Abstract
IFNgamma is a pro-inflammatory cytokine that potentiates p53-independent apoptosis in a variety of cell types. STAT1 is the primary mediator of IFNgamma action. ZBP-89 is a transcription factor that binds to the G/C-rich elements and mediates p53-independent apoptosis. In this study, site-directed mutagenesis revealed that a G-rich element from +171 to +179 within the first intron of the STAT1 gene is critical for optimal STAT1 promoter activity. Electrophoretic mobility shift assays and promoter analysis revealed that ZBP-89 binds directly to this STAT1 G-rich element along with Sp1 and Sp3. Reduction of ZBP-89 with siRNA attenuated both basal and IFNgamma-induced STAT1 expression and subsequently diminished the activation of apoptotic markers, e.g. caspase-3 and PARP. Taken together, we conclude that ZBP-89 is required for constitutive STAT1 expression and in this way contributes to the ability of cells to be activated by IFNgamma.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Apoptosis / drug effects
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Caspases / metabolism
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Cell Line, Tumor
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DNA-Binding Proteins / deficiency
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DNA-Binding Proteins / genetics*
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DNA-Binding Proteins / metabolism*
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Gene Expression Regulation* / drug effects
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Humans
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Interferon-gamma / pharmacology
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Introns / genetics
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Poly(ADP-ribose) Polymerases / metabolism
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Promoter Regions, Genetic / genetics
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RNA Interference
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Rats
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Response Elements / genetics*
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STAT1 Transcription Factor
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Trans-Activators / genetics*
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Transcription Factors / deficiency
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Transcription Factors / genetics
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Transcription Factors / metabolism*
Substances
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DNA-Binding Proteins
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RNA, Small Interfering
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STAT1 Transcription Factor
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STAT1 protein, human
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Stat1 protein, rat
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Trans-Activators
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Transcription Factors
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ZNF148 protein, human
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Zfp148 protein, rat
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Interferon-gamma
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Poly(ADP-ribose) Polymerases
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Caspases