• Korean Journal of Microbiology
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• v.52 no.1
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• pp.10-17
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• 2016

Enzyme immunoassay to analyze specific binding activity of antibody to antigen uses horseradish peroxidase (HRP) or alkaline phosphatase (AP). Chemical methods are usually used for coupling of these enzymes to antibody, which is complicated and random cross-linking process. As results, it causes decreases or loss of functional activity of either antibody or enzyme. In addition, most enzyme assays use secondary antibody to detect antigen binding activity of primary antibody. Enzymes coupled to secondary antibody provide a binding signal by substrate-based color development, suggesting secondary antibody is required in enzyme immunoassay. Additional incubation time for binding of secondary antibody should also be necessary. More importantly, non-specific binding activity caused by secondary antibody should also be eliminated. In this study, we cloned AP isolated from Escherichia coli (E. coli) chromosome by PCR and fused to) hAY4 single-chain variable domain fragment (ScFv) specific to death receptor (DR4) which is a receptor for tumor necrosis factor ${\alpha}$ related apoptosis induced ligand (TRAIL). hAY4 ScFv-AP expressed in E. coli showed 73.8 kDa as a monomer in SDS-PAGE. However, this fusion protein shown in size-exclusion chromatography (SEC) exhibited 147.6 kDa as a dimer confirming that natural dimerization of AP by non-covalent association induced ScFv-AP dimerization. In several immunoassay such as ELISA, Western blot and immunocytochemistry, it showed antigen binding activity by color development of substrates catalyzed by AP directly fused to primary hAY4 ScFv without secondary antibody. In summary, hAY4 ScFv-AP fusion protein was successfully purified as a soluble dimeric form in E. coli and showed antigen binding activity in several immunoassays without addition of secondary antibody which sometimes causes time-consuming, expensive and non-specific false binding.

• Journal of Life Science
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• v.23 no.10
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• pp.1230-1238
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• 2013

The regulatory effect of the tumor-suppressor protein p53 on the apoptogenic activity of $17{\alpha}$-estradiol ($17{\alpha}-E_2$) was compared between HCT116 ($p53^{+/+}$) and HCT116 ($p53^{-/-}$) cells. When the HCT116 ($p53^{+/+}$) and HCT116 ($p53^{-/-}$) cells were treated with $2.5{\sim}10{\mu}M$ $17{\alpha}-E_2$ for 48 h or with $10{\mu}M$for various time periods, cytotoxicity and an apoptotic sub-$G_1$ peak were induced in the HCT116 ($p53^{+/+}$) cells in a dose- and time-dependent manner. However, the HCT116 ($p53^{-/-}$) cells were much less sensitive to the apoptotic effect of $17{\alpha}-E_2$. Although $17{\alpha}-E_2$ induced aberrant mitotic spindle organization and incomplete chromosome congregation at the equatorial plate, $G_2/M$ arrest was induced to a similar extent in both cell types. In addition, $17{\alpha}-E_2$-induced activation of Bak and Bax, ${\Delta}{\Psi}m$ loss, and PARP degradation were more dominant in the HCT116 ($p53^{+/+}$) than in the HCT116 ($p53^{-/-}$) cells. In accordance with enhancement of p53 phosphorylation (Ser-15) and p53 levels, p21 and Bax levels were elevated in the HCT116 ($p53^{+/+}$) cells treated with $17{\alpha}-E_2$. The HCT116 ($p53^{-/-}$) cells exhibited barely or undetectable levels of p21 and Bax, regardless of $17{\alpha}-E_2$ treatment. On the other hand, although the level of Bcl-2 was slightly lower in the HCT116 ($p53^{+/+}$) than in the HCT116 ($p53^{-/-}$) cells, it remained relatively constant after the $17{\alpha}-E_2$ treatment. Together, these results show that among the components of the $17{\alpha}-E_2$-induced apoptotic-signaling pathway, which proceeds through mitotic spindle defects causing mitotic arrest, subsequent activation of Bak and Bax and the mitochondria-dependent caspase cascade, leading to PARP degradation, $17{\alpha}-E_2$-induced activation of Bak and Bax is the upstream target of proapoptotic action of p53.