Epstein-Barr virus nuclear antigen EBNA3C/6 expression maintains the level of latent membrane protein 1 in G1-arrested cells

Allday, Martin J.; Farrell, Paul J.

doi:10.1128/jvi.68.6.3491-3498.1994

Cited by 84 publications

(38 citation statements)

References 43 publications

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“…These observations suggest that other cellular and/or viral factors play a crucial role in LMP1 gene regulation in B-cells. Another EBV factor, EBNA6, is involved in maintaining LMP1 expression at high levels in GI-arrested Raji B-cells (Allday et al, 1993;Allday and Farrell, 1994). In our conditions, treatment of the EBNA2-negative B-cell line Akata and of the EBNA6positive, EBNA2-negative B-cell lines P3HR1 and Daudi with 8-Br cAMP (and theophylline) did not stimulate expression of either form of LMP1.…”

Section: Discussionmentioning

confidence: 53%

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Response to cAMP levels of the Epstein-Barr virus EBNA2-inducible LMP1 oncogene and EBNA2 inhibition of a PP1-like activity.

Fåhræus

Palmqvist²,

Nerdstedt³

et al. 1994

The EMBO Journal

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The expression of the Epstein‐Barr virus LMP1 oncogene is regulated by viral and non‐viral factors in a tissue dependent fashion. The virus encoded transcription factor EBNA2 induces its expression in human B‐cells. However, this induction also requires the contribution of cellular and/or other viral factors. In nasopharyngeal carcinoma cells and in cells from Hodgkin's lymphoma, LMP1 gene transcription is independent of viral products. Here we show that the effect of a factor binding to a cAMP responsive‐like element (CRE) in the LMP1 gene transcription regulatory sequence (LRS) is essential for efficient promoter activity in the DG75 B‐cell line and that elevation of cAMP levels in the cells induces LRS‐derived CAT activity in a CRE dependent fashion. Incubation of two EBV‐immortalized B‐cell lines expressing endogenous EBNA2A with 8‐Br cAMP increased the levels of the latency associated 66 kDa LMP1 within 2 h. Interestingly, LMP1 expression in DG75 cells conferred resistance to the inhibitory effect of 8‐Br cAMP on cell proliferation. The protein phosphatase 1 and 2A (PP1 and PP2A, respectively) inhibitor okadaic acid also stimulated LRS‐CAT activity in DG75 cells. EBNA2A from an EBV‐immortalized B‐cell line co‐immunopurified with a PP1‐like protein. An EBNA2A fragment spanning residues 324‐436 fused to the GST protein specifically rescued a PP1/PP2A‐like component from DG75 cell extracts. This GST‐EBNA2A fusion product inhibited a PP1‐like activity in nuclear extracts from these cells.

show abstract

Section: Discussionmentioning

confidence: 53%

“…Nevertheless, LMP1 expression is delayed many hours until cells reach the GI/S boundary (Allday and Farrell, 1994 and references therein). Absence of LMP1 expression in EBNA2-positive cells has been reported on several other occasions (Walls et al, 1989;Azim et al, 1990;Cordier et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

Response to cAMP levels of the Epstein-Barr virus EBNA2-inducible LMP1 oncogene and EBNA2 inhibition of a PP1-like activity.

Fåhræus

Palmqvist²,

Nerdstedt³

et al. 1994

The EMBO Journal

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show abstract

“…The experiments shown in Figure 2 test this hypothesis. When LCLs are grown to a high density they largely accumulate early in the GI phase of the cell cycle when pRb is hypophosphorylated (Allday and Farrell, 1994). Therefore, cultures of IB4 and AS-3 LCLs were allowed to proliferate without changing or supplementing their growth medium for 6 days to achieve a quiescent population.…”

Section: Resultsmentioning

confidence: 99%

“…Cell cycle analysis by flow cytometry was performed on an EPICS profile analyser (Coulter), as described previously (Allday and Farrell, 1994). Actively proliferating cells or cells treated with cisplatin were also fixed and stained with acridine orange (5 ,tg/ml; Sigma, Poole, UK) for -30 min and examined by fluorescence microscopy to assess their morphology.…”

Section: Flow Cytometry and Fluorescence Microscopymentioning

confidence: 99%

“…Filters were probed with the following antibodies: an anti-p53 mAb DOI (Vojtesek et al, 1992), an anti-mutant p53 mAb PAb 240 (Gannon et al, 1990), an anti-Bcl2 mAb (Dako UK Ltd, High Wycombe, UK), an anti-pRb mAb (Pharmingen, San Diego, CA) and rabbit anti-Bax antiserum (Santa Cruz Biotechnology Inc., CA). The visualization process was performed essentially as described previously (Allday and Farrell, 1994).…”

Section: Western Blotting and Antibodiesmentioning

confidence: 99%

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DNA damage in human B cells can induce apoptosis, proceeding from G1/S when p53 is transactivation competent and G2/M when it is transactivation defective.

et al. 1995

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Epstein-Barr virus efficiently immortalizes human B cells without neutralizing the function of p53.

et al. 1995

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Epstein‐Barr virus (EBV) efficiently converts resting human B cells into actively cycling, immortal, lymphoblastoid cell lines (LCLs). Here we show that LCLs expressing the full complement of latent viral genes are very sensitive to DNA‐damaging agents such as cisplatin. The response includes a rapid accumulation of the tumour suppressor protein p53 and induction of the cellular genes mdm2 and WAF1/p21. Although the levels of Bcl2 protein and Bax mRNA appear unaltered by the activation of p53, within 24 h the majority of cells undergo apoptosis. Over‐expression of wild‐type p53 in an LCL also resulted in apoptosis; this was preceded by the dephosphorylation of the retinoblastoma gene product, pRb. Primary resting B cells showed no response to cisplatin and even after drug treatment, p53 remained undetectable. However, after infection with EBV, p53 gene expression was induced to a similar level to that found in mitogen‐activated B cells. When the physiologically activated primary B cells were exposed to cisplatin, although p53 accumulated as in LCLs, the outcome was growth‐arrest rather than gross cell death. We conclude that, in contrast to the transformation of fibroblasts by adenovirus, SV40 or HPV, when B cells become activated and immortalized by EBV they are sensitized to the p53‐mediated damage response. When the resulting LCLs are treated with genotoxic agents such as cisplatin, they are unable to arrest like normal cells because they are driven to proliferate by EBV and consequently undergo apoptosis.

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Epstein-Barr virus nuclear antigen EBNA3C/6 expression maintains the level of latent membrane protein 1 in G1-arrested cells

Cited by 84 publications

References 43 publications

Response to cAMP levels of the Epstein-Barr virus EBNA2-inducible LMP1 oncogene and EBNA2 inhibition of a PP1-like activity.

Response to cAMP levels of the Epstein-Barr virus EBNA2-inducible LMP1 oncogene and EBNA2 inhibition of a PP1-like activity.

DNA damage in human B cells can induce apoptosis, proceeding from G1/S when p53 is transactivation competent and G2/M when it is transactivation defective.

Epstein-Barr virus efficiently immortalizes human B cells without neutralizing the function of p53.

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