bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kaposi's Sarcoma-Associated Herpesvirus
ori-Lyt
-Dependent DNA Replication: DualRole of Replication and Transcription Activator
Authors: Wang Yan , Tang Qiyi , Maul Gerd G. , Yuan Yan 
Published: November 2006

ABSTRACT

Lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) is
essential for viral propagation and pathogenicity. In Kaposi's sarcoma
lesions, constant lytic replication plays a role in sustaining the
population of latently infected cells that otherwise are quickly lost
by segregation of latent viral episomes as spindle cells divide. Lytic
DNA replication initiates from an origin (
ori-Lyt
) and
requires
trans
-acting elements. Two functional
ori-Lyt
s have been identified in the KSHV genome.
Some
cis
-acting and
trans
-acting elements for
ori-Lyt
-dependent DNA replication have been found. Among
these, K8 binding sites, a cluster of C/EBP binding motifs, and a
replication and transcription activator (RTA) responsive element (RRE)
are crucial
cis
-acting elements. Binding of K8 and RTA
proteins to these motifs in
ori-Lyt
DNA was demonstrated to be
absolutely essential for DNA replication. In the present study,
functional roles of RTA in
ori-Lyt
-dependent DNA replication
have been investigated. Two distinct functions of RTA were revealed.
First, RTA activates an
ori-Lyt
promoter and initiates
transcription across GC-rich tandem repeats. This RTA-mediated
transcription is indispensable for DNA replication. Second, RTA is a
component of the replication compartment, where RTA interacts with
prereplication complexes composed of at least six core machinery
proteins and K8. The prereplication complexes are recruited to
ori-Lyt
DNA through RTA, which interacts with the RRE, as well
as K8, which binds to a cluster of C/EBP binding motifs with the aid of
C/EBP α. The revelation of these two functions of RTA, together
with its role in initiation of a transcriptional cascade that leads to
transcription of all viral lytic genes, shows that RTA is a critical
initiator and regulator of KSHV lytic DNA replication and viral
propagation.
Identification of an Essential Domain in the Herpesvirus VP1/2 Tegument Protein: the Carboxy Terminus Directs Incorporation into Capsid Assemblons
Authors: Lee Joy I-Hsuan , Luxton G. W. Gant , Smith Gregory Allan 
Published: November 2006

ABSTRACT
The herpesvirus tegument is a layer of viral and cellular proteins located between the capsid and envelope of the virion. The VP1/2 tegument protein is critical for the propagation of all herpesviruses examined. Using an infectious clone of the alphaherpesvirus pseudorabies virus, we have made a collection of truncation and in-frame deletion mutations within the VP1/2 gene (UL36) and examined the resulting viruses for spread between cells. We found that the majority of the VP1/2 protein either was essential for virus propagation or did not tolerate large deletions. A recently described amino-terminal deubiquitinase-encoding domain was dispensable for alphaherpesvirus propagation, but the rate of propagation in an epithelial cell line and the frequency of transport in axons of primary sensory neurons were both reduced. We mapped one essential domain to a conserved sequence at the VP1/2 carboxy terminus and demonstrated that this domain sufficient to redirect the green fluorescent protein to capsid assemblons in nuclei of infected cells.
Rotavirus Infection Enhances Lipopolysaccharide-Induced Intussusception in a Mouse Model
Authors: Warfield Kelly L. , Blutt Sarah E. , Crawford Sue E. , Kang Gagandeep , Conner Margaret E. 
Published: November 2006

ABSTRACTUnexpected reports of intussusception after vaccination with the live tetravalent rotavirus vaccine RotaShield resulted in voluntary withdrawal of the vaccine. Intussusception, a condition in which the intestine acutely invaginates upon itself, is the most common cause of intestinal obstruction in children. We report here the development of a mouse model to study rotavirus-induced intussusception. In this model, both homologous murine and heterologous simian rotavirus strains significantly enhanced the rate of lipopolysaccharide (LPS)-induced intussusception, and this enhancement was replication dependent, requiring rotavirus doses of greater than one 50% infectious dose. Rotavirus-induced intussusceptions did not have observable lymphoid lead points, despite the induction of intestinal lymphoid hyperplasia after rotavirus infection. Intussusceptions are also postulated to result from altered intestinal motility, but rotavirus infection had no effect on gastrointestinal transit. LPS-induced intussusception is associated with the induction of inflammatory mediators, and intussusception rates can be modified by inflammatory antagonists. We show that rotavirus infection significantly enhanced serum tumor necrosis factor alpha and gamma interferon cytokine levels after LPS treatment compared to uninfected mice. Together, these data suggest that rotavirus infection sensitized mice to the inflammatory effects of subsequent LPS treatment to enhance intussusception rates.
Divergences in Protein Activity and Cellular Localization within theCampoletis sonorensisIchnovirus Vankyrin Family
Authors: Kroemer Jeremy A. , Webb Bruce A. 
Published: November 2006

ABSTRACTIchnoviruses (IVs) occur in obligate symbiotic associations with endoparasitic ichneumonid wasps. IVs are injected with eggs during parasitization, where viral infection and gene expression alter host physiology to ensure endoparasitoid survival. The sevenCampoletis sonorensisIV (CsIV)vankyringenes encode proteins that possess ankyrin repeat domains resembling the inhibitory domains of NF-κB transcription factor inhibitors (IκBs). The CsIVvankyrinsare divided into two subclasses: those expressed primarily in the host fat body (three genes) and those expressed in host hemocytes (four genes). CsIV vankyrin proteins showed limited antigenic similarity when analyzed by Western blotting. Cellular localization and expression patterns of recombinant vankyrin proteins in High Five and Sf9 insect cells differed within and between the subclasses and in cells exposed to lipopolysaccharide, laminarin, or viral immune challenge. In unstimulated Sf9 cells, five vankyrins were detected in cell nuclei. The remaining two proteins localized predominantly to cytoplasmic granules. Immune stimulation of cells resulted in a nuclear-to-cytoplasmic shift of three vankyrins but did not affect localization of other variants. When expressed from recombinantAutographa californicamultiple nucleopolyhedroviruses (AcMNPVs), all vankyrins showed a nuclear localization during early stages of infection with patterns resembling those of immune-challenged cells as the infection progressed. Two fat body vankyrins also produced unique biological effects when expressed from recombinant AcMNPV. Insect cells infected with these viruses exhibited enhanced longevity compared to those infected with viruses expressing other vankyrins. Together, these data suggest that vankyrin proteins in CsIV have divergent physiological functions.
Characterization of a Novel 5′ Subgenomic RNA3a Derived from RNA3 of Brome Mosaic Bromovirus
Authors: Wierzchoslawski Rafal , Urbanowicz Anna , Dzianott Aleksandra , Figlerowicz Marek , Bujarski Jozef J. 
Published: November 2006

ABSTRACT
The synthesis of 3′ subgenomic RNA4 (sgRNA4) by initiation from an internal sg promoter in the RNA3 segment was first described for Brome mosaic bromovirus (BMV), a model tripartite positive-sense RNA virus (W. A. Miller, T. W. Dreher, and T. C. Hall, Nature 313:68-70, 1985). In this work, we describe a novel 5′ sgRNA of BMV (sgRNA3a) that we propose arises by premature internal termination and that encapsidates in BMV virions. Cloning and sequencing revealed that, unlike any other BMV RNA segment, sgRNA3a carries a 3′ oligo(A) tail, in which respect it resembles cellular mRNAs. Indeed, both the accumulation of sgRNA3a in polysomes and the synthesis of movement protein 3a in in vitro systems suggest active functions of sgRNA3a during protein synthesis. Moreover, when copied in the BMV replicase in vitro reaction, the minus-strand RNA3 template generated the sgRNA3a product, likely by premature termination at the minus-strand oligo(U) tract. Deletion of the oligo(A) tract in BMV RNA3 inhibited synthesis of sgRNA3a during infection. We propose a model in which the synthesis of RNA3 is terminated prematurely near the sg promoter. The discovery of 5′ sgRNA3a sheds new light on strategies viruses can use to separate replication from the translation functions of their genomic RNAs.
Functional Characterization of Kaposi's Sarcoma-Associated Herpesvirus ORF45 byBacterial Artificial Chromosome-Based Mutagenesis
Authors: Zhu Fan Xiu , Li Xiaojuan , Zhou Fuchun , Gao Shou-Jiang , Yuan Yan 
Published: November 2006

ABSTRACT

Open
reading frame 45 (ORF45) of Kaposi's sarcoma-associated herpesvirus
(KSHV) encodes an immediate-early protein. This protein is also present
in virions as a tegument protein. ORF45 protein interacts with
interferon regulatory factor 7 (IRF-7) and inhibits virus-induced type
I interferon production by blocking activation of IRF-7. To define
further the function of ORF45 and the mechanism underlying its action,
we constructed an ORF45-null recombinant virus genome (BAC-stop45) by
using a bacterial artificial chromosome (BAC) system. Stable 293T cells
carrying the BAC36 (wild type) and BAC-stop45 genomes were generated.
When monolayers of 293T BAC36 and 293T BAC-stop45 cells were induced
with 12-
O
-tetradecanoylphorbol-13-acetate and sodium butyrate,
no significant difference was found between them in overall viral gene
expression and lytic DNA replication, but induced 293T BAC-stop45 cells
released 10-fold fewer virions to the medium than did 293T BAC36 cells.
When ORF45-null virus was used to infect cells, lower infectivity was
observed than for wild-type BAC36. These results suggest that KSHV
ORF45 plays roles in both early and late stages of viral infection,
probably in viral ingress and
egress.
The African Swine Fever Virus Nonstructural Protein pB602L Is Required for Formation of the Icosahedral Capsid of the Virus Particle
Authors: Epifano Carolina , Krijnse-Locker Jacomine , Salas María L. , Rodríguez Javier M. , Salas José 
Published: November 2006

ABSTRACT
African swine fever virus (ASFV) protein pB602L has been described as a molecular chaperone for the correct folding of the major capsid protein p72. We have studied the function of protein pB602L during the viral assembly process by using a recombinant ASFV, vB602Li, which inducibly expresses the gene coding for this protein. We show that protein pB602L is a late nonstructural protein, which, in contrast with protein p72, is excluded from the viral factory. Repression of protein pB602L synthesis inhibits the proteolytic processing of the two viral polyproteins pp220 and pp62 and leads to a decrease in the levels of protein p72 and a delocalization of the capsid protein pE120R. As shown by electron microscopy analysis of cells infected with the recombinant virus vB602Li, the viral assembly process is severely altered in the absence of protein pB602L, with the generation of aberrant “zipper-like” structures instead of icosahedral virus particles. These “zipper-like” structures are similar to those found in cells infected under restrictive conditions with the recombinant virus vA72 inducibly expressing protein p72. Immunoelectron microscopy studies show that the abnormal forms generated in the absence of protein pB602L contain the inner envelope protein p17 and the two polyproteins but lack the capsid proteins p72 and pE120R. These findings indicate that protein pB602L is essential for the assembly of the icosahedral capsid of the virus particle.
Adenovirus Fiber Shaft Contains a Trimerization Element That Supports Peptide Fusion for Targeted Gene Delivery
Authors: Li Jiali , Lad Sonya , Yang Guang , Luo Yunping , Iacobelli-Martinez Milena , Primus F. James , Reisfeld Ralph A. , Li Erguang 
Published: November 2006

ABSTRACTAdenoviral (Ad) vectors have been widely used in human gene therapy clinical trials. However, their application has frequently been restricted by the unfavorable expression of cell surface receptors critical for Ad infection. Infections by Ad2 and Ad5 are largely regulated by the elongated fiber protein that mediates its attachment to a cell surface receptor, coxsackie and adenovirus receptor (CAR). The fiber protein is a homotrimer consisting of an N-terminal tail, a long shaft, and a C-terminal knob region that is responsible for high-affinity receptor binding and Ad tropism. Consequently, the modification of the knob region, including peptide insertion and C-terminal fusion of ligands for cell surface receptors, has become a major research focus for targeting gene delivery. Such manipulation tends to disrupt fiber assembly since the knob region contains a stabilization element for fiber trimerization. We report here the identification of a novel trimerization element in the Ad fiber shaft. We demonstrate that fiber fragments containing the N-terminal tail and shaft repeats formed stable trimers that assembled onto Ad virions independently of the knob region. This fiber shaft trimerization element (FSTE) exhibited a capacity to support peptide fusion. We showed that Ad, modified with a chimeric protein by direct fusion of the FSTE with a growth factor ligand or a single-chain antibody, delivered a reporter gene selectively. Together, these results indicate that the shaft region of Ad fiber protein contains a trimerization element that allows ligand fusion, which potentially broadens the basis for Ad vector development.
Epstein-Barr Virus Selectively Deregulates DNA Damage Responses in Normal B Cells but Has No Detectable Effect on Regulation of the Tumor Suppressor p53
Authors: O'Nions Jenny , Turner Abigail , Craig Richard , Allday Martin J. 
Published: November 2006

ABSTRACT

To determine whether latent Epstein-Barr virus (EBV) modifies DNA damage responses in B lymphocytes, cells were treated with agents either producing DNA cross-links and adducts or generating double-strand breaks. The cyclin-dependent kinase inhibitor p21
WAF1
accumulated in mitogen-stimulated primary B cells following exposure to all genotoxins tested. In contrast, when proliferation was EBV driven, p21
WAF1
failed to accumulate after treatment with the DNA adduct-producing agents. The tumor suppressor p53 was stabilized and phosphorylated after all treatments, irrespective of whether latent EBV was present. This suggests that regulatory pathways upstream of p53 are unaffected by latent EBV but downstream effectors are altered if DNA adducts or distortions are involved.
A New Group B Adenovirus Receptor Is Expressed at High Levels on Human Stem and Tumor Cells
Authors: Tuve Sebastian , Wang Hongjie , Ware Carol , Liu Ying , Gaggar Anuj , Bernt Kathrin , Shayakhmetov Dmitry , Li ZongYi , Strauss Robert , Stone Daniel , Lieber André 
Published: November 2006

ABSTRACT

CD46
is used by human group B adenoviruses (Ads) as a high-affinity
attachment receptor. Here we show evidence that several group B Ads
utilize an additional receptor for infection of human cells, which is
different from CD46. We tentatively named this receptor receptor X.
Competition studies with unlabeled and labeled Ads, recombinant Ad
fiber knobs, and soluble CD46 and CD46 antibodies revealed three
different subgroups of group B Ads, in terms of their receptor usage.
Group I (Ad16, -21, -35, and -50) nearly exclusively uses CD46. Group
II (Ad3, -7p, and -14) utilizes receptor X and not CD46. Group III
(Ad11p) uses both CD46 and the alternative receptor X. Interaction of
group II and III Ads with receptor X occurs via the fiber knob.
Receptor X is an abundantly expressed glycoprotein that interacts with
group II and III Ads at relatively low affinity in a
Ca
2+
-dependent manner. This receptor is expressed at
high levels on human mesenchymal and undifferentiated embryonic stem
cells, as well as on human cancer cell lines. These findings have
practical implications for stem cell and gene
therapy.
Rotavirus Nonstructural Glycoprotein NSP4 Is Secreted from the Apical Surfaces of Polarized Epithelial Cells
Authors: Bugarc̀ić Andrea , Taylor John A. 
Published: November 2006

ABSTRACT
NSP4, a nonstructural glycoprotein encoded by rotavirus, is involved in the morphogenesis of virus particles in the endoplasmic reticulum of infected cells. NSP4 is also implicated in the pathophysiology of rotavirus-induced diarrhea by acting as an enterotoxin. To mediate enterotoxic effects in vivo, NSP4 must be secreted or released from rotavirus-infected cells in a soluble form; however, previous studies have indicated that NSP4 is a transmembrane glycoprotein localized within endomembrane compartments in infected cells. In this study, we examined the fate of NSP4 synthesized in Caco-2 cells infected with bovine rotavirus. Our studies reveal that NSP4 is actively secreted into the culture medium, preferentially from the infected-cell apical surface. The secretion of NSP4 is dramatically inhibited by brefeldin A and monensin, suggesting that a Golgi-dependent pathway is involved in release of the protein. In agreement with the proposed involvement of the Golgi apparatus during secretion, secreted NSP4 appears to undergo additional posttranslational modification compared to its cell-associated counterpart and is partially resistant to deglycosylation by endoglycosidase H. Our experiments identify a novel, soluble form of NSP4 secreted from virus-infected cells with the potential to carry out the enterotoxigenic role previously attributed to recombinant forms of the protein.
Gene Structure and Expression of Kaposi's Sarcoma-Associated Herpesvirus ORF56, ORF57, ORF58, and ORF59
Authors: Majerciak Vladimir , Yamanegi Koji , Zheng Zhi-Ming 
Published: November 2006

ABSTRACT

Though similar to those of herpesvirus saimiri and Epstein-Barr virus (EBV), the Kaposi's sarcoma-associated herpesvirus (KSHV) genome features more splice genes and encodes many genes with bicistronic or polycistronic transcripts. In the present study, the gene structure and expression of KSHV ORF56 (primase), ORF57 (MTA), ORF58 (EBV BMRF2 homologue), and ORF59 (DNA polymerase processivity factor) were analyzed in butyrate-activated KSHV
+
JSC-1 cells. ORF56 was expressed at low abundance as a bicistronic ORF56/57 transcript that utilized the same intron, with two alternative branch points, as ORF57 for its RNA splicing. ORF56 was transcribed from two transcription start sites, nucleotides (nt) 78994 (minor) and 79075 (major), but selected the same poly(A) signal as ORF57 for RNA polyadenylation. The majority of ORF56 and ORF57 transcripts were cleaved at nt 83628, although other nearby cleavage sites were selectable. On the opposite strand of the viral genome, colinear ORF58 and ORF59 were transcribed from different transcription start sites, nt 95821 (major) or 95824 (minor) for ORF58 and nt 96790 (minor) or 96794 (major) for ORF59, but shared overlapping poly(A) signals at nt 94492 and 94488. Two cleavage sites, at nt 94477 and nt 94469, could be equally selected for ORF59 polyadenylation, but only the cleavage site at nt 94469 could be selected for ORF58 polyadenylation without disrupting the ORF58 stop codon immediately upstream. ORF58 was expressed in low abundance as a monocistronic transcript, with a long 5′ untranslated region (UTR) but a short 3′ UTR, whereas ORF59 was expressed in high abundance as a bicistronic transcript, with a short 5′ UTR and a long 3′ UTR similar to those of polycistronic ORF60 and ORF62. Both ORF56 and ORF59 are targets of ORF57 and were up-regulated significantly in the presence of ORF57, a posttranscriptional regulator.
Walleye Dermal Sarcoma Virus Retroviral Cyclin Directly Contacts TAF9
Authors: Rovnak Joel , Quackenbush Sandra L. 
Published: November 2006

ABSTRACT
Walleye dermal sarcoma virus (WDSV) is a complex retrovirus associated with dermal sarcomas in walleye fish. A WDSV accessory gene encodes a cyclin homolog or retroviral cyclin (rv-cyclin). WDSV rv-cyclin was found to be associated with transcription complexes and to affect transcription in a cell-type and promoter-dependent manner. It inhibited the WDSV promoter in walleye fibroblasts and activated transcription from GAL4 promoters when fused to the GAL4 DNA binding domain, and an activation domain (AD) has been localized to 30 amino acids in the carboxyl region. rv-cyclin can block the pulldown of transcription coactivators by the AD of VP16, and the isolated rv-cyclin AD interferes specifically with the interaction between the carboxyl halves of the VP16 AD, VP16C, and TATA-binding protein-associated factor 9 (TAF9). The carboxyl region and isolated AD can bind TAF9 directly in assays of protein-protein interaction in vitro. Furthermore, rv-cyclin and the isolated rv-cyclin AD interfere specifically with the function of VP16C in transcription assays. A previously identified motif within the VP16C sequence mediates TAF9 binding, and this motif is present in the activation domains of a variety of TAF9-binding transcriptional activators. A similar motif is present in the rv-cyclin AD, and point mutations within this motif affect rv-cyclin function and protein-protein interactions. The results support a model of transcription regulation by direct interaction with TAF9.
Conformational Changes in the VP1-Unique Region of Native Human Parvovirus B19 Lead to Exposure of Internal Sequences That Play a Role in Virus Neutralization and Infectivity
Authors: Ros Carlos , Gerber Marco , Kempf Christoph 
Published: November 2006

ABSTRACT

The unique region of the capsid protein VP1 (VP1u) of human parvovirus B19 (B19) elicits a dominant immune response and has a phospholipase A
2
(PLA
2
) activity, which is necessary for the infection. In contrast to the rest of the parvoviruses, the VP1u of B19 is thought to occupy an external position in the virion, making this region a promising candidate for vaccine development. By using a monoclonal antibody against the most-N-terminal portion of VP1u, we revealed that this region rich in neutralizing epitopes is not accessible in native capsids. However, exposure of capsids to increasing temperatures or low pH led to its progressive accessibility without particle disassembly. Although unable to bind free virus or to block virus attachment to the cell, the anti-VP1u antibody was neutralizing, suggesting that the exposure of the epitope and the subsequent virus neutralization occur only after receptor attachment. The measurement of the VP1u-associated PLA
2
activity of B19 capsids revealed that this region is also internal but becomes exposed in heat- and in low-pH-treated particles. In sharp contrast to native virions, the VP1u of baculovirus-derived B19 capsids was readily accessible in the absence of any treatment. These results indicate that stretches of VP1u of native B19 capsids harboring neutralizing epitopes and essential functional motifs are not external to the capsid. However, a conformational change renders these regions accessible and triggers the PLA
2
potential of the virus. The results also emphasize major differences in the VP1u conformation between natural and recombinant particles.