bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Host Protein Staufen1 Participates in Human Immunodeficiency Virus Type 1 Assembly in Live Cells by Influencing pr55
Gag
Multimerization
Authors: Chatel-Chaix Laurent , Abrahamyan Levon , Fréchina Céline , Mouland Andrew J. , DesGroseillers Luc 
Published: April 2007

ABSTRACT

Human immunodeficiency virus type 1 (HIV-1) requires the sequential activities of virus-encoded proteins during replication. The activities of several host cell proteins and machineries are also critical to the completion of virus assembly and the release of infectious virus particles from cells. One of these proteins, the double-stranded RNA-binding protein Staufen1 (Stau1), selectively associates with the HIV-1 genomic RNA and the viral precursor Gag protein, pr55
Gag
. In this report, we tested whether Stau1 modulates pr55
Gag
assembly using a new and specific pr55
Gag
oligomerization assay based on bioluminescence resonance energy transfer (BRET) in both live cells and extracts after cell fractionation. Our results show that both the overexpression and knockdown of Stau1 increase the pr55
Gag
-pr55
Gag
BRET levels, suggesting a role for Stau1 in regulating pr55
Gag
oligomerization during assembly. This effect of Stau1 on pr55
Gag
oligomerization was observed only in membranes, a cellular compartment in which pr55
Gag
assembly primarily occurs. Consistently, expression of Stau1 harboring a vSrc myristylation signal led to a 6.5-fold enrichment of Stau1 in membranes and a corresponding enhancement in the Stau1-mediated effect on pr55
Gag
-pr55
Gag
BRET, demonstrating that Stau1 acts on assembly when targeted to membranes. A role for Stau1 in the formation of particles is further supported by the detection of membrane-associated detergent-resistant pr55
Gag
complexes and the increase of virus-like particle release when Stau1 expression levels are modulated. Our results indicate that Stau1 influences HIV-1 assembly by modulating pr55
Gag
-pr55
Gag
interactions, as shown in a live cell interaction assay. This likely occurs when Stau1 interacts with membrane-associated assembly intermediates.
U
S
3 of Herpes Simplex Virus Type 1 Encodes a Promiscuous Protein Kinase That Phosphorylates and Alters Localization of Lamin A/C in Infected Cells
Authors: Mou Fan , Forest Tom , Baines Joel D. 
Published: April 2007

ABSTRACT

The herpes simplex virus type 1 (HSV-1) U
S
3 gene encodes a serine/threonine kinase that, when inactivated, causes capsids to aggregate aberrantly between the inner and outer nuclear membranes (INM and ONM, respectively) within evaginations/extensions of the perinuclear space. In both Hep2 cells and an engineered cell line derived from Hep2 cells expressing lamin A/C fused to enhanced green fluorescent protein (eGFP-lamin A/C), lamin A/C localized mostly in a reticular pattern with small regions of the INM devoid of eGFP-lamin A/C when they were either mock infected or infected with wild-type HSV-1(F). Cells infected with HSV-1(F) also contained some larger diffuse regions lacking lamin A/C. Proteins U
L
31 and U
L
34, markers of potential envelopment sites at the INM and perinuclear virions, localized within the regions devoid of lamin A/C and also in regions containing lamin A/C. Similar to previous observations with Vero cells (S. L. Bjerke and R. J. Roller, Virology 347:261-276, 2006), the proteins U
L
34 and U
L
31 localized exclusively in very discrete regions of the nuclear lamina lacking lamin A/C in the absence of U
S
3 kinase activity. To determine how U
S
3 alters lamin A/C distribution, U
S
3 was purified and shown to phosphorylate lamin A/C at multiple sites in vitro, despite the presence of only one putative U
S
3 kinase consensus site in the lamin A/C sequence. U
S
3 kinase activity was also sufficient to invoke partial solubilization of lamin A/C from permeabilized Hep2 cell nuclei in an ATP-dependent manner. Two-dimensional electrophoretic analyses of lamin A/C revealed that lamin A/C is phosphorylated in HSV-infected cells, and the full spectrum of phosphorylation requires U
S
3 kinase activity. These data suggest that U
S
3 kinase activity regulates HSV-1 capsid nuclear egress at least in part by phosphorylation of lamin A/C.
Comparative Study of Methods for Detecting Sequence Compartmentalization in Human Immunodeficiency Virus Type 1
Authors: Zárate Selene , Pond Sergei L. Kosakovsky , Shapshak Paul , Frost Simon D. W. 
Published: April 2007

ABSTRACT
Human immunodeficiency virus (HIV) infects different organs and tissues. During these infection events, subpopulations of HIV type 1 (HIV-1) develop and, if viral trafficking is restricted between subpopulations, the viruses can follow independent evolutionary histories, i.e., become compartmentalized. This phenomenon is usually detected via comparative sequence analysis and has been reported for viruses isolated from the central nervous system (CNS) and the genital tract. Several approaches have been proposed to study the compartmentalization of HIV sequences, but to date, no rigorous comparison of the most commonly employed methods has been made. In this study, we systematically compared inferences made by six different methods for detecting compartmentalization based on three data sets: (i) a sample of 45 patients with sequences gathered from the CNS, (ii) sequences from the female genital tract of 18 patients, and (iii) a set of simulated sequences. We found that different methods often reached contradictory conclusions. Methods based on the topology of a phylogenetic tree derived from clonal sequences were generally more sensitive in detecting compartmentalization than those that relied solely upon pairwise genetic distances between sequences. However, as the branching structure in a phylogenetic tree is often uncertain, especially for short, low-diversity, or recombinant sequences, tree-based approaches may need to be modified to take phylogenetic uncertainty into account. Given the frequently discordant predictions of different methods and the strengths and weaknesses of each particular methodology, we recommend that a suite of several approaches be used for reliable inference of compartmentalized population structure.
A Borna Disease Virus Vector for Expression of Foreign Genes in Neurons of Rodents
Authors: Schneider Urs , Ackermann Andreas , Staeheli Peter 
Published: April 2007

ABSTRACT
An expression cassette for green fluorescent protein was successfully inserted at a site near the 5′ end of the genome of Borna disease virus (BDV). When introduced into a mutant virus with highly active polymerase, the foreign gene was strongly expressed in neurons of infected rats. Since BDV can establish long-term persistence in the central nervous system of rodents, it may be used to engineer efficient vectors for specific delivery of foreign genes into highly differentiated neurons.
The X Protein of Borna Disease Virus Serves Essential Functions in the Viral Multiplication Cycle
Authors: Poenisch Marion , Wille Sandra , Ackermann Andreas , Staeheli Peter , Schneider Urs 
Published: April 2007

ABSTRACT
The X gene of Borna disease virus (BDV) encodes a nonstructural 10-kDa protein that can interact with viral polymerase cofactor P, thus regulating polymerase activity. It remained unknown whether X is essential for virus multiplication. All our attempts to generate mutant BDV with a nonfunctional X gene proved unsuccessful. However, a mutant virus with an inactive X gene was able to replicate in Vero cells if an artificial gene cassette encoding X was inserted at a site near the 5′ end of the viral genome. These results indicate that X performs essential viral functions.
Human Immunodeficiency Virus Type 1 Variants Resistant to First- and Second-Version Fusion Inhibitors and Cytopathic in Ex Vivo Human Lymphoid Tissue
Authors: Chinnadurai Raghavan , Rajan Devi , Münch Jan , Kirchhoff Frank 
Published: April 2007

ABSTRACT

Human immunodeficiency virus type 1 (HIV-1) fusion inhibitors blocking viral entry by binding the gp41 heptad repeat 1 (HR1) region offer great promise for antiretroviral therapy, and the first of these inhibitors, T20 (Fuzeon; enfuvirtide), is successfully used in the clinic. It has been reported previously that changes in the 3-amino-acid GIV motif at positions 36 to 38 of gp41 HR1 mediate resistance to T20 but usually not to second-version fusion inhibitors, such as T1249, which target an overlapping but distinct region in HR1 including a conserved hydrophobic pocket (HP). Based on the common lack of cross-resistance and the difficulty of selecting T1249-resistant HIV-1 variants, it has been suggested that the determinants of resistance to first- and second-version fusion inhibitors may be different. To further assess HIV-1 resistance to fusion inhibitors and to analyze where changes in HR1 are tolerated, we randomized 16 codons in the HR1 region, including those making contact with HR2 codons and/or encoding residues in the GIV motif and the HP. We found that changes only at positions 37I, 38V, and 40Q near the N terminus of HR1 were tolerated. The propagation of randomly gp41-mutated HIV-1 variants in the presence of T1249 allowed the effective selection of highly resistant forms, all containing changes in the IV residues. Overall, the extent of T1249 resistance was inversely correlated to viral fitness and cytopathicity. Notably, one HIV-1 mutant showing ∼10-fold-reduced susceptibility to T1249 inhibition replicated with wild type-like kinetics and caused substantial CD4
+
-T-cell depletion in ex vivo-infected human lymphoid tissue in the presence and absence of an inhibitor. Taken together, our results show that the GIV motif also plays a key role in resistance to second-version fusion inhibitors and suggest that some resistant HIV-1 variants may be pathogenic in vivo.
Cytidine Deaminases APOBEC3G and APOBEC3F Interact with Human Immunodeficiency Virus Type 1 Integrase and Inhibit Proviral DNA Formation
Authors: Luo Kun , Wang Tao , Liu Bindong , Tian Chunjuan , Xiao Zuoxiang , Kappes John , Yu Xiao-Fang 
Published: April 2007

ABSTRACT
APOBEC3G (A3G) is a single-stranded DNA cytidine deaminase that targets retroviral minus-strand DNA and has potent antiviral activity against diverse retroviruses. However, the mechanisms of A3G antiviral functions are incompletely understood. Here we demonstrate that A3G, A3F, and, to a lesser extent, the noncatalytic A3GC291S block human immunodeficiency virus type 1 (HIV-1) replication by interfering with proviral DNA formation. In HIV-1 virions, A3G interacted with HIV-1 integrase and nucleocapsid, key viral factors for reverse transcription and integration. Unlike A3G, the weak antiviral A3C cytidine deaminase did not interact with either of these factors and did not affect viral reverse transcription or proviral DNA formation. Thus, multiple steps of the HIV-1 replication cycle, most noticeably the formation of proviral DNA, are inhibited by both cytidine deamination-dependent and -independent mechanisms.
Mutations in Human Immunodeficiency Virus Type 1 RNase H Primer Grip Enhance 3′-Azido-3′-Deoxythymidine Resistance
Authors: Delviks-Frankenberry Krista A. , Nikolenko Galina N. , Barr Rebekah , Pathak Vinay K. 
Published: April 2007

ABSTRACT
We recently observed that mutations in the human immunodeficiency type 1 (HIV-1) reverse transcriptase (RT) connection domain significantly increase 3′-azido-3′-deoxythymidine (AZT) resistance up to 536 times over wild-type (WT) RT in the presence of thymidine analog resistance mutations (TAMs). These mutations also decreased RT template switching, suggesting that they altered the balance between nucleotide excision and template RNA degradation, which in turn increased AZT resistance. Several residues in the HIV-1 connection domain contact the primer strand and form an RNase H primer grip structure that helps to position the primer-template at the RNase H and polymerase active sites. To test the hypothesis that connection domain mutations enhanced AZT resistance by influencing the RNase H primer grip, we determined the effects of alanine substitutions in RNase H primer grip residues on nucleoside RT inhibitor resistance in the context of a WT, TAM-containing, or K65R-containing polymerase domain. Ten of the 11 RNase H primer grip mutations increased AZT resistance 20 to 243 times above WT levels in the context of a TAM-containing polymerase domain. Furthermore, all mutations in the RNase H primer grip decreased template switching, suggesting that they reduced RNase H activity. These results demonstrate that mutations in the RNase H primer grip region can significantly enhance AZT resistance and support the hypothesis that mutations in the connection and RNase H domains can increase resistance by altering the RNase H primer grip region, changing interactions between RT and the template-primer complex and/or shifting the balance between the polymerase and RNase H activities.
VP3, a Structural Protein of Infectious Pancreatic Necrosis Virus, Interacts with RNA-Dependent RNA Polymerase VP1 and with Double-Stranded RNA
Authors: Pedersen Torunn , Skjesol Astrid , Jørgensen Jorunn B. 
Published: April 2007

ABSTRACT

Infectious pancreatic necrosis virus
(IPNV) is a bisegmented, double-stranded RNA (dsRNA) virus of the
Birnaviridae
family that causes widespread disease in salmonids. Its two genomic segments are encapsulated together with the viral RNA-dependent RNA polymerase, VP1, and the assumed internal protein, VP3, in a single-shell capsid composed of VP2. Major aspects of the molecular biology of IPNV, such as particle assembly and interference with host macromolecules, are as yet poorly understood. To understand the infection process, analysis of viral protein interactions is of crucial importance. In this study, we focus on the interaction properties of VP3, the suggested key organizer of particle assembly in birnaviruses. By applying the yeast two-hybrid system in combination with coimmunoprecipitation, VP3 was proven to bind to VP1 and to self-associate strongly. In addition, VP3 was shown to specifically bind to dsRNA in a sequence-independent manner by in vitro pull-down experiments. The binding between VP3 and VP1 was not dependent on the presence of dsRNA. Deletion analyses mapped the VP3 self-interaction domain within the 101 N-terminal amino acids and the VP1 interaction domain within the 62 C-terminal amino acids of VP3. The C-terminal end was also crucial but not sufficient for the dsRNA binding capacity of VP3. For VP1, the 90 C-terminal amino acids constituted the only dispensable part for maintaining VP3-binding ability. Kinetic analysis revealed the presence of VP1-VP3 complexes prior to the formation of mature virions in IPNV-infected CHSE-214 cells, which indicates a role in promoting the assembly process.
Inhibition of nuclear factor-κB augments antitumor activity of adenovirus-mediated melanoma differentiation-associated gene-7 against lung cancer cells via mitogen-activated protein kinase kinase kinase 1 activation
Authors: Oida Yasuhisa , Gopalan Began , Miyahara Ryo , Branch Cynthia D. , Chiao Paul , Chada Sunil , Ramesh Rajagopal 
Published: April 2007

Abstract
Nuclear factor-κB (NF-κB) activation promotes cell survival and growth. Reports show that chemotherapeutic agents and cytokines that are used for cancer therapy activate NF-κB expression in tumor cells and its suppression enhanced the antitumor activity. We hypothesized that adenovirus-mediated overexpression of melanoma differentiation-associated gene-7/interleukin-24 (Ad-mda7/IL-24) induces NF-κB expression and that inhibition of this expression results in enhanced tumor cell killing. Treatment of human lung tumor (H1299 and A549) cells with Ad-mda7 resulted in NF-κB activation in a dose- and time-dependent manner before activation of cell death pathways. To establish that inhibition of Ad-mda7–mediated NF-κB activation results in enhanced tumor cell killing, H1299 cells that overexpress the dominant-negative IκBα (dnIκBα) were treated with Ad-mda7 in vitro. An enhanced growth arrest and apoptosis was observed in Ad-mda7–treated H1299-dnIκBα compared with H1299-Neo cells. This Ad-mda7–mediated enhanced killing of H1299-dnIκBα cells involved cleavage of mitogen-activated protein kinase kinase kinase 1 (MEKK1) and caspase-3 in a feedback loop mechanism. The inhibition of MEKK1 or caspase-3 cleavage in H1299-dnIκBα cells resulted in reduced Ad-mda7–mediated cell killing. In vivo, the treatment of H1299-dnIκBα s.c. tumors with Ad-mda7 resulted in increased drug sensitivity and delayed the tumor growth rate compared with Ad-mda7–treated H1299-Neo tumors. Molecular analysis of Ad-mda7–treated H1299-dnIκBα tumors showed increased MEKK1 cleavage and activation of caspase-3 compared with Ad-mda7–treated H1299-Neo tumors. Our findings thus showed that the NF-κB activation induced by Ad-mda7 treatment of lung cancer cells is an intrinsic survival mechanism and that the inhibition of this NF-κB expression results in enhanced tumor cell killing. [Mol Cancer Ther 2007;6(4):1440–9]
Novel xenograft model expressing human hepatocyte growth factor shows ligand-dependent growth of c-Met–expressing tumors
Authors: Francone Todd D. , Landmann Ron G. , Chen Chin-Tung , Sun Mark Y. , Kuntz Eleanor J. , Zeng Zhaoshi , Dematteo Ronald P. , Paty Philip B. , Weiser Martin R. 
Published: April 2007

Abstract
c-Met, a receptor tyrosine kinase responsible for cellular migration, invasion, and proliferation, is overexpressed in human cancers. Although ligand-independent c-Met activation has been described, the majority of tumors are ligand dependent and rely on binding of hepatocyte growth factor (HGF) for receptor activation. Both receptor and ligand are attractive therapeutic targets; however, preclinical models are limited because murine HGF does not activate human c-Met. The goal of this study was to develop a xenograft model in which human HGF (hHGF) is produced in a controllable fashion in the mouse. Severe combined immunodeficient mice were treated with adenovirus encoding the hHGF transgene (Ad-hHGF) via tail vein injection, and transgene expression was determined by the presence of hHGF mRNA in mouse tissue and hHGF in serum. Ad-hHGF administration to severe combined immunodeficient mice resulted in hHGF production that was (a) dependent on quantity of virus delivered; (b) biologically active, resulting in liver hypertrophy; and (c) sustainable over 40 days. In this model, the ligand-dependent human tumor cell line SW1417 showed enhanced tumor growth, whereas the ligand-independent cell lines SW480 and GTL-16 showed no augmented tumor growth. This novel xenograft model is ideal for investigating c-Met/HGF–dependent human tumor progression and for evaluating c-Met targeted therapy. [Mol Cancer Ther 2007;6(4):1460–6]
Identification of a novel inhibitor of urokinase-type plasminogen activator
Authors: Zhu Ming , Gokhale Vijay M. , Szabo Lajos , Munoz Ruben M. , Baek Hyounggee , Bashyam Sridevi , Hurley Laurence H. , Von Hoff Daniel D. , Han Haiyong 
Published: April 2007

AbstractUrokinase-type plasminogen activator (uPA), a highly restricted serine protease, plays an important role in the regulation of diverse physiologic and pathologic processes. Strong clinical and experimental evidence has shown that elevated uPA expression is associated with cancer progression, metastasis, and shortened survival in patients. uPA has been considered as a promising molecular target for development of anticancer drugs. Here, we report the identification of several new uPA inhibitors using a high-throughput screen from a chemical library. From these uPA inhibitors, molecular modeling and docking studies identified 4-oxazolidinone as a novel lead pharmacophore. Optimization of the 4-oxazolidinone pharmacophore resulted in a series of structurally modified compounds with improved potency and selectivity. One of the 4-oxazolidinone analogues, UK122, showed the highest inhibition of uPA activity. The IC50 of UK122 in a cell-free indirect uPA assay is 0.2 μmol/L. This compound also showed no or little inhibition of other serine proteases such as thrombin, trypsin, plasmin, and the tissue-type plasminogen activator, indicating its high specificity against uPA. Moreover, UK122 showed little cytotoxicity against CFPAC-1 cells (IC50 &gt;100 μmol/L) but significantly inhibited the migration and invasion of this pancreatic cancer cell line. Our data show that UK122 could potentially be developed as a new anticancer agent that prevents the invasion and metastasis of pancreatic cancer. [Mol Cancer Ther 2007;6(4):1348–56]
Chemotherapeutic drugs sensitize cancer cells to TRAIL-mediated apoptosis: up-regulation of DR5 and inhibition of Yin Yang 1
Authors: Baritaki Stavroula , Huerta-Yepez Sara , Sakai Toshiyuki , Spandidos Demetrios A. , Bonavida Benjamin 
Published: April 2007

Abstract
Several chemotherapeutic drugs in combination with tumor necrosis factor–related apoptosis-inducing ligand (TRAIL) result in reversal of resistance to TRAIL-mediated apoptosis through up-regulation of DR5 expression. The promoter of DR5 has one putative binding site for the transcription repressor Yin Yang 1 (YY1), and thus, we hypothesized that the sensitizing drugs may inhibit YY1. We have found that treatment of tumor cells with various chemotherapeutic drugs inhibited nuclear factor-κB. We examined whether drugs also inhibit YY1 activity and whether YY1 inhibition correlates with up-regulation of DR5 expression and sensitization of cells to TRAIL-induced apoptosis. The TRAIL- and drug-resistant prostate carcinoma PC-3 cell line was treated with CDDP, VP-16, ADR, and vincristine. DR5 luciferase reporter constructs and small interfering RNA against YY1 were used to determine the role of YY1 in DR5 transcription. Pretreatment of PC-3 cells and other tumor cell lines with various chemotherapeutic drugs sensitized the cells to TRAIL-induced apoptosis concurrently with up-regulation of DR5 expression and inhibition of YY1 expression and its DNA-binding activity. The baseline luciferase activity in PC-3 cells transfected with the wild-type DR5 reporter was significantly augmented in cells transfected with DR5 constructs carrying deletions or mutation in the YY1-binding site. Treatment with drug enhanced DR5 wild-type luciferase activity, with no increase in cells transfected with the YY1-deleted or YY1-mutated constructs. Cells transfected with YY1 small interfering RNA showed up-regulation of DR5 expression and sensitization to TRAIL-mediated apoptosis. The findings provide evidence that drug-induced sensitization of tumor cells to TRAIL is mediated, in part, by inhibition of the transcription repressor YY1 and up-regulation of DR5 expression. Hence, YY1 may be a potential therapeutic target to reverse resistance to TRAIL-induced apoptosis. [Mol Cancer Ther 2007;6(4):1387–99]