Journal articles on the topic 'VIRF'
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1
Schrammeijer, B., J. Hemelaar, and P. J. J. Hooykaas. "The Presence and Characterization of a virF Gene on Agrobacterium vitis Ti Plasmids." Molecular Plant-Microbe Interactions® 11, no. 5 (May 1998): 429–33. http://dx.doi.org/10.1094/mpmi.1998.11.5.429.
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Octopine and nopaline strains of Agrobacterium tumefaciens differ in their ability to induce tumors on Nicotiana glauca. The presence of a virF locus on the octopine Ti plasmid makes N. glauca a host plant for these strains, indicating that the VirF protein is a host-range determinant. Here we show the presence of a virF locus not only on the Agrobacterium vitis octopine/cucumopine plasmids pTiAg57 and pTiTm4, but also on the nopaline Ti plas-mids pTiAT1, pTiAT66a, and pTiAT66b. On the octopine Ti plasmids from A. tumefaciens the virF gene is located between the virE locus and the left border of the T-region. In contrast, the virF gene on Ti plasmids of A. vitis is located at the very left end of the vir-region near the virA locus. The virF gene of pTiAg57 has been sequenced and codes for a protein of 202 amino acids with a molecular mass of 22,280 Da. Comparison showed that the virF gene from A. vitis strain Ag57 is almost identical to that from A. tumefaciens octopine strains. The transcription of the pTiAg57 virF is inducible by the plant phenolic compound acetosyringone through the presence of a vir-box consensus sequence in its promoter region. The VirF protein from pTiAg57 can complement octopine A. tumefaciens strains deleted for virF as shown by tumor formation on N. glauca.
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Wing, Helen J., Arthur W. Yan, Seth R. Goldman, and Marcia B. Goldberg. "Regulation of IcsP, the Outer Membrane Protease of the Shigella Actin Tail Assembly Protein IcsA, by Virulence Plasmid Regulators VirF and VirB." Journal of Bacteriology 186, no. 3 (February 1, 2004): 699–705. http://dx.doi.org/10.1128/jb.186.3.699-705.2004.
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ABSTRACT The Shigella outer membrane protease IcsP removes the actin assembly protein IcsA from the bacterial surface, and consequently modulates Shigella actin-based motility and cell-to-cell spread. Here, we demonstrate that IcsP expression is undetectable in mutants lacking either of two transcriptional activators, VirF and VirB. In wild-type Shigella spp., virB expression is entirely dependent on VirF; therefore, to circumvent this regulatory cascade, we independently expressed VirF or VirB in Shigella strains lacking both activators and measured both IcsP levels and transcription from the icsP promoter. Our results show that VirB significantly enhanced icsP transcription, even in the absence of VirF. In contrast, when VirF was induced in the absence of VirB, VirF had variable effects. The regulation of icsP is distinctly different from the regulation of the gene encoding its major substrate, icsA, which is activated by VirF and not VirB. We propose that the different pathways regulating icsA and icsP may be critical to the modulation of IcsA-mediated actin-based motility by IcsP.
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Okumura, Kayo, Kaori Ohtani, Hideo Hayashi, and Tohru Shimizu. "Characterization of Genes Regulated Directly by the VirR/VirS System in Clostridium perfringens." Journal of Bacteriology 190, no. 23 (September 12, 2008): 7719–27. http://dx.doi.org/10.1128/jb.01573-07.
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ABSTRACT Analysis of the complete sequence of the genome of Clostridium perfringens strain 13 resulted in identification of five genes, including pfoA (encoding theta toxin) and vrr (encoding VirR/VirS-regulated RNA), with consensus VirR-binding sequences upstream of the open reading frame (ORF), suggesting that expression of these genes may be regulated directly by the two-component VirR/VirS system. To test this possibility, we examined VirR/VirS system-mediated transcriptional regulation of three genes, virT, ccp (encoding alpha-clostripain), and virU, with the novel VirR-binding sequences. Northern analysis revealed that the steady-state levels (increases or decreases in the amounts of RNA expressed) of virT, ccp, and virU mRNAs were lower in a virR mutant strain than in the wild-type strain, as were the levels of the pfoA and vrr transcripts. The consensus VirR-binding sites were located similarly relative to the transcription start sites in the virT, ccp, and virU promoters. Mutation and overexpression analyses with virT and virU revealed that the virT gene product has a negative effect on expression of pfoA and ccp, whereas the virU gene product positively affects expression of pfoA, virT, ccp, and vrr. Nonsense and frameshift mutations in the virT or virU putative ORF did not affect the regulatory functions, suggesting that virT and virU may encode RNA regulators rather than proteins. These results suggest that a complex regulatory network, perhaps involving several regulatory RNA molecules, governs the expression of the VirR/VirS regulon in C. perfringens.
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Kalogeraki, Virginia S., Jun Zhu, Joel L. Stryker, and Stephen C. Winans. "The Right End of the vir Region of an Octopine-Type Ti Plasmid Contains Four New Members of the vir Regulon That Are Not Essential for Pathogenesis." Journal of Bacteriology 182, no. 6 (March 15, 2000): 1774–78. http://dx.doi.org/10.1128/jb.182.6.1774-1778.2000.
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ABSTRACT We sequenced the virD-virE, virE-virF, andvirF–T-DNA intergenic regions of an octopine Ti plasmid. Four newly described genes were induced by the vir gene inducer acetosyringone, two of which are conserved in the nopaline-type Ti plasmid pTiC58. One gene resembles a family of phosphatase genes. Each of these genes is dispensible for tumorigenesis.
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Porter, Megan E., and Charles J. Dorman. "In Vivo DNA-Binding and Oligomerization Properties of the Shigella flexneri AraC-Like Transcriptional Regulator VirF as Identified by Random and Site-Specific Mutagenesis." Journal of Bacteriology 184, no. 2 (January 15, 2002): 531–39. http://dx.doi.org/10.1128/jb.184.2.531-539.2002.
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ABSTRACT In Shigella flexneri expression of the plasmid-encoded virulence genes is regulated via a complex mechanism involving both environmental signals and specific transactivators. The primary regulator protein, VirF, is a member of the AraC family of transcription factors and shares with other AraC-like proteins a conserved carboxy-terminal domain thought to be important for DNA binding. Random and site-directed mutagenesis of the virF gene encoding VirF yielded a number of mutations along the length of the protein which severely affected the ability of VirF to activate gene expression. The mutant proteins were shown to be affected in their ability to activate the virulence genes virB and icsA, both known to be regulated directly by VirF, as well as the virB-dependent virulence gene mxiC. Mutating key residues predicted to be important for DNA recognition had a significant negative effect, thereby suggesting that VirF interacts with its target sequence via two helix-turn-helix motifs. Two mutants that were dominant negative when coexpressed with the wild-type VirF protein were also isolated, indicating a role for protein-protein oligomerization in normal VirF function.
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Nakayama, Shu-ichi, and Haruo Watanabe. "Identification of cpxR as a Positive Regulator Essential for Expression of the Shigella sonnei virF Gene." Journal of Bacteriology 180, no. 14 (July 15, 1998): 3522–28. http://dx.doi.org/10.1128/jb.180.14.3522-3528.1998.
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ABSTRACT virF is the master regulator which activates the virulence determinant genes of Shigella spp. such asipaBCD and virG. We previously reported that expression of virF itself is regulated in a pH-dependent manner and that cpxA, a sensor of a two-component regulatory system, is involved in this regulation (S. Nakayama and H. Watanabe, J. Bacteriol. 177:5062–5069, 1995). Disruption of cpxR, which has been thought to be the cognate response regulator of cpxA (J. Dong, S. Iuchi, H.-S. Kwan, Z. Lue, and E. C. C. Lin, Gene 136:227–230, 1993), abolishedvirF expression almost completely. Purified CpxR bound directly to the upstream region of virF. Binding capacity was enhanced when CpxR was phosphorylated by coincubation with acetyl phosphate in vitro. Furthermore, we observed that phosphorylated CpxR could activate virF transcription in vitro. These results clearly indicated that CpxR was an essential activator for virF expression and strongly suggested that the binding of phosphorylated CpxR to the target site upstream of the virF gene induced a direct activation of virF transcription.
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Gall, Tony Le, Maria Mavris, Maria Celeste Martino, Maria Lina Bernardini, Erick Denamur, and Claude Parsot. "Analysis of virulence plasmid gene expression defines three classes of effectors in the type III secretion system of Shigella flexneri." Microbiology 151, no. 3 (March 1, 2005): 951–62. http://dx.doi.org/10.1099/mic.0.27639-0.
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Proteins directly involved in entry and dissemination of Shigella flexneri into epithelial cells are encoded by a virulence plasmid of 200 kb. A 30-kb region (designated the entry region) of this plasmid encodes components of a type III secretion (TTS) apparatus, substrates of this apparatus and their dedicated chaperones. During growth of bacteria in broth, expression of these genes is induced at 37 °C and the TTS apparatus is assembled in the bacterial envelope but is not active. Secretion is activated upon contact of bacteria with host cells and is deregulated in an ipaB mutant. The plasmid encodes four transcriptional regulators, VirF, VirB, MxiE and Orf81. VirF controls transcription of virB, whose product is required for transcription of entry region genes. MxiE, with the chaperone IpgC acting as a co-activator, controls expression of several effectors that are induced under conditions of secretion. Genes under the control of Orf81 are not known. The aim of this study was to define further the repertoires of virulence plasmid genes that are under the control of (i) the growth temperature, (ii) each of the known virulence plasmid-encoded transcriptional regulators (VirF, VirB, MxiE and Orf81) and (iii) the activity of the TTS apparatus. Using a macroarray analysis, the expression profiles of 71 plasmid genes were compared in the wild-type strain grown at 37 and 30 °C and in virF, virB, mxiE, ipaB, ipaB mxiE and orf81 mutants grown at 37 °C. Many genes were found to be under the control of VirB and indirectly of VirF. No alteration of expression of any gene was detected in the orf81 mutant. Expression of 13 genes was increased in the secretion-deregulated ipaB mutant in an MxiE-dependent manner. On the basis of their expression profile, substrates of the TTS apparatus can be classified into three categories: (i) those that are controlled by VirB, (ii) those that are controlled by MxiE and (iii) those that are controlled by both VirB and MxiE. The differential regulation of expression of TTS effectors in response to the TTS apparatus activity suggests that different effectors might be required at different times following contact of bacteria with host cells.
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Xiang, Qiwang, Zunlin Yang, and John Nicholas. "STAT and Janus kinase targeting by human herpesvirus 8 interferon regulatory factor in the suppression of type-I interferon signaling." PLOS Pathogens 18, no. 7 (July 1, 2022): e1010676. http://dx.doi.org/10.1371/journal.ppat.1010676.
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Human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma (KS)-associated herpesvirus, is involved etiologically in AIDS-associated KS, primary effusion lymphoma (PEL), and multicentric Castleman’s disease, in which both viral latent and lytic functions are important. HHV-8 encodes four viral interferon regulatory factors (vIRFs) that are believed to contribute to viral latency (in PEL cells, at least) and/or to productive replication via suppression of cellular antiviral and stress signaling. Here, we identify vIRF-1 interactions with signal transducer and activator of transcription (STAT) factors 1 and 2, interferon type-I (IFN-I)-stimulated gene factor 3 (ISGF3) cofactor IRF9, and associated signal transducing Janus kinases JAK1 and TYK2. In naturally infected PEL cells and in iSLK epithelial cells infected experimentally with genetically engineered HHV-8, vIRF-1 depletion or ablation, respectively, led to increased STAT1 and STAT2 activation (phosphorylation) in IFNβ-treated, and untreated, cells during lytic replication and to associated cellular-gene induction. In transfected 293T cells, used for mechanistic studies, suppression by vIRF-1 of IFNβ-induced phospho-STAT1 (pSTAT1) was found to be highly dependent on STAT2, indicating vIRF-1-mediated inhibition and/or dissociation of ISGF3-complexing, resulting in susceptibility of pSTAT1 to inactivating dephosphorylation. Indeed, coprecipitation experiments involving targeted precipitation of ISGF3 components identified suppression of mutual interactions by vIRF-1. In contrast, suppression of IFNβ-induced pSTAT2 was effected by inhibition of TYK2 and its interactions with STAT2 and IFN-I receptor (IFNAR). Our identified vIRF-1 interactions with IFN-signaling mediators STATs 1 and 2, co-interacting ISGF3 component IRF9, and STAT-activating TYK2 and the suppression of IFN signaling via ISGF3, TYK2-STAT2 and TYK2-IFNAR disruption and TYK2 inhibition represent novel mechanisms of vIRF function and HHV-8 evasion from host-cell defenses.
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Koppolu, Veerendra, Ichie Osaka, Jeff M. Skredenske, Bria Kettle, P. Scott Hefty, Jiaqin Li, and Susan M. Egan. "Small-Molecule Inhibitor of the Shigella flexneri Master Virulence Regulator VirF." Infection and Immunity 81, no. 11 (September 3, 2013): 4220–31. http://dx.doi.org/10.1128/iai.00919-13.
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ABSTRACTVirF is an AraC family transcriptional activator that is required for the expression of virulence genes associated with invasion and cell-to-cell spread byShigella flexneri, including multiple components of the type three secretion system (T3SS) machinery and effectors. We tested a small-molecule compound, SE-1 (formerly designated OSSL_051168), which we had identified as an effective inhibitor of the AraC family proteins RhaS and RhaR, for its ability to inhibit VirF. Cell-based reporter gene assays withEscherichia coliandShigella, as well asin vitroDNA binding assays with purified VirF, demonstrated that SE-1 inhibited DNA binding and transcription activation (likely by blocking DNA binding) by VirF. Analysis of mRNA levels using real-time quantitative reverse transcription-PCR (qRT-PCR) further demonstrated that SE-1 reduced the expression of the VirF-dependent virulence genesicsA,virB,icsB, andipaBinShigella. We also performed eukaryotic cell invasion assays and found that SE-1 reduced invasion byShigella. The effect of SE-1 on invasion required preincubation ofShigellawith SE-1, in agreement with the hypothesis that SE-1 inhibited the expression of VirF-activated genes required for the formation of the T3SS apparatus and invasion. We found that the same concentrations of SE-1 had no detectable effects on the growth or metabolism of the bacterial cells or the eukaryotic host cells, respectively, indicating that the inhibition of invasion was not due to general toxicity. Overall, SE-1 appears to inhibit transcription activation by VirF, exhibits selectivity toward AraC family proteins, and has the potential to be developed into a novel antibacterial agent.
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Karney, Monika, Joy McKenna, Natasha Weatherspoon-Griffin, Alexander Karabachev, Makensie Millar, Eliese Potocek, and Helen Wing. "Investigating the DNA-Binding Site for VirB, a Key Transcriptional Regulator of Shigella Virulence Genes, Using an In Vivo Binding Tool." Genes 10, no. 2 (February 15, 2019): 149. http://dx.doi.org/10.3390/genes10020149.
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The transcriptional anti-silencing and DNA-binding protein, VirB, is essential for the virulence of Shigella species and, yet, sequences required for VirB-DNA binding are poorly understood. While a 7-8 bp VirB-binding site has been proposed, it was derived from studies at a single VirB-dependent promoter, icsB. Our previous in vivo studies at a different VirB-dependent promoter, icsP, found that the proposed VirB-binding site was insufficient for regulation. Instead, the required site was found to be organized as a near-perfect inverted repeat separated by a single nucleotide spacer. Thus, the proposed 7-8 bp VirB-binding site needed to be re-evaluated. Here, we engineer and validate a molecular tool to capture protein-DNA binding interactions in vivo. Our data show that a sequence organized as a near-perfect inverted repeat is required for VirB-DNA binding interactions in vivo at both the icsB and icsP promoters. Furthermore, the previously proposed VirB-binding site and multiple sites found as a result of its description (i.e., sites located at the virB, virF, spa15, and virA promoters) are not sufficient for VirB to bind in vivo using this tool. The implications of these findings are discussed.
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Morin, Gabriela, Bridget A. Robinson, Kelsey S. Rogers, and Scott W. Wong. "A Rhesus Rhadinovirus Viral Interferon (IFN) Regulatory Factor Is Virion Associated and Inhibits the Early IFN Antiviral Response." Journal of Virology 89, no. 15 (May 13, 2015): 7707–21. http://dx.doi.org/10.1128/jvi.01175-15.
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ABSTRACTThe interferon (IFN) response is the earliest host immune response dedicated to combating viral infection. As such, viruses have evolved strategies to subvert this potent antiviral response. Two closely related gammaherpesviruses, Kaposi's sarcoma-associated herpesvirus (KSHV) and rhesus macaque rhadinovirus (RRV), are unique in that they express viral homologues to cellular interferon regulatory factors (IRFs), termed viral IRFs (vIRFs). Cellular IRFs are a family of transcription factors that are particularly important for the transcription of type I IFNs. Here, we demonstrate a strategy employed by RRV to ensure rapid inhibition of virus-induced type I IFN induction. We found that RRV vIRF R6, when expressed ectopically, interacts with a transcriptional coactivator, CREB-binding protein (CBP), in the nucleus. As a result, phosphorylated IRF3, an important transcriptional regulator in beta interferon (IFN-β) transcription, fails to effectively bind to the IFN-β promoter, thus inhibiting the activation of IFN-β genes. In addition, we found R6 within RRV virion particles via immunoelectron microscopy and, furthermore, that virion-associated R6 is capable of inhibiting the type I IFN response by preventing efficient binding of IRF3/CBP complexes to the IFN-β promoter in the context of infection. The work shown here is the first example of a vIRF being associated with either the KSHV or RRV virion. The presence of this immunomodulatory protein in the RRV virion provides the virus with an immediate mechanism to evade the host IFN response, thus enabling the virus to effectively establish an infection within the host.IMPORTANCEKaposi's sarcoma-associated herpesvirus (KSHV) and the closely related rhesus macaque rhadinovirus (RRV) are the only viruses known to encode viral homologues to cellular interferon regulatory factors (IRFs), known as vIRFs. In KSHV, these proteins have been shown to play major roles in a variety of cellular processes and are particularly important in the evasion of the host type I interferon (IFN) response. In this study, we delineate the immunomodulatory mechanism of an RRV vIRF and its ability to assist the virus in rapid immune evasion by being prepackaged within the virion, thus providing evidence, for the first time, of a virion-associated vIRF. This work further contributes to our understanding of the mechanisms behind immunomodulation by the RRV vIRFs during infection.
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Mutocheluh, M., L. Hindle, C. Aresté, S. A. Chanas, L. M. Butler, K. Lowry, K. Shah, D. J. Evans, and D. J. Blackbourn. "Kaposi’s sarcoma-associated herpesvirus viral interferon regulatory factor-2 inhibits type 1 interferon signalling by targeting interferon-stimulated gene factor-3." Journal of General Virology 92, no. 10 (October 1, 2011): 2394–98. http://dx.doi.org/10.1099/vir.0.034322-0.
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Kaposi’s sarcoma-associated herpesvirus (KSHV) encodes four viral interferon regulatory factors (vIRF-1–4). We investigated the mechanism and consequences of vIRF-2-mediated inhibition of interferon-response element signalling following type I interferon (IFN) induction. Western blot and electrophoretic mobility-shift assays identified the interferon-stimulated gene factor-3 (ISGF-3) components STAT1 and IRF-9 as the proximal targets of vIRF-2 activity. The biological significance of vIRF-2 inhibition of ISGF-3 was demonstrated by vIRF-2-mediated rescue of the replication of the IFN-sensitive virus encephalomyocarditis virus. This study provides both a mechanism and evidence for KSHV vIRF-2-mediated suppression of the consequences of type 1 IFN-induced signalling.
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Fuld, Suzanne, Charles Cunningham, Kevin Klucher, Andrew J. Davison, and David J. Blackbourn. "Inhibition of Interferon Signaling by the Kaposi's Sarcoma-Associated Herpesvirus Full-Length Viral Interferon Regulatory Factor 2 Protein." Journal of Virology 80, no. 6 (March 15, 2006): 3092–97. http://dx.doi.org/10.1128/jvi.80.6.3092-3097.2006.
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ABSTRACT Interferon (IFN) signal transduction involves interferon regulatory factors (IRF). Kaposi's sarcoma-associated herpesvirus (KSHV) encodes four IRF homologues: viral IRF 1 (vIRF-1) to vIRF-4. Previous functional studies revealed that the first exon of vIRF-2 inhibited alpha/beta interferon (IFN-α/β) signaling. We now show that full-length vIRF-2 protein, translated from two spliced exons, inhibited both IFN-α- and IFN-λ-driven transactivation of a reporter promoter containing the interferon stimulated response element (ISRE). Transactivation of the ISRE promoter by IRF-1 was negatively regulated by vIRF-2 protein as well. Transactivation of a full-length IFN-β reporter promoter by either IRF-3 or IRF-1, but not IRF-7, was also inhibited by vIRF-2 protein. Thus, vIRF-2 protein is an interferon induction antagonist that acts pleiotropically, presumably facilitating KSHV infection and dissemination in vivo.
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Zimring, James C., Stephen Goodbourn, and Margaret K. Offermann. "Human Herpesvirus 8 Encodes an Interferon Regulatory Factor (IRF) Homolog That Represses IRF-1-Mediated Transcription." Journal of Virology 72, no. 1 (January 1, 1998): 701–7. http://dx.doi.org/10.1128/jvi.72.1.701-707.1998.
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ABSTRACT Human herpesvirus 8 (HHV-8) is the probable viral etiologic agent for Kaposi’s sarcoma. The HHV-8 genome encodes viral interferon regulatory factor (vIRF), a gene product that has homology to the IRF family of transcription factors. We demonstrate that vIRF inhibits responses to type I and type II interferons and blocks IRF-1-mediated transcription. vIRF does not compete with IRF-1 for binding to DNA or complex directly with IRF-1. The ability of vIRF to block IRF-1-mediated transcription is independent of the DNA binding domains of both vIRF and IRF-1. These data suggest that vIRF may contribute to viral pathogenesis and cellular transformation by interfering with interferon- and IRF-1-mediated gene expression through a novel mechanism.
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Roan, Florence, James C. Zimring, Stephen Goodbourn, and Margaret K. Offermann. "Transcriptional activation by the human herpesvirus-8-encoded interferon regulatory factor." Journal of General Virology 80, no. 8 (August 1, 1999): 2205–9. http://dx.doi.org/10.1099/0022-1317-80-8-2205.
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Human herpesvirus-8 (HHV-8), a gammaherpesvirus that is thought to be the viral aetiologic agent of Kaposi’s sarcoma and primary effusion lymphoma, encodes a homologue to cellular interferon regulatory factors (IRFs). The HHV-8 IRF homologue (vIRF; ORF K9) has previously been shown to inhibit gene induction by interferons and IRF-1 and to transform NIH3T3 cells or Rat-1 cells. Additionally, expression of antisense to vIRF in BCBL-1 cells results in the repression of certain HHV-8 genes, suggesting that vIRF may also positively regulate gene expression. We demonstrate that vIRF activates transcription when directed to DNA by the GAL4 DNA-binding domain. GAL-vIRF truncation constructs that individually are incapable of activating transcription can cooperate in transactivation when coexpressed in HeLa cells, suggesting that multiple regions of vIRF are involved in transactivation. These studies broaden the potential mechanisms of action of vIRF to include transcriptional activation as well as transcriptional repression.
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Bittinger, M. A., J. A. Gross, J. Widom, J. Clardy, and J. Handelsman. "Rhizobium etli CE3 Carries vir Gene Homologs on a Self-Transmissible Plasmid." Molecular Plant-Microbe Interactions® 13, no. 9 (September 2000): 1019–21. http://dx.doi.org/10.1094/mpmi.2000.13.9.1019.
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RosR is a transcriptional regulator important for determining cell-surface characteristics and nodulation competitiveness in Rhizobium etli CE3. We identified a 15-kb region that contains genes with similarity to members of the virB, virC, virG, and virE operons of Agrobacterium tumefaciens and demonstrated that RosR directly regulates one operon in this region. These genes were located on plasmid pa of R. etli CE3, which is self-transmissible between R. etli and A. tumefaciens.
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Burýšek, Ladislav, and Paula M. Pitha. "Latently Expressed Human Herpesvirus 8-Encoded Interferon Regulatory Factor 2 Inhibits Double-Stranded RNA-Activated Protein Kinase." Journal of Virology 75, no. 5 (March 1, 2001): 2345–52. http://dx.doi.org/10.1128/jvi.75.5.2345-2352.2001.
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ABSTRACT Human herpesvirus 8 (HHV-8; Kaposi's sarcoma herpesvirus) encodes four open reading frames with homology to cellular proteins of interferon regulatory factor (IRF) family. Three of them, viral IRF-1 (vIRF-1), vIRF-2, and vIRF-3, have been cloned and found, when overexpressed, to down-regulate the transcriptional activity of interferon type I gene promoters in infected cells by interfering with the transactivating activity of cellular IRFs. In this study, we have further characterized vIRF-2 and shown that it is a nuclear protein which is constitutively expressed in HHV-8-positive pleural effusion lymphoma cell lines. Nuclear localization of vIRF-2 was confirmed by in situ detection of ectopically expressed enhanced green fluorescent protein/vIRF-2 fusion protein. We found that the expression of vIRF-2 in HEK293 cells inhibited the antiviral effect of interferon and rescued translation of vesicular stomatitis virus mRNA from interferon-induced translational block. To provide insight into the mechanism of this effect we have demonstrated that vIRF-2 physically interacts with PKR consequently inhibiting autophosphorylation of double-stranded RNA-activated protein kinase (PKR) and blocking phosphorylation of PKR substrates histone 2A and eukaryotic translation initiation factor 2α. These results suggest that the latently expressed vIRF-2 has a role in viral mimicry which targets the activity of interferon-induced PKR kinase. By inhibiting the kinase activity of PKR and consequent down-modulation of protein synthesis, HHV-8 has evolved a mechanism by which it can overcome the interferon-mediated antiviral effect. Thus, the anti-interferon functions of vIRF-2 may contribute to the establishment of a chronic or latent infection.
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Pozharskaya, Veronika P., Laura L. Weakland, James C. Zimring, Laurie T. Krug, Elizabeth R. Unger, Andrew Neisch, Harish Joshi, Naoki Inoue, and Margaret K. Offermann. "Short Duration of Elevated vIRF-1 Expression during Lytic Replication of Human Herpesvirus 8 Limits Its Ability To Block Antiviral Responses Induced by Alpha Interferon in BCBL-1 Cells." Journal of Virology 78, no. 12 (June 15, 2004): 6621–35. http://dx.doi.org/10.1128/jvi.78.12.6621-6635.2004.
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ABSTRACT Human herpesvirus 8 (HHV-8) encodes multiple proteins that disrupt the host antiviral response, including viral interferon (IFN) regulatory factor 1 (vIRF-1). The product of the vIRF-1 gene blocks responses to IFN when overexpressed by transfection, but the functional consequence of vIRF-1 that is expressed during infection with HHV-8 is not known. These studies demonstrate that BCBL-1 cells that were latently infected with HHV-8 expressed low levels of vIRF-1 that were associated with PML bodies, whereas much higher levels of vIRF-1 were transiently expressed during the lytic phase of HHV-8 replication. The low levels of vIRF-1 that were associated with PML bodies were insufficient to block alpha IFN (IFN-α)-induced alterations in gene expression, whereas cells that expressed high levels of vIRF-1 were resistant to some changes induced by IFN-α, including the expression of the double-stranded-RNA-activated protein kinase. High levels of vIRF-1 were expressed for only a short period during the lytic cascade, so many cells with HHV-8 in the lytic phase responded to IFN-α with increased expression of antiviral genes and enhanced apoptosis. Furthermore, the production of infectious virus was severely compromised when IFN-α was present early during the lytic cascade. These studies indicate that the transient expression of high levels of vIRF-1 is inadequate to subvert many of the antiviral effects of IFN-α so that IFN-α can effectively induce apoptosis and block production of infectious virus when present early in the lytic cascade of HHV-8.
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Lubyova, Barbora, and Paula M. Pitha. "Characterization of a Novel Human Herpesvirus 8-Encoded Protein, vIRF-3, That Shows Homology to Viral and Cellular Interferon Regulatory Factors." Journal of Virology 74, no. 17 (September 1, 2000): 8194–201. http://dx.doi.org/10.1128/jvi.74.17.8194-8201.2000.
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ABSTRACT The genome of the human herpesvirus 8 (HHV-8) contains a cluster of open reading frames (ORFs) encoding proteins with homology to the cellular transcription factors of the interferon regulatory factor (IRF) family. Two of these homologues, vIRF-1 and vIRF-2, were previously identified and functionally analyzed. In this study, we have characterized a novel gene, designated vIRF-3, encoded within the previously predicted ORF K10.5 and our newly identified ORF K10.6. Northern blotting of RNA extracted from BCBL-1 cells with a vIRF-3-specific probe and reverse transcription-PCR analyses revealed a single transcript of 2.2 kb with a splice present in the coding region. The vIRF-3 mRNA levels in BCBL-1 cells were increased upon 12-O-tetradecanoylphorbol-13-acetate treatment, with kinetics of expression similar to those of the early immediate genes. The vIRF-3 ORF encodes a 73-kDa protein with homology to cellular IRF-4 and HHV-8-encoded vIRF-2 and K11. In transient transfection assays with the IFNACAT reporter, vIRF-3 functioned as a dominant-negative mutant of both IRF-3 and IRF-7 and inhibited virus-mediated transcriptional activity of the IFNA promoter. Similarly, the overexpression of vIRF-3 in mouse L929 cells resulted in inhibition of virus-mediated synthesis of biologically active interferons. These results suggest that by targeting IRF-3 and IRF-7, which play a critical role in the activation of alpha/beta interferon (IFN) genes, HHV-8 has evolved a mechanism by which it directly subverts the functions of IRFs and down-regulates the induction of the IFN genes that are important components of the innate immunity.
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Hwang, Keun Young, and Young Bong Choi. "Modulation of Mitochondrial Antiviral Signaling by Human Herpesvirus 8 Interferon Regulatory Factor 1." Journal of Virology 90, no. 1 (October 28, 2015): 506–20. http://dx.doi.org/10.1128/jvi.01903-15.
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ABSTRACTMitochondrial lipid raft-like microdomains, experimentally also termed mitochondrial detergent-resistant membrane fractions (mDRM), play a role as platforms for recruiting signaling molecules involved in antiviral responses such as apoptosis and innate immunity. Viruses can modulate mitochondrial functions for their own survival and replication. However, viral regulation of the antiviral responses via mDRM remains incompletely understood. Here, we report that human herpesvirus 8 (HHV-8) gene product viral interferon regulatory factor 1 (vIRF-1) is targeted to mDRM during virus replication and negatively regulates the mitochondrial antiviral signaling protein (MAVS)-mediated antiviral responses. The N-terminal region of vIRF-1 interacts directly with membrane lipids, including cardiolipin. In addition, a GxRP motif within the N terminus of vIRF-1, conserved in the mDRM-targeting region of mitochondrial proteins, including PTEN-induced putative kinase 1 (PINK1) and MAVS, was found to be important for vIRF-1 association with mitochondria. Furthermore, MAVS, which has the potential to promote vIRF-1 targeting to mDRM possibly by inducing cardiolipin exposure on the outer membrane of mitochondria, interacts with vIRF-1, which, in turn, inhibits MAVS-mediated antiviral signaling. Consistent with these results, vIRF-1 targeting to mDRM contributes to promotion of HHV-8 productive replication and inhibition of associated apoptosis. Combined, our results suggest novel molecular mechanisms for negative-feedback regulation of MAVS by vIRF-1 during virus replication.IMPORTANCESuccessful virus replication is in large part achieved by the ability of viruses to counteract apoptosis and innate immune responses elicited by infection of host cells. Recently, mitochondria have emerged to play a central role in antiviral signaling. In particular, mitochondrial lipid raft-like microdomains appear to function as platforms in cell apoptosis signaling. However, viral regulation of antiviral signaling through the mitochondrial microdomains remains incompletely understood. The present study demonstrates that HHV-8-encoded vIRF-1 targets to the mitochondrial detergent-resistant microdomains via direct interaction with cardiolipin and inhibits MAVS protein-mediated apoptosis and type I interferon gene expression in a negative-feedback manner, thus promoting HHV-8 productive replication. These results suggest that vIRF-1 is the first example of a viral protein to inhibit mitochondrial antiviral signaling through lipid raft-like microdomains.
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Burýšek, Ladislav, Wen-Shuz Yeow, Barbora Lubyová, Merrill Kellum, Susan L. Schafer, Yao Qi Huang, and Paula M. Pitha. "Functional Analysis of Human Herpesvirus 8-Encoded Viral Interferon Regulatory Factor 1 and Its Association with Cellular Interferon Regulatory Factors and p300." Journal of Virology 73, no. 9 (September 1, 1999): 7334–42. http://dx.doi.org/10.1128/jvi.73.9.7334-7342.1999.
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ABSTRACT Human herpesvirus 8/Kaposi sarcoma-associated virus (HHV-8/KSHV) contains, in addition to genes required for viral replication, a unique set of nonstructural genes which may be part of viral mimicry and contribute to viral replication and pathogenesis in vivo. Among these, HHV-8 encodes four open reading frames (ORFs) that showed homology to the transcription factors of the interferon regulatory factor (IRF) family. The ORF K9, viral IRF 1 (vIRF-1), has been cloned, and it was shown that, when overexpressed, it down modulates the interferon-mediated transcriptional activation of the interferon-stimulated gene 15 (ISG 15) promoter, and the role of vIRF-1 in viral mimicry was implied. However, the molecular mechanism of this effect has not been clarified. Here, we extend this observation and show that vIRF-1 also downregulates the transcriptional activity of IFNA gene promoter in infected cells by interfering with the transactivating activity of cellular IRFs, including IRF-1 and IRF-3. We further show that ectopic expression of vIRF-1 in NIH 3T3 cells confers resistance to tumor necrosis factor alpha-induced apoptosis. While vIRF-1 is unable to bind DNA with the same specificity as cellular IRFs, we demonstrate by in vitro binding assay that it can associate with the family of cellular IRFs, such as IRF-1 and the interferon consensus sequence binding protein. vIRF-1 interaction domain was localized between amino acids (aa) 152 and 243. While no binding between the full-size IRF-3 and vIRF-1 could be detected by the same assay, we show that vIRF-1 also targets the carboxy-terminal region (aa 1623 to 2414) of the transcriptional coactivator p300 which could also bind IRF-3 and IRF-1. These results demonstrate that vIRF-1 can modulate the transcription of the IFNA genes by direct heterodimerization with members of the IRF family, as well as by competitive binding with cellular transcription factors to the carboxy-terminal region of p300.
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Nakamura, Hiroyuki, Mengtao Li, Jodi Zarycki, and Jae U. Jung. "Inhibition of p53 Tumor Suppressor by Viral Interferon Regulatory Factor." Journal of Virology 75, no. 16 (August 15, 2001): 7572–82. http://dx.doi.org/10.1128/jvi.75.16.7572-7582.2001.
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ABSTRACT The irreversible cell cycle arrest and apoptosis induced by p53 are part of the host surveillance mechanisms for viral infection and tumor induction. Kaposi's sarcoma-associated herpesvirus (KSHV), the most recently discovered human tumor virus, is associated with the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. The K9 open reading frame of KSHV encodes a viral interferon (IFN) regulatory factor (vIRF) which functions as a repressor for cellular IFN-mediated signal transduction and as an oncoprotein to induce cell growth transformation. Here, we demonstrate that KSHV vIRF interacts with the cellular p53 tumor suppressor through the putative DNA binding region of vIRF and the central region of p53. This interaction suppresses the level of phosphorylation and acetylation of p53 and inhibits transcriptional activation of p53. As a consequence, vIRF efficiently prevents p53-mediated apoptosis. These results suggest that KSHV vIRF interacts with and inhibits the p53 tumor suppressor to circumvent host growth surveillance and to facilitate uncontrolled cell proliferation.
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Chen, Jiguo, Keiji Ueda, Shuhei Sakakibara, Toshiomi Okuno, and Koichi Yamanishi. "Transcriptional Regulation of the Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor Gene." Journal of Virology 74, no. 18 (September 15, 2000): 8623–34. http://dx.doi.org/10.1128/jvi.74.18.8623-8634.2000.
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ABSTRACT The Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, open reading frame (ORF) K9 encodes a viral interferon regulatory factor (vIRF) that functions as a repressor for interferon-mediated signal transduction. Consequently, this gene is thought to play an important role in the tumorigenicity of KSHV. To understand the molecular mechanisms underlying vIRF expression, we studied the transcriptional regulation of this gene. Experiments using 5′ rapid amplification of cDNA ends and primer extension revealed that vIRF had different transcriptional patterns during the latent and lytic phases. The promoter region of the minor transcript, which was mainly expressed in uninduced BCBL-1 cells, did not contain a canonical TATA box, but a cap-like element and an initiator element flanked the transcription start site. The promoter of the major transcript, which was mainly expressed in tetradecanoyl phorbol acetate-induced BCBL-1 cells, contained a canonical TATA box. A luciferase reporter assay using a deletion mutant of the vIRF promoter and a mutation in the TATA box showed that the TATA box was critical for the lytic activity of vIRF. The promoter activity in the latent phase was eight times stronger than that of the empty vector but was less than 10% of the activity in the lytic phase. Therefore, KSHV may use different functional promoter elements to regulate the expression of vIRF and to antagonize the cell's interferon-mediated antiviral activity. We have also identified a functional domain in the ORF 50 protein, an immediate-early gene product that is mainly encoded by ORF 50. The ORF 50 protein transactivated the vIRF and DNA polymerase promoters in BCBL-1, 293T, and CV-1 cells. Deleting one of its two putative nuclear localization signals (NLSs) resulted in failure of the ORF 50 protein to localize to the nucleus and consequently abrogated its transactivating activity. We further confirmed that the N-terminal region of the ORF 50 protein included an NLS domain. We found that this domain was sufficient to translocate β-galactosidase to the nucleus. Analysis of deletions within the vIRF promoter suggested that two sequence domains were important for its transactivation by the ORF 50 protein, both of which included putative SP-1 and AP-1 binding sites. Competition gel shift assays demonstrated that SP-1 bound to these two domains, suggesting that the SP-1 binding sites in the vIRF promoter are involved in its transactivation by ORF 50.
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Smith, David C., and Elena-Adriana Perseil. "Sb-rich rutile in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrology and crystal-chemistry." Mineralogical Magazine 61, no. 408 (October 1997): 655–69. http://dx.doi.org/10.1180/minmag.1997.061.408.04.
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AbstractThe petrographical, crystal-chemical and petrogenetical aspects of rutile rich in antimony (up to 33.75 wt.% Sb2O5; equal to 0.2 Sb5+ per O = 2) from St. Marcel-Praborna in the Aosta Valley, Italy, were re-examined. These compositions occur in two different petrographical environments (within the rock matrix or as microinclusions within Sb-rich titanite) in the manganese concentrations at this locality. The new data confirm our earlier hypothesis that two distinct petrogenetical/crystal-chemical processes both occurred: 1. Sb-metasomatism of pre-existing Sb-free rutile inclusions; and 2. creation of neoblastic Sb-rich rutile by the expulsion of Ti from pre-existing Sb-free titanite being metasomatized by Sb to form Sb-rich titanite. In the literature, Sb in minerals is variably considered as being trivalent and/or pentavalent. This work demonstrates that within rutile it is entirely Sb5+, substituting for Ti4+ by the following heterovalent cation exchange mechanism which is also the dominant one in the host Sb-rich titanite: 2 viR4+ = viR3+ + viR5+, where viR3+ = (Al,Cr,Mn,Fe)3+. A near-perfect correlation of ΣR5+vs. ΣR3+ (r > 0.98) is perturbed only by the presence of trace amounts of Ca2+, Sr2+ and Ba2+. Traces of Mn4+, Si4+ and/or (OH)− might also be present. These alkaline earth cations are the largest cations ever recorded in the rutile structure and are seemingly too large to occupy normal octahedral sites. The cation exchange mechanism involved might be that found in the ‘trirutile’ mineral group: 3 viR4+ = viR2+ + 2 viR5+. Alternatively these large divalent cations may be situated in the lozenge-shaped tunnels of the rutile structure, by analogy with other large cations occupying the wider subrectangular tunnels in the analogous cryptomelane/hollandite/priderite, romanéchite and todorokite mineral groups. This leads to a possible new cation exchange mechanism for the rutile structure: 2 viR4+ + tunelvacant = 2 viR3+ + tunnelR2+.
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Li, M., B. Damania, X. Alvarez, V. Ogryzko, K. Ozato, and J. U. Jung. "Inhibition of p300 Histone Acetyltransferase by Viral Interferon Regulatory Factor." Molecular and Cellular Biology 20, no. 21 (November 1, 2000): 8254–63. http://dx.doi.org/10.1128/mcb.20.21.8254-8263.2000.
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ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) has been consistently identified in Kaposi's sarcomas, body cavity-based lymphomas, and some forms of Castleman's disease. The K9 open reading frame of KSHV encodes a viral interferon regulatory factor (vIRF) which functions as a repressor for cellular interferon-mediated signal transduction and as an oncogene to induce cell growth transformation. We demonstrate that KSHV vIRF directly interacts with cellular transcriptional coactivator p300 and displaces p300/CBP-associated factor from p300 complexes. This interaction inhibits the histone acetyltransferase activity of p300, resulting in drastic reduction of nucleosomal histone acetylation and alteration of chromatin structure. As a consequence, vIRF expression markedly alters cellular cytokine expression, which is regulated by acetylation of nucleosomal histones. These results demonstrate that KSHV vIRF interacts with and inhibits the p300 transcriptional coactivator to circumvent the host antiviral immune response and to induce a global alteration of cellular gene expression. These studies also illustrate how a cellular gene captured by a herpesvirus has evolved several functions that suit the needs of the virus.
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Gore, Aja L., and Shelley M. Payne. "CsrA and Cra Influence Shigella flexneri Pathogenesis." Infection and Immunity 78, no. 11 (August 16, 2010): 4674–82. http://dx.doi.org/10.1128/iai.00589-10.
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ABSTRACT Shigella flexneri is a facultative intracellular pathogen that invades and disrupts the colonic epithelium. In order to thrive in the host, S. flexneri must adapt to environmental conditions in the gut and within the eukaryotic cytosol, including variability in the available carbon sources and other nutrients. We examined the roles of the carbon consumption regulators CsrA and Cra in a cell culture model of S. flexneri virulence. CsrA is an activator of glycolysis and a repressor of gluconeogenesis, and a csrA mutant had decreased attachment and invasion of cultured cells. Conversely, Cra represses glycolysis and activates gluconeogenesis, and the cra mutant had an increase in both attachment and invasion compared to the wild-type strain. Both mutants were defective in plaque formation. The importance of the glycolytic pathway in invasion and plaque formation was confirmed by testing the effect of a mutation in the glycolysis gene pfkA. The pfkA mutant was noninvasive and had cell surface alterations as indicated by decreased sensitivity to SDS and an altered lipopolysaccharide profile. The loss of invasion by the csrA and pfkA mutants was due to decreased expression of the S. flexneri virulence factor regulators virF and virB, resulting in decreased production of Shigella invasion plasmid antigens (Ipa). These data indicate that regulation of carbon metabolism and expression of the glycolysis gene pfkA are critical for synthesis of the virulence gene regulators VirF and VirB, and both the glycolytic and gluconeogenic pathways influence steps in S. flexneri invasion and plaque formation.
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Wies, Effi, Yasuko Mori, Alexander Hahn, Elisabeth Kremmer, Michael Stürzl, Bernhard Fleckenstein, and Frank Neipel. "The viral interferon-regulatory factor-3 is required for the survival of KSHV-infected primary effusion lymphoma cells." Blood 111, no. 1 (January 1, 2008): 320–27. http://dx.doi.org/10.1182/blood-2007-05-092288.
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Human herpesvirus-8 (HHV-8), also known as Kaposi sarcoma–associated herpesvirus (KSHV), is etiologically linked to primary effusion lymphoma (PEL). At least 10 KSHV-encoded proteins with potential roles in KSHV-associated neoplasia have been identified. However, with few exceptions, these putative oncogenes were analyzed in heterologous systems only using overexpression of single genes. Thus, the pathogenetic relevance of most of these putative oncogenes remains essentially unclear. We used RNA interference (RNAi) to knock down the expression of several KSHV genes in cultured PEL cells carrying the KSHV genome. The viral interferon-regulatory factor-3 (vIRF-3) was found to be required for proliferation and survival of cultured PEL cells. Knock-down of vIRF-3 expression by various RNAi approaches unequivocally resulted in reduced proliferation and increased activity of caspase-3 and/or caspase-7. Thus, vIRF-3 can be seen as a bona fide oncogene of KSHV-associated lymphoma. Surprisingly, although the related Epstein-Barr virus (EBV) is usually sufficient to immortalize human B lymphocytes, silencing of vIRF-3 reduced the viability of both EBV− and EBV+ PEL cells. This suggests that KSHV is the driving force in the pathogenesis of PEL.
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Krishnamohan, Atmakuri, V. Balaji, and K. Veluthambi. "Efficient vir Gene Induction inAgrobacterium tumefaciens Requires virA,virG, and vir Box from the Same Ti Plasmid." Journal of Bacteriology 183, no. 13 (July 1, 2001): 4079–89. http://dx.doi.org/10.1128/jb.183.13.4079-4089.2001.
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ABSTRACT The vir genes of octopine, nopaline, andl,l-succinamopine Ti plasmids exhibit structural and functional similarities. However, we observed differences in the interactions between octopine and nopalinevir components. The induction of an octopinevirE A6::lacZ fusion (pSM358cd) was 2.3-fold higher in an octopine strain (A348) than in a nopaline strain (C58). Supplementation of the octopinevirG A6 in a nopaline strain with pSM358 did not completely restore virE A6 induction. However, addition of the octopine virA A6 to the above strain increased virE A6 induction to a level almost comparable to that in octopine strains. In a reciprocal analysis, the induction of a nopalinevirE C58::cat fusion (pUCD1553) was two- to threefold higher in nopaline (C58 and T37) strains than in octopine (A348 and Ach5) andl,l-succinamopine (A281) strains. Supplementation of nopaline virA C58 andvirG C58 in an octopine strain (A348) harboring pUCD1553 increased induction levels ofvirE C58::cat fusion to a level comparable to that in a nopaline strain (C58). Our results suggest that octopine and l,l-succinamopine VirG proteins induce the octopine virE A6 more efficiently than they do the nopaline virE C58. Conversely, the nopaline VirG protein induces the nopalinevirE C58 more efficiently than it does the octopine virE A6. The ability of Bo542virG to bring about supervirulence in tobacco is observed for an octopine vir helper (LBA4404) but not for a nopaline vir helper (PMP90). Our analyses reveal that quantitative differences exist in the interactions between VirG and vir boxes of different Ti plasmids. Efficientvir gene induction in octopine and nopaline strains requires virA, virG, andvir boxes from the respective Ti plasmids.
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Hurt, Julie K., Thomas J. McQuade, Anthony Emanuele, Martha J. Larsen, and George A. Garcia. "High-Throughput Screening of the Virulence Regulator VirF." Journal of Biomolecular Screening 15, no. 4 (March 17, 2010): 379–87. http://dx.doi.org/10.1177/1087057110362101.
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Shigella flexneri is a human enteropathogen that infects about 165 million people and claims more than 1 million lives per year worldwide. Although shigellosis has been considered a disease of the “Third World,” like many other contagious diseases, it does occur in developed countries. The emergence of drug and multidrug-resistant strains of Shigella emphasizes the need for novel antibiotic development. VirF, an AraC-type transcriptional regulator, is responsible for the expression of all downstream virulence factors that control intracellular invasion and cell-to-cell spread of Shigella. Gene knockout studies have validated that inhibition of VirF expression is sufficient to block the normal life cycle of Shigella in the host and thereby increase susceptibility to the host immune system. The authors have developed a high-throughput, cell-based assay to monitor inhibition of VirF using β-galactosidase as a reporter protein. Using an avirulent strain of Shigella, they have screened libraries containing ~42,000 small molecules. Following confirmation and dose-response analysis, they have identified 7 compounds that demonstrate VirF inhibition in vivo ≥55% in comparison with the controls and little general antibacterial activity (measured by cell growth, OD600). The authors are in the process of confirming these “hits” in several secondary assays to assess the mechanism of action.
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Mitobe, Jiro, Eiji Arakawa, and Haruo Watanabe. "A Sensor of the Two-Component System CpxA Affects Expression of the Type III Secretion System through Posttranscriptional Processing of InvE." Journal of Bacteriology 187, no. 1 (January 1, 2005): 107–13. http://dx.doi.org/10.1128/jb.187.1.107-113.2005.
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ABSTRACT The chief function of the Cpx two-component system is perceiving various cell envelope stresses, but CpxR is also known to regulate the expression of the type III secretion system (TTSS) of Shigella sonnei through transcription of the primary regulator virF. Here, we have isolated novel cpxA mutants that exhibited decreased TTSS expression from Escherichia coli HW1273, which carries the virulence plasmid of S. sonnei. The cpxA deletion strain of HW1273 expressed β-galactosidase activity levels from the virF-lacZ fusion similar to those of HW1273. However, the second regulator InvE (VirB) and the TTSS component IpaB proteins were apparently expressed at a low level. In the cpxA strain, β-galactosidase activity levels from the invE-lacZ transcriptional fusion remained similar to those of HW1273, whereas the β-galactosidase activity level from the translational fusion of invE-lacZ was reduced to 21% of that of HW1273. Therefore, the deletion of the cpxA gene influenced TTSS expression chiefly at the posttranscriptional processing of InvE. In addition, the cpxA deletion strain of S. sonnei showed the same phenotype. These results indicate that the Cpx two-component system is involved in virulence expression through posttranscriptional processing of the regulatory protein InvE, a novel feature of the Cpx two-component system in posttranscriptional processing and virulence expression of Shigella.
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Berlutti, Francesca, Mariassunta Casalino, Carlo Zagaglia, Piera Assunta Fradiani, Paolo Visca, and Mauro Nicoletti. "Expression of the Virulence Plasmid-Carried Apyrase Gene (apy) of Enteroinvasive Escherichia coli andShigella flexneri Is under the Control of H-NS and the VirF and VirB Regulatory Cascade." Infection and Immunity 66, no. 10 (October 1, 1998): 4957–64. http://dx.doi.org/10.1128/iai.66.10.4957-4964.1998.
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ABSTRACT The transcription of the virulence plasmid (pINV)-carried invasion genes of Shigella flexneri and enteroinvasiveEscherichia coli (EIEC) is induced at 37°C and repressed at 30°C. In this work, we report that the O135: K−:H− EIEC strain HN280 and S. flexneri SFZM53, M90T, and 454, of serotypes 4, 5, and 2a, respectively, produce apyrase (ATP-diphosphohydrolase), the product of the apy gene. In addition, the S. flexneri strains, but not the EIEC strain, produce a nonspecific phosphatase encoded by the phoN-Sfgene. Both apy and phoN-Sf are pINV-carried loci whose contribution to the pathogenicity of enteroinvasive microorganisms has been hypothesized but not yet established. We found that, like that of virulence genes, the expression of both theapy and the phoN-Sf genes was temperature regulated. Strain HN280/32 (a pINV-integrated avirulent derivative of HN280 which has a severe reduction of virB transcription) expressed the apy gene in a temperature-regulated fashion but to a much lower extent than wild-type HN280, while the introduction of the Δhns deletion in HN280 and in HN280/32 induced the wild-type temperature-independent expression of apyrase. These results indicated that a reduction of virB transcription, which is known to occur in the pINV-integrated strain HN280/32, accounts for reduced apyrase expression and that the histone-like protein H-NS is involved in this regulatory network. Independent spontaneously generated mutants of HN280 and of SFZM53 which had lost the capacity to bind Congo red dye (Crb−) were isolated, and the molecular alterations of pINV were evaluated by PCR analysis. Alterations of pINV characterized by the absence of virF or virBand by the presence of the intact apy locus or intactapy and phoN-Sf loci were detected among Crb− mutants of HN280 and SFZM53, respectively. While all Crb− apy + mutants of HN280 failed to produce apyrase, Crb− apy+phoN-Sf + mutants of SFZM53 lacked apyrase activity but produced a nonspecific phosphatase, like parental SFZM53. Moreover, the introduction of recombinant plasmids carrying clonedvirF (pMYSH6504) or virB (pBN1) into Crb− mutants of HN280 and SFZM53 lacking virFor virB, respectively, fully restored temperature-dependent apyrase expression to levels resembling those of the parental strains. Taken together, our results demonstrate that, as has already been shown for invasion genes, apy is another locus whose expression is controlled by temperature, H-NS, and the VirF and VirB regulatory cascade. In contrast, the temperature-regulated expression of the nonspecific phosphatase does not appear to be under the control of the same regulatory network. These findings led us to speculate that apyrase may play a role in the pathogenicity of enteroinvasive bacteria.
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Lopes, Amanda de Oliveira, Pedro do Nascimento Marinho, Letícia d’Ambrosio de Souza Medeiros, and Vanessa Salete de Paula. "Human Gammaherpesvirus 8 Oncogenes Associated with Kaposi’s Sarcoma." International Journal of Molecular Sciences 23, no. 13 (June 29, 2022): 7203. http://dx.doi.org/10.3390/ijms23137203.
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Kaposi’s sarcoma-associated herpesvirus (KSHV), also known as human gammaherpesvirus 8 (HHV-8), contains oncogenes and proteins that modulate various cellular functions, including proliferation, differentiation, survival, and apoptosis, and is integral to KSHV infection and oncogenicity. In this review, we describe the most important KSHV genes [ORF 73 (LANA), ORF 72 (vCyclin), ORF 71 or ORFK13 (vFLIP), ORF 74 (vGPCR), ORF 16 (vBcl-2), ORF K2 (vIL-6), ORF K9 (vIRF 1)/ORF K10.5, ORF K10.6 (vIRF 3), ORF K1 (K1), ORF K15 (K15), and ORF 36 (vPK)] that have the potential to induce malignant phenotypic characteristics of Kaposi’s sarcoma. These oncogenes can be explored in prospective studies as future therapeutic targets of Kaposi’s sarcoma.
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Tang, Hongsheng, Tianlong Zhang, Xiaofeng Yang, and Hua Li. "Classification of different types of slag samples by laser-induced breakdown spectroscopy (LIBS) coupled with random forest based on variable importance (VIRF)." Analytical Methods 7, no. 21 (2015): 9171–76. http://dx.doi.org/10.1039/c5ay02208h.
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A LIBS technique coupled with random forest based on variable importance (VIRF) was presented for the classification analysis of slag samples (open-hearth furnace slag, converter slag and high titanium slag).
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Kalogeraki, Virginia S., and Stephen C. Winans. "Wound-Released Chemical Signals May Elicit Multiple Responses from an Agrobacterium tumefaciens Strain Containing an Octopine-Type Ti Plasmid." Journal of Bacteriology 180, no. 21 (November 1, 1998): 5660–67. http://dx.doi.org/10.1128/jb.180.21.5660-5667.1998.
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ABSTRACT The vir regions of octopine-type and nopaline-type Ti plasmids direct the transfer of oncogenic T-DNA fromAgrobacterium tumefaciens to the nuclei of host plant cells. Previous studies indicate that at least two genetic loci at the left ends of these two vir regions are sufficiently conserved to form heteroduplexes visible in the electron microscope. To initiate an investigation of these genetic loci, we determined the DNA sequences of these regions of both Ti plasmids and identified both conserved loci. One of these is the 2.5-kbvirH locus, which was previously identified on the octopine-type Ti plasmid but thought to be absent from the nopaline-type Ti plasmid. The virH operon contains two genes that resemble P-450-type monooxygenases. The other locus encodes a 0.5-kb gene designated virK. In addition, we identified other potential genes in this region that are not conserved between these two plasmids. To determine (i) whether these genes are members of the vir regulon and, (ii) whether they are required for tumorigenesis, we used a genetic technique to disrupt each gene and simultaneously fuse its promoter to lacZ. Expression of these genes was also measured by nuclease S1 protection assays. virK and two nonconserved genes, designatedvirL and virM, were strongly induced by thevir gene inducer acetosyringone. Disruptions ofvirH, virK, virL, orvirM did not affect tumorigenesis ofKalanchöe diagramontiana leaves or carrot disks, suggesting that they may play an entirely different role during pathogenesis.
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Ueda, Keiji, Kayo Ishikawa, Ken Nishimura, Shuhei Sakakibara, Eunju Do, and Koichi Yamanishi. "Kaposi's Sarcoma-Associated Herpesvirus (Human Herpesvirus 8) Replication and Transcription Factor Activates the K9 (vIRF) Gene through Two Distinct cis Elements by a Non-DNA-Binding Mechanism." Journal of Virology 76, no. 23 (December 1, 2002): 12044–54. http://dx.doi.org/10.1128/jvi.76.23.12044-12054.2002.
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ABSTRACT The replication and transcription activator (RTA) of Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, a homologue of Epstein-Barr virus BRLF1 or Rta, is a strong transactivator and inducer of lytic replication. RTA acting alone can induce lytic replication of KSHV in infected cell lines that originated from primary effusion lymphomas, leading to virus production. During the lytic replication process, RTA activates many kinds of genes, including polyadenylated nuclear RNA, K8, K9 (vIRF), ORF57, and so on. We focused here on the mechanism of how RTA upregulates the K9 (vIRF) promoter and identified two independent cis-acting elements in the K9 (vIRF) promoter that responded to RTA. These elements were finally confined to the sequence 5′-TCTGGGACAGTC-3′ in responsive element (RE) I-2B and the sequence 5′-GTACTTAAAATA-3′ in RE IIC-2, both of which did not share sequence homology. Multiple factors bound specifically with these elements, and their binding was correlated with the RTA-responsive activity. Electrophoretic mobility shift assay with nuclear extract from infected cells and the N-terminal part of RTA expressed in Escherichia coli, however, did not show that RTA interacted directly with these elements, in contrast to the RTA responsive elements in the PAN/K12 promoter region, the ORF57/K8 promoter region. Thus, it was likely that RTA could transactivate several kinds of unique cis elements without directly binding to the responsive elements, probably through cooperation with other DNA-binding factors.
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Broach, William H., Nicholas Egan, Helen J. Wing, Shelley M. Payne, and Erin R. Murphy. "VirF-Independent Regulation of Shigella virB Transcription is Mediated by the Small RNA RyhB." PLoS ONE 7, no. 6 (June 11, 2012): e38592. http://dx.doi.org/10.1371/journal.pone.0038592.
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Lu, Michael, Jacqueline Suen, Carolina Frias, Ruth Pfeiffer, Mong-Hsun Tsai, Eric Chuang, and Steven L. Zeichner. "Dissection of the Kaposi's Sarcoma-Associated Herpesvirus Gene Expression Program by Using the Viral DNA Replication Inhibitor Cidofovir." Journal of Virology 78, no. 24 (December 15, 2004): 13637–52. http://dx.doi.org/10.1128/jvi.78.24.13637-13652.2004.
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ABSTRACT Treatment of primary effusion lymphoma cells latently infected by Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus-8 [HHV-8]) with agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA) induces a lytic viral replication cycle, with an ordered gene expression program. Initial studies of the KSHV expression program following TPA induction using viral microarrays yielded useful information concerning the viral expression program, but precise kinetic assignments for some genes remained unclear. Classically, late herpesvirus genes require viral DNA replication for maximal expression. We used cidofovir (CDV), a nucleotide-analogue KSHV DNA polymerase inhibitor, to dissect KSHV expression into two components: genes expressed without viral DNA replication and those requiring it. The expression of known immediate-early or early genes (e.g., open reading frames [ORFs] 50, K8 bZIP, and 57) serving lytic regulatory roles was relatively unaffected by the presence of CDV, while known late capsid and tegument structural genes (e.g., ORFs 25, 26, 64, and 67) were CDV sensitive. Latency-associated transcript ORF 73 was unaffected by the presence of TPA or CDV, suggesting that it was constitutively expressed. Expression of several viral cellular gene homologs, including K2 (vIL-6), ORF 72 (vCyclin), ORF 74 (vGPCR), and K9 (vIRF-1), was unaffected by the presence of CDV, while that of others, such as K4.1 (vMIP-III), K11.1 (vIRF-2), and K10.5 (LANA2, vIRF-3), was inhibited. The results distinguish KSHV genes whose full expression required viral DNA replication from those that did not require it, providing additional insights into KSHV replication and pathogenesis strategies and helping to show which viral cell homologs are expressed at particular times during the lytic process.
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Niskanen, Taina, Jonas Waldenström, Maria Fredriksson-Ahomaa, Björn Olsen, and Hannu Korkeala. "virF-Positive Yersinia pseudotuberculosis and Yersinia enterocolitica Found in Migratory Birds in Sweden." Applied and Environmental Microbiology 69, no. 8 (August 2003): 4670–75. http://dx.doi.org/10.1128/aem.69.8.4670-4675.2003.
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ABSTRACT During spring and autumn migrations, 468 fecal samples from 57 different species of migratory birds were collected in Sweden. In total, Yersinia spp. were isolated from 12.8% of collected samples. The most commonly found species was Yersinia enterocolitica, which was isolated from 5.6% of all collected samples, followed by Y. intermedia (3.8%), Y. frederiksenii (3.0%), Y. kristensenii (0.9%), Y. pseudotuberculosis (0.6%), and Y. rohdei (0.4%). The pathogenic, virF-positive Y. pseudotuberculosis strains were recovered from three thrushes. These strains belonged to the same bioserotype, 1/O:2, but had two different profiles as determined by pulsed-field gel electrophoresis with NotI and SpeI enzymes. In addition, 10 Y. enterocolitica strains, all from barnacle geese, belonged to bioserotype 3/O:3, which is associated with human disease. Two of the strains were pathogenic, carrying the virF gene on their plasmids. All pathogenic Y. pseudotuberculosis and Y. enterocolitica strains were recovered during the spring, and as the birds were caught during active migration they likely became infected at an earlier stage of the migration, thus potentially transporting these bacterial pathogens over long geographical distances.
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Lohrke, Scott M., Hongjiang Yang, and Shouguang Jin. "Reconstitution of Acetosyringone-Mediated Agrobacterium tumefaciens Virulence Gene Expression in the Heterologous Host Escherichia coli." Journal of Bacteriology 183, no. 12 (June 15, 2001): 3704–11. http://dx.doi.org/10.1128/jb.183.12.3704-3711.2001.
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ABSTRACT The ability to utilize Escherichia coli as a heterologous system in which to study the regulation ofAgrobacterium tumefaciens virulence genes and the mechanism of transfer DNA (T-DNA) transfer would provide an important tool to our understanding and manipulation of these processes. We have previously reported that the rpoA gene encoding the alpha subunit of RNA polymerase is required for the expression of lacZ gene under the control of virB promoter (virBp::lacZ) in E. colicontaining a constitutively active virG gene [virG(Con)]. Here we show that an RpoA hybrid containing the N-terminal 247 residues from E. coli and the C-terminal 89 residues from A. tumefaciens was able to significantly express virBp::lacZ in E. coli in a VirG(Con)-dependent manner. Utilization oflac promoter-driven virA and virGin combination with the A. tumefaciens rpoA construct resulted in significant inducer-mediated expression of thevirBp::lacZ fusion, and the level ofvirBp::lacZ expression was positively correlated to the copy number of the rpoA construct. This expression was dependent on VirA, VirG, temperature, and, to a lesser extent, pH, which is similar to what is observed in A. tumefaciens. Furthermore, the effect of sugars on virgene expression was observed only in the presence of thechvE gene, suggesting that the glucose-binding protein ofE. coli, a homologue of ChvE, does not interact with the VirA molecule. We also evaluated other phenolic compounds in induction assays and observed significant expression with syringealdehyde, a low level of expression with acetovanillone, and no expression with hydroxyacetophenone, similar to what occurs in A. tumefaciens strain A348 from which the virA clone was derived. These data support the notion that VirA directly senses the phenolic inducer. However, the overall level of expression of thevir genes in E. coli is less than what is observed in A. tumefaciens, suggesting that additional gene(s) from A. tumefaciens may be required for the full expression of virulence genes in E. coli.
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Lee, Hye-Ra, Zsolt Toth, Young C. Shin, Jong-Soo Lee, Heesoon Chang, Wei Gu, Tae-Kwang Oh, Myung Hee Kim, and Jae U. Jung. "Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor 4 Targets MDM2 To Deregulate the p53 Tumor Suppressor Pathway." Journal of Virology 83, no. 13 (April 15, 2009): 6739–47. http://dx.doi.org/10.1128/jvi.02353-08.
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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.
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Bleves, Sophie, Marie-Noëlle Marenne, Gautier Detry, and Guy R. Cornelis. "Up-Regulation of the Yersinia enterocolitica yop Regulon by Deletion of the Flagellum Master Operon flhDC." Journal of Bacteriology 184, no. 12 (June 15, 2002): 3214–23. http://dx.doi.org/10.1128/jb.184.12.3214-3223.2002.
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ABSTRACT The Yop virulon enables extracellularly located Yersinia, in close contact with a eukaryotic target cell, to inject bacterial toxic proteins directly into the cytosol of this cell. Several Ysc proteins, forming the Yop secretion apparatus, display homology with proteins of the flagellar basal body. To determine whether this relationship could extend to the regulatory pathways, we analyzed the influence of flhDC, the master regulatory operon of the flagellum, on the yop regulon. In an flhDC mutant, the yop regulon was up-regulated. The transcription of virF and the steady-state level of the transcriptional activator VirF were enhanced. yop transcription was increased at 37°C and could also be detected at a low temperature. Yop secretion was increased at 37°C and occurred even at a low temperature. The Ysc secretion machinery was thus functional at room temperature in the absence of flagella, implying that in wild-type bacteria, FlhD and/or FlhC, or the product of a gene downstream of flhDC, represses the yop regulon. In agreement with this notion, increased expression of flhDC in wild-type bacteria resulted in the oversecretion of flagellins at room temperature and in decreased Yop secretion at 37°C.
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Bragança, Gabriel Godofredo Fiuza de, Marcelo De Sales Pessoa, and Katia Rocha. "Intervenções Regulatórias, Volatilidade e Contágio: Uma Análise VIRF." Brazilian Review of Finance 12, no. 3 (July 10, 2014): 385. http://dx.doi.org/10.12660/rbfin.v12n3.2014.23255.
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This paper examines how regulatory interventions can affect the market risk of electricity utilities and telecom carriers traded in the Brazilian stock market (BOVESPA). Our article uses a bivariate Generalized AutoRegressive Conditional Heteroskedasticity (GARCH - BEKK) model to analyze the impact of two relevant and surprising measures taken by the correspondent Brazilian regulatory authorities in 2012 (one in each sector) on both markets’ volatilities and covariance. We also adopt the volatility impulse response function (VIRF) developed by Hafner & Herwartz (2006) to estimate their persistence. On the one hand, the results indicate that the effects of the telecommunications’ regulatory intervention are negligible but, on the other hand, the impact of the electricity's regulatory measure is significant, long-lasting and contagious.
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WEAGANT, STEPHEN D., JAMES A. JAGOW, KAREN C. JINNEMAN, CURTIS J. OMIECINSKI, CHARLES A. KAYSNER, and WALTER E. HILL. "Development of Digoxigenin-Labeled PCR Amplicon Probes for Use in the Detection and Identification of Enteropathogenic Yersinia and Shiga Toxin–Producing Escherichia coli from Foods." Journal of Food Protection 62, no. 5 (May 1, 1999): 438–43. http://dx.doi.org/10.4315/0362-028x-62.5.438.
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By including digoxigenin-11-dUTP in a polymerase chain reaction (PCR), amplification products were produced that contained nonisotopic markers for use as DNA hybridization probes. Because these labeled amplicons encode pathogenic traits for specific foodborne bacteria, they can be used to detect the presence of potentially virulent organisms that may be present in foods. This technology allows the synthesis of a variety of shelf-stable probe reagents for detecting a number of foodborne microbes of public health concern. We used this technology to detect four genes in two potential pathogens: virF and yadA in enteropathogenic Yersinia and stx1 and stx2 in Shiga-like toxin–producing Escherichia coli. Results of DNA hybridizations of dot blots of 68 Yersinia strains and 24 of 25 E. coli strains were consistent with results of equivalent PCR analyses. DNA colony hybridization with nonisotopic virF probes of colonies arising on spread plates from artificially contaminated food homogenates was able to detect potentially pathogenic Y. enterocolitica. When compared with oligonucleotide probes, amplicon probes are much less sensitive to changes in hybridization and wash temperatures, allowing greater reproducibility. Labeled probe preparations were reused more than five times and have been stored at −20°C for more than 8 months. This method conveniently generates probes that are safe, stable, inexpensive, reusable, and reliable.
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Tornesello, Maria Lina, Clorinda Annunziata, Anna Lucia Tornesello, Luigi Buonaguro, and Franco Maria Buonaguro. "Human Oncoviruses and p53 Tumor Suppressor Pathway Deregulation at the Origin of Human Cancers." Cancers 10, no. 7 (June 22, 2018): 213. http://dx.doi.org/10.3390/cancers10070213.
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Viral oncogenesis is a multistep process largely depending on the complex interplay between viruses and host factors. The oncoviruses are capable of subverting the cell signaling machinery and metabolic pathways and exploit them for infection, replication, and persistence. Several viral oncoproteins are able to functionally inactivate the tumor suppressor p53, causing deregulated expression of many genes orchestrated by p53, such as those involved in apoptosis, DNA stability, and cell proliferation. The Epstein–Barr virus (EBV) BZLF1, the high-risk human papillomavirus (HPV) E6, and the hepatitis C virus (HCV) NS5 proteins have shown to directly bind to and degrade p53. The hepatitis B virus (HBV) HBx and the human T cell lymphotropic virus-1 (HTLV-1) Tax proteins inhibit p53 activity through the modulation of p300/CBP nuclear factors, while the Kaposi’s sarcoma herpesvirus (HHV8) LANA, vIRF-1 and vIRF-3 proteins have been shown to destabilize the oncosuppressor, causing a decrease in its levels in the infected cells. The large T antigen of the Merkel cell polyomavirus (MCPyV) does not bind to p53 but significantly reduces p53-dependent transcription. This review describes the main molecular mechanisms involved in the interaction between viral oncoproteins and p53-related pathways as well as in the development of therapeutic strategies targeting such interactions.
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Simonová, J., M. Vázlerová, and I. Steinhauserová. "Detection of pathogenic Yersinia enterocolitica serotype O:3 by biochemical, serological, and PCR methods." Czech Journal of Food Sciences 25, No. 4 (January 7, 2008): 214–20. http://dx.doi.org/10.17221/686-cjfs.
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In this study, the pathogenic <i>Y. enterocolitica</i> of serotype O:3 was monitored. The serotype is widely spread in Europe and has been linked to human yersiniosis. For the detection of pathogenic strains were used biochemical and serological methods as well as PCR methods based on the identification of virulence genes (<i>ail</i>, <i>rfbC</i>, <i>ystA</i>, <i>yadA</i>, <i>virF</i>). The occurrence of <i>Y. enterocolitica</i> O:3 strains was monitored in slaughter animals from a number of farms in the Czech Republic. A total of 3748 samples were collected coming from pigs (1388), cattle (633), poultry (902), and slaughter facilities (825). Fifty-two <i>Y. enterocolitica</i> O:3 isolates were identified by biochemical and serologic methods, and 53 <i>Y. enterocolitica</i> O:3 isolates were identified by PCR methods (46 isolates from pigs, 2 isolates from poultry, 3 isolates from cattle, and 2 isolates from a poultry slaughtering facility). All isolates of <i>Y. enterocolitica</i> O:3 carried genes <i>ail</i> and <i>rfbC</i>, 83% isolates carried gene <i>ystA</i>, 79% isolates carried gene <i>yadA</i> and 49% isolates carried gene <i>virF</i>. The use of PCR methods based on the identification of <i>ail</i> and <i>rfbC</i> genes provides for a sufficiently specific identification of pathogenic <i>Y. enterocolitica</i> O:3 strains with optimum time consumption compared to biochemical and serological methods. It is not recommendable to use other PCR methods (detection of the <i>ystA, <i>yadA</i>, and <i>virF</i> genes) for the detection of pathogenic <i>Y. enterocolitica</i> strains because those methods are not very specific for the determination of pathogenicity.
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García-Cano, Elena, Hagit Hak, Shimpei Magori, Sondra G. Lazarowitz, and Vitaly Citovsky. "The Agrobacterium F-Box Protein Effector VirF Destabilizes the Arabidopsis GLABROUS1 Enhancer/Binding Protein-Like Transcription Factor VFP4, a Transcriptional Activator of Defense Response Genes." Molecular Plant-Microbe Interactions® 31, no. 5 (May 2018): 576–86. http://dx.doi.org/10.1094/mpmi-07-17-0188-fi.
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Agrobacterium-mediated genetic transformation not only represents a technology of choice to genetically manipulate plants, but it also serves as a model system to study mechanisms employed by invading pathogens to counter the myriad defenses mounted against them by the host cell. Here, we uncover a new layer of plant defenses that is targeted by A. tumefaciens to facilitate infection. We show that the Agrobacterium F-box effector VirF, which is exported into the host cell, recognizes an Arabidopsis transcription factor VFP4 and targets it for proteasomal degradation. We hypothesize that VFP4 resists Agrobacterium infection and that the bacterium utilizes its VirF effector to degrade VFP4 and thereby mitigate the VFP4-based defense. Indeed, loss-of-function mutations in VFP4 resulted in differential expression of numerous biotic stress–response genes, suggesting that one of the functions of VFP4 is to control a spectrum of plant defenses, including those against Agrobacterium tumefaciens. We identified one such gene, ATL31, known to mediate resistance to bacterial pathogens. ATL31 was transcriptionally repressed in VFP4 loss-of-function plants and activated in VFP4 gain-of-function plants. Gain-of-function lines of VFP4 and ATL31 exhibited recalcitrance to Agrobacterium tumorigenicity, suggesting that A. tumefaciens may utilize the host ubiquitin/proteasome system to destabilize transcriptional regulators of the host disease response machinery.
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Lucero-Estrada, Cecilia S. M., José Miguel Soria, Gabriela Isabel Favier, and María Esther Escudero. "Evaluation of the pathogenic potential, antimicrobial susceptibility, and genomic relations of Yersinia enterocolitica strains from food and human origin." Canadian Journal of Microbiology 61, no. 11 (November 2015): 851–60. http://dx.doi.org/10.1139/cjm-2015-0391.
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Yersinia enterocolitica is a food-borne pathogen that causes gastroenteritis with occasional postinfection sequels. This study was aimed to determinate the pathogenic potential, antimicrobial susceptibility, and genomic relationships of Y. enterocolitica strains of different bioserotypes (B/O) isolated from foods and human samples in San Luis, Argentina. Strains obtained by culture were bioserotyped and characterized by phenotypic and genotypic virulence markers, antimicrobial susceptibility, and pulsed-field gel electrophoresis (PFGE). Yersinia enterocolitica was detected in 9.2% of 380 samples, with a distribution of 10.6% (30/284) for food products and 5.2% (5/96) for human samples. Regarding the pathogenic potential, B1A strains of different serotypes were virF– ail–, of which 72.0% (13/18) were ystB+ with virulence-related phenotypic characteristics. Among B2/O:9 isolates, 75.0% (9/12) exhibited the genotype virF+ ail+ ystB– along with phenotypic traits associated with virulence; the same genotype was observed in 80.0% (4/5) of B3/O:3 and B3/O:5 strains. By PFGE, it was possible to separate Y. enterocolitica biotypes into 4 clonal groups (A to D) with 23 genomic types, generating a discriminatory index of 0.96. All isolates were susceptible to antimicrobials used for clinical treatment. This study highlights the presence of pathogenic bioserotypes and the high genomic diversity of the Y. enterocolitica strains isolated in our region.
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Wise, Arlene A., Fang Fang, Yi-Han Lin, Fanglian He, David G. Lynn, and Andrew N. Binns. "The Receiver Domain of Hybrid Histidine Kinase VirA: an Enhancing Factor for vir Gene Expression in Agrobacterium tumefaciens." Journal of Bacteriology 192, no. 6 (January 14, 2010): 1534–42. http://dx.doi.org/10.1128/jb.01007-09.
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ABSTRACT The plant pathogen Agrobacterium tumefaciens expresses virulence (vir) genes in response to chemical signals found at the site of a plant wound. VirA, a hybrid histidine kinase, and its cognate response regulator, VirG, regulate vir gene expression. The receiver domain at the carboxyl end of VirA has been described as an inhibitory element because its removal increased vir gene expression relative to that of full-length VirA. However, experiments that characterized the receiver region as an inhibitory element were performed in the presence of constitutively expressed virG. We show here that VirA's receiver domain is an activating factor if virG is expressed from its native promoter on the Ti plasmid. When virAΔR was expressed from a multicopy plasmid, both sugar and the phenolic inducer were essential for vir gene expression. Replacement of wild-type virA on pTi with virAΔR precluded vir gene induction, and the cells did not accumulate VirG or induce transcription of a virG-lacZ fusion in response to acetosyringone. These phenotypes were corrected if the virG copy number was increased. In addition, we show that the VirA receiver domain can interact with the VirG DNA-binding domain.
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Shimizu, Takeshi, Kensuke Shima, Ken-ichi Yoshino, Kazuyoshi Yonezawa, Tohru Shimizu, and Hideo Hayashi. "Proteome and Transcriptome Analysis of the Virulence Genes Regulated by the VirR/VirS System in Clostridium perfringens." Journal of Bacteriology 184, no. 10 (May 15, 2002): 2587–94. http://dx.doi.org/10.1128/jb.184.10.2587-2594.2002.
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ABSTRACT The proteins under the control of the two-component system VirR/VirS in Clostridium perfringens were analyzed by using two-dimensional gel electrophoresis of the culture supernatant from the wild type and the virR mutant. Based on matrix-assisted laser desorption ionization-time of flight/mass spectrometry, seven positively regulated proteins and eight negatively regulated proteins were identified. Transcriptome analysis confirmed that 7 of the 15 proteins were regulated by the VirR/VirS system at the transcriptional level, but the remaining proteins were modified with a VirR/VirS-directed protease at the posttranslation and secretion levels. We purified and characterized the VirR/VirS-directed protease from the culture supernatant and identified it as a kind of clostripain. Because this proteolytic activity was strongly inhibited by leupeptin and antipain, it was concluded that this protease was a member of the family of cysteine proteases of C. perfringens.
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Tobe, T., M. Yoshikawa, T. Mizuno, and C. Sasakawa. "Transcriptional control of the invasion regulatory gene virB of Shigella flexneri: activation by virF and repression by H-NS." Journal of Bacteriology 175, no. 19 (1993): 6142–49. http://dx.doi.org/10.1128/jb.175.19.6142-6149.1993.
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