• BMB Reports
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• v.41 no.9
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• pp.678-683
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• 2008

The initial step during assembly of the hepatitis A virus particle is driven by domain 2A of P1-2A, which is the precursor of the structural proteins. The proteolytic removal of 2A from particulate VP1-2A by an as yet unknown host enzyme presumably terminates viral morphogenesis. Using a genetic approach, we show that a basic amino acid residue at the C-terminus of VP1 is required for efficient particle assembly and that host proteases trypsin and cathepsin L remove 2A from hepatitis A virus particles in vitro. Analyses of insertion mutants in the C-terminus of 2A reveal that this part of 2A is important for liberation of P1-2A from the polyprotein. The data provide the first evidence that the VP1/2A junction is involved in both viral particle assembly and maturation and, therefore, seems to coordinate the first and last steps in viral morphogenesis.

• BMB Reports
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• v.46 no.10
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• pp.495-500
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• 2013

Turnip yellow mosaic virus (TYMV) is a positive strand RNA virus. We have modified TYMV coat protein (CP) by inserting a c-Myc epitope peptide at the N- or C-terminus of the CP, and have examined its effect on assembly. We introduced the recombinant CP constructs into Nicotiana benthamiana leaves by agroinfiltration. Examination of the leaf extracts by agarose gel electrophoresis and Western blot analysis showed that the CP modified at the N-terminus produced a band co-migrating with wild-type virions. With C-terminal modification, however, the detected bands moved faster than the wild-type virions. To further examine the effect, TYMV constructs producing the modified CPs were prepared. With N-terminal modification, viral RNAs were protected from RNase A. In contrast, the viral RNAs were not protected with C-terminal modification. Overall, the results suggest that virion assembly and RNA packaging occur properly when the N-terminus of CP is modified, but not when the C-terminus is modified.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.651-651
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• 2013

Templated strategy is a very powerful tool for creating multi-dimensional self assembly of nanomaterials. Since viral protein cages have a uniform size with a well-defined structure, they can serve as an excellent template for the formation of a three-dimensional self-assembly of synthetic nanoparticles. In this study, we have examined the feasibility of the 3D self-assembly of gold nanoparticles of various sizes using a brome mosaic virus (BMV) capsid with cysteine groups expressed on its surface as a scaffold for the assembly. It was found that the three-dimensional clusters of gold nanoparticles with a designed structure were attainable by this approach, which was verified by transmission electron microscope (TEM) and dynamic light scattering (DLS) analysis.

• Research in Plant Disease
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• v.11 no.2
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• pp.98-105
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• 2005

All viruses have few genes relative to their hosts. Viruses, thus, utilize many host factors for efficient viral replication in host cell. Virus-host interactions are crucial determinations of host range, replication, and pathology. Host factors participate in most steps of positive-strand RNA virus infection, including entry, viral gene expression, virion assembly, and release. Recent data show that host factors play important roles in assembling the viral RNA replication complex, selecting and recruiting viral RNA replication templates, activating the viral complex for RNA synthesis, and the other steps. These virus-host interactions may contribute to the host specificity and/or pathology. Positive-strand RNA viruses encompass over two-thirds of all virus genera and include numerous pathogens. This review focuses on the importance of host factors involved in positive strand plant RNA virus genome replication.

• The Plant Pathology Journal
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• v.33 no.3
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• pp.213-228
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• 2017

Plasmodesmata (PDs) are specialized intercellular channels that facilitate the exchange of various molecules, including sugars, ribonucleoprotein complexes, transcription factors, and mRNA. Their diameters, estimated to be 2.5 nm in the neck region, are too small to transfer viruses or viral genomes. Tobacco mosaic virus and Potexviruses are the most extensively studied viruses. In viruses, the movement protein (MP) is responsible for the PD gating that allows the intercellular movement of viral genomes. Various host factors interact with MP to regulate complicated mechanisms related to PD gating. Virus replication and assembly occur in viral replication complex (VRC) with membrane association, especially in the endoplasmic reticulum. VRC have a highly organized structure and are highly regulated by interactions among the various host factors, proteins encoded by the viral genome, and the viral genome. Virus trafficking requires host machineries, such as the cytoskeleton and the secretory systems. MP facilitates the virus replication and movement process. Despite the current level of understanding of virus movement, there are still many unknown and complex interactions between virus replication and virus movement. While numerous studies have been conducted to understand plant viruses with regards to cell-to-cell movement and replication, there are still many knowledge gaps. To study these interactions, adequate research tools must be used such as molecular, and biochemical techniques. Without such tools, virologists will not be able to gain an accurate or detailed understanding of the virus infection process.

• Molecules and Cells
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• v.37 no.2
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• pp.140-148
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• 2014

We identified four basic amino acid residues as nuclear localization signals (NLS) in the C-terminal domain of the prototype foamy viral (PFV) integrase (IN) protein that were essential for viral replication. We constructed seven point mutants in the C-terminal domain by changing the lysine and arginine at residues 305, 308, 313, 315, 318, 324, and 329 to threonine or proline, respectively, to identify residues conferring NLS activity. Our results showed that mutation of these residues had no effect on expression assembly, release of viral particles, or in vitro recombinant IN enzymatic activity. However, mutations at residues 305 (R ${\rightarrow}$ T), 313(R ${\rightarrow}$ T), 315(R ${\rightarrow}$ P), and 329(R ${\rightarrow}$ T) lead to the production of defective viral particles with loss of infectivity, whereas non-defective mutations at residues 308(R ${\rightarrow}$ T), 318(K ${\rightarrow}$ T), and 324(K ${\rightarrow}$ T) did not show any adverse effects on subsequent production or release of viral particles. Sub-cellular fractionation and immunostaining for viral protein PFV-IN and PFV-Gag localization revealed predominant cytoplasmic localization of PFV-IN in defective mutants, whereas cytoplasmic and nuclear localization of PFV-IN was observed in wild type and non-defective mutants. However sub-cellular localization of PFV-Gag resulted in predominant nuclear localization and less presence in the cytoplasm of the wild type and non-defective mutants. But defective mutants showed only nuclear localization of Gag. Therefore, we postulate that four basic arginine residues at 305, 313, 315 and 329 confer the karyoplilic properties of PFV-IN and are essential for successful viral integration and replication.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.14-14
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• 2003

Potato virus X (PVX), the type member of Potexvirus genus, is a flexuous rod-shaped virus containing a single-stranded (＋) RNA. Infection by PVX produces genomic plus- and minus-strand RNAs and two major subgenomic RNAs (sgRNAs). To understand the mechanism for PVX replication, we are studying the cis- and/or trans-acting elements required for RNA replication. Previous studies have shown that the conserved sequences located upstream of two major sgRNAs, as well as elements in the 5' non-translated region (NTR) affect accumulation of genomic and sg RNAs. Complementarity between sequences at the 5' NTR and those located upstream of two major sgRNAs and the binding of host protein(s) to the 5' NTR have shown to be important for PVX RNA replication. The 5 NTR of PVX contains single-stranded AC-rich sequence and stem-loop structure. The potential role(s) of these cis-elements on virus replication, assembly, and their interaction with viral and host protein(s) during virus infection will be discussed based on the data obtained by in vitro binding, in vitro assembly, gel shift mobility assay, host gene expression profiling using various mutants at these regions.

• Korean Journal of Poultry Science
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• v.48 no.2
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• pp.81-90
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• 2021

Avian influenza viruses (AIVs) must utilize host cellular factors to complete their life cycle, and fragile X mental retardation protein (FMRP) has been reported to be a host factor promoting AIV ribonucleoprotein (vRNP) assembly and exports vRNP from the nucleus to the cytoplasm. The functional role of chicken FMRP translational regulator 1 (cFMR1) as a host factor of AIV is, however, poorly understood. In this study, we targeted the cFMR1 gene in DF1 cells using clustered regularly interspaced short palindromic repeats/Cas9-mediated genome editing to examine the functional role of cFMR1 as a host factor of AIV. We found that cFMR1 stimulated viral gene transcription during early stages of the viruses' life cycle and did not affect viral progeny production and viral polymerase activity in DF1 cells 24 hours post infection. cFMR1 overexpression did not exert significant effects on virus production, compared to the control. Therefore, unlike in mammalian systems (e.g., humans or mice), cFMR1 did not play a pivotal role in AIV but only seemed to stimulate viral proliferation during early stages of the viral life cycle. These results imply that the interplay between host factors and AIV differs between mammals and avian species, and such differences should be considered when developing anti-viral drugs for birds or establishing AIV-resistant bird models.

• BMB Reports
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• v.38 no.4
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• pp.381-385
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• 2005

Severe acute respiratory syndrome (SARS) is an emerging infectious disease associated with a novel coronavirus (CoV) that was identified and molecularly characterized in 2003. Previous studies on various coronaviruses indicate that protein-protein interactions amongst various coronavirus proteins are critical for viral assembly and morphogenesis. It is necessary to elucidate the molecular mechanism of SARS-CoV replication and rationalize the anti-SARS therapeutic intervention. In this study, we employed an in vitro GST pull-down assay to investigate the interaction between the membrane (M) and the nucleocapsid (N) proteins. Our results show that the interaction between the M and N proteins does take place in vitro. Moreover, we provide an evidence that 12 amino acids domain (194-205) in the M protein is responsible for binding to N protein. Our work will help shed light on the molecular mechanism of the virus assembly and provide valuable information pertaining to rationalization of future anti-viral strategies.

• BMB Reports
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• v.51 no.5
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• pp.219-224
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• 2018

Necroptosis is an emerging form of programmed cell death occurring via active and well-regulated necrosis, distinct from apoptosis morphologically, and biochemically. Necroptosis is mainly unmasked when apoptosis is compromised in response to tumor necrosis factor alpha. Unlike apoptotic cells, which are cleared by macrophages or neighboring cells, necrotic cells release danger signals, triggering inflammation, and exacerbating tissue damage. Evidence increasingly suggests that programmed necrosis is not only associated with pathophysiology of disease, but also induces innate immune response to viral infection. Therefore, necroptotic cell death plays both physiological and pathological roles. Physiologically, necroptosis induce an innate immune response as well as premature assembly of viral particles in cells infected with virus that abrogates host apoptotic machinery. On the other hand, necroptosis per se is detrimental, causing various diseases such as sepsis, neurodegenerative diseases and ischemic reperfusion injury. This review discusses the signaling pathways leading to necroptosis, associated necroptotic proteins with target-specific inhibitors and diseases involved. Several studies currently focus on protective approaches to inhibiting necroptotic cell death. In cancer biology, however, anticancer drug resistance severely hampers the efficacy of chemotherapy based on apoptosis. Pharmacological switch of cell death finds therapeutic application in drug- resistant cancers. Therefore, the possible clinical role of necroptosis in cancer control will be discussed in brief.