Okadaic acid markedly potentiates the heat-induced hsp 70 promoter activity.
The effects of okadaic acid (OA), a potent and specific inhibitor of serine/threonine phosphatases 2A and 1, on the transient expression of a human hsp 70 promoter-linked chloramphenicol acetyltransferase gene transfected into N-18 mouse neuroblastoma cells were determined. Assays of reporter gene activity showed that nanomolar concentrations of OA markedly potentiated the heat-induced (but not the basal) expression of pHBCAT, a full-length hsp 70 promoter-driven chloramphenicol acetyltransferase gene construct. This effect of OA was dose-dependent and promoter-specific and appeared to be attributable to inhibition of protein phosphatase 2A as opposed to protein phosphatase 1. The ability of OA to potentiate the heat-induced expression of pHBCAT appeared to be a feature common to several different cell types examined. We propose that the heat-induced transcriptional activation of heat shock genes is associated with the phosphorylation of component(s) of the transcription complex and that OA enhances this phosphorylation, thereby potentiating the heat-induced hsp 70 promoter activity.
Chang
N T
NT
Department of Biological Sciences, Rutgers, State University of New Jersey, Piscataway 08855-1059.
Huang
L E
LE
Liu
A Y
AY
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D004988:Ethers, Cyclic / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006367:HeLa Cells; D006360:Heat-Shock Proteins / Q000235:genetics*; D006358:Hot Temperature; D006801:Humans; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D009447:Neuroblastoma; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000187:drug effects; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D011994:Recombinant Proteins / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014407:Tumor Cells, Cultured
D004988:Ethers, Cyclic; D006360:Heat-Shock Proteins; D011994:Recombinant Proteins; D019319:Okadaic Acid; D015500:Chloramphenicol O-Acetyltransferase; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2