bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasminogen-Binding Activity of Neuraminidase Determines the Pathogenicity of Influenza A Virus
Authors: Goto Hideo , Wells Krisna , Takada Ayato , Kawaoka Yoshihiro 
Published: July 2002

ABSTRACT
When expressed in vitro, the neuraminidase (NA) of A/WSN/33 (WSN) virus binds and sequesters plasminogen on the cell surface, leading to enhanced cleavage of the viral hemagglutinin. To obtain direct evidence that the plasminogen-binding activity of the NA enhances the pathogenicity of WSN virus, we generated mutant viruses whose NAs lacked plasminogen-binding activity because of a mutation at the C terminus, from Lys to Arg or Leu. In the presence of trypsin, these mutant viruses replicated similarly to wild-type virus in cell culture. By contrast, in the presence of plasminogen, the mutant viruses failed to undergo multiple cycles of replication while the wild-type virus grew normally. The mutant viruses showed attenuated growth in mice and failed to grow at all in the brain. Furthermore, another mutant WSN virus, possessing an NA with a glycosylation site at position 130 (146 in N2 numbering), leading to the loss of neurovirulence, failed to grow in cell culture in the presence of plasminogen. We conclude that the plasminogen-binding activity of the WSN NA determines its pathogenicity in mice.
Murine Cytomegalovirus CC Chemokine Homolog MCK-2 (m131-129) Is a Determinant of Dissemination That Increases Inflammation at Initial Sites of Infection
Authors: Saederup Noah , Aguirre Shirley A. , Sparer Timothy E. , Bouley Donna M. , Mocarski Edward S. 
Published: July 2002

ABSTRACTThe murine cytomegalovirus CC chemokine homolog MCK-2 (m131-129) is an important determinant of dissemination during primary infection. Reduced peak levels of viremia at day 5 were followed by reduced levels of virus in salivary glands starting at day 7 whenmckinsertion (RM461) and point (RM4511) mutants were compared tomck-expressing viruses. A dramatic MCK-2-enhanced inflammation occurred at the inoculation site over the first few days of infection, preceding viremia. The data further reinforce the role of MCK-2 as a proinflammatory signal that recruits leukocytes to increase the efficiency of viral dissemination in the host.
The 5′ Untranslated Region of
Rhopalosiphum padi
Virus Contains an Internal Ribosome Entry Site Which Functions Efficiently in Mammalian, Plant, and Insect Translation Systems
Authors: Woolaway Kathryn E. , Lazaridis Konstantinos , Belsham Graham J. , Carter Michael J. , Roberts Lisa O. 
Published: July 2002

ABSTRACT

Rhopalosiphum padi
virus (RhPV) is one of several picorna-like viruses that infect insects; sequence analysis has revealed distinct differences between these agents and mammalian picornaviruses. RhPV has a single-stranded positive-sense RNA genome of about 10 kb; unlike the genomes of
Picornaviridae
, however, this genome contains two long open reading frames (ORFs). ORF1 encodes the virus nonstructural proteins, while the downstream ORF, ORF2, specifies the structural proteins. Both ORFs are preceded by long untranslated regions (UTRs). The intergenic UTR is known to contain an internal ribosome entry site (IRES) which directs non-AUG-initiated translation of ORF2. We have examined the 5′ UTR of RhPV for IRES activity by translating synthetic dicistronic mRNAs containing this sequence in a variety of systems. We now report that the 5′ UTR contains an element which directs internal initiation of protein synthesis from an AUG codon in mammalian, plant, and
Drosophila
in vitro translation systems. In contrast, the encephalomyocarditis virus IRES functions only in the mammalian system. The RhPV 5′ IRES element has features in common with picornavirus IRES elements, in that no coding sequence is required for IRES function, but also with cellular IRES elements, as deletion analysis indicates that this IRES element does not have sharply defined boundaries.
Comparison of Polymerase Subunits from Double-Stranded RNA Bacteriophages
Authors: Yang Hongyan , Makeyev Eugene V. , Bamford Dennis H. 
Published: July 2002

ABSTRACT

The family
Cystoviridae
comprises several bacteriophages with double-stranded RNA (dsRNA) genomes. We have previously purified the catalytic polymerase subunit (Pol) of one of the
Cystoviridae
members, bacteriophage φ6, and shown that the protein can catalyze RNA synthesis in vitro. In this reaction, both bacteriophage-specific and heterologous RNAs can serve as templates, but those containing 3′ termini from the φ6 minus strands are favored. This provides a molecular basis for the observation that only plus strands, not minus strands, are transcribed from φ6 dsRNA segments in vivo. To test whether such a regulatory mechanism is also found in other dsRNA viruses, we purified recombinant Pol subunits from the φ6-related bacteriophages φ8 and φ13 and assayed their polymerase activities in vitro. The enzymes catalyze template-dependent RNA synthesis using both single-stranded-RNA (ssRNA) and dsRNA templates. However, they differ from each other as well as from φ6 Pol in certain biochemical properties. Notably, each polymerase demonstrates a distinct preference for ssRNAs bearing short 3′-terminal sequences from the virus-specific minus strands. This suggests that, in addition to other factors, RNA transcription in
Cystoviridae
is controlled by the template specificity of the polymerase subunit.
Restoration of Function of Carboxy-Terminally Truncated Pseudorabies Virus Glycoprotein B by Point Mutations in the Ectodomain
Authors: Nixdorf Ralf , Klupp Barbara G. , Mettenleiter Thomas C. 
Published: July 2002

ABSTRACT

Glycoprotein B (gB) of pseudorabies virus (PrV) is essential for virus entry into target cells and direct viral cell-to-cell spread. Recently, we described a carboxy-terminally truncated derivative of PrV gB, gB-007, which was inefficiently incorporated into virions, was unable to complement infectivity, but was fully capable of restoring direct viral cell-to-cell spread of gB-negative PrV (R. Nixdorf, B. G. Klupp, and T. C. Mettenleiter, J. Virol. 74:7137–7145, 2000). Since recombinant PrV-007, which expresses gB-007 instead of wild-type gB, was able to spread directly from cell to cell, we attempted to obtain compensatory mutations leading to restoration of the entry defect by performing serial passages in cell culture. This procedure has previously been used to successfully restore entry defects in gD- or gL-deficient PrV mutants. From an initial titer of 100 PFU per ml in the supernatant, titers increased, reaching wild-type levels of up to 10
7
PFU after ca. 20 passages. One single-plaque isolate of the passaged mutant, designated PrV-007Pass, was further characterized. PrV-007Pass gB was efficiently incorporated into the viral envelope and restored infectivity to a gB-negative PrV mutant, PrV-gB
−
. Interestingly, localization of PrV-007Pass gB in the plasma membrane was similar to that of PrV-007. In contrast, wild-type gB is mainly found in intracellular vesicles. Marker rescue experiments and
trans
-complementation assays demonstrated the presence of compensatory mutations within the gB gene of PrV-007Pass. DNA sequencing revealed two point mutations in the gB open reading frame of PrV-007Pass, resulting in amino acid substitutions at positions 305 and 744 of gB, both of which are required for compensation of the defect in PrV-007. Our data again demonstrate the power of reversion analysis of herpesviruses and suggest that cytosolic and ectodomains play a role in incorporation of gB into virions.
Recovery of Infectious Pariacoto Virus from cDNA Clones and Identification of Susceptible Cell Lines
Authors: Johnson Karyn N. , Ball L. Andrew 
Published: July 2002

ABSTRACT

Pariacoto virus (PaV) is a nodavirus that was recently isolated in Peru from the Southern armyworm,
Spodoptera eridania
. Virus particles are non enveloped and about 30 nm in diameter and have
T
=3 icosahedral symmetry. The 3.0-Å crystal structure shows that about 35% of the genomic RNA is icosahedrally ordered, with the RNA forming a dodecahedral cage of 25-nucleotide (nt) duplexes that underlie the inner surface of the capsid. The PaV genome comprises two single-stranded, positive-sense RNAs: RNA1 (3,011 nt), which encodes the 108-kDa catalytic subunit of the RNA-dependent RNA polymerase, and RNA2 (1,311 nt), which encodes the 43-kDa capsid protein precursor α. In order to apply molecular genetics to the structure and assembly of PaV, we identified susceptible cell lines and developed a reverse genetic system for this virus. Cell lines that were susceptible to infection by PaV included those from
Spodoptera exigua, Helicoverpa zea
and
Aedes albopictus
, whereas cells from
Drosophila melanogaster
and
Spodoptera frugiperda
were refractory to infection. To recover virus from molecular clones, full-length cDNAs of PaV RNAs 1 and 2 were cotranscribed by T7 RNA polymerase in baby hamster kidney cells that expressed T7 RNA polymerase. Lysates of these cells were infectious both for cultured cells from
Helicoverpa zea
(corn earworm) and for larvae of
Galleria mellonella
(greater wax moth). The combination of infectious cDNA clones, cell culture infectivity, and the ability to produce milligram amounts of virus allows the application of DNA-based genetic methods to the study of PaV structure and assembly.
Two Functionally Distinct Forms of a Retroviral Receptor Explain the Nonreciprocal Receptor Interference among Subgroups B, D, and E Avian Leukosis Viruses
Authors: Adkins Heather B. , Blacklow Stephen C. , Young John A. T. 
Published: July 2002

ABSTRACTSubgroups B, D, and E avian leukosis viruses (ALV-B, -D, and -E) share the same chicken receptor, TVBS1, a tumor necrosis factor receptor (TNFR)-related protein. These viruses, however, exhibit nonreciprocal receptor interference (NRI): cells preinfected with ALV-B or ALV-D are resistant to superinfection by viruses of all three subgroups, whereas those pre-infected by ALV-E are resistant only to superinfection by other subgroup E viruses. In this study, we investigated the basis of this phenomenon by characterizing the interaction of TVBS1with ALV-B Env or ALV-E Env. Sequential immunoprecipitation analysis using surface envelope immunoglobulin fusion proteins revealed the existence of two separate types of TVBS1that are encoded by the same cDNA clone. One form, designated the type 1 receptor, is specific for ALV-B and ALV-E. The other form, the type 2 receptor, is specific for ALV-B. We show that a protein consisting of only the first and second extracellular cysteine-rich domains of TVBS1is capable of forming both receptor types. However, the third extracellular cysteine-rich domain is required for efficient formation of the type 1 receptor. We also demonstrate that heterogeneous N-linked glycosylation cannot explain the difference in activities of the two receptor types. The existence of two types of TVBS1explains the NRI pattern between ALV-B and -E: subgroup B viruses establish receptor interference with both receptor types, whereas subgroup E viruses interfere only with the type 1 receptor, leaving the type 2 receptor available to mediate subsequent rounds of ALV-B entry. The formation of a TVB receptor type that is specific for cytopathic ALV may also have important implications for understanding how some subgroups of ALV cause cell death.
Genetic Targeting of an Adenovirus Vector via Replacement of the Fiber Protein with the Phage T4 Fibritin
Authors: Krasnykh Victor , Belousova Natalya , Korokhov Nikolay , Mikheeva Galina , Curiel David T. 
Published: July 2002

ABSTRACT
The utility of adenovirus (Ad) vectors for gene therapy is restricted by their inability to selectively transduce disease-affected tissues. This limitation may be overcome by the derivation of vectors capable of interacting with receptors specifically expressed in the target tissue. Previous attempts to alter Ad tropism by genetic modification of the Ad fiber have had limited success due to structural conflicts between the fiber and the targeting ligand. Here we present a strategy to derive an Ad vector with enhanced targeting potential by a radical replacement of the fiber protein in the Ad capsid with a chimeric molecule containing a heterologous trimerization motif and a receptor-binding ligand. Our approach, which capitalized upon the overall structural similarity between the human Ad type 5 (Ad5) fiber and bacteriophage T4 fibritin proteins, has resulted in the generation of a genetically modified Ad5 incorporating chimeric fiber-fibritin proteins targeted to artificial receptor molecules. Gene transfer studies employing this novel viral vector have demonstrated its capacity to efficiently deliver a transgene payload to the target cells in a receptor-specific manner.
Adenovirus Hexon Protein Is a Potent Adjuvant for Activation of a Cellular Immune Response
Authors: Molinier-Frenkel Valérie , Lengagne Renée , Gaden Florence , Hong Saw-See , Choppin Jeannine , Gahery-Ségard Hanne , Boulanger Pierre , Guillet Jean-Gérard 
Published: July 2002

ABSTRACTThe capacity of recombinant adenoviruses (rAd) to induce immunization against their transgene products has been well documented. In the present study, we evaluated the vaccinal adjuvant role of rAd independently of its vector function. BALB/c mice received one subcutaneous injection of a mixture of six lipopeptides (LP6) used as a model immunogen, along with AdE1° (109particles), a first-generation rAd empty vector. Although coinjected with a suboptimal dose of lipopeptides, AdE1° significantly improved the effectiveness of the vaccination, even in the absence of booster immunization. In contrast to mice that received LP6 alone or LP6 plus a mock adjuvant, mice injected with AdE1° plus LP6 developed both a polyspecific T-helper type 1 response and an effector CD8 T-cell response specific to at least two class I-restricted epitopes. The helper response was still observed when immunization was performed using LP6 plus a mixture of soluble capsid components released from detergent-disrupted virions. When mice were immunized with LP6 and each individual capsid component, i.e., hexon, penton base, or fiber, the results obtained suggested that hexon protein was responsible for the adjuvant effect exerted by disrupted Ad particles on the helper response to the immunogen. Our results thus have some important implications not only in vaccinology but also for gene therapy using rAd vectors.
Redox Regulation of Adenovirus-Induced AP-1 Activation by Overexpression of Manganese-Containing Superoxide Dismutase
Authors: Zhang Hannah J. , Drake Victoria J. , Xu Linjing , Hu Jianfang , Domann Frederick E. , Oberley Larry W. , Kregel Kevin C. 
Published: July 2002

ABSTRACT

Adenovirus gene therapy is a promising tool in the clinical treatment of many genetic and acquired diseases. However, it has also caused pathogenic effects in organs such as the liver. The redox-sensitive transcription factors AP-1 and NF-κB have been implicated in these effects. To study the mechanisms of adenovirus-mediated AP-1 and NF-κB activation and the possible involvement of oxidative stress in adenovirus transduction, rats were injected with either replication-defective recombinant adenovirus with DNA containing the cytomegalovirus promoter region only (AdCMV), adenovirus containing human manganese-containing superoxide dismutase (MnSOD) cDNA (AdMnSOD), or vehicle. Compared to vehicle and AdCMV transduction, MnSOD gene transfer yielded a fivefold increase in liver MnSOD activity 7 days postinjection. Gel shift assay showed that AdCMV transduction induced DNA binding activity for AP-1 but not NF-κB. MnSOD overexpression abolished this activation. Western blotting analysis of c-Fos and c-Jun suggested that up-regulation of c-
fos
and c-
jun
gene expression does not directly contribute to the induction of AP-1 activation. Glutathione/glutathione disulfide ratios were decreased by adenovirus transduction and restored by MnSOD overexpression. The AP-1 binding activity that was induced by AdCMV was decreased by immunoprecipitation of Ref-1 protein. Ref-1 involvement was confirmed by restoration of AP-1 binding activity after the immunoprecipitated Ref-1 protein had been added back. AP-1 DNA binding activity was also elevated in control and AdMnSOD-injected rats after addition of the immunoprecipitated Ref-1 protein. These data indicate that cellular transduction by recombinant adenovirus stimulates AP-1 DNA binding activity. Furthermore, our results suggest that MnSOD overexpression decreases AP-1 DNA binding activity by regulating intracellular redox status, with the possible involvement of Ref-1 in this redox-sensitive pathway.
Role of Regulatory Elements and the MAPK/ERK or p38 MAPK Pathways for Activation of Human Cytomegalovirus Gene Expression
Authors: Chen Jiping , Stinski Mark F. 
Published: July 2002

ABSTRACT

A series of recombinant viruses with either site-specific mutations or various deletions of the early UL4 promoter of human cytomegalovirus were used to determine the roles of regulatory elements and the effects of the mitogen-activated protein kinase (MAPK) pathways. Viral gene expression was regulated by upstream
cis
-acting sites and by basic promoter elements that respond to the MAPK signal transduction pathways. Inhibitors of either the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway or the p38 MAPK pathway affected expression equally with either wild-type or mutant early UL4 promoters in the viral genome, indicating that the effects of the inhibitors are not exclusive for a single transcription factor. The minimal responsive element is the TATA box-containing early viral promoter.
Kaposi's Sarcoma-Associated Herpesvirus K3 Utilizes the Ubiquitin-Proteasome System in Routing Class I Major Histocompatibility Complexes to Late Endocytic Compartments
Authors: Lorenzo Mayra E. , Jung Jae U. , Ploegh Hidde L. 
Published: July 2002

ABSTRACTHuman herpesvirus 8 (HHV8) downregulates major histocompatibility complex (MHC) class I complexes from the plasma membrane via two of its genes, K3 and K5. The N termini of K3 and K5 contain a plant homeodomain (PHD) predicted to be structurally similar to RING domains found in E3 ubiquitin ligases. In view of the importance of the ubiquitin-proteasome system in sorting within the endocytic pathway, we analyzed its role in downregulation of MHC class I complexes in cells expressing K3. Proteasome inhibitors as well as cysteine and aspartyl protease inhibitors stabilize MHC class I complexes in cells expressing K3. However, proteasome inhibitors differentially affect sorting of MHC class I complexes within the endocytic pathway and prevent their delivery to a dense endosomal compartment. In this compartment, the cytoplasmic tail of MHC class I complexes is cleaved by cysteine proteases. The complex is then cleaved within the plane of the membrane by an aspartyl protease, resulting in a soluble MHC class I fragment composed of the lumenal domain of the heavy chain, β2-microglobulin (β2m), and peptide. We conclude that K3 not only directs internalization, but also targets MHC class I complexes to a dense endocytic compartment on the way to lysosomes in a ubiquitin-proteasome-dependent manner.
Langat Flavivirus Protease NS3 Binds Caspase-8 and Induces Apoptosis
Authors: Prikhod'ko Grigori G. , Prikhod'ko Elena A. , Pletnev Alexander G. , Cohen Jeffrey I. 
Published: July 2002

ABSTRACTThe flavivirus NS3 protein plays an important role in the cleavage and processing of the viral polyprotein and in the synthesis of the viral RNA. NS3 recruits NS2B and NS5 proteins to form complexes possessing protease and replicase activities through protease and nucleoside triphosphatase/helicase domains. We have found that NS3 also induces apoptosis. Expression of the Langat (LGT) virus NS3 protein resulted in a cleavage of cellular DNA and reduced the viability of cells. Coexpression of NS3 with apoptotic inhibitors (CrmA and P35) and addition of caspase peptide substrates (Z-VAD-FMK and Z-IETD-FMK) toNS3-transfected cells blocked NS3-induced apoptosis. In cotransfection experiments, NS3 bound to caspase-8 and enhanced caspase-8-mediated apoptosis. NS3 and caspase-8 colocalized in the cytoplasm of transfected cells. Deletion analysis demonstrated that at least two regions of NS3 contribute to its apoptotic activities. The protease and helicase domains are each able to bind to caspase-8, while the protease domain alone induces apoptosis. The protease domain and tetrahelix region of the helicase domain are required for NS3 to augment caspase-8-mediated apoptosis. Thus, the LGT virus NS3 protein is a multifunctional protein that binds to caspase-8 and induces apoptosis.
RelB-p50 NF-κB Complexes Are Selectively Induced by Cytomegalovirus Immediate-Early Protein 1: Differential Regulation of Bcl-xLPromoter Activity by NF-κB Family Members
Authors: Jiang H. Y. , Petrovas Constantinos , Sonenshein Gail E. 
Published: July 2002

ABSTRACTThe NF-κB/Rel family has been implicated in control of transcription of the Bcl-xLgene, a target which mediates cell survival signals. The cytomegalovirus (CMV) immediate-early protein 1 (IE1) was previously shown to induce NF-κB activity. Here, we report that in both vascular smooth muscle cells (SMCs) and NIH 3T3 cells, surprisingly, IE1 failed to induce Bcl-xLpromoter activity, although it induced activity of E8-CAT, a reporter construct driven by two copies of the NF-κB element upstream of the c-mycpromoter (upstream regulatory element [URE]). Thus, the subunit nature of the NF-κB/Rel factors induced by IE1 was examined using immunofluorescence and immunoblotting. IE1 was found to selectively induce nuclear RelB and p50 in SMCs and NIH 3T3 cells. An increase in RelB protein mediated by IE1 could, in part, be related to an increase in steady-staterelBmRNA levels. Consistent with this subunit identification, IE1 was unable to induce E8-CAT activity inrelB−/−murine embryonic fibroblast cells. In cotransfection analysis of SMCs and NIH 3T3 cells, RelB and p50 proteins failed to induce Bcl-xLpromoter activity while inducing E8-CAT. Furthermore, the NF-κB element of the Bcl-xLpromoter only weakly bound RelB-p50 complexes compared to the URE NF-κB element. Overall, these findings demonstrate in SMCs and NIH 3T3 cells that the CMV IE1 protein selectively induces RelB and p50, which fail to activate the Bcl-xLpromoter, indicating a strong specificity of binding and activity for the RelB member of the NF-κB family. Furthermore, our results implicate RelB in CMV infection of cells such as vascular SMCs.
Visualization of Polydnavirus Sequences in a Parasitoid Wasp Chromosome
Authors: Belle Elise , Beckage Nancy E. , Rousselet Jérôme , Poirié Marylène , Lemeunier Françoise , Drezen Jean-Michel 
Published: July 2002

ABSTRACT
Polydnaviruses, obligatorily associated with endoparasitoid wasps, are unique in that their segmented genome is composed of multiple double-stranded DNA circles. We present here the first cytological evidence that virus segments are integrated in the wasp genome, obtained by using in situ hybridization of virus probes with viral sequences in the chromosomes of a wasp from the braconid family of hymenopterans.