bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epstein-Barr Virus Exploits BSAP/Pax5 To Achieve the B-Cell Specificity of Its Growth-Transforming Program
Authors: Tierney Rosemary , Nagra Jasdeep , Hutchings Isabel , Shannon-Lowe Claire , Altmann Markus , Hammerschmidt Wolfgang , Rickinson Alan , Bell Andrew 
Published: July 2007

ABSTRACT
Epstein-Barr virus (EBV) can infect various cell types but limits its classical growth-transforming function to B lymphocytes, the cells in which it persists in vivo. Transformation initiates with the activation of Wp, a promoter present as tandemly repeated copies in the viral genome. Assays with short Wp reporter constructs have identified two promoter-activating regions, one of which (UAS2) appears to be lineage independent, while the other (UAS1) was B-cell specific and contained two putative binding sites for the B-cell-specific activator protein BSAP/Pax5. To address the physiologic relevance of these findings, we first used chromosome immunoprecipitation assays and found that BSAP is indeed bound to Wp sequences on the EBV genome in transformed cells. Thereafter, we constructed recombinant EBVs carrying two Wp copies, both wild type, with UAS1 or UAS2 deleted, or mutated in the BSAP binding sites. All the viruses delivered their genomes to the B-cell nucleus equally well. However, the BSAP binding mutant (and the virus with UAS1 deleted) showed no detectable activity in B cells, whether measured by early Wp transcription, expression of EBV latent proteins, or outgrowth of transformed cells. This was a B-cell-specific defect since, on entry into epithelial cells, an environment where Wp is not the latent promoter of choice, all the Wp mutant viruses initiated infection as efficiently as wild-type virus. We infer that EBV ensures the B-cell specificity of its growth-transforming function by exploiting BSAP/Pax5 as a lineage-specific activator of the transforming program.
The Cytoplasmic Tail of Glycoprotein M (gpUL100) Expresses Trafficking Signals Required for Human Cytomegalovirus Assembly and Replication
Authors: Krzyzaniak Magdalena , Mach Michael , Britt William J. 
Published: July 2007

ABSTRACT
The virion envelope of human cytomegalovirus (HCMV) is complex and consists of an incompletely defined number of glycoproteins. The gM/gN protein complex is the most abundant protein component of the envelope. Studies have indicated that deletion of the viral gene encoding either gM or gN is a lethal mutation. Analysis of the amino acid sequence of gM disclosed a C-terminal acidic cluster of amino acids and a tyrosine-containing trafficking motif, both of which are well-described trafficking/sorting signals in the cellular secretory pathway. To investigate the roles of these signals in the trafficking of the gM/gN complex during virus assembly, we made a series of gM (UL100 open reading frame) mutants in the AD169 strain of HCMV. Mutant viruses that lacked the entire C-terminal cytoplasmic tail of gM were not viable, suggesting that the cytoplasmic tail of gM is essential for virus replication. In addition, the gM mutant protein lacking the cytoplasmic domain exhibited decreased protein stability. Mutant viruses with a deletion of the acidic cluster or alanine substitutions in tyrosine-based motifs were viable but exhibited a replication-impaired phenotype suggestive of a defect in virion assembly. Analysis of these mutant gMs using static immunofluorescence and fluorescence recovery after photobleaching demonstrated delayed kinetics of intracellular localization of the gM/gN protein to the virus assembly compartment compared to the wild-type protein. These data suggest an important role of the glycoprotein gM during virus assembly, particularly in the dynamics of gM trafficking during viral-particle assembly.
Although Macrophage-Tropic Simian/Human Immunodeficiency Viruses Can Exhibit a Range of Pathogenic Phenotypes, a Majority of Isolates Induce No Clinical Disease in Immunocompetent Macaques
Authors: Igarashi Tatsuhiko , Donau Olivia K. , Imamichi Hiromi , Nishimura Yoshiaki , Theodore Theodore S. , Iyengar Ranjini , Erb Christopher , Buckler-White Alicia , Buckler Charles E. , Martin Malcolm A. 
Published: July 2007

ABSTRACTUnlike prototypical lentiviruses like visna and caprine arthritis-encephalitis viruses, which are mainly macrophage tropic (M-tropic), primate lentiviruses primarily target CD4+T lymphocytes. We previously reported that during the late phase of highly pathogenic chimeric simian/human immunodeficiency virus (SHIV) infections of rhesus macaques, when CD4+T cells have been systemically eliminated, high levels of viremia are maintained from productively infected macrophages. The availability of several different M-tropic SHIVs from such late-stage immunocompromised animals provided the opportunity to assess whether they might contribute to the immune deficiency induced by their T-cell-tropic parental viruses or possibly cause a distinct disease based on their capacity to infect macrophages. Pairs of rhesus monkeys were therefore inoculated intravenously with six different M-tropic SHIV preparations, and their plasma viral RNA loads, circulating lymphocyte subset numbers, and eventual disease outcomes were monitored. Only one of these six M-tropic SHIVs induced any disease; the disease phenotype observed was the typical rapid, complete, and irreversible depletion of CD4+T cells induced by pathogenic SHIVs. An analysis of two asymptomatic monkeys, previously inoculated with an M-tropic SHIV recovered directly from alveolar macrophages, revealed that this inoculum targeted alveolar macrophages in vivo, compared to a T-cell-tropic virus, yet no clinical disease occurred. Although one isolate did, in fact, induce the prototypical rapid, irreversible, and complete loss of CD4+T cells, indicating that M-tropism and pathogenicity may not be inversely related, the majority of M-tropic SHIVs induced no clinical disease in immunocompetent macaques.
Molecular Mechanisms by Which Human Immunodeficiency Virus Type 1 Integrase Stimulates the Early Steps of Reverse Transcription
Authors: Dobard Charles W. , Briones Marisa S. , Chow Samson A. 
Published: July 2007

ABSTRACT

Reverse transcriptase (RT) and integrase (IN) are two essential enzymes that play a critical role in synthesis and integration of the retroviral cDNA, respectively. For human immunodeficiency virus type 1 (HIV-1), RT and IN physically interact and certain mutations and deletions of IN result in viruses defective in early steps of reverse transcription. However, the mechanism by which IN affects reverse transcription is not understood. We used a cell-free reverse transcription assay with different primers and compositions of deoxynucleoside triphosphates to differentially monitor the effect of IN on the initiation and elongation modes of reverse transcription. During the initiation mode, addition of IN stimulated RT-catalyzed reverse transcription by fourfold. The stimulation was specific to IN and could not be detected when the full-length IN was replaced with truncated IN derivatives. The IN-stimulated initiation was also restricted to the template-primer complex formed using tRNA
3
Lys
or short RNA oligonucleotides as the primer and not those formed using DNA oligonucleotides as the primer. Addition of IN also produced a threefold stimulation during the elongation mode, which was not primer dependent. The stimulation of both initiation and elongation by IN was retained in the presence of an RT trap. Furthermore, IN had no effect on steps at or before template-primer annealing, including packaging of viral genomic RNA and tRNA
3
Lys
. Taken together, our results showed that IN acts at early steps of reverse transcription by increasing the processivity of RT and suppressing the formation of the pause products.
Arterivirus Subgenomic mRNA Synthesis and Virion Biogenesis Depend on the Multifunctional nsp1 Autoprotease
Authors: Tijms Marieke A. , Nedialkova Danny D. , Zevenhoven-Dobbe Jessika C. , Gorbalenya Alexander E. , Snijder Eric J. 
Published: July 2007

ABSTRACT

Many groups of plus-stranded RNA viruses produce additional, subgenomic mRNAs to regulate the expression of part of their genome. Arteriviruses and coronaviruses (order
Nidovirales
) are unique among plus-stranded RNA viruses for using a mechanism of discontinuous RNA synthesis to produce a nested set of 5′- and 3′-coterminal subgenomic mRNAs, which serve to express the viral structural protein genes. The discontinuous step presumably occurs during minus-strand synthesis and joins noncontiguous sequences copied from the 3′- and 5′-proximal domains of the genomic template. Nidovirus genome amplification (“replication”) and subgenomic mRNA synthesis (“transcription”) are driven by 13 to 16 nonstructural proteins (nsp's), generated by autocatalytic processing of two large “replicase” polyproteins. Previously, using a replicon system, the N-terminal nsp1 replicase subunit of the arterivirus equine arteritis virus (EAV) was found to be dispensable for replication but crucial for transcription. Using reverse genetics, we have now addressed the role of nsp1 against the background of the complete EAV life cycle. Mutagenesis revealed that nsp1 is in fact a multifunctional regulatory protein. Its papain-like autoprotease domain releases nsp1 from the replicase polyproteins, a cleavage essential for viral RNA synthesis. Several mutations in the putative N-terminal zinc finger domain of nsp1 selectively abolished transcription, while replication was either not affected or even increased. Other nsp1 mutations did not significantly affect either replication or transcription but still dramatically reduced the production of infectious progeny. Thus, nsp1 is involved in at least three consecutive key processes in the EAV life cycle: replicase polyprotein processing, transcription, and virion biogenesis.
ZEB1 and c-Jun Levels Contribute to the Establishment of Highly Lytic Epstein-Barr Virus Infection in Gastric AGS Cells
Authors: Feng Wen-hai , Kraus Richard J. , Dickerson Sarah J. , Lim Hui Jun , Jones Richard J. , Yu Xianming , Mertz Janet E. , Kenney Shannon C. 
Published: July 2007

ABSTRACTThe induction of lytic infection has been proposed as a therapeutic strategy for treating Epstein-Barr virus (EBV)-positive malignancies. To succeed, efficient methods are needed for activating the EBV immediate-early (IE) promoters, Zp and Rp. Here we compared factors which regulate Zp and Rp in AGS gastric carcinoma cells that support a remarkably high level of persistently lytic EBV infection with HeLa cervical cells that permit only tightly latent infection. We found that the level of Zp activity assayed by transient transfection assays with reporter plasmids was high in AGS cells but low in HeLa cells. The level of Rp activity was low in both cell types. Mutational analysis indicated that sequences within Zp located between −70 and +27 relative to the transcription initiation site were sufficient to confer a high level of Zp activity in AGS cells. The Zp CRE motif was necessary for this constitutive activity, while the ZIA and ZIB MEF2D motifs were not. Consistent with these findings, immunoblot analysis indicated that phosphorylated c-Jun, which activates Zp through the CRE motif, was expressed at a much higher level in EBV-infected AGS cells than in EBV-infected HeLa cells. In contrast, ZEB1, which represses Zp via the ZV motif located near the transcription initiation site, was abundant in HeLa cells, while it was absent from AGS cells. Exogenous addition of ZEB1 led to the repression of Zp in AGS cells. We conclude that the unusually high Zp activity level in AGS cells is due to the high abundance of positively acting transcription factors such as c-Jun combined with the low abundance of negatively acting factors such as ZEB1.
Hepatitis C Virus Stabilizes Hypoxia-Inducible Factor 1α and Stimulates the Synthesis of Vascular Endothelial Growth Factor
Authors: Nasimuzzaman Md , Waris Gulam , Mikolon David , Stupack Dwayne G. , Siddiqui Aleem 
Published: July 2007

ABSTRACT
Hepatitis C virus (HCV) infection is one of the major causes of chronic hepatitis, liver cirrhosis, which subsequently leads to hepatocellular carcinoma (HCC). The overexpression of the angiogenic factors has been demonstrated in HCC. In this study, we investigated the potential of HCV gene expression in inducing angiogenesis. Our results show that HCV infection leads to the stabilization of hypoxia-inducible factor 1α (HIF-1α). We further show that this stabilization was mediated via oxidative stress induced by HCV gene expression. The activation of NF-κB, STAT-3, PI3-K/AkT, and p42/44 mitogen-activated protein kinase was necessary for HIF-1α stabilization. HIF-1α induction in turn led to the stimulation of vascular endothelial growth factor. By using the chick chorioallantoic membrane assay, we show that HCV-infected cells released angiogenic cytokines, leading to neovascularization in vivo. These results indicate the potential of HCV gene expression in angiogenesis.
Analysis of Viral
cis
Elements Conferring Kaposi's Sarcoma-Associated Herpesvirus Episome Partitioning and Maintenance
Authors: Skalsky Rebecca L. , Hu Jianhong , Renne Rolf 
Published: July 2007

ABSTRACT

Maintenance of Kaposi's sarcoma-associated herpesvirus (KSHV) episomes in latently infected cells is dependent on the latency-associated nuclear antigen (LANA). LANA binds to the viral terminal repeats (TR), leading to recruitment of cellular origin recognition complex proteins. Additionally, LANA tethers episomes to chromosomes via interactions with histones H2A and H2B (A. J. Barbera et al., Science
311
:856-861, 2006). Despite these molecular details, less is known about how episomes are established after de novo infection. To address this, we measured short-term retention rates of green fluorescent protein-expressing replicons in proliferating lymphoid cells. In the absence of antibiotic selection, LANA significantly reduced the loss rate of TR-containing replicons. Additionally, we found that LANA can support long-term stability of KSHV replicons for more than 2 months under nonselective conditions. Analysis of
cis
elements within TR that confer episome replication and partitioning revealed that these activities can occur independently, and furthermore, both events contribute to episome stability. We found that replication-deficient plasmids containing LANA binding sites (LBS1/2) exhibited measurable retention rates in the presence of LANA. To confirm these observations, we uncoupled KSHV replication and partitioning by constructing hybrid origins containing the Epstein-Barr virus (EBV) dyad symmetry for plasmid replication and KSHV LBS1/2. We demonstrate that multiple LBS1/2 function in a manner analogous to that of the EBV family of repeats by forming an array of LANA binding sites for partitioning of KSHV genomes. Our data suggest that the efficiency with which KSHV establishes latency is dependent on multiple LANA activities, which stabilize viral genomes early after de novo infection.
CD40-CD40 Ligand Interactions Promote Trafficking of CD8
+
T Cells into the Brain and Protection against West Nile Virus Encephalitis
Authors: Sitati Elizabeth , McCandless Erin E. , Klein Robyn S. , Diamond Michael S. 
Published: July 2007

ABSTRACT

Recent studies have established a protective role for T cells during primary West Nile virus (WNV) infection. Binding of CD40 by CD40 ligand (CD40L) on activated CD4
+
T cells provides an important costimulatory signal for immunoglobulin class switching, antibody affinity maturation, and priming of CD8
+
T-cell responses. We examined here the function of CD40-dependent interactions in limiting primary WNV infection. Compared to congenic wild-type mice, CD40
−/−
mice uniformly succumbed to WNV infection. Although CD40
−/−
mice produced low levels of WNV-specific immunoglobulin M (IgM) and IgG, viral clearance from the spleen and serum was not altered, and CD8
+
T-cell priming in peripheral lymphoid tissues was normal. Unexpectedly, CD8
+
T-cell trafficking to the central nervous system (CNS) was markedly impaired in CD40
−/−
mice, and this correlated with elevated WNV titers in the CNS and death. In the brains of CD40
−/−
mice, T cells were retained in the perivascular space and did not migrate into the parenchyma, the predominant site of WNV infection. In contrast, in wild-type mice, T cells trafficked to the site of infection in neurons. Beside its role in maturation of antibody responses, our experiments suggest a novel function of CD40-CD40L interactions: to facilitate T-cell migration across the blood-brain barrier to control WNV infection.
PrP
c
Does Not Mediate Internalization of PrP
Sc
but Is Required at an Early Stage for De Novo Prion Infection of Rov Cells
Authors: Paquet Sophie , Daude Nathalie , Courageot Marie-Pierre , Chapuis Jérôme , Laude Hubert , Vilette Didier 
Published: July 2007

ABSTRACT

We have studied the interactions of exogenous prions with an epithelial cell line inducibly expressing PrP
c
protein and permissive to infection by a sheep scrapie agent. We demonstrate that abnormal PrP (PrP
Sc
) and prion infectivity are efficiently internalized in Rov cells, whether or not PrP
c
is expressed. At odds with earlier studies implicating cellular heparan sulfates in PrP
Sc
internalization, we failed to find any involvement of such molecules in Rov cells, indicating that prions can enter target cells by several routes. We further show that PrP
Sc
taken up in the absence of PrP
c
was unable to promote efficient prion multiplication once PrP
c
expression was restored in the cells. This observation argues that interaction of PrP
Sc
with PrP
c
has to occur early, in a specific subcellular compartment(s), and is consistent with the view that the first prion multiplication events may occur at the cell surface.
CCR5 and CXCR3 Are Dispensable for Liver Infiltration, but CCR5 Protects against Virus-Induced T-Cell-Mediated Hepatic Steatosis
Authors: Holst P. J. , Orskov C. , Qvortrup K. , Christensen J. P. , Thomsen A. R. 
Published: July 2007

ABSTRACTCCR5 and CXCR3 are important molecules in regulating the migration of activated lymphocytes. Thus, the majority of tissue-infiltrating T cells found in the context of autoimmune conditions and viral infections express CCR5 and CXCR3, and the principal chemokine ligands are expressed within inflamed tissues. Accordingly, intervention studies have pointed to nonredundant roles of these receptors in models of allograft rejection, viral infection, and autoimmunity. In spite of this, considerable controversy exists, with many studies failing to support a role for CCR5 or CXCR3 in disease pathogenesis. One possible explanation is that different chemokine receptors may take over in the absence of any individual receptor, thus rendering individual receptors redundant. We have attempted to address this issue by analyzing CCR5−/−, CXCR3−/−, and CCR5/CXCR3−/−mice with regard to virus-induced liver inflammation, generation and recruitment of effector cells, virus control, and immunopathology. Our results indicate that CCR5 and CXCR3 are largely dispensable for tissue infiltration and virus control. In contrast, the T-cell response is accelerated in CCR5−/−and CCR5/CXCR3−/−mice and the absence of CCR5 is associated with the induction of CD8+T-cell-mediated immunopathology consisting of marked hepatic microvesicular steatosis.
Exposure to hardly soluble indium compounds in ITO production and recycling plants is a new risk for interstitial lung damage
Authors: Hamaguchi T , Omae K , Takebayashi T , Kikuchi Y , Yoshioka N , Nishiwaki Y , Tanaka A , Hirata M , Taguchi O , Chonan T 
Published: July 2007

Objectives:To identify the effects of indium on the lung and to assess exposure-effect and exposure-response relations between indium exposure and effects on the lungs.Methods:Ninety three male indium exposed and 93 male non-exposed workers from four ITO manufacturing or ITO recycling plants were analysed in a cross-sectional study. Indium in serum (In-S) was determined as a biological exposure index. Geometric means (GSD) of In-S were 8.25 ng/ml (4.55) in the exposed workers and 0.25 (2.64) in the non-exposed workers. The maximum concentration of In-S was 116.9 ng/ml. A questionnaire for respiratory symptoms and job histories, spirometry, high-resolution computerised tomography (HRCT) of the chest, serum KL-6, serum SP-A, serum SP-D and serum CRP were measured as the effect indices.Results:Spirometry, subjective symptoms and the prevalence of interstitial or emphysematous changes on lung HRCT showed no differences between exposed and non-exposed workers. Geometric means (GSD) of KL-6, SP-D and SP-A in the exposed workers were 495.4 U/ml (2.26), 85.2 ng/ml (2.02) and 39.6 ng/ml (1.57), and were significantly higher than those in the non-exposed workers. The prevalence (%) of the exposed and non-exposed workers exceeding the reference values were also significantly higher in KL-6 (41.9 vs 2.2), SP-D (39.8 vs 7.5), and SP-A (43.0 vs 24.7). Very sharp exposure-effect and exposure-response relations were discovered between In-S and KL-6 and between In-S and SP-D when the exposed workers were classified into seven groups by In-S.Conclusions:The study outcomes with regard to the basis of serum immunochemistry biomarkers and HRCT indicate that exposure to hardly soluble indium compound dust may represent a risk for interstitial lung damage.
Mortality from Alzheimer's, motor neuron and Parkinson's disease in relation to magnetic field exposure: findings from the study of UK electricity generation and transmission workers, 1973–2004
Authors: Sorahan T , Kheifets L 
Published: July 2007

Background:There are a number of reports linking magnetic field exposure to increased risks of Alzheimer's disease and motor neuron disease.Methods:The mortality experienced by a cohort of 83 997 employees of the former Central Electricity Generating Board of England and Wales was investigated for the period 1973–2004. All employees were employed for at least six months with some employment in the period 1973–82. Computerised work histories were available for 79 972 study subjects for the period 1971–93. Information on job and facility (location) were used to estimate exposures to magnetic fields. Two analytical approaches were used to evaluate risks, indirect standardisation (n = 83 997) and Poisson regression (n = 79 972).Results:Based on serial mortality rates for England and Wales, deaths from Alzheimer's disease and motor neuron disease were unexceptional. There was an excess of deaths from Parkinson's disease of borderline significance. No statistically significant trends were shown for risks of any of these diseases to increase with lifetime cumulative exposure to magnetic fields (RR per 10 μT-y: Alzheimer's disease 1.10 (95% CI 0.90 to 1.33); motor neuron disease 1.06 (95% CI 0.86 to 1.32); Parkinson's disease 0.88 (95% CI 0.74 to 1.05))Conclusions:There is no convincing evidence that UK electricity generation and transmission workers have suffered increased risks from neurodegenerative diseases as a consequence of exposure to magnetic fields.