bluuebunny/crossref_metadata_2025_split huggingface dataset:
Autographa californica
Multiple Nucleopolyhedrovirus
exon0
(
orf141
), Which Encodes a RING Finger Protein, Is Required for Efficient Production of Budded Virus
Authors: Dai Xiaojiang , Stewart Taryn M. , Pathakamuri Joseph A. , Li Qianjun , Theilmann David A. 
Published: August 2004

ABSTRACT

exon0
(
orf141
) of
Autographa californica
multiple nucleopolyhedrovirus (Ac
M
NPV) is a highly conserved baculovirus gene that codes for a predicted 261-amino-acid protein. Located in the C-terminal region of EXON0 are a predicted leucine-rich coiled-coil domain and a RING finger motif. The 5′ 114 nucleotides of
exon0
form part of
ie0
, which is a spliced gene expressed at very early times postinfection, but transcriptional analysis revealed that
exon0
is transcribed as a late gene. To determine the role of
exon0
in the baculovirus life cycle, we used Ac
M
NPV bacmids and generated
exon0
knockout viruses (Ac-exon0-KO) by recombination in
Escherichia coli
. Ac-exon0-KO progressed through the very late phases in Sf9 cells, as evidenced by the development of occlusion bodies in the nuclei of the transfected or infected cells. However, production of budded virus (BV) in Ac-exon0-KO-infected cells was reduced at least 3 orders of magnitude in comparison to that in wild-type virus infection. Microscopy revealed that Ac-exon0-KO was restricted primarily to the cells initially infected, exhibiting a single-cell infection phenotype. Slot blot assays and Western blot analysis indicated that
exon0
deletion did not affect the onset or levels of viral DNA replication or the expression of IE1, IE0, and GP64 prior to BV release. These results demonstrate that
exon0
is required for efficient production of BV in the Ac
M
NPV life cycle but does not affect late occlusion-derived virus.
Mechanism of CD150 (SLAM) Down Regulation from the Host Cell Surface by Measles Virus Hemagglutinin Protein
Authors: Welstead G. Grant , Hsu Eric C. , Iorio Caterina , Bolotin Shelly , Richardson Christopher D. 
Published: August 2004

ABSTRACTMeasles virus has been reported to enter host cells via either of two cellular receptors, CD46 and CD150 (SLAM). CD46 is found on most cells of higher primates, while SLAM is expressed on activated B, T, and dendritic cells and is an important regulatory molecule of the immune system. Previous reports have shown that measles virus can down regulate expression of its two cellular receptors on the host cell surface during infection. In this study, the process of down regulation of SLAM by measles virus was investigated. We demonstrated that expression of the hemagglutinin (H) protein of measles virus was sufficient for down regulation. Our studies provided evidence that interactions between H and SLAM in the endoplasmic reticulum (ER) can promote the down regulation of SLAM but not CD46. In addition, we demonstrated that interactions between H and SLAM at the host cell surface can also contribute to SLAM down regulation. These results indicate that two mechanisms involving either intracellular interactions between H and SLAM in the ER or receptor-mediated binding to H at the surfaces of host cells can lead to the down regulation of SLAM during measles virus infection.
The Conserved Carboxy Terminus of the Capsid Domain of Human Immunodeficiency Virus Type 1 Gag Protein Is Important for Virion Assembly and Release
Authors: Melamed Daniel , Mark-Danieli Michal , Kenan-Eichler Michal , Kraus Osnat , Castiel Asher , Laham Nihay , Pupko Tal , Glaser Fabian , Ben-Tal Nir , Bacharach Eran 
Published: August 2004

ABSTRACT
The retroviral Gag precursor plays an important role in the assembly of virion particles. The capsid (CA) protein of the Gag molecule makes a major contribution to this process. In the crystal structure of the free CA protein of the human immunodeficiency virus type 1 (HIV-1), 11 residues of the C terminus were found to be unstructured, and to date no information exists on the structure of these residues in the context of the Gag precursor molecule. We performed phylogenetic analysis and demonstrated a high degree of conservation of these 11 amino acids. Deletion of this cluster or introduction of various point mutations into these residues resulted in significant impairment of particle infectivity. In this cluster, two putative structural regions were identified, residues that form a hinge region (353-VGGP-356) and those that contribute to an α-helix (357-GHKARVL-363). Overall, mutations in these regions resulted in inhibition of virion production, but mutations in the hinge region demonstrated the most significant reduction. Although all the Gag mutants appeared to have normal Gag-Gag and Gag-RNA interactions, the hinge mutants were characterized by abnormal formation of cytoplasmic Gag complexes. Gag proteins with mutations in the hinge region demonstrated normal membrane association but aberrant rod-like membrane structures. More detailed analysis of these structures in one of the mutants demonstrated abnormal trapped Gag assemblies. These data suggest that the conserved CA C terminus is important for HIV-1 virion assembly and release and define a putative target for drug design geared to inhibit the HIV-1 assembly process.
VP16-Dependent Association of Chromatin-Modifying Coactivators and Underrepresentation of Histones at Immediate-Early Gene Promoters during Herpes Simplex Virus Infection
Authors: Herrera Francisco J. , Triezenberg Steven J. 
Published: August 2004

ABSTRACT
During infection by herpes simplex virus type 1 (HSV-1), the virion protein VP16 activates the transcription of viral immediate-early (IE) genes. Genetic and biochemical assays have shown that the potent transcriptional activation domain of VP16 can associate with general transcription factors and with chromatin-modifying coactivator proteins of several types. The latter interactions are particularly intriguing because previous reports indicate that HSV-1 DNA does not become nucleosomal during lytic infection. In the present work, chemical cross-linking and immunoprecipitation assays were used to probe the presence of activators, general transcription factors, and chromatin-modifying coactivators at IE gene promoters during infection of HeLa cells by wild-type HSV-1 and by RP5, a viral strain lacking the VP16 transcriptional activation domain. The presence of VP16 and Oct-1 at IE promoters did not depend on the activation domain. In contrast, association of RNA polymerase II, TATA-binding protein, histone acetyltransferases (p300 and CBP), and ATP-dependent remodeling proteins (BRG1 and hBRM) with IE gene promoters was observed in wild-type infections but was absent or reduced in cells infected by RP5. In contrast to the previous evidence for nonnucleosomal HSV-1 DNA, histone H3 was found associated with viral DNA at early times of infection. Interestingly, histone H3 was underrepresented on IE promoters in a manner dependent on the VP16 activation domain. Thus, the VP16 activation domain is responsible for recruiting general transcription factors and coactivators to IE promoters and also for dramatically reducing the association of histones with those promoters.
Heat Shock Protein 70 Protects Cells from Cell Cycle Arrest and Apoptosis Induced by Human Immunodeficiency Virus Type 1 Viral Protein R
Authors: Iordanskiy Sergey , Zhao Yuqi , Dubrovsky Larisa , Iordanskaya Tatiana , Chen Mongzhong , Liang Dong , Bukrinsky Michael 
Published: August 2004

ABSTRACTViral protein R (Vpr) of human immunodeficiency virus type 1 (HIV-1) is an accessory protein that plays an important role in viral pathogenesis. This pathogenic activity of Vpr is related in part to its capacity to induce cell cycle G2arrest and apoptosis of target T cells. A screening for multicopy suppressors of these Vpr activities in fission yeast identified heat shock protein 70 (Hsp70) as a suppressor of Vpr-induced cell cycle arrest. Hsp70 is a member of a family of molecular chaperones involved in innate immunity and protection from environmental stress. In this report, we demonstrate that HIV-1 infection induces Hsp70 in target cells. Overexpression of Hsp70 reduced the Vpr-dependent G2arrest and apoptosis and also reduced replication of the Vpr-positive, but not Vpr-deficient, HIV-1. Suppression of Hsp70 expression by RNA interference (RNAi) resulted in increased apoptosis of cells infected with a Vpr-positive, but not Vpr-defective, HIV-1. Replication of the Vpr-positive HIV-1 was also increased when Hsp70 expression was diminished. Vpr and Hsp70 coimmunoprecipitated from HIV-infected cells. Together, these results identify Hsp70 as a novel anti-HIV innate immunity factor that targets HIV-1 Vpr.
Regulation of Hepatitis C Virus Replication by Interferon Regulatory Factor 1
Authors: Kanazawa Nobuhiko , Kurosaki Masayuki , Sakamoto Naoya , Enomoto Nobuyuki , Itsui Yasuhiro , Yamashiro Tsuyoshi , Tanabe Yoko , Maekawa Shinya , Nakagawa Mina , Chen Cheng-Hsin , Kakinuma Sei , Oshima Shigeru , Nakamura Tetsuya , Kato Takanobu , Wakita Takaji , Watanabe Mamoru 
Published: August 2004

ABSTRACT
Cellular antiviral responses are mediated partly by the expression of interferon-stimulated genes, triggered by viral genomes, their transcripts and replicative intermediates. Persistent replication of a hepatitis C virus (HCV) replicon suggests that the replicon does not elicit cellular innate antiviral responses. In the present study, we investigated regulatory factors of the interferon-mediated antiviral system in cells expressing an HCV replicon. Luciferase reporter assays revealed that the baseline activity of the interferon-stimulated response element (ISRE) was significantly lower in cells harboring the replicon than in naive cells. Among the proteins involved in the IFN/Jak/STAT pathway and in ISRE activity, the expression level of interferon regulatory factor 1 (IRF-1) was found to be significantly lower in cells harboring the replicon. Transfection of an IRF-1 expression construct into cells harboring the replicon caused an increase of ISRE activity, accompanied by suppression of expression of the HCV replicon. Moreover, in cured Huh7 cells from which the HCV replicon had been eliminated, the expression levels of IRF-1 and ISRE activity also were suppressed, demonstrating that the decrease of IRF-1 is attributable, not to active suppression by the viral proteins, but to adaptation of cells that enables replication of the HCV subgenome. The high permissiveness of the cured cells for the replicon was abolished by transgenic supplementation of IRF-1 expression. Taken together, IRF-1 is one of the key host factors that regulate intracellular HCV replication through modulation of interferon-stimulated-gene-mediated antiviral responses.
Inhibition of Cyclooxygenase Activity Reduces Rotavirus Infection at a Postbinding Step
Authors: Rossen John W. A. , Bouma Janneke , Raatgeep Rolien H. C. , Büller Hans A. , Einerhand Alexandra W. C. 
Published: August 2004

ABSTRACTElevated levels of prostaglandins (PGs), products of cyclooxygenases (COXs), are found in the plasma and stool of rotavirus-infected children. We sought to determine the role of COXs, PGs, and the signal transduction pathways involved in rotavirus infection to elucidate possible new targets for antiviral therapy. Human intestinal Caco-2 cells were infected with human rotavirus Wa or simian rotavirus SA-11. COX-2 mRNA expression and secreted PGE2levels were determined at different time points postinfection, and the effect of COX inhibitors on rotavirus infection was studied by an immunofluorescence assay (IFA). To reveal the signal transduction pathways involved, the effect of MEK, protein kinase A (PKA), p38 mitogen-activated protein kinase (MAPK), and NF-κB inhibitors on rotavirus infection was analyzed. In infected Caco-2 cells, increased COX-2 mRNA expression and secreted PGE2levels were detected. Indomethacin (inhibiting both COX-1 and COX-2) and specific COX-1 and COX-2 inhibitors reduced rotavirus infection by 85 and 50%, respectively, as measured by an IFA. Indomethacin reduced virus infection at a postbinding step early in the infection cycle, inhibiting virus protein synthesis. Indomethacin did not seem to affect viral RNA synthesis. Inhibitors of MEK, PKA, p38 MAPK, and NF-κB decreased rotavirus infection by at least 40%. PGE2counteracted the effect of the COX and PKA inhibitors but not of the MEK, p38 MAPK, and NF-κB inhibitors. Conclusively, COXs and PGE2are important mediators of rotavirus infection at a postbinding step. The ERK1/2 pathway mediated by PKA is involved in COX induction by rotavirus infection. MAPK and NF-κB pathways are involved in rotavirus infection but in a PGE2-independent manner. This report offers new perspectives in the search for therapeutic agents in treatment of severe rotavirus-mediated diarrhea in children.
Integral Membrane Protein P16 of Bacteriophage PRD1 Stabilizes the Adsorption Vertex Structure
Authors: Jaatinen Silja T. , Viitanen Salla J. , Bamford Dennis H. , Bamford Jaana K. H. 
Published: August 2004

ABSTRACT
The icosahedral membrane-containing double-stranded DNA bacteriophage PRD1 has a labile receptor binding spike complex at the vertices. This complex, which is analogous to that of adenovirus, is formed of the penton protein P31, the spike protein P5, and the receptor binding protein P2. Upon infection, the internal phage membrane transforms into a tubular structure that protrudes through a vertex and penetrates the cell envelope for DNA injection. We describe here a new class of PRD1 mutants lacking virion-associated integral membrane protein P16. P16 links the spike complex to the viral membrane and is necessary for spike stability. We also show that the unique vertex used for DNA packaging is intact in the P16-deficient particle, indicating that the 11 adsorption vertices and the 1 portal vertex are functionally and structurally distinct.
NSs Protein of Rift Valley Fever Virus Blocks Interferon Production by Inhibiting Host Gene Transcription
Authors: Billecocq Agnès , Spiegel Martin , Vialat Pierre , Kohl Alain , Weber Friedemann , Bouloy Michèle , Haller Otto 
Published: August 2004

ABSTRACT
Rift Valley fever virus (RVFV) is an important cause of epizootics and epidemics in Africa and a potential agent of bioterrorism. A better understanding of the factors that govern RVFV virulence and pathogenicity is required, given the urgent need for antiviral therapies and safe vaccines. We have previously shown that RVFV strains with mutations in the NSs gene are excellent inducers of α/β interferon (IFN-α/β) and are highly attenuated in mice. Here, we demonstrate that NSs is sufficient to block IFN-β gene expression at the transcriptional level. In cells transiently expressing NSs, IFN-β transcripts were not inducible by viral infection or by transfection of poly(I:C). NSs with anti-IFN activity accumulated in the nucleus. In contrast, mutant forms of NSs that had lost their IFN-inhibiting activity remained in the cytoplasm, indicating that nuclear localization plays a role. IFN synthesis is regulated by specific transcription factors, including interferon regulatory factor (IRF-3), NF-κB, and AP-1. In the presence of NSs, IRF-3 was still activated and moved to the nucleus. Likewise, NF-κB and AP-1 were activated normally, as shown in electrophoretic mobility shift assays. Moreover, NSs was found to inhibit transcriptional activity of a constitutive promoter, in agreement with recent findings showing that NSs targets the basal cellular transcription factor TFIIH. The present results suggest that NSs, unlike other viral IFN antagonists, does not inhibit IFN-specific transcription factors but blocks IFN gene expression at a subsequent step.
Tagging Retrovirus Vectors with a Metal Binding Peptide and One-Step Purification by Immobilized Metal Affinity Chromatography
Authors: Ye Kaiming , Jin Sha , Ataai Mohammad M. , Schultz Jerome S. , Ibeh Jeanette 
Published: August 2004

ABSTRACTRetroviral vectors produced from packaging cells are invariably contaminated by protein, nucleic acid, and other substances introduced in the manufacturing process. Elimination of these contaminants from retroviral vector preparations is helpful to reduce unwanted side effects, and purified vector preparations are desirable to improve reproducibility of therapeutic effect. Here we report a novel approach to engineer a metal binding peptide (MBP)-tagged murine leukemia virus (MuLV), allowing for one-step purification of retroviral vectors by immobilized metal affinity chromatography (IMAC). We inserted a His6peptide into an ecotropic envelope protein (Env) by replacing part of its hypervariable region sequence with a sequence encoding the His6peptide. Display of the His6tag on the surface of Env endowed the vectors with a high affinity for immobilized metal ions, such as nickel. We demonstrated that the His6-tagged MuLV could be produced to high titers and could be highly purified by one-step IMAC. The protein and DNA contaminants in the purified vector supernatants were below 7 μg/ml and 25 pg/ml, respectively, indicating a 1,229-fold reduction in protein contaminant level and a 6,800-fold reduction in DNA contaminant level. About 56% of the viral vectors were recovered in the IMAC purification. The purified vectors retained their functionality and infectivity. These results establish that an MBP can be functionally displayed on the surface of ecotropic retroviruses without interfering with their integrity, and MBP-tagged retroviral vectors can be highly purified by one-step IMAC.
Genetic Analysis of Determinants for Spike Glycoprotein Assembly into Murine Coronavirus Virions: Distinct Roles for Charge-Rich and Cysteine-Rich Regions of the Endodomain
Authors: Ye Rong , Montalto-Morrison Cynthia , Masters Paul S. 
Published: August 2004

ABSTRACT
The coronavirus spike protein (S) forms the distinctive virion surface structures that are characteristic of this viral family, appearing in negatively stained electron microscopy as stems capped with spherical bulbs. These structures are essential for the initiation of infection through attachment of the virus to cellular receptors followed by fusion to host cell membranes. The S protein can also mediate the formation of syncytia in infected cells. The S protein is a type I transmembrane protein that is very large compared to other viral fusion proteins, and all except a short carboxy-terminal segment of the S molecule constitutes the ectodomain. For the prototype coronavirus mouse hepatitis virus (MHV), it has previously been established that S protein assembly into virions is specified by the carboxy-terminal segment, which comprises the transmembrane domain and the endodomain. We have genetically dissected these domains in the MHV S protein to localize the determinants of S incorporation into virions. Our results establish that assembly competence maps to the endodomain of S, which was shown to be sufficient to target a heterologous integral membrane protein for incorporation into MHV virions. In particular, mutational analysis indicated a major role for the charge-rich carboxy-terminal region of the endodomain. Additionally, we found that the adjacent cysteine-rich region of the endodomain is critical for fusion of infected cells, confirming results previously obtained with S protein expression systems.
Diverse Roles for E4orf3 at Late Times of Infection Revealed in an E1B 55-Kilodalton Protein Mutant Background
Authors: Shepard Robin N. , Ornelles David A. 
Published: August 2004

ABSTRACT
Species C human adenovirus mutants that fail to express open reading frame 3 of early region 4 (E4orf3) are phenotypically indistinguishable from the wild-type virus when evaluated in cells cultured in vitro. However, E4orf3 gene function has been productively studied in the context of additional viral mutations. This study identifies diverse roles for the E4orf3 protein that are evident in the absence of early region 1B 55-kDa protein (E1B-55K) function. In an E1B-55K-deficient background, the E4orf3 protein promotes viral replication by increasing both the burst size and the probability that an infected cell will produce virus. Early viral gene expression is not impaired in E1B-55K/E4orf3 double mutant virus-infected cells. Cells infected with the double mutant virus accumulated concatemers of viral DNA. However, the E1B-55K/E4orf3 double mutant virus did not replicate any better in MO59J cells, in which viral DNA concatemers did not accumulate, than in MO59K cells, in which viral DNA concatemers were produced, suggesting that viral DNA concatenation is not the primary growth defect of the E1B-55K/E4orf3 double mutant virus. Accumulation of viral mRNA in the nucleus and cytoplasm of E1B-55K/E4orf3 double mutant virus-infected cells was severely reduced compared to that on wild-type virus-infected cells. Thus, in an E1B-55K mutant background, the E4orf3 protein promotes the accumulation of late viral RNA and enhances late gene expression. Finally, within the context of an E1B-55K mutant virus, the E4orf3 protein acts to suppress host cell translation and preserve the viability of cells at moderately late times of infection.
The Vaccinia Virus G1L Putative Metalloproteinase Is Essential for Viral Replication In Vivo
Authors: Hedengren-Olcott Marika , Byrd Chelsea M. , Watson Jeffrey , Hruby Dennis E. 
Published: August 2004

ABSTRACT

The function of the putative metalloproteinase encoded by the vaccinia virus
G1L
gene is unknown. To address this question, we have generated a vaccinia virus strain in which expression of the
G1L
gene is dependent on the addition of tetracycline (TET) when infection proceeds in a cell line expressing the tetracycline repressor. The vv
tetOG1L
virus replicated similarly to wild-type Western Reserve (WR) virus in these cells when TET was present but was arrested at a late stage in viral maturation in the absence of TET. This arrest resulted in the accumulation of 98.5% round immature virus particles compared to 6.9% at a similar time point when TET was present. Likewise, the titer of infectious virus progeny decreased by 98.9% ± 0.97% when the vv
tetOG1L
virus was propagated in the absence of TET. Mutant virus replication was partially rescued by plasmid-encoded G1L, but not by G1L containing an HXXEH motif mutated to RXXQR. Modeling of G1L revealed a predicted structural similarity to the α-subunit of
Saccharomyces cerevisiae
mitochondrial processing peptidase (α-MPP). The HXXEH motif of G1L perfectly overlaps the HXXDR motif of α-MPP in this model. These results demonstrate that
G1L
is essential for virus maturation and suggest that G1L is a metalloproteinase with structural homology to α-MPP. However, no obvious effects on the expression and processing of the vaccinia virus major core proteins were observed in the
G1L
conditional mutant in the absence of TET compared to results for the TET and wild-type WR controls, suggesting that G1L activity is required after this step in viral morphogenesis.