The lytic origin of herpesvirus papio is highly homologous to Epstein-Barr virus ori-Lyt: evolutionary conservation of transcriptional activation and replication signals.

ABSTRACT The mechanistic contribution of the Epstein-Barr virus (EBV) EBNA-LP protein to B-cell immortalization remains an enigma. However, previous studies have indicated that EBNA-LP may contribute to immortalization by enhancing EBNA2-mediated transcriptional activation of the LMP-1 gene. To gain further insight into the potential role EBNA-LP has in EBV-mediated B-cell immortalization, we asked whether it is a global or gene-specific coactivator of EBNA2 and whether coactivation requires interaction between these proteins. In type I Burkitt's lymphoma cells, we found that EBNA-LP strongly coactivated EBNA2 stimulation of LMP-1 and LMP2B RNAs, which are expressed from the viral divergent promoter. Surprisingly, the viral LMP2A gene and cellular CD21 and Hes-1 genes were induced by EBNA2 but showed no further induction after EBNA-LP coexpression. We also found that EBNA-LP did not stably interact with EBNA2 in coimmunoprecipitation assays, even though the conditions were adequate to observe specific interactions between EBNA2 and its cellular cofactor, CBF1. Colocalization between EBNA2 and EBNA-LP was not detectable in EBV-transformed cell lines or transfected type I Burkitt's cells. Finally, no significant interactions between EBNA2 and EBNA-LP were found with mammalian two-hybrid assays. From this data, we conclude that EBNA-LP is not a global coactivator of EBNA2 targets, but it preferentially coactivates EBNA2 stimulation of the viral divergent promoter. While this may require specific transient interactions between these proteins that only occur in the context of the divergent promoter, our data strongly suggest that EBNA-LP also cooperates with EBNA2 through mechanisms that do not require direct or indirect complex formation between these proteins.

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The Epstein-Barr Virus BMRF1 Protein Activates Transcription and Inhibits the DNA Damage Response by Binding NuRD

Journal of Virology ◽

10.1128/jvi.01070-19 ◽

2019 ◽

Vol 93 (22) ◽

Cited By ~ 1

Author(s):

Samuel G. Salamun ◽

Justine Sitz ◽

Carlos F. De La Cruz-Herrera ◽

Jaime Yockteng-Melgar ◽

Edyta Marcon ◽

...

Keyword(s):

Dna Damage ◽

Dna Damage Response ◽

Transcriptional Activation ◽

Epstein Barr Virus ◽

Nurd Complex ◽

Dna Breaks ◽

Nucleosome Remodeling ◽

Barr Virus ◽

Damage Response ◽

Epstein Barr

ABSTRACT The BMRF1 protein of Epstein-Barr virus (EBV) has multiple roles in viral lytic infection, including serving as the DNA polymerase processivity factor, activating transcription from several EBV promoters and inhibiting the host DNA damage response to double-stranded DNA breaks (DSBs). Using affinity purification coupled to mass spectrometry, we identified the nucleosome remodeling and deacetylation (NuRD) complex as the top interactor of BMRF1. We further found that NuRD components localize with BMRF1 at viral replication compartments and that this interaction occurs through the BMRF1 C-terminal region previously shown to mediate transcriptional activation. We identified an RBBP4 binding motif within this region that can interact with both RBBP4 and MTA2 components of the NuRD complex and showed that point mutation of this motif abrogates NuRD binding as well as the ability of BMRF1 to activate transcription from the BDLF3 and BLLF1 EBV promoters. In addition to its role in transcriptional regulation, NuRD has been shown to contribute to DSB signaling in enabling recruitment of RNF168 ubiquitin ligase and subsequent ubiquitylation at the break. We showed that BMRF1 inhibited RNF168 recruitment and ubiquitylation at DSBs and that this inhibition was at least partly relieved by loss of the NuRD interaction. The results reveal a mechanism by which BMRF1 activates transcription and inhibits DSB signaling and a novel role for NuRD in transcriptional activation in EBV. IMPORTANCE The Epstein-Barr virus (EBV) BMRF1 protein is critical for EBV infection, playing key roles in viral genome replication, activation of EBV genes, and inhibition of host DNA damage responses (DDRs). Here we show that BMRF1 targets the cellular nucleosome remodeling and deacetylation (NuRD) complex, using a motif in the BMRF1 transcriptional activation sequence. Mutation of this motif disrupts the ability of BMRF1 to activate transcription and interfere with DDRs, showing the importance of the NuRD interaction for BMRF1 functions. BMRF1 was shown to act at the same step in the DDR as NuRD, suggesting that it interferes with NuRD function.

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LYDMA-antigens and Immunity against EBV-infected Cells Epstein-Barr Virus as a Model for the Study of Host-infection Interaction

The International Journal of Biological Markers ◽

10.1177/172460088700200212 ◽

1987 ◽

Vol 2 (2) ◽

pp. 125-132 ◽

Cited By ~ 2

Author(s):

Maria L. Villa ◽

Emilio Bombardieri

Keyword(s):

Transcriptional Activation ◽

Epstein Barr Virus ◽

Dna Viruses ◽

Barr Virus ◽

Good Potential ◽

Infected Cells ◽

Membrane Antigens ◽

Epstein Barr ◽

Host Infection

Molecular biology has shown that DNA viruses carry their own transforming genes, unlike RNA viruses (retrovirus), which use cellular “oncogenes”. Some of the products of transforming viral genes are very good potential targets for immune defence. Epstein-Barr virus (EBV) immortalization is linked to the transcriptional activation of some latently transcribed regions; the lymphocyte-determined membrane antigens (LYDMA), the product of one of these regions, are the T-cell's chosen target. EBV-induced immortalization may therefore be free from any malignant consequence as long as immortalized clones are suppressed by immunosurveillance. In vivo, LYDMA-positive clones may be susceptible to immune control; LYDMA-negative clones can transform to neoplastic cells

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Epstein-Barr Virus Immediate-Early Protein BRLF1 Induces the Lytic Form of Viral Replication through a Mechanism Involving Phosphatidylinositol-3 Kinase Activation

Journal of Virology ◽

10.1128/jvi.75.13.6135-6142.2001 ◽

2001 ◽

Vol 75 (13) ◽

pp. 6135-6142 ◽

Cited By ~ 69

Author(s):

Catherine Dayle Darr ◽

Amy Mauser ◽

Shannon Kenney

Keyword(s):

Viral Replication ◽

Transcriptional Activation ◽

Epstein Barr Virus ◽

Adenovirus Vector ◽

Pi3 Kinase ◽

Immediate Early ◽

Kinase Activation ◽

Barr Virus ◽

Epstein Barr ◽

Phosphatidylinositol 3

ABSTRACT Expression of the Epstein-Barr virus (EBV) immediate-early (IE) protein BRLF1 induces the lytic form of viral replication in most EBV-positive cell lines. BRLF1 is a transcriptional activator that binds directly to a GC-rich motif present in some EBV lytic gene promoters. However, BRLF1 activates transcription of the other IE protein, BZLF1, through an indirect mechanism which we previously showed to require activation of the stress mitogen-activated protein kinases. Here we demonstrate that BRLF1 activates phosphatidylinositol-3 (PI3) kinase signaling in host cells. We show that the specific PI3 kinase inhibitor, LY294002, completely abrogates the ability of a BRLF1 adenovirus vector to induce the lytic form of EBV infection, while not affecting lytic infection induced by a BZLF1 adenovirus vector. Furthermore, we demonstrate that the requirement for PI3 kinase activation in BRLF1-induced transcriptional activation is promoter dependent. BRLF1 activation of the SM early promoter (which occurs through a direct binding mechanism) does not require PI3 kinase activation, whereas activation of the IE BZLF1 and early BMRF1 promoters requires PI3 kinase activation. Thus, there are clearly two separate mechanisms by which BRLF1 induces transcriptional activation.

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The EBNA1 Protein of Epstein-Barr Virus Functionally Interacts with Brd4

Journal of Virology ◽

10.1128/jvi.01680-08 ◽

2008 ◽

Vol 82 (24) ◽

pp. 12009-12019 ◽

Cited By ~ 68

Author(s):

Ammy Lin ◽

Shan Wang ◽

Tin Nguyen ◽

Kathy Shire ◽

Lori Frappier

Keyword(s):

Transcriptional Activation ◽

Epstein Barr Virus ◽

Mitotic Chromosome ◽

Human Cells ◽

Host Proteins ◽

Enhancer Element ◽

Barr Virus ◽

Chromosome Attachment ◽

Infected Cells ◽

Epstein Barr

ABSTRACT The EBNA1 protein of Epstein-Barr virus (EBV) is essential for EBV latent infection in ensuring the replication and stable segregation of the EBV genomes and in activating the transcription of other EBV latency genes. We have tested the ability of four host proteins (Brd2, Brd4, DEK, and MeCP2) implicated in the segregation of papillomavirus and Kaposi's sarcoma-associated herpesvirus to support EBNA1-mediated segregation of EBV-based plasmids in Saccharomyces cerevisiae. We found that Brd4 enabled EBNA1-mediated segregation while Brd2 and MeCP2 had a general stimulatory effect on plasmid maintenance. EBNA1 interacted with Brd4 in both yeast and human cells through N-terminal sequences previously shown to mediate transcriptional activation but not segregation. In keeping with this interaction site, silencing of Brd4 in human cells decreased transcriptional activation by EBNA1 but not the mitotic chromosome attachment of EBNA1 that is required for segregation. In addition, Brd4 was found to be preferentially localized to the FR enhancer element regulated by EBNA1, over other EBV sequences, in latently EBV-infected cells. The results indicate that EBNA1 can functionally interact with Brd4 in native and heterologous systems and that this interaction facilitates transcriptional activation by EBNA1 from the FR element.

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Epstein-Barr Virus Binding to CD21 Activates the Initial Viral Promoter via NF-κB Induction

Journal of Experimental Medicine ◽

10.1084/jem.186.5.731 ◽

1997 ◽

Vol 186 (5) ◽

pp. 731-737 ◽

Cited By ~ 67

Author(s):

Naoyuki Sugano ◽

Weiping Chen ◽

M. Luisa Roberts ◽

Neil R. Cooper

Keyword(s):

B Cells ◽

Transcriptional Activation ◽

Intracellular Signaling ◽

Epstein Barr Virus ◽

Human Herpesvirus ◽

Virus Binding ◽

Intracellular Signaling Pathway ◽

Barr Virus ◽

Sequence Of Events ◽

Epstein Barr

Epstein-Barr virus (EBV), an oncogenic human herpesvirus, binds to and infects normal human B lymphocytes via CD21, the CR2 complement receptor. Studies of the mechanisms that enable EBV to infect nonactivated, noncycling B cells provide compelling evidence for a sequence of events in which EBV binding to CD21 on purified resting human B cells rapidly activates the NF-κB transcription factor, which, in turn, binds to and mediates transcriptional activation of Wp, the initial viral latent gene promoter. Thus, EBV binding to its cellular receptor on resting B cells triggers an NF-κB–dependent intracellular signaling pathway which is required for infection.

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Marked Variation in Response of Consensus Binding Elements for the Rta Protein of Epstein-Barr Virus

Journal of Virology ◽

10.1128/jvi.79.15.9635-9650.2005 ◽

2005 ◽

Vol 79 (15) ◽

pp. 9635-9650 ◽

Cited By ~ 33

Author(s):

Lee-Wen Chen ◽

Pey-Jium Chang ◽

Henri-Jacques Delecluse ◽

George Miller

Keyword(s):

Dna Sequences ◽

Transcriptional Activation ◽

Mammalian Cells ◽

Epstein Barr Virus ◽

Lytic Cycle ◽

Maximal Response ◽

Binding Affinities ◽

Barr Virus ◽

Epstein Barr

ABSTRACT The R transactivator (Rta) protein activates Epstein-Barr virus (EBV) lytic-cycle genes by several distinct mechanisms that include direct binding to viral promoters, synergy with BamHI Z EBV replication activator (ZEBRA), and activation of cellular signaling pathways. In the direct and synergistic mechanisms of action, Rta binds to specific DNA sequences that are present in the promoters of responsive genes. It has been difficult to demonstrate the capacity of Rta expressed in mammalian cells to bind DNA in vitro in order to study the relative affinities of Rta binding elements. We discovered that a short C-terminal region of Rta inhibits the ability of Rta to bind DNA in vitro. C-terminally truncated versions of Rta bind DNA efficiently and thus facilitate a comparison of consensus Rta binding elements (CRBEs) found in promoters of five Rta-responsive genes: BMLF1, BHLF1, BMRF1, BaRF1, and BLRF2. All CRBEs in the promoters of the five genes conform to the proposed recognition sequence GNCCN9GGNG, where N is any nucleotide and N9 represents a sequence of nine nucleotides. Nonetheless, CRBEs varied markedly in their abilities to bind Rta in electrophoretic mobility shift assays. Not all CRBEs bound or responded to Rta. Binding affinities of the CRBEs and the capacity to be activated by Rta in reporter assays were strongly correlated. The CRBEs from the BMLF1 and BHLF1 promoters conferred the greatest response. The response of the BMRF1, BaRF1, and BLRF2 CRBEs was less robust. By creation of chimeras, inversions, and point mutations, differences in binding affinities and transcriptional activation levels could be attributed to N9 sequence variation. The length of N9 was also critical for a maximal response. In Raji and BZLF1-knockout cells, the mRNAs of the five Rta-responsive lytic-cycle genes differed dramatically in kinetics of expression, abundance, and synergistic responses to ZEBRA and Rta. Affinities of Rta response elements for Rta are likely to play an important role in temporal regulation and the level of lytic-cycle EBV gene expression.

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IRF-7, a new interferon regulatory factor associated with Epstein-Barr virus latency.

Molecular and Cellular Biology ◽

10.1128/mcb.17.10.5748 ◽

1997 ◽

Vol 17 (10) ◽

pp. 5748-5757 ◽

Cited By ~ 190

Author(s):

L Zhang ◽

J S Pagano

Keyword(s):

Transcriptional Activation ◽

Epstein Barr Virus ◽

Nuclear Antigen ◽

Type I ◽

Blood Leukocytes ◽

Type Iii ◽

Barr Virus ◽

Virus Latency ◽

Restricted Type ◽

Epstein Barr

The Epstein-Barr virus (EBV) BamHI Q promoter (Qp) is the only promoter used for the transcription of Epstein-Barr virus nuclear antigen 1 (EBNA-1) mRNA in cells in the most restricted (type I) latent infection state. However, Qp is inactive in type III latency. With the use of the yeast one-hybrid system, a new cellular gene has been identified that encodes proteins which bind to sequence in Qp. The deduced amino acid sequence of the gene has significant homology to the interferon regulatory factors (IRFs). This new gene and products including two splicing variants are designated IRF-7A, IRF-7B, and IRF-7C. The expression of IRF-7 is predominantly in spleen, thymus, and peripheral blood leukocytes (PBL). IRF-7 proteins were identified in primary PBL with specific antiserum against IRF-7B protein. IRF-7s can bind to interferon-stimulated response element (ISRE) sequence and repress transcriptional activation by both interferon and IRF-1. Additionally, a functional viral ISRE sequence, 5'-GCGAAAACGAAAGT-3', has been identified in Qp. Finally, the expression of IRF-7 is consistently high in type III latency cells and almost undetectable in type I latency, corresponding to the activity of endogenous Qp in these latency states and the ability of the IRF-7 proteins to repress Qp-reporter constructs. The identification of a functional viral ISRE and association of IRF-7 with type III latency may be relevant to the mechanism of regulation of Qp.

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