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Roger D Everett - One of the best experts on this subject based on the ideXlab platform.

  • herpes simplex virus type 1 immediate Early Protein icp0 and its isolated ring finger domain act as ubiquitin e3 ligases in vitro
    Journal of Virology, 2002
    Co-Authors: Chris Boutell, Seth Sadis, Roger D Everett
    Abstract:

    Proteasome-dependent degradation of ubiquitinated Proteins plays a key role in many important cellular processes. Ubiquitination requires the E1 ubiquitin activating enzyme, an E2 ubiquitin conjugating enzyme, and frequently a substrate-specific ubiquitin Protein ligase (E3). One class of E3 ubiquitin ligases has been shown to contain a common zinc-binding RING finger motif. We have previously shown that herpes simplex virus type 1 ICP0, itself a RING finger Protein, induces the proteasome-dependent degradation of several cellular Proteins and induces the accumulation of colocalizing conjugated ubiquitin in vivo. We now report that both full-length ICP0 and its isolated RING finger domain induce the accumulation of polyubiquitin chains in vitro in the presence of E1 and the E2 enzymes UbcH5a and UbcH6. Mutations within the RING finger region that abolish the in vitro ubiquitination activity also cause severe reductions in ICP0 activity in other assays. We conclude that ICP0 has the potential to act as an E3 ubiquitin ligase during viral infection and to target specific cellular Proteins for destruction by the 26S proteasome.

  • alphaherpesvirus Proteins related to herpes simplex virus type 1 icp0 induce the formation of colocalizing conjugated ubiquitin
    Journal of Virology, 2001
    Co-Authors: Jane Parkinson, Roger D Everett
    Abstract:

    Herpes simplex virus type 1 immediate Early Protein ICP0 influences virus infection by inducing the degradation of specific cellular Proteins via a mechanism requiring its RING finger and the ubiquitin-proteasome pathway. Many RING finger Proteins, by virtue of their RING finger domain, interact with E2 ubiquitin-conjugating enzymes and act as a component of an E3 ubiquitin ligase. We have recently shown that ICP0 induces the accumulation of colocalizing, conjugated ubiquitin, suggesting that ICP0 can act as or contribute to an E3 ubiquitin ligase. In this report we demonstrate that the ICP0-related RING finger Proteins encoded by other alphaherpesviruses also induce colocalizing, conjugated ubiquitin, thereby suggesting that they act by similar biochemical mechanisms.

H Kida - One of the best experts on this subject based on the ideXlab platform.

  • Promoter activity of sequence located upstream of the pseudorabies virus Early Protein 0 gene.
    Veterinary microbiology, 1998
    Co-Authors: S Watanabe, E Ono, H Nikami, H Kida
    Abstract:

    Promoter activity of the 5'-flanking region of the pseudorabies virus (PRV) Early Protein 0 (EP0) gene was analysed by transient transfection assays employing chloramphenicol acetyl transferase (CAT) reporter constructs. We identified a 213 bp segment of the viral genome that was capable of efficiently driving expression of the EPO gene and a linked reporter gene upon transient transfection into Vero cells. This segment lacked the typical TATA element, and possessed an initiator element and the putative binding sites for the transcription factor Sp1 and immediate-Early Protein IE180, a strong transactivator of PRV. By analysing 5'-deletion mutants of the segment, a 48 bp segment (from nucleotide positions -65 to -17), which possessed three Sp1 binding sites, was identified to be critical for the promoter activity. Cotransfection of Vero cells with the mutant constructs and an IE180 expression plasmid resulted in transactivation of only those constructs in which the Sp1 sites were present. These results indicate that the EP0 gene may be transcribed from the TATA-less promoter that responds to Sp1.

  • Pseudorabies virus (PRV) Early Protein 0 activates PRV gene transcription in combination with the immediate-Early Protein IE180 and enhances the infectivity of PRV genomic DNA.
    Veterinary microbiology, 1998
    Co-Authors: E Ono, S Watanabe, H Nikami, T Tasaki, H Kida
    Abstract:

    Pseudorabies virus (PRV) Early Protein 0 (EP0) functions as a transactivator of the viral gene promoters. In transient expression assays employing chloramphenicol acetyl transferase (CAT) reporter constructs, EP0 and the immediate-Early Protein IE180 act in an additive manner to activate transcription from the thymidine kinase (TK) and glycoProtein G (gG) gene promoters. EP0 enhanced the synthesis of infectious virus in cotransfection experiments with the EP0-expression plasmid and PRV genomic DNA. EP0 was detected by Western blot analysis in the purified virions. These results may indicate that EP0 in the virions acts as an important transactivator to express the immediate-Early gene efficiently in the first stage of infection, and IE180 and EP0 expressed after the infection cooperatively activate the Early and late gene expression in the later stage of infection.

  • Mapping of transregulatory domains of pseudorabies virus Early Protein 0 and identification of its dominant-negative mutant
    Archives of Virology, 1996
    Co-Authors: S. Watanabe, Y. Shimizu, H Kida
    Abstract:

    Pseudorabies virus (PRV) Early Protein 0 (EP0) is a transactivator containing the RING finger domain. Analysis of transactivating activity of truncated forms of the EP0 molecule consisting of 410 amino acids revealed that amino-terminal region containing the RING finger domain, amino acids 1 to 84, and the region between amino acids 114 to 242 containing acidic amino acid sequences were required for the transactivation. On the other hand, the mutant consisting of amino acids 1 to 113 exhibited a dominant-negative property.

  • Mapping of transcriptional regulatory domains of pseudorabies virus immediate-Early Protein.
    Archives of virology, 1994
    Co-Authors: Satoshi Taharaguchi, S Yamada, H Kida, H Inoue, E Ono, Yukio Shimizu
    Abstract:

    The 180 kilodalton immediate-Early Protein (IE180) of pseudorabies virus functions as a strong transactivator of several different promoters and also as a repressor of its own transcription. To map the functional domains of IE180, we prepared various truncated mutants and analyzed their transcriptional regulatory activities using the chloramphenicol acetyl transferase (CAT) assay. Analysis of mutants truncated from the carboxy-terminal end of the 1,460-amino acid polypeptide showed that a polypeptide possessing amino acids 1 to 1,081 retained significant functions of transactivation and autoregulation potential. On the other hand, removing amino acids 1 to 131 resulted in a complete loss of transactivation potential, indicating that the domain responsible for transactivation is located in the amino-terminal end of IE180. Additional amino-terminal truncation up to amino acid 453 did not affect the autoregulation activity, indicating that the region between amino acids 454 and 1081 has autoregulation potential.

Margarita Salas - One of the best experts on this subject based on the ideXlab platform.

  • bacteriophage φ29 Early Protein p17 self association and hetero association with the viral histone like Protein p6
    Journal of Biological Chemistry, 2003
    Co-Authors: Paola Crucitti, Ana M Abril, Margarita Salas
    Abstract:

    Abstract Gene 17 of the Bacillus subtilis phage Φ29 is expressed Early after infection, and it has been shown to be required at the very beginning of phage replication under conditions of low but not high multiplicity of infection. It has been proposed that, at the beginning of the infection, Protein p17 could be recruiting limiting amounts of initiation factors at the viral origins. Once the infection process is established and the replication Proteins reach optimal concentration, Protein p17 becomes dispensable. In this paper we focused, on the one hand, on the study of Protein p17 dimerization and the role of a putative coiled-coil region. On the other hand, we focused on its interaction with the viral origin-binding Protein p6. Based on our results we propose that Protein p17 function is to optimize binding of Protein p6 at the viral DNA ends, thus favoring the initiation of replication and negatively modulating its own transcription.

  • bacteriophage o29 Early Protein p17 is conditionally required for the first rounds of viral dna replication
    Gene, 1998
    Co-Authors: Paola Crucitti, Jose M Lazaro, Vladimir Benes, Margarita Salas
    Abstract:

    Abstract The gene 17 of the Bacillus subtilis phage φ29 is known to be involved in the viral DNA replication in vivo. In this paper, we show that the presence of Protein p17 is required when phage infection occurs at a low multiplicity of infection (moi), which is probably the natural condition for infection, but is dispensable at a high moi. Gene 17 has been cloned in an Escherichia coli expression vector and Protein p17 purified. A stimulatory effect of Protein p17 was demonstrated under in vitro conditions required to amplify φ29 DNA, starting with a low amount of input DNA. We propose that p17, which is synthesized Early after infection, is required at the very beginning of the phage amplification, conditions in which a low number of viral DNA molecules enter the host cell, possibly to recruit the limiting amount of initiation factors at the replication origins. Once the infection process is established and the other replication Proteins reach optimal concentration, p17 becomes dispensable.

  • Bacteriophage phi29 Early Protein p17 is conditionally required for the first rounds of viral DNA replication.
    Gene, 1998
    Co-Authors: Paola Crucitti, Jose M Lazaro, Vladimir Benes, Margarita Salas
    Abstract:

    The gene 17 of the Bacillus subtilis phage phi29 is known to be involved in the viral DNA replication in vivo. In this paper, we show that the presence of Protein p17 is required when phage infection occurs at a low multiplicity of infection (moi), which is probably the natural condition for infection, but is dispensable at a high moi. Gene 17 has been cloned in an Escherichia coli expression vector and Protein p17 purified. A stimulatory effect of Protein p17 was demonstrated under in vitro conditions required to amplify phi29 DNA, starting with a low amount of input DNA. We propose that p17, which is synthesized Early after infection, is required at the very beginning of the phage amplification, conditions in which a low number of viral DNA molecules enter the host cell, possibly to recruit the limiting amount of initiation factors at the replication origins. Once the infection process is established and the other replication Proteins reach optimal concentration, p17 becomes dispensable.

D Guruge - One of the best experts on this subject based on the ideXlab platform.

  • IE63-specific T-cell responses associate with control of subclinical varicella zoster virus reactivation in individuals with malignancies
    British Journal of Cancer, 2010
    Co-Authors: G N Malavige, L T Rohanachandra, L Jones, L Crack, M Perera, N Fernando, D Guruge
    Abstract:

    Background: Reactivation of the varicella zoster virus (VZV) is more common in patients with malignancies; however, the molecular and cellular mechanisms underlying this susceptibility are unclear. Methods: Using ex vivo interferon- γ ELISpot assays, we set out to analyse VZV-specific immune responses in a large cohort of patients with malignancies. Results: We observed that patients with malignancies had impaired VZV-specific T-cell responses, particularly in those with haematological malignancies and breast carcinoma. Immediate-Early Protein 63 (IE63)-specific T-cell responses were significantly impaired in those with subclinical VZV re-activation. Conclusions: Our results suggest that T-cell responses to IE63 are important in controlling VZV replication.

Stephen E. Straus - One of the best experts on this subject based on the ideXlab platform.

  • The cellular transcription factor USF cooperates with varicella-zoster virus immediate-Early Protein 62 to symmetrically activate a bidirectional viral promoter.
    Molecular and Cellular Biology, 1994
    Co-Authors: Jeffery L. Meier, Xu Luo, Michèle Sawadogo, Stephen E. Straus
    Abstract:

    The mechanisms governing the function of cellular USF and herpesvirus immediate-Early transcription factors are subjects of considerable interest. In this regard, we identified a novel form of coordinate gene regulation involving a cooperative interplay between cellular USF and the varicella-zoster virus immediate-Early Protein 62 (IE 62). A single USF-binding site defines the potential level of IE 62-dependent activation of a bidirectional viral Early promoter of the DNA polymerase and major DNA-binding Protein genes. We also report a dominant negative USF-2 mutant lacking the DNA-binding domain that permits the delineation of the biological role of both USF-1 and USF-2 in this activation process. The symmetrical stimulation of the bidirectional viral promoter by IE 62 is achieved at concentrations of USF-1 (43 kDa) or USF-2 (44 kDa) already existing in cells. Our observations support the notion that cellular USF can intervene in and possibly target promoters for activation by a herpesvirus immediate-Early Protein.

  • a major transactivator of varicella zoster virus the immediate Early Protein ie62 contains a potent n terminal activation domain
    Journal of Virology, 1993
    Co-Authors: Liyanage P Perera, Joseph D Mosca, William T Ruyechan, Gary Selwyn Hayward, Stephen E. Straus
    Abstract:

    Abstract Accumulating evidence indicates that the product of the putative immediate-Early gene ORF62 (IE62) activates varicella-zoster virus (VZV) genes thought to represent all three kinetic classes, namely, immediate-Early (alpha), Early (beta), and late (gamma) classes, of VZV genes as well as a variety heterologous gene promoters. However, the mechanism(s) by which IE62 Protein mediates transactivation of these diverse VZV and heterologous gene promoters remains to be elucidated. In this study, by using yeast GAL4 Protein chimeras, the coding regions of VZV ORF62 possessing activation domains have been assessed. We demonstrate that the VZV IE62 Protein contains a potent activation domain in the N-terminal portion of the molecule, encoded within the first 86 codons of ORF62. The predicted secondary structure profile and the acid-base composition of this IE62 domain resemble those of other transregulatory Proteins whose activation is mediated through acidic, hydrophobic elements. In addition, we show that deletion of this activation domain from the 1,310-residue native IE62 Protein results in ablation of the transactivator function of IE62. We also present evidence that the mutant IE62 Protein lacking the activation domain, though devoid of transactivation ability, was still capable of interfering with the activation of target promoters by the native, full-length IE62.