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Molecular and Cellular Biology, November 2001, p. 7163-7171, Vol. 21, No. 21
Department of Biochemistry, Molecular
Biology, and Cell Biology, Rice Institute for Biomedical Research,
Northwestern University, Evanston, Illinois 60208
Received 8 March 2001/Returned for modification 27 April
2001/Accepted 30 July 2001
Vertebrate cells express a family of heat shock transcription
factors (HSF1 to HSF4) that coordinate the inducible regulation of heat
shock genes in response to diverse signals. HSF1 is potent and
activated rapidly though transiently by heat shock, whereas HSF2 is a
less active transcriptional regulator but can retain its DNA binding
properties for extended periods. Consequently, the differential
activation of HSF1 and HSF2 by various stresses may be critical for
cells to survive repeated and diverse stress challenges and to provide
a mechanism for more precise regulation of heat shock gene expression.
Here we show, using a novel DNA binding and detection assay, that HSF1
and HSF2 are coactivated to different levels in response to a range of
conditions that cause cell stress. Above a low basal activity of both
HSFs, heat shock preferentially activates HSF1, whereas the amino acid
analogue azetidine or the proteasome inhibitor MG132 coactivates both
HSFs to different levels and hemin preferentially induces HSF2.
Unexpectedly, we also found that heat shock has dramatic adverse
effects on HSF2 that lead to its reversible inactivation coincident
with relocalization from the nucleus. The reversible inactivation of HSF2 is specific to heat shock and does not occur with other stressors or in cells expressing high levels of heat shock proteins. These results reveal that HSF2 activity is negatively regulated by heat and
suggest a role for heat shock proteins in the positive regulation of HSF2.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.21.7163-7171.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Stress-Specific Activation and Repression of
Heat Shock Factors 1 and 2


*
Corresponding author. Mailing address: Department of
Biochemistry, Molecular Biology, and Cell Biology, Rice Institute for Biomedical Research, Northwestern University, 2153 North Campus Dr.,
Evanston, IL 60208. Phone: (847) 491-3340. Fax: (847) 491-4461. E-mail:
r-morimoto{at}northwestern.edu.
Present address: IGEN International, Inc., Gaithersburg, MD 20877.
Present address: DyOGen, INSERM U309, Institut A. Bonniot, Domaine
de la Merci, 38706 La Tronche Cedex, France.
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