Abstract
We investigated whether Epstein--Barr virus (EBV) infection could counteract the antitumor effect of interferon (IFN)-alpha. EBV-negative subclones isolated from EBV-positive Burkitt's lymphoma (BL) cell lines Akata, Daudi and Mutu were found to fall into apoptosis after IFN-alpha treatment. On the other hand, EBV-positive counterparts exhibited striking resistance against IFN-alpha-induced apoptosis. Transfection of an individual EBV latent gene into EBV-negative BL cells revealed that EBV-encoded poly(A)(-) RNAs (EBERs) were responsible for IFN resistance. EBERs bound double-stranded (ds) RNA-activated protein kinase (PKR), a key mediator of the antiviral effect of IFN-alpha, and inhibited its phosphorylation. Transfection of dominant-negative PKR, which was catalytically inactive and could block phosphorylation of endogenous PKR, made EBV-negative BL cells resistant to IFN-alpha-induced apoptosis. Furthermore, EBERs did not bind mutant PKR, which was catalytically active but lacked dsRNA-binding activity, nor did they inhibit its phosphorylation. These results indicate that EBERs confer resistance to IFN-alpha-induced apoptosis via binding to PKR and inhibition of its phosphorylation. This is the first report that the virus counteracts IFN-induced apoptosis in virus-associated tumors.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Antineoplastic Agents / pharmacology*
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Antiviral Agents / pharmacology*
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Apoptosis / drug effects*
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Apoptosis / physiology
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Burkitt Lymphoma / enzymology
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Burkitt Lymphoma / pathology*
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Burkitt Lymphoma / virology
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Cell Transformation, Viral
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Clone Cells / drug effects
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Clone Cells / enzymology
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Clone Cells / pathology
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Clone Cells / virology
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Drug Resistance, Neoplasm / physiology*
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Drug Resistance, Viral / physiology*
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Epstein-Barr Virus Nuclear Antigens / analysis
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Gene Targeting
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Herpesvirus 4, Human / drug effects
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Herpesvirus 4, Human / genetics
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Herpesvirus 4, Human / isolation & purification
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Herpesvirus 4, Human / physiology*
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Humans
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Interferon-alpha / pharmacology*
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Neoplasm Proteins / antagonists & inhibitors*
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Neoplasm Proteins / metabolism
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Phosphorylation
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Protein Processing, Post-Translational
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RNA, Double-Stranded / metabolism
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RNA, Neoplasm / metabolism
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RNA, Viral / genetics
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RNA, Viral / physiology*
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Transfection
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Tumor Cells, Cultured / drug effects
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Tumor Cells, Cultured / enzymology
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Tumor Cells, Cultured / pathology
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Tumor Cells, Cultured / virology
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eIF-2 Kinase / antagonists & inhibitors*
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eIF-2 Kinase / metabolism
Substances
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Antineoplastic Agents
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Antiviral Agents
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Epstein-Barr Virus Nuclear Antigens
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Epstein-Barr virus encoded RNA 1
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Epstein-Barr virus encoded RNA 2
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Interferon-alpha
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Neoplasm Proteins
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RNA, Double-Stranded
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RNA, Neoplasm
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RNA, Viral
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eIF-2 Kinase
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EBV-encoded nuclear antigen 1