Pervanadate induces the hyperphosphorylation but not the activation of human heat shock factor 1.
In this study, we evaluated the effects of pervanadate, a tyrosine phosphatase inhibitor, on the regulation and function of heat-shock factor 1 (HSF1) in HeLa cells. We showed that 50-100 microM pervanadate induced the hyperphosphorylation of the latent HSF1, as demonstrated by a retarded mobility of the HSF1 protein in SDS-polyacrylamide gel electrophoresis and as supported by the reversal of this mobility shift upon treatment of the cell extract with acid phosphatase. Pervanadate by itself had no effect on the monomeric stoichiometry and DNA-binding activity of HSF1. Upon heat shock, the pervanadate-induced hyperphosphorylated HSF1 formed DNA-binding trimers and translocated into the nuclear compartment. At high concentration (approximately 500 microM), pervanadate also induced the tyrosine phosphorylation of many cellular proteins and blunted the heat-induced transcription of hsp 70. N-acetyl cysteine inhibited these effects of pervanadate, suggesting a redox-based mechanism for its activity. Analysis of the activation of mitogen-activated protein kinases (MAPKs) using antibodies specific for the phospho-form (activated) of the kinases in Western blot showed that pervanadate activated extracellular signal-regulated kinase (ERK1/2), c-Jun-N-terminal kinase 1/2 (JNK1/2), and p-38 kinase. Pharmacological inhibitors of the ERK1/2 kinase pathway or the p38 kinase had little or no effect on the pervanadate-induced hyperphosphorylation of HSF1. Our results show that hyperphosphorylation of hHSF1 can occur prior to and independent of other events involved in the activation of hHSF1. The possibility that activation of the MAPK signaling cascade, notably JNK, may contribute to the hyperphosphorylation of human HSF1 (hHSF1) is discussed.
Park
J
J
Graduate Program in Cell and Developmental Biology, Rutgers State University of New Jersey, Piscataway, New Jersey, USA.
Liu
A Y
AY
D004268:DNA-Binding Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D006367:HeLa Cells; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors; D014638:Vanadates / Q000378:metabolism / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C000619706:HSF1 protein, human; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D014157:Transcription Factors; C076715:pervanadate; D014638:Vanadates; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases