scholarly journals A heat shock transcription factor with reduced activity suppresses a yeast HSP70 mutant.

1995 ◽  
Vol 15 (9) ◽  
pp. 4890-4897 ◽  
Author(s):  
J T Halladay ◽  
E A Craig
Keyword(s):  
Growth Rate ◽  
Transcription Factor ◽  
Steady State ◽  
Heat Shock ◽  
Heat Shock Transcription Factor ◽  
Single Amino Acid ◽  
Slight Reduction ◽  
Wild Type ◽  
Band Shift ◽  
Poor Growth

Strains carrying deletions in both the SSA1 and SSA2 HSP70 genes of Saccharomyces cerevisiae exhibit pleiotropic phenotypes, including the inability to grow at 37 degrees C or higher, reduced growth rate at permissive temperatures, increased HSP gene expression, and constitutive thermotolerance. A screen for extragenic suppressors of the ssa1 ssa2 slow-growth phenotype identified a spontaneous dominant suppressor mutation, EXA3-1 (R.J. Nelson, M. Heschl, and E.A. Craig, Genetics 131:277-285, 1992). Here we report that EXA3-1 is an allele of HSF1, which encodes the heat shock transcription factor (HSF). Strains containing the EXA3-1 allele in a wild-type background exhibit a 10- to 15-fold reduction in HSF activity during steady-state growth conditions as well as a delay in the accumulation of the SSA4, HSP26, and HSP104 mRNAs after a heat shock. EXA3-1-mediated suppression is the result of a single amino acid substitution of a highly conserved residue in the HSF DNA-binding domain which drastically reduces the ability of HSF to bind to heat shock elements as evaluated by band shift analysis. Together, these results indicate that the poor growth of ssa1 ssa2 strains is the result, at least in part, of the overproduction of a deleterious heat shock protein(s). This conclusion is supported by the fact that the levels of at least some heat shock proteins are reduced in ssa1 ssa2 cells containing the EXA3-1 allele. Surprisingly, strains containing the EXA3-1 allele in a wild-type HSP70 background grow early as well as the wild-type strain over a wide temperature range, displaying only a slight reduction in growth rate at 37 degrees Celsius, indicating that cells contain significantly more HSF activity than is require for growth under steady-state conditions.

scholarly journals Activation of the DNA-binding ability of human heat shock transcription factor 1 may involve the transition from an intramolecular to an intermolecular triple-stranded coiled-coil structure.

1994 ◽  
Vol 14 (11) ◽  
pp. 7557-7568 ◽  
Author(s):  
J Zuo ◽  
R Baler ◽  
G Dahl ◽  
R Voellmy
Keyword(s):  
Transcription Factor ◽  
Heat Stress ◽  
Heat Shock ◽  
Dna Binding ◽  
Hydrophobic Interactions ◽  
Coiled Coil ◽  
Heat Shock Transcription Factor ◽  
Single Amino Acid ◽  
Binding Ability ◽  
Heat Shock Element

Heat stress regulation of human heat shock genes is mediated by human heat shock transcription factor hHSF1, which contains three 4-3 hydrophobic repeats (LZ1 to LZ3). In unstressed human cells (37 degrees C), hHSF1 appears to be in an inactive, monomeric state that may be maintained through intramolecular interactions stabilized by transient interaction with hsp70. Heat stress (39 to 42 degrees C) disrupts these interactions, and hHSF1 homotrimerizes and acquires heat shock element DNA-binding ability. hHSF1 expressed in Xenopus oocytes also assumes a monomeric, non-DNA-binding state and is converted to a trimeric, DNA-binding form upon exposure of the oocytes to heat shock (35 to 37 degrees C in this organism). Because endogenous HSF DNA-binding activity is low and anti-hHSF1 antibody does not recognize Xenopus HSF, we employed this system for mapping regions in hHSF1 that are required for the maintenance of the monomeric state. The results of mutagenesis analyses strongly suggest that the inactive hHSF1 monomer is stabilized by hydrophobic interactions involving all three leucine zippers which may form a triple-stranded coiled coil. Trimerization may enable the DNA-binding function of hHSF1 by facilitating cooperative binding of monomeric DNA-binding domains to the heat shock element motif. This view is supported by observations that several different LexA DNA-binding domain-hHSF1 chimeras bind to a LexA-binding site in a heat-regulated fashion, that single amino acid replacements disrupting the integrity of hydrophobic repeats render these chimeras constitutively trimeric and DNA binding, and that LexA itself binds stably to DNA only as a dimer but not as a monomer in our assays.

Role of heat shock transcription factor in yeast metallothionein gene expression

1991 ◽  
Vol 11 (7) ◽  
pp. 3676-3681
Author(s):  
W M Yang ◽  
W Gahl ◽  
D Hamer
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Heat Shock ◽  
Gene Transcription ◽  
Heat Shock Factor ◽  
Heat Shock Transcription Factor ◽  
Wild Type ◽  
Promoter Sequences ◽  
Metallothionein Gene ◽  
Upstream Promoter

The induction of Saccharomyces cerevisiae metallothionein gene transcription by Cu and Ag is mediated by the ACE1 transcription factor. In an effort to detect additional stimuli and factors that regulate metallothionein gene transcription, we isolated a Cu-resistant suppressor mutant of an ACE1 deletion strain. Even in the absence of metals, the suppressor mutant exhibited high basal levels of metallothionein gene transcription that required upstream promoter sequences. The suppressor gene was cloned, and its predicted product was shown to correspond to yeast heat shock transcription factor with a single-amino-acid substitution in the DNA-binding domain. The mutant heat shock factor bound strongly to metallothionein gene upstream promoter sequences, whereas wild-type heat shock factor interacted weakly with the same region. Heat treatment led to a slight but reproducible induction of metallothionein gene expression in both wild-type and suppressor strains, and Cd induced transcription in the mutant strain. These studies provide evidence for multiple pathways of metallothionein gene transcriptional regulation in S. cerevisiae.

Activation of the DNA-binding ability of human heat shock transcription factor 1 may involve the transition from an intramolecular to an intermolecular triple-stranded coiled-coil structure

1994 ◽  
Vol 14 (11) ◽  
pp. 7557-7568
Author(s):  
J Zuo ◽  
R Baler ◽  
G Dahl ◽  
R Voellmy
Keyword(s):  
Transcription Factor ◽  
Heat Stress ◽  
Heat Shock ◽  
Dna Binding ◽  
Hydrophobic Interactions ◽  
Coiled Coil ◽  
Heat Shock Transcription Factor ◽  
Single Amino Acid ◽  
Binding Ability ◽  
Heat Shock Element

Heat stress regulation of human heat shock genes is mediated by human heat shock transcription factor hHSF1, which contains three 4-3 hydrophobic repeats (LZ1 to LZ3). In unstressed human cells (37 degrees C), hHSF1 appears to be in an inactive, monomeric state that may be maintained through intramolecular interactions stabilized by transient interaction with hsp70. Heat stress (39 to 42 degrees C) disrupts these interactions, and hHSF1 homotrimerizes and acquires heat shock element DNA-binding ability. hHSF1 expressed in Xenopus oocytes also assumes a monomeric, non-DNA-binding state and is converted to a trimeric, DNA-binding form upon exposure of the oocytes to heat shock (35 to 37 degrees C in this organism). Because endogenous HSF DNA-binding activity is low and anti-hHSF1 antibody does not recognize Xenopus HSF, we employed this system for mapping regions in hHSF1 that are required for the maintenance of the monomeric state. The results of mutagenesis analyses strongly suggest that the inactive hHSF1 monomer is stabilized by hydrophobic interactions involving all three leucine zippers which may form a triple-stranded coiled coil. Trimerization may enable the DNA-binding function of hHSF1 by facilitating cooperative binding of monomeric DNA-binding domains to the heat shock element motif. This view is supported by observations that several different LexA DNA-binding domain-hHSF1 chimeras bind to a LexA-binding site in a heat-regulated fashion, that single amino acid replacements disrupting the integrity of hydrophobic repeats render these chimeras constitutively trimeric and DNA binding, and that LexA itself binds stably to DNA only as a dimer but not as a monomer in our assays.

Absence of heat shock transcription factor 1 retards the regrowth of atrophied soleus muscle in mice

2011 ◽  
Vol 111 (4) ◽  
pp. 1142-1149 ◽  
Author(s):  
Kazuyuki Yasuhara ◽  
Yoshitaka Ohno ◽  
Atsushi Kojima ◽  
Kenji Uehara ◽  
Moroe Beppu ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Stress Response ◽  
Heat Shock ◽  
Soleus Muscle ◽  
Heat Shock Transcription Factor ◽  
Hindlimb Suspension ◽  
Wild Type ◽  
Muscle Weight ◽  
Cross Sectional ◽  
Transcription Factor 1

Effects of heat shock transcription factor 1 (HSF1) gene on the regrowth of atrophied mouse soleus muscles were studied. Both HSF1-null and wild-type mice were subjected to continuous hindlimb suspension for 2 wk followed by 4 wk of ambulation recovery. There was no difference in the magnitude of suspension-related decrease of muscle weight, protein content, and the cross-sectional area of muscle fibers between both types of mice. However, the regrowth of atrophied soleus muscle in HSF1-null mice was slower compared with that in wild-type mice. Lower baseline expression level of HSP25, HSC70, and HSP72 were noted in soleus muscle of HSF1-null mice. Unloading-associated downregulation and reloading-associated upregulation of HSP25 and HSP72 mRNA were observed not only in wild-type mice but also in HSF1-null mice. Reloading-associated upregulation of HSP72 and HSP25 during the regrowth of atrophied muscle was observed in wild-type mice. Minor and delayed upregulation of HSP72 at mRNA and protein levels was also seen in HSF1-null mice. Significant upregulations of HSF2 and HSF4 were observed immediately after the suspension in HSF1-null mice, but not in wild-type mice. Therefore, HSP72 expression in soleus muscle might be regulated by the posttranscriptional level, but not by the stress response. Evidence from this study suggested that the upregulation of HSPs induced by HSF1-associated stress response might play, in part, important roles in the mechanical loading (stress)-associated regrowth of skeletal muscle.

scholarly journals Role of chromatin and Xenopus laevis heat shock transcription factor in regulation of transcription from the X. laevis hsp70 promoter in vivo.

1995 ◽  
Vol 15 (11) ◽  
pp. 6013-6024 ◽  
Author(s):  
N Landsberger ◽  
A P Wolffe
Keyword(s):  
Transcription Factor ◽  
Heat Shock ◽  
Xenopus Laevis ◽  
Heat Shock Transcription Factor ◽  
Chromatin Assembly ◽  
Regulation Of Transcription ◽  
Wild Type ◽  
Hsp70 Promoter ◽  
Chromatin Template

Xenopus laevis oocytes activate transcription from the Xenopus hsp70 promoter within a chromatin template in response to heat shock. Expression of exogenous Xenopus heat shock transcription factor 1 (XHSF1) causes the activation of the wild-type hsp70 promoter within chromatin. XHSF1 activates transcription at normal growth temperatures (18 degrees C), but heat shock (34 degrees C) facilitates transcriptional activation. Titration of chromatin in vivo leads to constitutive transcription from the wild-type hsp70 promoter. The Y box elements within the hsp70 promoter facilitate transcription in the presence or absence of chromatin. The presence of the Y box elements prevents the assembly of canonical nucleosomal arrays over the promoter and facilitates transcription. In a mutant hsp70 promoter lacking Y boxes, exogenous XHSF1 activates transcription from a chromatin template much more efficiently under heat shock conditions. Activation of transcription from the mutant promoter by exogenous XHSF1 correlates with the disappearance of a canonical nucleosomal array over the promoter. Chromatin structure on a mutant hsp70 promoter lacking Y boxes can restrict XHSF1 access; however, on both mutant and wild-type promoters, chromatin assembly can also restrict the function of the basal transcriptional machinery. We suggest that chromatin assembly has a physiological role in establishing a transcriptionally repressed state on the Xenopus hsp70 promoter in vivo.

scholarly journals Conserved Region 2.1 of Escherichia coli Heat Shock Transcription Factor σ32 Is Required for Modulating both Metabolic Stability and Transcriptional Activity

2004 ◽  
Vol 186 (22) ◽  
pp. 7474-7480 ◽  
Author(s):  
Mina Horikoshi ◽  
Takashi Yura ◽  
Sachie Tsuchimoto ◽  
Yoshihiro Fukumori ◽  
Masaaki Kanemori
Keyword(s):  
Escherichia Coli ◽  
Transcription Factor ◽  
Heat Shock ◽  
Transcriptional Activity ◽  
Heat Shock Transcription Factor ◽  
Metabolic Stability ◽  
Wild Type ◽  
Shock Proteins ◽  
Insight Into

ABSTRACT Escherichia coli heat shock transcription factor σ32 is rapidly degraded in vivo, with a half-life of about 1 min. A set of proteins that includes the DnaK chaperone team (DnaK, DnaJ, GrpE) and ATP-dependent proteases (FtsH, HslUV, etc.) are involved in degradation of σ32. To gain further insight into the regulation of σ32 stability, we isolated σ32 mutants that were markedly stabilized. Many of the mutants had amino acid substitutions in the N-terminal half (residues 47 to 55) of region 2.1, a region highly conserved among bacterial σ factors. The half-lives ranged from about 2-fold to more than 10-fold longer than that of the wild-type protein. Besides greater stability, the levels of heat shock proteins, such as DnaK and GroEL, increased in cells producing stable σ32. Detailed analysis showed that some stable σ32 mutants have higher transcriptional activity than the wild type. These results indicate that the N-terminal half of region 2.1 is required for modulating both metabolic stability and the activity of σ32. The evidence suggests that σ32 stabilization does not result from an elevated affinity for core RNA polymerase. Region 2.1 may, therefore, be involved in interactions with the proteolytic machinery, including molecular chaperones.

scholarly journals Heat shock transcription factor activates transcription of the yeast metallothionein gene.

1991 ◽  
Vol 11 (3) ◽  
pp. 1232-1238 ◽  
Author(s):  
P Silar ◽  
G Butler ◽  
D J Thiele
Keyword(s):  
Transcription Factor ◽  
Amino Acid ◽  
Heat Shock ◽  
Target Genes ◽  
Heat Shock Transcription Factor ◽  
Single Amino Acid ◽  
Heat Shock Gene ◽  
Yeast Saccharomyces Cerevisiae ◽  
Metallothionein Gene ◽  
Single Amino Acid Change

In the yeast Saccharomyces cerevisiae, transcription of the metallothionein gene CUP1 is induced by copper and silver. Strains with a complete deletion of the ACE1 gene, the copper-dependent activator of CUP1 transcription, are hypersensitive to copper. These strains have a low but significant basal level of CUP1 transcription. To identify genes which mediate basal transcription of CUP1 or which activate CUP1 in response to other stimuli, we isolated an extragenic suppressor of an ace1 deletion. We demonstrate that a single amino acid substitution in the heat shock transcription factor (HSF) DNA-binding domain dramatically enhances CUP1 transcription while reducing transcription of the SSA3 gene, a member of the yeast hsp70 gene family. These results indicate that yeast metallothionein transcription is under HSF control and that metallothionein biosynthesis is important in response to heat shock stress. Furthermore, our results suggest that HSF may modulate the magnitude of individual heat shock gene transcription by subtle differences in its interaction with heat shock elements and that a single-amino-acid change can dramatically alter the activity of the factor for different target genes.

Heat shock transcription factor activates transcription of the yeast metallothionein gene

1991 ◽  
Vol 11 (3) ◽  
pp. 1232-1238 ◽  
Author(s):  
P Silar ◽  
G Butler ◽  
D J Thiele
Keyword(s):  
Transcription Factor ◽  
Amino Acid ◽  
Heat Shock ◽  
Target Genes ◽  
Heat Shock Transcription Factor ◽  
Single Amino Acid ◽  
Heat Shock Gene ◽  
Yeast Saccharomyces Cerevisiae ◽  
Metallothionein Gene ◽  
Single Amino Acid Change

In the yeast Saccharomyces cerevisiae, transcription of the metallothionein gene CUP1 is induced by copper and silver. Strains with a complete deletion of the ACE1 gene, the copper-dependent activator of CUP1 transcription, are hypersensitive to copper. These strains have a low but significant basal level of CUP1 transcription. To identify genes which mediate basal transcription of CUP1 or which activate CUP1 in response to other stimuli, we isolated an extragenic suppressor of an ace1 deletion. We demonstrate that a single amino acid substitution in the heat shock transcription factor (HSF) DNA-binding domain dramatically enhances CUP1 transcription while reducing transcription of the SSA3 gene, a member of the yeast hsp70 gene family. These results indicate that yeast metallothionein transcription is under HSF control and that metallothionein biosynthesis is important in response to heat shock stress. Furthermore, our results suggest that HSF may modulate the magnitude of individual heat shock gene transcription by subtle differences in its interaction with heat shock elements and that a single-amino-acid change can dramatically alter the activity of the factor for different target genes.

scholarly journals Role of heat shock transcription factor in yeast metallothionein gene expression.

1991 ◽  
Vol 11 (7) ◽  
pp. 3676-3681 ◽  
Author(s):  
W M Yang ◽  
W Gahl ◽  
D Hamer
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Heat Shock ◽  
Gene Transcription ◽  
Heat Shock Factor ◽  
Heat Shock Transcription Factor ◽  
Wild Type ◽  
Promoter Sequences ◽  
Metallothionein Gene ◽  
Upstream Promoter

The induction of Saccharomyces cerevisiae metallothionein gene transcription by Cu and Ag is mediated by the ACE1 transcription factor. In an effort to detect additional stimuli and factors that regulate metallothionein gene transcription, we isolated a Cu-resistant suppressor mutant of an ACE1 deletion strain. Even in the absence of metals, the suppressor mutant exhibited high basal levels of metallothionein gene transcription that required upstream promoter sequences. The suppressor gene was cloned, and its predicted product was shown to correspond to yeast heat shock transcription factor with a single-amino-acid substitution in the DNA-binding domain. The mutant heat shock factor bound strongly to metallothionein gene upstream promoter sequences, whereas wild-type heat shock factor interacted weakly with the same region. Heat treatment led to a slight but reproducible induction of metallothionein gene expression in both wild-type and suppressor strains, and Cd induced transcription in the mutant strain. These studies provide evidence for multiple pathways of metallothionein gene transcriptional regulation in S. cerevisiae.

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