| Project/Area Number |
12213097
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Review Section |
Biological Sciences
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| Research Institution | Kyushu University |
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Principal Investigator |
NAKAYAMA Keiichi Kyushu University, Medical Institute of Bioregulation, Department of Molecular and Cellular Biology, Professor, 生体防御医学研究所, 教授 (80291508)
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| Co-Investigator(Kenkyū-buntansha) |
畠山 鎮次 九州大学, 生体防御医学研究所, 助教授 (70294973)
北川 雅敏 九州大学, 浜松医科大学・医学部, 教授 (50294971)
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| Project Period (FY) |
2000 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥56,200,000 (Direct Cost: ¥56,200,000)
Fiscal Year 2004: ¥11,700,000 (Direct Cost: ¥11,700,000)
Fiscal Year 2003: ¥11,700,000 (Direct Cost: ¥11,700,000)
Fiscal Year 2002: ¥12,000,000 (Direct Cost: ¥12,000,000)
Fiscal Year 2001: ¥10,800,000 (Direct Cost: ¥10,800,000)
Fiscal Year 2000: ¥10,000,000 (Direct Cost: ¥10,000,000)
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| Keywords | Cell Cycle / CDK inhibitor / p27 / ubiquitin / SCF complex / Skp2 / KPC / タンパク分解 / ユビキチンリガーゼ / CRM1 / ユビキチン化 / G0-G1移行期 / ノックアウトマウス / RING finger / サイクリンE / p27Kip1 |
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| Research Abstract |
We have studied the mechamism underlying the regulation of the abundance of the CDK inhibitor p27. p27 is degraded at the GO-G1 transition, and its abundance remains low during cell proliferation. The SCF/Skp2 ubiquitin ligase complex has been thought to play a critical role in p27 degradation. However, analysis of Skp2-deficient mice revealed that degradation of p27 at the GO-G1 transition proceeds normally in Skp2-/-cells, whereas p27 proteolysis during S-G2 phases is impaired in these Skp2-deficient cells. These results suggested the presence of Skp2-independent pathway to control ubiquitination of p27 at the GO-G1 transition. Using in vitro ubiquitylation assay, we biochemically purified a complex consisting of two proteins, designated KPC (Kip1 ubiquitylation Promoting Complex)1 and KPC2. Given that KPC1/2 are localized in the cytoplasm, nuclear export of p27 seems to precede the ubiquitination by KPC1/2. Overexpression of wild-type KPC1/2 in mammalian cells promotes the degradation of p27, whereas expression of dominant-negative mutant KPC 1/2 delayed the degradation. Depletion of KPC1 by RNA interference also inhibited p27 degradation. These data suggest that KPC 1/2 ubiquitin ligase complex controls the degradation of p27 at the GO-G1 transition, whereas the major function of Skp2 may be the regulation of progression from G2 to M phase by mediating the degradation of p27.
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