Deficient induction of human hsp70 heat shock gene transcription in Y79 retinoblastoma cells despite activation of heat shock factor 1.

The existence of multiple heat shock factor (HSF) genes in higher eukaryotes has promoted questions regarding the functions of these HSF family members, especially with respect to the stress response. To address these questions, we have used polyclonal antisera raised against mouse HSF1 and HSF2 to examine the biochemical, physical, and functional properties of these two factors in unstressed and heat-shocked mouse and human cells. We have identified HSF1 as the mediator of stress-induced heat shock gene transcription. HSF1 displays stress-induced DNA-binding activity, oligomerization, and nuclear localization, while HSF2 does not. Also, HSF1 undergoes phosphorylation in cells exposed to heat or cadmium sulfate but not in cells treated with the amino acid analog L-azetidine-2-carboxylic acid, indicating that phosphorylation of HSF1 is not essential for its activation. Interestingly, HSF1 and HSF2 overexpressed in transfected 3T3 cells both display constitutive DNA-binding activity, oligomerization, and transcriptional activity. These results demonstrate that HSF1 can be activated in the absence of physiological stress and also provide support for a model of regulation of HSF1 and HSF2 activity by a titratable negative regulatory factor.

Download Full-text

Activation of heat shock gene transcription by heat shock factor 1 involves oligomerization, acquisition of DNA-binding activity, and nuclear localization and can occur in the absence of stress

Molecular and Cellular Biology ◽

10.1128/mcb.13.3.1392-1407.1993 ◽

1993 ◽

Vol 13 (3) ◽

pp. 1392-1407

Author(s):

K D Sarge ◽

S P Murphy ◽

R I Morimoto

Keyword(s):

Heat Shock ◽

Dna Binding ◽

Gene Transcription ◽

Nuclear Localization ◽

Heat Shock Factor ◽

Binding Activity ◽

Heat Shock Gene ◽

Dna Binding Activity ◽

Shock Gene ◽

In Cells

The existence of multiple heat shock factor (HSF) genes in higher eukaryotes has promoted questions regarding the functions of these HSF family members, especially with respect to the stress response. To address these questions, we have used polyclonal antisera raised against mouse HSF1 and HSF2 to examine the biochemical, physical, and functional properties of these two factors in unstressed and heat-shocked mouse and human cells. We have identified HSF1 as the mediator of stress-induced heat shock gene transcription. HSF1 displays stress-induced DNA-binding activity, oligomerization, and nuclear localization, while HSF2 does not. Also, HSF1 undergoes phosphorylation in cells exposed to heat or cadmium sulfate but not in cells treated with the amino acid analog L-azetidine-2-carboxylic acid, indicating that phosphorylation of HSF1 is not essential for its activation. Interestingly, HSF1 and HSF2 overexpressed in transfected 3T3 cells both display constitutive DNA-binding activity, oligomerization, and transcriptional activity. These results demonstrate that HSF1 can be activated in the absence of physiological stress and also provide support for a model of regulation of HSF1 and HSF2 activity by a titratable negative regulatory factor.

Download Full-text

Light regulation of the 22 kd heat shock gene transcription and its translation product accumulation in Chlamydomonas reinhardtii.

The EMBO Journal ◽

10.1002/j.1460-2075.1990.tb07450.x ◽

1990 ◽

Vol 9 (9) ◽

pp. 2657-2661 ◽

Cited By ~ 15

Author(s):

D. Ish-Shalom ◽

K. Kloppstech ◽

I. Ohad

Keyword(s):

Heat Shock ◽

Chlamydomonas Reinhardtii ◽

Gene Transcription ◽

Light Regulation ◽

Heat Shock Gene ◽

Translation Product ◽

Shock Gene ◽

Product Accumulation

Download Full-text

Heat Shock Factor 1 Attenuates 4-Hydroxynonenal-mediated Apoptosis

Journal of Biological Chemistry ◽

10.1074/jbc.m706799200 ◽

2007 ◽

Vol 282 (46) ◽

pp. 33412-33420 ◽

Cited By ~ 70

Author(s):

Aaron T. Jacobs ◽

Lawrence J. Marnett

Keyword(s):

Lipid Peroxidation ◽

Heat Shock ◽

Nuclear Translocation ◽

Ectopic Expression ◽

Antioxidant Response ◽

Heat Shock Factor ◽

Heat Shock Gene ◽

Heat Shock Factor 1 ◽

Inhibitory Interaction ◽

Heat Shock Responses

Lipid peroxidation is a consequence of both normal physiology and oxidative stress that generates various reactive metabolites, a principal end product being 4-hydroxynonenal (HNE). As a diffusible electrophile, HNE reacts extensively with cellular nucleophiles. Consequently, HNE alters cellular signaling and activates the intrinsic apoptotic cascade. We have previously demonstrated that in addition to promoting apoptosis, HNE activates stress response pathways, including the antioxidant, endoplasmic reticulum stress, DNA damage, and heat shock responses. Here we demonstrate that activation of the heat shock response by HNE is dependent on the expression and nuclear translocation of heat shock factor 1 (HSF1), which promotes the expression of heat shock protein 40 (Hsp40) and Hsp70-1. Ectopic expression and immunoprecipitation of c-Myc-tagged Hsp70-1 indicates that HNE disrupts the inhibitory interaction between Hsp70-1 and HSF1, leading to the activation heat shock gene expression. Using siRNA to silence HSF1 expression, we observe that HSF1 is necessary for the induction of Hsp40 and Hsp70-1 by HNE, and the lack of Hsp expression is correlated with an increase in apoptosis. Nrf2, the transcription factor that mediates the antioxidant response, was also silenced using siRNA. Silencing Nrf2 also enhanced the cytotoxicity of HNE, but not as effectively as HSF1. Silencing HSF1 expression facilitates the activation of JNK pro-apoptotic signaling and selectively decreases expression of the anti-apoptotic Bcl-2 family member Bcl-XL. Overexpression of Bcl-XL attenuates HNE-mediated apoptosis in HSF1-silenced cells. Overall, activation of HSF1 and stabilization of Bcl-XL mediate a protective response that may contribute significantly to the cellular biology of lipid peroxidation.

Download Full-text

Conditional silencing: the HMRE mating-type silencer exerts a rapidly reversible position effect on the yeast HSP82 heat shock gene

Molecular and Cellular Biology ◽

10.1128/mcb.13.2.727-738.1993 ◽

1993 ◽

Vol 13 (2) ◽

pp. 727-738

Author(s):

S Lee ◽

D S Gross

Keyword(s):

Heat Shock ◽

Mating Type ◽

Binding Sites ◽

Position Effect ◽

Heat Shock Factor ◽

Heat Shock Gene ◽

Autonomously Replicating Sequence ◽

Type Locus ◽

Factor Binding ◽

Shock Gene

The HMRE silencer of Saccharomyces cerevisiae has been previously shown to transcriptionally repress class II and class III genes integrated within the HMR silent mating-type locus up to 2.6 kb away. Here we study the ability of this element to repress at an ectopic position, independent of sequences normally associated with it. When integrated 750 bp upstream of the HSP82 heat shock gene, the silencer represses basal-level transcription approximately 5-fold but has no effect on chemical- or heat-shock-induced expression. Such conditional silencing is also seen when the HMRE/HSP82 allele is carried on a centromeric episome or when the entire HMRa domain is transplaced 2.7 kb upstream of HSP82. Notably, the a1 promoter within the immigrant HMRa locus remains fully repressed at the same time HSP82 is derepressed. The position effect mediated by the E silencer is absolutely dependent on the presence of a functional SIR4 gene product, is lost within 1 min following stress induction, and is fully reestablished within 15 min following a return to nonstressful conditions. Similar kinetics of reestablishment are seen in HMRE/HSP82 and HMRa/HSP82 strains, indicating that complete repression can be mediated over thousands of base pairs within minutes. DNase I chromatin mapping reveals that the ABF1, RAP1, and autonomously replicating sequence factor binding sites within the silencer are constitutively occupied in chromatin, unaltered by heat shock or the presence of SIR4. Similarly, the heat shock factor binding site upstream of HSP82 remains occupied under such conditions, suggesting concurrent occupancy of silencer and activator binding sites. Our results are consistent with a model in which silencing at the HMRE/HSP82 allele is mediated by direct or indirect contacts between the silencer protein complex and heat shock factor.

Download Full-text