| Project/Area Number |
10044292
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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 |
Molecular biology
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| Research Institution | Hiroshima University |
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Principal Investigator |
SHIMIZU Noriaki Hiroshima University, Faculty of Integrated Arts and Science, Associate Professor, 総合科学部, 助教授 (10216096)
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| Co-Investigator(Kenkyū-buntansha) |
M.WAHL Jeoff The Salk Institute for Biological Studie, Professor
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1999: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1998: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | extrachromosomal DNA / Micronucleus / Gene Amplifrceatlon / Mitosis / Double Minutes / Lamin / Elimination / Gene Amplification / Double Minute / Nuclear structure / Extrachromosomal element / DNA replication / DM elimination |
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| Research Abstract |
The amplified oncogenes found in human cancer cells usually reside on extrachromosomal double minutes chromatin (DMs). DMs are composed with autonomously replicating circular DNA molecule of few megabase-pairs in size. We previously found that the elimination of DMs from cancer cells led to the reversion of cancer cell phenotypes and the cellular differentiation. DMs were eliminated from the cells through the selective incorporation into the micronuclei formed at cytoplasm. In this study, we accomplished to clarify the intracellular behavior and the extracellular elimination of DMs. Namely. DMs are normally segregated to daughter cells by adhering to the mitotic chromosomes. We showed that the treatment of micronuclei inducer, hydroxyurea, at S-phase led to the detachment of DMs from the chromosomes at the following anaphase. This detachment was most probably caused by the introduction of DNA double strand break in DM. The detached DMs Were left at the cytoplasm as aggregated form. At G1-phase, most of the cytoplasmic aggregates of DMs Were devoid from lamin protein, which was known to be a major constituent of nuclear lamina, and attached to the nucleus from the outside. When the cells entered the next S-phase, the cytoplasmic DMs Were entrapped by lamin which resulted in the nuclear bud-shaped structure followed by the completion of micronucleation. Our results also indicated that at least a portion of micronuclei thus formed were extruded from the cells which resulted in the elimination of DMs from the cancer cells.
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