ATF1 modulates the heat shock response by regulating the stress-inducible heat shock factor 1 transcription complex

Heat shock proteins as a key defense mechanism in poultry production under heat stress conditions

Over the past years, the poultry industry has been assigned to greater production performance but has become highly sensitive to environmental changes. The average world temperature has recently risen and is predicted to continue rising. In open-sided houses, poultry species confront high outside temperatures, which cause heat stress (HS) problems. Cellular responses are vital in poultry, as they may lead to identifying confirmed HS biomarkers. Heat shock proteins (HSP) are highly preserved protein families that play a significant role in cell function and cytoprotection against various stressors, including HS. The optimal response in which the cell survives the HS elevates HSP levels that prevent cellular proteins from damage caused by HS. The HSP have chaperonic action to ensure that stress-denatured proteins are folded, unfolded, and refolded. The HSP70 and HSP90 are the primary HSP in poultry with a defensive function during HS. HSP70 was the optimal biological marker for assessing HS among the HSP studied. The current review attempts to ascertain the value of HSP as a heat stress defense mechanism in poultry.

Involvement of transcriptional co-activator p300 in upregulated expression of HSP70 by aquareovirus non-structural protein NS31

Members of Aquareovirus genus, including grass carp reovirus (GCRV), contribute to a serious threat to aquaculture animals accompanied by stress response. Our previous reports revealed that GCRV nonstructural protein NS31 serves as a potent contributor for virus selectively up-regulating specific heat shock protein 70-kd gene（HSP70），however，the mechanism by which inducing HSP70 gene expression is unknown. In this study, we further found that either the N- or C-terminal domain of GCRV NS31 is responsible for enhancing fish HSP70 promoter transcription, and recombinant NS31 protein purified from baculovirus expression system seems to not directly bind HSP70 basic promoter in vitro by an electrophoretic mobility shift assay. However, the transcriptional co-activator p300 was identified as a potential interacting partner for NS31 by pull-down assay. Moreover, knock-down of p300 or addition of p300 inhibitor resulted in obviously reduced HSP70 expression by NS31 or GCRV infection suggesting that the well-characterized heat-shock-responsive HSF1/p300 transcriptional complex might involve in the induction of HSP70. These results collectively reveal this aquareovirus generates cell stress response through its nonstructural protein NS31 recruiting transcriptional co-activator p300.

ATF1 promotes the malignancy of lung adenocarcinoma cells by transcriptionally regulating ZNF143 expression

The clinical oncogenic functions and mechanisms of activating transcription factor 1 (ATF1) in the progression of lung adenocarcinoma have not been completely elucidated. In this study, by employing human lung adenocarcinoma tissues and cells, we detect the correlation of ATF1 expression with the clinicopathological features and prognosis of patients with lung adenocarcinoma and find that ATF1 promotes lung adenocarcinoma cell proliferation and migration by transcriptionally enhancing zinc finger protein 143 (ZNF143) expression. ATF1 and ZNF143 are strongly expressed in lung adenocarcinoma tissues compared with those in the adjacent normal tissues, and high ATF1 and ZNF143 expressions are related to poor disease-free survival of lung adenocarcinoma patients. ATF1 overexpression results in increased proliferation and migration of lung adenocarcinoma cells, whereas knockdown of ATF1 inhibits cell proliferation and migration. Furthermore, ATF1 transcriptionally regulates the expression of ZNF143, and ATF1 and ZNF143 expressions are positively correlated in lung adenocarcinoma tissues. ZNF143 knockdown blocks lung adenocarcinoma cell migration, which is mediated by ATF1 upregulation. Hence, this study provides a potential therapeutic candidate for the treatment of lung adenocarcinoma.

Identification of Candidate Genes for Min Pig Villi Hair Traits by Genome-Wide Association of Copy Number Variation

The Min pig is a famous native pig breed in northeast China, which has the special genetic character of villi hair growth in cold seasons. At present, little research has focused on the genetic mechanism of villi hair growth in Min pigs. Copy number variations (CNVs) are a type of variant that may influence many traits. In this study, we first investigated the phenotype of Large White × Min pigs' F2 pig villi hair in detail and then performed a CNV-based genome-wide association study (GWAS) between CNVs and pig villi hair appearance. Finally, a total number of 15 significant CNVRs were found to be associated with Min pig villi hair. The most significant CNVR was located on chromosome 1. Nearest gene annotation analysis indicated that the pig villi hair traits may be associated with the biological process of the G-protein-coupled receptor signaling pathway. QTL overlapping analysis found that among the CNVRs, 14 CNVRs could be co-located with known QTLs. Some genes such as MCHR2, LTBP2, and GFRA2 may be candidate genes for pig villi traits and are worth further study. Our study may provide a basic reference for the selection and breeding of cold-resistant pigs and outdoor breeding.

The potential roles of ATF family in the treatment of Alzheimer's disease

Activating transcription factors, ATFs, is a family of transcription factors that activate gene expression and transcription by recognizing and combining the cAMP response element binding proteins (CREB). It is present in various viruses as a cellular gene promoter. ATFs is involved in regulating the mammalian gene expression that is associated with various cell physiological processes. Therefore, ATFs play an important role in maintaining the intracellular homeostasis. ATF2 and ATF3 is mostly involved in mediating stress responses. ATF4 regulates the oxidative metabolism, which is associated with the survival of cells. ATF5 is presumed to regulate apoptosis, and ATF6 is involved in the regulation of endoplasmic reticulum stress (ERS). ATFs is actively studied in oncology. At present, there has been an increasing amount of research on ATFs for the treatment of neurological diseases. Here, we have focused on the different types of ATFs and their association with Alzheimer's disease (AD). The level of expression of different ATFs have a significant difference in AD patients when compared to healthy control. Recent studies have suggested that ATFs are implicated in the pathogenesis of AD, such as neuronal repair, maintenance of synaptic activity, maintenance of cell survival, inhibition of apoptosis, and regulation of stress responses. In this review, the potential role of ATFs for the treatment of AD has been highlighted. In addition, we have systematically reviewed the progress of research on ATFs in AD. This review will provide a basic and innovative understanding on the pathogenesis and treatment of AD.

HSF1 phosphorylation establishes an active chromatin state via the TRRAP-TIP60 complex and promotes tumorigenesis

Transcriptional regulation by RNA polymerase II is associated with changes in chromatin structure. Activated and promoter-bound heat shock transcription factor 1 (HSF1) recruits transcriptional co-activators, including histone-modifying enzymes; however, the mechanisms underlying chromatin opening remain unclear. Here, we demonstrate that HSF1 recruits the TRRAP-TIP60 acetyltransferase complex in HSP72 promoter during heat shock in a manner dependent on phosphorylation of HSF1-S419. TRIM33, a bromodomain-containing ubiquitin ligase, is then recruited to the promoter by interactions with HSF1 and a TIP60-mediated acetylation mark, and cooperates with the related factor TRIM24 for mono-ubiquitination of histone H2B on K120. These changes in histone modifications are triggered by phosphorylation of HSF1-S419 via PLK1, and stabilize the HSF1-transcription complex in HSP72 promoter. Furthermore, HSF1-S419 phosphorylation is constitutively enhanced in and promotes proliferation of melanoma cells. Our results provide mechanisms for HSF1 phosphorylation-dependent establishment of an active chromatin status, which is important for tumorigenesis.

Here the authors show phosphorylation of heat shock factor 1 (HSF1) at S419 via the chromatin-bound kinase PLK1, promotes HSF1 recruitment of histone acetyltransferases and histone acetylation reader proteins TRIM33 and TRIM24, which actually also execute histone H2BK120 mono-ubiquitination at target genes. Furthermore, HSF1 phosphorylation has an impact on melanoma cell proliferation.

Strategies for Improving Photodynamic Therapy Through Pharmacological Modulation of the Immediate Early Stress Response

Photodynamic therapy (PDT) is a minimally to noninvasive treatment modality that has emerged as a promising alternative to conventional cancer treatments. PDT induces hyperoxidative stress and disrupts cellular homeostasis in photosensitized cancer cells, resulting in cell death and ultimately removal of the tumor. However, various survival pathways can be activated in sublethally afflicted cancer cells following PDT. The acute stress response is one of the known survival pathways in PDT, which is activated by reactive oxygen species and signals via ASK-1 (directly) or via TNFR (indirectly). The acute stress response can activate various other survival pathways that may entail antioxidant, pro-inflammatory, angiogenic, and proteotoxic stress responses that culminate in the cancer cell's ability to cope with redox stress and oxidative damage. This review provides an overview of the immediate early stress response in the context of PDT, mechanisms of activation by PDT, and molecular intervention strategies aimed at inhibiting survival signaling and improving PDT outcome.

Molecular mechanisms of heat shock factor 1 regulation

To thrive and to fulfill their functions, cells need to maintain proteome homeostasis even in the face of adverse environmental conditions or radical restructuring of the proteome during differentiation. At the center of the regulation of proteome homeostasis is an ancient transcriptional mechanism, the so-called heat shock response (HSR), orchestrated in all eukaryotic cells by heat shock transcription factor 1 (Hsf1). As Hsf1 is implicated in aging and several pathologies like cancer and neurodegenerative disorders, understanding the regulation of Hsf1 could open novel therapeutic opportunities. In this review, we discuss the regulation of Hsf1's transcriptional activity by multiple layers of control circuits involving Hsf1 synthesis and degradation, conformational rearrangements and post-translational modifications (PTMs), and molecular chaperones in negative feedback loops.

Multifaceted roles of HSF1 in cell death: A state-of-the-art review

Cell death is a common and active process that is involved in various biological processes, including organ development, morphogenesis, maintaining tissue homeostasis and eliminating potentially harmful cells. Abnormal regulation of cell death significantly contributes to tumor development, progression and chemoresistance. The mechanisms of cell death are complex and involve not only apoptosis and necrosis but also their cross-talk with other types of cell death, such as autophagy and the newly identified ferroptosis. Cancer cells are chronically exposed to various stresses, such as lack of oxygen and nutrients, immune responses, dysregulated metabolism and genomic instability, all of which lead to activation of heat shock factor 1 (HSF1). In response to heat shock, oxidative stress and proteotoxic stresses, HSF1 upregulates transcription of heat shock proteins (HSPs), which act as molecular chaperones to protect normal cells from stresses and various diseases. Accumulating evidence suggests that HSF1 regulates multiple types of cell death through different signaling pathways as well as expression of distinct target genes in cancer cells. Here, we review the current understanding of the potential roles and molecular mechanism of HSF1 in regulating apoptosis, autophagy and ferroptosis. Deciphering HSF1-regulated signaling pathways and target genes may help in the development of new targeted anti-cancer therapeutic strategies.

A Gene Expression Biomarker Predicts Heat Shock Factor 1 Activation in a Gene Expression Compendium

The United States Environmental Protection Agency (US EPA) recently developed a tiered testing strategy to use advances in high-throughput transcriptomics (HTTr) testing to identify molecular targets of thousands of environmental chemicals that can be linked to adverse outcomes. Here, we describe a method that uses a gene expression biomarker to predict chemical activation of heat shock factor 1 (HSF1), a transcription factor critical for proteome maintenance. The HSF1 biomarker was built from transcript profiles derived from A375 cells exposed to a HSF1-activating heat shock protein (HSP) 90 inhibitor in the presence or absence of HSF1 expression. The resultant 44 identified genes included those that (1) are dependent on HSF1 for regulation, (2) have direct interactions with HSF1 assessed by ChIP-Seq, and (3) are in the molecular chaperone family. To test for accuracy, the biomarker was compared in a pairwise manner to gene lists derived from treatments with known HSF1 activity (HSP and proteasomal inhibitors) using the correlation-based Running Fisher test; the balanced accuracy for prediction was 96%. A microarray compendium consisting of 12,092 microarray comparisons from human cells exposed to 2670 individual chemicals was screened using our approach; 112 and 19 chemicals were identified as putative HSF1 activators or suppressors, respectively, and most appear to be novel modulators. A large percentage of the chemical treatments that induced HSF1 also induced oxidant-activated NRF2 (∼46%). For five compounds or mixtures, we found that NRF2 activation occurred at lower concentrations or at earlier times than HSF1 activation, supporting the concept of a tiered cellular protection system dependent on the level of chemical-induced stress. The approach described here could be used to identify environmentally relevant chemical HSF1 activators in HTTr data sets.

Pan-Cancer Analysis of the Prognostic and Immunological Role of HSF1: A Potential Target for Survival and Immunotherapy

Emerging evidence revealed the significant roles of heat shock factor 1 (HSF1) in cancer initiation, development, and progression, but there is no pan-cancer analysis of HSF1. The present study first comprehensively investigated the expression profiles and prognostic significance of HSF1 and the relationship of HSF1 with clinicopathological parameters and immune cell infiltration using bioinformatic techniques. HSF1 is significantly upregulated in various common cancers, and it is associated with prognosis. Pan-cancer Cox regression analysis indicated that the high expression of HSF1 was associated with poor overall survival (OS), disease-specific survival (DSS), and progression-free interval (PFI) in cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), head and neck squamous cell carcinoma (HNSC), and kidney renal papillary cell carcinoma (KIRP) patients. The methylation of HSF1 DNA was decreased in most cancers and negatively correlated with the HSF1 expression. Increased phosphorylation of S303, S307, and S363 in HSF1 was observed in some cancers. HSF1 remarkably correlated with the levels of infiltrating cells and immune checkpoint genes. Our pan-cancer analysis provides a deep understanding of the functions of HSF1 in oncogenesis and metastasis in different cancers.

MED12 interacts with the heat-shock transcription factor HSF1 and recruits CDK8 to promote the heat-shock response in mammalian cells

Activated and promoter-bound heat-shock transcription factor 1 (HSF1) induces RNA polymerase II recruitment upon heat shock, and this is facilitated by the core Mediator in Drosophila and yeast. Another Mediator module, CDK8 kinase module (CKM), consisting of four subunits including MED12 and CDK8, plays a negative or positive role in the regulation of transcription; however, its involvement in HSF1-mediated transcription remains unclear. We herein demonstrated that HSF1 interacted with MED12 and recruited MED12 and CDK8 to the HSP70 promoter during heat shock in mammalian cells. The kinase activity of CDK8 (and its paralog CDK19) promoted HSP70 expression partly by phosphorylating HSF1-S326 and maintained proteostasis capacity. These results indicate an important role for CKM in the protection of cells against proteotoxic stress.

Testicular localization of activating transcription factor 1 and its potential function during spermatogenesis

Activating transcription factor 1 (ATF1), belonging to the CREB/ATF family of transcription factors, is highly expressed in the testes. However, its role in spermatogenesis has not yet been established. Here, we aimed to elucidate the impact of ATF1 in spermatogenesis by examining the expression pattern of ATF1 in mice and the effect of ATF1 knockdown in the mouse testes. We found that ATF1 is expressed in various organs, with very high levels in the testes. Immunohistochemical staining showed that ATF1 was localized in the nuclei of spermatogonia and co-localized with proliferating cell nuclear antigen. In ATF1-deficient mice, the seminiferous tubules of the testis contained cells at all developmental stages; however, the number of spermatocytes was decreased. Proliferating cell nuclear antigen expression was decreased and apoptotic cells were rare in the seminiferous tubules. These results indicate that ATF1 plays a role in male germ cell proliferation and sperm production.

Molecular Chaperones in Osteosarcoma: Diagnosis and Therapeutic Issues

Osteosarcoma (OS) is the most common form of primary bone tumor affecting mainly children and young adults. Despite therapeutic progress, the 5-year survival rate is 70%, but it drops drastically to 30% for poor responders to therapies or for patients with metastases. Identifying new therapeutic targets is thus essential. Heat Shock Proteins (HSPs) are the main effectors of Heat Shock Response (HSR), the expression of which is induced by stressors. HSPs are a large family of proteins involved in the folding and maturation of other proteins in order to maintain proteostasis. HSP overexpression is observed in many cancers, including breast, prostate, colorectal, lung, and ovarian, as well as OS. In this article we reviewed the significant role played by HSPs in molecular mechanisms leading to OS development and progression. HSPs are directly involved in OS cell proliferation, apoptosis inhibition, migration, and drug resistance. We focused on HSP27, HSP60, HSP70 and HSP90 and summarized their potential clinical uses in OS as either biomarkers for diagnosis or therapeutic targets. Finally, based on different types of cancer, we consider the advantage of targeting heat shock factor 1 (HSF1), the major transcriptional regulator of HSPs in OS.

Methods for ChIP-seq analysis: A practical workflow and advanced applications

Chromatin immunoprecipitation followed by sequencing (ChIP-seq) is a central method in epigenomic research. Genome-wide analysis of histone modifications, such as enhancer analysis and genome-wide chromatin state annotation, enables systematic analysis of how the epigenomic landscape contributes to cell identity, development, lineage specification, and disease. In this review, we first present a typical ChIP-seq analysis workflow, from quality assessment to chromatin-state annotation. We focus on practical, rather than theoretical, approaches for biological studies. Next, we outline various advanced ChIP-seq applications and introduce several state-of-the-art methods, including prediction of gene expression level and chromatin loops from epigenome data and data imputation. Finally, we discuss recently developed single-cell ChIP-seq analysis methodologies that elucidate the cellular diversity within complex tissues and cancers.

Mobility connects: transposable elements wire new transcriptional networks by transferring transcription factor binding motifs

Transposable elements (TEs) constitute major fractions of plant genomes. Their potential to be mobile provides them with the capacity to cause major genome rearrangements. Those effects are potentially deleterious and enforced the evolution of epigenetic suppressive mechanisms controlling TE activity. However, beyond their deleterious effects, TE insertions can be neutral or even advantageous for the host, leading to long-term retention of TEs in the host genome. Indeed, TEs are increasingly recognized as major drivers of evolutionary novelties by regulating the expression of nearby genes. TEs frequently contain binding motifs for transcription factors and capture binding motifs during transposition, which they spread through the genome by transposition. Thus, TEs drive the evolution and diversification of gene regulatory networks by recruiting lineage-specific targets under the regulatory control of specific transcription factors. This process can explain the rapid and repeated evolution of developmental novelties, such as C₄ photosynthesis and a wide spectrum of stress responses in plants. It also underpins the convergent evolution of embryo nourishing tissues, the placenta in mammals and the endosperm in flowering plants. Furthermore, the gene regulatory network underlying flower development has also been largely reshaped by TE-mediated recruitment of regulatory elements; some of them being preserved across long evolutionary timescales. In this review, we highlight the potential role of TEs as evolutionary toolkits in plants by showcasing examples of TE-mediated evolutionary novelties.

Comparative interactomes of HSF1 in stress and disease reveal a role for CTCF in HSF1-mediated gene regulation

Heat shock transcription factor 1 (HSF1) orchestrates cellular stress protection by activating or repressing gene transcription in response to protein misfolding, oncogenic cell proliferation, and other environmental stresses. HSF1 is tightly regulated via intramolecular repressive interactions, post-translational modifications, and protein-protein interactions. How these HSF1 regulatory protein interactions are altered in response to acute and chronic stress is largely unknown. To elucidate the profile of HSF1 protein interactions under normal growth and chronic and acutely stressful conditions, quantitative proteomics studies identified interacting proteins in the response to heat shock or in the presence of a poly-glutamine aggregation protein cell-based model of Huntington's disease. These studies identified distinct protein interaction partners of HSF1 as well as changes in the magnitude of shared interactions as a function of each stressful condition. Several novel HSF1-interacting proteins were identified that encompass a wide variety of cellular functions, including roles in DNA repair, mRNA processing, and regulation of RNA polymerase II. One HSF1 partner, CTCF, interacted with HSF1 in a stress-inducible manner and functions in repression of specific HSF1 target genes. Understanding how HSF1 regulates gene repression is a crucial question, given the dysregulation of HSF1 target genes in both cancer and neurodegeneration. These studies expand our understanding of HSF1-mediated gene repression and provide key insights into HSF1 regulation via protein-protein interactions.

HSF1 is required for induction of mitochondrial chaperones during the mitochondrial unfolded protein response

The mitochondrial unfolded protein response (UPR^mt ) is characterized by the transcriptional induction of mitochondrial chaperone and protease genes in response to impaired mitochondrial proteostasis and is regulated by ATF5 and CHOP in mammalian cells. However, the detailed mechanisms underlying the UPR^mt are currently unclear. Here, we show that HSF1 is required for activation of mitochondrial chaperone genes, including HSP60, HSP10, and mtHSP70, in mouse embryonic fibroblasts during inhibition of matrix chaperone TRAP1, protease Lon, or electron transfer complex 1 activity. HSF1 bound constitutively to mitochondrial chaperone gene promoters, and we observed that its occupancy was remarkably enhanced at different levels during the UPR^mt . Furthermore, HSF1 supported the maintenance of mitochondrial function under the same conditions. These results demonstrate that HSF1 is required for induction of mitochondrial chaperones during the UPR^mt , and thus, it may be one of the guardians of mitochondrial function under conditions of impaired mitochondrial proteostasis.

Molecular Mechanisms of Heat Shock Factors in Cancer

Malignant transformation is accompanied by alterations in the key cellular pathways that regulate development, metabolism, proliferation and motility as well as stress resilience. The members of the transcription factor family, called heat shock factors (HSFs), have been shown to play important roles in all of these biological processes, and in the past decade it has become evident that their activities are rewired during tumorigenesis. This review focuses on the expression patterns and functions of HSF1, HSF2, and HSF4 in specific cancer types, highlighting the mechanisms by which the regulatory functions of these transcription factors are modulated. Recently developed therapeutic approaches that target HSFs are also discussed.

Diverse families of transposable elements affect the transcriptional regulation of stress-response genes in Drosophila melanogaster

Although transposable elements are an important source of regulatory variation, their genome-wide contribution to the transcriptional regulation of stress-response genes has not been studied yet. Stress is a major aspect of natural selection in the wild, leading to changes in the transcriptional regulation of a variety of genes that are often triggered by one or a few transcription factors. In this work, we take advantage of the wealth of information available for Drosophila melanogaster and humans to analyze the role of transposable elements in six stress regulatory networks: immune, hypoxia, oxidative, xenobiotic, heat shock, and heavy metal. We found that transposable elements were enriched for caudal, dorsal, HSF, and tango binding sites in D. melanogaster and for NFE2L2 binding sites in humans. Taking into account the D. melanogaster population frequencies of transposable elements with predicted binding motifs and/or binding sites, we showed that those containing three or more binding motifs/sites are more likely to be functional. For a representative subset of these TEs, we performed in vivo transgenic reporter assays in different stress conditions. Overall, our results showed that TEs are relevant contributors to the transcriptional regulation of stress-response genes.

Inhibiting Heat Shock Factor 1 in Cancer: A Unique Therapeutic Opportunity

The ability of cancer cells to cope with stressful conditions is critical for their survival, proliferation, and metastasis. The heat shock transcription factor 1 (HSF1) protects cells from stresses such as chemicals, radiation, and temperature. These properties of HSF1 are exploited by a broad spectrum of cancers, which exhibit high levels of nuclear, active HSF1. Functions for HSF1 in malignancy extend well beyond its central role in protein quality control. While HSF1 has been validated as a powerful target in cancers by genetic knockdown studies, HSF1 inhibitors reported to date have lacked sufficient specificity and potency for clinical evaluation. We review the roles of HSF1 in cancer, its potential as a prognostic indicator for cancer treatment, evaluate current HSF1 inhibitors and provide guidelines for the identification of selective HSF1 inhibitors as chemical probes and for clinical development.

The pericentromeric protein shugoshin 2 cooperates with HSF1 in heat shock response and RNA Pol II recruitment

The recruitment of RNA polymerase II (Pol II) to core promoters is highly regulated during rapid induction of genes. In response to heat shock, heat shock transcription factor 1 (HSF1) is activated and occupies heat shock gene promoters. Promoter-bound HSF1 recruits general transcription factors and Mediator, which interact with Pol II, but stress-specific mechanisms of Pol II recruitment are unclear. Here, we show in comparative analyses of HSF1 paralogs and their mutants that HSF1 interacts with the pericentromeric adaptor protein shugoshin 2 (SGO2) during heat shock in mouse cells, in a manner dependent on inducible phosphorylation of HSF1 at serine 326, and recruits SGO2 to the HSP70 promoter. SGO2-mediated binding and recruitment of Pol II with a hypophosphorylated C-terminal domain promote expression of HSP70, implicating SGO2 as one of the coactivators that facilitate Pol II recruitment by HSF1. Furthermore, the HSF1-SGO2 complex supports cell survival and maintenance of proteostasis in heat shock conditions. These results exemplify a proteotoxic stress-specific mechanism of Pol II recruitment, which is triggered by phosphorylation of HSF1 during the heat shock response.

Antioxidant Defence Systems and Oxidative Stress in Poultry Biology: An Update

Poultry in commercial settings are exposed to a range of stressors. A growing body of information clearly indicates that excess ROS/RNS production and oxidative stress are major detrimental consequences of the most common commercial stressors in poultry production. During evolution, antioxidant defence systems were developed in poultry to survive in an oxygenated atmosphere. They include a complex network of internally synthesised (e.g., antioxidant enzymes, (glutathione) GSH, (coenzyme Q) CoQ) and externally supplied (vitamin E, carotenoids, etc.) antioxidants. In fact, all antioxidants in the body work cooperatively as a team to maintain optimal redox balance in the cell/body. This balance is a key element in providing the necessary conditions for cell signalling, a vital process for regulation of the expression of various genes, stress adaptation and homeostasis maintenance in the body. Since ROS/RNS are considered to be important signalling molecules, their concentration is strictly regulated by the antioxidant defence network in conjunction with various transcription factors and vitagenes. In fact, activation of vitagenes via such transcription factors as Nrf2 leads to an additional synthesis of an array of protective molecules which can deal with increased ROS/RNS production. Therefore, it is a challenging task to develop a system of optimal antioxidant supplementation to help growing/productive birds maintain effective antioxidant defences and redox balance in the body. On the one hand, antioxidants, such as vitamin E, or minerals (e.g., Se, Mn, Cu and Zn) are a compulsory part of the commercial pre-mixes for poultry, and, in most cases, are adequate to meet the physiological requirements in these elements. On the other hand, due to the aforementioned commercially relevant stressors, there is a need for additional support for the antioxidant system in poultry. This new direction in improving antioxidant defences for poultry in stress conditions is related to an opportunity to activate a range of vitagenes (via Nrf2-related mechanisms: superoxide dismutase, SOD; heme oxygenase-1, HO-1; GSH and thioredoxin, or other mechanisms: Heat shock protein (HSP)/heat shock factor (HSP), sirtuins, etc.) to maximise internal AO protection and redox balance maintenance. Therefore, the development of vitagene-regulating nutritional supplements is on the agenda of many commercial companies worldwide.

Tailoring of Proteostasis Networks with Heat Shock Factors

Heat shock factors (HSFs) are the main transcriptional regulators of the heat shock response and indispensable for maintaining cellular proteostasis. HSFs mediate their protective functions through diverse genetic programs, which are composed of genes encoding molecular chaperones and other genes crucial for cell survival. The mechanisms that are used to tailor HSF-driven proteostasis networks are not yet completely understood, but they likely comprise from distinct combinations of both genetic and proteomic determinants. In this review, we highlight the versatile HSF-mediated cellular functions that extend from cellular stress responses to various physiological and pathological processes, and we underline the key advancements that have been achieved in the field of HSF research during the last decade.

Poly(ADP-Ribose) Polymerase 1 Promotes the Human Heat Shock Response by Facilitating Heat Shock Transcription Factor 1 Binding to DNA

The heat shock response (HSR) is characterized by the rapid and robust induction of heat shock proteins (HSPs), including HSP70, in response to heat shock and is regulated by heat shock transcription factor 1 (HSF1) in mammalian cells. Poly(ADP-ribose) polymerase 1 (PARP1), which can form a complex with HSF1 through the scaffold protein PARP13, has been suggested to be involved in the HSR. However, its effects on and the regulatory mechanisms of the HSR are not well understood. Here we show that prior to heat shock, the HSF1-PARP13-PARP1 complex binds to the HSP70 promoter. In response to heat shock, activated and auto-PARylated PARP1 dissociates from HSF1-PARP13 and is redistributed throughout the HSP70 locus. Remarkably, chromatin in the HSP70 promoter is initially PARylated at high levels and decondensed, whereas chromatin in the gene body is moderately PARylated afterwards. Activated HSF1 then binds to the promoter efficiently and promotes the HSR. Chromatin PARylation and HSF1 binding to the promoter are also facilitated by the phosphorylation-dependent dissociation of PARP13. Furthermore, the HSR and proteostasis capacity are reduced by pretreatment with genotoxic stresses, which disrupt the ternary complex. These results illuminate one of the priming mechanisms of the HSR that facilitates the binding of HSF1 to DNA during heat shock.

Acute HSF1 depletion induces cellular senescence through the MDM2-p53-p21 pathway in human diploid fibroblasts

Heat shock transcription factor 1 (HSF1) regulates the expression of a wide array of genes, control of the expression of heat shock proteins (HSPs) and cell growth. Although acute depletion of HSF1 induces cellular senescence, the underlying mechanisms are poorly understood. Here, we report that HSF1 depletion-induced senescence (HDIS) of human diploid fibroblasts (HDFs) was independent of HSP-mediated proteostasis but dependent on activation of the p53-p21 pathway, partly because of the increased expression of dehydrogenase/reductase 2 (DHRS2), a putative MDM2 inhibitor. We observed that HDIS occurred without decreased levels of major HSPs or increased proteotoxic stress in HDFs. Additionally, an inhibitor of HSP70 family proteins increased proteotoxicity and suppressed cell growth, but failed to induce senescence. Importantly, we found that activation of the p53-p21 pathway due to reduced MDM2-dependent p53 degradation was required for HDIS. Furthermore, we provide evidence that increased DHRS2 expression contributes to p53 stabilization and HDIS. Collectively, our observations uncovered a molecular pathway in which HSF1 depletion-induced DHRS2 expression leads to activation of the MDM2-p53-p21 pathway required for HDIS.

The HSF1-PARP13-PARP1 complex facilitates DNA repair and promotes mammary tumorigenesis

Poly(ADP-ribose) polymerase 1 (PARP1) is involved in DNA repair, chromatin structure, and transcription. However, the mechanisms that regulate PARP1 distribution on DNA are poorly understood. Here, we show that heat shock transcription factor 1 (HSF1) recruits PARP1 through the scaffold protein PARP13. In response to DNA damage, activated and auto-poly-ADP-ribosylated PARP1 dissociates from HSF1–PARP13, and redistributes to DNA lesions and DNA damage-inducible gene loci. Histone deacetylase 1 maintains PARP1 in the ternary complex by inactivating PARP1 through deacetylation. Blocking ternary complex formation impairs redistribution of PARP1 during DNA damage, which reduces gene expression and DNA repair. Furthermore, ternary complex formation and PARP1 redistribution protect cells from DNA damage by promoting DNA repair, and support growth of BRCA1-null mammary tumors, which are sensitive to PARP inhibitors. Our findings identify HSF1 as a regulator of genome integrity and define this function as a guarding mechanism for a specific type of mammary tumorigenesis.

PARP1 recruitment to DNA lesions is critical for DNA damage repair but how DNA damage induces PARP1 redistribution is largely unknown. Here, the authors provide evidence that PARP1 redistribution and DNA repair in tumor cells depend on the formation of a HSF1–PARP13–PARP1 complex.

New inhibitor targeting human transcription factor HSF1: effects on the heat shock response and tumor cell survival

Comparative modeling of the DNA-binding domain of human HSF1 facilitated the prediction of possible binding pockets for small molecules and definition of corresponding pharmacophores. In silico screening of a large library of lead-like compounds identified a set of compounds that satisfied the pharmacophoric criteria, a selection of which compounds was purchased to populate a biased sublibrary. A discriminating cell-based screening assay identified compound 001, which was subjected to systematic analysis of structure–activity relationships, resulting in the development of compound 115 (I_HSF115). I_HSF115 bound to an isolated HSF1 DNA-binding domain fragment. The compound did not affect heat-induced oligomerization, nuclear localization and specific DNA binding but inhibited the transcriptional activity of human HSF1, interfering with the assembly of ATF1-containing transcription complexes. I_HSF115 was employed to probe the human heat shock response at the transcriptome level. In contrast to earlier studies of differential regulation in HSF1-naïve and -depleted cells, our results suggest that a large majority of heat-induced genes is positively regulated by HSF1. That I_HSF115 effectively countermanded repression in a significant fraction of heat-repressed genes suggests that repression of these genes is mediated by transcriptionally active HSF1. I_HSF115 is cytotoxic for a variety of human cancer cell lines, multiple myeloma lines consistently exhibiting high sensitivity.

Comparative analysis reveals genomic features of stress-induced transcriptional readthrough

Transcription is a highly regulated process, and stress-induced changes in gene transcription have been shown to play a major role in stress responses and adaptation. Genome-wide studies reveal prevalent transcription beyond known protein-coding gene loci, generating a variety of RNA classes, most of unknown function. One such class, termed downstream of gene-containing transcripts (DoGs), was reported to result from transcriptional readthrough upon osmotic stress in human cells. However, how widespread the readthrough phenomenon is, and what its causes and consequences are, remain elusive. Here we present a genome-wide mapping of transcriptional readthrough, using nuclear RNA-Seq, comparing heat shock, osmotic stress, and oxidative stress in NIH 3T3 mouse fibroblast cells. We observe massive induction of transcriptional readthrough, both in levels and length, under all stress conditions, with significant, yet not complete, overlap of readthrough-induced loci between different conditions. Importantly, our analyses suggest that stress-induced transcriptional readthrough is not a random failure process, but is rather differentially induced across different conditions. We explore potential regulators and find a role for HSF1 in the induction of a subset of heat shock-induced readthrough transcripts. Analysis of public datasets detected increases in polymerase II occupancy in DoG regions after heat shock, supporting our findings. Interestingly, DoGs tend to be produced in the vicinity of neighboring genes, leading to a marked increase in their antisense-generating potential. Finally, we examine genomic features of readthrough transcription and observe a unique chromatin signature typical of DoG-producing regions, suggesting that readthrough transcription is associated with the maintenance of an open chromatin state.

Targeting Overexpressed Activating Transcription Factor 1 (ATF1) Inhibits Proliferation and Migration and Enhances Sensitivity to Paclitaxel In Esophageal Cancer Cells

Background

Previous reports showed that Activating Transcription Factor 1 (ATF1) plays an important role in tumor progression in a tumor-specific manner. However, little is known about the expression and role of ATF1 in esophageal cancer.

Material/Methods

The expression of ATF1 was examined by immunohistochemistry and Western blotting. The correlation between the expression of ATF1 and clinical characteristics of esophageal squamous cell carcinomas (ESCC) patients was analyzed by Fisher’s exact test. The role of cell proliferation, clonogenic survival, migration, and invasion in vitro, as well as the sensitization to paclitaxel, were determined after knockdown of ATF1 by siRNA.

Results

ATF1 was overexpressed in ESCC tissues, which was positively correlated with lymph node metastasis, poor differentiation, and early tumor invasion of esophageal cancer patients. Knockdown of ATF1 effectively reduced cell proliferation, induced S phase cell cycle arrest, and inhibited cell migration and invasion. Moreover, silencing of ATF1 significantly enhanced the sensitivity of esophageal cancer cells to paclitaxel.

Conclusions

These findings suggest that ATF1 is a promising drug target for esophageal cancer.

Bromodomain factors of BET family are new essential actors of pericentric heterochromatin transcriptional activation in response to heat shock

The heat shock response is characterized by the transcriptional activation of both hsp genes and noncoding and repeated satellite III DNA sequences located at pericentric heterochromatin. Both events are under the control of Heat Shock Factor I (HSF1). Here we show that under heat shock, HSF1 recruits major cellular acetyltransferases, GCN5, TIP60 and p300 to pericentric heterochromatin leading to a targeted hyperacetylation of pericentric chromatin. Redistribution of histone acetylation toward pericentric region in turn directs the recruitment of Bromodomain and Extra-Terminal (BET) proteins BRD2, BRD3, BRD4, which are required for satellite III transcription by RNAP II. Altogether we uncover here a critical role for HSF1 in stressed cells relying on the restricted use of histone acetylation signaling over pericentric heterochromatin (HC).

HSF1 and HSF3 cooperatively regulate the heat shock response in lizards

Cells cope with temperature elevations, which cause protein misfolding, by expressing heat shock proteins (HSPs). This adaptive response is called the heat shock response (HSR), and it is regulated mainly by heat shock transcription factor (HSF). Among the four HSF family members in vertebrates, HSF1 is a master regulator of HSP expression during proteotoxic stress including heat shock in mammals, whereas HSF3 is required for the HSR in birds. To examine whether only one of the HSF family members possesses the potential to induce the HSR in vertebrate animals, we isolated cDNA clones encoding lizard and frog HSF genes. The reconstructed phylogenetic tree of vertebrate HSFs demonstrated that HSF3 in one species is unrelated with that in other species. We found that the DNA-binding activity of both HSF1 and HSF3 in lizard and frog cells was induced in response to heat shock. Unexpectedly, overexpression of lizard and frog HSF3 as well as HSF1 induced HSP70 expression in mouse cells during heat shock, indicating that the two factors have the potential to induce the HSR. Furthermore, knockdown of either HSF3 or HSF1 markedly reduced HSP70 induction in lizard cells and resistance to heat shock. These results demonstrated that HSF1 and HSF3 cooperatively regulate the HSR at least in lizards, and suggest complex mechanisms of the HSR in lizards as well as frogs.

Metabolic control of the proteotoxic stress response: implications in diabetes mellitus and neurodegenerative disorders

Proteome homeostasis, or proteostasis, is essential to maintain cellular fitness and its disturbance is associated with a broad range of human health conditions and diseases. Cells are constantly challenged by various extrinsic and intrinsic insults, which perturb cellular proteostasis and provoke proteotoxic stress. To counter proteomic perturbations and preserve proteostasis, cells mobilize the proteotoxic stress response (PSR), an evolutionarily conserved transcriptional program mediated by heat shock factor 1 (HSF1). The HSF1-mediated PSR guards the proteome against misfolding and aggregation. In addition to proteotoxic stress, emerging studies reveal that this proteostatic mechanism also responds to cellular energy state. This regulation is mediated by the key cellular metabolic sensor AMP-activated protein kinase (AMPK). In this review, we present an overview of the maintenance of proteostasis by HSF1, the metabolic regulation of the PSR, particularly focusing on AMPK, and their implications in the two major age-related diseases-diabetes mellitus and neurodegenerative disorders.

Systematic investigation of transcription factors critical in the protection against cerebral ischemia by Danhong injection

Systematic investigations of complex pathological cascades during ischemic brain injury help to elucidate novel therapeutic targets against cerebral ischemia. Although some transcription factors (TFs) involved in cerebral ischemia, systematic surveys of their changes during ischemic brain injury have not been reported. Moreover, some multi-target agents effectively protected against ischemic stroke, but their mechanisms, especially the targets of TFs, are still unclear. Therefore, a comprehensive approach by integrating network pharmacology strategy and a new concatenated tandem array of consensus transcription factor response elements method to systematically investigate the target TFs critical in the protection against cerebral ischemia by a medication was first reported, and then applied to a multi-target drug, Danhong injection (DHI). High-throughput nature and depth of coverage, as well as high quantitative accuracy of the developed approach, make it more suitable for analyzing such multi-target agents. Results indicated that pre-B-cell leukemia transcription factor 1 and cyclic AMP-dependent transcription factor 1, along with six other TFs, are putative target TFs for DHI-mediated protection against cerebral ischemia. This study provides, for the first time, a systematic investigation of the target TFs critical to DHI-mediated protection against cerebral ischemia, as well as reveals more potential therapeutic targets for ischemic stroke.

When Cancer Fights Back: Multiple Myeloma, Proteasome Inhibition, and the Heat-Shock Response

Multiple myeloma is a plasma cell malignancy with an estimated 26,850 new cases and 11,240 deaths in 2015 in the United States. Two main classes of agents are the mainstays of therapy-proteasome inhibitors (PI) and immunomodulatory drugs (IMiD). Other new targets are emerging rapidly, including monoclonal antibodies and histone deacetylase (HDAC) inhibitors. These therapeutic options have greatly improved overall survival, but currently only 15% to 20% of patients experience long-term progression-free survival or are cured. Therefore, improvement in treatment options is needed. One potential means of improving clinical options is to target resistance mechanisms for current agents. For example, eliminating the cytoprotective heat-shock response that protects myeloma cells from proteasome inhibition may enhance PI-based therapies. The transcription factor heat-shock factor 1 (HSF1) is the master regulator of the heat-shock response. HSF1 is vital in the proteotoxic stress response, and its activation is controlled by posttranslational modifications (PTM). This review details the mechanisms of HSF1 regulation and discusses leveraging that regulation to enhance PI activity.

Mitochondrial SSBP1 protects cells from proteotoxic stresses by potentiating stress-induced HSF1 transcriptional activity

Heat-shock response is an adaptive response to proteotoxic stresses including heat shock, and is regulated by heat-shock factor 1 (HSF1) in mammals. Proteotoxic stresses challenge all subcellular compartments including the mitochondria. Therefore, there must be close connections between mitochondrial signals and the activity of HSF1. Here, we show that heat shock triggers nuclear translocation of mitochondrial SSBP1, which is involved in replication of mitochondrial DNA, in a manner dependent on the mitochondrial permeability transition pore ANT–VDAC1 complex and direct interaction with HSF1. HSF1 recruits SSBP1 to the promoters of genes encoding cytoplasmic/nuclear and mitochondrial chaperones. HSF1–SSBP1 complex then enhances their induction by facilitating the recruitment of a chromatin-remodelling factor BRG1, and supports cell survival and the maintenance of mitochondrial membrane potential against proteotoxic stresses. These results suggest that the nuclear translocation of mitochondrial SSBP1 is required for the regulation of cytoplasmic/nuclear and mitochondrial proteostasis against proteotoxic stresses.

Heat shock induces proteotoxic stress, and the cellular response is mediated by heat-shock factor 1 (HSF1). Here, Tan et al. show that following heat shock, mitochondrial SSBP1 translocates to the nucleus and binds HSF1 to enhance the expression of chaperones and support the maintenance of mitochondrial function.