scholarly journals Combined structural, biochemical and cellular evidence demonstrates that both FGDF motifs in alphavirus nsP3 are required for efficient replication

Open Biology ◽  
2016 ◽  
Vol 6 (7) ◽  
pp. 160078 ◽  
Author(s):  
Tim Schulte ◽  
Lifeng Liu ◽  
Marc D. Panas ◽  
Bastian Thaa ◽  
Nicole Dickson ◽  
...  
Keyword(s):  
Viral Replication ◽  
Semliki Forest Virus ◽  
Protein Structures ◽  
Growth Curves ◽  
Structural Protein ◽  
Binding Studies ◽  
Efficient Replication ◽  
Hierarchical Interaction

Recent findings have highlighted the role of the Old World alphavirus non-structural protein 3 (nsP3) as a host defence modulator that functions by disrupting stress granules, subcellular phase-dense RNA/protein structures formed upon environmental stress. This disruption mechanism was largely explained through nsP3-mediated recruitment of the host G3BP protein via two tandem FGDF motifs. Here, we present the 1.9 Å resolution crystal structure of the NTF2-like domain of G3BP-1 in complex with a 25-residue peptide derived from Semliki Forest virus nsP3 (nsP3-25). The structure reveals a poly-complex of G3BP-1 dimers interconnected through the FGDF motifs in nsP3-25. Although in vitro and in vivo binding studies revealed a hierarchical interaction of the two FGDF motifs with G3BP-1, viral growth curves clearly demonstrated that two intact FGDF motifs are required for efficient viral replication. Chikungunya virus nsP3 also binds G3BP dimers via a hierarchical interaction, which was found to be critical for viral replication. These results highlight a conserved molecular mechanism in host cell modulation.

scholarly journals TRIM25 inhibits infectious bursal disease virus replication by targeting VP3 for ubiquitination and degradation

2021 ◽  
Vol 17 (9) ◽  
pp. e1009900
Author(s):  
Suyan Wang ◽  
Mengmeng Yu ◽  
Aijing Liu ◽  
Yuanling Bao ◽  
Xiaole Qi ◽  
...  
Keyword(s):  
Viral Replication ◽  
Disease Virus ◽  
Infectious Bursal Disease Virus ◽  
Defense Responses ◽  
Immune Defense ◽  
Infectious Bursal Disease ◽  
Structural Protein ◽  
Bursal Disease

Infectious bursal disease virus (IBDV), a double-stranded RNA virus, causes immunosuppression and high mortality in 3–6-week-old chickens. Innate immune defense is a physical barrier to restrict viral replication. After viral infection, the host shows crucial defense responses, such as stimulation of antiviral effectors to restrict viral replication. Here, we conducted RNA-seq in avian cells infected by IBDV and identified TRIM25 as a host restriction factor. Specifically, TRIM25 deficiency dramatically increased viral yields, whereas overexpression of TRIM25 significantly inhibited IBDV replication. Immunoprecipitation assays indicated that TRIM25 only interacted with VP3 among all viral proteins, mediating its K27-linked polyubiquitination and subsequent proteasomal degradation. Moreover, the Lys854 residue of VP3 was identified as the key target site for the ubiquitination catalyzed by TRIM25. The ubiquitination site destroyed enhanced the replication ability of IBDV in vitro and in vivo. These findings demonstrated that TRIM25 inhibited IBDV replication by specifically ubiquitinating and degrading the structural protein VP3.

scholarly journals Breakdown of Filamentous Myofibrils by the UPS–Step by Step

Biomolecules ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 110
Author(s):  
Dina Aweida ◽  
Shenhav Cohen
Keyword(s):  
Protein Quality ◽  
Protein Structures ◽  
Ubiquitin Proteasome System ◽  
Surface Proteins ◽  
Catalytic Core ◽  
Complex Protein ◽  
Ubiquitin Proteasome ◽  
Aaa Atpases

Protein degradation maintains cellular integrity by regulating virtually all biological processes, whereas impaired proteolysis perturbs protein quality control, and often leads to human disease. Two major proteolytic systems are responsible for protein breakdown in all cells: autophagy, which facilitates the loss of organelles, protein aggregates, and cell surface proteins; and the ubiquitin-proteasome system (UPS), which promotes degradation of mainly soluble proteins. Recent findings indicate that more complex protein structures, such as filamentous assemblies, which are not accessible to the catalytic core of the proteasome in vitro, can be efficiently degraded by this proteolytic machinery in systemic catabolic states in vivo. Mechanisms that loosen the filamentous structure seem to be activated first, hence increasing the accessibility of protein constituents to the UPS. In this review, we will discuss the mechanisms underlying the disassembly and loss of the intricate insoluble filamentous myofibrils, which are responsible for muscle contraction, and whose degradation by the UPS causes weakness and disability in aging and disease. Several lines of evidence indicate that myofibril breakdown occurs in a strictly ordered and controlled manner, and the function of AAA-ATPases is crucial for their disassembly and loss.

scholarly journals Furin Processing and Proteolytic Activation of Semliki Forest Virus

2003 ◽  
Vol 77 (5) ◽  
pp. 2981-2989 ◽  
Author(s):  
Xinyong Zhang ◽  
Martin Fugère ◽  
Robert Day ◽  
Margaret Kielian
Keyword(s):  
Conformational Changes ◽  
Secretory Pathway ◽  
Semliki Forest Virus ◽  
Fusion Reaction ◽  
Low Ph ◽  
Protein Fusion ◽  
Proteolytic Activation ◽  
Control Virus

ABSTRACT The alphavirus Semliki Forest virus (SFV) infects cells via a low-pH-dependent membrane fusion reaction mediated by the E1 envelope protein. Fusion is regulated by the interaction of E1 with the receptor-binding protein E2. E2 is synthesized as a precursor termed “p62,” which forms a stable heterodimer with E1 and is processed late in the secretory pathway by a cellular furin-like protease. Once processing to E2 occurs, the E1/E2 heterodimer is destabilized so that it is more readily dissociated by exposure to low pH, allowing fusion and infection. We have used FD11 cells, a furin-deficient CHO cell line, to characterize the processing of p62 and its role in the control of virus fusion and infection. p62 was not cleaved in FD11 cells and cleavage was restored in FD11 cell transfectants expressing human furin. Studies of unprocessed virus produced in FD11 cells (wt/p62) demonstrated that the p62 protein was efficiently cleaved by purified furin in vitro, without requiring prior exposure to low pH. wt/p62 virus particles were also processed during their endocytic uptake in furin-containing cells, resulting in more efficient virus infection. wt/p62 virus was compared with mutant L, in which p62 cleavage was blocked by mutation of the furin-recognition motif. wt/p62 and mutant L had similar fusion properties, requiring a much lower pH than control virus to trigger fusion and fusogenic E1 conformational changes. However, the in vivo infectivity of mutant L was more strongly inhibited than that of wt/p62, due to additional effects of the mutation on virus-cell binding.

scholarly journals Synergistic In Vitro Antiretroviral Activity of a Humanized Monoclonal Anti-CD4 Antibody (TNX-355) and Enfuvirtide (T-20)

2006 ◽  
Vol 50 (6) ◽  
pp. 2231-2233 ◽  
Author(s):  
Xing-Quan Zhang ◽  
Meredith Sorensen ◽  
Michael Fung ◽  
Robert T. Schooley
Keyword(s):  
Viral Replication ◽  
Viral Entry ◽  
Antiretroviral Agents ◽  
Entry Inhibitors ◽  
High Level ◽  
Antiretroviral Activity

ABSTRACT Recently, antiretroviral agents directed at several steps involved in viral entry have been shown to reduce viral replication in vitro and in vivo. We have demonstrated a high level of in vitro synergistic antiretroviral activity for two entry inhibitors that are directed at sequential steps in the entry process.

scholarly journals Semliki Forest virus vectors: efficient vehicles for in vitro and in vivo gene delivery

FEBS Letters ◽  
2001 ◽  
Vol 504 (3) ◽  
pp. 99-103 ◽  
Author(s):  
Kenneth Lundstrom ◽  
Christophe Schweitzer ◽  
Daniel Rotmann ◽  
Danielle Hermann ◽  
Edith M. Schneider ◽  
...  
Keyword(s):  
Gene Delivery ◽  
Semliki Forest Virus ◽  
Virus Vectors ◽  
In Vivo Gene Delivery

scholarly journals Interaction of Proteus mirabilis Urease Apoenzyme and Accessory Proteins Identified with Yeast Two-Hybrid Technology

2001 ◽  
Vol 183 (4) ◽  
pp. 1423-1433 ◽  
Author(s):  
Susan R. Heimer ◽  
Harry L. T. Mobley
Keyword(s):  
Proteus Mirabilis ◽  
Accessory Proteins ◽  
Structural Protein ◽  
Yeast Two Hybrid ◽  
Nickel Ions ◽  
Catalytically Active ◽  
Tract Infections ◽  
Two Hybrid

ABSTRACT Proteus mirabilis, a gram-negative bacterium associated with complicated urinary tract infections, produces a metalloenzyme urease which hydrolyzes urea to ammonia and carbon dioxide. The apourease is comprised of three structural subunits, UreA, UreB, and UreC, assembled as a homotrimer of individual UreABC heterotrimers (UreABC)3. To become catalytically active, apourease acquires divalent nickel ions through a poorly understood process involving four accessory proteins, UreD, UreE, UreF, and UreG. While homologues of UreD, UreF, and UreG have been copurified with apourease, it remains unclear specifically how these polypeptides associate with the apourease or each other. To identify interactions among P. mirabilis accessory proteins, in vitro immunoprecipitation and in vivo yeast two-hybrid assays were employed. A complex containing accessory protein UreD and structural protein UreC was isolated by immunoprecipitation and characterized with immunoblots. This association occurs independently of coaccessory proteins UreE, UreF, and UreG and structural protein UreA. In a yeast two-hybrid screen, UreD was found to directly interact in vivo with coaccessory protein UreF. Unique homomultimeric interactions of UreD and UreF were also detected in vivo. To substantiate the study of urease proteins with a yeast two-hybrid assay, previously described UreE dimers and homomultimeric UreA interactions among apourease trimers were confirmed in vivo. Similarly, a known structural interaction involving UreA and UreC was also verified. This report suggests that in vivo, P. mirabilis UreD may be important for recruitment of UreF to the apourease and that crucial homomultimeric associations occur among these accessory proteins.

scholarly journals Reductive Mobilization of Iron from Intact Ferritin: Mechanisms and Physiological Implication

2018 ◽  
Vol 11 (4) ◽  
pp. 120 ◽  
Author(s):  
Fadi Bou-Abdallah ◽  
John Paliakkara ◽  
Galina Melman ◽  
Artem Melman
Keyword(s):  
Protein Structures ◽  
Reducing Agents ◽  
Iron Core ◽  
Ferrous Ions ◽  
Major Pathway ◽  
Iron Mobilization ◽  
Iron Mineral ◽  
Mineral Core

Ferritins are highly conserved supramolecular protein nanostructures composed of two different subunit types, H (heavy) and L (light). The two subunits co-assemble into a 24-subunit heteropolymer, with tissue specific distributions, to form shell-like protein structures within which thousands of iron atoms are stored as a soluble inorganic ferric iron core. In-vitro (or in cell free systems), the mechanisms of iron(II) oxidation and formation of the mineral core have been extensively investigated, although it is still unclear how iron is loaded into the protein in-vivo. In contrast, there is a wide spread belief that the major pathway of iron mobilization from ferritin involves a lysosomal proteolytic degradation of ferritin, and the dissolution of the iron mineral core. However, it is still unclear whether other auxiliary iron mobilization mechanisms, involving physiological reducing agents and/or cellular reductases, contribute to the release of iron from ferritin. In vitro iron mobilization from ferritin can be achieved using different reducing agents, capable of easily reducing the ferritin iron core, to produce soluble ferrous ions that are subsequently chelated by strong iron(II)-chelating agents. Here, we review our current understanding of iron mobilization from ferritin by various reducing agents, and report on recent results from our laboratory, in support of a mechanism that involves a one-electron transfer through the protein shell to the iron mineral core. The physiological significance of the iron reductive mobilization from ferritin by the non-enzymatic FMN/NAD(P)H system is also discussed.

scholarly journals MERS-CoV Accessory ORFs Play Key Role for Infection and Pathogenesis

mBio ◽  
2017 ◽  
Vol 8 (4) ◽  
Author(s):  
Vineet D. Menachery ◽  
Hugh D. Mitchell ◽  
Adam S. Cockrell ◽  
Lisa E. Gralinski ◽  
Boyd L. Yount ◽  
...  
Keyword(s):  
Public Health ◽  
Viral Replication ◽  
Rapid Response ◽  
Mutant Virus ◽  
Global Public Health ◽  
Vaccine Platform ◽  
Zoonotic Pathogens ◽  
Related Group

ABSTRACT While dispensable for viral replication, coronavirus (CoV) accessory open reading frame (ORF) proteins often play critical roles during infection and pathogenesis. Utilizing a previously generated mutant, we demonstrate that the absence of all four Middle East respiratory syndrome CoV (MERS-CoV) accessory ORFs (deletion of ORF3, -4a, -4b, and -5 [dORF3-5]) has major implications for viral replication and pathogenesis. Importantly, attenuation of the dORF3-5 mutant is primarily driven by dysregulated host responses, including disrupted cell processes, augmented interferon (IFN) pathway activation, and robust inflammation. In vitro replication attenuation also extends to in vivo models, allowing use of dORF3-5 as a live attenuated vaccine platform. Finally, examination of ORF5 implicates a partial role in modulation of NF-κB-mediated inflammation. Together, the results demonstrate the importance of MERS-CoV accessory ORFs for pathogenesis and highlight them as potential targets for surveillance and therapeutic treatments moving forward. IMPORTANCE The initial emergence and periodic outbreaks of MERS-CoV highlight a continuing threat posed by zoonotic pathogens to global public health. In these studies, mutant virus generation demonstrates the necessity of accessory ORFs in regard to MERS-CoV infection and pathogenesis. With this in mind, accessory ORF functions can be targeted for both therapeutic and vaccine treatments in response to MERS-CoV and related group 2C coronaviruses. In addition, disruption of accessory ORFs in parallel may offer a rapid response platform to attenuation of future emergent strains based on both SARS- and MERS-CoV accessory ORF mutants. IMPORTANCE The initial emergence and periodic outbreaks of MERS-CoV highlight a continuing threat posed by zoonotic pathogens to global public health. In these studies, mutant virus generation demonstrates the necessity of accessory ORFs in regard to MERS-CoV infection and pathogenesis. With this in mind, accessory ORF functions can be targeted for both therapeutic and vaccine treatments in response to MERS-CoV and related group 2C coronaviruses. In addition, disruption of accessory ORFs in parallel may offer a rapid response platform to attenuation of future emergent strains based on both SARS- and MERS-CoV accessory ORF mutants.

Amino acid changes in the capsid protein of a reassortant betanodavirus strain: Effect on viral replication in vitro and in vivo

2018 ◽  
Vol 42 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Sandra Souto ◽  
José G. Olveira ◽  
Esther García-Rosado ◽  
Carlos P. Dopazo ◽  
Isabel Bandín
Keyword(s):  
Amino Acid ◽  
Viral Replication ◽  
Capsid Protein ◽  
Strain Effect

scholarly journals Nature, Position, and Frequency of Mutations Made in a Single Cycle of HIV-1 Replication

2010 ◽  
Vol 84 (19) ◽  
pp. 9864-9878 ◽  
Author(s):  
Michael E. Abram ◽  
Andrea L. Ferris ◽  
Wei Shao ◽  
W. Gregory Alvord ◽  
Stephen H. Hughes
Keyword(s):  
Viral Replication ◽  
Mutation Rate ◽  
Hot Spots ◽  
High Rate ◽  
Published Data ◽  
Single Cycle ◽  
Efficient System ◽  
Hiv 1

ABSTRACT There is considerable HIV-1 variation in patients. The extent of the variation is due to the high rate of viral replication, the high viral load, and the errors made during viral replication. Mutations can arise from errors made either by host DNA-dependent RNA polymerase II or by HIV-1 reverse transcriptase (RT), but the relative contributions of these two enzymes to the mutation rate are unknown. In addition, mutations in RT can affect its fidelity, but the effect of mutations in RT on the nature of the mutations that arise in vivo is poorly understood. We have developed an efficient system, based on existing technology, to analyze the mutations that arise in an HIV-1 vector in a single cycle of replication. A lacZα reporter gene is used to identify viral DNAs that contain mutations which are analyzed by DNA sequencing. The forward mutation rate in this system is 1.4 × 10−5 mutations/bp/cycle, equivalent to the retroviral average. This rate is about 3-fold lower than previously reported for HIV-1 in vivo and is much lower than what has been reported for purified HIV-1 RT in vitro. Although the mutation rate was not affected by the orientation of lacZα, the sites favored for mutations (hot spots) in lacZα depended on which strand of lacZα was present in the viral RNA. The pattern of hot spots seen in lacZα in vivo did not match any of the published data obtained when purified RT was used to copy lacZα in vitro.

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