Intracellular distribution of 73 000 and 72 000 dalton heat shock proteins in HeLa cells

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Abstract
Intracellular localization of 73 000 and 72 000 dalton heat shock proteins (HSP73/72) in HeLa cells that were heat shocked or treated with chemical stressors was investigated using indirect immunofluorescent staining. The antiserum used specifically recognized the HSP73/72 in HeLa cells, and HSPs were increased by heating cells at 42°C for 2 or 4 h and by prior treatment with chemical stressors (sodium arsenite, cadmium chloride, 8-hydroxyquinoline and ethanol). There was diffuse cytoplasmic staining at 37°C., whereas nucleoli were stained brightly when cells were heated at 42°C for 2 h. This rapid accumulation of HSP73/72 in the nucleoli was not inhibited by cycloheximide (50 μg/ml). Translocation of HSPs to the nucleoli was specific for heat because no translocation was induced by treatment with chemical stressors. When the cells were returned to 37°C after heating, the HSPs in their nucleoli disappeared rapidly and diffuse cytoplasmic staining was present after 6–9 h. Our results suggest that the transient accumulation of HSP73/72 in HeLa cell nucleoli that is induced by heat shock is not correlated with the development of thermotolerance obtained in other cell systems.