Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) K13/vFLIP (viral Flice-inhibitory protein) induces transcription of numerous genes through NF-κB activation, including pro-inflammatory cytokines, which contribute to the pathogenesis of Kaposi's sarcoma (KS). In this study, we report that KSHV vFLIP induces the expression of the NF-κB regulatory proteins A20, ABIN-1 and ABIN-3 (A20-binding NF-κB inhibitors) in primary human endothelial cells, and that KS spindle cells express A20 in KS tissue. In reporter assays, A20 strongly impaired vFLIP-induced NF-κB activation in 293T cells, but ABIN-1 and ABIN-3 did not. Mutational analysis established that the C-terminal domain (residues 427-790) is critical for A20 modulation of NF-κB, but the ubiquitin-editing OTU (ovarian tumor) domain is not. In functional assays, A20 inhibited vFLIP-induced expression of the chemokine IP-10, reduced vFLIP-induced cell proliferation and increased IKK1 protein levels. Thus, we demonstrate that A20 negatively regulates NF-κB activation directly induced by KSHV vFLIP. By attenuating excessive and prolonged vFLIP-induced NF-κB activation that could be harmful to KSHV-infected cells, A20 likely has an important role in the pathogenesis of KSHV-associated diseases, in which vFLIP is expressed.
Publication types
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Research Support, N.I.H., Intramural
MeSH terms
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Animals
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Chemokine CXCL10 / metabolism
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DNA-Binding Proteins / biosynthesis
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / metabolism*
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Endothelial Cells / cytology
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Endothelial Cells / metabolism
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Herpesvirus 8, Human / genetics
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Herpesvirus 8, Human / metabolism*
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Humans
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Intracellular Signaling Peptides and Proteins / biosynthesis
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Mice
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NF-kappa B / antagonists & inhibitors*
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NF-kappa B / genetics
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NF-kappa B / metabolism
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Nuclear Proteins / biosynthesis
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Proteins / genetics
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Proteins / metabolism
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Sarcoma, Kaposi / genetics
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Sarcoma, Kaposi / metabolism
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Sarcoma, Kaposi / pathology
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Sarcoma, Kaposi / virology*
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Transduction, Genetic
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Transfection
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Tumor Necrosis Factor alpha-Induced Protein 3
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Viral Proteins / antagonists & inhibitors
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Viral Proteins / genetics
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Viral Proteins / metabolism*
Substances
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CXCL10 protein, human
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Chemokine CXCL10
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DNA-Binding Proteins
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Intracellular Signaling Peptides and Proteins
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NF-kappa B
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Nuclear Proteins
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Proteins
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TNIP1 protein, human
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TNIP3 protein, human
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Viral Proteins
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viral FLIP protein, Human herpesvirus 8
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TNFAIP3 protein, human
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Tumor Necrosis Factor alpha-Induced Protein 3