1996 Fiscal Year Final Research Report Summary
Mechanisms of Sister Chromatid Separation in the Cell Division Cycle
| Project/Area Number |
05102004
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| Research Category |
Grant-in-Aid for Specially Promoted Research
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| Allocation Type | Single-year Grants |
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| Review Section |
Biological Sciences
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
YANAGIDA Mitsuhiro Kyoto University Faculty of Science Assistant, 大学院・理学研究科, 教授 (80025428)
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| Co-Investigator(Kenkyū-buntansha) |
NAKASEKO Yukinobu Kyoto University Faculty of Science Professor, 大学院・理学研究科, 助手 (30231468)
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| Project Period (FY) |
1993 – 1996
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| Keywords | cell cycle / sister chromatid separation / chromosome condensation / cyclins / centromere / proteolysis / stress / M phase |
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| Research Abstract |
During the course of our four-year research project 40 original papers were published while 5 are submitted. There are two major problems in sister chromatid separation in mitosis, namely, coupling with cell cycle regulation and fidelity mechanisms to ensure correct sister chromatid separation. In the present study, following important discoveries and significant advancement in understanding were made. We found that Cut2 specifically required for sister chromatid separation undergoes proteolysis in anaphase with the machinery identical to that for cyclin B destruction. Cut2 contains the destruction box sequences similar to that of mitotic cyclins required for ubiquitin dependent proteolysis. These results clearly show that proteolysis promotes mitotic exit and sister chromatid separation by destruction of cyclin B and Cut2. Cut2 forms a large complex with Cut1, and the actual role of the complex is under an intensive investigation. The above results indicate that regulation of the 20S
… More
APC/cyclosome containing ubiquitin ligase is crucially important for understanding sister chromatid separation. Four subunits of APC have been identified in this laboratory and one of them, Cut4, was found to be particularly important. Cut4 responds to stress, heavy metal, cyclic AMP/PKA inactivation pathway at the level of 20S assembly, and perhaps determines whether the onset of anaphase should be triggered. The heteromeric complex of Cut3 and Cut14 which were essential for chromosome condensation was purified and examined for their molecular activity. We found that the complex has very strong DNA annealing activity. The individual subunits and the mutant complex had only reduced activities. There results strongly suggested that single stranded DNA regions might be inhibitory in chromosome condensation. Indeed chromatin in mutatnuclei contained abundant S1-nuclease sensitive sites. Hence resolving single stranded regions in nuclear chromatin seems to be prerequisite for chromosome condensation. We show that Mis6 protein required for equal segregation of chromosomes locates at the centromeres throughout the cell cycle and promotes bidirectional orientations of the sister centromeres in metaphase. Less
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