Exosomes derived from HTLV-1 infected cells contain viral proteins and mRNA

The E3/19K glycoprotein of adenovirus functions to diminish recognition of adenovirus-infected cells by major histocompatibility complex class I-restricted cytotoxic T lymphocytes (CTLs) by binding intracellular class I molecules and preventing them from reaching the plasma membrane. In the present study we have characterized the nature of the interaction between E3/19K and the H-2Kd (Kd) molecule. An E3/19K molecule genetically engineered to terminate six residues from its normal COOH terminus (delta E19), was found to associate with Kd in a manner indistinguishable from wild-type E3/19K. Unlike E3/19K, however, delta E19 was transported through the Golgi complex to the plasma membrane, where it could be detected biochemically and immunocytochemically using a monoclonal antibody specific for the lumenal domain of E3/19K. Importantly, delta E19 also differed from E3/19K in being unable to prevent the presentation of Kd-restricted viral proteins to CTLs. This is unlikely to be due to delta E19 having a lower avidity for Kd than E3/19K, since delta E19 was able to compete with E3/19K for Kd binding, both physically, and functionally in nullifying the E3/19K blockade of antigen presentation. These findings indicate that the ability of E3/19K to block antigen presentation is due solely to its ability to retain newly synthesized class I molecules in the endoplasmic reticulum.

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Characterization of Viral Proteins Synthesized in 229E Infected Cells and Effect(s) of Inhibition of Glycosylation and Glycoprotein Transport

Advances in Experimental Medicine and Biology - Molecular Biology and Pathogenesis of Coronaviruses ◽

10.1007/978-1-4615-9373-7_6 ◽

1984 ◽

pp. 65-77 ◽

Cited By ~ 7

Author(s):

M. C. Kemp ◽

J. C. Hierholzer ◽

A. Harrison ◽

J. S. Burks

Keyword(s):

Viral Proteins ◽

Infected Cells ◽

Glycoprotein Transport

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Remodeling the Endoplasmic Reticulum by Poliovirus Infection and by Individual Viral Proteins: an Autophagy-Like Origin for Virus-Induced Vesicles

Journal of Virology ◽

10.1128/jvi.74.19.8953-8965.2000 ◽

2000 ◽

Vol 74 (19) ◽

pp. 8953-8965 ◽

Cited By ~ 360

Author(s):

David A. Suhy ◽

Thomas H. Giddings ◽

Karla Kirkegaard

Keyword(s):

Endoplasmic Reticulum ◽

Mammalian Cells ◽

Buoyant Density ◽

Rna Replication ◽

Viral Proteins ◽

Replication Complex ◽

Poliovirus Infection ◽

Endosomal Membranes ◽

Infected Cells ◽

Positive Strand Rna

ABSTRACT All positive-strand RNA viruses of eukaryotes studied assemble RNA replication complexes on the surfaces of cytoplasmic membranes. Infection of mammalian cells with poliovirus and other picornaviruses results in the accumulation of dramatically rearranged and vesiculated membranes. Poliovirus-induced membranes did not cofractionate with endoplasmic reticulum (ER), lysosomes, mitochondria, or the majority of Golgi-derived or endosomal membranes in buoyant density gradients, although changes in ionic strength affected ER and virus-induced vesicles, but not other cellular organelles, similarly. When expressed in isolation, two viral proteins of the poliovirus RNA replication complex, 3A and 2C, cofractionated with ER membranes. However, in cells that expressed 2BC, a proteolytic precursor of the 2B and 2C proteins, membranes identical in buoyant density to those observed during poliovirus infection were formed. When coexpressed with 2BC, viral protein 3A was quantitatively incorporated into these fractions, and the membranes formed were ultrastructurally similar to those in poliovirus-infected cells. These data argue that poliovirus-induced vesicles derive from the ER by the action of viral proteins 2BC and 3A by a mechanism that excludes resident host proteins. The double-membraned morphology, cytosolic content, and apparent ER origin of poliovirus-induced membranes are all consistent with an autophagic origin for these membranes.

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Copatching and Lipid Raft Association of Different Viral Glycoproteins Expressed on the Surfaces of Pseudorabies Virus-Infected Cells

Journal of Virology ◽

10.1128/jvi.78.10.5279-5287.2004 ◽

2004 ◽

Vol 78 (10) ◽

pp. 5279-5287 ◽

Cited By ~ 25

Author(s):

Herman W. Favoreel ◽

Thomas C. Mettenleiter ◽

Hans J. Nauwynck

Keyword(s):

Lipid Rafts ◽

Lipid Raft ◽

Plasma Membranes ◽

Pseudorabies Virus ◽

Viral Proteins ◽

Viral Envelope ◽

Viral Glycoprotein ◽

Monospecific Antibody ◽

Infected Cells ◽

Simplex Virus

ABSTRACT Pseudorabies virus (PRV) is a swine alphaherpesvirus that is closely related to human herpes simplex virus (HSV). Both PRV and HSV express a variety of viral envelope glycoproteins in the plasma membranes of infected cells. Here we show that at least four major PRV glycoproteins (gB, gC, gD, and gE) in the plasma membrane of infected swine kidney cells and monocytes seem to be linked, since monospecific antibody-induced patching of any one of these proteins results in copatching of the others. Further, for all four PRV glycoproteins, monospecific antibody-induced patches were enriched in GM1, a typical marker of lipid raft microdomains, but were excluded for transferrin receptor, a nonraft marker, suggesting that these viral proteins may associate with lipid rafts. However, only gB and, to a lesser extent, gE were found in lipid raft fractions by using detergent floatation assays, indicating that gC and gD do not show strong lipid raft association. Addition of methyl-β-cyclodextrin (MCD), a cholesterol-depleting agent that is commonly used to disrupt lipid rafts, only slightly reduced copatching efficiency between the different viral proteins, indicating that other factors, perhaps tegument-glycoprotein interactions, may be important for the observed copatching events. On the other hand, MCD strongly reduced polarization of the antibody-induced viral glycoprotein patches to a cap structure, a gE-dependent process that has been described for specific PRV- and HSV-infected cells. Therefore, we hypothesize that efficient gE-mediated capping of antibody-antigen patches may require the lipid raft-associated signal transduction machinery.

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Nuclear Factor NF45 Interacts with Viral Proteins of Infectious Bursal Disease Virus and Inhibits Viral Replication

Journal of Virology ◽

10.1128/jvi.02506-09 ◽

2010 ◽

Vol 84 (20) ◽

pp. 10592-10605 ◽

Cited By ~ 30

Author(s):

Ruth L. O. Stricker ◽

Sven-Erik Behrens ◽

Egbert Mundt

Keyword(s):

Viral Replication ◽

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Molecular Mechanisms ◽

Viral Proteins ◽

Infectious Bursal Disease ◽

Nuclear Factor ◽

Replication Process ◽

Bursal Disease ◽

Infected Cells

ABSTRACT Two of the central issues in developing new strategies to interfere with viral infections concern the identification of cellular proteins involved in viral replication and/or antiviral measures and the dissection of the underlying molecular mechanisms. To gain initial insight into the role of host proteins in the life cycle of infectious bursal disease virus (IBDV), a double-stranded RNA virus, we examined the cellular nuclear factor 45 (NF45). NF45 was previously indicated to be involved in the replication process of other types of RNA viruses. Interestingly, by performing immunofluorescence studies, we found that in IBDV-infected cells the mainly nuclear NF45 accumulated at the sites of viral replication in the cytoplasm. NF45 was shown to specifically colocalize with the viral RNA-dependent RNA polymerase VP1, the capsid protein VP2, and the ribonucleoprotein VP3. Immunoprecipitation experiments indicated protein-protein associations between NF45 and VP1, VP2, and VP3. Expression of the individual VP3 or the combination of expression of VP1 and VP3 did not result in a cytoplasmic accumulation of NF45, which, among other data, showed that recruitment of the cellular protein in infected cells functionally correlates with the viral replication process. Since small interfering RNA(siRNA)-mediated downregulation of NF45 resulted in an approximately 5-fold increase of virus yield, our study suggests that NF45, by association with viral proteins, is part of a yet-uncharacterized cellular defense mechanism against IBDV infections.

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Effects of Major Capsid Proteins, Capsid Assembly, and DNA Cleavage/Packaging on the pUL17/pUL25 Complex of Herpes Simplex Virus 1

Journal of Virology ◽

10.1128/jvi.01658-09 ◽

2009 ◽

Vol 83 (24) ◽

pp. 12725-12737 ◽

Cited By ~ 15

Author(s):

Luella Scholtes ◽

Joel D. Baines

Keyword(s):

Herpes Simplex Virus ◽

Herpes Simplex ◽

Nuclear Localization ◽

Conformational Changes ◽

Viral Proteins ◽

Dna Packaging ◽

Capsid Proteins ◽

Herpes Simplex Virus 1 ◽

Infected Cells ◽

Simplex Virus

ABSTRACT The UL17 and UL25 proteins (pUL17 and pUL25, respectively) of herpes simplex virus 1 are located at the external surface of capsids and are essential for DNA packaging and DNA retention in the capsid, respectively. The current studies were undertaken to determine whether DNA packaging or capsid assembly affected the pUL17/pUL25 interaction. We found that pUL17 and pUL25 coimmunoprecipitated from cells infected with wild-type virus, whereas the major capsid protein VP5 (encoded by the UL19 gene) did not coimmunoprecipitate with these proteins under stringent conditions. In addition, pUL17 (i) coimmunoprecipitated with pUL25 in the absence of other viral proteins, (ii) coimmunoprecipitated with pUL25 from lysates of infected cells in the presence or absence of VP5, (iii) did not coimmunoprecipitate efficiently with pUL25 in the absence of the triplex protein VP23 (encoded by the UL18 gene), (iv) required pUL25 for proper solubilization and localization within the viral replication compartment, (v) was essential for the sole nuclear localization of pUL25, and (vi) required capsid proteins VP5 and VP23 for nuclear localization and normal levels of immunoreactivity in an indirect immunofluorescence assay. Proper localization of pUL25 in infected cell nuclei required pUL17, pUL32, and the major capsid proteins VP5 and VP23, but not the DNA packaging protein pUL15. The data suggest that VP23 or triplexes augment the pUL17/pUL25 interaction and that VP23 and VP5 induce conformational changes in pUL17 and pUL25, exposing epitopes that are otherwise partially masked in infected cells. These conformational changes can occur in the absence of DNA packaging. The data indicate that the pUL17/pUL25 complex requires multiple viral proteins and functions for proper localization and biochemical behavior in the infected cell.

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The Human Cytomegalovirus UL51 Protein Is Essential for Viral Genome Cleavage-Packaging and Interacts with the Terminase Subunits pUL56 and pUL89

Journal of Virology ◽

10.1128/jvi.01955-12 ◽

2012 ◽

Vol 87 (3) ◽

pp. 1720-1732 ◽

Cited By ~ 55

Author(s):

Eva Maria Borst ◽

Jennifer Kleine-Albers ◽

Ildar Gabaev ◽

Marina Babić ◽

Karen Wagner ◽

...

Keyword(s):

Human Cytomegalovirus ◽

Unit Length ◽

Viral Proteins ◽

Enzymatic Process ◽

Genome Packaging ◽

Subnuclear Localization ◽

Promising Target ◽

Synthetic Ligand ◽

Infected Cells ◽

Hcmv Replication

ABSTRACTCleavage of human cytomegalovirus (HCMV) genomes as well as their packaging into capsids is an enzymatic process mediated by viral proteins and therefore a promising target for antiviral therapy. The HCMV proteins pUL56 and pUL89 form the terminase and play a central role in cleavage-packaging, but several additional viral proteins, including pUL51, had been suggested to contribute to this process, although they remain largely uncharacterized. To study the function of pUL51 in infected cells, we constructed HCMV mutants encoding epitope-tagged versions of pUL51 and used a conditionally replicating virus (HCMV-UL51-ddFKBP), in which pUL51 levels could be regulated by a synthetic ligand. In cells infected with HCMV-UL51-ddFKBP, viral DNA replication was not affected when pUL51 was knocked down. However, no unit-length genomes and no DNA-filled C capsids were found, indicating that cleavage of concatemeric HCMV DNA and genome packaging into capsids did not occur in the absence of pUL51. pUL51 was expressed mainly with late kinetics and was targeted to nuclear replication compartments, where it colocalized with pUL56 and pUL89. Upon pUL51 knockdown, pUL56 and pUL89 were no longer detectable in replication compartments, suggesting that pUL51 is needed for their correct subnuclear localization. Moreover, pUL51 was found in a complex with the terminase subunits pUL56 and pUL89. Our data provide evidence that pUL51 is crucial for HCMV genome cleavage-packaging and may represent a third component of the viral terminase complex. Interference with the interactions between the terminase subunits by antiviral drugs could be a strategy to disrupt the HCMV replication cycle.

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Host Shutoff in Influenza A Virus: Many Means to an End

Viruses ◽

10.3390/v10090475 ◽

2018 ◽

Vol 10 (9) ◽

pp. 475 ◽

Cited By ~ 14

Author(s):

Rachel Levene ◽

Marta Gaglia

Keyword(s):

Immune Responses ◽

Influenza A Virus ◽

Influenza A ◽

Rna Synthesis ◽

Viral Proteins ◽

Host Gene Expression ◽

Structural Protein ◽

Infected Cells ◽

Host Shutoff ◽

Virus Replication Cycle

Influenza A virus carries few of its own proteins, but uses them effectively to take control of the infected cells and avoid immune responses. Over the years, host shutoff, the widespread down-regulation of host gene expression, has emerged as a key process that contributes to cellular takeover in infected cells. Interestingly, multiple mechanisms of host shutoff have been described in influenza A virus, involving changes in translation, RNA synthesis and stability. Several viral proteins, notably the non-structural protein NS1, the RNA-dependent RNA polymerase and the endoribonuclease PA-X have been implicated in host shutoff. This multitude of host shutoff mechanisms indicates that host shutoff is an important component of the influenza A virus replication cycle. Here we review the various mechanisms of host shutoff in influenza A virus and the evidence that they contribute to immune evasion and/or viral replication. We also discuss what the purpose of having multiple mechanisms may be.

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