Induction of the DNA-binding and transcriptional activities of heat shock factor 1 is uncoupled in Xenopus oocytes.

The DNA-binding and transcriptional activities of the heat shock transcription factor 1 (HSF1) are repressed under normal conditions and rapidly upregulated by heat stress. Here, we tested for the ability of various stress agents to activate HSF1 in the Xenopus oocyte model system. The HSE-binding activity of HSF1 was induced by a number of chemical stresses including cadmium, aluminum, iron, mercury, arsenite, ethanol, methanol, and salicylate. HSE-binding was not induced by several stresses known to induce the synthesis of hsps in other cell types in different organisms including zinc, copper, cobalt, manganese, recovery from anoxia, UV-irradiation, and increased pH. The inability of several known inducers of the stress response to activate the HSE-binding ability of HSF1 suggests that certain stress activation pathways may be absent or inactive in oocytes. The transcriptional activity of oocyte HSF1 was induced by heat, cadmium, and arsenite, but many of the agents that induced HSE-binding failed to stimulate HSF1-mediated transcription. The apparent uncoupling of inducible HSE-binding and transcriptional activities of HSF1 under a variety of stress regimes indicates that these events are regulated by independent mechanisms in the oocyte.