Abstract
The signaling pathway by which environmental stresses activate heat shock factors (HSFs) is not completely understood. We show that the small GTPase rac1, and Rac1-regulated reactive oxygen species (ROS) play an important role in stress-stimulated heat shock response. A dominant-negative allele of Rac1 (Rac1N17) inhibits the hypoxia/reoxygenation and sodium arsenite-induced transcriptional activity of HSF-1 and the transcription of heat shock protein 70. Rac1N17 also suppresses the production of intracellular ROS induced by hypoxia/reoxygenation or sodium arsenite. Moreover, direct suppression of intracellular ROS levels by antioxidants decreases stress-stimulated HSF activity. However, expression of a constitutively active mutant of Rac1 (Rac1V12) in the absence of extracellular stresses does not increase intracellular ROS levels or induce the heat shock response. These results show that Rac1 is a necessary but insufficient component of the stress-induced signaling pathway that leads to ROS production, activation of HSFs, and transcription of heat shock proteins.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenoviridae / genetics
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Alleles
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Arsenites / pharmacology
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Blotting, Northern
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Chloramphenicol O-Acetyltransferase / metabolism
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DNA / metabolism
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DNA-Binding Proteins / metabolism
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Gene Expression Regulation
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Genes, Dominant
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HSP70 Heat-Shock Proteins / metabolism
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Heat Shock Transcription Factors
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Heat-Shock Proteins / metabolism*
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Humans
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Hydrogen Peroxide / pharmacology
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Hypoxia
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Immunoblotting
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JNK Mitogen-Activated Protein Kinases*
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Luciferases / metabolism
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MAP Kinase Kinase 4
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Microscopy, Fluorescence
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Mitogen-Activated Protein Kinase Kinases / metabolism
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Oxidation-Reduction*
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Oxidative Stress
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Oxygen / metabolism
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Plasmids / metabolism
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Reactive Oxygen Species / metabolism
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Signal Transduction
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Sodium Compounds / pharmacology
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Time Factors
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Transcription Factors
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Transcription, Genetic
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Transfection
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Tumor Cells, Cultured
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rac1 GTP-Binding Protein / metabolism*
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rac1 GTP-Binding Protein / physiology*
Substances
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Arsenites
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DNA-Binding Proteins
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Enzyme Inhibitors
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HSP70 Heat-Shock Proteins
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Heat Shock Transcription Factors
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Heat-Shock Proteins
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Reactive Oxygen Species
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Sodium Compounds
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Transcription Factors
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sodium arsenite
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DNA
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Hydrogen Peroxide
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Luciferases
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Chloramphenicol O-Acetyltransferase
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JNK Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 4
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Mitogen-Activated Protein Kinase Kinases
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rac1 GTP-Binding Protein
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Oxygen