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Kim, Byung-Ho,Han, Yo Seb,Choe, Bong-Keun,Cho, Hyeseong,Nam, Gi Deog,Lee, Jin Woo,Kim, Young Il,Park, Jai Kyung,Dong, Seok Ho,Kim, Hyo Jong,Chang, Young-Woon,Lee, Joung-Il,Rin Chang KYUNG HEE UNIVERSITY MEDICAL CENTER 2006 고황의학상 수상논문집 Vol.21-22 No.-
Conditionally immortalized hepatocytes (CIH) established with a gene for the temperature-sensitive mutant of the T antigen (tsT) have characteristics to stop proliferating and to differentiate at nonpermissive temperatures (37-39℃) due to inactivation of the T antigen. Therefore, they may be a good alternative to primary hepatocytes for experimental investigations or clinical applications. Deinduction of the T antigen results in a transient increase of p53 in these cells, leading to reexpression of normal senescence because of the telomere attrition occurring during the early stages of immortalization. To determine this T antigen dependency for the maintenance of immortality, a type of rat CIH was cultured continuously at 39℃. The frequency of occurrence of T-antigen-independent clones ranged from 0.053% to 0.093%. These clones maintained the temperature-sensitive property of the T antigen; nevertheless, they were able to progress to the S phase and proliferate without undergoing apoptosis at 39℃ as at 33℃, a permissive temperature. The temperature-sensitive point mutation of tsT was not affected in these clones and the T antigen was functioning properly. The integrity of the p53 pathway was also maintained from the point of Western blot analysis of p21. Although the telomerase continued to be expressed and the telomere length was maintained, marked chromosomal damage could not be avoided in these cells. It is a plausible explanation that this escape phenomenon from conditional immortalization may be related to the change of other genes involved in cell cycles, which have yet to be elucidated. In conclusion, CIH could lose their temperature-sensitive characteristics without the change of tsT, itself, and the T antigen is not always necessary to maintain their immortality. Therefore, the results obtained from experimental investigations using these cells should be interpreted carefully, and unpredictable phenotypic changes should also be taken into consideration when using them in clinical applications.
Kim, Byung-Ho,Han, Yo Seb,Choe, Bong-Keun,Cho, Hyeseong,Nam, Gi Deog,Lee, Jin Woo,Kim, Young Il,Park, Jai Kyung,Dong, Seok Ho,Kim, Hyo Jong,Chang, Young Woon,Lee, Joung Il,Chang, Rin Cognizant Communication Corp. 2005 CELL TRANSPLANTATION Vol.14 No.7
<P>Conditionally immortalized hepatocytes (CIH) established with a gene for the temperature-sensitive mutant of the T antigen (tsT) have characteristics to stop proliferating and to differentiate at nonpermissive temperatures (37-39 degrees C) due to inactivation of the T antigen. Therefore, they may be a good alternative to primary hepatocytes for experimental investigations or clinical applications. Deinduction of the T antigen results in a transient increase of p53 in these cells, leading to reexpression of normal senescence because of the telomere attrition occurring during the early stages of immortalization. To determine this T antigen dependency for the maintenance of immortality, a type of rat CIH was cultured continuously at 39 degrees C. The frequency of occurrence of T-antigen-independent clones ranged from 0.053% to 0.093%. These clones maintained the temperature-sensitive property of the T antigen; nevertheless, they were able to progress to the S phase and proliferate without undergoing apoptosis at 39 degrees C as at 33 degrees C, a permissive temperature. The temperature-sensitive point mutation of tsT was not affected in these clones and the T antigen was functioning properly. The integrity of the p53 pathway was also maintained from the point of Western blot analysis of p21. Although the telomerase continued to be expressed and the telomere length was maintained, marked chromosomal damage could not be avoided in these cells. It is a plausible explanation that this escape phenomenon from conditional immortalization may be related to the change of other genes involved in cell cycles, which have yet to be elucidated. In conclusion, CIH could lose their temperature-sensitive characteristics without the change of tsT, itself, and the T antigen is not always necessary to maintain their immortality. Therefore, the results obtained from experimental investigations using these cells should be interpreted carefully, and unpredictable phenotypic changes should also be taken into consideration when using them in clinical applications.</P>
Hepatitis B virus X protein activates the ATM-Chk2 pathway and delays cell cycle progression
Kim, Sujeong,Lee, Ho-Soo,Ji, Jae-Hoon,Cho, Mi-Young,Yoo, Young-Suk,Park, Yong-Yea,Cha, Hyuk-Jin,Lee, Youngsoo,Kim, Youngbae,Cho, Hyeseong Microbiology Society 2015 The Journal of general virology Vol.96 No.8
<P>Genetic instability is intimately associated with tumour development. In particular, liver cancers associated with hepatitis B virus (HBV) exhibit high genetic instability; however, our understanding of the underlying molecular mechanisms remains limited. In this study, we found that γ-H2AX, a marker of DNA double-strand breaks (DSBs), and the levels of phospho-Chk2 (p-Chk2, the activated form) were significantly elevated in HBV-associated hepatocellular carcinomas and neighbouring regenerating nodules. Likewise, introduction of the pHBV or pMyc-HBx plasmids into cells induced accumulation of γ-H2AX foci and increased the p-Chk2 level. In these cells, inhibitory phosphorylation of Cdc25C phosphatase (Ser216) and CDK1 (Tyr15) was elevated; consequently, cell-cycle progression was delayed at G2/M phase, suggesting that activation of the ATM-Chk2 pathway by the HBV X protein (HBx) induces cell-cycle delay. Accordingly, inhibition of ataxia telangiectasia mutated (ATM) by caffeine or siRNA abolished the increase in the p-Chk2 level and restored the delayed CDK1 kinase activity in ChangX cells. We also found that cytoplasmic HBx, but not nuclear HBx, induced reactive oxygen species (ROS) production and led to the accumulation of γ-H2AX foci and the increased p-Chk2 level. Together, these data indicate that HBx-induced ROS accumulation induces DNA damage that activates the ATM-Chk2 pathway. Our findings provide insight into the mechanisms of HBV pathogenesis.</P>
Park, Min,Lee, Hyeseong,Jang, Ji-un,Park, Jong Hyuk,Kim, Chai Hwan,Kim, Seong Yun,Kim, Jaewoo Elsevier Applied Science Publishers 2019 Composites science and technology Vol.177 No.-
<P><B>Abstract</B></P> <P>Techniques for optimizing the dispersion of carbon nanotubes in composites by applying small amounts of additives in a simple manner are recognized as one of the most important core technologies in nanocomposite engineering. In this study, we reported the feasibility of phenyl glycidyl ether (PGE) as an effective noncovalent functionalization agent and suggested a facile and low-temperature process that applied high-speed rotation based on a planetary centrifugal mixer to improve the dispersion of multiwalled carbon nanotube (MWCNT) in the polyamide 6 (PA6) composite. PGE molecules were introduced on MWCNTs based on the π-π* interaction, resulting in enhanced MWCNT dispersion by preventing of the aggregation between the MWCNTs due to the van der Waals force. The tensile strength of the PA6 composite fiber filled with 1 wt% MWCNTs was improved up to 31.8% by the PGE treatment, indicating that PGE molecules were an effective noncovalent functionalization agent.</P>