Colocalization of Interferon Regulatory Factor 7 (IRF7) with Latent Membrane Protein 1 (LMP1) of Epstein-Barr Virus

ABSTRACT We have shown previously that interferon regulatory factor 7 (IRF7), a multifunctional protein intimately involved in latent Epstein-Barr virus (EBV) infection, is induced as well as activated by EBV latent membrane protein 1 (LMP1), the principal EBV oncoprotein. Since the LMP1 promoter (LMP1p) contains an interferon-stimulated response element (ISRE), we hypothesized that IRF7 might be able to regulate LMP1 expression and thus participate in a regulatory circuit between these two genes. In this study, IRF7 was shown first to activate LMP1p in transient transfection assays. Compared with EBV nuclear antigen 2 (EBNA2), the most potent viral transactivator of LMP1p, IRF7 has a lesser effect (approximately 10% that of EBNA2) on induction of LMP1p. Study with IRF7 deletion mutants showed that IRF7 functional domains have similar effects on both the beta interferon (IFN-β) and LMP1 promoters in BJAB and 293 cells, and study with IRF7 phosphomimetic mutants showed that IRF7 phosphorylation may be involved in the activation of these two promoters. Further, the ISRE in LMP1p responds to IRF7 induction and IRF7 binds to this element. In the EBV-positive cell line P3HR1, which lacks the complete EBNA2 and EBV-encoded leader protein genes and hence expresses low-level LMP1, IRF7 alone can notably increase the endogenous LMP1 mRNA and protein levels. These results indicate that LMP1 is regulated by this host cell gene in addition to the viral factor, EBNA2, and may help to explain how LMP1 is expressed in type II latency in the absence of EBNA2. Moreover, IRF7 can regulate a viral gene in addition to a host cellular gene such as the IFN-β gene. Together with the previous data that LMP1 can induce IRF7 expression and facilitate IRF7 phosphorylation and nuclear translocation, these results suggest a positive regulatory circuit between IRF7 and LMP1.

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Epstein-Barr Virus Latent Membrane Protein 1 Regulates the Function of Interferon Regulatory Factor 7 by Inducing Its Sumoylation

Journal of Virology ◽

10.1128/jvi.01407-12 ◽

2012 ◽

Vol 86 (22) ◽

pp. 12251-12261 ◽

Cited By ~ 37

Author(s):

G. L. Bentz ◽

J. Shackelford ◽

J. S. Pagano

Keyword(s):

Membrane Protein ◽

Epstein Barr Virus ◽

Interferon Regulatory Factor ◽

Latent Membrane Protein ◽

Latent Membrane Protein 1 ◽

Regulatory Factor ◽

Barr Virus ◽

Interferon Regulatory Factor 7 ◽

Epstein Barr ◽

Virus Latent Membrane Protein

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Interferon Regulatory Factor 7 Mediates Activation of Tap-2 by Epstein-Barr Virus Latent Membrane Protein 1

Journal of Virology ◽

10.1128/jvi.75.1.341-350.2001 ◽

2001 ◽

Vol 75 (1) ◽

pp. 341-350 ◽

Cited By ~ 46

Author(s):

Luwen Zhang ◽

Joseph S. Pagano

Keyword(s):

Epstein Barr Virus ◽

Nuclear Translocation ◽

Interferon Regulatory Factor ◽

Latent Membrane Protein ◽

Latent Membrane Protein 1 ◽

Regulatory Factor ◽

Barr Virus ◽

Interferon Regulatory Factor 7 ◽

Epstein Barr

ABSTRACT Transporter associated with antigen processing 2 (Tap-2) is responsible for ATP-dependent transport of peptides from the cytosol to the endoplasmic reticulum, where peptides bind to newly synthesized human leukocyte antigen (HLA) class I molecules, which are essential for cellular immune responses. Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) has been shown to induce the expression of Tap-2. In this study, the induction of endogenous Tap-2 by LMP-1 is shown to be associated with and requires the expression of interferon regulatory factor 7 (IRF-7). In DG75 Burkitt's lymphoma (BL) cells, in which LMP-1 induces the expression of IRF-7, LMP-1 induced endogenous Tap-2, and ectopic expression of IRF-7 could enhance the induction. In Akata BL cells, in which LMP-1 could not induce IRF-7, LMP-1 could not induce Tap-2. Addition of IRF-7, which complements the defect in Akata cells, could stimulate the expression of Tap-2. Furthermore, LMP-1 and IRF-7A but not other IRF-7 splicing variants could activate endogenous Tap-2. A Tap-2 promoter reporter construct could be activated by the overexpression of IRF-7A. The activation could be specifically enhanced by LMP-1 and was dependent on an intact interferon-stimulated response element (ISRE) present in the Tap-2 promoter. Also, IRF-7 can bind to the Tap-2 promoter under physiological conditions in vivo, as shown by formaldehyde cross-linking, as well as to the Tap-2 ISRE in vitro, as shown by gel mobility shift assays. Furthermore, LMP-1 facilitates the phosphorylation and nuclear translocation of IRF-7. These data point to the role of IRF-7 as a secondary mediator of LMP-1-activated signal transduction for Tap-2 as follows: LMP-1 stimulates the expression of IRF-7 and facilitates its phosphorylation and nuclear translocation, and then the activated IRF-7 mediates the activation of the cellular Tap-2 gene. The induction of Tap-2 by IRF-7 and LMP-1 may have an important implication for the immune response to EBV and its persistence in vivo.

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Interferon Regulatory Factor 7 Is Induced by Epstein-Barr Virus Latent Membrane Protein 1

Journal of Virology ◽

10.1128/jvi.74.3.1061-1068.2000 ◽

2000 ◽

Vol 74 (3) ◽

pp. 1061-1068 ◽

Cited By ~ 71

Author(s):

Luwen Zhang ◽

Joseph S. Pagano

Keyword(s):

Membrane Protein ◽

Epstein Barr Virus ◽

Latent Membrane Protein ◽

Negative Regulator ◽

Latent Membrane Protein 1 ◽

Type I ◽

Regulatory Factor ◽

Type Iii ◽

Barr Virus ◽

Epstein Barr

ABSTRACT Infection by Epstein-Barr virus (EBV) generates several types of latency with different profiles of gene expression but with expression of Epstein-Barr nuclear antigen 1 (EBNA-1) in common. TheBamHI Q promoter (Qp) is used for the transcription of EBNA-1 mRNA in type I latency, which is an EBV infection state exemplified by Burkitt's lymphoma (BL). However, Qp is inactive in type III latency, and other promoters (C/Wp) are used for transcription of EBNA-1, which raises the question of how usage of these promoters is governed. Interferon (IFN) regulatory factor 7 (IRF-7) was identified first as a negative regulator of Qp. Expression of IRF-7 is associated with EBV type III latency, where Qp is inactive, but not with type I latency, raising the possibility that a viral gene product(s) expressed in type III latency might induce IRF-7 and repress Qp. Here, detailed analysis of the expression of IRF-7 revealed that it is associated with the expression of EBV latent membrane protein 1 (LMP-1) and that LMP-1 stimulates the expression of IRF-7 in type III latency in which Qp is inactive. In contrast, LMP-1 is not expressed in type I latency cells in which Qp is active. LMP-1 represses the constitutive activity of Qp reporter constructs. Mutational analysis of Qp reporter constructs revealed that the Qp IFN-stimulated response element (ISRE) is essential for the repression by LMP-1. Furthermore, LMP-1 reduced EBNA-1 mRNA derived from Qp only in type I cells in which IRF-7 could be induced. Finally, IFN-α, but not IFN-γ, repressed endogenous Qp activity, which is consistent with the ability of IFN-α to induce IRF-7. Thus, IRF-7 may mediate repression of Qp by LMP-1. The induction of IRF-7 by LMP-1 may be relevant to the silencing of Qp in EBV type III latency.

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Intracellular Signaling Molecules Activated by Epstein-Barr Virus for Induction of Interferon Regulatory Factor 7

Journal of Virology ◽

10.1128/jvi.75.24.12393-12401.2001 ◽

2001 ◽

Vol 75 (24) ◽

pp. 12393-12401 ◽

Cited By ~ 55

Author(s):

Luwen Zhang ◽

Lihong Wu ◽

Ke Hong ◽

Joseph S. Pagano

Keyword(s):

Membrane Protein ◽

Intracellular Signaling ◽

Epstein Barr Virus ◽

Nuclear Translocation ◽

Interferon Regulatory Factor ◽

Dominant Negative ◽

Regulatory Factor ◽

Barr Virus ◽

Interferon Regulatory Factor 7 ◽

Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) is the principal oncogenic protein in the EBV transformation process. LMP-1 induces the expression of interferon regulatory factor 7 (IRF-7) and activates IRF-7 protein by phosphorylation and nuclear translocation. LMP-1 is an integral membrane protein with two regions in its C terminus that initiate signaling processes, the C-terminal activator regions 1 (CTAR-1) and CTAR-2. Here, genetic analysis of LMP-1 has determined that the PXQXT motif that governs the interaction between LMP-1 CTAR-1 and tumor necrosis factor receptor-associated factors (TRAFs) is needed to induce the expression of IRF-7. Mutations in the PXQXT motif in CTAR-1 that disrupt the interaction between LMP-1 and TRAFs abolished the induction of IRF-7. Also, dominant-negative mutants of TRAFs inhibited the induction of IRF-7 by CTAR-1. The last three amino acids (YYD) of CTAR-2 are also important for the induction of IRF-7. When both PXQXT and YYD were mutated (LMP-DM), the LMP-1 mutant failed to induce IRF-7. Also, LMP-DM blocked the induction of IRF-7 by wild-type LMP-1. These data strongly suggest that both CTAR-1 and CTAR-2 of LMP-1 independently induce the expression of IRF-7. In addition, NF-κB is involved in the induction of IRF-7. A superrepressor of IκB (sr-IκB) could block the induction of IRF-7 by LMP-1, and overexpression of NF-κB (p65 plus p50) could induce the expression of IRF-7. In addition, we have found that human IRF-7 is a stable protein, and sodium butyrate, a modifier of chromatin structure, induces IRF-7.

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Sequence Variations of Epstein-Barr Virus-Encoded Small Noncoding RNA and Latent Membrane Protein 1 in Hematologic Tumors in Northern China

Intervirology ◽

10.1159/000510398 ◽

2021 ◽

Vol 64 (2) ◽

pp. 69-80

Author(s):

Hai-Yu Wang ◽

Lingling Sun ◽

Ping Li ◽

Wen Liu ◽

Zhong-Guang Zhang ◽

...

Keyword(s):

Membrane Protein ◽

Nested Pcr ◽

Noncoding Rna ◽

Epstein Barr Virus ◽

Northern China ◽

Latent Membrane Protein ◽

Latent Membrane Protein 1 ◽

Small Noncoding Rna ◽

Barr Virus ◽

Epstein Barr

Objective: To investigate the relationship between hematologic tumors and Epstein-Barr virus (EBV)-encoded small noncoding RNA (EBER) variations as well as latent membrane protein 1 (LMP1) variations. Methods: Patients with leukemia and myelodysplastic syndrome (MDS) were selected as subjects. Genotypes 1/2 and genotypes F/f were analyzed using the nested PCR technology, while EBER and LMP1 subtypes were analyzed by the nested PCR and DNA sequencing. Results: Type 1 was more dominant than type 2, found in 59 out of 82 (72%) leukemia and in 31 out of 35 (88.6%) MDS, while type F was more prevalent than type f in leukemia (83/85, 97.6%) and MDS (29/31, 93.5%) samples. The distribution of EBV genotypes 1/2 was not significantly different among leukemia, MDS, and healthy donor groups, neither was that of EBV genotypes F/f. EB-6m prototype was the dominant subtype of EBER in leukemia and MDS (73.2% [30/41] and 83.3% [10/12], respectively). The frequency of EB-6m was lower than that of healthy people (96.7%, 89/92), and the difference was significant (p < 0.05). China 1 subtype was the dominant subtype of LMP1 in leukemia and MDS (70% [28/40] and 90% [9/10], respectively), and there was no significant difference in the distribution of LMP1 subtypes among the 3 groups (p > 0.05). Conclusion: The distribution of EBV 1/2, F/f, EBER, and LMP1 subtypes in leukemia and MDS was similar to that in the background population in Northern China, which means that these subtypes may be rather region-restricted but not associated with leukemia and MDS pathogenesis.

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