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XB-ART-15536
Mol Cell Biol 1998 Feb 01;182:906-18. doi: 10.1128/MCB.18.2.906.
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Intramolecular repression of mouse heat shock factor 1.

Farkas T , Kutskova YA , Zimarino V .


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The pathway leading to transcriptional activation of heat shock genes involves a step of heat shock factor 1 (HSF1) trimerization required for high-affinity binding of this activator protein to heat shock elements (HSEs) in the promoters. Previous studies have shown that in vivo the trimerization is negatively regulated at physiological temperatures by a mechanism that requires multiple hydrophobic heptad repeats (HRs) which may form a coiled coil in the monomer. To investigate the minimal requirements for negative regulation, in this work we have examined mouse HSF1 translated in rabbit reticulocyte lysate or extracted from Escherichia coli after limited expression. We show that under these conditions HSF1 behaves as a monomer which can be induced by increases in temperature to form active HSE-binding trimers and that mutations of either HR region cause activation in both systems. Furthermore, temperature elevations and acidic buffers activate purified HSF1, and mild proteolysis excises fragments which form HSE-binding oligomers. These results suggest that oligomerization can be repressed in the monomer, as previously proposed, and that repression can be relieved in the apparent absence of regulatory proteins. An intramolecular mechanism may be central for the regulation of this transcription factor in mammalian cells, although not necessarily sufficient.

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Species referenced: Xenopus
Genes referenced: hsf1

References [+] :
Abdella, A new cleavable reagent for cross-linking and reversible immobilization of proteins. 1979, Pubmed