• Korean Journal of Microbiology
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• v.38 no.3
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• pp.221-229
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• 2002

Japanese encephalitis virus (JEV) persistence was established and maintained in Vero cell culture for over 1 year. Eleven clones of plaque morphology mutant JEV, with large and small plaque sizes, were obtained from the cell culture supernatant. Genomic RNA replication efficiency of the mutants in naive Vero cell appeared to correspond to their different plaque sizes. No significant changes in envelop protein ORF or in non-coding regions at both ends of the RNA genome suggested that there could be an unidentified factor(s) playing role in JEV attenuation. Unlike to the replication of wild-type JEV, the mutants did not induce severe degree of cytopathic effect in Vero cells upon infection. While obvious decrease of Bcl-2 and its mRNA expression and sharp increase of p53 in naive Vero cells infected with either wild-type JEV or the large plaque-forming mutant, those changes were not observed with the small plaque-forming one. Together with these observation, internucleosomal DNA fragmentation and chromosomal DNA profile in the Vero cells infected with the mutants suggest that an overall changes in cytopathic effect in the plaque morphology mutants-infected cells should be primarily due to the reduced genomic RNA replication and the compromised degree of p53-independent apoptosis by the virus infection at least in part.

• Korean Journal of Microbiology
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• v.29 no.2
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• pp.75-79
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• 1991

The yeast L-A virus (4.6 kb dsRNA genome) encodes the major coat protein and a "gag-pol" fusion minor coat protein that separately encapsidate itself and $M_{1}$, a 1.8 kb dsRNA satellite virus encoding a secreted protein toxin (the killer toxin). The teast chromosomal SKI genes prevent viral cytopathology by lowering the virus copy number. Thus, $ski^{-}$ mutants are ts and cs for growth. We transformed a ski2-2 virus-infested mutant with a yeast bank in a high copy cloning vector and selected the rare healthy transformants for analysis. One type of transformant segregated M-O L-A-O cells with high frequency. Elimination of the DNA clone from the ski2-2 strain eliminated this phinotype and introduction of the DNA clone recovered from such transformants into the parent ski2-2 strain, or into ski3 or ski6 mutants gave the same phenotype. This killer-curing phenotype was due to the curing of the helper L-A dsRNA virus. The 6.5 kb insert only had this activity when carried on a high copy vector and in $ski^{-}$ cells (not in $SKI^{+}$ cells). This 6.5 kb insert acts as a mutagen on L-A dsRNA producing a high rate of deletion mutations.mutations.

• Molecules and Cells
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• v.19 no.1
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• pp.81-87
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• 2005

Phytochelatins play an important role in heavy metal detoxification in plants as well as in other organisms. The Arabidopsis thaliana mutant cad1-3 does not produce detectable levels of phytochelatins in response to cadmium stress. The hypersensitivity of cad1-3 to cadmium stress is attributed to a mutation in the phytochelatin synthase 1 (AtPCS1) gene. However, A. thaliana also contains a functional phytochelatin synthase 2 (AtPCS2). In this study, we investigated why the cad1-3 mutant is hypersensitive to cadmium stress despite the presence of AtPCS2. Northern and Western blot analyses showed that expression of AtPCS2 is weak compared to AtPCS1 in both roots and shoots of transgenic Arabidopsis. The lower level of AtPCS2 expression was confirmed by RT-PCR analysis of wild type Arabidopsis. Moreover, no tissue-specific expression of AtPCS2 was observed. Even when AtPCS2 was under the control of the AtPCS1 promoter or of the cauliflower mosaic virus 35S promoter (CaMV 35S) it was not capable of fully complementing the cad1-3 mutant for cadmium resistance.

• The Journal of Korean Society of Virology
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• v.29 no.3
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• pp.183-193
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• 1999

Human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein is synthesized as a 160 KDa precursor, gp160, that is cleaved by a cellular protease to form the gp120 and gp41 subunits. Mammalian expression vectors were designed that are capable of efficient expression of various mutant envelope glycoproteins derived from a molecular clone of HIV-1. To construct these vectors, one type of mutation was made at the gp120-gp41 cleavage site by oligonucleotide-directed mutagenesis. And another mutation was made to change amino acids in the membrane spanning region of HIV-1 gp41 important for membrane anchorage. Next, these two mutations were combined to generate a vector to have double mutations in cleavage site and membrane-spanning region. These mutants were transiently expressed in mammalian cells. The effect of these mutations on envelope glycoprotein synthesis, proteolytic processing and secretion was determined. In addition, cell surface expression and ability of the glycoprotein to induce syncytium formation were examined. This study provides a mammalian expression system that is capable of efficient expression and secretion of soluble gp160.

• The Plant Pathology Journal
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• v.15 no.1
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• pp.38-43
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• 1999

Mutants of the monopartite geminivirus beet curly top virus (BCTV) have been screened for infectivity, systemic movement, replication and symptom development in Arabidopsis thaliana. As known by coding for coat protein, R1 mutant was not infectious and did not move systemically. R2, R3 and L2/L3 mutants produced milder symptoms compared to wild type BCTV but the infectivity was reduced by 40% to 60%. R2 ORF is thought to be involved in the regulation of ssDNA and dsDNA accumulation because only dsDNA was accumulated on R2-infected organs. Disruption of ORF L4 resulted in reduced infections, but the viral DNA was accumulated in infected organs from roots to shoot tips as much as wild type BCTV on Sei-O. In addition, 4 mutants did not produce callus-like tissues on infected organs, suggesting that L4 ORF may play a role in the induction of host cell divisions by virus infection. This result was supported by the patterns of mRNA expression and promoter analysis of the cell cycle marker gene, cycl, on Arabidopsis. cycl mRNA was accumulated on symptomatic organs by wild type BCTV infections but not by L4 mutant. We conclude that the BCTV L4 ORF is essential for symptom developments, specially callus-like formation on infected organs.

• Korean Journal of Microbiology
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• v.30 no.6
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• pp.472-478
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• 1992

Synthesis of the pol gene products of HTLV-I requires rihosomes to shift frame twice in - I direction while translating genome-size mRNA. We havc made a lI1utagcni/cd RNA in which the gag and pro genes are aligned to allow synthe,.is of a largcr amount of the Gag-Pro-Pol polyproteins by a single frameshifting. Using this mutant, wc could examine the questions whether the predicted RNA secondary or tertiary structure downstream of the shift site is operative as a determinant for - I frameshifting. Deletion analysis showed that the stem-loop structure is essential for efficient frameshifting in the pro-pol overlap, but formation of a pseudoknot is less important.

• Journal of Information Processing Systems
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• v.11 no.2
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• pp.280-294
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• 2015

This paper presents the infectious watermarking model (IWM) for the protection of video contents that are based on biological virus modeling by the infectious route and procedure. Our infectious watermarking is designed as a new paradigm protection for video contents, regarding the hidden watermark for video protection as an infectious virus, video content as host, and codec as contagion medium. We used pathogen, mutant, and contagion as the infectious watermark and defined the techniques of infectious watermark generation and authentication, kernel-based infectious watermarking, and content-based infectious watermarking. We experimented with our watermarking model by using existing watermarking methods as kernel-based infectious watermarking and content-based infectious watermarking medium, and verified the practical applications of our model based on these experiments.

• The Plant Pathology Journal
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• v.39 no.6
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• pp.592-599
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• 2023

A defective RNA3 (D3Yα) of strain Y of cucumber mosaic virus (CMV-Y) was examined on host-specific maintenance, experimental conditions, and a viral factor required for its generation in plants. D3Yα was stably maintained in cucumber but not in tomato plants for 28 days post inoculation (dpi). D3Yα was generated in Nicotiana tabacum or N. benthamiana after prolonged infection in the second and the third passages, but not in plants of N. benthamiana grown at low temperature at 28 dpi or infected with CMV-Y mutant that had the 2b gene deleted. Collectively, we suggest that generation and retention of D3Yα depends on potential host plants and experimental conditions, and that the 2b protein has a role for facilitation of generation of D3Yα.

• Microbiology and Biotechnology Letters
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• v.43 no.1
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• pp.1-8
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• 2015

In this study, a DNA-launched reverse genetics system was developed from a type 2 porcine reproductive and respiratory syndrome virus (PRRSV) strain, KNU-12. The complete genome of 15,412 nucleotides was assembled as a single cDNA clone and placed under the eukaryotic CMV promoter. Upon transfection of BHK-tailless pCD163 cells with a full-length cDNA clone, viable and infectious type 2 progeny PRRSV were rescued. The reconstituted virus was found to maintain growth properties similar to those of the parental virus in porcine alveolar macrophage (PAM) cells. With the availability of this type 2 PRRSV infectious clone, we first explored the biological relevance of ORF5a in the PRRSV replication cycle. Therefore, we used a PRRSV reverse genetics system to generate an ORF5a knockout mutant clone by changing the ORF5a translation start codon and introducing a stop codon at the 7^th codon of ORF5a. The ORF5a knockout mutant was found to exhibit a lack of infectivity in both BHK-tailless pCD163 and PAM-pCD163 cells, suggesting that inactivation of ORF5a expression is lethal for infectious virus production. In order to restore the ORF5a gene-deleted PRRSV, complementing cell lines were established to stably express the ORF5a protein of PRRSV. ORF5a-expressing cells were capable of supporting the production of the replicationdefective virus, indicating complementation of the impaired ORF5a gene function of PRRSV in trans.

• BMB Reports
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• v.33 no.1
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• pp.63-68
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• 2000

Most baculoviruses have an ecdysteroid UDP-glucosyltransferase (egt) gene, whose product inactivates ecdysteroid within the infected host. Bomhyx mori larvae infected with BmEGTZ, a mutant B. mori nucleopolyhedrovirus (BmNPV) in which the egt gene has been inactivated, die more rapidly compared to larvae infected with wild-type BmNPV. In this study, the profile of hemolymph proteins, and progression of virus infection in BmEGTZ- and BmNPV-infected B. mori larvae, was analyzed by SDS-PAGE and histochemically. These analyses showed that virus-encoded and virus-induced proteins were expressed quicker in BmEGTZ-infected larvae than in BmNPV-infected larvae. This suggests that the decrease in time to death, following BmEGTZ infection, results from the stimulation of virus-specific protein expression. In order to examine the effect of ecdysteroid on virus transmission, the profile of hemolymph proteins, and progression of virus infection, were analyzed following an ecdysteroid injection of BmEGTZ- or BmNPV-infected larvae. In the BmNPV-infected larvae, ecdysteroid treatment had no apparent effect on hemolymph protein expression. This suggests that the injected ecdysteroid was inactivated by the BmNPV-expressed ecdysteroid UDP-glucosyltransferase. An Ecdysteroid injection into BmEGTZ-infected larvae increased the speed of virus-specific protein expression and virus transmission. These results suggest that ecdysteroid stimulates protein expression, which in tum results in the stimulation of virus transmission.