Abstract
The apoptotic protein Hrk is expressed in hematopoietic progenitors after growth factor deprivation. Here we identify a silencer sequence in the 3' untranslated region of the hrk gene that binds to the transcriptional repressor DREAM in interleukin-3 (IL-3)-dependent hematopoietic progenitor cells, and abrogates the expression of reporter genes when located downstream of the open reading frame. In addition, the binding of DREAM to the hrk gene is reduced or eliminated when cells are cultured in the absence of IL-3 or treated with a calcium ionophore or a phosphatidylinositol 3-kinase-specific inhibitor, suggesting that both calcium mobilization and phosphorylation can regulate the transcriptional activity of DREAM. Furthermore, we have shown that DREAM is phosphorylated by a phosphatidylinositol 3-kinase-dependent, but Akt-independent pathway. In all cases, loss of the DREAM-DNA binding complex was correlated with increased levels of Hrk and apoptosis. These data suggest that IL-3 may trigger the activation of DREAM through different signaling pathways, which in turn binds to a silencer sequence in the hrk gene and blocks transcription, avoiding inappropriate cell death in hematopoietic progenitors.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3' Untranslated Regions / genetics
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Animals
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Apoptosis
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Calcium / metabolism
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Calcium-Binding Proteins*
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Carrier Proteins / antagonists & inhibitors
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Carrier Proteins / genetics*
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Carrier Proteins / metabolism
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Cell Line
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Enzyme Inhibitors / pharmacology
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Gene Expression Regulation / drug effects
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Gene Silencing / physiology*
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Genes, Reporter
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Hematopoietic Stem Cells / cytology
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Hematopoietic Stem Cells / metabolism*
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Humans
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Interleukin-3 / metabolism*
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Interleukin-3 / pharmacology
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Ionophores / pharmacology
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Kv Channel-Interacting Proteins
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Mice
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation / drug effects
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Protein Serine-Threonine Kinases*
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-akt
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Regulatory Sequences, Nucleic Acid / physiology
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Repressor Proteins / metabolism*
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Signal Transduction / drug effects
Substances
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3' Untranslated Regions
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Calcium-Binding Proteins
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Carrier Proteins
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Csen protein, mouse
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Enzyme Inhibitors
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Interleukin-3
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Ionophores
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KCNIP3 protein, human
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Kv Channel-Interacting Proteins
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Phosphoinositide-3 Kinase Inhibitors
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Proto-Oncogene Proteins
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Repressor Proteins
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AKT1 protein, human
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Calcium