Mechanism of quercetin-induced suppression and delay of heat shock gene expression and thermotolerance development in HT-29 cells.
Previous studies have shown that a combination of low pH and quercetin (QCT) treatment following heat shock markedly suppresses and delays the expression of heat shock protein genes, particularly the HSP70 gene (Lee et al., Biochem. Biophys. Res. Commun., 186:1121-1128, 1992). The possible mechanism for alteration of gene expression by treatment with QCT at low pH was investigated in human colon carcinoma cells. Cells were heated at 45 degrees C for 15 min and then incubated at 37 degrees C for various times (0-12 h) with QCT (0.05-0.2 mM) at pH 7.4 or 6.5. Gel mobility-shift analysis of whole cell extracts from heated cells showed the formation of the heat shock transcription factor (HSF)-heat shock element (HSE) complex. Dissociation of HSF from the HSE of the human HSP70 promotor occurred within 4 h under both pH conditions. The kinetics of recovery were not affected by treatment with 0.1% dimethyl sulfoxide (DMSO). However, the dissociation of HSF-HSE complex was markedly delayed during treatment with a combination of low pH and QCT. In addition, in vitro transcription assays showed a suppression of initiation and elongation of HSP70 mRNA. These results may explain why the combination of low pH and QCT treatment suppresses and delays the HSP70 gene expression as well as thermotolerance development.
Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, Michigan 48073.
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Lee
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Erdos
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Hou
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Kim
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Kim
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Corry
D001483:Base Sequence; D002460:Cell Line; D003110:Colonic Neoplasms; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011794:Quercetin / Q000494:pharmacology*; D014157:Transcription Factors; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D009838:Oligodeoxyribonucleotides; D014157:Transcription Factors; D011794:Quercetin; D004121:Dimethyl Sulfoxide