Heat Shock Factor Binding Protein 1 Research Articles

Structural and functional characterization of Hdh-HSBP1 and its involvement in heat stress and early development in Pacific abalone, Haliotis discus hannai

Heat shock factor binding protein 1 (HSBP1) is known to regulate the activity of heat shock factor 1 (HSF1) and the early development of organisms. To understand the involvement of HSBP1 in the heat shock response and embryonic and larval development of Pacific abalone (Haliotis discus hannai), the Hdh-HSBP1 gene was sequenced from the digestive gland (DG) tissue. The full-length sequence of Hdh-HSBP1 encompassed 738 nucleotides, encoding an 8.42 kDa protein consisting of 75 deduced amino acids. The protein contains an HSBP1 domain and a coiled-coil domain, which are conserved features in the HSBP1 protein family. Protein-protein molecular docking revealed that the coiled-coil region of Hdh-HSBP1 binds to the coiled-coil region of Hdh-HSF1. Tissue expression analysis demonstrated that the highest Hdh-HSBP1 expression occurred in the DG, whereas seasonal expression analysis revealed that this gene was most highly expressed in summer. In heat-stressed abalone, the highest expression of Hdh-HSBP1 occurred at 30 °C. Moreover, time-series analysis revealed that the expression of this gene began to increase significantly at 6 h post-heat stress, with higher expression observed at 12 h and 24 h post-heat stress. Furthermore, Hdh-HSBP1 mRNA expression showed a link to ROS production. Additionally, the expression of Hdh-HSBP1 showed significantly higher expression in the early stages of embryonic development in Pacific abalone. These results suggest that Hdh-HSBP1 plays a crucial role in the stress physiology of Pacific abalone by interacting with Hdh-HSF1, as well as its embryonic development.

Phenotypic and genotypic traits governing adaptive capacity of indigenous Salem Black goats subjected to protein energy alterations in the diet

A study was conducted to assess the different proportions of protein energy ratio on the adaptive capabilities of Salem Black goats based on changes in both phenotypic and selective genotypic traits. Forty adult Salem Black does (average body weight (BW) 16.0 kg) were divided into five groups, GI (n = 8; ICAR recommended; crude protein (CP) 80 g and total digestible nutrients (TDN) 358 g); GII (n = 8; 50 % Low Protein and Normal Energy; CP 40 g and TDN- 358 g); GIII (n = 8; Normal Protein and 50 % Low Energy; CP 80 g and TDN 179 g), GIV (n = 8; 50 % Low Protein and 50 % Low Energy; CP 40 g and TDN 179 g) and GV (n = 8; 70 % Low Protein and 70 % Low Energy; CP 24 g and TDN 107 g). The results indicated that the alteration in protein energy composition of the diet did not influence any of the physiological and endocrine variables. However, the alteration in the feed composition changed the molecular adaptation process by inducing changes (P < 0.05) in the expression pattern of selective (heat shock protein) HSPs genes. Further, it was observed that the gene expression patterns were sensitive to energy component of the diet rather than protein content. This was evident from the fact that when energy content was not compromised the Salem black goat was able to mount appropriate stress response. Thus, the study signified the importance of ensuring optimum nutrient requirement to cope with the existing environmental condition. In addition, the study also identified heat shock factor 1 (HSF1), heat shock factor binding protein 1 (HSBP1), HSP27, HSP60, HSP70, HSP90 and HSP110 could serve as reliable biomarkers for nutritional stress in Salem Black goat.

Dietary supplementation of thiamine down-regulates the expression of mitophagy and endoplasmic reticulum stress-related genes in the rumen epithelium of goats during high-concentrate diet feeding

Several studies have demonstrated that high-concentrate (HC) diet with thiamine supplementation can alleviate rumen epithelium inflammation and protecting the barrier function in goats. This study aimed to investigate the effects of dietary supply of thiamine on mitophagy and endoplasmic reticulum stress (ERS) during high-concentrate diet feeding. Twenty-four Boer goats (35.62 ± 2.4 kg) were used in this study, goats were subsequently assigned to 3 treatment groups (8 goats in each group) as follows: a low-concentrate diet (CON; concentrate: forage 30:70), a high-concentrate diet (HC; concentrate: forage 70:30) and high-concentrate diet with 200 mg thiamine/kg DMI (HCT; concentrate: forage 70:30) for 12 weeks. Compared with the HC group, the goats of HCT group had a markedly higher final weight, net weight gain, and average daily gain (ADG). The blood physiological and biochemical results showed that the HCT group expressed a lower the content of lymphocytes and leukocytes but a higher total protein and monocytes compared with that of HC group. The rumen epithelial mitochondrial membrane potential change (ΔΨm), relative mitochondrial DNA (mtDNA) content, adenosine triphosphate (ATP) level, together with the activities of the respiratory complexes I, III, and IV were markedly higher in the HCT group relative to HC ones. Relative to the HC group, the unc-51 like autophagy activating kinase 1 (ULK1), microtubule-associated protein 1 light chain 3 (LC3), autophagy-related 5 (ATG5), autophagy related 7 (ATG7), Beclin1, PTEN induced putative kinase 1 (PINK1), PERK (PKR-Endoplasmic Reticulum Kinase), activating transcription factor 4 (ATF4), activating transcription factor 6 (ATF6), X-box binding protein 1 (XBP1), heat shock 70 kDa protein 5 (HSPA5), DNA damage-inducible transcript 3 (DDIT3) and DNA damage-inducible transcript 4 (DDIT4) mRNA levels were decreased, but the breast cancer 1 (BRCA1), ataxia telangiectasia mutated (ATM), heat shock factor binding protein 1 (HSBP1) were increased in rumen epithelium of the HCT group. The results of transmission electron micrographs showed that the cell structure of the HCT group was higher integrity than that in the HC group, and the damage degree of mitochondria as well as endoplasmic reticulum being lower than the HC group. These results demonstrated that dietary thiamine could enhance rumen epithelial integrity by suppressing the responses of ERS and mitophagy during long-term HC diet feeding. HIGHLIGHTS This study is the first to demonstrate that the reduction of inflammatory response is related to the down-regulation of autophagy and endoplasmic reticulum stress in goats. Thiamine has good anti-inflammatory and anti-oxidation properties, which can be applied in intensive industry to reduce the negative effects caused by long-term high-concentrate diet.

Lin28A Regulates Stem-like Properties of Ovarian Cancer Cells by Enriching RAN and HSBP1 mRNA and Up-regulating its Protein Expression.

Ovarian cancer (OC) is one of the malignant tumors that seriously threaten women's health, with the highest mortality rate in gynecological malignancies. The prognosis of patients with advanced OC is still poor, and the 5-year survival rate is only 20-30%. Therefore, how to improve the early diagnosis rate and therapeutic effect are urgent for patients with OC. In this research, we found that Lin28A can promote the expression of stem cell marker molecules CD133, CD44, OCT4 and Nanog. We later confirmed that Lin28A can enrich the mRNA of ras-related nuclear protein (RAN) and heat shock factor binding protein 1 (HSBP1) through RIP assay, and that Lin28A can regulate their protein expression. We also identified that RAN and HSBP1 are highly expressed in OC tissues, and that they are significantly positively correlated with the expression of Lin28A and negatively correlated with the survival prognosis of OC patients. After stable knockdown of RAN or HSBP1 in OC cells with high expression of Lin28A, the expression of the stem cell marker molecules such as OCT4, CD44 and Nanog are reduced. And after knocking down of RAN or HSBP1 in Lin28A highly expressed OC cells, the survival and invasion of OC cells and tumor size of OC xenograft in nude mice were markedly inhibited and apoptosis was increased. Our data also showed that knock down of RAN or HSBP1 can inhibit the invasion ability of OC cells by decreasing the expression of N-cadherin, Vimentin and promoting the expression of E-cadherin. Meanwhile, knockdown of RAN or HSBP1 induced cell apoptosis by inhibiting the expression of PARP. Our results indicated that Lin28A could regulate the biological behaviors in OC cells through RAN/HSBP1. These findings suggest that Lin28A/RAN/HSBP1 can be used as a marker for diagnosis and prognosis of OC patients, and RAN/HSBP1 may be a potential new target for gene therapy of OC.

Novel SNP identified in HSBP1 gene and its association with thermal tolerance traits in Murrah buffalo

Heat shock response (HSR) is a universal mechanism in all organisms upon heat shock (HS) to prevent stress damages. It is under tight regulation by heat shock factors (HSFs) and heat shock proteins (HSPs). On the attenuation of HSR, Heat Shock Factor Binding Protein1 (HSBP1) interacts with HSF1 and thus converting the active trimer form of HSF1 to inert monomer state. Thus, play an important role in regulating heat shock genes. The present study aimed to explore single nucleotide polymorphism (SNP) in HSBP1 and their association with the thermo tolerance traits (respiration rate, rectal temperature and heat tolerance coefficient) for identification of most thermal adapted Murrah buffaloes. Two hundred female Murrah buffaloes were genotyped using custom sequencing to identify SNP. Only one novel SNPs in exon 3 at position g.1892C&gt;T and two nucleotide variation g.1327C&gt;G and g.1202C&gt;T were identified through direct DNA sequence scanning. Homozygous wild type genotypes (CC) were found in higher frequency (0.84, n=168) than homozygous recessive (0.10, n=20) and heterozygous (0.06, n=12) mutant genotypes at SNP locus g.1892C&gt;T. The association among the different genotype of this SNP locus with thermo tolerance was analyzed using Generalized Linear Model procedure in Statistical Analysis System. However, no significant difference was detected among the genotypes in terms of thermo tolerance traits in the study.

Molecular cloning of hsf1 and hsbp1 cDNAs, and the expression of hsf1, hsbp1 and hsp70 under heat stress in the sea cucumber Apostichopus japonicus.

The heat shock response (HSR) is known for the elevated synthesis of heat shock proteins (HSPs) under heat stress, which is mediated primarily by heat shock factor 1 (HSF1). Heat shock factor binding protein 1 (HSBP1) and feedback control of heat shock protein 70 (HSP70) are major regulators of the activity of HSF1. We obtained full-length cDNA of genes hsf1 and hsbp1 in the sea cucumber Apostichopus japonicus, which are the second available for echinoderm (after Strongylocentrotus purpuratus), and the first available for holothurian. The full-length cDNA of hsf1 was 2208bp, containing a 1326bp open reading frame encoding 441 amino acids. The full-length cDNA of hsbp1 was 2850bp, containing a 225bp open reading frame encoding 74 amino acids. The similarities of A. japonicus HSF1 with other species are low, and much higher similarity identities of A. japonicus HSBP1 were shared. Phylogenetic trees showed that A. japonicus HSF1 and HSBP1 were clustered with sequences from S. purpuratus, and fell into distinct clades with sequences from mollusca, arthropoda and vertebrata. Analysis by real-time PCR showed hsf1 and hsbp1 mRNA was expressed constitutively in all tissues examined. The expression of hsf1, hsbp1 and hsp70 in the intestine at 26°C was time-dependent. The results of this study might provide new insights into the regulation of heat shock response in this species.

Overexpression of HSBP1 is associated with resistance to radiotherapy in oral squamous epithelial carcinoma.

Heat shock factor binding protein 1 (HSBP1) has been recognized to regulate early embryonic development. However, HSBP1 expression and function in oral squamous carcinoma (OSCC) have not been studied. We found that HSBP1 expression was elevated in OSCC tissues compared to adjacent normal tissue. Although increased HSBP1 expression was not associated with clinical stage of the disease, it significantly related to outcome after radiotherapy (P < 0.01). Overexpression of HSBP1 enhanced sensitivity of OSCC cells in radiation. Moreover, HSBP1 elevated expression of stem cell markers such as CD44, CD133, ALDH and SOX2, and subsequently enhanced mammosphere formation ability, indicating it drives stem cell-like status in OSCC cells. Furthermore, in mice xenograft tumor model, HSBP1 increased sensitivity of OSCC to radiotherapy. Above all, HSBP1 is a potential marker for prognosis of OSCC after radiotherapy.

Molecular cloning, characterization and expression analysis of three heat shock responsive genes from Haliotis diversicolor

In this study, molecular characterization and expression of three heat shock responsive genes were analyzed as indicators to understand the mechanism of heat shock response of small abalone Haliotis diversicolor under stresses. The full length cDNA of heat shock transcriptional factor 1 (HdHSF1), heat shock factor binding protein 1(HSBP1), and heat shock protein 90 (HdHSP90) are 1548 bp, 809 bp, and 2592 bp respectively, encoding a protein of 515 aa, 75 aa, and 728 aa respectively. Real time quantitative PCR analysis revealed that these three genes are constitutively expressed in 7 selected tissues. The expression level of HdHSF1 in gills was higher than that in other tissues (p < 0.05). The highest expression level of HdHSBP1 was detected in hemocytes. The highest expression level of HdHSP90 was in the digestive tract and colleterial gland. The HdHSF1 expression level in the gills was up-regulated significantly (p < 0.05) after thermal stress and hypoxia exposure respectively. On the contrary, HdHSBP1 was down-regulated both in gills and hemocytes after thermal stress and the same as in gills after hypoxia stress. HdHSP90 expression level was also up-regulated in gills and hemocytes after both thermal and hypoxia stresses. These results indicated that these three heat shock responsive genes play important roles in response to thermal and hypoxia stress.

Genetic variations of HSBP1 gene and its effect on thermal performance traits in Chinese Holstein cattle

Molecular chaperones have been understood to be preferentially transcribed to prevent perturbations in response to various stresses. In this study, three single nucleotide polymorphisms (SNPs), g.324G>C, g.589C>T and g.651C>G in Heat shock factor binding protein 1 (HSBP1) gene were found and genotyped in 930 Chinese Holstein cattle. The results indicated that only g.589C>T polymorphism locus met Hardy-Weinberg equilibrium (P > 0.05). Pair linkage disequilibrium analysis and haplotype construction of HSBP1 gene were performed using SHEsis software. Seven haplotypes were constructed and fourteen haplotype combinations were found. Association analysis showed that H2H2 haplotype combination was advantageous for thermo tolerance breeding in Chinese Holstein. The cows with H2H2 haplotype combination have lower decrease rate of milk yield than those with H2H3 haplotype combination (P < 0.05) and lower potassium content in erythrocytes (PCE) than those with H2H5 (P < 0.05), H4H4 (P < 0.05) and H4H5 (P < 0.01) haplotype combination. The association between SNP and thermo tolerance traits showed that PCE of cows with GG genotype was lower than those with CG genotype at g.651C>G locus (P < 0.01). Pair linkage disequilibrium analysis revealed that the three loci were at a strong disequilibrium state. So we presumed that the effect of H2H2 haplotype combination on thermo tolerance traits major due to the SNP of g.651C>G.

Discovery of variants unmasked by hemizygous deletions

Array-based genome-wide segmental aneuploidy screening detects both de novo and inherited copy number variations (CNVs). In sporadic patients de novo CNVs are interpreted as potentially pathogenic. However, a deletion, transmitted from a healthy parent, may be pathogenic if it overlaps with a mutated second allele inherited from the other healthy parent. To detect such events, we performed multiplex enrichment and next-generation sequencing of the entire coding sequence of all genes within unique hemizygous deletion regions in 20 patients (1.53 Mb capture footprint). Out of the detected 703 non-synonymous single-nucleotide variants (SNVs), 8 represented variants being unmasked by a hemizygous deletion. Although evaluation of inheritance patterns, Grantham matrix scores, evolutionary conservation and bioinformatic predictions did not consistently indicate pathogenicity of these variants, no definitive conclusions can be drawn without functional validation. However, in one patient with severe mental retardation, lack of speech, microcephaly, cheilognathopalatoschisis and bilateral hearing loss, we discovered a second smaller deletion, inherited from the other healthy parent, resulting in loss of both alleles of the highly conserved heat shock factor binding protein 1 (HSBP1) gene. Conceivably, inherited deletions may unmask rare pathogenic variants that may exert a phenotypic impact through a recessive mode of gene action.

Expression, Purification and Crystallization of Heat Shock Factor Binding Protein 1*

Heat shock response rises when the organisms in the environmental stimulate. During heat shock, a lot of proteins which is so called heat shock protein that do not express in normal state largely express. These proteins′ expression is regulated by a family of transcription factor. These proteins were called heat shock transcriptional factors (HSFs). Among these HSFs, HSF1 is the most important protein. And HSFs are also regulated by other proteins, such as heat shock factor binding protein1 (HSBP1). HSBP1 interact with the trimer formation of HSF1 to convert the HSF1 from its active trimer state to inert monomer state. In order to do the further functional investigation, the gene of HSBP1 was cloned by PCR using the virus cDNAs as templates and expressed in Escherichia coli BL21 (DE3). Furthermore, the expressed HSBP1 protein was purified and crystallized. The distinct crystal form was obtained by the hanging-drop vapor-diffusion process to carry on screening and the optimization to the crystallization condition. The crystals belong to R3 space group with the cell parameter a = b = 35.2, c = 233.3.

Manipulating Heat Shock Factor-1 in Xenopus Tadpoles: Neuronal Tissues Are Refractory to Exogenous Expression

BackgroundThe aging related decline of heat shock factor-1 (HSF1) signaling may be causally related to protein aggregation diseases. To model such disease, we tried to cripple HSF1 signaling in the Xenopus tadpole.ResultsOver-expression of heat shock factor binding protein-1 did not inhibit the heat shock response in Xenopus. RNAi against HSF1 mRNA inhibited the heat shock response by 70% in Xenopus A6 cells, but failed in transgenic tadpoles. Expression of XHSF380, a dominant-negative HSF1 mutant, was embryonic lethal, which could be circumvented by delaying expression via a tetracycline inducible promoter. HSF1 signaling is thus essential for embryonic Xenopus development. Surprisingly, transgenic expression of the XHSF380 or of full length HSF1, whether driven by a ubiquitous or a neural specific promoter, was not detectable in the larval brain.ConclusionsOur finding that the majority of neurons, which have little endogenous HSF1, refused to accept transgene-driven expression of HSF1 or its mutant suggests that HSF1 levels are strictly controlled in neuronal tissue.

An Evolutionarily Conserved Sexual Signature in the Primate Brain

The question of a potential biological sexual signature in the human brain is a heavily disputed subject. In order to provide further insight into this issue, we used an evolutionary approach to identify genes with sex differences in brain expression level among primates. We reasoned that expression patterns important to uphold key male and female characteristics may be conserved during evolution. We selected cortex for our studies because this specific brain region is responsible for many higher behavioral functions. We compared gene expression profiles in the occipital cortex of male and female humans (Homo sapiens, a great ape) and cynomolgus macaques (Macaca fascicularis, an old world monkey), two catarrhine species that show abundant morphological sexual dimorphism, as well as in common marmosets (Callithrix Jacchus, a new world monkey) which are relatively sexually monomorphic. We identified hundreds of genes with sex-biased expression patterns in humans and macaques, while fewer than ten were differentially expressed between the sexes in marmosets. In primates, a general rule is that many of the morphological and behavioral sexual dimorphisms seen in polygamous species, such as macaques, are typically less pronounced in monogamous species such as the marmosets. Our observations suggest that this correlation may also be reflected in the extent of sex-biased gene expression in the brain. We identified 85 genes with common sex-biased expression, in both human and macaque and 2 genes, X inactivation-specific transcript (XIST) and Heat shock factor binding protein 1 (HSBP1), that were consistently sex-biased in the female direction in human, macaque, and marmoset. These observations imply a conserved signature of sexual gene expression dimorphism in cortex of primates. Further, we found that the coding region of female-biased genes is more evolutionarily constrained compared to the coding region of both male-biased and non sex-biased brain expressed genes. We found genes with conserved sexual gene expression dimorphism in the occipital cortex of humans, cynomolgus macaques, and common marmosets. Genes within sexual expression profiles may underlie important functional differences between the sexes, with possible importance during primate evolution.

The maize heat shock factor-binding protein paralogs EMP2 and HSBP2 interact non-redundantly with specific heat shock factors

The heat shock response (HSR) is a conserved mechanism by which transcripts of heat shock protein (hsp) genes accumulate following mobilization of heat shock transcription factors (HSFs) in response to thermal stress. Studies in animals identified the heat shock factor-binding protein1 (HSBP1) that interacts with heat shock transcription factor1 (HSF1) during heat shock attenuation; overexpression analyses revealed that the coiled-coil protein HSBP1 functions as a negative regulator of the HSR. Zea mays contains two HSBP paralogs, EMP2 and HSBP2, which exhibit differential accumulation during the HSR and plant development. Embryo-lethal recessive emp2 mutations revealed that EMP2 is required for the down-regulation of hsp transcription during embryogenesis, whereas accumulation of HSBP2 is induced in seedlings following heat shock. Notwithstanding, no interaction has yet been demonstrated between a plant HSBP and a plant HSF. In this report 22 maize HSF isoforms are identified comprising three structural classes: HSF-A, HSF-B and HSF-C. Phylogenetic analysis of Arabidopsis, maize and rice HSFs reveals that at least nine ancestral HSF isoforms were present prior to the separation of monocot and eudicots, followed by differential amplification of HSF members in these lineages. Yeast two-hybrid analyses show that EMP2 and HSBP2 interact non-redundantly with specific HSF-A isoforms. Site-specific mutagenesis of HSBP2 reveals that interactions between hydrophobic residues within the coiled coil are required for HSF::HSBP2 binding; domain swapping demonstrate that the isoform specificity of HSF::HSBP interaction is conferred by residues outside of the coiled coil. These data suggest that the non-redundant functions of the maize HSBPs may be explained, at least in part, by the specificity of HSBP::HSF interactions during plant development.

PTHrP [67-86] regulates the expression of stress proteins in breast cancer cells inducing modifications in urokinase-plasminogen activator and MMP-1 expression.

It was previously reported that a midregion domain of parathyroid hormone-related protein (PTHrP), that is, [67-86]-amide, is able to restrain growth and promote matrigel penetration by the 8701-BC cell line, derived from a biopsy fragment of a primary ductal infiltrating carcinoma of the human breast, and that cell invasion in vitro is drastically impaired by inactivation of urokinase-plasminogen activator (uPa). In this study we started a more detailed investigation of the possible effects on gene expression arising from the interaction between PTHrP [67-86]-amide and 8701-BC breast cancer cells by a combination of conventional-, differential display-and semi-quantitative multiplex-polymerase chain reaction (PCR) assays. We present here the first evidence that the upregulation of some stress-related genes, most noticeably heat shock factor binding protein-1 (hsbp1) and heat shock protein 90 (hsp-90), is involved in the acquisition of an in vitro more invasive phenotype by cells treated with midregion PTHrP. This is conceivably accomplished by sequestering and inactivating heat shock factor-1 (hsf1) which is able to recognize Ets transcription-factor-binding sites present in some gene promoters, such as those of uPa and matrix metalloprotease-1 (MMP-1). In fact, our data show that incubation of PTHrP [67-86]-amide-treated cells with either antisense hsbp1-oligonucleotide or geldanamycin, an hsp90-inactivating antibiotic, results in downregulation of uPa and upregulation of MMP-1, and in a prominent inhibition of cell invasion in matrigel-containing Transwell chambers. Alternatively, incubation of untreated 8701-BC cells with quercetin, a flavonoid known to decrease the amount of free hsf1, is found to induce upregulation of uPa and downregulation of MMP-1, and an increase of matrigel invasion by cells, thus providing further supporting data of the involvement of hsf unavailability on the modulation of uPa and MMP-1 expression and on cell invasive behaviour. These studies confirm a previous postulate that over-secretion of uPa, rather than of other extracellular proteases, is a primary condition for the increase of invasive activity triggered by PTHrP [67-86]-amide in vitro, and support a role for midregion forms of PTHrP in potentially affecting pathological mammary growth and differentiation. They also identify two new key protagonists in the complex scenario of breast tumor cell invasiveness in vitro, that is, hsbp1 and hsp90, which deserve further and more extensive studies as potential and attractive molecular targets for anti-breast cancer treatments.

Negative regulation of the heat shock transcriptional response by HSBP1.

In response to stress, heat shock factor 1 (HSF1) acquires rapid DNA binding and transient transcriptional activity while undergoing conformational transition from an inert non-DNA-binding monomer to active functional trimers. Attenuation of the inducible transcriptional response occurs during heat shock or upon recovery at non-stress conditions and involves dissociation of the HSF1 trimer and loss of activity. We have used the hydrophobic repeats of the HSF1 trimerization domain in the yeast two-hybrid protein interaction assay to identify heat shock factor binding protein 1 (HSBP1), a novel, conserved, 76-amino-acid protein that contains two extended arrays of hydrophobic repeats that interact with the HSF1 heptad repeats. HSBP1 is nuclear-localized and interacts in vivo with the active trimeric state of HSF1 that appears during heat shock. During attenuation of HSF1 to the inert monomer, HSBP1 associates with Hsp70. HSBP1 negatively affects HSF1 DNA-binding activity, and overexpression of HSBP1 in mammalian cells represses the transactivation activity of HSF1. To establish a biological role for HSBP1, the homologous Caenorhabditis elegans protein was overexpressed in body wall muscle cells and was shown to block activation of the heat shock response from a heat shock promoter-reporter construct. Alteration in the level of HSBP1 expression in C. elegans has severe effects on survival of the animals after thermal and chemical stress, consistent with a role for HSBP1 as a negative regulator of the heat shock response.