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Latent Epstein-Barr virus (EBV) infection is associated with a variety of malignancies. Rapid in situ hybridization techniques have been described for various lytic viral infections because of limited gene expression. However, EBERS (Epstein Barr early RNAs) are expressed in abundance in tumour cells which are latently infected with EBV. We have targeted these transcripts in a rapid (3 h) in situ hybridization assay fo the detection of latent EBV in clinical specimens, including formalin-fixed paraffin-embedded material. EBER RNA was detected in control cell lines which have two copies of the EBV genome and in paraffin-embedded biopsy specimens from patients with nasopharyngeal carcinoma, EBV-associated Hodgkin's disease, Burkitt's lymphoma and post-transplant lymphoma. The technique did not detect EBER RNA in oral hairy leukoplakia, a pathologic process previously characterized as associated with lytic EBV infection. The sensitivity, specificity and rapidity of this technique make it ideal for the diagnostic detection of EBV in latently infected clinical specimens.
Mol Cell Probes 1993 Apr
PMID:Rapid in situ hybridization for the diagnosis of latent Epstein-Barr virus infection. 839 39

Most of the evidence that supports the hypothesis that the c-myc gene is abnormally regulated in Burkitt's lymphoma (BL) is indirect. The putative abnormal expression of c-myc is likely, at least in part, to be a consequence of the usurpation of its regulatory sequences by immunoglobulin enhancer elements, which are invariably juxtaposed to c-myc by the translocations associated with this tumor (C. M. Croce, J. Erikson, A. Ar-Rushdi, D. Aden, and K. Nishikura, Proc. Natl. Acad. Sci. USA, 81: 3170-3174, 1984). We have developed a differentiation induction model system to examine this issue more directly. In a variety of non-BL cell lines, differentiation induction results in the down-regulation of c-myc (G. P. Studzinski, A. K. Bhandal, and Z. S. Brelvi, Proc. Soc. Exp. Biol. Med., 179: 288-295, 1985; Y. Matsui, R. Takahasi, K. Minara, T. Nakagawa, T. Koizumi, Y. Nakao, T. Sugiyama, and T. Fugita, Cancer Res., 49: 1366-1371, 1985; T. Mitchell, E. Sariban, and D. Kufe, Mol. Pharmacol., 30: 398-402, 1986; Z. S. Brelvi, and G. P. Studzinski, J. Cell. Physiol., 128: 171-179, 1986). Since BL is of B-cell origin, differentiation is associated with persistent or increased expression of immunoglobulin genes. Therefore, if c-myc and c-mu are coregulated in BL via immunoglobulin enhancer sequences, persistent or increased expression of the c-myc gene, rather than down-regulation, should occur in differentiated BL cells. Differentiation was induced in four BL cell lines with theophylline (7 x 10(-3) M), and mRNA was examined by Northern blot analysis. In all four BL lines studied (JD38, AG876, KK124, and Daudi), there was persistent or increased expression of both c-mu and c-myc genes (detected with a third exon c-myc probe), in contrast to the decreased expression of the c-myc gene observed in the three Epstein-Barr virus transformed lines studied (A3317, TC84, and CB34). In the BL cell line, JD38, the c-myc gene is truncated (the second and third exons are translocated to chromosome 14 while the first exon remains on chromosome 8). In this line, we demonstrated that theophylline induced differentiation results in down-regulation of the first exon while the level of expression of the translocated second and third exons remains unchanged or increases.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Theophylline induced differentiation provides direct evidence for the deregulation of c-myc in Burkitt's lymphoma and suggests participation of immunoglobulin enhancer sequences. 841 37

Expression of beta interferon (IFN-beta) is transiently induced when Namalwa B cells (Burkitt lymphoma cell line) are infected by Sendai virus. In this study, we found that an elongation of the IFN-beta mRNA could be detected in virus-infected cells and that such a modification was not observed when the IFN-beta transcript was induced by a nonviral agent, poly(I-C). Treatment of the cells with a transcriptional inhibitor (actinomycin D or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole) resulted in further elongation of the transcript. Characterization of the elongated IFN-beta transcript by primer extension and RNase H treatment showed that the modification was a result of an elongated poly(A) tail of up to 400 nucleotides. We conclude that the poly(A) tail elongation of the IFN-beta transcript is associated with the viral infection. Furthermore, the presence of the elongated IFN-beta transcript correlated with a decrease of IFN-beta protein in the medium and in cell extracts. Sucrose gradient analysis of cytoplasmic extracts showed that IFN-beta transcripts with elongated poly(A) tails were found in the nonpolysomal fractions, whereas the shorter transcripts could be detected in both polysomal and nonpolysomal fractions. A longer form of the IFN-beta mRNA was also found in the nonpolysomal fractions of cells not treated with transcriptional inhibitors. Thus, the observed regulation of IFN-beta mRNA is not entirely dependent on the inhibition of transcription. To our knowledge, this study provides the first example of a poly(A) tail elongation in somatic cells that negatively influences gene expression in vivo.
Mol Cell Biol 1996 Feb
PMID:Repression of beta interferon gene expression in virus-infected cells is correlated with a poly(A) tail elongation. 855 72

Alpha interferon is a potent growth inhibitor of Daudi Burkitt's lymphoma cells. We show here that alpha-interferon signaling interacted simultaneously with several components of the basic cell cycle machinery, causing cells to enter into a state that had many features characteristic of the G0 state. Within a few hours after alpha-interferon treatment, cyclin D3 mRNA and protein levels dropped to undetectable levels and, in parallel, the activities of cyclin A- and cyclin E-associated kinases were significantly reduced. The latter resulted from the rapid alpha-interferon-mediated elimination of cdc25A, a phosphatase that is required for antagonism of negative tyrosine phosphorylation of cdk2 in cyclin-cdk complexes. This regulation represents a novel mechanism through which an external inhibitory cytokine interacts with the cell cycle machinery. At later time points after alpha-interferon treatment, the levels of the 55-kDa slowly migrating hyperphosphorylated form of cyclin E and of cyclin A were also reduced. The antiproliferative effects were reversible, and cultures from which alpha interferon was removed reentered S phase after a lag that typically corresponded to approximately two doubling times. During this lag period, the expression of cyclin D3 and cyclin A, as well as of the cdc25A phosphatase, continued to be switched off, in spite of the removal of alpha interferon from the cell surface. In contrast, c-myc, which represents another downstream target gene that is subjected to negative regulation by alpha interferon, was relieved from suppression much earlier, concomitant with the decay in early signaling of the cytokine. The delayed pattern of cyclin reexpression provides evidence that alpha-interferon signaling imposes a G0-like state on this system.
Mol Cell Biol 1996 Jul
PMID:Alpha interferon suppresses the cyclin D3 and cdc25A genes, leading to a reversible G0-like arrest. 866 11

We have characterized a nuclear protein complex from B lymphoblastoid cell lines that binds to HLA class II promoters as detected by electrophoretic gel mobility shift assays (EMSA). This complex (C1) binds to three independent sites in the proximal DRA promoter which have not been identified previously as cis-acting elements. C1 is very abundant in Burkitt's lymphoma cell lines, but less abundant in "normal" B lymphoblastoid cell lines. The binding specificity of the C1 complex was analysed using competition experiments and chemical footprinting methods. Complexes with specificity similar to C1 also bind the DPA and DQA promoters. Though mutation of the sequences in the DRA promoter that severely reduced binding of the C1 complex had no effect on the ability of the DRA fragment to drive transcription of the reporter gene in transient expression or in vitro transcription assays, this conservation of binding sites among all class II promoters tested suggests functional relevance in transcription. In addition, complexes similar to C1 were observed in nuclear extracts from all cell lines examined, but minor differences in mobility appeared to correlate with class II expression. Thus, the C1 complex may act as a trans-acting factor in MHC class II expression.
Mol Immunol
PMID:Coordinate regulation of HLA class II genes: a novel DNA binding complex. 867 92

Interferon (IFN) is one of the potent antiproliferative cytokines and is used to treat some selected cancers. IFN arrests the growth of Burkitt Lymphoma derived cell line Daudi cells in the G1 phase. G1-to-S progression is controlled by positive and negative regulatory genes. Therefore, we investigated the effects of IFN on G1-controlling genes. Expression of cyclin-dependent kinases (Cdks 2, 3, 4, 5, 6), MO15/Cdk7, and cyclins E and H was studied to assess positive regulators, while p15Ink4B, p16Ink4, p18, p21Cip1, and p27Kip1 were assessed as negative regulators. Cdks 2, 4, 6 and cyclin E were markedly down-regulated. MO15/Cdk7 expression showed little change, but its regulatory subunit (cyclin H) was down-regulated like cyclin E. Expression of p15Ink4B and p16Ink4 was not observed. p18 was induced until 48 h and its expression returned to the initial level at 72 h. In contrast, p21Cip1 mRNA expression remained at the baseline level throughout IFN treatment, while the expression of p27Kip1 increased at 48 and 72 h. Taken together, these data indicate that IFN changes the messenger RNA of G1-controlling genes towards the suppression of G1-to-S transition.
Mol Cell Biochem 1995 Nov 22
PMID:Interferon modulates the messenger RNA of G1-controlling genes to suppress the G1-to-S transition in Daudi cells. 875 Nov 61

We determined, in a semiquantitative fashion, the level of expression of c-myc in 18 follicular center cell lymphomas and five non-neoplastic lymph nodes using reverse transcription and the polymerase chain reaction technique (RT-PCR). With this method, RNA is extracted from lymph node specimens and reverse-transcribed to produce cDNA, which is then amplified using primers specific for c-myc sequences that span introns, thus precluding amplification of genomic DNA. Amplified products are compared with beta2-microglobulin sequences co-amplified in each case as a control for the quality of RNA extracted, RT, and PCR amplification. Using cell lines derived from Burkitt's lymphomas, the RT-PCR method yielded results equivalent to standard Northern blot analysis yet required smaller quantities of tissue. The c-myc transcripts were detected in all lymphoma cases studied (seven high, 11 low expression) and in all non-neoplastic lymph nodes. High or low c-myc expression was based on comparison with non-neoplastic lymph nodes. We conclude that the RT-PCR method is a sensitive, reliable method for measuring gene expression in lymphoma tissues and may be useful for studying the role of c-myc in follicular lymphomas.
Diagn Mol Pathol 1996 Mar
PMID:Use of the polymerase chain reaction technique to determine c-myc expression in follicular center cell lymphoma. 891 41

Epstein-Barr virus (EBV) is capable of adopting three distinct forms of latency: the type III latency program, in which six EBV-encoded nuclear antigens (EBNAs) are expressed, and the type I and type II latency programs, in which only a single viral nuclear protein, EBNA1, is produced. Several groups have reported heavy CpG methylation of the EBV genome in Burkitt's lymphoma cell lines which maintain type I latency, and loss of viral genome methylation in tumor cell lines has been correlated with a switch to type III latency. Here, evidence that the type III latency program must be inactivated by methylation to allow EBV to enter the type I or type II restricted latency program is provided. The data demonstrates that the EBNA1 gene promoter, Qp, active in types I and II latency, is encompassed by a CpG island which is protected from methylation. CpG methylation inactivates the type III latency program and consequently allows the type I or II latency program to operate by alleviating EBNA1-mediated repression of Qp. Methylation of the type III latency EBNA gene promoter, Cp, appears to be essential to prevent type III latency, since EBNA1 is expressed in all latently infected cells and, as shown here, is the only viral antigen required for activation of Cp. EBV is thus a pathogen which subverts host-cell-determined methylation to regulate distinct genetic programs.
Mol Cell Biol 1997 Jan
PMID:Host-cell-determined methylation of specific Epstein-Barr virus promoters regulates the choice between distinct viral latency programs. 897 17

Regulation of immunoglobulin heavy chain (IgH) gene expression is controlled by a B cell-specific promoter, intronic enhancer and additional B cell-specific enhancer elements identified recently in the 3' end of the IgH locus. One of the latter elements, the IgH 3' enhancer, is of particular interest: (1) it is B cell-specific and active only in late B cell development; (2) in rodent plasmacytomas and in some human Burkitt's lymphomas it is part of a locus control region (LCR) that is involved in deregulation of the c-myc oncogene as a result of translocation into the IgH locus; and (3) it has been implicated in the mechanisms that control Ig gene class switch recombination. We have used a somatic cell hybridization approach to genetically analyse regulation of the activity of the IgH 3' enhancer. When mouse MPC11 plasmacytoma cells, in which the IgH 3' enhancer is active, are fused with fibroblasts, Ig expression is extinguished at the level of transcription. Here we show that in a MPC11 plasmacytoma x fibroblast environment, the IgH 3' enhancer is transcriptionally inactive. Furthermore, we demonstrate that binding of several B cell-specific transcription factors, essential for IgH 3' enhancer activity, is lacking, which may explain 3' enhancer inactivity, although the binding of repressors cannot be excluded. Moreover, the high expression level of c-myc, characteristic of the parental MPC11 cells carrying the t(12;15) translocation, is down-regulated in the hybrids to that in unfused fibroblasts. Therefore, inactivation of the IgH 3' enhancer is a multifactorial process affecting several transcription factors that control the cell-specific and developmental activity of the enhancer.
Mol Immunol 1997 Feb
PMID:Concomitant downregulation of IgH 3' enhancer activity and c-myc expression in a plasmacytoma x fibroblast environment: implications for dysregulation of translocated c-myc. 918 42

An in situ polymerase chain reaction (IS-PCR) technique was used to detect and differentiate strains of episomal Epstein-Barr virus (EBV) in infected cells. IS-PCR was performed on cell monolayers in eight-chamber glass slides using EBV type-specific primer pairs conserved within the EBV-encoded nuclear antigen (EBNA) 3C region. The amplicons in the cells were detected by in situ hybridization using EBV type-1 and type-2 specific 5'-biotinylated oligonucleotide probes and avidin-conjugated alkaline phosphatase as secondary reagent. This method was successfully used to identify EBV strains not only in Burkitt's lymphoma cell lines but also in B cells obtained from a patient with infectious mononucleosis. The technique described on this report is a reliable method to detect latently infected EBV-positive cells and can potentially be used to identify and type EBV strains present in clinical specimens.
Mol Cell Probes 1997 Jun
PMID:Detection and differentiation of Epstein-Barr virus strains by in situ polymerase chain reaction. 923 25


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