RESUMO
Protein folding in the cell is mediated by an extensive network of >1,000 chaperones, quality control factors, and trafficking mechanisms collectively termed the proteostasis network. While the components and organization of this network are generally well established, our understanding of how protein-folding problems are identified, how the network components integrate to successfully address challenges, and what types of biophysical issues each proteostasis network component is capable of addressing remains immature. We describe a chemical biology-informed framework for studying cellular proteostasis that relies on selection of interesting protein-folding problems and precise researcher control of proteostasis network composition and activities. By combining these methods with multifaceted strategies to monitor protein folding, degradation, trafficking, and aggregation in cells, researchers continue to rapidly generate new insights into cellular proteostasis.
Assuntos
Chaperonas Moleculares/genética , Técnicas de Sonda Molecular , Proteoma/genética , Deficiências na Proteostase/genética , Proteostase/genética , Animais , Sistemas CRISPR-Cas , Regulação da Expressão Gênica , Meia-Vida , Resposta ao Choque Térmico/efeitos dos fármacos , Humanos , Chaperonas Moleculares/metabolismo , Agregados Proteicos , Engenharia de Proteínas/métodos , Dobramento de Proteína/efeitos dos fármacos , Transporte Proteico/efeitos dos fármacos , Proteoma/química , Proteoma/metabolismo , Proteostase/efeitos dos fármacos , Deficiências na Proteostase/metabolismo , Deficiências na Proteostase/patologia , Transdução de Sinais , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/farmacologia , Resposta a Proteínas não Dobradas/efeitos dos fármacosRESUMO
Cells sense elevated temperatures and mount an adaptive heat shock response that involves changes in gene expression, but the underlying mechanisms, particularly on the level of translation, remain unknown. Here we report that, in budding yeast, the essential translation initiation factor Ded1p undergoes heat-induced phase separation into gel-like condensates. Using ribosome profiling and an in vitro translation assay, we reveal that condensate formation inactivates Ded1p and represses translation of housekeeping mRNAs while promoting translation of stress mRNAs. Testing a variant of Ded1p with altered phase behavior as well as Ded1p homologs from diverse species, we demonstrate that Ded1p condensation is adaptive and fine-tuned to the maximum growth temperature of the respective organism. We conclude that Ded1p condensation is an integral part of an extended heat shock response that selectively represses translation of housekeeping mRNAs to promote survival under conditions of severe heat stress.
Assuntos
RNA Helicases DEAD-box/metabolismo , Regulação Fúngica da Expressão Gênica/genética , Biossíntese de Proteínas/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , RNA Helicases DEAD-box/fisiologia , Expressão Gênica/genética , Genes Essenciais/genética , Proteínas de Choque Térmico/metabolismo , Resposta ao Choque Térmico/genética , RNA Mensageiro/metabolismo , Ribossomos/metabolismo , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/fisiologiaRESUMO
The super elongation complex (SEC) is required for robust and productive transcription through release of RNA polymerase II (Pol II) with its P-TEFb module and promoting transcriptional processivity with its ELL2 subunit. Malfunction of SEC contributes to multiple human diseases including cancer. Here, we identify peptidomimetic lead compounds, KL-1 and its structural homolog KL-2, which disrupt the interaction between the SEC scaffolding protein AFF4 and P-TEFb, resulting in impaired release of Pol II from promoter-proximal pause sites and a reduced average rate of processive transcription elongation. SEC is required for induction of heat-shock genes and treating cells with KL-1 and KL-2 attenuates the heat-shock response from Drosophila to human. SEC inhibition downregulates MYC and MYC-dependent transcriptional programs in mammalian cells and delays tumor progression in a mouse xenograft model of MYC-driven cancer, indicating that small-molecule disruptors of SEC could be used for targeted therapy of MYC-induced cancer.
Assuntos
Antineoplásicos/farmacologia , Neoplasias Experimentais/tratamento farmacológico , Fator B de Elongação Transcricional Positiva/metabolismo , Proteínas Repressoras/metabolismo , Elongação da Transcrição Genética/efeitos dos fármacos , Fatores de Elongação da Transcrição/metabolismo , Animais , Antineoplásicos/química , Antineoplásicos/uso terapêutico , Drosophila , Feminino , Células HCT116 , Células HEK293 , Resposta ao Choque Térmico , Humanos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Ligação Proteica/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-myc/genética , Proteínas Proto-Oncogênicas c-myc/metabolismo , RNA Polimerase II/metabolismo , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/farmacologiaRESUMO
Cellular homeostasis is constantly challenged by a myriad of extrinsic and intrinsic stressors. To mitigate the stress-induced damage, cells activate transient survival programs. The heat shock response (HSR) is an evolutionarily well-conserved survival program that is activated in response to proteotoxic stress. The HSR encompasses a dual regulation of transcription, characterized by rapid activation of genes encoding molecular chaperones and concomitant global attenuation of non-chaperone genes. Recent genome-wide approaches have delineated the molecular depth of stress-induced transcriptional reprogramming. The dramatic rewiring of gene and enhancer networks is driven by key transcription factors, including heat shock factors (HSFs), that together with chromatin-modifying enzymes remodel the 3D chromatin architecture, determining the selection of either gene activation or repression. Here, we highlight the current advancements of molecular mechanisms driving transcriptional reprogramming during acute heat stress. We also discuss the emerging implications of HSF-mediated stress signaling in the context of physiological and pathological conditions.
Assuntos
Proteostase , Fatores de Transcrição , Proteostase/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Resposta ao Choque Térmico/genética , Chaperonas Moleculares/genética , Cromatina/genética , Fatores de Transcrição de Choque Térmico/genética , Fatores de Transcrição de Choque Térmico/metabolismoRESUMO
The heat shock response is crucial for cell survival. In this issue of Molecular Cell, Desroches Altamirano et al.1 demonstrate that a temperature-induced conformational change in the translation initiation factor eIF4G is a key mechanism regulating translation during the heat shock response.
Assuntos
Fator de Iniciação Eucariótico 4G , Resposta ao Choque Térmico , Biossíntese de Proteínas , RNA Mensageiro , Fator de Iniciação Eucariótico 4G/metabolismo , Fator de Iniciação Eucariótico 4G/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Humanos , Animais , Conformação Proteica , Proteínas de Choque Térmico/metabolismo , Proteínas de Choque Térmico/genéticaRESUMO
Stress granules (SGs) are conserved reversible cytoplasmic condensates enriched with aggregation-prone proteins assembled in response to various stresses. How plants regulate SG dynamics is unclear. Here, we show that 26S proteasome is a stable component of SGs, promoting the overall clearance of SGs without affecting the molecular mobility of SG components. Increase in either temperature or duration of heat stress reduces the molecular mobility of SG marker proteins and suppresses SG clearance. Heat stress induces dramatic ubiquitylation of SG components and enhances the activities of SG-resident proteasomes, allowing the degradation of SG components even during the assembly phase. Their proteolytic activities enable the timely disassembly of SGs and secure the survival of plant cells during the recovery from heat stress. Therefore, our findings identify the cellular process that de-couples macroscopic dynamics of SGs from the molecular dynamics of its constituents and highlights the significance of the proteasomes in SG disassembly.
Assuntos
Arabidopsis , Resposta ao Choque Térmico , Complexo de Endopeptidases do Proteassoma , Ubiquitinação , Complexo de Endopeptidases do Proteassoma/metabolismo , Complexo de Endopeptidases do Proteassoma/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Arabidopsis/enzimologia , Proteólise , Grânulos de Estresse/metabolismo , Grânulos de Estresse/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Grânulos Citoplasmáticos/metabolismoRESUMO
Heat-shocked cells prioritize the translation of heat shock (HS) mRNAs, but the underlying mechanism is unclear. We report that HS in budding yeast induces the disassembly of the eIF4F complex, where eIF4G and eIF4E assemble into translationally arrested mRNA ribonucleoprotein particles (mRNPs) and HS granules (HSGs), whereas eIF4A promotes HS translation. Using in vitro reconstitution biochemistry, we show that a conformational rearrangement of the thermo-sensing eIF4A-binding domain of eIF4G dissociates eIF4A and promotes the assembly with mRNA into HS-mRNPs, which recruit additional translation factors, including Pab1p and eIF4E, to form multi-component condensates. Using extracts and cellular experiments, we demonstrate that HS-mRNPs and condensates repress the translation of associated mRNA and deplete translation factors that are required for housekeeping translation, whereas HS mRNAs can be efficiently translated by eIF4A. We conclude that the eIF4F complex is a thermo-sensing node that regulates translation during HS.
Assuntos
Fator de Iniciação 4F em Eucariotos , Fator de Iniciação Eucariótico 4G , Resposta ao Choque Térmico , Proteínas de Ligação a Poli(A) , Biossíntese de Proteínas , RNA Mensageiro , Ribonucleoproteínas , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Resposta ao Choque Térmico/genética , Fator de Iniciação 4F em Eucariotos/metabolismo , Fator de Iniciação 4F em Eucariotos/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Fator de Iniciação Eucariótico 4G/metabolismo , Fator de Iniciação Eucariótico 4G/genética , Ribonucleoproteínas/metabolismo , Ribonucleoproteínas/genética , Fator de Iniciação 4E em Eucariotos/metabolismo , Fator de Iniciação 4E em Eucariotos/genética , Fator de Iniciação 4A em Eucariotos/metabolismo , Fator de Iniciação 4A em Eucariotos/genética , Regulação Fúngica da Expressão Gênica , Ligação Proteica , RNA Fúngico/metabolismo , RNA Fúngico/genéticaRESUMO
RNA polymerase II (RNA Pol II)-mediated transcription is a critical, highly regulated process aided by protein complexes at distinct steps. Here, to investigate RNA Pol II and transcription-factor-binding and dissociation dynamics, we generated endogenous photoactivatable-GFP (PA-GFP) and HaloTag knockins using CRISPR-Cas9, allowing us to track a population of molecules at the induced Hsp70 loci in Drosophila melanogaster polytene chromosomes. We found that early in the heat-shock response, little RNA Pol II and DRB sensitivity-inducing factor (DSIF) are reused for iterative rounds of transcription. Surprisingly, although PAF1 and Spt6 are found throughout the gene body by chromatin immunoprecipitation (ChIP) assays, they show markedly different binding behaviors. Additionally, we found that PAF1 and Spt6 are only recruited after positive transcription elongation factor (P-TEFb)-mediated phosphorylation and RNA Pol II promoter-proximal pause escape. Finally, we observed that PAF1 may be expendable for transcription of highly expressed genes where nucleosome density is low. Thus, our live-cell imaging data provide key constraints to mechanistic models of transcription regulation.
Assuntos
Proteínas de Drosophila , Drosophila melanogaster , RNA Polimerase II , Transcrição Gênica , Fatores de Elongação da Transcrição , RNA Polimerase II/metabolismo , RNA Polimerase II/genética , Animais , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Fatores de Elongação da Transcrição/metabolismo , Fatores de Elongação da Transcrição/genética , Proteínas de Choque Térmico HSP70/metabolismo , Proteínas de Choque Térmico HSP70/genética , Fator B de Elongação Transcricional Positiva/metabolismo , Fator B de Elongação Transcricional Positiva/genética , Regiões Promotoras Genéticas , Sistemas CRISPR-Cas , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Cromossomos Politênicos/genética , Cromossomos Politênicos/metabolismo , Regulação da Expressão Gênica , Fosforilação , Ligação Proteica , Resposta ao Choque Térmico/genética , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Nucleossomos/metabolismo , Nucleossomos/genéticaRESUMO
While we are beginning to appreciate the cellular roles played by long noncoding RNAs, the function of transcripts emerging from repetitive genomic regions remains enigmatic. In this issue, Zovoilis et al. report that the polycomb protein EZH2, upon heat shock, facilitates transcription of stress-responsive genes by inducing the degradation of the transcriptional repressor B2 repeat RNA.
Assuntos
Proteínas do Grupo Polycomb , RNA Longo não Codificante , Genoma , Resposta ao Choque Térmico , Complexo Repressor Polycomb 2RESUMO
More than 98% of the mammalian genome is noncoding, and interspersed transposable elements account for â¼50% of noncoding space. Here, we demonstrate that a specific interaction between the polycomb protein EZH2 and RNA made from B2 SINE retrotransposons controls stress-responsive genes in mouse cells. In the heat-shock model, B2 RNA binds stress genes and suppresses their transcription. Upon stress, EZH2 is recruited and triggers cleavage of B2 RNA. B2 degradation in turn upregulates stress genes. Evidence indicates that B2 RNA operates as a "speed bump" against advancement of RNA polymerase II, and temperature stress releases the brakes on transcriptional elongation. These data attribute a new function to EZH2 that is independent of its histone methyltransferase activity and reconcile how EZH2 can be associated with both gene repression and activation. Our study reveals that EZH2 and B2 together control activation of a large network of genes involved in thermal stress.
Assuntos
Proteína Potenciadora do Homólogo 2 de Zeste/metabolismo , Regulação da Expressão Gênica , Resposta ao Choque Térmico , RNA não Traduzido/metabolismo , Retroelementos , Animais , Células-Tronco Embrionárias/metabolismo , Camundongos , Células NIH 3T3 , RNA Polimerase II/metabolismo , Transcrição GênicaRESUMO
Defects in mitochondrial metabolism have been increasingly linked with age-onset protein-misfolding diseases such as Alzheimer's, Parkinson's, and Huntington's. In response to protein-folding stress, compartment-specific unfolded protein responses (UPRs) within the ER, mitochondria, and cytosol work in parallel to ensure cellular protein homeostasis. While perturbation of individual compartments can make other compartments more susceptible to protein stress, the cellular conditions that trigger cross-communication between the individual UPRs remain poorly understood. We have uncovered a conserved, robust mechanism linking mitochondrial protein homeostasis and the cytosolic folding environment through changes in lipid homeostasis. Metabolic restructuring caused by mitochondrial stress or small-molecule activators trigger changes in gene expression coordinated uniquely by both the mitochondrial and cytosolic UPRs, protecting the cell from disease-associated proteins. Our data suggest an intricate and unique system of communication between UPRs in response to metabolic changes that could unveil new targets for diseases of protein misfolding.
Assuntos
Citosol/fisiologia , Resposta ao Choque Térmico/fisiologia , Lipídeos/biossíntese , Mitocôndrias/fisiologia , Resposta a Proteínas não Dobradas/fisiologia , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Linhagem Celular , Regulação da Expressão Gênica , Técnicas de Silenciamento de Genes , Proteínas de Choque Térmico/genética , Homeostase , Humanos , Metabolismo dos Lipídeos/genética , Proteínas Mitocondriais/metabolismo , Chaperonas Moleculares/genética , Dobramento de ProteínaRESUMO
As sessile organisms, plants must cope with abiotic stress such as soil salinity, drought, and extreme temperatures. Core stress-signaling pathways involve protein kinases related to the yeast SNF1 and mammalian AMPK, suggesting that stress signaling in plants evolved from energy sensing. Stress signaling regulates proteins critical for ion and water transport and for metabolic and gene-expression reprogramming to bring about ionic and water homeostasis and cellular stability under stress conditions. Understanding stress signaling and responses will increase our ability to improve stress resistance in crops to achieve agricultural sustainability and food security for a growing world population.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Produtos Agrícolas/fisiologia , Proteínas Serina-Treonina Quinases/metabolismo , Estresse Fisiológico/fisiologia , Proteínas Quinases Ativadas por AMP/genética , Cloroplastos/enzimologia , Resposta ao Choque Frio , Produtos Agrícolas/enzimologia , Produtos Agrícolas/genética , Secas , Estresse do Retículo Endoplasmático , Metabolismo Energético , Abastecimento de Alimentos , Regulação da Expressão Gênica de Plantas , Resposta ao Choque Térmico , Mitocôndrias/enzimologia , Pressão Osmótica , Peroxissomos/enzimologia , Proteínas Serina-Treonina Quinases/genética , Salinidade , Transdução de Sinais , Estresse Fisiológico/genéticaRESUMO
Eusocial insect reproductive females show strikingly longer life spans than nonreproductive female workers despite high genetic similarity. In the ant Harpegnathos saltator (Hsal), workers can transition to reproductive "gamergates," acquiring a fivefold prolonged life span by mechanisms that are poorly understood. We found that gamergates have elevated expression of heat shock response (HSR) genes in the absence of heat stress and enhanced survival with heat stress. This HSR gene elevation is driven in part by gamergate-specific up-regulation of the gene encoding a truncated form of a heat shock factor most similar to mammalian HSF2 (hsalHSF2). In workers, hsalHSF2 was bound to DNA only upon heat stress. In gamergates, hsalHSF2 bound to DNA even in the absence of heat stress and was localized to gamergate-biased HSR genes. Expression of hsalHSF2 in Drosophila melanogaster led to enhanced heat shock survival and extended life span in the absence of heat stress. Molecular characterization illuminated multiple parallels between long-lived flies and gamergates, underscoring the centrality of hsalHSF2 to extended ant life span. Hence, ant caste-specific heat stress resilience and extended longevity can be transferred to flies via hsalHSF2. These findings reinforce the critical role of proteostasis in health and aging and reveal novel mechanisms underlying facultative life span extension in ants.
Assuntos
Formigas , Longevidade , Animais , Feminino , Longevidade/genética , Formigas/genética , Drosophila melanogaster/genética , Envelhecimento , Resposta ao Choque Térmico/genética , MamíferosRESUMO
The heat shock transcription factors (HSFs) were discovered over 30 years ago as direct transcriptional activators of genes regulated by thermal stress, encoding heat shock proteins. The accepted paradigm posited that HSFs exclusively activate the expression of protein chaperones in response to conditions that cause protein misfolding by recognizing a simple promoter binding site referred to as a heat shock element. However, we now realize that the mammalian family of HSFs comprises proteins that independently or in concert drive combinatorial gene regulation events that activate or repress transcription in different contexts. Advances in our understanding of HSF structure, post-translational modifications and the breadth of HSF-regulated target genes have revealed exciting new mechanisms that modulate HSFs and shed new light on their roles in physiology and pathology. For example, the ability of HSF1 to protect cells from proteotoxicity and cell death is impaired in neurodegenerative diseases but can be exploited by cancer cells to support their growth, survival and metastasis. These new insights into HSF structure, function and regulation should facilitate the development tof new disease therapeutics to manipulate this transcription factor family.
Assuntos
Regulação da Expressão Gênica/genética , Fatores de Transcrição de Choque Térmico/genética , Proteínas de Choque Térmico/genética , Transcrição Gênica/genética , Animais , Resposta ao Choque Térmico/genética , Humanos , Processamento de Proteína Pós-Traducional/genéticaRESUMO
Heat causes protein misfolding and aggregation and, in eukaryotic cells, triggers aggregation of proteins and RNA into stress granules. We have carried out extensive proteomic studies to quantify heat-triggered aggregation and subsequent disaggregation in budding yeast, identifying >170 endogenous proteins aggregating within minutes of heat shock in multiple subcellular compartments. We demonstrate that these aggregated proteins are not misfolded and destined for degradation. Stable-isotope labeling reveals that even severely aggregated endogenous proteins are disaggregated without degradation during recovery from shock, contrasting with the rapid degradation observed for many exogenous thermolabile proteins. Although aggregation likely inactivates many cellular proteins, in the case of a heterotrimeric aminoacyl-tRNA synthetase complex, the aggregated proteins remain active with unaltered fidelity. We propose that most heat-induced aggregation of mature proteins reflects the operation of an adaptive, autoregulatory process of functionally significant aggregate assembly and disassembly that aids cellular adaptation to thermal stress.
Assuntos
Resposta ao Choque Térmico , Saccharomyces cerevisiae/citologia , Saccharomyces cerevisiae/fisiologia , Cicloeximida/farmacologia , Grânulos Citoplasmáticos/metabolismo , Agregados Proteicos , Biossíntese de Proteínas/efeitos dos fármacos , Inibidores da Síntese de Proteínas/farmacologia , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/metabolismoRESUMO
Mammalian developmental and disease-associated genes concentrate large quantities of the transcriptional machinery by forming membrane-less compartments known as transcriptional condensates. However, it is unknown whether these structures are evolutionarily conserved or involved in 3D genome reorganization. Here, we identify inducible transcriptional condensates in the yeast heat shock response (HSR). HSR condensates are biophysically dynamic spatiotemporal clusters of the sequence-specific transcription factor heat shock factor 1 (Hsf1) with Mediator and RNA Pol II. Uniquely, HSR condensates drive the coalescence of multiple Hsf1 target genes, even those located on different chromosomes. Binding of the chaperone Hsp70 to a site on Hsf1 represses clustering, whereas an intrinsically disordered region on Hsf1 promotes condensate formation and intergenic interactions. Mutation of both Hsf1 determinants reprograms HSR condensates to become constitutively active without intergenic coalescence, which comes at a fitness cost. These results suggest that transcriptional condensates are ancient and flexible compartments of eukaryotic gene control.
Assuntos
Resposta ao Choque Térmico , Corpos Nucleares , Animais , Resposta ao Choque Térmico/genética , Proteínas de Choque Térmico HSP70/genética , Mamíferos , RNA Polimerase II/genética , Saccharomyces cerevisiae/genética , GenomaRESUMO
The heat shock (HS) response involves rapid induction of HS genes, whereas transcriptional repression is established more slowly at most other genes. Previous data suggested that such repression results from inhibition of RNA polymerase II (RNAPII) pause release, but here, we show that HS strongly affects other phases of the transcription cycle. Intriguingly, while elongation rates increase upon HS, processivity markedly decreases, so that RNAPII frequently fails to reach the end of genes. Indeed, HS results in widespread premature transcript termination at cryptic, intronic polyadenylation (IPA) sites near gene 5'-ends, likely via inhibition of U1 telescripting. This results in dramatic reconfiguration of the human transcriptome with production of new, previously unannotated, short mRNAs that accumulate in the nucleus. Together, these results shed new light on the basic transcription mechanisms induced by growth at elevated temperature and show that a genome-wide shift toward usage of IPA sites can occur under physiological conditions.
Assuntos
Poliadenilação , Transcriptoma , Resposta ao Choque Térmico/genética , Humanos , RNA Polimerase II/genética , RNA Polimerase II/metabolismo , RNA Mensageiro/genéticaRESUMO
It is unclear how various factors functioning in the transcriptional elongation by RNA polymerase II (RNA Pol II) cooperatively regulate pause/release and productive elongation in living cells. Using an acute protein-depletion approach, we report that SPT6 depletion results in the release of paused RNA Pol II into gene bodies through an impaired recruitment of PAF1C. Short genes demonstrate a release with increased mature transcripts, whereas long genes are released but fail to yield mature transcripts, due to a reduced processivity resulting from both SPT6 and PAF1C loss. Unexpectedly, SPT6 depletion causes an association of NELF with the elongating RNA Pol II on gene bodies, without any observed functional significance on transcriptional elongation pattern, arguing against a role for NELF in keeping RNA Pol II in the paused state. Furthermore, SPT6 depletion impairs heat-shock-induced pausing, pointing to a role for SPT6 in regulating RNA Pol II pause/release through PAF1C recruitment.
Assuntos
RNA Polimerase II , Fatores de Transcrição , Resposta ao Choque Térmico , Regiões Promotoras Genéticas , RNA Polimerase II/genética , RNA Polimerase II/metabolismo , Fatores de Transcrição/genética , Transcrição GênicaRESUMO
Stresses such as heat shock trigger the formation of protein aggregates and the induction of a disaggregation system composed of molecular chaperones. Recent work reveals that several cases of apparent heat-induced aggregation, long thought to be the result of toxic misfolding, instead reflect evolved, adaptive biomolecular condensation, with chaperone activity contributing to condensate regulation. Here we show that the yeast disaggregation system directly disperses heat-induced biomolecular condensates of endogenous poly(A)-binding protein (Pab1) orders of magnitude more rapidly than aggregates of the most commonly used misfolded model substrate, firefly luciferase. Beyond its efficiency, heat-induced condensate dispersal differs from heat-induced aggregate dispersal in its molecular requirements and mechanistic behavior. Our work establishes a bona fide endogenous heat-induced substrate for long-studied heat shock proteins, isolates a specific example of chaperone regulation of condensates, and underscores needed expansion of the proteotoxic interpretation of the heat shock response to encompass adaptive, chaperone-mediated regulation.
Assuntos
Condensados Biomoleculares/metabolismo , Proteínas de Choque Térmico HSP40/metabolismo , Proteínas de Choque Térmico HSP70/metabolismo , Proteínas de Choque Térmico/metabolismo , Resposta ao Choque Térmico , Proteínas de Ligação a Poli(A)/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Ligação Competitiva , Condensados Biomoleculares/genética , Proteínas de Choque Térmico HSP40/genética , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico/genética , Proteínas de Ligação a Poli(A)/genética , Agregados Proteicos , Ligação Proteica , Dobramento de Proteína , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genéticaRESUMO
The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed to study the physiological regulation of deep body temperature. This review focuses on healthy and disordered human temperature regulation during heat stress. Central to this discussion is the notion that various morphological features, intrinsic factors, diseases, and injuries independently and interactively influence deep body temperature during exercise and/or exposure to hot ambient temperatures. The first sections review fundamental aspects of the human heat stress response, including the biophysical principles governing heat balance and the autonomic control of heat loss thermoeffectors. Next, we discuss the effects of different intrinsic factors (morphology, heat adaptation, biological sex, and age), diseases (neurological, cardiovascular, metabolic, and genetic), and injuries (spinal cord injury, deep burns, and heat stroke), with emphasis on the mechanisms by which these factors enhance or disturb the regulation of deep body temperature during heat stress. We conclude with key unanswered questions in this field of research.