Epstein-Barr Virus-Induced Changes in B-Lymphocyte Gene Expression

Abstract

In primary Epstein-Barr virus (EBV) infection, a substantial fraction of peripheral blood B lymphocytes are latently infected and express virus-encoded proteins that are capable of causing continuous B-cell proliferation. The EBV-encoded proteins engender an unusually vigorous and large T-cell immune response which eliminates most of the virus-infected cells. In severely T-cell immune-compromised or otherwise susceptible people, the EBV-infected B lymphocytes can malignantly proliferate (reviewed in reference 90).The EBV gene products that are expressed in primary lymphocyte infection and that stimulate cell proliferation include six nuclear antigen proteins (EBNAs), two latent infection integral membrane proteins (LMPs), two small RNAs (EBERs), and BamA rightward transcripts (BARTs) of uncertain function (reviewed in reference 59). This complex infection, termed latency III, is characteristic of EBV gene expression in EBV-transformed lymphoblastoid cell lines (LCLs) and many lymphoproliferations that occur in immune-deficient humans (23, 95).Many of the EBV effects on cell growth and survival are likely to be mediated by EBV-induced changes in cell gene transcription. Five of the EBNAs can alter cell gene transcription through their direct or indirect interaction with the cellular DNA sequence-specific transcription factors RBP-j/CBF1, PU.1, and AUF1 (35,42,52,53,65,72,91,113,119,123). Furthermore, EBV LMP1 is similar to a constitutively activated CD40 receptor and activates NF-B, Jun/Fos, and AP1 cellular transcription factors (27,28,30,33,36,40,45,50,60,66,81,83). Moreover, EBV LMP2 is similar to a constitutively activated B-cell antigen receptor (BCR) in causing a stable small increase in BCR tyrosine kinase signaling and in desensitizing the cell to BCR-type signal transduction (12, 80). Four of the EBNAs that interact with cellular transcription factors and LMP1 are critical for EBV effects on cell growth and survival, while EBNA3B, LMP2, EBERs, and BARTs are not (19,37,49,56,68,73,76,92,102,108,109).In the experiments reported here, cDNA arrays were used to investigate the effects of EBV latency III infection on cell gene transcription. cDNA arrays are particularly useful in characterizing changes in expression of large numbers of cellular genes (3,4,48,51,57,74,97,100). We compared gene expression in BL41, an EBV-negative Burkitt's lymphoma (BL) cell line, with gene expression in two latency III-expressing cell lines-BL41 infected in vitro with EBV (BL41EBV) and an LCL (IB4) (18,62). In contrast to a comparison of LCLs with resting B lymphocytes, which would identify a large number of cell genes whose expression is up-regulated at various points in the cell cycle, comparison with a non-EBV-infected BL cell line will identify genes that are specifically up-regulated by EBV latency III proteins. However, EBV-regulated genes whose transcription is inherent to the BL phenotype, such as c-myc, may escape detection. MATERIALS AND METHODS Cell

AIDS and associated malignancies

“…This form of latency is termed Latency III. This form of latency is common in immunoblastic lymphomas [17]. A Type II form of latency where EBNA 1, LMP-1 and LMP-2a are expressed has been identified in some EBV associated lymphomas.…”

“…The most commonly identified virus associated with AIDS related lymphomas is EBV and there is a large body of published work on the oncogenic mechanisms of this agent [17,18]. B-lymphocytes transformed by EBV (lymphoblastoid cell lines) in vitro express an array of virus-encoded proteins including six EBV nuclear antigens (EBNAs) and three LMPs.…”

“…A Type II form of latency where EBNA 1, LMP-1 and LMP-2a are expressed has been identified in some EBV associated lymphomas. In Latency I (typical of Burkitt lymphomas) only EBNA-1 (generated from the Qp promoter) and EBERs are expressed [17,18]. Recent studies have indicated that some heterogeneity in EBV gene expression and EBNA promoter usage exists among endemic BL [19].…”

NF-κB Down-regulates Expression of the B-lymphoma Marker CD10 through a miR-155/PU.1 Pathway

“…The six human B-lymphoma cell lines used in this study are as follows: BJAB, EBV-negative, GCB-like DLBCL (20,21); SUDHL-4, a B-lymphoma that has been characterized as both a follicular lymophoma (22) and GCBlike DLBCL (23); BL-41, EBV-negative Burkitt lymphoma (14); Daudi, EBV-positive, LMP1-negative Burkitt lymphoma (24); IB4, EBV-transformed lymphoblastoid cell line (14); and RC-K8, ABC-like DLBCL (25). For treatment of cells with lipopolysaccharide (LPS) (Sigma), BJAB cells were first cultured in DMEM containing 5% FBS for 24 h and then treated with 5 g/ml of LPS for the indicated times.…”

“…We previously showed that overexpression of an activated mutant of the NF-B family transcription factor REL in the GCB-like B-lymphoma cell line BJAB leads to reduced expression of CD10 (13). Infection of cells with Epstein-Barr virus (EBV) or human cytomegalovirus, both inducers of NF-B, causes reduced expression of CD10 (14,15). Taken together, such results suggested to us that NF-B or a target of NF-B is involved in repressing CD10 gene/protein expression in certain B-cell lymphomas.…”