• Molecules and Cells
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• v.21 no.2
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• pp.251-260
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• 2006

During mitosis, genomic integrity is maintained by the proper coordination of anaphase entry and mitotic exit via mitotic checkpoints. In budding yeast, mitotic exit is controlled by a regulatory cascade called the mitotic exit network (MEN). The MEN is regulated by a small GTPase, Tem1p, which in turn is controlled by a two-component GAP, Bfa1p-Bub2p. Recent results suggested that phosphorylation of Bfa1p by the polorelated kinase Cdc5p is also required for triggering mitotic exit, since it decreases the GAP activity of Bfa1p-Bub2p. However, the dispensability of GEF Lte1p for mitotic exit has raised questions about regulation of the MEN by the GTPase activity of Tem1p. We isolated a Bfa1p mutant, $Bfa1p^{E438K}$, whose overexpression only partially induced anaphase arrest. The molecular and biochemical functions of $Bfa1p^{E438K}$ are similar to those of wild type Bfa1p, except for decreased GAP activity. Interestingly, in $BFA1^{E438K}$ cells, the MEN could be regulated with nearly wild type kinetics at physiological temperature, as well as in response to various checkpoint-activating signals, but the cells were more sensitive to spindle damage than wild type. These results suggest that the GAP activity of Bfa1p-Bub2p is responsible for the mitotic arrest caused by spindle damage and Bfa1p overproduction. In addition, the viability of cdc5-2 ${\Delta}bfa1 $ cells was not reduced by $BFA1^{E438K}$, suggesting that Cdc5p also regulates Bfa1p to activate mitotic exit by other mechanism(s), besides phosphorylation.

• The Korean Journal of Zoology
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• v.15 no.3
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• pp.95-100
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• 1972

Dose response and time dependence of unscheduled DNA synthesis induced by X-rays were measured to determine if any correlation exists between unscheduled DNA synthesis, modal chromosome number, chromosome exchange and mitotic activity in four mammalian cell strains. Unscheduled DNA synthesis occurred in all strains studied. The rate was dose-dependent and strain-specific. Only HeLa $S_3$ showed a staturated dose response after 4, 000 R, other cells were linearly proportional to dose increases. Time dependence of unscheduled DNA synthesis was completed within 2 hours after irradiation regardless of cell strains. Unscheduled DNA synthesis was not directly related to modal chromosome number, total exchange rate and mitotic activity. Mitotic activity and chromosome exchange were both dose-dependent, but the rates of them were inversely related.

• Biomedical Science Letters
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• v.17 no.3
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• pp.197-202
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• 2011

Mitosis count is one of the most helpful morphologic features for distinguishing pulmonary typical carcinoid (TC) from atypical carcinoid (AC). However, identifying areas of highest mitotic activity is tedious and time-consuming, and mitosis count may vary substantially among pathologists. Anti-phosphohistone H3 (PHH3) is an antibody that specifically detects histone H3 only when phosphorylated at serine 10 or serine 28, an event that is concurrent with mitotic chromatin condensation and not observed during apoptosis. In this study, immunohistochemical staining for PHH3 was performed to determine whether PHH3 was a reliable and objective mitosis-specific marker for pulmonary carcinoid tumors. Seventeen cases of surgically resected pulmonary carcinoid tumors (12 TCs and 5 ACs) were obtained and classified according to the 2004 World Health Organization classification. Mitotic counts determined by PHH3 correlated to ones determined by hematoxylin and eosin (H&E) staining; however, PHH3 mitotic counts (mean mitotic counts: 1 in TCs and 3.2 in ACs) were slightly higher than H&E mitotic counts (mean mitotic counts: 0.25 in TCs and 1.8 in ACs). The mitotic counts determined by experienced observer were more correlated to those determined by inexperienced observer with the PHH3-based method (R=0.968, P<0.001) rather than H&E staining (R=0.658, P<0.001). These results suggest that the PHH3 mitotic counting method was more sensitive and simple for detecting mitoses compared to traditional H&E staining. Therefore, PHH3 immunohistochemistry may contribute to more accurate and reproducible diagnosis of pulmonary carcinoid tumors and may be a valuable aid for administrating appropriate clinical treatment.

• BMB Reports
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• v.51 no.6
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• pp.261-262
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• 2018

Aurora B is an important kinase involved in dynamic cellular events in mitosis. Aurora B activity is controlled by several post-translational modifications (PTMs). Among them, E3 ubiquitin ligase-mediated ubiquitination plays crucial roles in controlling the relocation and degradation of Aurora B. Aurora B, ubiquitinated by different E3 ligases, moves to the exact site for its mitotic function during metaphase-anaphase transition and is then degraded for cell cycle progression at the end of mitosis. However, how the stability of Aurora B is maintained until its degradation has been poorly understood. Recently, we have found that USP35 acts as a deubiquitinating enzyme (DUB) for Aurora B and affects its stability during cell division, thus being involved in the regulation of mitosis. In this review, we discuss the USP35-mediated deubiquitination of Aurora B and the regulation of mitotic progression by USP35.

• Molecules and Cells
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• v.42 no.12
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• pp.840-849
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• 2019

The spatiotemporal mitotic processes are controlled qualitatively by phosphorylation and qualitatively by ubiquitination. Although the SKP1-CUL1-F-box protein (SCF) complex and the anaphase-promoting complex/cyclosome (APC/C) mainly mediate ubiquitin-dependent proteolysis of mitotic regulators, the E3 ligase for a large portion of mitotic proteins has yet to be identified. Here, we report c-Cbl as an E3 ligase that degrades DDA3, a protein involved in spindle dynamics. Depletion of c-Cbl led to increased DDA3 protein levels, resulting in increased recruitment of Kif2a to the mitotic spindle, a concomitant reduction in spindle formation, and chromosome alignment defects. Furthermore, c-Cbl depletion induced centrosome over-duplication and centriole amplification. Therefore, we concluded that c-Cbl controls spindle dynamics and centriole duplication through its E3 ligase activity against DDA3.

• Journal of Ginseng Research
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• v.46 no.3
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• pp.481-488
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• 2022

Background: Although the tumor-suppressive effects of ginsenosides in cell cycle have been well established, their pharmacological properties in mitosis have not been clarified yet. The chromosomal instability resulting from dysregulated mitotic processes is usually increased in cancer. In this study, we aimed to investigate the anticancer effects of ginsenoside Rg1 on mitotic progression in cancer. Materials and methods: Cancer cells were treated with ginsenoside Rg1 and their morphology and intensity of different protein were analyzed using immunofluorescence microscopy. The level of proteins in chromosomes was compared through chromosomal fractionation and Western blot analyses. The location and intensity of proteins in the chromosome were confirmed through immunostaining of mitotic chromosome after spreading. The colony formation assays were conducted using various cancer cell lines. Results: Ginsenoside Rg1 reduced cancer cell proliferation in some cancers through inducing mitotic arrest. Mechanistically, it inhibits the phosphorylation of histone H3 Thr3 (H3T3ph) mediated by Haspin kinase and concomitant recruitment of chromosomal passenger complex (CPC) to the centromere. Depletion of Aurora B at the centromere led to abnormal centromere integrity and spindle dynamics, thereby causing mitotic defects, such as increase in the width of the metaphase plate and spindle instability, resulting in delayed mitotic progression and cancer cell proliferation. Conclusion: Ginsenoside Rg1 reduces the level of Aurora B at the centromere via perturbing Haspin kinase activity and concurrent H3T3ph. Therefore, ginsenoside Rg1 suppresses cancer cell proliferation through impeding mitotic processes, such as chromosome alignment and spindle dynamics, upon depletion of Aurora B from the centromere.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.6
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• pp.3669-3676
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• 2013

Faithful transmission of genetic information depends on accurate chromosome segregation as cells exit from mitosis, and errors in chromosomal segregation are catastrophic and may lead to aneuploidy which is the hallmark of cancer. In eukaryotes, an elaborate molecular control system ensures proper orchestration of events at mitotic exit. Phosphorylation of specific tyrosyl residues is a major control mechanism for cellular proliferation and the activities of protein tyrosine kinases and phosphatases must be integrated. Although mitotic kinases are well characterized, phosphatases involved in mitosis remain largely elusive. Here we identify a novel variant of mouse protein tyrosine phosphatase containing domain 1 (Ptpcd1), that we named Ptpcd2. Ptpcd1 is a Cdc14 related centrosomal phosphatase. Our newly identified Ptpcd2 shared a significant homology to yeast Cdc14p (34.1%) and other Cdc14 family of phosphatases. By subcellular fractionation Ptpcd2 was found to be enriched in the cytoplasm and nuclear pellets with catalytic phosphatase activity. By means of immunofluorescence, Ptpcd2 was spatiotemporally regulated in a cell cycle dependent manner with cytoplasmic abundance during mitosis, followed by nuclear localization during interphase. Overexpression of Ptpcd2 induced mitotic exit with decreased levels of some mitotic markers. Moreover, Ptpcd2 failed to colocalize with the centrosomal marker ${\gamma}$-tubulin, suggesting it as a non-centrosomal protein. Taken together, Ptpcd2 phosphatase appears a non-centrosomal variant of Ptpcd1 with probable mitotic functions. The identification of this new phosphatase suggests the existence of an interacting phosphatase network that controls mammalian mitosis and provides new drug targets for anticancer modalities.

• The Korean Journal of Zoology
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• v.14 no.4
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• pp.175-180
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• 1971

The effects of X-irradiation on the mitotic activity, the chromosome aberration and the DNA synthetic pattern in synchronized human kidney cells treated with 5-AU were measured in the present experiment. When 5-AU was added, mitotic activity was markedly suppressed. After removal of the cells from the chemical, its activity proceeded synchronouly and reached peaks at hours 10. In 5-AU+100R groups, it was observed the X-ray caused mitotic delay, the irregularity of the time when mitotic peak appeared and the inhibiton of mitotic activity. In the control group, chromosome aerrations per cell was 0.030, whereas 0.147 in 5-AU treated group. In 5-AU+100R and 5-AU+200R groups, chromosome aberrations per cell were 0.583 and 0.669 respectively and the average chromosome aberrations per cell per R was 0.0035. 5-AU increased the frequency of labeled metaphases together with labeling intensity, and this is thought to be due to the accumulation of cells by 5-AU at S stage. On the contrary, X-ray decreased the labeling intensity and the frequency of labeled metaphases.

• Asian-Australasian Journal of Animal Sciences
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• v.2 no.3
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• pp.204-205
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• 1989

• Microbiology and Biotechnology Letters
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• v.50 no.3
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• pp.436-440
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• 2022

In this study, yeast artificial chromosome Insert (YAC) harboring genes which related xylan metabolism was constructed by using chromosome manipulation technique. For efficient chromosome manipulation, each splitting fragment (DNA module) required for splitting process was prepared and these DNA modules were transformed into Saccharomyces cerevisiae strain YKY164. By two-rounds chromosome splitting, yeast chromosome VII (1,124 kb) was split 887 kb-YAC, 45 kb-mini YAC and 198 kb-YAC and YKY183 strain containing 18 chromosomes was constructed. Splitting efficiency for chromosome manipulation was 50- 78% and expression level of foreign genes on 45 kb-mini YAC and enzyme activity were indistinguishable from that of the YKY164 strain. Furthermore, xylan-degraded products by recombinant enzymes were confirmed and mini-yeast artificial chromosome maintained stable mitotic stability without chromosome loss during 160 generations.