Mutations in the Epstein-Barr virus latent membrane protein-1 (BNLF-1) gene in spontaneous lymphoblastoid cell lines: effect on in vitro transformation associated parameters and tumorigenicity in SCID and nude mice (original) (raw)
Journal of Virology, 1989
A previously unrecognized activity has been associated with the product of the BNLF-1 gene of Epstein-Barr virus. This gene encodes the latent membrane protein of Epstein-Barr virus. When the gene was expressed at high levels, it was toxic to all cell lines tested, which included six human B-lymphoid lines as well as BALB/3T3, 143/EBNA-1, and HEp-2 cells. The BNLF-1 gene was previously shown to induce anchorage-independent and tumorigenic growth in Rat-1 and BALB/3T3 cells. We demonstrate here that only those mutations in the BNLF-1 gene that score positively in the anchorage-independent growth assay were cytotoxic when expressed at high levels. It is therefore possible that the same activities of the latent membrane protein that are necessary to induce anchorage-independent growth of some rodent cell lines also confer toxicity to many cell lines when expressed at high levels.
Cellular expression profiles of Epstein-Barr virus-transformed B-lymphoblastoid cell lines
Biomedical Reports, 2020
Epstein-Barr virus (EBV) can infect human B cells and is associated with various types of B cell lymphomas. Studies on the global alterations of the cellular pathways mediated by EBV-induced B cell transformation are limited. In the present study, microarray analysis was performed following generation of two EBV-infected B-lymphoblastoid cell lines (BLCL), in which normal B cells obtained from two healthy Thai individuals and transcriptomic profiles were compared with their respective normal B cells. The two EBV-transformed BLCL datasets exhibited a high degree of similarity between their RNA expression profiles, whereas the two normal B-cell datasets did not exhibit the same degree of similarity in their RNA expression profiles. Differential gene expression analysis was performed, and the results showed that EBV infection was able to dysregulate several cellular pathways in the human B-cell genes involved in cancer and cell activation, such as the MAPK, WNT and PI3K-Akt signaling pathways, which were upregulated in the BLCL and were associated with increased cellular proliferation and immortalization of EBV-infected B cells. Expression of proteins located in the plasma membrane, which initiate a biological response to ligand binding, were also notably upregulated. Expression of genes involved in cell cycle control, the p53 signaling pathway and cellular senescence were downregulated. In conclusion, genes that were markedly upregulated by EBV included those involved in the acquisition of a tumorigenic phenotype of BLCL, which was positively correlated with several hallmarks of cancer.
Oncogene, 1997
Latent membrane protein (LMP) is a latent Epstein-Barr virus (EBV) protein expressed in the EBV associated malignancy, nasopharyngeal carcinoma (NPC). Properties ascribed to this protein include inhibition of epithelial cell dierentiation and deregulation of epithelial cellular gene expression, and are believed to contribute to the development of NPC. Studies to evaluate the oncogenic potential of LMP in epithelial cells have not been conclusive. We carried out studies to determine the tumorigenic activity of LMP in two human epithelial cell lines, SCC12F and HaCaT; while SCC12F LMP transfectants were non-tumorigenic in severe combined immunode®cient mice, HaCaT LMP transfectants were strongly oncogenic. The tumours produced were well dierentiated, keratinising squamous cell carcinomas suggesting that LMP does not inhibit epithelial cell dierentiation which con¯icts with a previous report by Dawson et al. (1990). To resolve this discrepancy we examined the ability of HaCaT and SCC12F LMP transfectants to dierentiate in a suspension culture assay. Both lines were able to dierentiate to a similar extent as parental lines and control transfectants. Our results indicate that LMP is strongly oncogenic in human epithelial cells but that inhibition of dierentiation is not necessarily a mechanism by which LMP contributes to the pathogenesis of NPC.
Epstein-Barr virus – molecular basis for malignant transformation
Scripta Scientifica Medica, 2016
Epstein-Barr (EBV) is a widespread virus which can be detected in more than 90% of world population. Primary EBV infection during adolescence and adulthood results in infectious mononucleosis, while in children it is usually asymptomatic. EBV is responsible for different malignant forms of B-cell or epithelial cancers, such as Hodgkin's and non-Hodgkin's lymphoma, Burkitt's lymphoma, post-transplant lymphoproliferative disorders, nasopharyngeal carcinoma, hairy leukoplakia and HIV-associated lymphomas. Evidence exists that an infection with EBV is also linked with a higher risk of hepatocellular and gastric cancers, as well as autoimmune diseases. EВV shows two alternative life cycles-latent and lytic. After the primary infection, the virus remains in the B lymphocytes in latency, while the lytic infection takes place predominantly in the epithelial cells and can last for months with constant virus release in saliva and nasopharyngeal secretion. Unlike other herpes viruses, the development of oncological diseases is linked with the latent cycle, as a result of the immune response failure to control latently infected cells. With the present work we try to concisely review the current knowledge about mechanisms of EBV pathogenesis in humans and to summarize recent findings in the field.
Epstein–Barr Virus-Associated Malignancies: Roles of Viral Oncoproteins in Carcinogenesis
Frontiers in Oncology, 2018
The Epstein-Barr virus (EBV) is the first herpesvirus identified to be associated with human cancers known to infect the majority of the world population. EBV-associated malignancies are associated with a latent form of infection, and several of the EBVencoded latent proteins are known to mediate cellular transformation. These include six nuclear antigens and three latent membrane proteins (LMPs). In lymphoid and epithelial tumors, viral latent gene expressions have distinct pattern. In both primary and metastatic tumors, the constant expression of latent membrane protein 2A (LMP2A) at the RNA level suggests that this protein is the key player in the EBV-associated tumorigenesis. While LMP2A contributing to the malignant transformation possibly by cooperating with the aberrant host genome. This can be done in part by dysregulating signaling pathways at multiple points, notably in the cell cycle and apoptotic pathways. Recent studies also have confirmed that LMP1 and LMP2 contribute to carcinoma progression and that this may reflect the combined effects of these proteins on activation of multiple signaling pathways. This review article aims to investigate the aforementioned EBV-encoded proteins that reveal established roles in tumor formation, with a greater emphasis on the oncogenic LMPs (LMP1 and LMP2A) and their roles in dysregulating signaling pathways. It also aims to provide a quick look on the six members of the EBV nuclear antigens and their roles in dysregulating apoptosis.
Journal of Virology, 1993
The stable expression of the Epstein-Barr virus (EBV) latent membrane protein (LMP) in certain EBV-negative Burkitt's lymphoma cell lines correlates with an increased expression of the oncogene Bcl-2 (S. Henderson, M. Rowe, C. Gregory, D. Croom-Carter, F. Wang, R. Longnecker, E. Kieff, and A. Rickinson, Cell 65:1107-1115, 1991). This finding is consistent with a model in which Bcl-2 contributes to the immortalization of B cells mediated by EBV. We therefore asked whether the expression of Bcl-2 protein correlates with the induction of three cellular phenotypes induced by or associated with LMP. The expression of Bcl-2 in primary B cells infected with the B95-8 strain of EBV varied between 1 and 1.8 times that in uninfected cells when 50% of the cells were infected, expressed LMP, and incorporated 20-fold more [3H]thymidine than did uninfected cells. This finding indicates that induced proliferation of these primary cells is not sufficient to induce Bcl-2. We found that BALB/c 3T...
Oncotarget, 2015
A tumor model that Epstein-Barr virus (EBV) latent infection facilitated the tumorigenicity was previously established using the Maxi-EBV system. In the present approach, EBV-lost cell clones demonstrated significantly decreased tumorigenesis. On the other hand, the LMP1 gene in Maxi-EBV genome was replaced by that of nasopharyngeal carcinoma origin. The resultant cell line, 293-1/NL showed much lower malignancy than the original 293-EBV. The result was opposite to our expectation. The change of 293 sublineage cells for EBV harboring also got similar result. To seek the underlying reason, the copy number of EBV genome in all the cell lines was detected. The result indicated that 293-EBV contained about 4.5-fold higher EBV copies than 293-1/NL did. Parallel EBV genomes led to relatively stable copies in different 293 sublineages, suggesting the viral genome structure is a factor for the sustainability of EBV's copy number. Moreover, the LMP1 transcription in high copy-containing ...
Blood, 1997
Sequence variations in the Epstein-Barr virus (EBV) encoded latent membrane protein-1 (LMP-1) gene have been described in a Chinese nasopharyngeal carcinoma-derived isolate (CAO), and in viral isolates from various EBV-associated tumors. It has been suggested that these genetic changes, which include loss of a Xho I restriction site (position 169425) and a C-terminal 30-base pair (bp) deletion (position 168287-168256), define EBV genotypes associated with increased tumorigenicity or with disease among particular geographic populations. To determine the frequency of LMP-1 variations in European wild-type virus isolates, we sequenced the LMP1 promoter and gene in EBV from lymphoblastoid cell lines from healthy carriers and patients without EBV-associated disease. Sequence changes were often present, and defined at least four main groups of viral isolates, which we designate Groups A through D. The widespread prevalence of LMP-1 sequence variations, particularly the Xho I polymorphism ...
Oncogene, 1999
Epstein-Barr virus (EBV) transforms resting primary human B lymphocytes into inde®nitely proliferating lymphoblastoid cell lines in vitro and is associated with several human malignancies in vivo. Recombinant EBV genetic analyses combined with in vitro B lymphocyte transformation assays demonstrate that latent infection membrane protein 1 (LMP1) is essential for EBVmediated lymphocyte transformation. LMP1 has no intrinsic enzymatic activity but instead aggregates cellular proteins of the tumor necrosis factor receptor signaling pathway to activate transcription factor NF-kB. Mutants rendering LMP1 defective in these protein interactions are impaired in their abilities to activate NF-kB in reporter gene assays. Concordantly, EBV recombinants with LMP1 mutations that are compromised for NF-kB activation are impaired for growth transformation. Thus, EBV-mediated growth transformation is genetically and biochemically linked to LMP1mediated activation of NF-kB.
Epstein–Barr virus and oncogenesis: from latent genes to tumours
Oncogene, 2003
Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumours. As a common virus infection, EBV appears to have evolved to exploit the process of B cell development to persist as a lifelong asymptomatic infection. However, the virus can contribute to oncogenesis as evidenced by its frequent detection in certain tumours, namely Burkitt's lymphoma (BL), post-transplant B cell lymphomas, Hodgkin's disease (HD) and nasopharyngeal carcinoma (NPC), and by its unique ability to efficiently transform resting B cells in vitro into permanently growing lymphoblastoid cell lines (LCLs). These transforming effects are associated with the restricted expression of EBV genes such that only a subset of so-called latent virus proteins are expressed in virus infected tumours and in LCLs. Distinct forms of EBV latency are manifest in the different tumours and these appear to be a vestige of the pattern of latent gene expression used by the virus during the establishment of persistent infection within the B cell pool. This review summarises our current knowledge of EBV latent gene function and how this relates to the role of the virus in the aetiology of different tumours.
Journal of virology, 1995
Recombinant Epstein-Barr viruses (EBVs) were made with mutated latent membrane protein 1 (LMP1) genes that express only the LMP1 amino-terminal cytoplasmic and six transmembrane domains (MS187) or these domains and the first 44 amino acids of the 200-residue LMP1 carboxy-terminal domain (MS231). After infection of primary B lymphocytes with virus stocks having small numbers of recombinant virus and large numbers of P3HR-1 EBV which is transformation defective but wild type (WT) for LMP1, all lymphoblastoid cell lines (LCLs) that had MS187 or MS231 LMP1 also had WT LMP1 provided by the coinfecting P3HR-1 EBV. Lytic virus infection was induced in these coinfected LCLs, and primary B lymphocytes were infected. In over 200 second-generation LCLs, MS187 LMP1 was never present without WT LMP1. Screening of over 600 LCLs infected with virus from MS231 recombinant virus-infected LCLs identified two LCLs which were infected with an MS231 recombinant without WT LMP1. The MS231 recombinant vir...
The Epstein-Barr Virus Regulome in Lymphoblastoid Cells
Cell host & microbe, 2017
Epstein-Barr virus (EBV) transforms B cells to continuously proliferating lymphoblastoid cell lines (LCLs), which represent an experimental model for EBV-associated cancers. EBV nuclear antigens (EBNAs) and LMP1 are EBV transcriptional regulators that are essential for LCL establishment, proliferation, and survival. Starting with the 3D genome organization map of LCL, we constructed a comprehensive EBV regulome encompassing 1,992 viral/cellular genes and enhancers. Approximately 30% of genes essential for LCL growth were linked to EBV enhancers. Deleting EBNA2 sites significantly reduced their target gene expression. Additional EBV super-enhancer (ESE) targets included MCL1, IRF4, and EBF. MYC ESE looping to the transcriptional stat site of MYC was dependent on EBNAs. Deleting MYC ESEs greatly reduced MYC expression and LCL growth. EBNA3A/3C altered CDKN2A/B spatial organization to suppress senescence. EZH2 inhibition decreased the looping at the CDKN2A/B loci and reduced LCL growth...
Epstein–Barr virus latent genes
Latent Epstein-Barr virus (EBV) infection has a substantial role in causing many human disorders. The persistence of these viral genomes in all malignant cells, yet with the expression of limited latent genes, is consistent with the notion that EBV latent genes are important for malignant cell growth. While the EBV-encoded nuclear antigen-1 (EBNA-1) and latent membrane protein-2A (LMP-2A) are critical, the EBNA-leader proteins, EBNA-2, EBNA-3A, EBNA-3C and LMP-1, are individually essential for in vitro transformation of primary B cells to lymphoblastoid cell lines. EBV-encoded RNAs and EBNA-3Bs are dispensable. In this review, the roles of EBV latent genes are summarized.
Signature Amino Acid Changes in Latent Membrane Protein 1 Distinguish Epstein–Barr Virus Strains
Virology, 1999
Sequence variations in the Epstein-Barr virus (EBV) latent membrane protein 1 gene have been described in numerous EBV-associated tumors with some of these variations, most notably a 30-base pair deletion in the cytoplasmic carboxylterminal domain, suggested as associated with an increase in tumorigenicity. In this study, EBV DNA sequence was determined from 92 tissue specimens or cell lines, including nasopharyngeal carcinoma, oral hairy leukoplakia, posttransplant lymphoma, post-transplant without pathology, mononucleosis, Burkitt's lymphoma, parotid tumor, and normal from distinct geographical regions. The amino-and carboxyl-terminal sequences and, in some cases, the full-length sequences of latent membrane protein 1 were determined. Characteristic sequence patterns distinguished strains, with the carboxylterminal sequence being the most informative in distinguishing among the strains. Phylogenetic relationships between strains were determined, as were signature amino acid changes that discriminate between them. A correlation between strain and disease or strain and geographic location was not detected. The sequence variation and signature sequences identified at least seven distinct strains, as well as hybrid strains that apparently result from recombination.
International Journal of Cancer, 1994
This study examined the effect of naturally occurring Epstein-Barr virus (EBV) latent membrane protein 1 (LMP-1) gene sequence variation on the LMP-1 half-life in epithelial cells. The LMP-1 half-life was not influenced by sequence variation in amino acids 250 to 307 or amino acids 343 to 352. The LMP-1 half-life was short when the amino acid encoded at position 129 was methionine, the initiation codon product of lytic LMP-1 (lyLMP-1). The mutation of amino acid 129 to isoleucine greatly increased the LMP-1 half-life. Expression of lyLMP-1 in trans down-regulated the LMP-1 half-life in a dose-dependent manner and restored a short-half-life phenotype to the mutated LMP-1 construct lacking the cis ability to express lyLMP-1. This observed dominant negative effect of lyLMP-1 expression on the LMP-1 half-life in epithelial cells in vitro may have implications for EBV epithelial oncogenesis in vivo.
Journal of Virology, 1994
Previous recombinant Epstein-Barr virus molecular genetic experiments with specifically mutated LMP1 genes indicate that LMP1 is essential for primary B-lymphocyte growth transformation and that the amino-terminal cytoplasmic and first transmembrane domains are together an important mediator of transformation. EBV recombinants with specific deletions in the amino-terminal cytoplasmic domain have now been constructed and tested for the ability to growth transform primary B lymphocytes into lymphoblastoid cell lines. Surprisingly, deletion of DNA encoding EHDLER or GPPLSSS from the full LMP1 amino-terminal cytoplasmic domain (MEHDLERGPPGPRRPPRGPPLSSS) had no discernible effect on primary B-lymphocyte transformation. These two motifs distinguish the LMP1 amino-terminal cytoplasmic domain from other arginine-rich membrane proximal sequences that anchor hydrophobic transmembrane domains. Two deletions which included the ERGPPGPRRPPR motif adversely affected but did not prevent transforma...
Archives of Virology, 2004
Epstein Barr virus widely infects human populations and remains mostly asymptomatic; however, it has been associated with several malignancies. The EBV-encoded latent membrane protein-1 has been involved in neoplasic transformation; a 30-bp deletion and several mutations in the COOH-terminal domain have been associated with histopathological and clinical disease features. Objective: To analyze and correlate the presence of mutations and a 30-bp deletion with the influence of LMP-1 on tumorigenicity in a population of EBV+ pediatric malignancies. Methods: We studied EBV presence by LMP-1 immunohistochemistry, EBERs in situ hybridization and PCR in fresh and formalin-fixed paraffinembedded tissue samples from 10 Hodgkin's lymphomas, 6 non-Hodgkin's lymphomas, 4 undifferentiated nasopharyngeal carcinomas. Eighteen out of 20 samples were sequenced. Eight fresh normal lymphoid tissue samples and 3 peripheral blood samples were analyzed. Results: All cases were EBV positive. EBV typing rendered 12 EBV-1 and 8 EBV-2. Del-LMP-1 was detected in 15/20 EBV related malignancies, as well as in 4/11 control tissues. A high percentage of patients showed point mutations previously described. The presence of del-LMP-1 and point mutations failed to correlate with clinical course. Conclusions: We found a marked incidence of del-LMP-1 (75%) in our series. However, we failed to find any correlation between histological aggressiveness of malignancies and the presence of del-LMP-1 and point mutations.
Functional interplay of Epstein-Barr virus oncoproteins in a mouse model of B cell lymphomagenesis
Proceedings of the National Academy of Sciences, 2020
Epstein-Barr virus (EBV) is a B cell transforming virus that causes B cell malignancies under conditions of immune suppression. EBV orchestrates B cell transformation through its latent membrane proteins (LMPs) and Epstein-Barr nuclear antigens (EBNAs). We here identify secondary mutations in mouse B cell lymphomas induced by LMP1, to predict and identify key functions of other EBV genes during transformation. We find aberrant activation of early B cell factor 1 (EBF1) to promote transformation of LMP1-expressing B cells by inhibiting their differentiation to plasma cells. EBV EBNA3A phenocopies EBF1 activities in LMP1-expressing B cells, promoting transformation while inhibiting differentiation. In cells expressing LMP1 together with LMP2A, EBNA3A only promotes lymphomagenesis when the EBNA2 target Myc is also overexpressed. Collectively, our data support a model where proproliferative activities of LMP1, LMP2A, and EBNA2 in combination with EBNA3A-mediated inhibition of terminal p...