• YAKHAK HOEJI
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• v.43 no.3
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• pp.378-384
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• 1999

Retinoic acid (RA) and dibutyryl cyclic AMP (dbcAMP) induce the differentiation of the multipotent embryonic carcinoma cell line, F9 cells, into parietal endoderm like cell. The F9 cells are highly proliferative doubling approximately 12 hourse. S Phase is predominant, lasting 10 hours and G2/M phase occupies most of the remaining cycle (2 hours) and G1 phase is nearly non-existent. In this study, we showed the effect of RA and dbcAMPon the cell cycle associated molecules (especially around G1 phase) during F9 cell differentiation. Differentiation of F9 cells was induced by the combined addition of RA ($10^{-7}M$) and dbcAMP (0.5mM), and cells were harvested daily up to 4 days. Flow cytometric analysis showed the prolongation of G1 phase around 30 hours after induction. Western blot analysis revealed that the amount of cyclin D1 and cdk2 were increased at day 4. However, histone H1 kinase activity of cdk2 was decreased. These data strongly suggest that RA and dbcAMP induce the growth arrest of F9 cells at G1 phase by decreasing the activity of cdk2, although they have increased the protein contents of cyclin D1 and cdk2. The reason for the discrepancy between the H1 kinase activity and protein contents are not clear yet.

• Genomics & Informatics
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• v.12 no.4
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• pp.195-202
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• 2014

Metabolic syndrome (MetS) is a complex disorder related to insulin resistance, obesity, and inflammation. Genetic and environmental factors also contribute to the development of MetS, and through genome-wide association studies (GWASs), important susceptibility loci have been identified. However, GWASs focus more on individual single-nucleotide polymorphisms (SNPs), explaining only a small portion of genetic heritability. To overcome this limitation, pathway analyses are being applied to GWAS datasets. The aim of this study is to elucidate the biological pathways involved in the pathogenesis of MetS through pathway analysis. Cohort data from the Korea Associated Resource (KARE) was used for analysis, which include 8,842 individuals (age, $52.2{\pm}8.9years$ ; body mass index, $24.6{\pm}3.2kg/m^2$). A total of 312,121 autosomal SNPs were obtained after quality control. Pathway analysis was conducted using Meta-analysis Gene-Set Enrichment of Variant Associations (MAGENTA) to discover the biological pathways associated with MetS. In the discovery phase, SNPs from chromosome 12, including rs11066280, rs2074356, and rs12229654, were associated with MetS (p < $5{\times}10^{-6}$), and rs11066280 satisfied the Bonferroni-corrected cutoff (unadjusted p < $1.38{\times}10^{-7}$, Bonferroni-adjusted p < 0.05). Through pathway analysis, biological pathways, including electron carrier activity, signaling by platelet-derived growth factor (PDGF), the mitogen-activated protein kinase kinase kinase cascade, PDGF binding, peroxisome proliferator-activated receptor (PPAR) signaling, and DNA repair, were associated with MetS. Through pathway analysis of MetS, pathways related with PDGF, mitogen-activated protein kinase, and PPAR signaling, as well as nucleic acid binding, protein secretion, and DNA repair, were identified. Further studies will be needed to clarify the genetic pathogenesis leading to MetS.

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.110-113
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• 2005

Under the condition of nutritional deprivation, actively growing cells prepare to enter $G_0$-like stationary phase. Protein modification by phosphorylation/dephosphorylation or ubiqutination contributes to transfer cells from active cell cycle to dormant stage. We show here that Psp1/Sds23, which functions in association with the 20S cyclosome/APC (1) and is essential for cell cycle progression in Schizosaccharomyces pombe (2), is phosphorylated by stress-activated MAP kinase Sty1 and protein kinase A, as well as Cdc2/cyclinB, upon entry into stationary phase. Three serines at the positions 18,333 and 391 are phosphorylated and overexpression of Psp1 mutated on these sites causes cell death in stationary phase. These modifications are required for the binding of Spufd2, a S.pombe homolog of multiubiquitin chain assembly factor E4 in ubiquitin fusion degradation pathway. Deletion of Spufd2 gene led to increase cell viability in stationary phase, indicating that S. pombe Ufd2 functions to inhibit cell growth at this stage to maintain cell viability. Moreover, Psp1 enhances the multiubiquitination function of Ufd2, suggesting that Psp1 phosphorylated by sty1 and PKA kinases is associated with the Ufd2-dependent protein degradation pathway, which is linked to stress tolerance, to maintain cell viability in the $G_0$-like stationary phase.

• The Korean Journal of Food And Nutrition
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• v.24 no.2
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• pp.258-267
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• 2011

14-3-3 is a highly conserved, ubiquitously expressed protein family. It associates with diverse cellular proteins through its specific phosphoserine/phosphothreonine-binding activity and thus contributes to the regulation of crucial cellular processes such as metabolism, signal transduction, cell-cycle control, apoptosis, protein trafficking, transcription and stress responses. This study aims to determine changes in levels of 14-3-3 isoforms and 14-3-3 - associated proteins in Helicobacter pylori(H. pylori)-infected gastric epithelial AGS cells. AGS cells were stimulated with H. pylori(NCTC 11637) at the ratio of 300:1(bacterium:cell). Western blot analysis revealed that 14-3-3 $\sigma$ was elevated at 3 hr after H. pylori treatment. Other isoforms were not significantly affected by H. pylori infection. Using immunoprecipitation to 14-3-3 $\sigma$, followed by proteomic analysis, we found that S phase kinase associated protein isoform 2 bound to 14-3-3 $\sigma$ has increased. In contrast, three proteins (DEAD-box polypeptide 3, heterogeneous nuclear ribonucleoprotein H2 and WD repeat-containing protein isoform 1) bound to 14-3-3 decreased by H. pylori infection. Our results suggest that 14-3-3 may play an important regulatory role in H. pylori-induced signal transduction in gastric epithelial cells.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.2
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• pp.677-682
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• 2014

Resveratrol has been examined in several model systems for potential effects against cancer. Adenosine monophosphate-activated protein kinase (AMPK) is reported to suppress proliferation in most eukaryocyte cells. Whether resveratrol via AMPK inhibits proliferation of oesophageal adenocarcinoma cells (OAC) is unknown. The aim of this study was to determine the roles of AMPK in the protective effects of resveratrol in OAC proliferation and to elucidate the underlying mechanisms. Treatment of cultured OAC derived from human subjects or cell lines with resveratrol resulted in decreased cell proliferation. Further, inhibition of AMPK by pharmacological reagent or genetical approach abolished resveratrol-suppressed OAC proliferation, reduced the level of $p27^{Kip1}$, a cyclin-dependent kinase inhibitor, and increased the levels of S-phase kinase-associated protein 2 (Skp2) of $p27^{Kip1}$-E3 ubiquitin ligase and 26S proteasome activity reduced by resveratrol. Furthermore, gene silencing of $p27^{Kip1}$ reversed resveratrol-suppressed OAC proliferation. In conclusion, these findings indicate that resveratrol inhibits Skp2-mediated ubiquitylation and 26S proteasome-dependent degradation of $p27^{Kip1}$ via AMPK activation to suppress OAC proliferation.

• Journal of Cancer Prevention
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• v.23 no.4
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• pp.170-175
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• 2018

Background: Human hepatocellular carcinoma (HCC) is a common liver tumor and the main cause of cancer-related death. Tyrosine kinase inhibitors, such as imatinib and GNF5 which were developed to treat chronic myelogenous leukemia, regulate the progression of various cancers. The aim of this study was to confirm the anti-tumor activity of tyrosine kinase inhibitors through regulation of S-phase kinase-associated protein 2 (Skp2), an important oncogenic factor in various cancer cells, in human hepatocarcinoma SK-HEP1 cells. Methods: Cell viability and colony formation assays were conducted to evaluate the effects of imatinib, GNF5 and GNF2 on the growth of SK-HEP1 cells. Using immunoblot analysis, we assessed change of the activation of caspases, PARP, Akt, mitogen-activated protein kinases, and Skp2/p27/p21 pathway by imatinib and GNF5 in SK-HEP1 cells. Using sh-Skp2 HCC cells, the role of Skp2 in the effects of imatinib and GNF5 was evaluated. Results: Imatinib and GNF5 significantly inhibited the growth of SK-HEP1 cells. Treatment of imatinib and GNF5 decreased Skp2 expression and Akt phosphorylation, and increased the expression of p27, p21, and active-caspases in SK-HEP1 cells. In sh-Skp2 HCC cells, cell growth and the expression of Skp2 were inhibited by more than in the mock group treated with imatinib and GNF5. Conclusions: These results suggest that the anti-growth activity of tyrosine kinase inhibitors may be associated with the regulation of p27/p21 and caspases through Skp2 blockage in HCC cells.

• Journal of Physiology & Pathology in Korean Medicine
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• v.20 no.3
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• pp.701-709
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• 2006

The Rhus verniciflua Stokes (乾漆-RVS) has been used in traditional East Asia medicine for the therapy of gastritis, stomach cancer, although the mechanism for the biological activity is unclear. In the present study aims to investigate RVS extract contributes to growth inhibitory effect and it's the molecular mechanism on the human gastric cancer cells. AGS (gastric cancer cells) and RIEI (normal cells) were treated to different concentrations and periods of RVS extract $(10{\;}{\sim{{\;}100{\;}ug/mil)$. Growth inhibitory effect was analyzed by measuring FACS study and MTS assay. Cell cycle inhibition was confirmed by measuring CDK2 kinase activity by immunoprecipitation and kinase assay. And apoptosis was confirmed by surveying caspase cascades activation using a pan caspase inhibitor Exposure to RVS extract (50 ug/mll) resulted in a synergistic inhibitory effect on cell growth in AGS cells. Growth inhibition was related with the inhibition of proliferation and induction of apoptosis. The extract induces Gl -cell cycle arrest through the regulation of cyclins, the induction of p27kip1, and the decrease CDK2 kinase activity. And upregulated p27kip1 level is caused by protein stability increment by the reduction of S-phase kinase-associated protein 2 (Skp2), a key molecule related with p27kip1 ubiquitination and degradation, and do novo protein synthesis. Besides, 乾漆 extract induces apoptosis through the expression of Bax, poly(ADP-ribose) polymerase (PARP) and activation of caspase-3. RVS extract induces Gl -cell cycle arrest via accumulation of p27kip1 and apoptosis in human gastric cancer cells but not in normal cells, therefore we suggest that the extract can be used as a novel class of anti-cancer drugs.

• Molecules and Cells
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• v.46 no.6
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• pp.360-373
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• 2023

Papillary thyroid carcinoma (PTC) is the most common subtype of thyroid carcinoma. Despite a good prognosis, approximately a quarter of PTC patients are likely to relapse. Previous reports suggest an association between S-phase kinase-associated protein 2 (SKP2) and the prognosis of thyroid cancer. SKP1 is related to apoptosis of PTC cells; however, its role in PTC remains largely elusive. This study aimed to understand the expression and molecular mechanism of SKP2 in PTC. SKP2 expression was upregulated in PTC tissues and closely associated with clinical diagnosis. In vitro and in vivo knockdown of SKP2 expression in PTC cells suppressed cell growth and proliferation and induced apoptosis. SKP2 depletion promoted cell autophagy under glucose deprivation. SKP2 interacted with PH domain leucine-rich repeat protein phosphatase-1 (PHLPP1), triggering its degradation by ubiquitination. Furthermore, SKP2 activates the AKT-related pathways via PHLPP1, which leads to the cytoplasmic translocation of SKP2, indicating a reciprocal regulation between SKP2 and AKT. In conclusion, the upregulation of SKP2 leads to PTC proliferation and survival, and the regulatory network among SKP2, PHLPP1, and AKT provides novel insight into the molecular basis of SKP2 in tumor progression.

• The Korean Journal of Physiology and Pharmacology
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• v.23 no.3
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• pp.171-179
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• 2019

Pituitary tumors are usually benign but can occasionally exhibit hormonal and proliferative behaviors. Dysregulation of the G1/S restriction point largely contributes to the over-proliferation of pituitary tumor cells. F-box protein S-phase kinase-interacting protein-2 (SKP2) reportedly targets and inhibits the expression of $p27^{Kip1}$, a well-known negative regulator of G1 cell cycle progression. In this study, SKP2 expression was found to be upregulated while $p27^{Kip1}$ expression was determined to be downregulated in rat and human pituitary tumor cells. Furthermore, SKP2 knockdown induced upregulation of $p27^{Kip1}$ and cell growth inhibition in rat and human pituitary tumor cells, while SKP2overexpression elicited opposite effects on $p27^{Kip1}$ expression and cell growth. The expression of microRNA-186 (miR-186) was reported to be reduced in pituitary tumors. Online tools predicted SKP2 to be a direct downstream target of miR-186, which was further confirmed by luciferase reporter gene assays. Moreover, miR-186 could modulate the cell proliferation and $p27^{Kip1}$-mediated cell cycle alternation of rat and human pituitary tumor cells through SKP2. As further confirmation of these findings, miR-186 and $p27^{Kip1}$ expression were downregulated, while SKP2 expression was upregulated in human pituitary tumor tissue samples; thus, SKP2 expression negatively correlated with miR-186 and $p27^{Kip1}$ expression. In contrast, miR-186 expression positively associated with $p27^{Kip1}$ expression. Taken together, we discovered a novel mechanism by which miR-186/SKP2 axis modulates pituitary tumor cell proliferation through $p27^{Kip1}$-mediated cell cycle alternation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1766-1772
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• 2009

In this study, we are interested in comparing the protein profiles of acid-shocked and control cells of S. mutans isolated from Korean children with caries. The results of 2D gel electrophoresis showed that twelve proteins are up-regulated when the cells were grown under 20 mM lactic acid stress in the exponential phase. Up-proteins under acid stress were estimated a major key of the survival and proliferation of S. mutans in low pH environments. These proteins are estimated generally associated with three biochemical pathways: glycolysis, alternative acid production and branched-chain amino acid biosynthesis.