Abstract
The FLI-1 transcription factor is a member of the ETS gene family, most closely related to ERG. In this study, the FLI-1 protein products were characterized using a specific monoclonal antibody previously developed against bacterially expressed protein. In the human T-cell line Jurkat, both isoforms of FLI-1, p51 and p48, are phosphorylated, primarily on serine residues. FLI-1 phosphorylation is increased by a Ca(2+)-mediated process, and inhibitor studies indicate that protein phosphatase 2A, at least in part, controls FLI-1 phosphorylation level. FLI-1 phosphorylation is not stimulated by phorbal 12-myristate 13-acetate (PMA), a protein kinase C activator, and in this it differs from ERG protein phosphorylation. The p51 isoform has a half-life of 105 min, and p48 has a half-life of 80 min; in contrast, the ERG protein is much more stable with a half-life of 21 h. Newly synthesized FLI-1 protein decreased during human T cell activation. Our data suggest that although the FLI-1 and ERG genes are highly homologous, their distinct properties may contribute to their different roles in gene regulation.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Antibodies, Monoclonal
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Cantharidin / pharmacology
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Cell Line, Tumor
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DNA-Binding Proteins / metabolism*
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Gene Expression Regulation
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Genes, Tumor Suppressor
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Humans
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Ionomycin / pharmacology
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Jurkat Cells
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Lymphocyte Activation
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Phosphoprotein Phosphatases / antagonists & inhibitors
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Phosphoprotein Phosphatases / metabolism
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Phosphoproteins / metabolism*
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Protein Isoforms / metabolism
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Protein Phosphatase 2
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Protein Processing, Post-Translational
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Proto-Oncogene Protein c-fli-1
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Proto-Oncogene Proteins / metabolism*
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T-Lymphocytes / drug effects
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T-Lymphocytes / metabolism*
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T-Lymphocytes / physiology
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Tetradecanoylphorbol Acetate / pharmacology
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Trans-Activators / metabolism*
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Transcription Factors
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Tumor Suppressor Proteins
Substances
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Antibodies, Monoclonal
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DNA-Binding Proteins
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Phosphoproteins
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Protein Isoforms
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Proto-Oncogene Protein c-fli-1
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Proto-Oncogene Proteins
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TP63 protein, human
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Trans-Activators
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Transcription Factors
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Tumor Suppressor Proteins
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Ionomycin
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Phosphoprotein Phosphatases
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Protein Phosphatase 2
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Cantharidin
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Tetradecanoylphorbol Acetate