書概要(欧文)」より