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- Notch Signal Transduction Induces a Novel Profile of Kaposi’s Sarcoma-Associated Herpesvirus Gene Expression
- Heesoon Chang
- J. Microbiol. 2006;44(2):217-225.
- DOI: https://doi.org/2362 [pii]
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Abstract
- Kaposi’s sarcoma-associated herpesvirus (KSHV) RTA transcription factor is recruited to its responsive elements through interaction with RBP-Jк that is a downstream transcription factor of the Notch signaling pathway that is important in development and cell fate determination. This suggests that KSHV RTA mimics cellular Notch signal transduction to activate viral lytic gene expression. Here, I demonstrated that unlike other B lymphoma cells, KSHV-infected primary effusion lymphoma BCBL1 cells displayed the constitutive activation of ligand-mediated Notch signal transduction, evidenced by the Jagged ligand expression and the complete proteolytic process of Notch receptor I. In order to investigate the effect of Notch signal transduction on KSHV gene expression, human Notch intracellular (hNIC) domain that constitutively activates RBP-Jк transcription factor activity was expressed in BCBL1 cells, TRExBCBL1-hNIC, in a tetracycline inducible manner. Gene expression profiling showed that like RTA, hNIC robustly induced expression of a number of viral genes including K5 immune modulatory gene resulting in downregulation of MHC I and CD54 surface expression. Finally, the genetic analysis of KSHV genome demonstrated that the hNIC-mediated expression of K5 during viral latency consequently conferred the downregulation of MHC I and CD54 surface expression. These results indicate that cellular Notch signal transduction provides a novel expression profiling of KSHV immune deregulatory gene that consequently confers the escape of host immune surveillance during viral latency.
- Identification of the Genes Involved in Stationary-Phase Specific Acid Resistance of Salmonella typhimurium
- Bang, Iel Soo , Lee, In Soo , Lee, Yung Nok , Park, Yong keun
- J. Microbiol. 1995;33(1):21-27.
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Abstract
- Salmonella encounters variables pH fluctuation during its life cycle and has been developed adaptative systems such as acid tolerance response (ATR) to survive at severe acidic environment. As part of on going investigation of stationary-phase specific acid resistance, we have searched for acid sensitive mutations in virulent Salmonella typhimurim UK-1 usin the MudJ fusion technique and two lethal selection procedures including DNP(dinitrophenol) selection media and microtiterplate selection method. Two acid sensitive mutations have been identified and designated, spatrK2, spatrK5. These mutations removed both stationary-phase acid tolerant effect and stationary-phase specific acid resistance. Non-specific histone like protein, H-NS and stationary-phase specific sigma factor, RpoS made little contribution to that system at respective single mutation(5-10 fold decrease). But, when both mutations were combined together, no acid resistance was achieved while acid tolerance response was still effective. Two dimensional SDS polyacrylamide gel electrophoresis showed new stationary-phase specific acid shock proteins as well as proteins already known. Not expectedly, the gels from acid adapted samples of both rpoS and hns mutation showed that double mutation of those regulators does not make change of the standard acid shock proteins. Only four acid shock proteins were regulated by these regulators, while fifteen proteins were newly identified as the members of acid shock response system by these regulators. These results implicate that stationary-phase acid resistance of that organism has RpoS/H-NS soubly dependent acid protective system and independent acid tolerance response system.
- Kinetic and spectral investigations on Ca^2+ and Sr^2+ containing methanol dehydrogenases
- Kim, Si Wouk , Kim, Chung, Sung , Lee, Jung Sup , Koh, Moon Joo , Yang, Song Suk , Duine, Johannis A. , Kim, Young Min
- J. Microbiol. 1997;35(3):200-205.
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Abstract
- Both Ca^2+ and Sr^2+ containing methanol dehydrogenases (MDH) were purified to homogeneity with yields of 48% and 42%, respectively, from Methylabacillus methanolovorus sp. strain SK5. Most of the biochemical and structural properties were similar to each other. However, some differences were found: (1) although the overall shape of the absorption spectrum of Sr^2+ MDH was very similar to that of Ca^2+ MDH, the absorption intensity originating from the cofactor in Sr^2+. MDH was higher than that in Ca^2+-MDH. Small blue shift of the maximum was also observed. These are probably due to a difference in redox state of the cofactors in Ca^2+ and Sr^2+ -MDH; (2)Sr^2+ -MDH was more heat-stable than Ca^2+-MDH above 56℃; (3) the V_max values for the methanol-dependent activities of Sr^2+ Ca^2+ -MDH in the presence of 3 mM KCN were 2.038 and 808 nmol/mg protein/min, respectively. In addition, the K_m values of Sr^2+ and Ca^2+ MDH for methanol were 12 and 21 uM, respectively; (4) the endogenous activity of Ca^2+ -MDH was more sensitive than that of Sr^2+ -MDH in the presence of cyanide; (5) Diethyl pyrocarbonate treatment increased the enzyme activities of Ca^2+ and Sr^2+ MDH 4.2 and 1.4 folds, respectively. These results indicate that Sr^2+ stabilizes the structural conformation and enhances the activity of MDH more than Ca^2+.
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