| Project/Area Number |
16591280
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General surgery
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| Research Institution | St.Marianna University School of Medicine |
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Principal Investigator |
OHTA Tomohiko St.Marianna University School of Medicine, Department of Surgery, Associate Professor, 医学部, 助教授 (60233136)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2005: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2004: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | BRCA1 / BARD1 / familial breast cancer / ubiquitin ligase / RPB8 / RING finger / nucleophosmin / Nucleophosmin |
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| Research Abstract |
I have discovered in 2001 that BRCA1 constituted a RING heterodimer type ubiquitin ligase with BARD1. In this study I further investigated the substrates of BRCA1 to elacidate how the activity contributed the BRCA1's ability to maintain the chromosomal stability. I identified several substrates by our original screen methods. Among them I have investigated nucleophosmin/B23 (NPM) in 2004. BRCA1-BARD1 interacted with and polyubiquitinated NPM in vivo and in vitro. The polyubiquitination was non-traditional Lys-6-linked type, and therefore NPM was not degraded by the modification and instead stabilized. BRCA1-BARD1 and NPM were co-localized over the chromosomal surface during mitosis when NPM was actually ubiquitinated in vivo. I propose the lack of NPM ubiquitination could be the basis of centrosome hyper amplification and aneuploidy caused by BRCA1 deficiency. I next analyzed another candidate substrate, RPB8, in 2005. BRCA1-BARD1 interacted with and polyubiquitinated RPB8 in vivo and in vitro. The ubiquitination of RPB8 was observed 10 minutes after UV irradiation in HeLa cells stably expressing FLAG-tagged RPB8, and this ubiquitination was abolished by BRCA1 knockdown by siRNA. Interestingly HeLa cells stably expressing ubiquitin-resistant RPB8 mutant exhibited UV hypersensitivity. The results suggested that BRCA1 regulates chromosomal stability by transcription-coupled DNA repair through ubiquitination of RPB8.
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