Developmentally regulated nuclear transport of transcription factors in Drosophila embryos enable the heat shock response

Development ◽  
1998 ◽  
Vol 125 (23) ◽  
pp. 4841-4850 ◽  
Author(s):  
Z. Wang ◽  
S. Lindquist
Keyword(s):  
Transcription Factors ◽  
Heat Shock ◽  
Heat Shock Response ◽  
Nuclear Transport ◽  
Binding Activity ◽  
Spatiotemporal Pattern ◽  
Dna Binding Activity ◽  
Early Embryos ◽  
Shock Response ◽  
Drosophila Embryos

Hsp70 is a broadly conserved thermotolerance factor, but inhibits growth at normal temperatures and cannot be induced in early embryos. We report that in Drosophila embryos the temporal and spatial patterns of Hsp70 inducibility were unexpectedly complex, with striking differences between the soma and the germline. In both, regulation occurred at the level of transcription. During the refractory period for Hsp70 induction, HSF (heat-shock transcription factor) exhibited specific DNA-binding activity characteristic of activation in extracts of heated embryos. Remarkably, however, HSF was restricted to the cytoplasm in intact embryos even after heat shock. HSF moved from the cytoplasm to the nucleus in the absence of heat precisely when the capacity to induce Hsp70 was acquired (cycle 12 of the germline, cycle 13 in the soma). During oogenesis, Hsp70 inducibility was lost in nurse cells around stage 10, in a posterior-to-anterior gradient and HSF redistributed from nucleus to cytoplasm in the same spatiotemporal pattern. In a highly inbred derivative of the Samarkind strain, HSF moved into embryonic nuclei earlier than in our standard wild-type strain. Correspondingly, Hsp70 was inducible earlier, confirming that nuclear transport of HSF controls the inducibility of Hsp70 in early embryos. We also report for the first time the nuclear import patterns of two general transcription factors, RNA polymerase subunit Ilc and TATA binding protein (TBP). Both enter nuclei in a highly synchronous manner, independently of each other and of HSF. The import of TBP coincides with the first reported appearance of transcripts in the embryo. We suggest that the potentiation of general and heat shock-specific transcription in Drosophila embryos is controlled by the developmentally programmed relocalization of general and heat shock-specific transcription factors. Restricted nuclear entry of HSF represents a newly described mechanism for regulating the heat-shock response.

Heat shock protects L6 myotubes from catabolic effects of dexamethasone and prevents downregulation of NF-κB

2001 ◽  
Vol 281 (4) ◽  
pp. R1193-R1200 ◽  
Author(s):  
Guangju Luo ◽  
Xiaoyan Sun ◽  
Eric Hungness ◽  
Per-Olof Hasselgren
Keyword(s):  
Heat Shock ◽  
Protein Degradation ◽  
Heat Shock Response ◽  
Muscle Cells ◽  
Binding Activity ◽  
Mrna Levels ◽  
Dna Binding Activity ◽  
Heat Shock Stress ◽  
L6 Myotubes ◽  
Shock Response

Glucocorticoids are the most important mediator of muscle cachexia in various catabolic conditions. Recent studies suggest that the transcription factor NF-κB acts as a suppressor of genes in the ubiquitin-proteasome proteolytic pathway and that glucocorticoids increase muscle proteolysis by downregulating NF-κB activity. The heat shock (stress) response, characterized by the induction of heat shock proteins, confers a protective effect against a variety of harmful stimuli. In the present study, we tested the hypothesis that the heat shock response protects muscle cells from the catabolic effects of dexamethasone and prevents downregulation of NF-κB. Cultured L6 myotubes were subjected to heat shock (43°C for 1 h) followed by recovery at 37°C for 1 h. Thereafter, cells were treated for 6 h with 1 μM dexamethasone, during which period protein degradation was measured as release of TCA-soluble radioactivity from proteins that had been prelabeled with [3H]tyrosine. Heat shock resulted in increased protein and mRNA levels for heat shock protein 70. The increase in protein degradation induced by dexamethasone was prevented in cells expressing the heat shock response. In the same cells, dexamethasone-induced downregulation of NF-κB DNA binding activity was blocked. The present results suggest that the heat shock response may protect muscle cells from the catabolic effects of dexamethasone and that this effect of heat shock may be related to inhibited downregulation of NF-κB activity.

scholarly journals Feeling the Heat: The Campylobacter jejuni HrcA Transcriptional Repressor Is an Intrinsic Protein Thermosensor

Biomolecules ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1413
Author(s):  
Giovanni Versace ◽  
Marta Palombo ◽  
Anna Menon ◽  
Vincenzo Scarlato ◽  
Davide Roncarati
Keyword(s):  
Heat Stress ◽  
Heat Shock ◽  
Dna Binding ◽  
Campylobacter Jejuni ◽  
Heat Shock Response ◽  
Binding Activity ◽  
Protective Mechanism ◽  
Intrinsic Protein ◽  
Dna Binding Activity ◽  
Shock Response

The heat-shock response, a universal protective mechanism consisting of a transcriptional reprogramming of the cellular transcriptome, results in the accumulation of proteins which counteract the deleterious effects of heat-stress on cellular polypeptides. To quickly respond to thermal stress and trigger the heat-shock response, bacteria rely on different mechanisms to detect temperature variations, which can involve nearly all classes of biological molecules. In Campylobacter jejuni the response to heat-shock is transcriptionally controlled by a regulatory circuit involving two repressors, HspR and HrcA. In the present work we show that the heat-shock repressor HrcA acts as an intrinsic protein thermometer. We report that a temperature upshift up to 42°C negatively affects HrcA DNA-binding activity to a target promoter, a condition required for de-repression of regulated genes. Furthermore, we show that this impairment of HrcA binding at 42°C is irreversible in vitro, as DNA-binding was still not restored by reversing the incubation temperature to 37°C. On the other hand, we demonstrate that the DNA-binding activity of HspR, which controls, in combination with HrcA, the transcription of chaperones’ genes, is unaffected by heat-stress up to 45°C, portraying this master repressor as a rather stable protein. Additionally, we show that HrcA binding activity is enhanced by the chaperonin GroE, upon direct protein–protein interaction. In conclusion, the results presented in this work establish HrcA as a novel example of intrinsic heat-sensing transcriptional regulator, whose DNA-binding activity is positively modulated by the GroE chaperonin.

The effect of the heat shock response on ultrastructure of the centrosome of Drosophila cultured cells in interphase: possible relation with changes in the chemical state of calcium.

1993 ◽  
Vol 71 (11-12) ◽  
pp. 507-517 ◽  
Author(s):  
Christiane Marcaillou ◽  
Alain Debec ◽  
Sylvie Lauverjat ◽  
Armelle Saihi
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Cultured Cells ◽  
Chemical State ◽  
Ultrastructural Organization ◽  
Heat Shock Stress ◽  
Shock Response ◽  
Pericentriolar Material ◽  
Functional Inactivation ◽  
Drosophila Embryos

Previous observations have shown that the heat shock response affects the centrosome function. We compared the ultrastructural organization of the centrosome in control (23 °C) and heat-shocked (37 °C, 50 min) interphase Drosophila cells to detect the nature of the lesions that could alter this organelle. The centrosome apparatus showed only minor modifications after the stress and the architecture of the centrioles appeared unaffected. The main difference concerned the organization of pericentriolar material which appeared more condensed and clotted. In extreme cases this material seemed to collapse on the centrioles. Recent reports proposed that Ca2+ concentrations could modify the distribution of pericentriolar material. In this study, we measured the changes in total and bound calcium in control or heat-shocked cell samples. The hyperthermia stress induced an increase of about 80% in global calcium. However, there was a decrease of about 50% in bound calcium. A heat shock stress seemed therefore to promote a change from the bound to the free state for a noticeable proportion of the element. As a preliminary hypothesis, these changes in the chemical state of calcium could be related to alterations in the pericentriolar material and thus with the functional inactivation of the centrosome. This view is also supported by calcium analysis on early Drosophila embryos. Contrary to cultured cells, Drosophila embryos did not present a stress inactivation of centrosomes. Equally, a heat shock did not disturb the bound calcium level in embryos.Key words: Centrosome, ultrastructure, calcium, heat shock, Drosophila.

scholarly journals Cytoplasmic protein misfolding titrates Hsp70 to activate nuclear Hsf1

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Anna E Masser ◽  
Wenjing Kang ◽  
Joydeep Roy ◽  
Jayasankar Mohanakrishnan Kaimal ◽  
Jany Quintana-Cordero ◽  
...  
Keyword(s):  
Heat Shock ◽  
Dna Binding ◽  
Protein Misfolding ◽  
Regulatory System ◽  
Binding Activity ◽  
Cytoplasmic Protein ◽  
Dna Binding Activity ◽  
Shock Response ◽  
Transcriptional Output ◽  
Substrate Binding Domain

Hsf1 is an ancient transcription factor that responds to protein folding stress by inducing the heat-shock response (HSR) that restore perturbed proteostasis. Hsp70 chaperones negatively regulate the activity of Hsf1 via stress-responsive mechanisms that are poorly understood. Here, we have reconstituted budding yeast Hsf1-Hsp70 activation complexes and find that surplus Hsp70 inhibits Hsf1 DNA-binding activity. Hsp70 binds Hsf1 via its canonical substrate binding domain and Hsp70 regulates Hsf1 DNA-binding activity. During heat shock, Hsp70 is out-titrated by misfolded proteins derived from ongoing translation in the cytosol. Pushing the boundaries of the regulatory system unveils a genetic hyperstress program that is triggered by proteostasis collapse and involves an enlarged Hsf1 regulon. The findings demonstrate how an apparently simple chaperone-titration mechanism produces diversified transcriptional output in response to distinct stress loads.

scholarly journals Developmental regulation of the heat shock response by nuclear transport factor karyopherin-α3

Development ◽  
2001 ◽  
Vol 128 (17) ◽  
pp. 3349-3358 ◽  
Author(s):  
Xiang-dong Fang ◽  
Tianxin Chen ◽  
Kim Tran ◽  
Carl S. Parker
Keyword(s):  
Heat Shock ◽  
Nuclear Localization ◽  
Heat Shock Response ◽  
Nuclear Transport ◽  
Early Embryo ◽  
Nuclear Localization Sequence ◽  
Nuclear Targeting ◽  
Transport Factor ◽  
Shock Response ◽  
Hsp70 Induction

During early stages of Drosophila development the heat-shock response cannot be induced. It is reasoned that the adverse effects on cell cycle and cell growth brought about by Hsp70 induction must outweigh the beneficial aspects of Hsp70 induction in the early embryo. Although the Drosophila heat shock transcription factor (dHSF) is abundant in the early embryo it does not enter the nucleus in response to heat shock. In older embryos and in cultured cells the factor is localized within the nucleus in an apparent trimeric structure that binds DNA with high affinity. The domain responsible for nuclear localization upon stress resides between residues 390 and 420 of the dHSF. Using that domain as bait in a yeast two-hybrid system we now report the identification and cloning of a Drosophila nuclear transport protein karyopherin-α3 (dKap-α3). Biochemical methods demonstrate that the dKap-α3 protein binds specifically to the dHSF’s nuclear localization sequence (NLS). Furthermore, the dKap-α3 protein does not associate with NLSs that contain point mutations, which are not transported in vivo. Nuclear docking studies also demonstrate specific nuclear targeting of the NLS substrate by dKap-α3. Consistant with previous studies demonstrating that early Drosophila embryos are refractory to heat shock as a result of dHSF nuclear exclusion, we demonstrate that the early embryo is deficient in dKap-α3 protein through cycle 12. From cycle 13 onward the transport factor is present and the dHSF is localized within the nucleus thus allowing the embryo to respond to heat shock.

scholarly journals Dual regulation of heat-shock transcription factor (HSF) activation and DNA-binding activity by H2O2: role of thioredoxin

1996 ◽  
Vol 318 (1) ◽  
pp. 187-193 ◽  
Author(s):  
Muriel R. JACQUIER-SARLIN ◽  
Barbara S POLLA
Keyword(s):  
Transcription Factors ◽  
Heat Shock ◽  
Dna Binding ◽  
Cellular Response ◽  
Nuclear Translocation ◽  
Alkylating Agents ◽  
Iodoacetic Acid ◽  
Binding Activity ◽  
Dna Binding Activity

The heat-shock (HS) response is a ubiquitous cellular response to stress, involving the transcriptional activation of HS genes. Reactive oxygen species (ROS) have been shown to regulate the activity of a number of transcription factors. We investigated the redox regulation of the stress response and report here that in the human pre-monocytic line U937 cells, H2O2 induced a concentration-dependent transactivation and DNA-binding activity of heat-shock factor-1 (HSF-1). DNA-binding activity was, however, lower with H2O2 than with HS. We thus hypothesized a dual regulation of HSF by oxidants. We found that oxidizing agents, such as H2O2 and diamide, as well as alkylating agents, such as iodoacetic acid, abolished, in vitro, the HSF-DNA-binding activity induced by HS in vivo. The effects of H2O2in vitro were reversed by the sulphydryl reducing agent dithiothreitol and the endogenous reductor thioredoxin (TRX), while the effects of iodoacetic acid were irreversible. In addition, TRX also restored the DNA-binding activity of HSF oxidized in vivo, while it was found to be itself induced in vivo by both HS and H2O2. Thus, H2O2 exerts dual effects on the activation and the DNA-binding activity of HSF: on the one hand, H2O2 favours the nuclear translocation of HSF, while on the other, it alters HSF-DNA-binding activity, most likely by oxidizing critical cysteine residues within the DNA-binding domain. HSF thus belongs to the group of ROS-modulated transcription factors. We propose that the time required for TRX induction, which may restore the DNA-binding activity of oxidized HSF, provides an explanation for the delay in heat-shock protein synthesis upon exposure of cells to ROS.

DNA binding of heat shock factor to the heat shock element is insufficient for transcriptional activation in murine erythroleukemia cells

1990 ◽  
Vol 10 (4) ◽  
pp. 1600-1608
Author(s):  
J O Hensold ◽  
C R Hunt ◽  
S K Calderwood ◽  
D E Housman ◽  
R E Kingston
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Transcriptional Activation ◽  
Heat Shock Factor ◽  
Apparent Size ◽  
Binding Activity ◽  
Heat Shock Element ◽  
Shock Response ◽  
Murine Erythroleukemia ◽  
Regulated Gene Expression

The heat shock response is among the most highly conserved examples of regulated gene expression, being present in all cellular organisms. Transcriptional activation of heat shock genes by increased temperature or other cellular stresses is mediated by the binding of a heat shock factor (HSF) to a conserved nucleotide sequence (the heat shock element) present in the promoter of heat-inducible genes. Despite the high degree of conservation of this response, embryonic stages of development are characterized by the absence of a heat shock response. Murine erythroleukemia (MEL) cells also lack this response, and we report here a detailed characterization of this defect for one of the most highly conserved of these genes, hsp70. Surprisingly, heat-induced transcriptional activation of this gene does not occur, despite the induction of a protein with the binding specificity of murine HSF. However, the MEL HSF differs slightly in apparent size from the HSF in 3T3 cells, which exhibit a normal heat shock response. These data suggest that activation of mammalian HSF by heat requires at least two separate steps: an alteration of binding activity followed by further modification that activates transcription. MEL cells do not respond to heat shock because they lack the ability to perform this secondary modification. These cells provide a useful system for characterizing heat shock activation in mammals.

scholarly journals DNA binding of heat shock factor to the heat shock element is insufficient for transcriptional activation in murine erythroleukemia cells.

1990 ◽  
Vol 10 (4) ◽  
pp. 1600-1608 ◽  
Author(s):  
J O Hensold ◽  
C R Hunt ◽  
S K Calderwood ◽  
D E Housman ◽  
R E Kingston
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Transcriptional Activation ◽  
Heat Shock Factor ◽  
Apparent Size ◽  
Binding Activity ◽  
Heat Shock Element ◽  
Shock Response ◽  
Murine Erythroleukemia ◽  
Regulated Gene Expression

The heat shock response is among the most highly conserved examples of regulated gene expression, being present in all cellular organisms. Transcriptional activation of heat shock genes by increased temperature or other cellular stresses is mediated by the binding of a heat shock factor (HSF) to a conserved nucleotide sequence (the heat shock element) present in the promoter of heat-inducible genes. Despite the high degree of conservation of this response, embryonic stages of development are characterized by the absence of a heat shock response. Murine erythroleukemia (MEL) cells also lack this response, and we report here a detailed characterization of this defect for one of the most highly conserved of these genes, hsp70. Surprisingly, heat-induced transcriptional activation of this gene does not occur, despite the induction of a protein with the binding specificity of murine HSF. However, the MEL HSF differs slightly in apparent size from the HSF in 3T3 cells, which exhibit a normal heat shock response. These data suggest that activation of mammalian HSF by heat requires at least two separate steps: an alteration of binding activity followed by further modification that activates transcription. MEL cells do not respond to heat shock because they lack the ability to perform this secondary modification. These cells provide a useful system for characterizing heat shock activation in mammals.

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