bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Microtubules in Extracellular Release of Poliovirus
Authors: Taylor Matthew P. , Burgon Trever B. , Kirkegaard Karla , Jackson William T. 
Published: April 2009

ABSTRACT
Cellular autophagy, a process that directs cytosolic contents to the endosomal and lysosomal pathways via the formation of double-membraned vesicles, is a crucial aspect of innate immunity to many intracellular pathogens. However, evidence is accumulating that certain RNA viruses, such as poliovirus, subvert this pathway to facilitate viral growth. The autophagosome-like membranes induced during infection with wild-type poliovirus were found to be, unlike cellular autophagosomes, relatively immobile. Their mobility increased upon nocodazole treatment, arguing that vesicular tethering is microtubule dependent. In cells infected with a mutant virus that is defective in its interaction with the host cytoskeleton and secretory pathway, vesicle movement increased, indicating reduced tethering. In all cases, the release of tethering correlated with increased amounts of extracellular virus, which is consistent with the hypothesis that small amounts of cytosol and virus entrapped by double-membraned structures could be released via fusion with the plasma membrane. We propose that this extracellular delivery of cytoplasmic contents be termed autophagosome-mediated exit without lysis (AWOL). This pathway could explain the observed exit, in the apparent absence of cellular lysis, of other cytoplasmic macromolecular complexes, including infectious agents and complexes of aggregated proteins.
Integrase Interacts with Nucleoporin NUP153 To Mediate the Nuclear Import of Human Immunodeficiency Virus Type 1
Authors: Woodward Cora L. , Prakobwanakit Sarin , Mosessian Sherly , Chow Samson A. 
Published: April 2009

ABSTRACT
The ability to traverse an intact nuclear envelope and productively infect nondividing cells is a salient feature of human immunodeficiency virus type 1 (HIV-1) and other lentiviruses, but the viral factors and mechanism of nuclear entry have not been defined. HIV-1 integrase (IN) is implicated to play a role in the nuclear import of the virus, but the cellular pathway for IN trafficking and the role of IN in mediating the nuclear import of viral particles are unknown. Using a semipermeabilized cell assay, we observed that the nuclear import of IN was not the result of passive diffusion but occurred independently of cytosolic factors, metabolic energy, and the classical receptor-mediated, Ran-dependent import pathways. To determine if IN enters the nucleus by interacting with the nucleopore complex (NPC), we found that IN bound directly with the FxFG-rich C-terminal domain of nucleoporin 153 (NUP153C). When added in excess to the import assay, NUP153C inhibited the nuclear import of IN. Known binding partners of NUP153C competed with IN for binding with NUP153 and also inhibited the nuclear import of IN. In cultured cells, overexpression of NUP153C reduced the infectivity of an HIV-derived vector by interfering with the nuclear translocation of the viral cDNA. These results support a functional role for the IN-NUP153 interaction in HIV-1 replication and suggest that HIV-1 subviral particles gain access to the nucleus by interacting directly with the NPC via the binding of particle-associated IN to NUP153C.
Severe Acute Respiratory Syndrome Coronavirus Papain-Like Protease Ubiquitin-Like Domain and Catalytic Domain Regulate Antagonism of IRF3 and NF-κB Signaling
Authors: Frieman Matthew , Ratia Kiira , Johnston Robert E. , Mesecar Andrew D. , Baric Ralph S. 
Published: April 2009

ABSTRACTThe outcome of a viral infection is regulated in part by the complex coordination of viral and host interactions that compete for the control and optimization of virus replication. Severe acute respiratory syndrome coronavirus (SARS-CoV) intimately engages and regulates the host innate immune responses during infection. Using a novel interferon (IFN) antagonism screen, we show that the SARS-CoV proteome contains several replicase, structural, and accessory proteins that antagonize the IFN pathway. In this study, we focus on the SARS-CoV papain-like protease (PLP), which engages and antagonizes the IFN induction and NF-κB signaling pathways. PLP blocks these pathways by affecting activation of the important signaling proteins in each pathway, IRF3 and NF-κB. We also show that the ubiquitin-like domain of PLP is necessary for pathway antagonism but not sufficient by itself to block these pathways regardless of the enzymatic activity of the protease. The potential mechanism of PLP antagonism and its role in pathogenesis are discussed.
Dissecting the Functional Domains of a Nonenveloped Virus Membrane Penetration Peptide
Authors: Banerjee Manidipa , Khayat Reza , Walukiewicz Hanna E. , Odegard Amy L. , Schneemann Anette , Johnson John E. 
Published: April 2009

ABSTRACT
Recent studies have established that several nonenveloped viruses utilize virus-encoded lytic peptides for host membrane disruption. We investigated this mechanism with the “gamma” peptide of the insect virus Flock House virus (FHV). We demonstrate that the C terminus of gamma is essential for membrane disruption in vitro and the rescue of immature virus infectivity in vivo, and the amphipathic N terminus of gamma alone is not sufficient. We also show that deletion of the C-terminal domain disrupts icosahedral ordering of the amphipathic helices of gamma in the virus. Our results have broad implications for understanding membrane lysis during nonenveloped virus entry.
Identification of a Feline Leukemia Virus Variant That Can Use THTR1, FLVCR1, and FLVCR2 for Infection
Authors: Shalev Zvi , Duffy Simon P. , Adema Karen W. , Prasad Rati , Hussain Naveen , Willett Brian J. , Tailor Chetankumar S. 
Published: April 2009

ABSTRACTThe pathogenic subgroup C feline leukemia virus (FeLV-C) arises in infected cats as a result of mutations in the envelope (Env) of the subgroup A FeLV (FeLV-A). To better understand emergence of FeLV-C and potential FeLV intermediates that may arise, we characterized FeLV Env sequences from the primary FY981 FeLV isolate previously derived from an anemic cat. Here, we report the characterization of the novel FY981 FeLV Env that is highly related to FeLV-A Env but whose variable region A (VRA) receptor recognition sequence partially resembles the VRA sequence from the prototypical FeLV-C/Sarma Env. Pseudotype viruses bearing FY981 Env were capable of infecting feline, human, and guinea pig cells, suggestive of a subgroup C phenotype, but also infected porcine ST-IOWA cells that are normally resistant to FeLV-C and to FeLV-A. Analysis of the host receptor used by FY981 suggests that FY981 can use both the FeLV-C receptor FLVCR1 and the feline FeLV-A receptor THTR1 for infection. However, our results suggest that FY981 infection of ST-IOWA cells is not mediated by the porcine homologue of FLVCR1 and THTR1 but by an alternative receptor, which we have now identified as the FLVCR1-related protein FLVCR2. Together, our results suggest that FY981 FeLV uses FLVCR1, FLVCR2, and THTR1 as receptors. Our findings suggest the possibility that pathogenic FeLV-C arises in FeLV-infected cats through intermediates that are multitropic in their receptor use.
Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor 4 Targets MDM2 To Deregulate the p53 Tumor Suppressor Pathway
Authors: Lee Hye-Ra , Toth Zsolt , Shin Young C. , Lee Jong-Soo , Chang Heesoon , Gu Wei , Oh Tae-Kwang , Kim Myung Hee , Jung Jae U. 
Published: April 2009

ABSTRACT
Cells infected by viruses utilize interferon (IFN)-mediated and p53-mediated irreversible cell cycle arrest and apoptosis as part of the overall host surveillance mechanism to ultimately block viral replication and dissemination. Viruses, in turn, have evolved elaborate mechanisms to subvert IFN- and p53-mediated host innate immune responses. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes several viral IFN regulatory factors (vIRF1 to vIRF4) within a cluster of loci, their functions being primarily to inhibit host IFN-mediated innate immunity and deregulate p53-mediated cell growth control. Despite its significant homology and similar genomic location to other vIRFs, vIRF4 is distinctive, as it does not target and antagonize host IFN-mediated signal transduction. Here, we show that KSHV vIRF4 interacts with the murine double minute 2 (MDM2) E3 ubiquitin ligase, leading to the reduction of p53, a tumor suppressor, via proteasome-mediated degradation. The central region of vIRF4 is required for its interaction with MDM2, which led to the suppression of MDM2 autoubiquitination and, thereby, a dramatic increase in MDM2 stability. Consequently, vIRF4 expression markedly enhanced p53 ubiquitination and degradation, effectively suppressing p53-mediated apoptosis. These results indicate that KSHV vIRF4 targets and stabilizes the MDM2 E3 ubiquitin ligase to facilitate the proteasome-mediated degradation of p53, perhaps to circumvent host growth surveillance and facilitate viral replication in infected cells. Taken together, the indications are that the downregulation of p53-mediated cell growth control is a common characteristic of the four KSHV vIRFs and that p53 is indeed a key factor in the host's immune surveillance program against viral infections.
Vaccinia Virus E3 Suppresses Expression of Diverse Cytokines through Inhibition of the PKR, NF-κB, and IRF3 Pathways
Authors: Myskiw Chad , Arsenio Janilyn , van Bruggen Rebekah , Deschambault Yvon , Cao Jingxin 
Published: April 2009

ABSTRACT
The vaccinia virus double-stranded RNA binding protein E3 has been demonstrated to inhibit the expression of cytokines, including beta interferon (IFN-β) and tumor necrosis factor alpha (TNF-α). However, few details regarding the molecular mechanisms of this inhibition have been described. Using real-time PCR arrays, we found that E3 suppressed the induction of a diverse array of cytokines representing members of the IFN, interleukin (IL), TNF, and transforming growth factor cytokine families. We discovered that the factor(s) responsible for the induction of IL-6, TNF-α, and inhibin beta A (INHBA) was associated with the early and late phases of virus infection. In contrast, the factor(s) which regulates IFN-β induction was associated with the late phase of replication. We have found that expression of these cytokines can be induced by transfection of cells with RNA isolated from vaccinia virus-infected cells. Moreover, we provide evidence that E3 antagonizes both PKR-dependent and PKR-independent pathways to regulate cytokine expression. PKR-dependent activation of p38 and NF-κB was required for vaccinia virus-induced INHBA expression, whereas induction of TNF-α required only PKR-dependent NF-κB activation. In contrast, induction of IL-6 and IFN-β was largely PKR independent. IL-6 induction is regulated by NF-κB, while IFN-β induction is mediated by IFN-β promoter stimulator 1 and IFN regulatory factor 3/NF-κB. Collectively, these results indicate that E3 suppresses distinct but interlinked host signaling pathways to inhibit the expression of a diverse array of cytokines.
Modeling Subgenomic Hepatitis C Virus RNA Kinetics during Treatment with Alpha Interferon
Authors: Dahari Harel , Sainz Bruno , Perelson Alan S. , Uprichard Susan L. 
Published: April 2009

ABSTRACT
Although replicons have been used to demonstrate hepatitis C virus (HCV) inhibition by alpha interferon (IFN-α), the detailed inhibition kinetics required to mathematically model HCV RNA decline have been lacking. Therefore, we measured genotype 1b subgenomic replicon (sg1b) RNA levels under various IFN-α concentrations to assess the inhibition kinetics of intracellular HCV RNA. During nine days of IFN-α treatment, sg1b RNA decreased in a biphasic, dose-dependent manner. Using frequent measurements to dissect these phases during IFN-α treatments of 100 and 250 U/ml revealed that the first-phase sg1b RNA decline began ∼12 h posttreatment, continued for 2 to 4 days, and then exhibited a distinct flat or slower second phase. Based on these data, we developed a mathematical model of IFN-α-induced intracellular sg1b RNA decline, and we show that the mechanism(s) mediating IFN-α inhibition of HCV acts primarily by reducing sg1b RNA amplification, with an additional effect on HCV RNA stability/degradation detectable at a dose of 250 U/ml IFN-α. While the extremely slow or flat second phase of viral RNA inhibition observed in vitro, in which there is little or no cell death, supports the in vivo modeling prediction that the more profound second-phase decline observed in IFN-α-treated patients reflects immune-mediated death/loss of productively infected cells, the second-phase decline in viral RNA with a dose of 250 U/ml IFN-α suggests that a further inhibition of intracellular HCV RNA levels may contribute as well. As such, dissection of HCV IFN-α inhibition kinetics in vitro has brought us closer to understanding the mechanism(s) by which IFN-α may be inhibiting HCV in vivo.
Human Cytomegalovirus Protein pp71 Induces Daxx SUMOylation
Authors: Hwang Jiwon , Kalejta Robert F. 
Published: April 2009

ABSTRACT
Proteins that participate in a diverse array of cellular processes can be modified covalently and reversibly on lysine residues by the small ubiquitin-like modifier proteins termed SUMOs. In some instances, such modification profoundly affects protein function, but the biological significance of many SUMOylation events remains unknown. Protein SUMOylation is modulated during many viral infections. Here we demonstrate that the human cytomegalovirus (HCMV) pp71 protein promotes the SUMOylation of its cellular substrate, Daxx. A component of promyelocytic leukemia nuclear bodies, Daxx is a transcriptional corepressor that silences the expression of viral immediate-early (IE) genes at the start of both lytic and quiescent HCMV infections. pp71 is a tegument component delivered directly to cells by infecting HCMV virions. At the start of lytic infections, it travels to the nucleus and stimulates viral IE gene expression by displacing the chromatin remodeling protein ATRX from Daxx and by mediating Daxx degradation through a rare ubiquitin-independent, proteasome-dependent process. Here we report that pp71 also substantially increases the basal level of SUMOylated Daxx observed in cells. To date, consequences of Daxx SUMOylation have not been observed for cellular promoters, and we detected no qualitative change in viral IE gene expression in the absence of pp71-induced Daxx SUMOylation. Thus, while pp71 enhances the basal level of SUMOylated Daxx, the role that this modification plays in regulating Daxx activity in uninfected or HCMV-infected cells remains an enigma.
AMP-activated protein kinase promotes human prostate cancer cell growth and survival
Authors: Park Hyeon Ung , Suy Simeng , Danner Malika , Dailey Vernon , Zhang Ying , Li Henghong , Hyduke Daniel R. , Collins Brian T. , Gagnon Gregory , Kallakury Bhaskar , Kumar Deepak , Brown Milton L. , Fornace Albert , Dritschilo Anatoly , Collins Sean P. 
Published: April 2009

Abstract
The molecular mechanisms underlying the development and progression of prostate cancer are poorly understood. AMP-activated protein kinase (AMPK) is a serine-threonine kinase that is activated in response to the hypoxic conditions found in human prostate cancers. In response to energy depletion, AMPK activation promotes metabolic changes to maintain cell proliferation and survival. Here, we report prevalent activation of AMPK in human prostate cancers and provide evidence that inhibition or depletion of AMPK leads to decreased cell proliferation and increased cell death. AMPK was highly activated in 40% of human prostate cancer specimens examined. Endogenous AMPK was active in both the androgen-sensitive LNCaP cells and the androgen-independent CWR22Rv1 human prostate cancer cells. Depletion of AMPK catalytic subunits by small interfering RNA or inhibition of AMPK activity with a small-molecule AMPK inhibitor (compound C) suppresses human prostate cancer cell proliferation. Apoptotic cell death was induced in LNCaP and CWR22Rv1 cells at compound C concentrations that inhibited AMPK activity. The evidence provided here is the first report that the activated AMPK pathway is involved in the growth and survival of human prostate cancer and offers novel potential targets for chemoprevention of human prostate cancer. [Mol Cancer Ther 2009;8(4):733–41]
Increased AKT S473 phosphorylation after mTORC1 inhibition is rictor dependent and does not predict tumor cell response to PI3K/mTOR inhibition
Authors: Breuleux Madlaina , Klopfenstein Matthieu , Stephan Christine , Doughty Cheryl A. , Barys Louise , Maira Saveur-Michel , Kwiatkowski David , Lane Heidi A. 
Published: April 2009

Abstract
Mammalian target of rapamycin (mTOR) regulates cellular processes important for progression of human cancer. RAD001 (everolimus), an mTORC1 (mTOR/raptor) inhibitor, has broad antitumor activity in preclinical models and cancer patients. Although most tumor lines are RAD001 sensitive, some are not. Selective mTORC1 inhibition can elicit increased AKT S473 phosphorylation, involving insulin receptor substrate 1, which is suggested to potentially attenuate effects on tumor cell proliferation and viability. Rictor may also play a role because rictor kinase complexes (including mTOR/rictor) regulate AKT S473 phosphorylation. The role of raptor and rictor in the in vitro response of human cancer cells to RAD001 was investigated. Using a large panel of cell lines representing different tumor histotypes, the basal phosphorylation of AKT S473 and some AKT substrates was found to correlate with the antiproliferative response to RAD001. In contrast, increased AKT S473 phosphorylation induced by RAD001 did not correlate. Similar increases in AKT phosphorylation occurred following raptor depletion using siRNA. Strikingly, rictor down-regulation attenuated AKT S473 phosphorylation induced by mTORC1 inhibition. Further analyses showed no relationship between modulation of AKT phosphorylation on S473 and T308 and AKT substrate phosphorylation patterns. Using a dual pan-class I phosphatidylinositol 3-kinase/mTOR catalytic inhibitor (NVP-BEZ235), currently in phase I trials, concomitant targeting of these kinases inhibited AKT S473 phosphorylation, eliciting more profound cellular responses than mTORC1 inhibition alone. However, reduced cell viability could not be predicted from biochemical or cellular responses to mTORC1 inhibitors. These data could have implications for the clinical application of phosphatidylinositol 3-kinase/mTOR inhibitors. [Mol Cancer Ther 2009;8(4):742–53]
Opposing control of rhabdomyosarcoma growth and differentiation by myogenin and interleukin 4
Authors: Nanni Patrizia , Nicoletti Giordano , Palladini Arianna , Astolfi Annalisa , Rinella Paola , Croci Stefania , Landuzzi Lorena , Monduzzi Giada , Stivani Valeria , Antognoli Agnese , Murgo Annalisa , Ianzano Marianna , De Giovanni Carla , Lollini Pier-Luigi 
Published: April 2009

Abstract
Rhabdomyosarcoma is a tumor of striated muscle origin that displays defective myogenic differentiation. Terminal myogenesis switches off cell proliferation and migration, hence, the promotion of rhabdomyosarcoma differentiation should antagonize tumor growth and metastasis. Terminal myogenesis is controlled by cell-intrinsic myogenic transcription factors like myogenin and environmental mediators like interleukin 4 (IL-4). We studied whether the expression of myogenin or exposure to IL-4 could promote the myogenesis of poorly differentiating human rhabdomyosarcoma cells RD/12. Forced expression of myogenin amplified myosin expression and the formation of myotube-like elements, inhibited cell migration, and reduced the growth of local tumors and liver metastases in immunodepressed mice. In contrast, exposure to IL-4 promoted cell proliferation and survival, especially at high cell density, inhibited myogenin expression, and myogenesis. Moreover, IL-4 stimulated the directed migration of cells with low myogenin levels, but not of cells with higher (spontaneous or forced) levels. Thus, IL-4, which was known to promote late stages of normal myogenesis, favors growth and migration, and inhibits further differentiation of the myogenic stages attained by rhabdomyosarcoma cells. Strategies to increase myogenin expression and block IL-4 could simultaneously reduce growth and migration, and enhance terminal differentiation of rhabdomyosarcoma, thus contributing to the control of tumor growth and metastatic spread. [Mol Cancer Ther 2009;8(4):754–61]
Aminopeptidase inhibition as a targeted treatment strategy in myeloma
Authors: Moore Hannah E. , Davenport Emma L. , Smith Emma M. , Muralikrishnan Srikanth , Dunlop Alan S. , Walker Brian A. , Krige David , Drummond Alan H. , Hooftman Leon , Morgan Gareth J. , Davies Faith E. 
Published: April 2009

Abstract
Myeloma cells are highly dependent on the unfolded protein response to assemble folded immunoglobulins correctly. Therefore, targeting protein handling within a myeloma cell by inhibiting the aminopeptidase enzyme system, which catalyses the hydrolysis of amino acids from the proteins NH2 terminus, represents a therapeutic approach. CHR-2797, a novel aminopeptidase inhibitor, is able to inhibit proliferation and induce growth arrest and apoptosis in myeloma cells, including cells resistant to conventional chemotherapeutics. It causes minimal inhibition of bone marrow stromal cell (BMSC) proliferation but is able to overcome the microenvironmental protective effects, inhibiting the proliferation of myeloma cells bound to BMSCs and the increase in vascular endothelial growth factor levels seen when myeloma cells and BMSCs are bound together. Additive and synergistic effects are seen with bortezomib, melphalan, and dexamethasone. Apoptosis occurs via both caspase-dependent and non-caspase-dependent pathways with an increase in Noxa, cleavage of Mcl-1, and activation of the unfolded protein response. Autophagy is also seen. CHR-2797 causes an up-regulation of genes involved in the proteasome/ubiquitin pathway, as well as aminopeptidases, and amino acid deprivation response genes. In conclusion, inhibiting protein turnover using the aminopeptidase inhibitor CHR-2797 results in myeloma cell apoptosis and represents a novel therapeutic approach that warrants further investigation in the clinical setting. [Mol Cancer Ther 2009;8(4):762–70]