• BMB Reports
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• v.44 no.3
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• pp.147-157
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• 2011

The meiotic process from the primordial stage to zygote in female germ cells is mainly adjusted by post-transcriptional regulation of pre-existing maternal mRNA and post-translational modification of proteins. Several key proteins such as the cell cycle regulator, Cdk1/cyclin B, are post-translationally modified for precise control of meiotic progression. The second messenger (cAMP), kinases (PKA, Akt, MAPK, Aurora A, CaMK II, etc), phosphatases (Cdc25, Cdc14), and other proteins (G-protein coupled receptor, phosphodiesterase) are directly or indirectly involved in this process. Many proteins, such as CPEB, maskin, eIF4E, eIF4G, 4E-BP, and 4E-T, post-transcriptionally regulate mRNA via binding to the cap structure at the 5' end of mRNA or its 3' untranslated region (UTR) to generate a closed-loop structure. The 3' UTR of the transcript is also implicated in post-transcriptional regulation through an association with proteins such as CPEB, CPSF, GLD-2, PARN, and Dazl to modulate poly(A) tail length. RNA interfering is a new regulatory mechanism of the amount of mRNA in the mouse oocyte. This review summarizes information about post-transcriptional and post-translational regulation during mouse oocyte meiotic maturation.

• Radiation Oncology Journal
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• v.19 no.2
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• pp.146-152
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• 2001

Purpose : To investigate the regulation of apoptosis and cell cycle in mouse brain irradiation. Materials and Methods : 8-week old male mice, C57B1/6J were given whole body $\gamma-radiation$ with a single dose of 25 Gy using Cobalt 60 irradiator. At different times 1, 2, 4, 8 and 24hr after irradiation, mice were killed and brain tissues were collected. Apoptotic cells were scored by TUNEL assay. Expression of p53, Bcl-2, and Bax and cell cycle regulating molecules; cyclins Bl, Dl, E and cdk2, cdk4, $p34^{cdc2}$ were analysed by Western blotting. Cell cycle was analysed by Flow cytometry. Results : The peak of radiation induced apoptosis is shown at 8 hour after radiation. With a single 25 Gy irradiation, the peak of apoptotic index in C57B1/6J is $24.0{\pm}0.25$ (p<0.05) at 8 hour after radiation. Radiation upregulated the expression of p53/tubulin, Bax/tubulin, and Bcl-2/tubulin with 1.3, 1.1 and 1.45 fold increase, respectively were shown at the peak level at 8 hour after radiation. The levels of cell cycle regulating molecules after radiation are not changed significantly except cyclin D1 with 1.3 fold increase. Fractions of Go-Gl, G2-M and S phase in the cell cycle does not specific changes by time. Conclusion : In mouse brain tissue, radiation induced apoptosis is particularly shown in a specific area, subependyma. These results and lack of radiation induced changes in cell cycle ofter better understanding of radiation response of noraml brain tissue.

• Journal of Physiology & Pathology in Korean Medicine
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• v.25 no.5
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• pp.857-862
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• 2011

The purpose of this study is to investigate the anti-proliferative mechanism by Trichosanthes kirilowii (TCK) in MCF-7 human breast carcinoma cell. In this study, we used human breast cancer cell line, Michigan cancer foundation-7 cells (MCF-7 cells). They were co-incubated with 30~200 ${\mu}g$/ml TCK for 48 hours, and cell viability was measured by Water-soluble tetrazolium salt-1 (WST-1) assay. After MCF-7 cells were exposed to 60 ${\mu}g$/ml of TCK for 0, 3, 6, 12, 24, 48 hours, We performed flow analysis cytometry sorting(FACS) and western blot analysis. We investigated the effect of dose-dependent cell growth inhibition by TCK, which could be proved by WST-1 assay. Also, flow cytometry analysis showed that TCK increased percentage of subG1 phase and G2/M phase cell cycle. In addition, TCK induced apoptosis through the expression of caspase-9, -3 and poly(ADP-ribose) polymerase(PARP) activation. Moreover, we showed that ATM-dependent G2/M phase arrest by DNA damage and phosphorylation of chk2, cdc25C, cdc2(Tyr15). Taken together, these results suggest that by G2/M phase arrest through DNA damage and inducing of apoptosis through intrinsic pathway, TCK may have potential tumor suppressor in breast cancer.

• BMB Reports
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• v.44 no.5
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• pp.352-357
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• 2011

The effect of human MutY homolog (hMYH) on the activation of checkpoint proteins in response to hydroxyurea (HU) and ultraviolet (UV) treatment was investigated in hMYH-disrupted HEK293 cells. hMYH-disrupted cells decreased the phosphorylation of Chk1 upon HU or UV treatment and increased the phosphorylation of Cdk2 and the amount of Cdc25A, but not Cdc25C. In siMYH-transfected cells, the increased rate of phosphorylated Chk1 upon HU or UV treatment was lower than that in siGFP-transfected cells, meaning that hMYH was involved in the activation mechanism of Chk1 upon DNA damage. The phosphorylation of ataxia telangiectasia and Rad3-related protein (ATR) upon HU or UV treatment was decreased in hMYH-disrupted HEK293 and HaCaT cells. Co-immunoprecipitation experiments showed that hMYH was immunoprecipitated by anti-ATR. These results suggest that hMYH may interact with ATR and function as a mediator of Chk1 phosphorylation in response to DNA damage.

• Proceedings of the Korean Society of Toxicology Conference
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• 2002.05a
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• pp.81-81
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• 2002

The recent development of cDNA microarray or cDNA chip technology has made it possible to analyze the expression of thousands of genes at once. In present study, we made radioresistant clones (#1 and #4) from NIH3T3 cells which are not tumorigenic and we identified 4 genes using microarray system, cdk6, cdc25B, mdm-2 and nidogene, which were altered in radiaiton resistanct NIH3T3 cells.(omitted)

• Microbiology and Biotechnology Letters
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• v.29 no.3
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• pp.181-185
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• 2001

The naturally occurring chemical indole-3-carbinol (13C), found in vegetables of the Brassica genus, is a promising anticancer agent that was shown previ- ously to induce a Gl cell cycle arrest of human breast cancer cell lines, independent of estrogen receptor signaling. The anticancer activity of 13C and the possible mechanisms of its action were explored in a human hepatocellular carcinoma cell line, HepG2. Treatment of HepG2 cells with 13C suppressed the growth of the cells. The growth sup- pression caused by 13C ($IC_{50}$/: 444$\mu$M) was found to be partially due to its ability to stop the cell cycle in HepG2 cells. Western blot analysis for the Gl phase artiest demonstrated that the expression-levels of cyclin-dependent kinase (Cdk4, Cdk6) and cyclic D were reduced strongly after treatment of Hep72 cells with 13C (4007M) for 24- 72 hrs. Furthermore, I3C selectively abolished the expression of Cdk6 in a dose- and time-dependent manner, and accordingly, inhibited the phosphorylation of retinoblastoma. Interestingly, after the HepG2 cells reached their max- imal growth arrest, the level of the p21, a well-known Cdk inhibitor, increased significantly. Therefore, it could be considered that the Gl arrest of HepG2 cells treated with 13C was due to the indirect inhibition of Cdk4/6 activities by p21 Western blot analysis for G2/M phase arrest of demonstrated the levels of Cdc2 and cyclin Bl werer reduced dramatically after the treatment of HepG2 cells with 13C ($40\mu$M) for 24-72 hrs. flow cytometry of propidium iodide-stained HepG2 cells revealed that 13C induces a Gl (53%,72hr incubation) and G2 (25%,24hr incubation) cell cycle arrest. Thus, our observations have uncovered a previously undefined antiproliferative pathway for r3C that implicates Cdk4/6 and Cdc2 as a target for cell cycle control in human HepG2 cells. However, the 13C-medi- ated cell cycle arrest and repression of Cdk4/6 production did not affect the apoptotic induction of HepG2 cell.

• Journal of Life Science
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• v.24 no.1
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• pp.92-97
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• 2014

Cordycepin, an active component originally isolated from the traditional medicine Cordyceps militaris, is a derivative of the nucleoside adenosine, which has been shown to possess a number of pharmacological properties, including antioxidant and anti-inflammatory activities, immunological stimulation, and antitumor effects. This study was conducted on cultured human prostate carcinoma LNCap cells to elucidate the possible mechanisms by which cordycepin exerts its anticancer activity, which, until now, has remained poorly understood. Cordycepin treatment of LNCap cells resulted in dose-dependent inhibition of cell growth and the induction of apoptotic cell death as detected by an MTT assay, cleavage of poly ADP-ribose polymerase, and annexin V-FITC staining. Flow cytometric analysis revealed that cordycepin resulted in G2/M arrest in cell cycle progression and downregulation of cyclin B1 and cyclin A expression in a concentration-dependent manner. Moreover, the incubation of cells with cordycepin caused a striking induction in the expression of the cyclin-dependent kinase (CDK) inhibitor p21Waf1/Cip1 without affecting the expression of the tumor suppressor p53. It also resulted in a significant increase in the binding of CDK2 and CDC2 to p21. These findings suggest that cordycepin-induced G2/M arrest and apoptosis in human prostate carcinoma cells is mediated through p53-independent upregulation of the CDK inhibitor p21.

• Journal of Life Science
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• v.20 no.4
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• pp.519-527
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• 2010

Paclitaxel is known as a potent inhibitor of microtubule depolymerization. It leads to mitotic arrest and cell death by stabilizing the spindle in various cell types. Here, we investigated the effects of paclitaxel on the proliferation and cell death of rabbit articular chondrocytes. Paclitaxel inhibited proliferation in a dose- and time- dependent manner, determined by MTT assay in rabbit articular chondrocytes. We also established paclitaxel-induced G2/M arrest by fluorescent activated cell sorter (FACS) analysis. Paclitaxel increased expression of cyclin B, p53 and p21, while reducing expression of cdc2 and cdc25C in chondrocytes, as detected by Western blot analysis. Interestingly, paclitaxel showed the mitotic catastrophe that leads to abnormal nucleus division and cell death without DNA fragmentation through activation of caspase. Cell death by mitotic catastrophe in cells treated with paclitaxel was suppressed by inhibiting G1/S arrest with 2 mM thymidine. These results demonstrate that paclitaxel induces cell death via mitotic catastrophe without activation of casepase in rabbit articular chondrocytes.

• Molecular & Cellular Toxicology
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• v.2 no.3
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• pp.159-165
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• 2006

To determine the anticancer effect of D-amygdalin (D-mandelinitrole-${\beta}$-D-gentiobioside) in human chronic myeloid leukemia cells K562, we profiled the gene expression between amygdalin treatment and control groups. Through 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, the cytotoxicity of D-amygdalin was $57.79{\pm}1.83%$ at the concentration of 5 mg/mL for 24 h. We performed cDNA microarray analysis and compared the gene expression profiles between D-amygdalin (5 mg/mL, 24 h) treatment and control groups. Among the genes changed by D-amygdalin, we paid attention to cell cycle-related genes, and particularly cell cycle regulator genes; because arrest of cell cycle processing was ideal tactic in remedy for cancer. In our data, expressions of cyclin-dependent kinase inhibitor 1B (p27, Kip1) (CDKN1B), ataxia telangiectasia mutated (includes complementation groups A, C, and D) (ATM), cyclin-dependent kinase inhibitor 1C (p57, Kip2) (CDKN1C), and CHK1 checkpoint homolog (CHEK1, formally known as CHK1) were increased, while expressions of cyclin-dependent kinase 2 (CDK2), cell division cycle 25A (CDC25A), and cyclin E1 (CCNE1) were decreased. The pattern of these gene expressions were confirmed through RT-PCR. Our results showed that D-amygdalin might control cell cycle regulator genes and arrest S phase of cell cycle in K562 cells as the useful anticancer drug.

• Journal of Life Science
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• v.16 no.4
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• pp.589-597
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• 2006

Genistein, a natural isoflavonoid phytoestrogen, is a strong inhibitor of protein tyrosine kinase and DNA topoisomerase activities. There are several studies documenting molecular alterations leading to cell cycle arrest and induction of apoptosis by genistein as a chemopreventive agent in a variety of cancer cell lines; however, its mechanism of action and its molecular targets on human bladder carcinoma and leukemic cells remain unclear. In the present study, we have addressed the mechanism of action by which genistein suppressed the proliferation of T24 bladder carcinoma and U937 leukemic cells. Genistein significantly inhibited the cell growth and induced morphological changes, and induced the G2/M arrest of the cell cycle in both T24 and U937 cells with a relatively stronger cytotoxicity in U937. The G2/M arrest in T24 cells was associated with the inhibition of cyclin A, cyclin B1 and Cdc25C protein expression without alteration of tumor suppressor p53 and cyclin-dependent kinase (Cdk) inhibitor p21(WAF1/CIP1). However, the inhibitory effects of genistein on the cell growth of U937 cells were connected with a marked inhibition of cyclin B1 and an induction of Cdk inhibitor p21 proteins by p53-independent manner. These data suggest that genistein may exert a strong anticancer effect and additional studies will be needed to evaluate the different mechanisms between T24 and U937 cells.