bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell-Free Human Immunodeficiency Virus Type 1 Transcytosis through Primary Genital Epithelial Cells
Authors: Bobardt Michael D. , Chatterji Udayan , Selvarajah Suganya , Van der Schueren Bernadette , David Guido , Kahn Bruce , Gallay Philippe A. 
Published: December 2006

ABSTRACT
Although the transport of human immunodeficiency virus type 1 (HIV-1) through the epithelium is critical for HIV-1 colonization, the mechanisms controlling this process remain obscure. In the present study, we investigated the transcellular migration of HIV-1 as a cell-free virus through primary genital epithelial cells (PGECs). The absence of CD4 on PGECs implicates an unusual entry pathway for HIV-1. We found that syndecans are abundantly expressed on PGECs and promote the initial attachment and subsequent entry of HIV-1 through PGECs. Although CXCR4 and CCR5 do not contribute to HIV-1 attachment, they enhance viral entry and transcytosis through PGECs. Importantly, HIV-1 exploits both syndecans and chemokine receptors to ensure successful cell-free transport through the genital epithelium. HIV-1-syndecan interactions rely on specific residues in the V3 of gp120 and specific sulfations within syndecans. We found no obvious correlation between coreceptor usage and the capacity of the virus to transcytose. Since viruses isolated after sexual transmission are mainly R5 viruses, this suggests that the properties conferring virus replication after transmission are distinct from those conferring cell-free virus transcytosis through the genital epithelium. Although we found that cell-free HIV-1 crosses PGECs as infectious particles, the efficiency of transcytosis is extremely poor (less than 0.02% of the initial inoculum). This demonstrates that the genital epithelium serves as a major barrier against HIV-1. Although one cannot exclude the possibility that limited passage of cell-free HIV-1 transcytosis through an intact genital epithelium occurs in vivo, it is likely that the establishment of infection via cell-free HIV-1 transmigration is a rare event.
M-T5, the Ankyrin Repeat, Host Range Protein of Myxoma Virus, Activates Akt and Can Be Functionally Replaced by Cellular PIKE-A
Authors: Werden Steven J. , Barrett John W. , Wang Gen , Stanford Marianne M. , McFadden Grant 
Published: December 2006

ABSTRACT

The myxoma virus (MV) ankyrin repeat, host range factor M-T5 has the ability to bind and activate cellular Akt, leading to permissive MV replication in a variety of diverse human cancer cell lines (G. Wang, J. W. Barrett, M. Stanford, S. J. Werden, J. B. Johnston, X. Gao, M. Sun, J. Q. Cheng, and G. McFadden, Proc. Natl. Acad. Sci. USA
103:
4640-4645, 2006). The susceptibility of permissive human cancer cells to MV infection is directly correlated with the basal or induced levels of phosphorylated Akt. When M-T5 is deleted from MV, the knockout virus, vMyxT5KO, can no longer productively infect a subset of human cancer cells (designated type II) that exhibit little or no endogenous phosphorylated Akt. In searching for a host counterpart of M-T5, we noted sequence similarity of M-T5 to a recently identified ankyrin repeat cellular binding protein of Akt called PIKE-A. PIKE-A binds and activates the kinase activity of Akt in a GTP-dependent manner and promotes the invasiveness of human cancer cell lines. Here, we demonstrate that transfected PIKE-A is able to rescue the ability of vMyxT5KO to productively infect type II human cancer cells that were previously resistant to infection. Also, cancer cells that were completely nonpermissive for both wild-type and vMyxT5KO infection (called type III) were rendered fully permissive following ectopic expression of PIKE-A. We conclude that the MV M-T5 host range protein is functionally interchangeable with the host PIKE-A protein and that the activation of host Akt by either M-T5 or PIKE-A is critical for the permissiveness of human cancer cells for MV.
Early Resolution of Herpes Simplex Virus Type 2 Infection of the Murine Genital Tract Involves Stimulation of Genital Parenchymal Cells by Gamma Interferon
Authors: Bird Melanie D. , Chu Chin-Fun , Johnson Alison J. , Milligan Gregg N. 
Published: December 2006

ABSTRACTEarly clearance of a thymidine kinase-deficient strain of herpes simplex virus type 2 from the female genital tract required T-cell-produced gamma interferon (IFN-γ). Transfer of activated CD8+T cells to irradiated C57BL/6 mice resulted in rapid virus clearance, but clearance was greatly delayed in recipients deficient in the IFN-γ receptor (IFN-γR). Early virus clearance was demonstrated in radiation chimeras in which IFN-γR expression was limited to parenchymal cells, but resolution was significantly delayed in chimeras deficient in IFN-γR expression and chimeras expressing IFN-γR only on hematopoietic cells. Together, these results suggest that early IFN-γ-mediated protection was manifested mainly by stimulation of genital parenchymal cells.
In Vivo Packaging of Brome Mosaic Virus RNA3, but Not RNAs 1 and 2, Is Dependent on a
cis
-Acting 3′ tRNA-Like Structure
Authors: Annamalai Padmanaban , Rao A. L. N. 
Published: December 2006

ABSTRACT

The four encapsidated RNAs of brome mosaic virus (BMV; B1, B2, B3, and B4) contain a highly conserved 3′ 200-nucleotide (nt) region encompassing the tRNA-like structure (TLS) which is required for packaging in vitro (Y. G. Choi, T. W. Dreher, and A. L. N. Rao, Proc. Natl. Acad. Sci. USA 99:655-660, 2002). To validate these observations in vivo, we performed packaging assays using
Agrobacterium-
mediated transient expression of RNAs and coat protein (CP) (P. Annamalai and A. L. N. Rao, Virology 338:96-111, 2005). Coexpression of TLS-less constructs of B1 or B2 or B3 and CP mRNAs in
Nicotiana benthamiana
leaves resulted in packaging of TLS-less B1 and B2 but not B3, suggesting that packaging of B3 requires the TLS in
cis
. This conjecture was confirmed by the efficient packaging of a B3 chimera in which the viral TLS was replaced with a cellular tRNA
Tyr
. When
N. benthamiana
leaves were infiltrated with a mixture of transformants containing wild-type B1 (wtB1) plus wtB2 plus a TLS-less B3 (wtB1+wtB2+TLS-lessB3), the 3′ end of progeny B3 was restored by heterologous recombination with that of either B1 or B2. This intrinsic
cis-
requirement of TLS in promoting B3 packaging was further confirmed when a mixture containing agrotransformants of TLS-less B1+B2+B3 was supplemented with either wtB4 or a 3′ 200-nt or 3′ 336-nt untranslated region (UTR) of B3. Northern blot analysis followed by sequencing of B3 progeny revealed that replication of TLS-less B3, but not TLS-less B1 or B2, was fully restored due to recombination with TLS from transiently expressed wtB4 or the B3 3′ UTR. Collectively, these observations suggested that the requirement of a
cis
-acting TLS is distinct for B3 compared with B1 or B2.
Structural and Mutagenic Analysis of Foot-and-Mouth Disease Virus 3C Protease Reveals the Role of the β-Ribbon in Proteolysis
Authors: Sweeney Trevor R. , Roqué-Rosell Núria , Birtley James R. , Leatherbarrow Robin J. , Curry Stephen 
Published: December 2006

ABSTRACT

The 3C protease (3C
pro
) from foot-and-mouth disease virus (FMDV), the causative agent of a widespread and economically devastating disease of domestic livestock, is a potential target for antiviral drug design. We have determined the structure of a new crystal form of FMDV 3C
pro
, a chymotrypsin-like cysteine protease, which reveals features that are important for catalytic activity. In particular, we show that a surface loop which was disordered in previous structures adopts a β-ribbon structure that is conformationally similar to equivalent regions on other picornaviral 3C proteases and some serine proteases. This β-ribbon folds over the peptide binding cleft and clearly contributes to substrate recognition. Replacement of Cys142 at the tip of the β-ribbon with different amino acids has a significant impact on enzyme activity and shows that higher activity is obtained with more hydrophobic side chains. Comparison of the structure of FMDV 3C
pro
with homologous enzyme-peptide complexes suggests that this correlation arises because the side chain of Cys142 contacts the hydrophobic portions of the P2 and P4 residues in the peptide substrate. Collectively, these findings provide compelling evidence for the role of the β-ribbon in catalytic activity and provide valuable insights for the design of FMDV 3C
pro
inhibitors.
Virus-Induced Decline in Soluble Vascular Endothelial Growth Receptor 2 Is Associated with Plasma Leakage in Dengue Hemorrhagic Fever
Authors: Srikiatkhachorn Anon , Ajariyakhajorn Chuanpis , Endy Timothy P. , Kalayanarooj Siripen , Libraty Daniel H. , Green Sharone , Ennis Francis A. , Rothman Alan L. 
Published: December 2006

ABSTRACTSome individuals infected with dengue virus develop dengue hemorrhagic fever (DHF), a viral hemorrhagic disease characterized by a transient period of localized plasma leakage. To determine the importance of vascular endothelial growth factor A (VEGF-A) in this syndrome, we compared plasma levels of VEGF-A and the soluble forms of its receptors in patients with DHF to patients with dengue fever (DF), a milder form of dengue virus infection without plasma leakage. We observed a rise in the plasma levels of free, but not total VEGF-A in DHF patients at the time of plasma leakage. This was associated with a decline in the soluble form of VEGF receptor 2 (VEGFR2) and VEGF-soluble VEGFR2 complexes, but not the soluble form of VEGFR1. The severity of plasma leakage in patients inversely correlated with plasma levels of soluble VEGFR2. In vitro, dengue virus suppressed soluble VEGFR2 production by endothelial cells but up-regulated surface VEGFR2 expression and promoted response to VEGF stimulation. In vivo, plasma viral load correlated with the degree of decline in plasma soluble VEGFR2. These results suggest that VEGF regulates vascular permeability and its activity is controlled by binding to soluble VEGFR2. Dengue virus-induced changes in surface and soluble VEGFR2 expression may be an important mechanism of plasma leakage in DHF.
Interaction of Papillomavirus E2 Protein with the Brm Chromatin Remodeling Complex Leads to Enhanced Transcriptional Activation
Authors: Ajay Kumar R. , Naidu Samisubbu R. , Wang Xiaoyu , Imbalzano Anthony N. , Androphy Elliot J. 
Published: December 2006

ABSTRACT
Papillomavirus E2 is a sequence-specific DNA binding protein that regulates transcription and replication of the viral genome. The transcriptional activities of E2 are typically evaluated by transient transfection of nonreplicating E2-dependent reporters. We sought to address whether E2 activates transcription in an episomal context and its potential interaction with the chromatin remodeling proteins. Using an Epstein-Barr virus-based episomal reporter, we demonstrate that E2 stimulates transcription from an E2-dependent promoter in a chromatin context. This activation is enhanced by the presence of proteins associated with SWI/SNF complexes, which are ATP-dependent chromatin remodeling enzymes. We show that exogenous expression of the Brm ATPase enhances E2 activity in SWI/SNF-deficient cell lines and that the amino-terminal transactivation domain of E2 mediates association with the Brm complex in vivo. Using chromatin immunoprecipitation assays, we demonstrate that Brm enhances promoter occupancy by E2 in an episomal context. Our results demonstrate that E2 activates transcription from an episomal reporter system and reveal a novel property of E2 in collaborating with the Brm chromatin remodeling complex in enhancing transcriptional activation.
Disseminated Simian Varicella Virus Infection in an Irradiated Rhesus Macaque (
Macaca mulatta
)
Authors: Kolappaswamy Krishnan , Mahalingam Ravi , Traina-Dorge Vicki , Shipley Steven T. , Gilden Donald H. , Kleinschmidt-Demasters Bette K. , McLeod Charles G. , Hungerford Laura L. , DeTolla Louis J. 
Published: December 2006

ABSTRACT
We describe correlative clinicopathological/virological findings from a simian varicella virus (SVV)-seronegative monkey that developed disseminated varicella 105 days after gamma-irradiation. Twelve other monkeys in the colony were also irradiated, none of which developed varicella. Before irradiation, sera from the monkey that developed disseminated infection and one asymptomatic monkey were available. Analysis indicated that subclinical reactivation of latent SVV from an asymptomatic irradiated monkey likely led to disseminated varicella in the seronegative irradiated monkey. These findings parallel those from humans with disseminated varicella infection and support the usefulness of SVV infection as a model for human varicella-zoster virus infection, particularly virus reactivation after gamma-irradiation.
Antiviral Peptides Targeting the West Nile Virus Envelope Protein
Authors: Bai Fengwei , Town Terrence , Pradhan Deepti , Cox Jonathan , Ashish  , Ledizet Michel , Anderson John F. , Flavell Richard A. , Krueger Joanna K. , Koski Raymond A. , Fikrig Erol 
Published: December 2006

ABSTRACT
West Nile virus (WNV) can cause fatal murine and human encephalitis. The viral envelope protein interacts with host cells. A murine brain cDNA phage display library was therefore probed with WNV envelope protein, resulting in the identification of several adherent peptides. Of these, peptide 1 prevented WNV infection in vitro with a 50% inhibition concentration of 67 μM and also inhibited infection of a related flavivirus, dengue virus. Peptide 9, a derivative of peptide 1, was a particularly potent inhibitor of WNV in vitro, with a 50% inhibition concentration of 2.6 μM. Moreover, mice challenged with WNV that had been incubated with peptide 9 had reduced viremia and fatality compared with control animals. Peptide 9 penetrated the murine blood-brain barrier and was found in the brain parenchyma, implying that it may have antiviral activity in the central nervous system. These short peptides serve as the basis for developing new therapeutics for West Nile encephalitis and, potentially, other flaviviruses.
Hepatitis B Virus X Protein Induces Perinuclear Mitochondrial Clustering in Microtubule- and Dynein-Dependent Manners
Authors: Kim Sujeong , Kim Hye-Young , Lee Seungmin , Kim Sung Woo , Sohn Seonghyang , Kim Kyongmin , Cho Hyeseong 
Published: December 2006

ABSTRACTThe hepatitis B virus (HBV) X protein (HBx) is thought to play a key role in HBV replication and the development of liver cancer. It became apparent that HBx induces mitochondrial clustering at the nuclear periphery, but the molecular basis for mitochondrial clustering is not understood. Since mitochondria move along the cytoskeleton as a cargo of motor proteins, we hypothesized that mitochondrial clustering induced by HBx occurs by an altered intracellular motility. Here, we demonstrated that the treatment of HBx-expressing cells with a microtubule-disrupting drug (nocodazole) abrogated mitochondrial clustering, while the removal of nocodazole restored clustering within 30 to 60 min, indicating that mitochondrial transport is occurring in a microtubule-dependent manner. The addition of a cytochalasin D-disrupting actin filament, however, did not measurably affect mitochondrial clustering. Mitochondrial clustering was further studied by observations of HBV-related hepatoma cells and HBV-replicating cells. Importantly, the abrogation of the dynein activity in HBx-expressing cells by microinjection of a neutralizing anti-dynein intermediate-chain antibody, dynamitin overexpression, or the addition of a dynein ATPase inhibitor significantly suppressed the mitochondrial clustering. In addition, HBx induced the activation of the p38 mitogen-activated protein kinase (MAPK) and inhibition of the p38 kinase activity by SB203580-attenuated HBx-induced mitochondrial clustering. Taken together, HBx activation of the p38 MAPK contributed to the increase in the microtubule-dependent dynein activity. The data suggest that HBx plays a novel regulatory role in subcellular transport systems, perhaps facilitating the process of maturation and/or assembly of progeny particles during HBV replication. Furthermore, mitochondrion aggregation induced by HBx may represent a cellular process that underlies disease progression during chronic viral infection.
Thiol/Disulfide Exchange Is Required for Membrane Fusion Directed by the Newcastle Disease Virus Fusion Protein
Authors: Jain Surbhi , McGinnes Lori W. , Morrison Trudy G. 
Published: December 2006

ABSTRACTNewcastle disease virus (NDV), an avian paramyxovirus, initiates infection with attachment of the viral hemagglutinin-neuraminidase (HN) protein to sialic acid-containing receptors, followed by fusion of viral and cell membranes, which is mediated by the fusion (F) protein. Like all class 1 viral fusion proteins, the paramyxovirus F protein is thought to undergo dramatic conformational changes upon activation. How the F protein accomplishes extensive conformational rearrangements is unclear. Since several viral fusion proteins undergo disulfide bond rearrangement during entry, we asked if similar rearrangements occur in NDV proteins during entry. We found that inhibitors of cell surface thiol/disulfide isomerase activity—5′5-dithio-bis(2-nitrobenzoic acid) (DTNB), bacitracin, and anti-protein disulfide isomerase antibody—inhibited cell-cell fusion and virus entry but had no effect on cell viability, glycoprotein surface expression, or HN protein attachment or neuraminidase activities. These inhibitors altered the conformation of surface-expressed F protein, as detected by conformation-sensitive antibodies. Using biotin maleimide (MPB), a reagent that binds to free thiols, free thiols were detected on surface-expressed F protein, but not HN protein. The inhibitors DTNB and bacitracin blocked the detection of these free thiols. Furthermore, MPB binding inhibited cell-cell fusion. Taken together, our results suggest that one or several disulfide bonds in cell surface F protein are reduced by the protein disulfide isomerase family of isomerases and that F protein exists as a mixture of oxidized and reduced forms. In the presence of HN protein, only the reduced form may proceed to refold into additional intermediates, leading to the fusion of membranes.
Wild-Type Levels of Human Immunodeficiency Virus Type 1 Infectivity in the Absence of Cellular Emerin Protein
Authors: Shun Ming-Chieh , Daigle Janet E. , Vandegraaff Nick , Engelman Alan 
Published: December 2006

ABSTRACT
Preintegration complexes (PICs) mediate retroviral integration, and recent results indicate an important role for the inner nuclear membrane protein emerin in orienting human immunodeficiency virus type 1 (HIV-1) PICs to chromatin for integration. Two other host cell proteins, the barrier-to-autointegration factor (BAF) and lamina-associated polypeptide 2α (LAP2α), seemed to play a similar preintegrative role for Moloney murine leukemia virus (MMLV) in addition to HIV-1. In contrast, we determined efficient HIV-1 and MMLV infection of HeLa-P4 cells following potent down-regulation of emerin, BAF, or LAP2α protein by using short interfering RNA. Mouse embryo fibroblasts ablated for emerin protein through gene knockout support the same level of HIV-1 infection as cells derived from wild-type littermate control animals. As the expression of human emerin in mouse knockout cells fails to affect the level of infectivity achieved in its absence, we conclude that HIV-1 efficiently infects cells in the absence of emerin protein and, by extension, that emerin is not a universally important regulator of HIV-1 infectivity.
Participation of both Host and Virus Factors in Induction of Severe Acute Respiratory Syndrome (SARS) in F344 Rats Infected with SARS Coronavirus
Authors: Nagata Noriyo , Iwata Naoko , Hasegawa Hideki , Fukushi Shuetsu , Yokoyama Masaru , Harashima Ayako , Sato Yuko , Saijo Masayuki , Morikawa Shigeru , Sata Tetsutaro 
Published: December 2006

ABSTRACT
To understand the pathogenesis and develop an animal model of severe acute respiratory syndrome (SARS)-associated coronavirus (SARS-CoV), the Frankfurt 1 SARS-CoV isolate was passaged serially in young F344 rats. Young rats were susceptible to SARS-CoV but cleared the virus rapidly within 3 to 5 days of intranasal inoculation. After 10 serial passages, replication and virulence of SARS-CoV were increased in the respiratory tract of young rats without clinical signs. By contrast, adult rats infected with the passaged virus showed respiratory symptoms and severe pathological lesions in the lung. Levels of inflammatory cytokines in sera and lung tissues were significantly higher in adult F344 rats than in young rats. During in vivo passage of SARS-CoV, a single amino acid substitution was introduced within the binding domain of the viral spike protein recognizing angiotensin-converting enzyme 2 (ACE2), which is known as a SARS-CoV receptor. The rat-passaged virus more efficiently infected CHO cells expressing rat ACE2 than did the original isolate. These results strongly indicate that host and virus factors such as advanced age and virus adaptation are critical for the development of SARS in rats.
Mutations in the Central Domain of Potato Virus X TGBp2 Eliminate Granular Vesicles and Virus Cell-to-Cell Trafficking
Authors: Ju Ho-Jong , Brown James E. , Ye Chang-Ming , Verchot-Lubicz Jeanmarie 
Published: December 2006

ABSTRACT
Most RNA viruses remodel the endomembrane network to promote virus replication, maturation, or egress. Rearrangement of cellular membranes is a crucial component of viral pathogenesis. The PVX TGBp2 protein induces vesicles of the granular type to bud from the endoplasmic reticulum network. Green fluorescent protein (GFP) was fused to the PVX TGBp2 coding sequence and inserted into the viral genome and into pRTL2 plasmids to study protein subcellular targeting in the presence and absence of virus infection. Mutations were introduced into the central domain of TGBp2, which contains a stretch of conserved amino acids. Deletion of a 10-amino-acid segment (m2 mutation) overlapping the segment of conserved residues eliminated the granular vesicle and inhibited virus movement. GFP-TGBp2m2 proteins accumulated in enlarged vesicles. Substitution of individual conserved residues in the same region similarly inhibited virus movement and caused the mutant GFP-TGBp2 fusion proteins to accumulate in enlarged vesicles. These results identify a novel element in the PVX TGBp2 protein which determines vesicle morphology. In addition, the data indicate that vesicles of the granular type induced by TGBp2 are necessary for PVX plasmodesmata transport.
Adeno-Associated Virus Site-Specific Integration Is Regulated by TRP-185
Authors: Yamamoto Noriaki , Suzuki Masato , Kawano Masa-aki , Inoue Takamasa , Takahashi Ryou-u , Tsukamoto Hiroko , Enomoto Teruya , Yamaguchi Yuki , Wada Tadashi , Handa Hiroshi 
Published: December 2006

ABSTRACT

Adeno-associated virus (AAV) integrates site specifically into the AAVS1 locus on human chromosome 19. Although recruitment of the AAV nonstructural protein Rep78/68 to the
R
ep
b
inding
s
ite (RBS) on AAVS1 is thought to be an essential step, the mechanism of the site-specific integration, particularly, how the site of integration is determined, remains largely unknown. Here we describe the identification and characterization of a new cellular regulator of AAV site-specific integration.
T
AR
R
NA loop binding
p
rotein 185 (TRP-185), previously reported to associate with human immunodeficiency virus type 1 TAR RNA, binds to AAVS1 DNA. Our data suggest that TRP-185 suppresses AAV integration at the AAVS1 RBS and enhances AAV integration into a region downstream of the RBS. TRP-185 bound to Rep68 directly, changing the Rep68 DNA binding property and stimulating Rep68 helicase activity. We present a model in which TRP-185 changes the specificity of the AAV integration site from the RBS to a downstream region by acting as a molecular chaperone that promotes Rep68 complex formation competent for 3′→5′ DNA helicase activity.