bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vpr Stimulates Viral Expression and Induces Cell Killing in Human Immunodeficiency Virus Type 1-Infected Dividing Jurkat T Cells
Authors: Yao Xiao-Jian , Mouland Andrew J. , Subbramanian Ramu A. , Forget Janique , Rougeau Nicole , Bergeron Dominique , Cohen Eric A. 
Published: December 2019

ABSTRACTIn this study we investigated the effects of Vpr during human immunodeficiency virus (HIV) infection of proliferating Jurkat T cells by using a vesicular stomatitis virus envelope G glycoprotein pseudotyped HIV superinfection system. We observe that the expression of Vpr results in a severe reduction in the life span of HIV type 1 (HIV-1)-infected dividing T cells in culture. In agreement with a recent report (S. A. Stewart, B. Poon, J. B. M. Jowett, and I. S. Chen, J. Virol. 71:5579–5592, 1997), we show that events characteristic of apoptotic cell death are involved in the Vpr-mediated cytopathic effects. Our results also show that infection with viruses expressing the wild-typevprgene results in an increase in viral gene expression and production. Interestingly, the effects of Vpr on cell viability and on viral gene expression both correlate with the ability of the protein to induce a cell cycle arrest in the G2/M phase. Mutagenesis analyses show that the C terminus of Vpr is essential for these biological activities. Although the role of Vpr is currently associated with the infection of nondividing cells, our results suggest that Vpr can also directly increase viral replication in vivo in infected dividing T cells. Furthermore, these in vitro observations suggest that Vpr-mediated cytotoxic effects could contribute to the CD4+depletion associated with AIDS progression.
CD4-Induced Conformational Changes in the Human Immunodeficiency Virus Type 1 gp120 Glycoprotein: Consequences for Virus Entry and Neutralization
Authors: Sullivan Nancy , Sun Ying , Sattentau Quentin , Thali Markus , Wu Dona , Denisova Galina , Gershoni Jonathan , Robinson James , Moore John , Sodroski Joseph 
Published: December 2019

ABSTRACTHuman immunodeficiency virus type 1 (HIV-1) entry into target cells involves sequential binding of the gp120 exterior envelope glycoprotein to CD4 and to specific chemokine receptors. Soluble CD4 (sCD4) is thought to mimic membrane-anchored CD4, and its binding alters the conformation of the HIV-1 envelope glycoproteins. Two cross-competing monoclonal antibodies, 17b and CG10, that recognize CD4-inducible gp120 epitopes and that block gp120-chemokine receptor binding were used to investigate the nature and functional significance of gp120 conformational changes initiated by CD4 binding. Envelope glycoproteins derived from both T-cell line-adapted and primary HIV-1 isolates exhibited increased binding of the 17b antibody in the presence of sCD4. CD4-induced exposure of the 17b epitope on the oligomeric envelope glycoprotein complex occurred over a wide range of temperatures and involved movement of the gp120 V1/V2 variable loops. Amino acid changes that reduced the efficiency of 17b epitope exposure following CD4 binding invariably compromised the ability of the HIV-1 envelope glycoproteins to form syncytia or to support virus entry. Comparison of the CD4 dependence and neutralization efficiencies of the 17b and CG10 antibodies suggested that the epitopes for these antibodies are minimally accessible following attachment of gp120 to cell surface CD4. These results underscore the functional importance of these CD4-induced changes in gp120 conformation and illustrate viral strategies for sequestering chemokine receptor-binding regions from the humoral immune response.
Specific Interaction of Eukaryotic Translation Initiation Factor 3 with the 5′ Nontranslated Regions of Hepatitis C Virus and Classical Swine Fever Virus RNAs
Authors: Sizova Daria V. , Kolupaeva Victoria G. , Pestova Tatyana V. , Shatsky Ivan N. , Hellen Christopher U. T. 
Published: December 2019

ABSTRACT

Translation of hepatitis C virus (HCV) and classical swine fever virus (CSFV) RNAs is initiated by cap-independent attachment (internal entry) of ribosomes to the ∼350-nucleotide internal ribosomal entry segment (IRES) at the 5′ end of both RNAs. Eukaryotic initiation factor 3 (eIF3) binds specifically to HCV and CSFV IRESs and plays an essential role in the initiation process on them. Here we report the results of chemical and enzymatic footprinting analyses of binary eIF3-IRES complexes, which have been used to identify the eIF3 binding sites on HCV and CSFV IRESs. eIF3 protected an internal bulge in the apical stem IIIb of domain III of the CSFV IRES from chemical modification and protected bonds in and adjacent to this bulge from cleavage by RNases ONE and V
1
. eIF3 protected an analagous region in domain III of the HCV IRES from cleavage by these enzymes. These results are consistent with the results of primer extension analyses and were supported by observations that deletion of stem-loop IIIb or of the adjacent hairpin IIIc from the HCV IRES abrogated the binding of eIF3 to this RNA. This is the first report that eIF3 is able to bind a eukaryotic mRNA in a sequence- or structure-specific manner. UV cross-linking of eIF3 to [
32
P]UTP-labelled HCV and CSFV IRES elements resulted in strong labelling of 4 (p170, p116, p66, and p47) of the 10 subunits of eIF3, 1 or more of which are likely to be determinants of these interactions. In the cytoplasm, eIF3 is stoichiometrically associated with free 40S ribosomal subunits. The results presented here are consistent with a model in which binding of these two translation components to separate, specific sites on both HCV and CSFV IRESs enhances the efficiency and accuracy of binding of these RNAs to 40S subunits in an orientation that promotes entry of the initiation codon into the ribosomal P site.
An Evolutionarily Conserved Splice Generates a Secreted Env-Bet Fusion Protein during Human Foamy Virus Infection
Authors: Giron Marie-Louise , de Thé Hugues , Saïb Ali 
Published: December 2019

ABSTRACT

Foamy viruses (spumaretroviruses) represent a retroviral genus which exhibits unusual features relating it to pararetroviruses. Previously, we reported the existence of a protein species harboring Env, Bel, and Bet epitopes in human foamy virus (HFV)-infected cells (M. L. Giron, F. Rozain, M. C. Debons-Guillemin, M. Canivet, J. Périès, and R. Emanoil-Ravier, J. Virol. 67:3596–3600, 1993). Here, we identify this protein as a 160-kDa Env-Bet fusion glycoprotein (gp160) translated from an mRNA species harboring a highly conserved splice site which deletes the membrane anchor domain of Env and fuses the
env
open reading frame with that of
bel1/bet
. While gp160 and Bet proteins were both secreted into the supernatant, only Bet was taken up by recipient cells. Since Bet plays a key role in the switch from lytic to chronic infection, secretion of Bet and gp160, together with cellular uptake of Bet, could be highly relevant for both immune response and development of HFV infection in vivo.
Transcription Factor YY1 Represses Cell-Free Replication from Human Papillomavirus Origins
Authors: Lee Kyung-Yeol , Broker Thomas R. , Chow Louise T. 
Published: December 2019

ABSTRACT

We have established cell-free replication for the human papillomavirus type 18 (HPV-18) origin of replication (
ori
)-containing DNA by using purified HPV-18 E1 and E2 gene products expressed as fusion proteins in
Escherichia coli
. The transcription factor YY1 has been shown to regulate RNA transcription by binding to a sequence overlapping the putative E1 protein binding site in the HPV-18
ori
. We show that exogenously added YY1 fusion protein inhibited HPV-18
ori
replication. Cotransfection of YY1 expression vectors also inhibited transient replication in 293 cells. However, inhibition did not appear to be mediated by binding to its cognate site in the
ori
as YY1 also inhibited the replication of the HPV-11
ori
, which does not have a known or suspected YY1 binding site. Moreover, inhibition was not alleviated by the inclusion of YY1 binding oligonucleotides in the replication reaction mixtures. Rather, we demonstrated a direct interaction between purified fusion E2 protein and fusion YY1 protein by the pull-down assay and a partial restoration of replication activity by an elevated E2 protein concentration. These results suggest that YY1 can inhibit HPV
ori
replication by interfering with E2 protein functions.
Transmissible Gastroenteritis Coronavirus Induces Programmed Cell Death in Infected Cells through a Caspase-Dependent Pathway
Authors: Eleouet Jean-François , Chilmonczyk Stefan , Besnardeau Lydia , Laude Hubert 
Published: December 2019

ABSTRACT

In this report, we show that apoptosis (or programmed cell death) is induced in different cell lines infected with a coronavirus, the porcine transmissible gastroenteritis virus (TGEV). Kinetic analysis of internucleosomal DNA cleavage by agarose gel electrophoresis and flow cytometry or cytometric monitoring of the mitochondrial transmembrane potential showed that, for ST cells infected with TGEV, the first overt signs of apoptosis appeared from 10 to 12 h postinfection on. They preceded morphological changes characteristic of cells undergoing apoptosis, as observed by light and electron microscopy. The tripeptide pan-ICE (caspase) inhibitor
N
-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone blocked TGEV-induced apoptosis with no effect on virus production. The thiol agent pyrrolidine dithiocarbamate inhibited apoptosis, suggesting that TGEV infection may lead to apoptosis via cellular oxidative stress. The effect of TGEV infection on activation of NF-κB, a transcription factor known to be activated by oxidative stress, was examined. NF-κB DNA binding was shown to be strongly and quickly induced by TGEV infection. However, transcription factor decoy experiments showed that NF-κB activation is not critical for TGEV-induced apoptosis.
Identification of Kaposin (Open Reading Frame K12) as a Human Herpesvirus 8 (Kaposi’s Sarcoma-Associated Herpesvirus) Transforming Gene
Authors: Muralidhar Sumitra , Pumfery Anne M. , Hassani Morad , Sadaie M. Reza , Azumi Norio , Kishishita Masamichi , Brady John N. , Doniger Jay , Medveczky Peter , Rosenthal Leonard J. 
Published: December 2019

ABSTRACT

The recently identified human herpesvirus 8 (HHV-8, or Kaposi’s sarcoma-associated herpesvirus) has been implicated in the etiology of both Kaposi’s sarcoma (KS) and primary effusion (body cavity-based) lymphoma (PEL) (Y. Chang et al., Science 266:1865–1869, 1994; P. S. Moore et al., J. Virol. 70:549–558, 1996). An important feature of the association of HHV-8 with these malignancies is the expression of an abundant, latency-associated 0.7-kb transcript, T0.7 (W. Zhong et al., Proc. Natl. Acad. Sci. USA 93:6641–6646, 1996). T0.7 is found in all stages in nearly all KS tumors of different epidemiologic origin, including AIDS-associated, African endemic, and classical KS (K. A. Staskus et al., J. Virol. 71:715–719, 1997), as well as in a body cavity-based lymphoma-derived cell line, BCBL-1, that is latently infected with HHV-8 (R. Renne et al., Nat. Med. 2:342–346, 1996). T0.7 encodes a unique HHV-8 open reading frame, K12, also known as kaposin. In this study, we report that the kaposin gene induced tumorigenic transformation. Constructs with kaposin expressed either from its endogenous promoter or from a heterologous promoter induced focal transformation upon transfection into Rat-3 cells. All transformed Rat-3 cell lines containing kaposin sequences produced high-grade, highly vascular, undifferentiated sarcomas upon subcutaneous injection of athymic
nu/nu
mice. Tumor-derived cell lines expressed kaposin mRNA, suggesting a role in the maintenance of the transformed phenotype. Furthermore, kaposin protein was detected in transformed and tumor-derived cells by immunofluorescence and localized to the cytoplasm. More importantly, expression of kaposin protein was also detected in the PEL cell lines BCBL-1 and KS-1. These findings demonstrate the oncogenic potential of kaposin and suggest its possible role in the development of KS and other HHV-8-associated malignancies.
Role of Rta in the Translation of Bicistronic BZLF1 of Epstein-Barr Virus
Authors: Chang Pey-Jium , Chang Yu-Sun , Liu Shih-Tung 
Published: December 2019

ABSTRACT

The BZLF1 gene of Epstein-Barr virus (EBV), which encodes a transcription factor, Zta, is transcribed into monocistronic and bicistronic mRNAs from two different promoters during the immediate-early stage of the EBV lytic cycle. It is generally accepted that the Zta protein translated from the monocistronic mRNA profoundly influences the activation of the EBV lytic cycle. In this study, we constructed a plasmid, pCMV-RZLUC, which can transcribe a bicistronic mRNA consisting of BRLF1 and a BZLF1-
luc
fusion gene under latent conditions. P3HR1 cells transfected with this plasmid produce a luciferase activity which is approximately 17-fold higher than the activity exhibited by pRZLUC, a plasmid incapable of transcribing the bicistronic mRNA. Genetic analyses indicated that mutations in BRLF1 not only can decrease the translation of the fusion gene from the bicistronic mRNA but can also be complemented by a functional BRLF1 gene in
cis
. This observation implies that the product of BRLF1, Rta, is involved in the translation of the downstream gene. Results presented herein also demonstrate that these mutations cannot be complemented in
trans
with a plasmid overexpressing Rta, suggesting that the amount of Rta in the vicinity of the intercistronic region may be crucial for the translation. Furthermore, our results correspond to those of previous investigations indicating that the Zta protein can be translated from the bicistronic mRNA and that, similar to the translation of bicistronic ZLUC, mutations in BRLF1 also hinder the translation of Zta from the BRLF1-BZLF1 bicistronic mRNA. Translation of Zta from the bicistronic mRNA may play an essential role in the activation of the EBV lytic cycle.
Complete Genomic Sequence of Border Disease Virus, a Pestivirus from Sheep
Authors: Becher Paul , Orlich Michaela , Thiel Heinz-Jürgen 
Published: December 2019

ABSTRACT

The genus
Pestivirus
of the family
Flaviviridae
comprises three established species, namely, bovine viral diarrhea virus (BVDV), classical swine fever virus (CSFV), and border disease virus from sheep (BDV). In this study, we report the first complete nucleotide sequence of BDV, that of strain X818. The genome is 12,333 nucleotides long and contains one long open reading frame encoding 3,895 amino acids. The 5′ noncoding region (NCR) of BDV X818 consists of 372 nucleotides and is thus similar in length to the 5′ NCR reported for other pestiviruses. The 3′ NCR of X818 is 273 nucleotides long and thereby at least 32 nucleotides longer than the 3′ NCR of pestiviruses analyzed thus far. Within the 3′ NCR of BDV X818, the sequence motif TATTTATTTA was identified at four locations. The same repeat was found at two or three locations within the 3′ NCR of different CSFV isolates but was absent in the 3′ NCR of BVDV. Analysis of five additional BDV strains showed that the 3′ NCR sequences are highly conserved within this species. Comparison of the deduced amino acid sequence of X818 with the ones of other pestiviruses allowed the prediction of polyprotein cleavage sites which were conserved with regard to the structural proteins. It has been reported for two BVDV strains that cleavage at the nonstructural (NS) protein sites 3/4A, 4A/4B, 4B/5A, and 5A/5B is mediated by the NS3 serine protease and for each site a conserved leucine was found at the P1 position followed by either serine or alanine at P1′ (N. Tautz, K. Elbers, D. Stoll, G. Meyers, and H.-J. Thiel, J. Virol. 71:5415–5422, 1997; J. Xu, E. Mendez, P. R. Caron, C. Lin, M. A. Murcko, M. S. Collett, and C. M. Rice, J. Virol. 71:5312–5322). Interestingly, P1′ of the predicted NS5A/5B cleavage site of BDV is represented by an asparagine residue. Transient expression studies demonstrated that this unusual NS5A/5B processing site is efficiently cleaved by the NS3 serine protease of BDV.
Functional Interaction of Human Immunodeficiency Virus Type 1 Vpu and Gag with a Novel Member of the Tetratricopeptide Repeat Protein Family
Authors: Callahan Michael A. , Handley Mark A. , Lee Yung-Hui , Talbot Katrin J. , Harper J. Wade , Panganiban Antonito T. 
Published: December 2019

ABSTRACT
Viral protein U (Vpu) is a protein encoded by human immunodeficiency virus type 1 (HIV-1) that promotes the degradation of the virus receptor, CD4, and enhances the release of virus particles from cells. We isolated a cDNA that encodes a novel cellular protein that interacts with Vpu in vitro, in vivo, and in yeast cells. This Vpu-binding protein (UBP) has a molecular mass of 41 kDa and is expressed ubiquitously in human tissues at the RNA level. UBP is a novel member of the tetratricopeptide repeat (TPR) protein family containing four copies of the 34-amino-acid TPR motif. Other proteins that contain TPR motifs include members of the immunophilin superfamily, organelle-targeting proteins, and a protein phosphatase. UBP also interacts directly with HIV-1 Gag protein, the principal structural component of the viral capsid. However, when Vpu and Gag are coexpressed, stable interaction between UBP and Gag is diminished. Furthermore, overexpression of UBP in virus-producing cells resulted in a significant reduction in HIV-1 virion release. Taken together, these data indicate that UBP plays a role in Vpu-mediated enhancement of particle release.
Measles Virus Infection and Replication in Undifferentiated and Differentiated Human Neuronal Cells in Culture
Authors: McQuaid S. , Campbell S. , Wallace I. J. C. , Kirk J. , Cosby S. L. 
Published: December 2019

ABSTRACT
Measles virus (MV) infection of the human central nervous system (CNS) typically involves widespread infection of neurons. However, little is known about how they become infected, how defective virus arises and accumulates, or how virus spreads among the cells of the CNS. In vitro studies of viral interactions with human neuronal cells may contribute to the resolution of such issues. In mixed cultures containing differentiated human neuronal (hNT2) cells and neuroepithelial cells, immunofluorescence studies show that the neurons, unlike both their NT2 progenitors and the neuroepithelial cells, are not initially susceptible to MV infection. This is possibly due to their lack of expression of CD46, a known cell surface receptor for MV. Later in the course of infection, however, both MV proteins and genomic RNA become detectable in their processes, where they contact infected, fully permissive neuroepithelial cells. Such a mechanism of virus transfer may be involved in the initiation and spread of persistent MV infection in diseases such as subacute sclerosing panencephalitis. Furthermore, mutated defective virus may readily accumulate and spread without the need, at any stage, for viral maturation and budding.
Actin-Dependent Receptor Colocalization Required for Human Immunodeficiency Virus Entry into Host Cells
Authors: Iyengar Sujatha , Hildreth James E. K. , Schwartz David H. 
Published: December 2019

ABSTRACTHuman immunodeficiency virus (HIV) envelope binds CD4 and a chemokine receptor in sequence, releasing hydrophobic viral gp41 residues into the target membrane. HIV entry required actin-dependent concentration of coreceptors, which could be disrupted by cytochalasin D (CytoD) without an effect on cell viability or mitosis. Pretreatment of peripheral blood mononuclear cells, but not virus, inhibited entry and infection. Immunofluorescent confocal microscopy of activated cells revealed CD4 and CXCR4 in nonoverlapping patterns. Addition of gp120 caused polarized cocapping of both molecules with subsequent pseudopod formation, while CytoD pretreatment blocked these membrane changes completely.
The N-Terminal Extension of the Influenza B Virus Nucleoprotein Is Not Required for Nuclear Accumulation or the Expression and Replication of a Model RNA
Authors: Stevens Mark P. , Barclay Wendy S. 
Published: December 2019

ABSTRACT
The nucleoprotein (NP) of influenza B virus is 50 amino acids longer at the N-terminus than influenza A virus NP and lacks homology to the A virus protein over the first 69 residues. We have deleted the N-terminal 51 and 69 residues of the influenza B/Ann Arbor/1/66 virus NP and show that nuclear accumulation of the protein is unaffected. This indicates that the nuclear localization signal is not located at the extreme N terminus, as in influenza A virus NP. To determine if the N-terminal mutants could support the expression and replication of a model influenza B virus RNA, the genes encoding the subunits of the viral RNA-dependent RNA polymerase (PA, PB1, and PB2) were cloned. Coexpression of NP and the P proteins in 293 cells was found to permit the expression and replication of a transfected model RNA based on segment 4 of B/Maryland/59, in which the hemagglutinin-coding region was replaced by a chloramphenicol acetyltransferase gene. The expression and replication of the synthetic RNA were not affected by the replacement of NP with NP mutants lacking the N-terminal 51 or 69 residues, indicating that the N-terminal extension is not required for transcription or replication of the viral RNA. In addition, we report that the influenza B virus NP cannot be functionally replaced by type A virus NP in this system.
Role for β2-Microglobulin in Echovirus Infection of Rhabdomyosarcoma Cells
Authors: Ward Trevor , Powell Robert M. , Pipkin Pamela A. , Evans David J. , Minor Phillip D. , Almond Jeffrey W. 
Published: December 2019

ABSTRACT
A monoclonal antibody (MAb) that blocks most echoviruses (EVs) from infecting rhabdomyosarcoma (RD) cells has been isolated. By using the CELICS cloning method (T. Ward, P. A. Pipkin, N. A. Clarkson, D. M. Stone, P. D. Minor, and J. W. Almond, EMBO J. 13:5070–5074, 1994), the ligand for this antibody has been identified as β2-microglobulin (β2m), the 12-kDa protein that associates with class I heavy chains to form class I HLA complexes. A commercial MAb (MAb 1350) against β2m was also found to block EV7 infection without affecting binding to its receptor, DAF, or replication of EV7 viral RNA inside cells. Entry of EV7 into cells was reduced by only 30% by antibody and cytochalasin D, an inhibitor of endocytosis mediated by caveolae and clathrin-coated pits, but was not significantly reduced by sodium azide. The block to virus entry by cytochalasin D was additive to the block induced by antibody. We suggest that EV7 rapidly enters into a multicomponent receptor complex prior to entry into cells and that this initial entry event requires β2m or class I HLA for infection to proceed.