Journal of Microbiology

Hyon E Choy

3 Articles

Effect of Iron on Cytolysin A Expression in Salmonella enterica serovar Typhi: Jinghua Cui , Honghua Piao , Shen Jin , Hee Sam Na , Yeongjin Hong , Hyon E Choy , Phil Youl Ryu; J. Microbiol. 2009;47(4):479-485. Published online September 9, 2009; DOI: https://doi.org/10.1007/s12275-009-0039-4

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Previously, a novel protein ClyA (Cytolysin A) has been identified in Escherichia coli K-12, Salmonella enterica serovars Typhi and Paratyphi A and Shigella. Salmonella spp. synthesize substantial amounts of ClyA upon infection of the human host, although the mechanism by which ClyA is induced in vivo is unclear. Since environmental signals could control the expression of virulence determinants, ClyA expression in S. Typhi Ty2 was tested by Western blotting in the presence of normal pooled human serum (NPS). The level of ClyA expression increased in the presence of NPS in a concentration-dependent manner. RPMI 1640 medium similarly induced ClyA expression. ClyA expression was inversely proportional to the concentration of iron in RPMI medium. Therefore, we speculated that iron inhibited the expression of ClyA in S. Typhi Ty2, and free iron depletion may be one of the causes of S. Typhi-mediated induction of ClyA in vivo. Transcription from a clyA-lacZ fusion gene decreased as iron concentration increased, but not as significantly as the ClyA protein expression. It is concluded that the regulatory effect of iron on clyA expression is mainly at translational level.

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Expression of Bacteroides fragilis hemolysins in vivo and role of HlyBA in an intra‐abdominal infection model
Leandro A. Lobo, Audrey L. Jenkins, C. Jeffrey Smith, Edson R. Rocha
MicrobiologyOpen.2013; 2(2): 326. CrossRef
Molecular cloning and characterization of clyA genes in various serotypes of Salmonella enterica
Lan Ji Huang, Jinghua Cui, Hong Hua Piao, Yeongjin Hong, Hyon E. Choy, Phil Youl Ryu
The Journal of Microbiology.2010; 48(5): 663. CrossRef

Expression of c-Myc Is Related to Host Cell Death Following Salmonella typhimurium Infection in Macrophage: Jihyoun Seong , Hong Hua Piao , Phil Yeoul Ryu , Youn Uck Kim , Hyon E Choy , Yeongjin Hong; J. Microbiol. 2009;47(2):214-219. Published online May 2, 2009; DOI: https://doi.org/10.1007/s12275-008-0308-7

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Abstract PDF

It has been known that ornithine decarboxylase (ODC) induced by the binding of c-Myc to odc gene is closely linked to cell death. Here, we investigated the relationship between their expressions and cell death in macrophage cells following treatment with Salmonella typhimurium or lipopolysaccharide (LPS). ODC expression was increased by bacteria or LPS and repressed by inhibitors against mitogen-activated protein kinases (MAPKs) in Toll-like receptor 4 (TLR4) signaling pathway. In contrast, c-Myc protein level was increased after treatment with bacteria, but not by treatment with LPS or heat-killed bacteria although both bacteria and LPS increased the levels of c-myc mRNA to a similar extent. c-Myc protein level is dependent upon bacterial invasion because treatment with cytochalasin D (CCD), inhibitors of endocytosis, decreased c-Myc protein level. The cell death induced by bacteria was significantly decreased after treatment of CCD or c-Myc inhibitor, indicating that cell death by S. typhimurium infection is related to c-Myc, but not ODC. Consistent with this conclusion, treatment with bacteria mutated to host invasion did not increase c-Myc protein level and cell death rate. Taken together, it is suggested that induction of c-Myc by live bacterial infection is directly related to host cell death.

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G-quadruplex-targeting indoloquinoxaline derivative modulates host immunity against Leishmania donovani
Joyshree Karmakar, Sarmistha Pal, Maximilian Johannes Braun, Sk Jubayar Ahashan, Harald Schwalbe, Jyotirmayee Dash
NAR Molecular Medicine.2025;[Epub] CrossRef
Enhanced bacterial cancer therapy delivering therapeutic RNA interference of c-Myc
Jason S. Williams, Adam T. Higgins, Katie J. Stott, Carly Thomas, Lydia Farrell, Cleo S. Bonnet, Severina Peneva, Anna V. Derrick, Trevor Hay, Tianqi Wang, Claire Morgan, Sarah Dwyer, Joshua D’Ambrogio, Catherine Hogan, Matthew J. Smalley, Lee Parry, Paul
Cell & Bioscience.2024;[Epub] CrossRef
The deadly bite of Salmonella Typhi
Kaiyi Zhang, Mathias Hornef, Marcus Fulde
The EMBO Reports.2015; 16(8): 887. CrossRef
A role for c-Myc in regulating anti-mycobacterial responses
Howard C. H. Yim, James C. B. Li, John C. H. Pong, Allan S. Y. Lau
Proceedings of the National Academy of Sciences.2011; 108(43): 17749. CrossRef

Identification of Genes Differentially Expressed in RAW264.7 Cells Infected by Salmonella typhimurium Using PCR Method: Kyung Ho Kang , Jung A Song , Dong-Jun Shin , Hyon E Choy , Yeongjin Hong; J. Microbiol. 2007;45(1):29-33.; DOI: https://doi.org/2495 [pii]

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Abstract PDF: Salmonella typhimurium, causing mouse typhoid, infects hosts such as macrophage cells, and proliferates in intracellular vacuoles causing infected cells to trigger numerous genes to respond against the infection. In this study, we tried to identify such genes in RAW264.7 cells by using the PCR screening method with degenerate primers. Fourteen genes were found to be differentially expressed after a 4 h infection in which the expression of 8 genes increased while expression of the others decreased. Most of the genes were involved in proinflammatory responses such as cytokines production and cell death. The mutation in msbB gene encoding the myristoyl transferase in lipid A of lipopolysaccharide (LPS) resulted in much lower toxicity to the inoculated animals. We compared the expression of the identified genes in wild-type and msbB-mutated S. typhimurium infections and found that Lyzs encoding lysozyme type M was differentially expressed. This gene is quite likely to be related to bacterial survival in the host cells.

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