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The p38 signaling pathway upregulates expression of the Epstein-Barr virus LMP1 oncogene.

Journal article
Authors Pegah Johansson
Ann Jansson
Ulla Rüetschi
Lars Rymo
Published in Journal of virology
Volume 84
Issue 6
Pages 2787-97
ISSN 1098-5514
Publication year 2010
Published at Institute of Biomedicine, Department of Clinical Chemistry and Transfusion Medicine
Pages 2787-97
Language en
Links dx.doi.org/10.1128/JVI.01052-09
Keywords Cell Line, Cyclic AMP Response Element-Binding Protein, genetics, metabolism, Gene Expression Regulation, Viral, Herpesvirus 4, Human, genetics, metabolism, Humans, MAP Kinase Signaling System, physiology, Oncogene Proteins, Viral, genetics, metabolism, Promoter Regions, Genetic, Proteins, genetics, metabolism, RNA, Small Interfering, genetics, metabolism, RNA, Viral, genetics, metabolism, Up-Regulation, Viral Matrix Proteins, genetics, metabolism, p38 Mitogen-Activated Protein Kinases, antagonists & inhibitors, genetics, metabolism
Subject categories Virology, Cell and molecular biology, Clinical chemistry

Abstract

The Epstein-Barr virus (EBV)-encoded LMP1 oncogene has a role in transformation, proliferation, and metastasis of several EBV-associated tumors. Furthermore, LMP1 is critically involved in transformation and growth of EBV-immortalized B cells in vitro. The oncogenic properties of LMP1 are attributed to its ability to upregulate anti-apoptotic proteins and growth signals. The transcriptional regulation of LMP1 is dependent on the context of cellular and viral proteins present in the cell. Here, we investigated the effect of several signaling pathways on the regulation of LMP1 expression. Inhibition of p38 signaling, using p38-specific inhibitors SB203580 and SB202190, downregulated LMP1 in estrogen-induced EREB2.5 cells. Similarly, p38 inhibition decreased trichostatin A-induced LMP1 expression in P3HR1 cells. Exogenous expression of p38 in lymphoblastoid cell lines (LCLs) led to an increase in LMP1 promoter activity in reporter assays, and this activation was mediated by the previously identified CRE site in the promoter. Inhibition of p38 by SB203580 and p38-specific small interfering RNA (siRNA) also led to a modest decrease in endogenous LMP1 expression in LCLs. Chromatin immunoprecipitation indicated decreased binding of CREB-ATF1 to the CRE site in the LMP1 promoter after inhibition of the p38 pathway in EREB2.5 cells. Taken together, our results suggest that an increase in p38 activation upregulates LMP1 expression. Since p38 is activated in response to stimuli such as stress or possibly primary infection, a transient upregulation of LMP1 in response to p38 may allow the cells to escape apoptosis. Since the p38 pathway itself is activated by LMP1, our results also suggest the presence of an autoregulatory loop in LMP1 upregulation.

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