Journal of Microbiology

Journal Article

LAMMER Kinase Governs the Expression and Cellular Localization of Gas2, a Key Regulator of Flocculation in Schizosaccharomyces pombe: Won-Hwa Kang , Yoon-Dong Park , Joo-Yeon Lim , Hee-Moon Park; J. Microbiol. 2024;62(1):21-31. Published online January 5, 2024; DOI: https://doi.org/10.1007/s12275-023-00097-7

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Abstract: It was reported that LAMMER kinase in Schizosaccharomyces pombe plays an important role in cation-dependent and galactose-specific flocculation. Analogous to other flocculating yeasts, when cell wall extracts of the Δlkh1 strain were treated to the wild-type strain, it displayed flocculation. Gas2, a 1,3-β-glucanosyl transferase, was isolated from the EDTA-extracted cell-surface proteins in the Δlkh1 strain. While disruption of the gas2+ gene was not lethal and reduced the flocculation activity of the Δlkh1 strain, the expression of a secreted form of Gas2, in which the GPI anchor addition sequences had been removed, conferred the ability to flocculate upon the WT strain. The Gas2-mediated flocculation was strongly inhibited by galactose but not by glucose. Immunostaining analysis showed that the cell surface localization of Gas2 was crucial for the flocculation of fission yeast. In addition, we identified the regulation of mbx2+ expression by Lkh1 using RT-qPCR. Taken together, we found that Lkh1 induces asexual flocculation by regulating not only the localization of Gas2 but also the transcription of gas2+ through Mbx2.

Nitric oxide in human cytomegalovirus replication and gene expression: Lee, Jee Yeon , Lee, Chan Hee; J. Microbiol. 1997;35(2):152-157.

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Abstract: Infection of human fibroblast (HF) cells with human cytomegalovirus (HCMV) result in changes in the intracellular level of second messengers. Since nitric oxide (NO) production has been known to be related with other second messengers, it is probable that HCMV infection of HF cells may involve NO. To test this possibility, the amount of NO was measured following HCMV infection but we were not able to detect significant change in the production of NO. Exogenous addition of NO generators such as sodium nitroprusside (SNP) or S-nitroso-N-a-cetylpenicillamine (SNAP) immediately after HCMV infection, however, inhibited virus multiplication. Furthermore, immunoblot experiment using monoclonal antibody to HCMV major immediate early (MIE) proteins or CAT assay using pCMVIE/CAT (plasmid containing CAT gene driven by HCMV MIE promoter) revealed that SNP or SNAP blocked the MIE gene expression. SNP was more effective than SNAP in hibiting HCMV multiplication or MIE gene expression. SNP produced more NO than SNAP in inhibiting HCMV multiplication or MIE gene expression. SNP produced more NO than SNAP. Although the mechanism for the inhibition of HCMV multiplication and MIE gene expression by NO is still elusive some correlation with NO-mediated inhibition of HCMV-induced increase in cytosolic free Ca^2+ concentration ([Ca^2+]) was observed. The increase of [Ca^2+] following HCMV infection was inhibited by SNP, and less effectively by SNAP. Raising [Ca^2+ with bromo-A23187 partially reversed the SNP block of MIE gene expression. Thus, there appear to e some relationships among NO. [Ca^2+], and HCMV MIE gene expression.

Expression of Human Cytomegalovirus Immediate Early US3 Gene in Human Fibroblast Cells: Gyu-Cheol Lee , Chong-Kyo Lee , Jin-Hyun Ahn , Chan-Hee Lee; J. Microbiol. 2000;38(1):24-30.

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Abstract: US3 gene is a member of the human cytomegalovirus (HCMV) immediate early gene. Although the precise functions of the US3 gene in HCMV replication and pathogenesis are not known, it has been reported to play a role in inhibiting major histocompatibility class I antigen presentation. For further knowledge of US3 gene expression, rabbit polyclonal antiserum of the US3 gene product was used for indirect immunofluorescence assay. In permissive human foreskin fibroblast (HFF) cells, US3 gene expression was detectable as crescent or half-moon shape in the perinuclear region at immediate early times after virus infection. HFF cells infected with mutant HCMV lacking US3 open reading frames were negative for US3 immunofluorescence assay. Double immunofluorescence assay using monoclonal antibody to gamma adaptin (specific for the Golgi complex) and rabbit anti-US3 antiserum revealed that US3 gene product could be localized to the Golgi complex. At later time after HCMV infection, US3 gene products were detected as globular aggregates in the cytosol. These aggregates were positive for gamma adaptin and stained with preimmune serum, suggesting a nonspecific reaction to the Golgi complex. Northern blot analysis revealed that transcription of US3 was observed only during immediate early times after virus infection (until 6 h postinfection). Therefore US3 gene expression appears to be confined to immediate early time and its gene products are localized to the Golgi complex as cres-cent shaped forms in the perinuclear cytoplasm.

Human Cytomegalovirus Inhibition of Interferon Signal Transduction: Daniel M. Miller , Colleen M. Cebulla , Daniel D. Sedmak; J. Microbiol. 2000;38(4):203-208.

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Abstract: Cytomegalovirus (CMV), a beta-herpesvirus with worldwide distribution, exhibits host persistence, a distinguishing characteristic of all herpesviruses. This persistence is dependent upon restricted gene expression in infected cells as well as the ability of productively infected cells to escape from normal cell-mediated anti-viral immunosurveillance. Type I (IFN-[alpha]/[beta]) and type II (IFN-[gamma]) interferons are major components of the innate defense system against viral infection. They are potent inducers of MHC class I and II antigens and of antigen processing proteins. Additionally, IFNs mediate direct anti-viral effects through induction of effector molecules that block viral infection and replication, such as 2', 5-oligoadenylate synthetase (2, 5-OAS). IFNs function through activation of well-defined signal transduction pathways that involve phosphorylation of constituent proteins and ultimate formation of active transcription factors. Recent studies have shown that a number of diverse viruses, including CMV, EBV, HPV, mumps and Ebola, are capable of inhibiting IFN-mediated signal transduction through a variety of mechanisms. As an example, CMV infection inhibits the ability of infected cells to transcribe HLA class I and II antigens as well as the antiviral effector molecules 2, 5-OAS and MxA I. EMSA studies have shown that IFN-[alpha] and IFN-[gamma] are unable to induce complete signal transduction in the presence of CMV infection, phenomena that are associated with specific decreases in JAK1 and p48. Viral inhibition of IFN signal transduction represents a new mechanistic paradigm for increased viral survival, a paradigm predicting widespread consequences in the case of signal transduction factors common to multiple cytokine pathways.

Measurement of Antiviral Activities Using Recombinant Human Cytomegalovirus: Byung-Hak Song , Gyu-Cheol Lee , Chan-Hee Lee; J. Microbiol. 2000;38(4):255-259.

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Abstract: For rapid and sensitive measurement of antiviral activities, application of a recombinant virus containing firefly luciferase gene was attempted. Recombinant human cytomegalovirus (HCMV) containing luciferase gene driven by HCMV late gene pp28 promoter (HCMV/pp28-luc) was used to test the antiviral activities of three known compounds and the result was compared with results from the conventional plaque assay for measuring the production of infectious viruses. When human fibroblast cells were infected with HCMV/pp28-luc, luciferase activity was observed at 2 days after infection and reached maximum at 6 days after infection, whereas the production of infectious virus was maximal at 4 days after infection. The antiviral activities of ganciclovir, acyclovir, and papaverine were measured in HFF cells infected with HCMV/pp28-luc and the luciferase activity was compared with the infectious virus titers. Luciferase activity decreased as the concentration of ganciclovir or papaverine increased, while there was a slight decrease in luciferase activity with acyclovir. The level of the decrease in luciferase activity was comparable to the level of decrease in the production of infectious virus. Therefore, the antiviral assay using recombinant virus HCMV/pp28-luc resulted in sensitivity similar to the conventional plaque assay with a significant reduction in assay time.

Induction of Apoptosis in Human Monocytes by Human Cytomegalovirus is Related with Calcium Increase: Myung Sook Moon , Gyu Cheol Lee , Chan H. Lee; J. Microbiol. 2002;40(3):224-229.

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Abstract: The effect of human cytomegalovirus (HCMV) on three human monocyte cell lines at different stages of differentiation was investigated. While the viability of HL-60 cells or U-937 cells was not significantly affected by HCMV infection, the viability of THP-1 cells was reduced. Acridine orange/ethidium bromide staining revealed that the reduction of THP-1 cell viability was due to increased apoptotic death following HCMV infection. Apoptosis in HL-60 cells was not affected by HCMV infection, and induction of apoptosis of U-937 cells by HCMV was intermediate between HL-60 and THP-1 cells. Since HL-60 cells are the least differentiated and THP-1 cells are the most differentiated, the induction of apoptosis of human monocytes appears to be related to the degree of cell differentiation. Flow cytometric and confocal microscopic studies using fluorescent calcium indicator Fluo-3 suggested a significant increase in intracellular free calcium concentration ([Ca^2+ ]_i ) in THP-1 cells undergoing apoptosis by HCMV infection. Again [Ca^2+ ]_i in HCMV-infected HL-60 cells was not critically altered, and that in HCMV-infected U-937 cells was intermediate between THP-1 cells and HL-60 cells. Calcium influx blockers such as verapamil and nifedipine partially reversed HCMV-induced apoptosis in THP-1 cells.

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