Initial Characterization of the Epstein–Barr Virus BSRF1 Gene Product

Epstein–Barr virus (EBV) is a ubiquitous virus that causes infectious mononucleosis and several types of cancer, such as Burkitt lymphoma, T/NK-cell lymphoma, and nasopharyngeal carcinoma. As a herpesvirus, it encodes more than 80 genes, many of which have not been characterized. EBV BamHI S rightward reading frame 1 (BSRF1) encodes a tegument protein that, unlike its homologs herpes simplex virus unique long 51 (UL51) and human cytomegalovirus UL71, has not been extensively investigated. To examine the role of BSRF1, we prepared knockout and revertant strains using the bacterial artificial chromosome system. Unexpectedly, the disruption of the gene had little or no effect on EBV lytic replication and the transformation of primary B cells. However, the knockdown of BSRF1 in B95-8 cells decreased progeny production. An immunofluorescence assay revealed that BSRF1 localized to the Golgi apparatus in the cytoplasm, as did its homologs. BSRF1 also associated with BamHI G leftward reading frame 3.5 (BGLF3.5), BamHI B rightward reading frame 2 (BBRF2), and BamHI A leftward reading frame 1 (BALF1), and BALF1 was incorporated into the tegument fraction with BSRF1. Taken together, our results indicate that BSRF1 plays a role in secondary envelopment or virion egress in the cytoplasm, as do its homolog genes.

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Characterization and Intracellular Trafficking of Epstein-Barr Virus BBLF1, a Protein Involved in Virion Maturation

Journal of Virology ◽

10.1128/jvi.01126-12 ◽

2012 ◽

Vol 86 (18) ◽

pp. 9647-9655 ◽

Cited By ~ 24

Author(s):

Ya-Fang Chiu ◽

Bill Sugden ◽

Pey-Jium Chang ◽

Lee-Wen Chen ◽

Ying-Ju Lin ◽

...

Keyword(s):

Epstein Barr Virus ◽

Retrograde Transport ◽

Lytic Replication ◽

Herpes Simplex Virus 1 ◽

Virus Particles ◽

Tegument Proteins ◽

Barr Virus ◽

Viral Maturation ◽

Epstein Barr ◽

Simplex Virus

Epstein-Barr virus (EBV) BBLF1 shares 13 to 15% amino acid sequence identities with the herpes simplex virus 1 UL11 and cytomegalovirus UL99 tegument proteins, which are involved in the final envelopment during viral maturation. This study demonstrates that BBLF1 is a myristoylated and palmitoylated protein, as are UL11 and UL99. Myristoylation of BBLF1 both facilitates its membrane anchoring and stabilizes it. BBLF1 is shown to localize to thetrans-Golgi network (TGN) along with gp350/220, a site where final envelopment of EBV particles takes place. The localization of BBLF1 at the TGN requires myristoylation and two acidic clusters, which interact with PACS-1, a cytosolic protein, to mediate retrograde transport from the endosomes to the TGN. Knockdown of the expression of BBLF1 during EBV lytic replication reduces the production of virus particles, demonstrating the requirement of BBLF1 to achieve optimal production of virus particles. BBLF1 is hypothesized to facilitate the budding of tegumented capsid into glycoprotein-embedded membrane during viral maturation.

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The Epstein-Barr Virus BMRF1 Gene Is Essential for Lytic Virus Replication

Journal of Virology ◽

10.1128/jvi.80.10.5078-5081.2006 ◽

2006 ◽

Vol 80 (10) ◽

pp. 5078-5081 ◽

Cited By ~ 31

Author(s):

Bernhard Neuhierl ◽

Henri-Jacques Delecluse

Keyword(s):

Epstein Barr Virus ◽

Lytic Replication ◽

Wild Type ◽

Reading Frame ◽

Barr Virus ◽

Wild Type Phenotype ◽

Late Protein ◽

Processivity Factor ◽

Epstein Barr ◽

Lytic Dna Replication

ABSTRACT The Epstein-Barr virus (EBV) BMRF1 protein is a DNA polymerase processivity factor. We have deleted the BMRF1 open reading frame from the EBV genome and assessed the ΔBMRF1 EBV phenotype. ΔBMRF1 viruses were replication deficient, but the wild-type phenotype could be restored by BMRF1 trans-complementation. The replication-deficient phenotype included impaired lytic DNA replication and late protein expression. ΔBMRF1 and wild-type viruses were undistinguishable in terms of their ability to transform primary B cells. Our results provide genetic evidence that BMRF1 is essential for lytic replication of the EBV genome.

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Pathogenetic role of Epstein-Barr Virus in relation to tumour cell characteristics of nasal T/NK-cell lymphomas

10.5353/th_b3026901 ◽

1997 ◽

Author(s):

Kwok-shing, Alan Chiang

Keyword(s):

Tumour Cell ◽

Epstein Barr Virus ◽

Nk Cell ◽

Pathogenetic Role ◽

Barr Virus ◽

Epstein Barr

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Induction of the Lytic Cycle Sensitizes Epstein-Barr Virus-Infected B Cells to NK Cell Killing That Is Counteracted by Virus-Mediated NK Cell Evasion Mechanisms in the Late Lytic Cycle

Journal of Virology ◽

10.1128/jvi.01932-15 ◽

2015 ◽

Vol 90 (2) ◽

pp. 947-958 ◽

Cited By ~ 14

Author(s):

Luke R. Williams ◽

Laura L. Quinn ◽

Martin Rowe ◽

Jianmin Zuo

Keyword(s):

B Cells ◽

Nk Cells ◽

Epstein Barr Virus ◽

Nk Cell ◽

Cell Killing ◽

Lytic Replication ◽

Lytic Cycle ◽

Barr Virus ◽

Infected Cells ◽

Epstein Barr

ABSTRACTEpstein-Barr Virus (EBV) persists for the lifetime of the infected host despite eliciting strong immune responses. This persistence requires a fine balance between the host immune system and EBV immune evasion. Accumulating evidence suggests an important role for natural killer (NK) cells in this balance. NK cells can kill EBV-infected cells undergoing lytic replicationin vitro, and studies in both humans and mice with reconstituted human immune systems have shown that NK cells can limit EBV replication and prevent infectious mononucleosis. We now show that NK cells, via NKG2D and DNAM-1 interactions, recognize and kill EBV-infected cells undergoing lytic replication and that expression of a single EBV lytic gene, BZLF1, is sufficient to trigger sensitization to NK cell killing. We also present evidence suggesting the possibility of the existence of an as-yet-unidentified DNAM-1 ligand which may be particularly important for killing lytically infected normal B cells. Furthermore, while cells entering the lytic cycle become sensitized to NK cell killing, we observed that cells in the late lytic cycle are highly resistant. We identified expression of the vBcl-2 protein, BHRF1, as one effective mechanism by which EBV mediates this protection. Thus, contrary to the view expressed in some reports, EBV has evolved the ability to evade NK cell responses.IMPORTANCEThis report extends our understanding of the interaction between EBV and host innate responses. It provides the first evidence that the susceptibility to NK cell lysis of EBV-infected B cells undergoing lytic replication is dependent upon the phase of the lytic cycle. Induction of the lytic cycle is associated with acquired sensitization to NK cell killing, while progress through the late lytic cycle is associated with acquired resistance to killing. We provide mechanistic explanations for this novel observation, indicating important roles for the BZLF1 immediate early transactivator, the BHRF1 vBcl-2 homologue, and a novel ligand for the DNAM-1 NK cell receptor.

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