• BMB Reports
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• 제44권5호
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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.

• Reproductive and Developmental Biology
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• 제35권4호
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• pp.511-518
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• 2011

To avoid hyperacute rejection of xenografts, ${\alpha}1,3$-galactosyltransferase knock-out (GalT KO) pigs have been produced. In this study, we examined whether Sia-containing glycoconjugates are important as an immunogenic non-Gal epitope in the pig liver with disruption of ${\alpha}1,3$-galactosyltransferase gene. The target cells were then used as donor cells for somatic cell nuclear transfer (scNT). A total of 1,800 scNT embryos were transferred to 10 recipients. One recipient developed to term and naturally delivered two piglets. Real-time RT-PCR and glycosyltransferase activity showed that ${\alpha}2,3$-sialyltransferase (${\alpha}2,3ST$) and ${\alpha}2,6$-sialyltransferase (${\alpha}2,6ST$) in the heterozygote GalT KO liver have higher expression levels and activities compared to controls, respectively. According to lectin blotting, sialic acidcontaining glycoconjugate epitopes were also increased due to the decreasing of ${\alpha}$-Gal in heterozygote GalT KO liver, whereas GalNAc-containing glycoconjugate epitopes were decreased in heterozygote GalT KO liver compare to the control. Furthermore, the heterozygote GalT KO liver showed a higher Neu5Gc content than control. Taken together, these finding suggested that the deficiency of GalT gene in pigs resulted in increased production of Neu5Gc-bounded epitopes (H-D antigen) due to increase of ${\alpha}2,6$-sialyltransferase. Thus, this finding suggested that the deletion of CMAH gene to the GalT KO background is expected to further prolong xenograft survival.

• 대한바이러스학회지
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• 제29권4호
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• pp.235-245
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• 1999

HIV-1 Tat, a strong transactivator, is essential for the HIV-1 replication and AIDS progression. The Tat function is markedly inhibited by human p53 anti-oncogene. However, the detail mechanism has not yet been clearly revealed. In our previous report, we have addressed that p53 is unlikely to interact directly with HIV-1 Tat. In the consecutive experiments, Tat-phosphorylation was found to increase in proportional to the amounts of transfected p53. This work was initiated to identify the signaling factor that is involved in the p53-mediated Tat suppression. Several protein kinases were tested for the phosphorylation of Tat, and we found that PKR is likely to be involved in the p53-mediated Tat suppression. PKR was co-immunoprecipitated by anti-Tat antibody in the Tat-expressing Jurkat cell lysates only when the cells were transfected by p53, indicating that PKR-Tat interaction depends on the p53 activity. The interaction seems to result in PKR-mediated Tat-phosphorylation. Tat function was not blocked by p53 when co-transfected trasiently with antisense-PKR. We have generated PKR-knock out Jurkat cell clone. The PKR defective Jurkat cells didn't show the p53-mediated Tat suppression. These data indicate that p53-mediated Tat suppression is strongly associated with PKR. PKR-mediated Tat phosphorylation experiments are now under investigation by kinase assay and co-immunoprecipitation in the presence or absence of p53.

• 대한기계학회논문집B
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• 제34권5호
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• pp.449-456
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• 2010

HCCI 엔진은 고효율, 저공해를 실현할 수 있는 차세대 내연기관이다. 그러나 HCCI 엔진이 상용화되기 위해서는 몇 가지 문제점들이 해결되어야 한다. 그 중에서 가장 큰 문제점은 과도한 압력 상승률이 노킹을 발생시키기 때문에 운전영역이 제한되는 것이다. 이번 연구의 목적은 HCCI 엔진에서 압력상승률 저감을 위하여 온도 성층화와 농도 성층화 효과를 조사하는 것이다. 그리고 Multi-zone 모델을 이용한 화학반응 수치해석을 통하여 연소 및 배기가스 특성에 미치는 영향을 알아보았다. 수치해석에서 2 단계 열발생을 가지는 DME와 1단계 열발생을 가지는 메탄을 사용하였다.

• Animal cells and systems
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• 제12권2호
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• pp.69-75
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• 2008

The tumor suppressor and transcription factor p53 is a key modulator of cellular stress responses, and can trigger apoptosis in many cell types including neurons. In this study, we have shown that Microtubule-associated protein 1B(MAP1B) light chain interacts with tumor suppressor p53. MAP1B is one of the major cytoskeletal proteins in the developing nervous system and essential in forming axons during elongation. We also demonstrate that both p53 and MAP1B-LC1 interact in the nucleus in HEK 293 cells. Indeed, we show that the MAP1B-LC1 negatively regulates p53-dependent transcriptional activity of a reporter containing the p21 promoter. Consequently, MAP1B light chain binds with p53 and their interaction leads to the inhibition of doxorubicin-induced apoptosis in HEK 293 cells. Furthermore, these examinations might be taken into consideration when knock-down of MAP1B-LC1 is used as a cancer therapeutic strategy to enhance p53's apoptotic activity in chemotherapy.

• 연구논문집
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• 통권33호
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• pp.5-16
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• 2003

Fuel distribution, combustion, and flame propagation characteristics of heavy duty engine with the liquid phase LPG injection(LPLI) were studied in a single cylinder engine. Optically accessible single cylinder engine and laser diagnostics system were built for quantifying fuel concentration by acetone PLIF(planar laser induced fluorescence) measurements. In case of Otto cycle engine with large bore size, the engine knock and thermal stress of exhaust manifold are so critical that lean burn operation is needed to reduce the problems. It is generally known that fuel stratification is one of the key technologies to extend the lean misfire limit. The formation of rich mixture in the spark plug vicinity was achieved by open valve injection. With higher swirl strength(Rs=3.4) and open valve injection, the cloud of fuel followed the flow direction and the radial air/fuel mixing was limited by strong swirl flow. It was expected that axial stratification was maintained with open-valve injection if the radial component of the swirling motion was stronger than the axial components. The axial fuel stratification and concentration were sensitive to fuel injection timing in case of Rs=3.4 while those were relatively independent of the injection timing in case of Rs2.3. Thus, strong swirl flow could promote desirable axial fuel stratification and, in result, may make flame propagation stable in the early stage of combustion.

• IMMUNE NETWORK
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• 제13권6호
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• pp.264-274
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• 2013

The unrestricted population of $CD4^+Foxp3^+$ regulatory T (Treg) cells, which have been known to control the expression of autoimmune diseases and protective immunity to inflammatory reactions, has led to greater appreciation of functional plasticity. Detecting and/or isolating Ag-specific $CD4^+Foxp3^+$ Tregs at the single cell level are required to study their function and plasticity. In this study, we established and compared both MHC class II tetramer and intracellular CD154 staining, in order to detect $CD4^+Foxp3^+$ Treg specific for foreign Ag in acute and chronic infections with lymphocytic choriomeningitis virus (LCMV). Our results revealed that MHC class II tetramer staining showed a lower detection rate of LCMV $GP_{66-77}$-specific $CD4^+$ T cells because most of MHC class II tetramers were unbound and unstable when combined staining was performed with intracellular cytokines. In contrast, intracellular CD154 staining was revealed to be easier and simple for detecting LCMV $GP_{66-77}$-specific $CD4^+$ T cells, compared to MHC class II tetramer staining. Subsequently, we employed intracellular CD154 staining to detect LCMV $GP_{66-77}$-specific $CD4^+Foxp3^+$ Tregs using $Foxp3^{GFP}$ knock-in mouse, and found that LCMV $GP_{66-77}$-specific $CD4^+Foxp3^+$ Tregs and polyclonal $CD4^+Foxp3^+$ Tregs showed differential expansion in mice infected with LCMV Arms or Cl13 at acute (8 and 13 days pi) and chronic phases (35 days pi). Therefore, our results provide insight into the valuable use of intracellular CD154 staining to detect and characterize foreign Ag-specific $CD4^+Foxp3^+$ Treg in various models.

• KSBB Journal
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• 제32권3호
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• pp.224-232
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• 2017

Resveratrol has been actively investigated as an anticancer drug since it induces cell growth inhibition and apoptosis in many cancer cells. Resveratrol acts through modulation of multiple pathways and genes. In this study, we found resveratrol reduced cell growth and mammosphere formation in MDA-MB-231 triple-negative human breast cancer cells. This suppressive effect of resveratrol is accompanied by a reduction in Bmi-1 gene expression. We also observed that knock-down of Bmi-1 gene by small interfering RNA effectively sensitizes breast cancer cells to resveratrol treatment. Our data demonstrate, for the first time, that resveratrol down-regulates Bmi-1 expression in human breast cancer cells and suggest that specific molecular targeting of Bmi-1 can be combined with a chemotherapeutic strategy to improve the response of breast cancer cells to resveratrol.

• 미생물학회지
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• 제46권4호
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• pp.401-404
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• 2010

출아효모 Saccharomyces cerevisiae에서 RNA-binding 단백질인 Tho1은 mRNA가 전사되는 동안 초기 mRNA에 결합하여 mRNP 생성과 성숙한 mRNA의 핵에서 세포질로의 방출에 관여하는 것으로 여겨진다. 분열효모 Schizosaccharomyces pombe에서도 Tho1과 유사한 단백질을 암호화하는 유전자(spTho1로 명명)를 찾아 그 특성을 조사하였다. 이배체 S.pombe 균주에 하나의 spTho1 유전자만을 결실시킨 후 4분체분석을 수행한 결과, 이 유전자는 생장에 반드시 필요하지 않았다. 또한 spTho1 결실 돌연변이는 mRNA의 핵에서 세포질로의 방출도 정상적으로 보였다. 그러나 티아민에 의해 발현이 조절되는 강력한 프로모터를 이용하여 spTho1를 과발현시키면, 세포의 생장이 억제되었으며 $poly(A)^+$ RNA가 핵 안에 축적되었다. 이와 같은 결과들은 spTho1 유전자가 필수적이지는 않지만 mRNA의 핵에서 세포질로의 방출에 관여하고 있음을 시사한다.

• 생명과학회지
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• 제19권7호
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• pp.852-858
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• 2009

호흡전자전달계의 cytochrome bc$_1$ complex 또는 cytochrome c oxidase가 기능을 하지 않는 Rhodobacter sphaeroides mutant 내에서 pyridine nucleotide[NAD(P)H와 NAD(P)$^+$]의 농도와 redox 상태는 wild type과 비교할 때 큰 변화가 없었다. 높은 산소분압 조건에서 키운 Rhodobacter sphaeroides cbb$_3$ oxidase mutant 내에서 PrrBA two-component system에 의해서 조절되는 puf 오페론의 발현은 pyridine nucleotide나 전자전달계의 ubiquinone/ubiquinol pool의 redox 상태의 변화에 의해 유도된 것이 아니다. R. sphaeroides cytochrome bc$_1$ complex mutant를 이용하여 광합성기구 합성에 대한 cbb$_3$ cytochrome c oxidase의 억제 효과는 ubiquinone/ubiquinol pool의 redox 변화에 의해 간접적으로 일어나는 것이 아님을 증명하였다.