bluuebunny/crossref_metadata_2025_split huggingface dataset:
CCAAT/Enhancer-Binding Protein-α Is Induced during the Early Stages of Kaposi's Sarcoma-Associated Herpesvirus (KSHV) Lytic Cycle Reactivation and Together with the KSHV Replication and Transcription Activator (RTA) Cooperatively Stimulates the Viral RTA, MTA, and PAN Promoters
Authors: Wang Shizhen Emily , Wu Frederick Y. , Yu Yanxing , Hayward Gary S. 
Published: August 2003

ABSTRACT

During the immediate-early (IE) phase of reactivation from latency, the Kaposi's sarcoma-associated herpesvirus (KSHV) replication and transcription activator protein (RTA) (or ORF50) is thought to be the most critical trigger that upregulates expression of many downstream viral lytic cycle genes, including the delayed-early (DE) gene encoding the replication-associated protein (RAP) (or K8). RAP physically interacts with and stabilizes the cellular transcription factor CCAAT/enhancer-binding protein-α (C/EBPα), leading to upregulated expression of the cellular C/EBPα and p21
CIP-1
proteins followed by G
0
/G
1
cell cycle arrest. Furthermore, RTA also interacts with C/EBPα, and both RAP and RTA cooperate with C/EBPα to activate the RAP promoter through binding to a strong proximal C/EBP binding site that also serves as an RTA-responsive element (RRE). Here we show that C/EBPα also activates the IE RTA promoter in transient-cotransfection reporter gene assays and that addition of either RTA or RAP enhances the effect. Electrophoretic mobility shift assay and deletion analysis revealed three C/EBP binding sites that mediate cooperative transactivation of the RTA promoter by C/EBPα and RTA. Furthermore, chromatin immunoprecipitation assay results showed that the endogenous C/EBPα, RTA, and RAP proteins all associate with RTA promoter sequences in tetradecanoyl phorbol acetate-induced primary effusion lymphoma (PEL) cells. Induction of endogenous KSHV RTA mRNA in PEL cells by exogenously introduced C/EBPα was confirmed by reverse transcription-PCR analysis and by double-label indirect immunofluorescence assays. Reciprocally, expression of exogenous RTA also led to an increase of endogenous C/EBPα expression that could be detected by Western immunoblot assays even in KSHV-negative DG75 cells. Cotransfected RTA also increased positive C/EBPα autoregulation of the C/EBPα promoter in transient-cotransfection reporter gene assays. Finally, C/EBPα proved to strongly activate the promoters of two other KSHV DE genes encoding PAN (polyadenylated nuclear) RNA and MTA (ORF57), which was again mediated by C/EBP binding sites that also contribute to RTA activation. Overall, these results support a model in which the cellular transcription factor C/EBPα and RTA:C/EBPα interactions play important roles both upstream and downstream of the two major KSHV regulatory proteins RTA and RAP during the early stages of lytic cycle reactivation.
Point Mutations in Exon I of the Herpes Simplex Virus Putative Terminase Subunit, UL15, Indicate that the Most Conserved Residues Are Essential for Cleavage and Packaging
Authors: Przech Angela J. , Yu Dong , Weller Sandra K. 
Published: August 2003

ABSTRACT
The herpes simplex virus UL15 and UL28 genes are believed to encode two subunits of the terminase involved in cleavage and packaging of viral genomes. Analysis of the UL15 protein sequence and its herpesvirus homologues revealed the presence of 20 conserved regions. Twelve of the twenty regions conserved among herpesviruses are also conserved in terminases from DNA bacteriophage. Point mutations in UL15 were designed in four conserved regions: L120N (CR1), Q205E (CR2), Q251E (CR3), G263A (CR3), and Y285S (CR4). Transfection experiments indicated that each mutant gene could produce stable UL15 protein at wild-type levels; however, only one mutant (Q251E) was able to complement the UL15-null virus. Each mutation was introduced into the viral genome by marker transfer, and all mutants except Q251E were unable to form plaques on Vero cells. Furthermore, failure to form plaques on Vero cells correlated with a defect in cleavage and packaging. Immunofluorescence experiments indicated that in cells infected with all mutant viruses the UL15 protein could be detected and was found to localize to replication compartments. Although wild-type and mutant Q251E were able to produce A, B, and C capsids, the rest of the mutants were only able to produce B capsids, a finding consistent with their defects in cleavage and packaging. In addition, all mutant UL15 proteins retained their ability to interact with B capsids. Therefore, amino acid residues 120, 205, 263, and 285 are essential for the cleavage and packaging process rather than for association with capsids or localization to replication compartments.
Antiviral Activity of Limitin against Encephalomyocarditis Virus, Herpes Simplex Virus, and Mouse Hepatitis Virus: Diverse Requirements by Limitin and Alpha Interferon for Interferon Regulatory Factor 1
Authors: Kawamoto Shin-Ichiro , Oritani Kenji , Asada Hideo , Takahashi Isao , Ishikawa Jun , Yoshida Hitoshi , Yamada Masahide , Ishida Naoko , Ujiie Hidetoshi , Masaie Hiroaki , Tomiyama Yoshiaki , Matsuzawa Yuji 
Published: August 2003

ABSTRACTLimitin has sequence homology with alpha interferon (IFN-α) and IFN-β and utilizes the IFN-α/β receptor. However, it has no influence on the proliferation of normal myeloid and erythroid progenitors. In this study, we show that limitin has antiviral activity in vitro as well as in vivo. Limitin inhibited not only cytopathic effects in encephalomyocarditis virus- or herpes simplex virus (HSV) type 1-infected L929 cells, but also plaque formation in mouse hepatitis virus (MHV) type 2-infected DBT cells. In addition, administration of limitin to mice suppressed MHV-induced hepatitis and HSV-induced death. The antiviral activity may be mediated in part by 2′,5′-oligoadenylate synthetase, RNA-dependent protein kinase, and Mx protein, which inhibit viral replication or degrade viral components, because limitin induced their mRNA expression and enzyme activity. While limitin has antiviral activity as strong as that of IFN-α in vitro (the concentration that provided 50% inhibition of cytopathic effect is ∼30 pg/ml), IFN regulatory factor 1 (IRF-1) dependencies for induction of an antiviral state were different for limitin and IFN-α. In IRF-1-deficient fibroblasts, a higher concentration of limitin than of IFN-α was required for the induction of antiviral activity and the transcription of proteins from IFN-stimulated response element. The unique signals and the fewer properties of myelosuppression suggest that a human homolog of limitin may be used as a new antiviral drug.
Maedi-Visna Virus and Caprine Arthritis Encephalitis Virus Genomes Encode a Vpr-Like but No Tat Protein
Authors: Villet Stéphanie , Bouzar Baya Amel , Morin Thierry , Verdier Gérard , Legras Catherine , Chebloune Yahia 
Published: August 2003

ABSTRACT

A small open reading frame (ORF) in maedi-visna virus (MVV) and caprine arthritis encephalitis virus (CAEV) was initially named “
tat
” by analogy with a similarly placed ORF in the primate lentiviruses. The encoded “Tat” protein was ascribed the function of up regulation of the viral transcription from the long terminal repeat (LTR) promoter, but we have recently reported that MVV and CAEV Tat proteins lack
trans
-activation function activity under physiological conditions (S. Villet, C. Faure, B. Bouzar, G. Verdien, Y. Chebloune, and C. Legras, Virology 307:317-327, 2003). In the present work, we show that MVV Tat localizes to the nucleus of transfected cells, probably through the action of a nuclear localization signal in its C-terminal portion. We also show that, unlike the human immunodeficiency virus (HIV) Tat protein, MVV Tat was not secreted into the medium by transfected human or caprine cells in the absence of cell lysis but that, like the primate accessory protein Vpr, MVV and CAEV Tat proteins were incorporated into viral particles. In addition, analysis of the primary protein structures showed that small-ruminant lentivirus (SRLV) Tat proteins are more similar to the HIV type 1 (HIV-1) Vpr protein than to HIV-1 Tat. We also demonstrate a functional similarity between the SRLV Tat proteins and the HIV-1 Vpr product in the induction of a specific G
2
arrest of the cell cycle in MVV Tat-transfected cells, which increases the G
2
/G
1
ratio 2.8-fold. Together, these data strongly suggest that the
tat
ORF in the SRLV genomes does not code for a regulatory transactivator of the LTR but, rather, for a Vpr-like accessory protein.
Existence of Transdominant and Potentiating Mutants of UL9, the Herpes Simplex Virus Type 1 Origin-Binding Protein, Suggests that Levels of UL9 Protein May Be Regulated during Infection
Authors: Marintcheva Boriana , Weller Sandra K. 
Published: August 2003

ABSTRACT
UL9 is a multifunctional protein required for herpes simplex virus type 1 (HSV-1) replication in vivo. UL9 is a member of the superfamily II helicases and exhibits helicase and origin-binding activities. We have previously shown that mutations in the conserved helicase motifs of UL9 can have either a transdominant or potentiating effect on the plaque-forming ability of infectious DNA from wild-type virus (A. J. Malik and S. K. Weller, J. Virol. 70:7859-7866, 1996). In this paper, the mechanisms of transdominance and potentiation are explored. We show that the motif V mutant protein containing a G to A substitution at residue 354 is unstable when expressed by transfection and is either processed to a 38-kDa N-terminal fragment or degraded completely. The overexpression of the MV mutant protein is able to influence the steady-state protein levels of wild-type UL9 and to override the inhibitory effects of wild-type UL9. Potentiation correlates with the ability of the UL9 variants containing the G354A mutation to be processed or degraded to the 38-kDa form. We propose that the MV mutant protein is able to interact with full-length UL9 and that this interaction results in a decrease in the steady-state levels of UL9, which in turn leads to enhanced viral infection. Furthermore, we demonstrate that inhibition of HSV-1 infection can be obtained by overexpression of full-length UL9, the C-terminal third of the protein containing the origin-binding domain, or the N-terminal two-thirds of UL9 containing the conserved helicase motifs and the putative dimerization domain. Our results suggest that transdominance can be mediated by overexpression, origin-binding activity, and dimerization, whereas potentiation is most likely caused by the ability of the UL9 MV mutant to influence the steady-state levels of wild-type UL9. Taken together, the results presented in this paper suggest that the regulation of steady-state levels of UL9 may play an important role in controlling viral infection.
Cell Cycle Regulation by Kaposi's Sarcoma-Associated Herpesvirus K-bZIP: Direct Interaction with Cyclin-CDK2 and Induction of G
1
Growth Arrest
Authors: Izumiya Yoshihiro , Lin Su-Fang , Ellison Thomas J. , Levy Alon M. , Mayeur Greg L. , Izumiya Chie , Kung Hsing-Jien 
Published: August 2003

ABSTRACT

In order to cope with hostile host environments, many viruses have developed strategies to perturb the cellular machinery to suit their replication needs. Some herpesvirus genes protect cells from undergoing apoptosis to prolong the lives of infected cells, while others, such as Epstein-Barr virus Zta, slow down the G
1
/S transition phase to allow ample opportunity for transcription and translation of viral genes before the onset of cellular genomic replication. In this study, we investigated whether Kaposi's sarcoma-associated herpesvirus (KSHV) K-bZIP, a homologue of the Epstein-Barr virus transcription factor BZLF1 (Zta), plays a role in cell cycle regulation. Here we show that K-bZIP physically associates with cyclin-CDK2 and downmodulates its kinase activity. The association can be detected in the natural environment of KSHV-infected cells without artificial overexpression of either component. With purified protein, it can be shown that the interaction between K-bZIP and cyclin-CDK2 is direct and that K-bZIP alone is sufficient to inhibit CDK2 activity. The interacting domain of K-bZIP has been mapped to the basic region. The result of these associations is a prolonged G
1
phase, accompanied by the induction of p21 and p27 in a naturally infected B-cell line. Thus, in addition to the previously described transcription and genome replication functions, a new role of K-bZIP in KSHV replication is identified in this report.
Chromosomal Distribution of Endogenous Jaagsiekte Sheep Retrovirus Proviral Sequences in the Sheep Genome
Authors: Carlson Jonathan , Lyon Monique , Bishop Jeanette , Vaiman Anne , Cribiu Edmond , Mornex Jean-François , Brown Susan , Knudson Dennis , DeMartini James , Leroux Caroline 
Published: August 2003

ABSTRACT

A family of endogenous retroviruses (enJSRV) closely related to Jaagsiekte sheep retrovirus (JSRV) is ubiquitous in domestic and wild sheep and goats. Southern blot hybridization studies indicate that there is little active replication or movement of the enJSRV proviruses in these species. Two approaches were used to investigate the distribution of proviral loci in the sheep genome. Fluorescence in situ hybridization (FISH) to metaphase chromosome spreads using viral DNA probes was used to detect loci on chromosomes. Hybridization signals were reproducibly detected on seven sheep chromosomes and eight goat chromosomes in seven cell lines. In addition, a panel of 30 sheep-hamster hybrid cell lines, each of which carries one or more sheep chromosomes and which collectively contain the whole sheep genome, was examined for enJSRV sequences. DNA from each of the lines was used as a template for PCR with JSRV
gag
-specific primers. A PCR product was amplified from 27 of the hybrid lines, indicating that JSRV
gag
sequences are found on at least 15 of the 28 sheep chromosomes, including those identified by FISH. Thus, enJSRV proviruses are essentially randomly distributed among the chromosomes of sheep and goats. FISH and/or Southern blot hybridization on DNA from several of the sheep-hamster hybrid cell lines suggests that loci containing multiple copies of enJSRV are present on chromosomes 6 and 9. The origin and functional significance of these arrays is not known.
Surface Downregulation of Major Histocompatibility Complex Class I, PE-CAM, and ICAM-1 following De Novo Infection of Endothelial Cells with Kaposi's Sarcoma-Associated Herpesvirus
Authors: Tomescu Costin , Law Wai K. , Kedes Dean H. 
Published: August 2003

ABSTRACTUnder selective pressure from host cytotoxic T lymphocytes, many viruses have evolved to downregulate major histocompatibility complex (MHC) class I and/or T-cell costimulatory molecules from the surface of infected cells. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes two proteins, MIR-1 and MIR-2, that serve this function during lytic replication. In vivo, however, KSHV exists in a predominantly latent state, with less than 5% of infected cells expressing discernible lytic gene products. Thus, mechanisms of immune evasion that depend on genes expressed only during lytic replication are unlikely to be active in most KSHV-infected cells. As a result, we searched for evidence of similar defensive strategies extant during latency, employing culture systems that strongly favor latent KSHV infection. We measured cell surface levels of immunomodulatory proteins on both primary dermal microvascular endothelial cells (pDMVEC) infected through coculture with induced primary effusion lymphoma cells and telomerase-immortalized DMVEC infected directly with cell-free virus. Employing a panel of antibodies against several endothelial cell surface proteins, we show that de novo infection with KSHV leads to the downregulation of MHC class I, CD31 (PE-CAM), and CD54 (ICAM-I) but not CD58 (LFA-3) or CD95 (Fas). Furthermore, flow cytometry with a fluorescently labeled monoclonal antibody to the latency-associated nuclear antigen (LANA) revealed that downregulation occurred predominantly on KSHV-infected (LANA-positive) cells. Although the vast majority of infected cells displayed this downregulation, less than 1% expressed either immediate-early or late lytic proteins detectable by immunofluorescence. Together, these results suggest that downregulation of immunomodulatory proteins on the surface of target cells may represent a constitutive mode of immune evasion employed by KSHV following de novo infection.
A Bromodomain-Containing Protein from Tomato Specifically Binds Potato Spindle Tuber Viroid RNA In Vitro and In Vivo
Authors: Martínez de Alba Angel Emilio , Sägesser Rudolf , Tabler Martin , Tsagris Mina 
Published: August 2003

ABSTRACT
For the identification of RNA-binding proteins that specifically interact with potato spindle tuber viroid (PSTVd), we subjected a tomato cDNA expression library prepared from viroid-infected leaves to an RNA ligand screening procedure. We repeatedly identified cDNA clones that expressed a protein of 602 amino acids. The protein contains a bromodomain and was termed viroid RNA-binding protein 1 (VIRP1). The specificity of interaction of VIRP1 with viroid RNA was studied by different methodologies, which included Northwestern blotting, plaque lift, and electrophoretic mobility shift assays. VIRP1 interacted strongly and specifically with monomeric and oligomeric PSTVd positive-strand RNA transcripts. Other RNAs, for example, U1 RNA, did not bind to VIRP1. Further, we could immunoprecipitate complexes from infected tomato leaves that contained VIRP1 and viroid RNA in vivo. Analysis of the protein sequence revealed that VIRP1 is a member of a newly identified family of transcriptional regulators associated with chromatin remodeling. VIRP1 is the first member of this family of proteins, for which a specific RNA-binding activity is shown. A possible role of VIRP1 in viroid replication and in RNA mediated chromatin remodeling is discussed.
Differences in the N Termini of Herpes Simplex Virus Type 1 and 2 gDs That Influence Functional Interactions with the Human Entry Receptor Nectin-2 and an Entry Receptor Expressed in Chinese Hamster Ovary Cells
Authors: Zago Anna , Spear Patricia G. 
Published: August 2003

ABSTRACT
Amino acid differences at seven positions in the N termini of the glycoproteins D (gDs) specified by herpes simplex virus type 1 (HSV-1) and HSV-2 are largely responsible for the significantly higher cell fusion activity of HSV-2 gD with Chinese hamster ovary cells expressing human nectin-2 or only an endogenous hamster receptor.
Protective Efficacy of an AIDS Vaccine, a Single DNA Priming Followed by a Single Booster with a Recombinant Replication-Defective Sendai Virus Vector, in a Macaque AIDS Model
Authors: Takeda Akiko , Igarashi Hiroko , Nakamura Hiromi , Kano Munehide , Iida Akihiro , Hirata Takahiro , Hasegawa Mamoru , Nagai Yoshiyuki , Matano Tetsuro 
Published: August 2003

ABSTRACT
We previously demonstrated the excellent protective efficacy of DNA priming followed by Gag-expressing Sendai virus (SeV) boosting (DNA prime/SeV-Gag boost vaccine) against a pathogenic simian-human immunodeficiency virus (SHIV89.6PD) infection in macaques. Here we show that we established a practical, safer AIDS vaccine protocol, a single DNA priming followed by a single booster with a recently developed replication-defective F deletion SeV-expressing Gag, and show its protective efficacy against SHIV89.6PD infections.
High Circulating Frequencies of Tumor Necrosis Factor Alpha- and Interleukin-2-Secreting Human T-Lymphotropic Virus Type 1 (HTLV-1)-Specific CD4+T Cells in Patients with HTLV-1-Associated Neurological Disease
Authors: Goon Peter K. C. , Igakura Tadahiko , Hanon Emmanuel , Mosley Angelina J. , Asquith Becca , Gould Keith G. , Taylor Graham P. , Weber Jonathan N. , Bangham Charles R. M. 
Published: August 2003

ABSTRACTSignificantly higher frequencies of tumor necrosis factor alpha- and interleukin-2-secreting human T-lymphotropic virus type 1 (HTLV-1)-specific CD4+T cells were present in the peripheral blood mononuclear cells of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients than in those of asymptomatic carriers with similar provirus loads. The data suggest that HTLV-1-specific CD4+T cells play a role in the pathogenesis of HAM/TSP.
Early- and Intermediate-Stage Variants of Simian Immunodeficiency Virus Replicate Efficiently in Cells Lacking CCR5
Authors: Forte Serene , Harmon Mary-Elizabeth , Pineda Mario J. , Overbaugh Julie 
Published: August 2003

ABSTRACT
Primate lentiviruses are thought to use the chemokine receptor CCR5 as the major coreceptor for entry into cells. Here we show that some variants of simian immunodeficiency virus (SIV) replicate efficiently in peripheral blood mononuclear cells (PBMCs) lacking a functional CCR5. There were differences in the replication patterns of sequential variants that evolved during SIVMne infection; the late-stage pathogenic variants were unable to replicate in PBMCs lacking CCR5, whereas the early- and intermediate-stage viruses replicated as well in PBMCs lacking CCR5 as they did in cells with wild-type CCR5. The coreceptor specificities of these sequential variants were compared using indicator cell lines expressing known SIV coreceptors. Among the known SIV coreceptors, there were none that were functional for the early and intermediate variants but not the late-stage variants, suggesting that the coreceptor used for replication in PBMCs may be a coreceptor that has not yet been described. Because some variants replicate with high efficiency in peripheral blood cells using this as yet uncharacterized cellular receptor, this coreceptor may be important for viral entry of some target cell populations in the host.
Susceptibility of Human Hepatitis Delta Virus RNAs to Small Interfering RNA Action
Authors: Chang Jinhong , Taylor John M. 
Published: August 2003

ABSTRACT
In animal cells, small interfering RNAs (siRNA), when exogenously provided, have been reported to be capable of inhibiting replication of several different viruses. In preliminary studies, siRNA species were designed and tested for their ability to act on the protein expressed in Huh7 cells transfected with DNA-directed mRNA constructs containing hepatitis delta virus (HDV) target sequences. The aim was to achieve siRNA specific for each of the three RNAs of HDV replication: (i) the 1,679-nucleotide circular RNA genome, (ii) its exact complement, the antigenome, and (iii) the less abundant polyadenylated mRNA for the small delta protein. Many of the 16 siRNA tested gave >80% inhibition in this assay. Next, these three classes of siRNA were tested for their ability to act during HDV genome replication. It was found that only siRNA targeted against HDV mRNA sequences could interfere with HDV genome replication. In contrast, siRNA targeted against genomic and antigenomic RNA sequences had no detectable effect on the accumulation of these RNAs. Reconstruction experiments with nonreplicating HDV RNA sequences support the interpretation that neither the potential for intramolecular rod-like RNA folding nor the presence of the delta protein conferred resistance to siRNA. In terms of replicating HDV RNAs, it is considered more likely that the genomic and antigenomic RNAs are resistant because their location within the nucleus makes them inaccessible to siRNA-mediated degradation.