• BMB Reports
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• 제44권8호
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• pp.553-557
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• 2011

We previously reported that CDK2/Cyclin A can phosphorylate and activate the transcription factor NF-Y. In this study, we investigated a potential regulatory role for NF-Y in the transcription of Cyclin A and other cell cycle regulatory genes. Gel-shift assays demonstrate that NF-Y binds to CCAAT sequences in the Cyclin A promoter, as well as to those in the promoters of cell cycle G2 regulators such as CDC2, Cyclin B and CDC25C. Furthermore, expression of Cyclin A increases NF-Y's affinity for CCAAT sequences in the CDC2 promoter; however, Cyclin A's induction of CDC2 transcription is antagonized by p21, an inhibitor of CDK2/Cyclin A. These results suggest a model wherein NF-Y binds to and activates transcription from the Cyclin A promoter, increasing cellular levels of Cyclin A/CDK2 and potentiating NF-Y's capacity for transcriptional transactivation, and imply a positive feedback loop between NF-Y and Cyclin A/CDK2. Our findings are additionally indicative of a role for Cyclin A in activating Cyclin B/CDK1 through promoting NF-Y dependent transcription of Cyclin B and CDC2; NF-Y mediated crosstalk may therefore help to orchestrate cell-cycle progression.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제15권1호
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• pp.29-37
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• 2012

Purpose: To examine the prevalence of $Clostridium$ $difficile$ ($C.$ $difficile$) colonization (CDC) and potential neonatal determinants of CDC in hospitalized preterm infants. Methods: Fecal samples were serially collected within 72 h after birth and at 1, 2, and 4-6 weeks of age from preterm infants in the neonatal intensive care units (NICUs) of two different university hospitals. Total bacterial DNA was extracted from each fecal sample from 49 infants, and polymerase chain reaction (PCR) was performed with primers for the 16S gene of $C.$ $difficile$ and the toxin A and toxin B genes. The correlation between the results of $C.$ $difficile$ PCR assays and the clinical characteristics of the infants was analyzed. Results: The prevalence rates of CDC were 34.7, 37.2, 41.3, and 53.1% within 72 h after birth and at 1, 2, and 4.6 weeks of age, respectively. The toxin positivity rate was significantly higher in the infants with persistent CDC than in those with transient CDC (8/12 [66.7%] vs. 6/25 [24.5%] ($p$=0.001). Among the various neonatal factors, only the feeding method during the first week after birth was significantly associated with persistent CDC. Exclusive breast-milk feeding (EBMF) significantly decreased the risk of persistent CDC compared to formula or mixed feeding (adjusted odds ratio: 0.133, 95% confidence interval: 0.02-0.898, $p$=0.038). Conclusion: The prevalence of CDC increased with the duration of hospitalization in preterm infants in the NICU. EBMF during the first week after birth in hospitalized preterm infants may protect against persistent CDC.

• 생명과학회지
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• 제23권6호
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• pp.832-837
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• 2013

본 연구에서는 생체 내 구성요소 및 에너지원으로서 중요한 역할을 하는 글루타민 결핍에 의한 인체 전립선 PC3 암세포의 증식에 관한 기전 연구를 실시하였다. 글루타민 결핍에 의한 PC3 세포의 증식억제는 세포주기 G2/M arrest와 연관성이 있었으나, apoptosis 유발 현상은 관찰되지 않았다. 글루타민 결핍에 의한 G2/M arrest는 전사 및 번역 수준에서 Cdc2, cyclin A 및 cyclin B1의 발현 억제 및 p53 비의존적인 p21(WAF1/CIP1)의 발현 증가와 연관성이 있었다. 아울러 글루타민 결핍은 Chk1 및 Chk2의 인산화를 증가시켰으나, Cdc25C의 인산화는 감소시켰다. 본 연구의 결과는 글루타민 결핍에 의한 PC3 세포의 증식억제가 apoptosis 유발과는 상관없이 G2/M arrest를 유발시킨다는 첫 번째 증거이다.

• BMB Reports
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• 제51권7호
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• pp.350-355
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• 2018

HnRNPK is a multifunctional protein that participates in chromatin remodeling, transcription, RNA splicing, mRNA stability and translation. Here, we uncovered the function of hnRNPK in regulating the proliferation and differentiation of myoblasts. hnRNPK was mutated in the C2C12 myoblast cell line using the CRISPR/Cas9 system. A decreased proliferation rate was observed in hnRNPK-mutated cells, suggesting an impaired proliferation phenotype. Furthermore, increased G2/M phase, decreased S phase and increased sub-G1 phase cells were detected in the hnRNPK-mutated cell lines. The expression analysis of key cell cycle regulators indicated mRNA of Cyclin A2 was significantly increased in the mutant myoblasts compared to the control cells, while Cyclin B1, Cdc25b and Cdc25c were decreased sharply. In addition to the myoblast proliferation defect, the mutant cells exhibited defect in myotube formation. The myotube formation marker, myosin heavy chain (MHC), was decreased sharply in hnRNPK-mutated cells compared to control myoblasts during differentiation. The deficiency in hnRNPK also resulted in the repression of Myog expression, a key myogenic regulator during differentiation. Together, our data demonstrate that hnRNPK is required for myoblast proliferation and differentiation and may be an essential regulator of myoblast function.

• 한국환경성돌연변이발암원학회지
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• 제25권2호
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• pp.51-59
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• 2005

Overexpression of HSP25 delayed cell growth, increased the level of $p21^{waf}$, reduced the levels of cyclin D1, cylcin A and cdc2, and induced radioresistance in L929 cells. We demonstrated that extracellular regulated kinase (ERK) and MAP kinase/ERK kinase (MEK) expressions as well as their activation (phospho-forms) were inhibited by hsp25 overexpression. To confirm the relationship between ERK1/2 and hsp25-mediated radioresistance, ERK1 or ERK2 cDNA was transiently transfected into the hsp25 overexpressed cells and their radioresistance was examined. HSP25-mediated radioresistance was abolished by overexpression of ERK2, but not by overexpression of ERK1. Alteration of cell cycle distribution and cell cycle related protein expressions (cyclin D, cyclin A and cdc2) by hsp25 overexpression were also recovered by ERK2 cDNA transfection. Increase in Bc1-2 protein by hsp25 gene transfection was also reduced by subsequent ERK2 cDNA-transfection. In addition, HSP25 overexpression reduced reactive oxygen species (ROS) and increased expression of manganese superoxide dismutase (MnSOD) gene. Increased activation of NF-kB (IkB degradation) was also found in hsp25-overexpressed cells. Moreover, transfection of hsp25 antisense gene abrogated all the HSP25-mediated phenomena. To further elucidate the exact relationship between MnSOD induction and NF-kB activation, dominant negative $I-kB\alpha(I-kB\alpha-DN)$ construction was transfected to HSP25 overexpressed cells. $I-kB\alpha-DN$ inhibited HSP25 mediated MnSOD gene expression. In addition, HSP25 mediated radioresistance was blocked by $I-kB\alpha-DN$ transfection. Blockage of MnSOD with antisense oligonucleotides in HSP25 overexpressed cells, prevented apoptosis and returned the ERK1/2 activation to the control level. From the above results, we suggest for the first time that reduced oxidative damage by HSP25 was due to MnSOD-mediated down regulation of ERK1/2.

• 한국미생물·생명공학회지
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• 제41권4호
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• pp.425-432
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• 2013

본 연구에서는 인체 대장암세포인 HT29를 사용하여 포황 메탄올 추출물(Methanol extract of Typha orientalis, METO)의 항암 활성 및 그 분자적 기전에 관하여 분석하였다. 먼저 METO가 다양한 암세포의 증식에 미치는 영향을 분석한 결과, 인체 대장암 세포, 폐암 세포, 간암 세포 등의 세포증식을 억제하였으며 그 중에서도 대장암 세포인 HT29에 대해 강한 세포 증식 억제 효과를 나타내었다. METO에 의한 세포 증식 억제 기전을 분석하기 위하여 Flow cytometry analysis를 수행한 결과, METO 농도의존적으로 HT29 세포의 G2/M기 세포분포가 증가하고 아울러 apoptosis 유발군인 SubG1기 세포분포가 증가하는 것을 확인할 수 있었다. METO에 의한 HT29 세포의 G2/M arrest는 Cdc2의 inactive form인 phospho-Cdc2의 증가에 의한 G2/M checkpoint 관련 단백질의 활성억제에 의한 것이라 사료된다. 이러한 phospho-Cdc2의 증가는 METO에 의해 발현이 증가된 Wee1 kinase와 발현이 감소된 Cdc25C phosphatase에 의해 야기된 것임을 확인하였다. 또한 METO에 의한 HT29의 apoptosis 유도에 관한 분자적 기전 분석을 위해 Western blot analysis를 수행한 결과, METO 농도가 증가할수록 종양 억제 유전자인 p53, death receptor인 FAS, Bcl-2 family 중 pro-apoptotic 단백질인 Bax 및 cytosolic cytochrome C의 발현이 증가되고, Caspase-3가 활성화되어 단편화된 Caspase-3의 증가가 관찰되었다. 또한 활성화된 Caspase-3의 기질 단백질인 PARP의 단편화가 일어나 apoptosis가 유도되는 것을 알 수 있었다. 이상의 결과들로부터 METO는 인체 대장암세포 HT29의 G2/M arrest 및 apoptosis 유도에 의한 항암활성을 보유함을 확인하였다.

• 한국식품영양과학회지
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• 제33권8호
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• pp.1237-1245
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• 2004

브라질 기원인 신령 버섯 (A. blazei murill)은 강력한 항암 및 면역강화 작용을 가진 것으로 알려져 있다. 본 연구에서는 신령버섯 수용성 추출물(water extracted A. blazei Murill, WEAB)이 A549 인체 폐암세포 증식에 미치는 영향을 조사하였으며, 증식억제와 연관된 기전 해석을 시도하였다. WEAB가 처리된 A549 세포는 처리 농도 의존적으로 생존율이 감소되었으며, WEAB 처리는 암세포의 다양한 형태적 변형을 유발하였다. Flow cytometry 분석 결과로서 WEAB 처리에 의한 A549 폐암세포의 증식억제는 세포주기 G2/M arrest 및 apoptosis 유발과 직접적으로 연관성이 있음을 알 수 있었다. WEAB가 처리된 암세포에서 전사 및 번역 수준에서 cyclin A 발현의 감소 및 Cdk inhibitor p21 발현의 증가 현상이 관찰되었으나, cyclin B1, Cdk2, Cdc2, Wee1, Cdc25c 및 p53 등의 발현에는 큰 변화가 관찰되지 못하였다. 또한 WEAB의 처리는 COX-2 선택적 발현 저하를 유발하였으나, telomere 조절 관련 유전자들의 발현에는 큰 영향을 주지 못하였다. 이상의 결과는 신령버섯 추출물이 강력한 항암 및 암 예방 효능의 잠재력을 가지고 있음을 의미하며, 이에 관한 지속적인 연구가 필요할 것으로 생각된다.

• Radiation Oncology Journal
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• 제21권4호
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• pp.306-314
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• 2003

목적: K562 세포의 방사선에 의한 세포 사망은 mitotic catastrophe 현상이 위주로 나타나지만 herbimycin A (HMA)에 의하여 apoptosis 반응이 촉진되는 반면 genisteln에 의하여 두 가지 형태의 세포사망이 모두 억제된다. 본 연구에서는 HMA와 genistein에 의한 K562세포의 방사선 유도 세포주기 조절 변화와 세포 사망 양상의 연관성을 조사하였다. 대상 및 방법: 지수증식기의 KS62 세포에 6 MV 선형가속기(Clinac 1,m C, Varian)를 이용하여 200~300 cGy/min의 선량률로 10 Gy를 균일하게 조사하였다. HMA와 genistein은 각각 250 nM와 25$\mu$M농도로 방사선 조사 후 즉시 투여하였다. 실험에서는 세포주기, 오절인자의 발현 및 활성, 노화 및 분화정도 등에 있어서의 시간에 따른 변화를 조사하였다. 결과: 방사선 단독조사에서 KS62세포는 G2기의 정체를 보였으나 정상적인 053을 가지는 세포와는 달리 지속적인 세포주기의 정체를 보이지 않았다. G2정체가 유지되는 동안 cyclin Bl의 점진적인 증가를 관찰할 수 있었으며, 이는 염색체의 복제가 완료되지 않은 상태에서 M기로 진행하여 미성숙한 염색체 응축과 mitotic catastrophe 현상이 나타나는 것과 일치한다. 방사선 조사와 함께 HMA를 투여한 경우에는 G2정체가 빠르게 해소되었으며 동시에 Gl기에서 세포가 정체되는 양상을 보였다. 세포주기 조절인자 cdc2 kinase 활성 증가와 cyclln I와 A 발현 및 CDK2 활성의 감소 등의 현상으로 설명되며, 이는 apoptosis의 증가와 연관성을 갖는다. 반면 genistein의 경우에는 cyclin Bl과 떨cfsc 발현 및 cdc2활성이 모두 감소하는 등 G2정체를 계속 유지하였다. 이와 함께 방사선에 의한 노화와 megakaryocyte로의 분화도 지속되는 것을 관찰할 수 있었다. 결론: HMA와 genistein에 의한 KS62세포의 방사선 유도 세포사망의 변화는 세포주기 조절과 밀접하게 연관되어 있음을 확인하였다. 이는 다양한 방사선 유도 세포사망의 기전을 이해하는 데 독창적인 모델을 제공하며, 방사선을 이용한 암 치료법의 개발에 새로운 표적을 제공할 수 있을 것이다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권11호
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• pp.6419-6425
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• 2013

Background: Neoadjuvant chemotherapy (NACT) is a treatment modality whereby chemotherapy is used as the initial treatment of HNSCC in patients presenting with advanced cancer that cannot be treated by other means. It leads to shrinkage of tumours to an operable size without significant compromise to essential oro-facial organs of the patients. The molecular mechanisms behind shrinkage due to NACT is not well elucidated. Materials and Methods: Eleven pairs of primary HNSCCs and adjacent normal epithelium, before and after chemotherapy were screened for cell proliferation and apoptosis. This was followed by immunohistochemical analysis of some cell cycle (LIMD1, RBSP3, CDC25A, CCND1, cMYC, RB, pRB), DNA repair (MLH1, p53) and apoptosis (BAX, BCL2) associated proteins in the same set of samples. Results: Significant decrease in proliferation index and increase in apoptotic index was observed in post-therapy tumors compared to pre-therapy. Increase in the RB/pRB ratio, along with higher expression of RBSP3 and LIMD1 and lower expression of cMYC were observed in post-therapy tumours, while CCND1 and CDC25A remained unchanged. While MLH1 remained unchanged, p53 showed higher expression in post-therapy tumors, indicating inhibition of cell proliferation and induction of apoptosis. Increase in the BAX/BCL2 ratio was observed in post-therapy tumours, indicating up-regulation of apoptosis in response to therapy. Conclusions: Thus, modulation of the G1/S cell cycle regulatory proteins and apoptosis associated proteins might play an important role in tumour shrinkage due to NACT.

• Tribology and Lubricants
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• 제25권1호
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• pp.20-24
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• 2009

TiC-derived carbon coatings have been synthesized at $600^{\circ}C$ temperature treatment with $H_2/Cl_2$ mixture gases. From Raman spectroscopy measurements, the modified layer was covered with carbon and the thick-ness of the layer was increased with increasing reaction time. And $I_D/I_G$ ratio was decreased with increasing reaction time. The superior tribological property was obtained from TiC reacted with $Cl_2$ gas for 2 hrs. And the tribological property measurements indicate that TiC-derived carbon layer has $0.9{\times}10_{-6}mm^3/Nm$ in wear coefficient and 0.13 in friction coefficient.