bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Membrane-Destabilizing Peptide in Capsid Protein L2 Is Required for Egress of Papillomavirus Genomes from Endosomes
Authors: Kämper Nadine , Day Patricia M. , Nowak Thorsten , Selinka Hans-Christoph , Florin Luise , Bolscher Jan , Hilbig Lydia , Schiller John T. , Sapp Martin 
Published: December 2005

ABSTRACT
Papillomaviruses are internalized via clathrin-dependent endocytosis. However, the mechanism by which viral genomes pass endosomal membranes has not been elucidated. In this report we show that the minor capsid protein L2 is required for egress of viral genomes from endosomes but not for initial uptake and uncoating and that a 23-amino-acid peptide at the C terminus of L2 is necessary for this function. Pseudogenomes encapsidated by L1 and L2 lacking this peptide accumulated in vesicular compartments similar to that observed with L1-only viral particles, and these mutant pseudoviruses were noninfectious. This L2 peptide displayed strong membrane-disrupting activity, induced cytolysis of bacteria and eukaryotic cells in a pH-dependent manner, and permeabilized cells after exogenous addition. Fusions between green fluorescent protein and the L2 peptide integrated into cellular membranes like the wild type but not like C-terminal mutants of L2. Our data indicate that the L2 C terminus facilitates escape of viral genomes from the endocytic compartment and that this feature is conserved among papillomaviruses. Furthermore, the characteristic of this peptide differs from the classical virus-encoded membrane-penetrating peptides.
UL54
-Null Pseudorabies Virus Is Attenuated in Mice but Productively Infects Cells in Culture
Authors: Schwartz Jennifer A. , Brittle Elizabeth E. , Reynolds Ashley E. , Enquist Lynn W. , Silverstein Saul J. 
Published: December 2005

ABSTRACT

The pseudorabies virus (PRV) UL54 homologs are important multifunctional proteins with roles in shutoff of host protein synthesis, transactivation of virus and cellular genes, and regulation of splicing and translation. Here we describe the first genetic characterization of UL54. We constructed
UL54
null mutations in a PRV bacterial artificial chromosome using sugar suicide and λRed allele exchange systems. Surprisingly, UL54 is dispensable for growth in tissue culture but exhibits a small-plaque phenotype that can be complemented in
trans
by both the herpes simplex virus type 1 ICP27 and varicella-zoster virus open reading frame 4 proteins. Deletion of
UL54
in the virus vJSΔ54 had no effect on the ability of the virus to shut off host cell protein synthesis but did affect virus gene expression. The glycoprotein gC accumulated to lower levels in cells infected with vJSΔ54 compared to those infected with wild-type virus, while gK levels were undetectable. Other late gene products, gB, gE, and Us9, accumulated to higher levels than those seen in cells infected with wild-type virus in a multiplicity-dependent manner. DNA replication is also reduced in cells infected with vJSΔ54. UL54 appears to regulate
UL53
and
UL52
at the transcriptional level as their respective RNAs are decreased in cells infected with vJSΔ54. Interestingly, vJSΔ54 is highly attenuated in a mouse model of PRV infection. Animals infected with vJSΔ54 survive twice as long as animals infected with wild-type virus, and this results in delayed accumulation of virus-specific antigens in skin, dorsal root ganglia, and spinal cord tissues.
7a Protein of Severe Acute Respiratory Syndrome Coronavirus Inhibits Cellular Protein Synthesis and Activates p38 Mitogen-Activated Protein Kinase
Authors: Kopecky-Bromberg Sarah A. , Martinez-Sobrido Luis , Palese Peter 
Published: December 2005

ABSTRACT
It was recently shown that the 7a protein of severe acute respiratory syndrome coronavirus induces biochemical changes associated with apoptosis. In this study, the mechanism by which the 7a protein induces apoptosis was examined. The 7a protein was tested for the ability to inhibit cellular gene expression because several proapoptotic viral proteins with this function have previously been identified. 7a protein inhibited expression of luciferase from an mRNA construct that specifically measures translation, whereas inhibitors of transcription and nucleocytoplasmic transport did not. The inhibition of translation and other cellular processes of gene expression have been associated with the induction of a stress response in cells. Western blot analysis using phosphospecific antibodies indicated that 7a protein activated p38 mitogen-activated protein kinase (MAPK), but not c-Jun N-terminal protein kinase/stress-activated protein kinase. Taken together, these data indicate that the induction of apoptosis by the 7a protein may be related to its ability to inhibit cellular translation and activate p38 MAPK.
Involvement of Template-Activating Factor I/SET in Transcription of Adenovirus Early Genes as a Positive-Acting Factor
Authors: Haruki Hirohito , Okuwaki Mitsuru , Miyagishi Makoto , Taira Kazunari , Nagata Kyosuke 
Published: December 2005

ABSTRACT
The adenovirus genome complexed with viral core protein VII (adenovirus DNA-protein VII complex) at least is the bona fide template for transcription of adenovirus early genes. It is believed that the highly basic protein VII, like cellular histones, is a negative regulator for genome functions. Analyses with in vitro replication and transcription systems using the adenovirus DNA-protein VII complex have revealed that remodeling of the complex is crucial for efficient DNA replication and transcription. We identified host acidic proteins, template-activating factor I (TAF-I), TAF-II, and TAF-III as stimulatory factors for replication from the adenovirus DNA-protein VII complex. Recently, it was reported that the adenovirus DNA interacts with TAF-I and pp32, another host acidic protein (Y. Xue, J. S. Johnson, D. A. Ornelles, J. Lieberman, and D. A. Engel, J. Virol. 79:2474-2483, 2005). We found that TAF-I interacts and colocalizes with protein VII in adenovirus-infected cells during the early phases of infection, but pp32 does not. Although pp32 had the potential ability to interact with protein VII, pp32 did not remodel the adenovirus DNA-protein VII complex in vitro. Small interfering RNA-mediated knockdown of TAF-I expression leads to the delay of the transcription timing of early genes. These results provide evidence that TAF-I plays an important role in the early stages of the adenovirus infection cycle.
Naïve and Memory Cell Turnover as Drivers of CCR5-to-CXCR4 Tropism Switch in Human Immunodeficiency Virus Type 1: Implications for Therapy
Authors: Ribeiro Ruy M. , Hazenberg Mette D. , Perelson Alan S. , Davenport Miles P. 
Published: December 2005

ABSTRACTEarly human immunodeficiency virus infection is characterized by the predominance of CCR5-tropic (R5) virus. However, in many individuals CXCR4-tropic (X4) virus appears in late infection. The reasons for this phenotypic switch are unclear. The patterns of chemokine receptor expression suggest that X4 and R5 viruses have a preferential tropism for naïve and memory T cells, respectively. Since memory cells divide approximately 10 times as often as naïve cells in uninfected individuals, a tropism for memory cells in early infection may provide an advantage. However, with disease progression both naïve and memory cell division frequencies increase, and at low CD4 counts, the naïve cell division frequency approaches that of memory cells. This may provide a basis for the phenotypic switch from R5 to X4 virus observed in late infection. We show that a model of infection using observed values for cell turnover supports this mechanism. The phenotypic switch from R5 to X4 virus occurs at low CD4 counts and is accompanied by a rapid rise in viral load and drop in CD4 count. Thus, low CD4 counts are both a cause and an effect of X4 virus dominance. We also investigate the effects of different antiviral strategies. Surprisingly, these results suggest that both conventional antiretroviral regimens and CCR5 receptor-blocking drugs will promote R5 virus over X4 virus.
Impact of Capsid Conformation and Rep-Capsid Interactions on Adeno-Associated Virus Type 2 Genome Packaging
Authors: Bleker Svenja , Pawlita Michael , Kleinschmidt Jürgen A. 
Published: December 2005

ABSTRACT

Single-stranded genomes of adeno-associated virus (AAV) are packaged into preformed capsids. It has been proposed that packaging is initiated by interaction of genome-bound Rep proteins to the capsid, thereby targeting the genome to the portal of encapsidation. Here we describe a panel of mutants with amino acid exchanges in the pores at the fivefold axes of symmetry on AAV2 capsids with reduced packaging and reduced Rep-capsid interaction. Mutation of two threonines at the rim of the fivefold pore nearly completely abolished Rep-capsid interaction and packaging. This suggests a Rep-binding site at the highly conserved amino acids at or close to the pores formed by the capsid protein pentamers. A different mutant (P. Wu, W. Xiao, T. Conlon, J. Hughes, M. Agbandje-McKenna, T. Ferkol, T. Flotte, and N. Muzyczka, J. Virol.
74:
8635-8647, 2000) with an amino acid exchange at the interface of capsid protein pentamers led to a complete block of DNA encapsidation. Analysis of the capsid conformation of this mutant revealed that the pores at the fivefold axes were occupied by VP1/VP2 N termini, thereby preventing DNA introduction into the capsid. Nevertheless, the corresponding capsids had more Rep proteins bound than wild-type AAV, showing that correct Rep interaction with the capsid depends on a defined capsid conformation. Both mutant types together support the conclusion that the pores at the fivefold symmetry axes are involved in genome packaging and that capsid conformation-dependent Rep-capsid interactions play an essential role in the packaging process.
Mutations on the External Surfaces of Adeno-AssociatedVirus Type 2 Capsids That Affect Transduction andNeutralization
Authors: Lochrie Michael A. , Tatsuno Gwen P. , Christie Brian , McDonnell Jennifer Wellman , Zhou Shangzhen , Surosky Richard , Pierce Glenn F. , Colosi Peter 
Published: December 2005

ABSTRACT
Mutations
were made at 64 positions on the external surface of the
adeno-associated virus type 2 (AAV-2) capsid in regions expected to
bind antibodies. The 127 mutations included 57 single alanine
substitutions, 41 single nonalanine substitutions, 27 multiple
mutations, and 2 insertions. Mutants were assayed for capsid synthesis,
heparin binding, in vitro transduction, and binding and neutralization
by murine monoclonal and human polyclonal antibodies. All mutants made
capsid proteins within a level about 20-fold of that made by the wild
type. All but seven mutants bound heparin as well as the wild type.
Forty-two mutants transduced human cells at least as well as the wild
type, and 10 mutants increased transducing activity up to ninefold more
than the wild type. Eighteen adjacent alanine substitutions diminished
transduction from 10- to 100,000-fold but had no effect on heparin
binding and define an area (dead zone) required for transduction that
is distinct from the previously characterized heparin receptor binding
site. Mutations that reduced binding and neutralization by a murine
monoclonal antibody (A20) were localized, while mutations that reduced
neutralization by individual human sera or by pooled human, intravenous
immunoglobulin G (IVIG) were dispersed over a larger area. Mutations
that reduced binding by A20 also reduced neutralization. However, a
mutation that reduced the binding of IVIG by 90% did not reduce
neutralization, and mutations that reduced neutralization by IVIG did
not reduce its binding. Combinations of mutations did not significantly
increase transduction or resistance to neutralization by IVIG. These
mutations define areas on the surface of the AAV-2 capsid that are
important determinants of transduction and antibody
neutralization.
Neutralization Escape Variants of Human Immunodeficiency Virus Type 1 Are Transmitted from Mother to Infant
Authors: Wu Xueling , Parast Adam B. , Richardson Barbra A. , Nduati Ruth , John-Stewart Grace , Mbori-Ngacha Dorothy , Rainwater Stephanie M. J. , Overbaugh Julie 
Published: December 2005

ABSTRACT
Maternal passive immunity typically plays a critical role in protecting infants from new infections; however, the specific contribution of neutralizing antibodies in limiting mother-to-child transmission of human immunodeficiency virus type 1 is unclear. By examining cloned envelope variants from 12 transmission pairs, we found that vertically transmitted variants were more resistant to neutralization by maternal plasma than were maternal viral variants near the time of transmission. The vertically transmitted envelope variants were poorly neutralized by monoclonal antibodies biz, 2G12, 2F5, and 4E10 individually or in combination. Despite the fact that the infant viruses were among the most neutralization resistant in the mother, they had relatively few glycosylation sites. Moreover, the transmitted variants elicited de novo neutralizing antibodies in the infants, indicating that they were not inherently difficult to neutralize. The neutralization resistance of vertically transmitted viruses is in contrast to the relative neutralization sensitivity of viruses sexually transmitted within discordant couples, suggesting that the antigenic properties of viruses that are favored for transmission may differ depending upon mode of transmission.
Epstein-Barr Virus (EBV) Genome and Expression in Breast Cancer Tissue: Effect of EBV Infection of Breast Cancer Cells on Resistance to Paclitaxel (Taxol)
Authors: Arbach Hratch , Viglasky Viktor , Lefeu Florence , Guinebretière Jean-Marc , Ramirez Vanessa , Bride Nadège , Boualaga Nadia , Bauchet Thomas , Peyrat Jean-Philippe , Mathieu Marie-Christine , Mourah Samia , Podgorniak Marie-Pierre , Seignerin Jean-Marie , Takada Kenzo , Joab Irène 
Published: December 2005

ABSTRACT
The Epstein-Barr virus (EBV) has been detected in subsets of breast cancers. In order to elaborate on these observations, we quantified by real-time PCR (Q-PCR) the EBV genome in biopsy specimens of breast cancer tissue as well as in tumor cells isolated by microdissection. Our findings show that EBV genomes can be detected by Q-PCR in about half of tumor specimens, usually in low copy numbers. However, we also found that the viral load is highly variable from tumor to tumor. Moreover, EBV genomes are heterogeneously distributed in morphologically identical tumor cells, with some clusters of isolated tumor cells containing relatively high genome numbers while other tumor cells isolated from the same specimen may be negative for EBV DNA. Using reverse transcription-PCR, we detected EBV gene transcripts: EBNA-1 in almost all of the EBV-positive tumors and RNA of the EBV oncoprotein LMP-1 in a smaller subset of the tissues analyzed. Moreover, BARF-1 RNA was detected in half of the cases studied. Furthermore, we observed that in vitro EBV infection of breast carcinoma cells confers resistance to paclitaxel (taxol) and provokes overexpression of a multidrug resistance gene (MDR1). Consequently, even if a small number of breast cancer cells are EBV infected, the impact of EBV infection on the efficiency of anticancer treatment might be of importance.
R5 Variants of Human Immunodeficiency Virus Type 1 Preferentially Infect CD62L−CD4+T Cells and Are Potentially Resistant to Nucleoside Reverse Transcriptase Inhibitors
Authors: Gondois-Rey Françoise , Biancotto Angelique , Fernandez Marcelo Antonio , Bettendroffer Lise , Blazkova Jana , Trejbalova Katerina , Pion Marjorie , Hirsch Ivan 
Published: December 2005

ABSTRACTThe persistence of human immunodeficiency virus type 1 (HIV-1) in memory CD4+T cells is a major obstacle to the eradication of the virus with current antiretroviral therapy. Here, we investigated the effect of the activation status of CD4+T cells on the predominance of R5 and X4 HIV-1 variants in different subsets of CD4+T cells in ex vivo-infected human lymphoid tissues and peripheral blood mononuclear cells (PBMCs). In these cell systems, we examined the sensitivity of HIV replication to reverse transcriptase inhibitors. We demonstrate that R5 HIV-1 variants preferentially produced productive infection in HLA-DR−CD62L−CD4+T cells. These cells were mostly in the G1b phase of the cell cycle, divided slowly, and expressed high levels of CCR5. In contrast, X4 HIV-1 variants preferentially produced productive infection in activated HLA-DR+CD62L+CD4+T cells, which expressed high levels of CXCR4. The abilities of the nucleoside reverse transcriptase inhibitors (NRTI) zidovudine and lamivudine to stop HIV-1 replication were 20 times greater in activated T cells than in slowly dividing HLA-DR−CD62L−CD4+T cells. This result, demonstrated both in a highly physiologically relevant ex vivo lymphoid tissue model and in PBMCs, correlated with higher levels of thymidine kinase mRNA in activated than in slowly dividing HLA-DR−CD62L−CD4+T cells. The non-NRTI nevirapine was equally efficient in both cell subsets. The lymphoid tissue and PBMC-derived cell systems represent well-defined models which could be used as new tools for the study of the mechanism of resistance to HIV-1 inhibitors in HLA-DR−CD62L−CD4+T cells.
Hepatitis C Virus Induces Toll-Like Receptor 4 Expression, Leading to Enhanced Production of Beta Interferon and Interleukin-6
Authors: Machida Keigo , Cheng Kevin T. H. , Sung Vicky M.-H. , Levine Alexandra M. , Foung Steven , Lai Michael M. C. 
Published: December 2005

ABSTRACT
Hepatitis C virus (HCV) induces inflammatory signals, leading to hepatitis, hepatocellular carcinomas, and lymphomas. The mechanism of HCV involvement in the host's innate immune responses has not been well characterized. In this study, we analyzed expression and regulation of the entire panel of toll-like receptors (TLRs) in human B cells following HCV infection in vitro. Among all of the TLRs (TLRs 1 to 10) examined, only TLR4 showed an altered expression (a three- to sevenfold up-regulation) after HCV infection. Peripheral blood mononuclear cells from HCV-infected individuals also showed a higher expression level of TLR4 compared with those of healthy individuals. HCV infection significantly increased beta interferon (IFN-β) and interleukin-6 (IL-6) secretion from B cells, particularly after lipopolysaccharide stimulation. The increased IFN-β and IL-6 production was mediated by TLR4 induction, since the introduction of the small interfering RNA against TLR4 specifically inhibited the HCV-induced cytokine production. Among all of the viral proteins, only NS5A caused TLR4 induction in hepatocytes and B cells. NS5A specifically activated the promoter of the TLR4 gene in both hepatocytes and B cells. In conclusion, HCV infection directly induces TLR4 expression and thereby activates B cells, which may contribute to the host's innate immune responses.
Uracil DNA Glycosylase Is Dispensable for Human Immunodeficiency Virus Type 1 Replication and Does Not Contribute to the Antiviral Effects of the Cytidine Deaminase Apobec3G
Authors: Kaiser Shari M. , Emerman Michael 
Published: December 2005

ABSTRACT

It is well established that many host factors are involved in the replication of human immunodeficiency virus (HIV) type 1. One host protein, uracil DNA glycosylase 2 (UNG2), binds to multiple viral proteins and is packaged into HIV type 1 virions. UNG initiates the removal of uracils from DNA, and this has been proposed to be important both for reverse transcription and as a mediator to the antiviral effect of virion-incorporated Apobec3G, a cytidine deaminase that generates numerous uracils in the viral DNA during virus replication. We used a natural human
UNG
−
/
−
cell line as well as cells that express a potent catalytic active-site inhibitor of UNG to assess the effects of removing UNG activity on HIV infectivity. In both cases, we find UNG2 activity and protein to be completely dispensable for virus replication. Moreover, we find that virion-associated UNG2 does not affect the loss of infectivity caused by Apobec3G.
Three Immunoproteasome-Associated Subunits Cooperatively Generate a Cytotoxic T-Lymphocyte Epitope of Epstein-Barr Virus LMP2A by Overcoming Specific Structures Resistant to Epitope Liberation
Authors: Ito Yoshinori , Kondo Eisei , Demachi-Okamura Ayako , Akatsuka Yoshiki , Tsujimura Kunio , Tanimoto Mitsune , Morishima Yasuo , Takahashi Toshitada , Kuzushima Kiyotaka 
Published: December 2005

ABSTRACTThe precise roles of gamma interferon-inducible immunoproteasome-associated molecules in generation of cytotoxic T-lymphocyte (CTL) epitopes have yet to be fully elucidated. We describe here a unique epitope derived from the Epstein-Barr virus (EBV) latent membrane protein 2A (LMP2A) presented by HLA-A*2402 molecules. Generation of the epitope, designated LMP2A222-230, from the full-length protein requires the immunoproteasome subunit low-molecular-weight protein 7 (ip-LMP7) and the proteasome activator 28-α subunit and is accelerated by ip-LMP2, as revealed by gene expression experiments using an LMP2A222-230-specific CTL clone as a responder in enzyme-linked immunospot assays. The unequivocal involvement of all three components was confirmed by RNA interference gene silencing. Interestingly, the LMP2A222-230epitope could be efficiently generated from incomplete EBV-LMP2A fragments that were produced by puromycin treatment or gene-engineered shortened EBV-LMP2A lacking some of its hydrophobic domains. In addition, epitope generation was increased by a single amino acid substitution from leucine to alanine immediately flanking the C terminus, this being predicted by a web-accessible program to increase the cleavage strength. Taken together, the data indicate that the generation of LMP2A222-230is influenced not only by extrinsic factors such as immunoproteasomes but also by intrinsic factors such as the length of the EBV-LMP2A protein and proteasomal cleavage strength at specific positions in the source antigen.