1
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Carlson T, Christian N, Bonner JJ. A role for RNA metabolism in inducing the heat shock response. Gene Expr 2018; 7:283-91. [PMID: 10440229 PMCID: PMC6174669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
Yeast HSF is constitutively trimeric and DNA bound. Heat shock is thought to activate HSF by inducing a conformational change. We have developed an assay in which we can follow a conformational change of HSF that correlates with activity and thus appears to be the active conformation. This conformational change requires two HSF trimers bound cooperatively to DNA. The conformational change can be induced in whole cell extracts, and is thus amenable to biochemical analysis. We have purified a factor that triggers the conformational change. The factor is sensitive to dialysis, insensitive to NEM, and is not extractable by phenol. It is small, and apparently not a peptide. Mass spectroscopy identifies a novel guanine nucleotide that tracks with activity on columns. This novel nucleotide, purchased from Sigma, induces the conformational change (although this does not prove the identity of the activating factor unambiguously, because Sigma's preparation is contaminated with other compounds). What is the source of this nucleotide in cells? Activity can be generated by treating extracts with ribonuclease; this implicates RNA degradation as a source of HSF-activating activity. The heat shock response is primarily responsible for monitoring the levels of protein chaperones; how can RNA degradation be involved? Synthetic lethal interactions link HSF activity to ribosome biogenesis, suggesting a possible model. Ribosomal proteins are produced in large quantities, and in excess of rRNA; unassembled r-proteins are rapidly degraded (t1/2 approximately 3 min). Unassembled r-proteins aggregate readily. It is likely that unassembled r-proteins represent a major target of chaperones in vivo, and for proteasome-dependent degradation. Interference with rRNA processing (e.g., by heat shock) requires hsp70s to handle the aggregation-prone r-proteins, and proteasome proteins to help degrade the unassembled r-proteins before they aggregate. A nucleotide signal could be generated from the degradation products of the rRNA itself.
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Affiliation(s)
- Tage Carlson
- *Departments of Biology, Indiana University, Bloomington, IN 47405
| | - Noah Christian
- †Departments of Chemistry, Indiana University, Bloomington, IN 47405
| | - J. José Bonner
- *Departments of Biology, Indiana University, Bloomington, IN 47405
- Address correspondence to J. José Bonner, Department of Biology, Indiana University, 142 Jordan Hall, 1001 E. 3rd Street, Bloomington, IN 47405-3700. Tel: (812) 855-7074; Fax: (812) 855-6705; E-mail:
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2
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Dayalan Naidu S, Dinkova-Kostova AT. Regulation of the mammalian heat shock factor 1. FEBS J 2017; 284:1606-1627. [PMID: 28052564 DOI: 10.1111/febs.13999] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 11/17/2016] [Accepted: 01/03/2017] [Indexed: 12/21/2022]
Abstract
Living organisms are endowed with the capability to tackle various forms of cellular stress due to the presence of molecular chaperone machinery complexes that are ubiquitous throughout the cell. During conditions of proteotoxic stress, the transcription factor heat shock factor 1 (HSF1) mediates the elevation of heat shock proteins, which are crucial components of the chaperone complex machinery and function to ameliorate protein misfolding and aggregation and restore protein homeostasis. In addition, HSF1 orchestrates a versatile transcriptional programme that includes genes involved in repair and clearance of damaged macromolecules and maintenance of cell structure and metabolism, and provides protection against a broad range of cellular stress mediators, beyond heat shock. Here, we discuss the structure and function of the mammalian HSF1 and its regulation by post-translational modifications (phosphorylation, sumoylation and acetylation), proteasomal degradation, and small-molecule activators and inhibitors.
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Affiliation(s)
- Sharadha Dayalan Naidu
- Division of Cancer Research, School of Medicine, Jacqui Wood Cancer Centre, University of Dundee, UK
| | - Albena T Dinkova-Kostova
- Division of Cancer Research, School of Medicine, Jacqui Wood Cancer Centre, University of Dundee, UK
- Department of Pharmacology and Molecular Sciences, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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3
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Solís EJ, Pandey JP, Zheng X, Jin DX, Gupta PB, Airoldi EM, Pincus D, Denic V. Defining the Essential Function of Yeast Hsf1 Reveals a Compact Transcriptional Program for Maintaining Eukaryotic Proteostasis. Mol Cell 2016; 63:60-71. [PMID: 27320198 PMCID: PMC4938784 DOI: 10.1016/j.molcel.2016.05.014] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 03/22/2016] [Accepted: 05/11/2016] [Indexed: 11/18/2022]
Abstract
Despite its eponymous association with the heat shock response, yeast heat shock factor 1 (Hsf1) is essential even at low temperatures. Here we show that engineered nuclear export of Hsf1 results in cytotoxicity associated with massive protein aggregation. Genome-wide analysis revealed that Hsf1 nuclear export immediately decreased basal transcription and mRNA expression of 18 genes, which predominately encode chaperones. Strikingly, rescuing basal expression of Hsp70 and Hsp90 chaperones enabled robust cell growth in the complete absence of Hsf1. With the exception of chaperone gene induction, the vast majority of the heat shock response was Hsf1 independent. By comparative analysis of mammalian cell lines, we found that only heat shock-induced but not basal expression of chaperones is dependent on the mammalian Hsf1 homolog (HSF1). Our work reveals that yeast chaperone gene expression is an essential housekeeping mechanism and provides a roadmap for defining the function of HSF1 as a driver of oncogenesis.
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Affiliation(s)
- Eric J Solís
- Department of Molecular and Cellular Biology, Northwest Labs, Harvard University, Cambridge, MA 02138, USA; Systems Biology PhD Program, Harvard University, Cambridge, MA 02138, USA
| | - Jai P Pandey
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Xu Zheng
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Dexter X Jin
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Piyush B Gupta
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Koch Institute for Integrative Cancer Research at MIT, Cambridge, MA 02142, USA; Harvard Stem Cell Institute, Cambridge, MA 02138, USA
| | - Edoardo M Airoldi
- Department of Statistics, Harvard University, Cambridge, MA 02138, USA
| | - David Pincus
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA.
| | - Vladimir Denic
- Department of Molecular and Cellular Biology, Northwest Labs, Harvard University, Cambridge, MA 02138, USA.
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4
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Nussbaum I, Weindling E, Jubran R, Cohen A, Bar-Nun S. Deteriorated stress response in stationary-phase yeast: Sir2 and Yap1 are essential for Hsf1 activation by heat shock and oxidative stress, respectively. PLoS One 2014; 9:e111505. [PMID: 25356557 PMCID: PMC4214751 DOI: 10.1371/journal.pone.0111505] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Accepted: 10/02/2014] [Indexed: 11/19/2022] Open
Abstract
Stationary-phase cultures have been used as an important model of aging, a complex process involving multiple pathways and signaling networks. However, the molecular processes underlying stress response of non-dividing cells are poorly understood, although deteriorated stress response is one of the hallmarks of aging. The budding yeast Saccharomyces cerevisiae is a valuable model organism to study the genetics of aging, because yeast ages within days and are amenable to genetic manipulations. As a unicellular organism, yeast has evolved robust systems to respond to environmental challenges. This response is orchestrated largely by the conserved transcription factor Hsf1, which in S. cerevisiae regulates expression of multiple genes in response to diverse stresses. Here we demonstrate that Hsf1 response to heat shock and oxidative stress deteriorates during yeast transition from exponential growth to stationary-phase, whereas Hsf1 activation by glucose starvation is maintained. Overexpressing Hsf1 does not significantly improve heat shock response, indicating that Hsf1 dwindling is not the major cause for Hsf1 attenuated response in stationary-phase yeast. Rather, factors that participate in Hsf1 activation appear to be compromised. We uncover two factors, Yap1 and Sir2, which discretely function in Hsf1 activation by oxidative stress and heat shock. In Δyap1 mutant, Hsf1 does not respond to oxidative stress, while in Δsir2 mutant, Hsf1 does not respond to heat shock. Moreover, excess Sir2 mimics the heat shock response. This role of the NAD+-dependent Sir2 is supported by our finding that supplementing NAD+ precursors improves Hsf1 heat shock response in stationary-phase yeast, especially when combined with expression of excess Sir2. Finally, the combination of excess Hsf1, excess Sir2 and NAD+ precursors rejuvenates the heat shock response.
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Affiliation(s)
- Inbal Nussbaum
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Esther Weindling
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Ritta Jubran
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Aviv Cohen
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Shoshana Bar-Nun
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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5
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Biology of the heat shock response and protein chaperones: budding yeast (Saccharomyces cerevisiae) as a model system. Microbiol Mol Biol Rev 2012; 76:115-58. [PMID: 22688810 DOI: 10.1128/mmbr.05018-11] [Citation(s) in RCA: 362] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The eukaryotic heat shock response is an ancient and highly conserved transcriptional program that results in the immediate synthesis of a battery of cytoprotective genes in the presence of thermal and other environmental stresses. Many of these genes encode molecular chaperones, powerful protein remodelers with the capacity to shield, fold, or unfold substrates in a context-dependent manner. The budding yeast Saccharomyces cerevisiae continues to be an invaluable model for driving the discovery of regulatory features of this fundamental stress response. In addition, budding yeast has been an outstanding model system to elucidate the cell biology of protein chaperones and their organization into functional networks. In this review, we evaluate our understanding of the multifaceted response to heat shock. In addition, the chaperone complement of the cytosol is compared to those of mitochondria and the endoplasmic reticulum, organelles with their own unique protein homeostasis milieus. Finally, we examine recent advances in the understanding of the roles of protein chaperones and the heat shock response in pathogenic fungi, which is being accelerated by the wealth of information gained for budding yeast.
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6
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A stress response related to the carbon source and the absence of KlHAP2 in Kluyveromyces lactis. J Ind Microbiol Biotechnol 2010; 38:43-9. [DOI: 10.1007/s10295-010-0827-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 07/26/2010] [Indexed: 10/19/2022]
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7
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DNA-binding and transcriptional activities of human HSF4 containing mutations that associate with congenital and age-related cataracts. Biochim Biophys Acta Mol Basis Dis 2010; 1802:749-53. [PMID: 20670914 DOI: 10.1016/j.bbadis.2010.06.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 05/27/2010] [Accepted: 06/01/2010] [Indexed: 12/30/2022]
Abstract
Heat shock transcription factor HSF4 is necessary for ocular lens development and fiber cell differentiation. Mutations of the human HSF4 gene have been implicated in congenital and age-related cataracts. Here, we show that HSF4 activates transcription of genes encoding crystallins and beaded filament structural proteins in lens epithelial cells. Five missense mutations that have been associated with congenital cataract inhibited DNA-binding of HSF4, which demonstrates the relationship between HSF4 mutations, loss of lens protein gene expression, and cataractogenesis. However, two missense mutations that have been associated with age-related cataract did not or only slightly alter HSF4 activity, implying that other genetic and environmental factors affect the functions of these mutant proteins.
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8
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Westerheide SD, Anckar J, Stevens SM, Sistonen L, Morimoto RI. Stress-inducible regulation of heat shock factor 1 by the deacetylase SIRT1. Science 2009; 323:1063-6. [PMID: 19229036 DOI: 10.1126/science.1165946] [Citation(s) in RCA: 531] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Heat shock factor 1 (HSF1) is essential for protecting cells from protein-damaging stress associated with misfolded proteins and regulates the insulin-signaling pathway and aging. Here, we show that human HSF1 is inducibly acetylated at a critical residue that negatively regulates DNA binding activity. Activation of the deacetylase and longevity factor SIRT1 prolonged HSF1 binding to the heat shock promoter Hsp70 by maintaining HSF1 in a deacetylated, DNA-binding competent state. Conversely, down-regulation of SIRT1 accelerated the attenuation of the heat shock response (HSR) and release of HSF1 from its cognate promoter elements. These results provide a mechanistic basis for the requirement of HSF1 in the regulation of life span and establish a role for SIRT1 in protein homeostasis and the HSR.
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Affiliation(s)
- Sandy D Westerheide
- Department of Biochemistry, Molecular Biology and Cell Biology, Rice Institute for Biomedical Research, Northwestern University, Evanston, IL, 60208, USA
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9
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Yamamoto A, Sakurai H. The DNA-binding domain of yeast Hsf1 regulates both DNA-binding and transcriptional activities. Biochem Biophys Res Commun 2006; 346:1324-9. [PMID: 16806072 DOI: 10.1016/j.bbrc.2006.06.057] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Accepted: 06/12/2006] [Indexed: 11/26/2022]
Abstract
The heat shock transcription factor (HSF) is a key regulator of the heat shock response. In Saccharomyces cerevisiae, the transcription activating ability of Hsf1 is repressed by its DNA-binding domain, but the detailed mechanism by which the inhibitory function is relieved in response to stress remains unknown. In this study, we isolated and characterized three hsf1 mutants with temperature-sensitive mutations in the DNA-binding domain. Two mutations inhibited DNA-binding activity, leading to decreased expression of target genes. The third mutation caused transcriptional defects without affecting DNA binding, and its suppressor mutation was located in a region important for sensing heat shock. These results indicate that the DNA-binding domain regulates both the DNA-binding and transcriptional activities of Hsf1, and suggest that these functions are located within discrete regions of the DNA-binding domain.
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Affiliation(s)
- Ayako Yamamoto
- Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan
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10
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Hashikawa N, Mizukami Y, Imazu H, Sakurai H. Mutated Yeast Heat Shock Transcription Factor Activates Transcription Independently of Hyperphosphorylation. J Biol Chem 2006; 281:3936-42. [PMID: 16361698 DOI: 10.1074/jbc.m510827200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The homotrimeric heat shock transcription factor (HSF) binds to the heat shock element of target genes and regulates transcription in response to various stresses. The Hsf1 protein of Saccharomyces cerevisiae is extensively phosphorylated upon heat shock; a modification that is under positive regulation by its C-terminal regulatory domain (CTM). Hyperphosphorylation has been implicated in gene-specific transcriptional activation. Here, we surveyed genes whose heat shock response is reduced by a CTM mutation. The CTM is indispensable for transcription via heat shock elements bound by a single Hsf1 trimer but is dispensable for transcription via heat shock elements bound by Hsf1 trimers in a cooperative manner. Intragenic mutations located within or near the wing region of the winged helix-turn-helix DNA-binding domain suppress the temperature-sensitive growth phenotype associated with the CTM mutation and enable Hsf1 to activate transcription independently of hyperphosphorylation. Deletion of the wing partially restores the transcriptional defects of the unphosphorylated Hsf1. These results demonstrate a functional link between hyperphosphorylation and the wing region and suggest that this modification is involved in a conformational change of a single Hsf1 trimer to an active form.
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Affiliation(s)
- Naoya Hashikawa
- Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Ishikawa, Japan
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11
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Bu L, Jin Y, Shi Y, Chu R, Ban A, Eiberg H, Andres L, Jiang H, Zheng G, Qian M, Cui B, Xia Y, Liu J, Hu L, Zhao G, Hayden MR, Kong X. Mutant DNA-binding domain of HSF4 is associated with autosomal dominant lamellar and Marner cataract. Nat Genet 2002; 31:276-8. [PMID: 12089525 DOI: 10.1038/ng921] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Congenital cataracts cause 10-30% of all blindness in children, with one-third of cases estimated to have a genetic cause. Lamellar cataract is the most common type of infantile cataract. We carried out whole-genome linkage analysis of Chinese individuals with lamellar cataract, and found that the disorder is associated with inheritance of a 5.11-cM locus on chromosome 16. This locus coincides with one previously described for Marner cataract. We screened individuals of three Chinese families for mutations in HSF4 (a gene at this locus that encodes heat-shock transcription factor 4) and discovered that in each family, a distinct missense mutation, predicted to affect the DNA-binding domain of the protein, segregates with the disorder. We also discovered an association between a missense mutation and Marner cataract in an extensive Danish family. We suggest that HSF4 is critical to lens development.
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Affiliation(s)
- Lei Bu
- Shanghai Research Center of Biotechnology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200233, People's Republic of China
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12
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Littlefield O, Nelson HC. Crystal packing interaction that blocks crystallization of a site-specific DNA binding protein-DNA complex. Proteins 2001; 45:219-28. [PMID: 11599025 DOI: 10.1002/prot.1142] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We present here three high-resolution crystal structures of complexes between the DNA-binding domain of the heat-shock transcription factor (HSF) and DNA oligomers. Although the DNA oligomers contain HSF's specific binding sequence, called a heat-shock element, the crystal structures do not contain the specific protein-DNA complex. In one crystal structure, the 10 base pair DNA oligomer is statically disordered. In the other two related structures, the 12 base pair DNA oligomers are in unique positions, but the protein-DNA contacts in these two crystals are not sequence specific. In all three structures, the DNA appears to act as a rigid, polyanion scaffold to support columns of proteins in a crystalline lattice. A robust crystal packing interface between protein monomers obscures the true DNA-binding surface, known from previous genetic and biochemical studies. By redesigning the protein to interfere with the crystal lattice contacts, we were able to obtain physiologically relevant crystals in a specific protein-DNA complex. Thus, a crystal-packing interface was able to prevent the weak, but physiological relevant interactions between a protein and DNA.
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Affiliation(s)
- O Littlefield
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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13
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Zhang L, Eggers-Schumacher G, Schöffl F, Prändl R. Analysis of heat-shock transcription factor-DNA binding in Arabidopsis suspension cultures by UV laser crosslinking. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2001; 28:217-223. [PMID: 11722765 DOI: 10.1046/j.1365-313x.2001.01137.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Crosslinking techniques are important in examining protein-DNA interactions in living cells. Formaldehyde and UV light emitted by conventional lamps are the most commonly used crosslinking agents. The crosslinking step is followed by immunoprecipitation of specific protein-DNA adducts, and by analysis and quantification of the co-immunoprecipitated DNA. There are a few reported cases of fruitful in vivo protein-DNA crosslinking experiments, but not in plants. In this report, we analyse the binding of heat-shock transcription factor (HSF) to heat-shock promoters in intact Arabidopsis cells. Efficient protein-DNA crosslinking by irradiation of Arabidopsis suspension culture tissue was achieved using UV laser pulses. In addition, methods for immunoprecipitation and detection of the co-immunoprecipitated DNA are reported. Our results suggest that Arabidopsis HSFs immunoreactive for HSF1 antibodies bind constitutively to the HSP18.2 gene.
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Affiliation(s)
- L Zhang
- ZMBP-Allgemeine Genetik, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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14
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Bonner JJ, Chen D, Storey K, Tushan M, Lea K. Structural analysis of yeast HSF by site-specific crosslinking. J Mol Biol 2000; 302:581-92. [PMID: 10986120 DOI: 10.1006/jmbi.2000.4096] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We have introduced cysteine substitutions into the yeast HSF1 gene at a variety of locations. Most have no phenotypic effect, and therefore provide site-specific probes for thiol-specific reagents. Crosslinking of single mutants identifies locations where equivalent regions of individual monomers can approach each other in the HSF trimer. Crosslinking of double mutants indicates regions that can approach closely within a single subunit. Results for the DNA binding domain and trimerization domain are consistent with known structural information, and provide essential controls on the validity of the technique. In contrast to these two domains, the N-terminal and C-terminal domains, wherein lie the transcriptional activators, are highly flexible, and do not appear to be in stable contact with any other portions of the protein. None of these patterns are affected by the conformational change that is induced by superoxide or heat shock. We suggest a new model for the mechanism of HSF regulation that accomodates the structural information provided by these studies.
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Affiliation(s)
- J J Bonner
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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15
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Bonner JJ, Carlson T, Fackenthal DL, Paddock D, Storey K, Lea K. Complex regulation of the yeast heat shock transcription factor. Mol Biol Cell 2000; 11:1739-51. [PMID: 10793148 PMCID: PMC14880 DOI: 10.1091/mbc.11.5.1739] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The yeast heat shock transcription factor (HSF) is regulated by posttranslational modification. Heat and superoxide can induce the conformational change associated with the heat shock response. Interaction between HSF and the chaperone hsp70 is also thought to play a role in HSF regulation. Here, we show that the Ssb1/2p member of the hsp70 family can form a stable, ATP-sensitive complex with HSF-a surprising finding because Ssb1/2p is not induced by heat shock. Phosphorylation and the assembly of HSF into larger, ATP-sensitive complexes both occur when HSF activity decreases, whether during adaptation to a raised temperature or during growth at low glucose concentrations. These larger HSF complexes also form during recovery from heat shock. However, if HSF is assembled into ATP-sensitive complexes (during growth at a low glucose concentration), heat shock does not stimulate the dissociation of the complexes. Nor does induction of the conformational change induce their dissociation. Modulation of the in vivo concentrations of the SSA and SSB proteins by deletion or overexpression affects HSF activity in a manner that is consistent with these findings and suggests the model that the SSA and SSB proteins perform distinct roles in the regulation of HSF activity.
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Affiliation(s)
- J J Bonner
- Department of Biology, Indiana University, Bloomington, Indiana 47405-3700, USA.
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16
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Lee S, Carlson T, Christian N, Lea K, Kedzie J, Reilly JP, Bonner JJ. The yeast heat shock transcription factor changes conformation in response to superoxide and temperature. Mol Biol Cell 2000; 11:1753-64. [PMID: 10793149 PMCID: PMC14881 DOI: 10.1091/mbc.11.5.1753] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In vitro DNA-binding assays demonstrate that the heat shock transcription factor (HSF) from the yeast Saccharomyces cerevisiae can adopt an altered conformation when stressed. This conformation, reflected in a change in electrophoretic mobility, requires that two HSF trimers be bound to DNA. Single trimers do not show this change, which appears to represent an alteration in the cooperative interactions between trimers. HSF isolated from stressed cells displays a higher propensity to adopt this altered conformation. Purified HSF can be stimulated in vitro to undergo the conformational change by elevating the temperature or by exposing HSF to superoxide anion. Mutational analysis maps a region critical for this conformational change to the flexible loop between the minimal DNA-binding domain and the flexible linker that joins the DNA-binding domain to the trimerization domain. The significance of these findings is discussed in the context of the induction of the heat shock response by ischemic stroke, hypoxia, and recovery from anoxia, all known to stimulate the production of superoxide.
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Affiliation(s)
- S Lee
- Departments of Biology and Chemistry, Indiana University, Bloomington, Indiana 47405-3700, USA
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17
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Abstract
The structure of a complex between the HIV Revresponsive element (RRE) RNA and a fragment of the Rev protein has recently been determined by NMR. Together with previous studies of the Tat-TAR complex, these results show how RNA elements with considerable tertiary structure are able to play a more active role in directing binding to elements of protein secondary structure.
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Affiliation(s)
- D Grate
- Department of Biology, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA.
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