• Animal cells and systems
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• v.10 no.1
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• pp.1-6
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• 2006

Previous studies showed that Cdc7 kinase of Schizosaccharomyces pombe phosphorylated the minichromosome maintenance (Mcm) complex efficiently in the presence of spMcm10 protein. The biochemical properties of the phosphorylated Mcm complexes were examined to understand the activation mechanism of the Mcm complex by Cdc7 kinase. The phosphorylation of Mcm complex in the presence of spMcm10 by Cdc7 kinase did not affect the stability of the Mcm complex containing all six subunits, and the changes in the sedimentation properties were not observed after the phosphorylation. The reconstitution of the Mcm complex using the purified proteins showed that the phosphorylation of Mcm2 proteins did not affect the interactions between Mcm proteins. The phosphorylation of the Mcm2-7 complex at the same condition also did not activate the other biochemical activities such as DNA helicase and single stranded (ss) DNA binding activities. On the other hand, spMcm10 protein that was used for the stimulation of Mcm phosphorylation showed single stranded DNA binding activity, and inhibited the DNA helicase activity of the Mcm4/6/7 complex. These inhibitory effects were reduced by the addition of Cdc7 kinase, suggesting that the phosphorylation by Cdc7 kinase decreased the interactions between spMcm10 and the Mcm complex. Taken together, these results suggested that the phosphorylation by Cdc7 kinase alone is not sufficient for the remodeling and the activation of the Mcm complex, and the additional factors or the phosphorylations might be required for the activation of the Mcm complex.

• Journal of Haehwa Medicine
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• v.14 no.1
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• pp.201-211
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• 2005

Cdc2 kinase is a prototypical cyclin-dependent kinase critical for G2 to M phase cell cycle transition. Yet, its function in the nervous system is largely unknown. Here, we investigated possible role of Cdc2 in axonal regeneration using sciatic nerve system in rat. Cdc2 protein levels and activity were increased in the injured sciatic nerves 3 and 7 days after crush injury and then decreased to basal level 14 days later. Administration of Cdc2 kinase inhibitor roscovitine in vivo at the time of crush injury significantly inhibited axonal regeneration when regrowing axons were analyzed using retrograde tracers. Cdc2 protein levels in cultured Schwann cells which were prepared from sciatic nerves 7 days after crush injury were much higher compared with those from uninjured sciatic nerves, suggesting that Cdc2 protein expression was primarily induced in the Schwann cells. To further investigate Cdc2 function in Schwann cell, we examined changes in cultured Schwann cell proliferation and migration in culture system. Both the number of proliferating Schwann cells and the extent of neurite outgrowth from co-cultured DRG neurons were significantly decreased by Cdc2 inhibitor roscovitine treatment in DRG culture which was prepared from animals with sciatic nerve injury for 7 days. Also, Schwann cell migration in the injured sciatic nerve explant was significantly inhibited by roscovitine treatment. Taken together, the present data suggest that Cdc2 may be involved in peripheral nerve regeneration via Schwann cell proliferation and migration.

• BMB Reports
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• v.36 no.4
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• pp.421-425
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• 2003

The serine/threonine protein kinase family is a large and diverse group of enzymes that are involved in the regulation of multiple cellular pathways. Elevated kinase activity has been implicated in many diseases and frequently targeted for the development of pharmacological inhibitors. Therefore, non-radioactive antibody-based kinase assays that allow high throughput screening of compound libraries have been developed. However, they require a generation of antibodies against the phosphorylated form of a specific substrate. We report here a time-resolved fluorescence assay platform that utilizes a commercially-available generic anti-phosphothreonine antibody and permits assaying kinases that are able to phosporylate threonin residues on protein substrates. Using this approach, we developed an assay for Cdc7/Dbf4 kinase activity, determined the $K_m$ for ATP, and identified rottlerin as a non-ATP competitive inhibitor of this enzyme.

• BMB Reports
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• v.40 no.5
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• pp.805-813
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• 2007

Although MCM2 is obviously important for the initiation of eukaryotic DNA replication, its role in $O_2$ dependent regulation of replicon initiation is poorly understood. In this report, I analysed the changes of MCM2 during the transition from hypoxically suppressed replicon initiation to the burst of initiation triggered by reoxygenation in T24 cells. A high level of chromatin bound and nucleosolic MCM2 was found under the hypoxic replicon arrest. In contrast low cytosolic MCM2 was noticed. Recovery of $O_2$ induced phosphorylation and diminution of chromatin bound MCM2, whereas cytosolic MCM2 increased. The level of chromatin bound Cdc7 did not change significantly upon reoxygenation. However, after reoxygenation, significant phosphorylation of Cdc7 and an increase of coimmunoprecipitation with its substrate (MCM2) were observed. This provides a hint that reoxygenation may promote the kinase activity of Cdc7. These changes might be the critical factors in $O_2$ dependent regulation of replicon initiation. Moreover, phosphorylation of Cdc7 by Cdk2 can be observed in vitro, but seems to fail to regulate the level of chromatin bound Cdc7 as well as the changes of MCM2 in response to reoxygenation of hypoxically suppressed cells.

• Journal of Embryo Transfer
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• v.16 no.3
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• pp.223-231
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• 2001

The success of nuclear transplantation with mammalian oocytes depends critically on the potential of oocytes activation, which mainly caused to prevent the re-accumulation of maturation promoting factor (MPF). This study was conducted to compare the effect of combined treatment of lonomycin with a Hl-histone kinase inhibitor (dimethylaminopurine, DMAP) or cdc2 kinase inhibitor (sodium pyrophosphate, SPP) on activation of bovine oocytes. In vitro matured bovine oocytes with the first polar body (PB) and dense cytoplasm were assigned to 3 experimental groups. For activation treatment, oocytcs were exposed to 5 $\mu$M lonomycin for 5 min (Group 1), and followed by 1.9 mM dimethylaminopurine (DMAP) for 3 h (Group 2) or followed by 2 mM sodium pyrophosphate (SPP) for 3 h (Group 3). The activation effects in the three treatments and the control group (untreated) were judged by the extrusion of the second PB and formation of a pronucleus (PN). Differences among groups were analysed using one-way ANOVA after arc-sine transformation of proportional data. All three treatments led to high activation rates (90% to 95%), with significant difference from the control. However, the extrusion of the second PB and the rate of PN formation differed remarkably among treatments. In Group I and 3, about 95% of the oocytes had extruded the second polar body, but one PN had formed in a higher proportion of oocytes in Group 3 than in Group 1 (90% vs. 5%). In experiment 2, the rates of cleavage and development into blastocysts in Group 1 were significantly lower than those of Group 2 and 3 (8.7% and 0% vs. 50.5% and 11.6%, and 44.6% and 7.2%, respectively, P<0.05). In experiment 3, ~80% of parthenotes in Group 1 were developed with haploid chromosomal sets. However, when ionomycin was followed immediately by DMAP (Group 2). only 20% of parthenotes were haploid. In Group 3, combined treatment with ionomycin and SPP, the appearance of abnormal chromosomal tracts was significantly (P〈0.05) reduced and the proportion of haploid parthenotes was increased to 85% (17/20) than in Group 2. These results demonstrate that SPP acted as a cdc2 kinase inhibitor and formed the haploidy in oocyte activation. Thus, the present study suggests that cdc2 kinase inhibitor, such as sodium pyrophosphate, may have an effective role in oocyte activation for the production of cloned embryos/animals by nuclear transplantation.

• Proceedings of the Zoological Society Korea Conference
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• 2003.08a
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• pp.57-57
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• 2003

No Abstract, See Full Text

• Reproductive and Developmental Biology
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• v.33 no.2
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• pp.85-91
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• 2009

In this study, in vitro maturation system using fetal bovine serum (FBS) or porcine follicular fluid (pFF) was investigated to produce comparable oocytes to those derived from in vivo. Control group of oocytes was cultured in TCM 199 supplemented with 0.1% polyvinyl alcohol (PVA). Other three groups of oocytes were cultured in TCM 199 supplemented with 10% FBS, 10% pFF or 5% FBS + 5% pFF, respectively. After 44 h maturation, oocytes with the first polar body were activated with two electric pulses (DC) of 1.2 kv/cm for 30 ${\mu}sec$. Also, matured oocytes of four groups were reconstructed and fused. Reconstructed embryos were cultured in PZM-3 under 5% $CO_2$ in air at $38.5^{\circ}C$ for 6 days. The oocytes matured in the medium supplemented with FBS or/and pFF showed significantly higher maturation rates (64.0 vs. 73.9 to 85.2%). In PA embryos, cleavage rates (89.7 vs. 77.1 to 86.6%) and blastocysts rates (30.0 vs. 16.2 to 26.2%) were significantly higher in pFF group (p<0.05). In NT embryos, there was no difference among treatments in cleavage rate, but the blastocyst rates (28.5 vs. 15.5 to 24.6%) were significantly higher in pFF group (p<0.05). The apoptosis rate was significantly higher (p<0.05) in the control than other groups (10.8 vs. 4.9 to 8.2% for PA, 3.1 vs. 0.5 to 1.3% for NT). In order to select the comparable oocyte to in vivo oocytes, each group of oocytes was stained with Brilliant cresyl blue (BCB) after 42h maturation. The matured oocytes were separated according to color of cytoplasm; stained group (BCB+) and unstained group (BCB-). The oocytes matured in the presence of FBS or/and pFF showed significantly higher staining rates (70.3 to 72.7 vs. 35.1%) (p<0.05). To verify the fact that the supplementation of FBS or/and pFF can increase the maturation rates, cdc2 kinase activity, the catalytic subunit of MPF, was determined. The cdc2 kinase activity of the oocytes matured in the medium supplemented with FBS or/and pFF was significantly higher than control group (6.7 to 9.3 vs. 3.8). In conclusion, the supplementation of FBS or/and pFF can support in vitro maturation rate of porcine oocytes through the increment of cdc2 kinase activity level in the cytoplasm.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.7
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• pp.1045-1050
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• 2002

The aims of this study were to detect spontaneously occurring apoptosis in cultured porcine ovarian cells, to examine the role of growth hormone (GH), tyrosine kinase (TK), protein kinase G (PKG) and cyclin-dependent kinase (CDK) in the control of this process, and to determine whether the effect of GH on apoptosis is mediated by TK-, PKG- and cdc2-dependent intracellular mechanisms. We studied the action of pGH (10 ng/ml), blockers of TK (genistein, lavendustin, both 100 ng/ml), PKG (Rp-Br-PET-cGMPS, 50 nM; KT5823, 100 ng/ml) and CDK (olomoucine, $1{\mu}g/ml$), as well as combinations of GH with these blockers, on the onset of apoptosis in cultured granulosa cells isolated from antral (3-6 mm) porcine follicles. The functional characteristics of an early apoptotic event, DNA fragmentation, were determined using terminal deoxynucleotidyltransferase (TdT)-mediated dUTP nick end labelling (TUNEL), whilst morphological signs of advanced apoptosis such as pyknosis, chromatin marginalization, shrinkage and fragmentation of nucleus, were detected using routine light microscopy. After culture, some ovarian granulosa cells exhibited DNA fragmentation, which in some cases was associated with morphological apoptosis-related changes (pyknosis, shrinkage and fragmentation of the nucleus). GH significantly reduced the proportion of TUNEL-positive cells. Neither TK nor CDK blockers when given alone, significantly affected the percentage of TUNEL-positive cells although both PKG blockers significantly increased this index. Furthermore, TK and PKG blockers given together with GH, prevented or reversed the inhibitory effect of GH on apoptosis, whilst the CDK blocker olomoucine promoted it. These observations demonstrate apoptosis in porcine ovaries and suggest the involvement of GH, TK, PKG and CDK in the control of this process. They also suggest that the effect of GH on ovarian apoptosis is mediated or regulated by multiple signalling pathways including TK-, PKG- and CDK-dependent intracellular mechanisms.

• Reproductive and Developmental Biology
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• v.31 no.2
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• pp.77-82
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• 2007

This study was conducted to investigate the effects of oocyte maturational age and activation condition on in vitro development of porcine parthenogenetic embryos (parthenotes). Porcine follicular oocytes were matured in vitro for 30 to 44 hr. Maturation rate was examined during in vitro maturation (IVM) every 2 hr interval. The cdc2 kinase activity was measured at 36 and 44 hr of IVM. Some oocytes were activated at 36 or 44 hr of IVM by three different conditions; 1) single electric stimulation (1.5 kV/cm for $30{\mu}sec$; ES), 2) double electric stimulations (1.5 kV/cm for $30{\mu}sec$, followed by 1.0 kV/cm for $50{\mu}sec$ after 1 hr; ES+ES) or 3) ES+ES followed by culture in 6-dimethlyaminopurine (6-DMAP) for 4 hr (ES+ES+D), and cultured for 6-7 days. Maturation rate was significantly increased as culture period was increased to 36 hr (66.9%, p<0.05), and then gradually increased to 87.1% at 44 hr of IVM. The cdc2 kinase activity was decreased (p<0.05) with culture period prolonged from 36 hr to 44 hr. Lower blastocyst formation rate (4.3%, p<0.05) were obtained by ES in 36 hr-matured oocytes compared to other treatments (16.5 and 20.5%) in the same age and the same treatment in 44 hr-matured oocytes (15.0%). High blastocyst formation rate (23.6%) was obtained by ES+ES+D in 44 hr-matured oocytes (p<0.05). These results demonstrate that porcine oocyte activation and in vitro development of parthenotes can be affected by interactions between oocyte maturational age and activation condition.

• Biomolecules & Therapeutics
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• v.20 no.6
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• pp.513-519
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• 2012

Although the immense efforts have been made for cancer prevention, early diagnosis, and treatment, cancer morbidity and mortality has not been decreased during last forty years. Especially, lung cancer is top-ranked in cancer-associated human death. Therefore, effective strategy is strongly required for the management of lung cancer. In the present study, we found that novel daphnane diterpenoids, yuanhualine (YL), yuanhuahine (YH) and yuanhuagine (YG) isolated from the flower of Daphne genkwa (Thymelaeaceae), exhibited potent anti-proliferative activities against human lung A549 cells with the $IC_{50}$ values of 7.0, 15.2 and 24.7 nM, respectively. Flow cytometric analysis revealed that the daphnane diterpenoids induced cell-cycle arrest in the G0/G1 as well as G2/M phase in A549 cells. The cell-cycle arrests were well correlated with the expression of checkpoint proteins including the up-regulation of cyclin-dependent kinase inhibitor p21 and p53 and down-regulation of cyclin A, cyclin B1, cyclin E, cyclin dependent kinase 4, cdc2, phosphorylation of Rb and cMyc expression. In the analysis of signal transduction molecules, the daphnane diterpenoids suppressed the activation of Akt, STAT3 and Src in human lung cancer cells. The daphnane diterpenoids also exerted the potent anti-proliferative activity against anticancer-drug resistant cancer cells including gemcitabine-resistant A549, gefitinib-, erlotinib-resistant H292 cells. Synergistic effects in the growth inhibition were also observed when yuanhualine was combined with gemcitabine, gefitinib or erlotinib in A549 cells. Taken together, these findings suggest that the novel daphnane diterpenoids might provide lead candidates for the development of therapeutic agents for human lung cancers.