Biologic and antigenic characteristics of epstein‐barr virus‐related herpesviruses of chimpanzees and baboons

Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA-3C) is a large transcriptional regulator essential for EBV-mediated immortalization of B lymphocytes. We previously identified interactions between EBNA-3C and two cellular transcription factors, J and Spi proteins, through which EBNA-3C regulates transcription. To better understand the contribution of these interactions to EBNA-3C function and EBV latency, we examined whether they are conserved in the homologous proteins of nonhuman primate lymphocryptoviruses (LCVs), which bear a strong genetic and biological similarity to EBV. The homologue of EBNA-3C encoded by the LCV that infects baboons (BaLCV) was found to be only 35% identical in sequence to its EBV counterpart. Of particular significance, this homology localized predominantly to the N-terminal half of the molecule, which encompasses the domains in EBNA-3C that interact with J and Spi proteins. Like EBNA-3C, both BaLCV and rhesus macaque LCV (RhLCV) 3C proteins bound to J and repressed transcription mediated by EBNA-2 through its interaction with J. Both nonhuman primate 3C proteins were also able to activate transcription mediated by the Spi proteins in the presence of EBNA-2. Like EBNA-3C, a domain encompassing the putative basic leucine zipper motif of the BaLCV-3C protein directly interacted with both Spi-1 and Spi-B. Surprisingly, a recently identified motif in EBNA-3C that mediates repression was not identifiable in the BaLCV-3C protein.Finally, although the C terminus of BaLCV-3C bears minimal homology to EBNA-3C, it nonetheless contains a C-terminal domain rich in glutamine and proline that was able to function as a potent transcriptional activation domain, as does the C terminus of EBNA-3C. The conservation of these functional motifs despite poor overall homology among the LCV 3C proteins strongly suggests that the interactions of EBNA-3C with J and Spi do indeed play significant roles in the life cycle of EBV.Studies using recombinant Epstein-Barr virus (EBV) genomes have identified six latent infection proteins that are essential for EBV-mediated immortalization of B lymphocytes in vitro: EBV nuclear antigen 1 (EBNA-1), EBNA-2, EBNA-LP, EBNA-3A, EBNA-3C, and latent membrane protein (LMP) 1 (5,17,27,29,34,53). Two of these viral proteins, and perhaps the least well understood, are members of the EBNA-3 family of transcriptional regulators. Although the three EBNA-3 genes (3A, 3B, and 3C) share a similar gene structure and are likely to have evolved from a common ancestral gene, the encoded proteins are highly divergent in amino acid sequence. The EBNA-3 proteins are also likely to have diverged functionally, since EBNA-3A and EBNA-3C, but not EBNA-3B, are essential for EBV-mediated immortalization of B lymphocytes. Despite their differences, all EBNA-3 proteins function as transcriptional regulatory proteins whose transcriptional effects are mediated through interactions with cellular sequence-specific DNA-binding proteins, rather than by binding directly to DNA (26,45,50,57,58). In addition to...

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confidence: 99%

Transcriptional Regulatory Properties of Epstein-Barr Virus Nuclear Antigen 3C Are Conserved in Simian Lymphocryptoviruses

Dalbiès-Tran

Jiang

Ruf

et al. 2003

“…This so-called growth program of latency, or the latency III program, is also observed during the early phase of latent infection in vivo and in EBV-associated lymphoproliferative disorders which occur in immunocompromised patients. The ability to immortalize B lymphocytes in vitro and the association with lymphomas and lymphoproliferative disorders are shared by distantly related lymphocryptoviruses that infect Old World primates such as chimpanzees, baboons, or rhesus macaques (9,14). Infection of rhesus macaques with their respective virus mirrors EBV infection of humans, making them excellent animal models of EBV infection (39).…”

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confidence: 99%

Amino Acids of Epstein-Barr Virus Nuclear Antigen 3A Essential for Repression of Jκ-Mediated Transcription and Their Evolutionary Conservation

Dalbiès-Tran

Stigger-Rosser

Dotson

et al. 2001

Epstein-Barr virus (EBV) nuclear antigen 3A (EBNA-3A) is essential for virus-mediated immortalization of B lymphocytes in vitro and is believed to regulate transcription of cellular and/or viral genes. One known mechanism of regulation is through its interaction with the cellular transcription factor J. This interaction downregulates transcription mediated by EBNA-2 and J. To identify the amino acids that play a role in this interaction, we have generated mutant EBNA-3A proteins. A mutant EBNA-3A protein in which alanine residues were substituted for amino acids 199, 200, and 202 no longer downregulated transcription. Surprisingly, this mutant protein remained able to coimmunoprecipitate with J. Using a reporter gene assay based on the recruitment of J by various regions spanning EBNA-3A, we have shown that this mutation abolished binding of J to the N-proximal region (amino acids 125 to 222) and that no other region of EBNA-3A alone was sufficient to mediate an association with J. To determine the biological significance of the interaction of EBNA-3A with J, we have studied its conservation in the simian lymphocryptovirus herpesvirus papio (HVP) by cloning HVP-3A, the homolog of EBNA-3A encoded by this virus. This 903-amino-acid protein exhibited 37% identity with its EBV counterpart, mainly within the amino-terminal half. HVP-3A also interacted with J through a region located between amino acids 127 and 223 and also repressed transcription mediated through EBNA-2 and J. The evolutionary conservation of this function, in proteins that have otherwise significantly diverged, argues strongly for an important biological role in virus-mediated immortalization of B lymphocytes.The ubiquitous human gammaherpesvirus Epstein-Barr virus (EBV) infects epithelial cells in the oropharynx and then establishes a latent infection in B lymphocytes (for a review, see reference 28). These latently infected B cells are believed to constitute the reservoir of virus that sustains the host's lifelong infection. In vitro, EBV-mediated immortalization of B lymphocytes generates lymphoblastoid cell lines in which the full set of viral latent genes is expressed (for reviews, see references 28, 46, and 51). This so-called growth program of latency, or the latency III program, is also observed during the early phase of latent infection in vivo and in EBV-associated lymphoproliferative disorders which occur in immunocompromised patients. The ability to immortalize B lymphocytes in vitro and the association with lymphomas and lymphoproliferative disorders are shared by distantly related lymphocryptoviruses that infect Old World primates such as chimpanzees, baboons, or rhesus macaques (9, 14). Infection of rhesus macaques with their respective virus mirrors EBV infection of humans, making them excellent animal models of EBV infection (39).Only a very limited number of gene products encoded by EBV can be detected in EBV-immortalized B cells. Three of these are members of the EBV nuclear antigen 3 (EBNA-3) family, two of which, EBNA-3A and -3C...

“…While EBV has been reported to immortalize B cells from chimpanzees, it was reported to be unable to immortalize cells from baboons or macaques (5)(6)(7)(8). LCV from cynomolgus macaques (cyLCV) and rhesus macaques (rhLCV) could transform B cells from both macaque species but not human cells (8,9).…”

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confidence: 99%

“…These data suggest a model of a restricted host range in which LCV can immortalize B cells from their own and closely related primate species but not cells from more distant species. This model is challenged by reports that LCV from chimpanzees (chLCV) and baboons (baLCV) could immortalize B cells from humans, baboons, and different macaque species, suggesting no restriction of LCV host range among hominoids and Old World NHP (6,7). However, the cell line used as the source of chLCV in those studies was obtained not by spontaneous outgrowth from chimpanzee peripheral blood mononuclear cells (PBMC) but by infecting baboon PBMC with throat swab material from chimpanzees (5,6,10).…”

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confidence: 99%

“…Since we used a baLCV strain (S594; isolated from Papio hamadryas) different from that used for the published baEBNA2 sequence (BA65; isolated from Papio cynocephalus), we sequenced baEBNA2 of S594 and found only four nucleotide and two amino acid changes compared to BA65 baEBNA2 ( Fig. 2) (6,8,(11)(12)(13). The stronger EBNA2 similarity of chLCV with EBV and of cyLCV with rhLCV confirmed the hominoid and Old World NHP origins of m5305 chLCV and m4409 cyLCV, respectively.…”

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confidence: 99%

See 1 more Smart Citation

Host Range Restriction of Epstein-Barr Virus and Related Lymphocryptoviruses

Mühe

Wang

2015

Epstein-Barr-related herpesviruses, or lymphocryptoviruses (LCV), naturally infect humans and nonhuman primates (NHP), but their host range is not well characterized. Using LCV and B cells from multiple species of Hominidae and Cercopithecidae, we show that LCV can immortalize B cells from some nonnative species but that growth transformation is restricted to B cells from their own family of hominoids or Old World NHP, suggesting a high degree of LCV adaptation to their natural primate host. Herpesviruses in the lymphocryptovirus (LCV) genus are found naturally only in hominoids (human, great apes, and gibbons) and Old and New World nonhuman primates (NHP), suggesting that they evolved relatively recently. LCVs infecting hominoids and Old World NHP have well-conserved viral genomes and biological properties, including the ability to immortalize B cells from the natural host in vitro (1, 2). Epstein-Barr virus (EBV), i.e., human LCV, can also immortalize B cells derived from New World NHP, leading to the assumption that LCV might have the ability to immortalize B cells from other NHP species (3, 4). However, a clear model for the host range of LCV-induced B cell immortalization has not emerged from the literature.While EBV has been reported to immortalize B cells from chimpanzees, it was reported to be unable to immortalize cells from baboons or macaques (5-8). LCV from cynomolgus macaques (cyLCV) and rhesus macaques (rhLCV) could transform B cells from both macaque species but not human cells (8,9). These data suggest a model of a restricted host range in which LCV can immortalize B cells from their own and closely related primate species but not cells from more distant species. This model is challenged by reports that LCV from chimpanzees (chLCV) and baboons (baLCV) could immortalize B cells from humans, baboons, and different macaque species, suggesting no restriction of LCV host range among hominoids and Old World NHP (6, 7). However, the cell line used as the source of chLCV in those studies was obtained not by spontaneous outgrowth from chimpanzee peripheral blood mononuclear cells (PBMC) but by infecting baboon PBMC with throat swab material from chimpanzees (5, 6, 10). Virtually all domesticated Old World NHP raised in conventional groups are persistently infected with their natural LCV. Thus, the cell line derived from baboon PBMC could theoretically have been infected with either chLCV or endogenous baLCV, and techniques to distinguish the two were not available at the time at which those studies were performed. In our previous studies, we obtained immortalized human B cell lines after exposing human PBMC to baLCV, but in all cases the cell lines contained both baLCV and endogenous EBV; i.e., baLCV required EBV coinfection for human B cell immortalization (8). Those studies demonstrated the potential problem posed by persistent B cell infection with endogenous LCV and the importance of confirming the molecular signature, or identity, of the transforming virus in immortalized cells.Unfortunately, the cel...