bluuebunny/crossref_metadata_2025_split huggingface dataset:
Woodchuck Hepatitis Virus Enhancer I and Enhancer II Are Both Involved in N-
myc2
Activation in Woodchuck Liver Tumors
Authors: Flajolet Marc , Tiollais Pierre , Buendia Marie-Annick , Fourel Geneviève 
Published: December 2019

ABSTRACT

Direct activation of the N-
myc2
oncogene by insertion of woodchuck hepatitis virus (WHV) DNA is a major oncogenic step in woodchuck hepatocarcinogenesis. We previously reported that WHV enhancer II (We2), which controls expression of the core/pregenome RNA, can also activate the N-
myc2
promoter in hepatoma cell lines. To better define the integrated WHV regulatory sequences responsible for N-
myc2
promoter activation in woodchuck liver tumors, we analyzed the structure and enhancer activity of a single viral integrant found at the
win
locus in tumor 2260T1 and mapping approximately 175 kb 3′ of N-
myc2
. This viral insert was made of 11 concatemerized WHV fragments, 5 of which overlapped with We2 sequences and 1 with WHV sequence homologous to that of hepatitis B virus enhancer I (We1). In transient transfection assays in hepatoma-derived cells, the We2 activator was found to be fully effective only when inserted in close proximity to the N-
myc2
promoter whereas the We1 element by itself was apparently devoid of activity. In contrast, the 2260T1 viral insert exhibited a potent enhancer capacity that depended both on multimerized We2 and on We1 sequences. In a survey of different woodchuck hepatomas, both elements were commonly found within integrated viral sequences involved in long-range N-
myc2
activation.
The NS5A/NS5 Proteins of Viruses from Three Genera of the Family
Flaviviridae
Are Phosphorylated by Associated Serine/Threonine Kinases
Authors: Reed Karen E. , Gorbalenya Alexander E. , Rice Charles M. 
Published: December 2019

ABSTRACT

Phosphorylation of the expressed NS5A protein of hepatitis C virus (HCV), a member of the
Hepacivirus
genus of the family
Flaviviridae
, has been demonstrated in mammalian cells and in a cell-free assay by an associated kinase activity. In this report, phosphorylation is also shown for the NS5A and NS5 proteins, respectively, of bovine viral diarrhea virus (BVDV) and yellow fever virus (YF), members of the other two established genera in this family. Phosphorylation of BVDV NS5A and YF NS5 was observed in infected cells, transient expression experiments, and a cell-free assay similar to the one developed for HCV NS5A. Phosphoamino acid analyses indicated that all three proteins were phosphorylated by serine/threonine kinases. Similarities in the properties of BVDV NS5A, YF NS5, and HCV NS5A phosphorylation in vitro further suggested that closely related kinases or the same kinase may phosphorylate these viral proteins. Conservation of this trait among three quite distantly related viruses representing three separate genera suggests that phosphorylation of the NS5A/NS5 proteins or their association with cellular kinases may play an important role in the flavivirus life cycle.
Effects of Substituting Granulin or a Granulin-Polyhedrin Chimera for Polyhedrin on Virion Occlusion and Polyhedral Morphology in
Autographa californica
Multinucleocapsid Nuclear Polyhedrosis Virus
Authors: Eason Jane E. , Hice Robert H. , Johnson Jeffrey J. , Federici Brian A. 
Published: December 2019

ABSTRACT

Substitution of granulin from the
Trichoplusia ni
granulosis virus (TnGV) for polyhedrin of the
Autographa californica
multinucleocapsid nuclear polyhedrosis virus (Ac
M
NPV) yielded a few very large (2 to 5 μm) cuboidal inclusions in the cytoplasm and nucleus of infected cells. These polyhedra lacked the beveled edges characteristic of wild-type Ac
M
NPV polyhedra, contained fractures, and occluded few virions. Placing a nuclear localization signal (KRKK) in granulin directed more granulin to the nucleus and resulted in more structurally uniform cuboidal inclusions in which no virions were observed. A granulin-polyhedrin chimera produced tetrahedral occlusions with more virions than granulin inclusions but many fewer than wild-type polyhedra. Despite the unusual structure of the granulin and granulin-polyhedrin inclusions, they interacted with Ac
M
NPV p10 fibrillar structures and electron-dense spacers that are precursors of the polyhedral calyx. The change in inclusion shape obtained with the granulin-polyhedrin chimera demonstrates that the primary amino acid sequence affects occlusion body shape, but the large cuboidal inclusions formed by granulin indicate that the amino acid sequence is not the only determinant. The failure of granulin or the granulin-polyhedrin chimera to properly occlude Ac
M
NPV virions suggests that specific interactions occur between polyhedrin and other viral proteins which facilitate normal virion occlusion and occlusion body assembly and shape in baculoviruses.
The Herpesvirus Transactivator VP16 Mimics a Human Basic Domain Leucine Zipper Protein, Luman, in Its Interaction with HCF
Authors: Lu Rui , Yang Ping , Padmakumar Sharmila , Misra Vikram 
Published: December 2019

ABSTRACT

In human cells infected with herpes simplex virus (HSV), viral gene expression is initiated by the virion protein VP16. VP16 does not bind DNA directly but forms a multiprotein complex on the viral immediate-early gene promoters with two cellular proteins: the POU domain protein Oct-1 and host cell factor (HCF; also called C1, VCAF, and CFF). Despite its apparent role in stabilizing the VP16-induced transcription complex, the natural biological role of HCF is unclear. Only recently HCF has been implicated in control of the cell cycle. To determine the role of HCF in cells and answer why HSV has evolved an HCF-dependent mechanism for the initiation of the lytic cycle, we identified the first human ligand for HCF (R. Lu et al., Mol. Cell. Biol. 17:5117–5126, 1997). This protein, Luman, is a member of the CREB/ATF family of transcription factors that can activate transcription from promoters containing cyclic AMP response elements (CRE). Here we provide evidence that Luman and VP16 share two important structural features: an acidic activation domain and a common mechanism for binding HCF. We found that Luman, its homolog in
Drosophila
, dCREB-A (also known as BBF-2), and VP16 bind to HCF by a motif, (D/E)HXY(S/A), present in all three proteins. In addition, a mutation (P134S) in HCF that prevents VP16 binding also abolishes its binding to Luman and dCREB-A. We also show that while interaction with HCF is not required for the ability of Luman to activate transcription when tethered to the GAL4 promoter, it appears to be essential for Luman to activate transcription through CRE sites. These data suggest that the HCF-Luman interaction may represent a conserved mechanism for transcriptional regulation in metazoans, and HSV mimics this interaction with HCF to monitor the physiological state of the host cell.
Cellular Components Interact with Adenovirus Type 5 Minimal DNA Packaging Domains
Authors: Schmid Susanne I. , Hearing Patrick 
Published: December 2019

ABSTRACT

Adenovirus type 5 DNA packaging is initiated from the left end of the viral genome and depends on the presence of a
cis
-acting packaging domain located between nucleotides 194 and 380. Multiple redundant packaging elements (termed A repeats I through VII [AI through AVII]) are contained within this domain and display differential abilities to support DNA packaging in vivo. The functionally most important repeats, AI, AII, AV, and AVI, follow a bipartite consensus motif exhibiting AT-rich and CG-rich core sequences. Results from previous mutational analyses defined a fragment containing AV, AVI, and AVII as a minimal packaging domain in vivo, which supports a functional independence of the respective
cis
-acting sequences. Here we describe multimeric versions of individual packaging elements as minimal packaging domains that can confer viability and packaging activity to viruses carrying gross truncations within their left end. These mutant viruses directly rate the functional role that different packaging elements play relative to each other. The A repeats are likely to be binding sites for limiting,
trans
-acting packaging factors of cellular and/or viral origin. We report here the characterization of two cellular binding activities interacting with all of the minimal packaging domains in vitro, an unknown binding activity termed P-complex, and the transcription factor chicken ovalbumin upstream promoter transcription factor. The binding of both activities is dependent on the integrity of the AT-rich, but not the CG-rich, consensus half site. In the case of P-complex, binding affinity for different minimal packaging domains in vitro correlates well with their abilities to support DNA packaging in vivo. Interestingly, P-complex interacts not only with packaging elements but also with the left terminus of the viral genome, the core origin of replication. Our data implicate cellular factors as components of the viral packaging machinery. The dual binding specificity of P-complex for packaging and replication sequences may further suggest a direct involvement of left-end replication sequences in viral DNA encapsidation.
Binding of Human Immunodeficiency Virus Type 1 to CD4 and CXCR4 Receptors Differentially Regulates Expression of Inflammatory Genes and Activates the MEK/ERK Signaling Pathway
Authors: Popik Waldemar , Hesselgesser Joseph E. , Pitha Paula M. 
Published: December 2019

ABSTRACTWe have previously shown that binding of human immunodeficiency virus type 1 (HIV-1) virions to CD4 receptors stimulates association of Lck with Raf-1 and results in the activation of Raf-1 kinase in a Ras-independent manner. In the present study, we demonstrate that HIV-1 envelope glycoproteins of both T-cell-tropic and macrophagetropic strains rapidly activate the ERK/mitogen-activated protein (MAP) kinase pathway and the binding of nuclear transcription factors (AP-1, NF-κB, and C/EBP) and stimulate expression of cytokine and chemokine genes. The activation of this signaling pathway requires functional CD4 receptors and is independent of binding to CXCR4. Binding of the natural ligand stromal cell-derived factor 1 (SDF-1) to CXCR4, which inhibits entry of T-cell-tropic HIV-1, activates also the ERK/MAP kinase pathway. However, SDF-1 did not affect the CD4-mediated expression of cytokine and chemokine genes. These results provide firm molecular evidence that binding of HIV-1 envelope glycoproteins to CD4 receptor initiates a signaling pathway(s) independent of the binding to the chemokine receptor that leads to the aberrant expression of inflammatory genes and may contribute significantly to HIV-1 replication as well as to deregulation of the immune system.
Naturally Occurring Human Immunodeficiency Virus Type 1 Long Terminal Repeats Have a Frequently Observed Duplication That Binds RBF-2 and Represses Transcription
Authors: Estable Mario Clemente , Bell Brendan , Hirst Martin , Sadowski Ivan 
Published: December 2019

ABSTRACT

Approximately 38% of human immunodeficiency virus type 1 (HIV-1)-infected patients within the Vancouver Lymphadenopathy-AIDS Study have proviruses bearing partial 15- to 34-nucleotide duplications upstream of the NF-κB binding sites within the 5′ long terminal repeat (LTR). This most frequent naturally occurring length polymorphism (MFNLP) of the HIV-1 5′ LTR encompasses potential binding sites for several candidate transcription factors, including TCF-1α/hLEF, c-Ets, AP-4, and Ras-responsive binding factor 2 (RBF-2) (M. C. Estable et al., J. Virol. 70:4053–4062, 1996). RBF-2 and an apparently related factor, RBF-1, bind to at least four
cis
elements within the LTR which are required for full transcriptional responsiveness to protein-tyrosine kinases and v-Ras (B. Bell and I. Sadowski, Oncogene 13:2687–2697, 1996). Here we demonstrate that representative MFNLPs from two patients specifically bind RBF-2. In both cases, deletion of the MFNLP caused elevated LTR-directed transcription in cells expressing RBF-2 but not in cells with undetectable RBF-2. RBF-1, but not RBF-2, appears to contain the Ets transcription factor family member GABPα/GABPβ1. Taken together with the fact that every MFNLP from a comparative study of over 500 LTR sequences from 42 patients contains a predicted binding site for RBF-2, our data suggest that the MFNLP is selected in vivo because it provides a duplicated RBF-2
cis
element, which may limit transcription in monocytes and activated T cells.
Involvement of Aminopeptidase N (CD13) in Infection of Human Neural Cells by Human Coronavirus 229E
Authors: Lachance Claude , Arbour Nathalie , Cashman Neil R. , Talbot Pierre J. 
Published: December 2019

ABSTRACT
Attachment to a cell surface receptor can be a major determinant of virus tropism. Previous studies have shown that human respiratory coronavirus HCV-229E uses human aminopeptidase N (hAPN [CD13]) as its cellular receptor for infection of lung fibroblasts. Although human coronaviruses are recognized respiratory pathogens, occasional reports have suggested their possible neurotropism. We have previously shown that human neural cells, including glial cells in primary cultures, are susceptible to human coronavirus infection in vitro (A. Bonavia, N. Arbour, V. W. Yong, and P. J. Talbot, J. Virol. 71:800–806, 1997). However, the only reported expression of hAPN in the nervous system is at the level of nerve synapses. Therefore, we asked whether hAPN is utilized as a cellular receptor for infection of these human neural cell lines. Using flow cytometry, we were able to show the expression of hAPN on the surfaces of various human neuronal and glial cell lines that are susceptible to HCV-229E infection. An hAPN-specific monoclonal antibody (WM15), but not control antibody, inhibited the attachment of radiolabeled HCV-229E to astrocytic, neuronal, and oligodendrocytic cell lines. A correlation between the apparent amount of cell surface hAPN and the level of virus attachment was observed. Furthermore, the presence of WM15 inhibited virus infection of these cell lines, as detected by indirect immunofluorescence. These results indicate that hAPN (CD13) is expressed on neuronal and glial cell lines in vitro and serves as the receptor for infection by HCV-229E. This further strengthens the neurotropic potential of this human respiratory virus.
Changing the Site of Initiation of Plus-Strand DNA Synthesis Inhibits the Subsequent Template Switch during Replication of a Hepadnavirus
Authors: Loeb Daniel D. , Tian Ru , Gulya Karolyn J. , Qualey Amy E. 
Published: December 2019

ABSTRACT
Unique to hepadnavirus reverse transcription is the process of primer translocation, in which the RNA primer for the initiation of plus-strand DNA synthesis is generated at one site on its template, DR1, and is moved to a new site, DR2. For duck hepatitis B virus (DHBV), DR2 is located within 50 nucleotides of the 5′ end of the minus-strand DNA template. When the synthesis of plus-strand DNA proceeds to the 5′ terminus of the minus strand, the 3′ end of the minus strand becomes the template for DNA synthesis. This switch in templates circularizes the nascent genome and is required for the genesis of the relaxed circular form of the DNA and the mature capsid. Maturation of the capsid is a prerequisite for virus egress. We have analyzed a series of DHBV variants in which plus-strand DNA synthesis was initiated from a new position relative to the 5′ end of the template. For these variants, the subsequent circularization was inhibited. We found that when the number of nucleotides between the site of initiation of plus-strand DNA synthesis and the 5′ end of its template was restored to 54 nucleotides, circularization was substantially restored. These results mean that the process of circularization is influenced by the earlier steps in DNA replication. This sensitivity is consistent with the notion that this region of the nascent genome is in a dynamic structure that is crucial for successful DNA replication.
Involvement of Human CRM1 (Exportin 1) in the Export and Multimerization of the Rex Protein of Human T-Cell Leukemia Virus Type 1
Authors: Hakata Yoshiyuki , Umemoto Tomoe , Matsushita Shuzo , Shida Hisatoshi 
Published: December 2019

ABSTRACT
We investigated the role of human CRM1 (hCRM1) (exportin 1) in the function of Rex protein encoded by human T-cell leukemia virus type 1. hCRM1 promoted the export of Rex protein from the nucleus to the cytoplasm. A Rex protein with a mutation in the activation domain, RexM90, lost both the ability to bind to hCRM1 and the ability to multimerize. The overexpression of hCRM1 complemented the functional defects of RexM64, which contains a mutation in the multimerization domain of Rex. A dominant-negative mutant of Rex which sequesters cofactors of Rex abrogated multimerization as well as the activity of the wild-type Rex protein. These two functions were simultaneously restored by the overexpression of hCRM1. Taken together, these results suggest that hCRM1 plays important roles in the multimerization and export of Rex protein.
Protective Role of Gamma Interferon during the Recall Response to Influenza Virus
Authors: Bot Adrian , Bot Simona , Bona Constantin A. 
Published: December 2019

ABSTRACTDuring secondary immune responses to influenza virus, virus-specific T memory cells are a major source of gamma interferon (IFN-γ). We assessed the contribution of IFN-γ to heterologous protection against the A/WSN/33 (H1N1) virus of wild-type and IFN-γ−/− mice previously immunized with the A/HK/68 (H3N2) virus. The IFN-γ−/− mice displayed significantly reduced survival rates subsequent to a challenge with various doses of the A/WSN/33 virus. This was associated with an impaired ability of the IFN-γ−/− mice to completely clear the pulmonary virus by day 7 after the challenge, although significant reduction of the virus titers was noted. However, the IFN-γ−/− mice developed type A influenza virus cross-reactive cytotoxic T lymphocytes (CTLs) similar to the wild-type mice, as demonstrated by both cytotoxicity and a limiting-dilution assay for the estimation of CTL precursor frequency. The pulmonary recruitment of T cells in IFN-γ−/− mice was not dramatically affected, and the percentage of CD4+and CD8+T cells was similar to that of wild-type mice. The T cells from IFN-γ−/− mice did not display a significant switch toward a Th2 profile. Furthermore, the IFN-γ−/− mice retained the ability to mount significant titers of WSN and HK virus-specific hemagglutination-inhibiting antibodies. Together, these results are consistent with a protective role of IFN-γ during the heterologous response against influenza virus independently of the generation and local recruitment of cross-reactive CTLs.
The High Mobility Group Protein 1 Is a Coactivator of Herpes Simplex Virus ICP4 In Vitro
Authors: Carrozza Michael J. , DeLuca Neal 
Published: December 2019

ABSTRACT
ICP4 is an activator of herpes simplex virus early and late gene transcription during infection and in vitro can efficiently activate the transcription of a core promoter template containing only a TATA box and an initiator element. In this study, we noted that the extent of activation by ICP4 in vitro was highly dependent on the purity of TFIID when recombinant TFIIB, TFIIE, and TFIIF were used as sources of these factors. ICP4 efficiently activated transcription with a crude TFIID fraction. However, when immunoaffinity-purified TFIID was used in place of the less pure TFIID, ICP4 activated transcription to a significantly lesser extent. This finding indicated that the crude TFIID fraction may contain additional factors that serve as coactivators of ICP4. To test this hypothesis, the crude TFIID preparation was further fractionated by gel filtration chromatography. The TFIID that eluted from the column lacked the hypothesized coactivator activity. A fraction well separated from TFIID contained an activity that when added with the TFIID fraction resulted in higher levels of transcription in the presence ICP4. Further purification of the coactivator-containing fraction resulted in the isolation of a single 30-kDa polypeptide (p30). p30 was also shown to serve as a coactivator of ICP4 with immunoaffinity-purified TFIID; however, p30 had no effect on basal transcription. Amino acid sequence analysis revealed that p30 was the high mobility group protein 1, which has been shown to facilitate the formation of higher-order DNA-protein complexes.
The Papillomavirus E1 Protein Forms a DNA-Dependent Hexameric Complex with ATPase and DNA Helicase Activities
Authors: Sedman Juhan , Stenlund Arne 
Published: December 2019

ABSTRACT
The E1 protein from bovine papillomavirus has site-specific DNA binding activity, DNA helicase activity, and DNA-dependent ATPase activity consistent with the properties of an initiator protein. Here we have identified and characterized a novel oligomeric form of E1 that is associated with the ATPase and DNA helicase activities and whose formation is strongly stimulated by single-stranded DNA. This oligomeric form corresponds to a hexamer of E1.
Inhibition of Herpes Simplex Virus Replication by a 2-Amino Thiazole via Interactions with the Helicase Component of the UL5-UL8-UL52 Complex
Authors: Spector F. C. , Liang L. , Giordano H. , Sivaraja M. , Peterson M. G. 
Published: December 2019

ABSTRACT

With the use of a high-throughput biochemical DNA helicase assay as a screen, T157602, a 2-amino thiazole compound, was identified as a specific inhibitor of herpes simplex virus (HSV) DNA replication. T157602 inhibited reversibly the helicase activity of the HSV UL5-UL8-UL52 (UL5/8/52) helicase-primase complex with an IC
50
(concentration of compound that yields 50% inhibition) of 5 μM. T157602 inhibited specifically the UL5/8/52 helicase and not several other helicases. The primase activity of the UL5/8/52 complex was also inhibited by T157602 (IC
50
= 20 μM). T157602 inhibited HSV growth in a one-step viral growth assay (IC
90
= 3 μM), and plaque formation was completely prevented at concentrations of 25 to 50 μM T157602. Vero, human foreskin fibroblast (HFF), and Jurkat cells could be propagated in the presence of T157602 at concentrations exceeding 100 μM with no obvious cytotoxic effects, indicating that the window between antiviral activity and cellular toxicity is at least 33-fold. Seven independently derived T157602-resistant mutant viruses (four HSV type 2 and three HSV type 1) carried single base pair mutations in the UL5 that resulted in single amino acid changes in the UL5 protein. Marker rescue experiments demonstrated that the UL5 gene from T157602-resistant viruses conferred resistance to T157602-sensitive wild-type viruses. Recombinant UL5/8/52 helicase-primase complex purified from baculoviruses expressing mutant UL5 protein showed complete resistance to T157602 in the in vitro helicase assay. T157602 and its analogs represent a novel class of specific and reversible anti-HSV agents eliciting their inhibitory effects on HSV replication by interacting with the UL5 helicase.