Transcription of the human HSP70 gene is regulated during cell growth, in response to infection by certain DNA viruses and a plethora of conditions that cause physiological stress. Basal expression is modulated by serum stimulation and enhanced by many cellular and virus encoded oncoproteins that activate transcription. The level of basal HSP70 transcription varies among cell types and tissues and appears to be linked to a feedback loop that controls the activation of the stress-inducible response. One of the major questions on the stress response is to identify the biochemical sensor that responds to heat shock. To address this problem, we will continue our in vivo footprinting studies and in vitro activation of heat shock transcription factor (HSF) experiments to understand how physiological stress activates the DNA binding domain of HSF. We will also investigate the events involved in oligomerization and transcriptional activity of HSF and finally, we will study the events involved in attenuation of the heat shock transcriptional response. To obtain a detailed understanding of these events, we will dissect the binding and activation domains of two recently cloned mouse HSF genes, mHSF-1 that exhibits inducible sequence-specific DNA binding and mHSF-2 that exhibits constitutive DNA binding activity. We will overexpress the wild type and mutant factors to obtain a detailed biochemical analysis of HSF function in reconstituted transcription assays. The availability of cloned vertebrate heat shock and HSF genes will allow us to examine their expression during early mouse development and differentiation and to create transgenic mice which exhibit an altered stress response. This will be particularly important in the brain in which most cells types do not appear to have a stress response. Finally, we will investigate the role of the stress response in conditions of pathophysiology and disease including cancer, inflammation and aging.
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