| Project/Area Number |
15390097
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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 |
General medical chemistry
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| Research Institution | Ehime University |
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Principal Investigator |
HIGASHIYAMA Shigeki Ehime University, School of Medicine, Professor, 医学部, 教授 (60202272)
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| Co-Investigator(Kenkyū-buntansha) |
MORIMOTO Chie Ehime University, School of Medicine, Instructor, 医学部, 助手 (10332826)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 2004: ¥5,200,000 (Direct Cost: ¥5,200,000)
Fiscal Year 2003: ¥10,300,000 (Direct Cost: ¥10,300,000)
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| Keywords | HB-EGF / Shedding / Transcriptional repressor / PLZF / EGF family / metalloprotease / gene regulation / shedding / repressor |
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| Research Abstract |
Heparin-binding EGF-like growth factor(HB-EGF) is initially synthesized as a type I transmembrane protein (proHB-EGF). The proHB-EGF is shed by specific metalloproteases, releasing the N-terminal fragment into the extracellular space as a soluble growth factor (HB-EGF) and the C-terminal fragment (HB-EGF-C) into the intracellular space, where it prevents transcriptional repression by the promyelocytic leukemia zinc finger protein (PLZF). The goal of the present study was to characterize regulation of proHB-EGF shedding and study its temporal variations in HB-EGF-C localization throughout the cell cycle. Quantitative combination analyses of cell surface proHB-EGF and HB-EGF in conditioned medium showed that proHB-EGF shedding occurred during the G1 cell cycle phase. Laser scanning cytometry revealed that HB-EGF-C was internalized into the cytoplasm during the late G1 phase and accumulated in the nucleus beginning in the S phase. Subsequent nuclear export of PLZF occurred during the late S phase. Further, HB-EGF-C was localized around the centrosome following breakdown of the nuclear envelope and was localized to the interzonal space with chromosome segregation in the late M phase. Temporal variations in HB-EGF localization throughout the cell cycle were also characterized by time-lapse imaging of cells expressing YFP-tagged proHB-EGF, and these results were consistent with those obtained in cytometry studies. Furthermore, we identified BCL-6 and BAZF as transcriptional repressors targeted by HB-EGF-C. These results indicate that proHB-EGF shedding and subsequent HB-EGF-C signaling are related with progression of the cell cycle and may provide a clue to understand the unique biological significance of non-receptor-mediated signaling of proHB-EGF in cell growth.
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