Molecular Basis of the Defective Heat Stress Response in Mycobacterium leprae

ABSTRACT Mycobacterium leprae, a major human pathogen, grows poorly at 37°C. The basis for its inability to survive at elevated temperatures was investigated. We determined that M. leprae lacks a protective heat shock response as a result of the lack of transcriptional induction of the alternative sigma factor genes sigE and sigB and the major heat shock operons, HSP70 and HSP60, even though heat shock promoters and regulatory circuits for these genes appear to be intact. M. leprae sigE was found to be capable of complementing the defective heat shock response of mycobacterial sigE knockout mutants only in the presence of a functional mycobacterial sigH, which orchestrates the mycobacterial heat shock response. Since the sigH of M. leprae is a pseudogene, these data support the conclusion that a key aspect of the defective heat shock response in M. leprae is the absence of a functional sigH. In addition, 68% of the genes induced during heat shock in M. tuberculosis were shown to be either absent from the M. leprae genome or were present as pseudogenes. Among these is the hsp/acr2 gene, whose product is essential for M. tuberculosis survival during heat shock. Taken together, these results suggest that the reduced ability of M. leprae to survive at elevated temperatures results from the lack of a functional transcriptional response to heat shock and the absence of a full repertoire of heat stress response genes, including sigH.

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Caenorhabditis elegans AF4/FMR2 Family Homolog affl-2 Regulates Heat-Shock-Induced Gene Expression

Genetics ◽

10.1534/genetics.120.302923 ◽

2020 ◽

Vol 215 (4) ◽

pp. 1039-1054

Author(s):

Sophie J. Walton ◽

Han Wang ◽

Porfirio Quintero-Cadena ◽

Alex Bateman ◽

Paul W. Sternberg

Keyword(s):

Gene Expression ◽

Heat Stress ◽

Caenorhabditis Elegans ◽

Heat Shock ◽

Heat Shock Response ◽

Genetic Locus ◽

Transcriptional Response ◽

Transcriptional Elongation ◽

Link Type ◽

Shock Response

To mitigate the deleterious effects of temperature increases on cellular organization and proteotoxicity, organisms have developed mechanisms to respond to heat stress. In eukaryotes, HSF1 is the master regulator of the heat shock transcriptional response, but the heat shock response pathway is not yet fully understood. From a forward genetic screen for suppressors of heat-shock-induced gene expression in Caenorhabditis elegans, we found a new allele of hsf-1 that alters its DNA-binding domain, and we found three additional alleles of sup-45, a previously molecularly uncharacterized genetic locus. We identified sup-45 as one of the two hitherto unknown C. elegans orthologs of the human AF4/FMR2 family proteins, which are involved in regulation of transcriptional elongation rate. We thus renamed sup-45 as affl-2 (AF4/FMR2-Like). Through RNA-seq, we demonstrated that affl-2 mutants are deficient in heat-shock-induced transcription. Additionally, affl-2 mutants have herniated intestines, while worms lacking its sole paralog (affl-1) appear wild type. AFFL-2 is a broadly expressed nuclear protein, and nuclear localization of AFFL-2 is necessary for its role in heat shock response. affl-2 and its paralog are not essential for proper HSF-1 expression and localization after heat shock, which suggests that affl-2 may function downstream of, or parallel to, hsf-1. Our characterization of affl-2 provides insights into the regulation of heat-shock-induced gene expression to protect against heat stress.

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Caenorhabditis elegans AF4/FMR2 family homolog affl-2 is required for heat shock induced gene expression

10.1101/817833 ◽

2019 ◽

Author(s):

Sophie J. Walton ◽

Han Wang ◽

Porfirio Quintero-Cadena ◽

Alex Bateman ◽

Paul W. Sternberg

Keyword(s):

Gene Expression ◽

Heat Stress ◽

Heat Shock ◽

Heat Shock Response ◽

Genetic Locus ◽

Transcriptional Response ◽

Egg Laying ◽

Transcriptional Elongation ◽

C Elegans ◽

Shock Response

AbstractTo mitigate the deleterious effects of temperature increases on cellular organization and proteotoxicity, organisms have developed mechanisms to respond to heat stress. In eukaryotes, HSF1 is the master regulator of the heat shock transcriptional response, but the heat shock response pathway is not yet fully understood. From a forward genetic screen for suppressors of heat shock induced gene expression in C. elegans, we identified a new allele of hsf-1 that alters its DNA-binding domain, and three additional alleles of sup-45, a previously uncharacterized genetic locus. We identified sup-45 as one of the two hitherto unknown C. elegans orthologs of the human AF4/FMR2 family proteins, which are involved in regulation of transcriptional elongation rate. We thus renamed sup-45 as affl-2 (AF4/FMR2-Like). affl-2 mutants are egg-laying defective and dumpy, but worms lacking its sole paralog (affl-1) appear wild-type. AFFL-2 is a broadly expressed nuclear protein, and nuclear localization of AFFL-2 is necessary for its role in heat shock response. affl-2 and its paralog are not essential for proper HSF-1 expression and localization after heat shock, which suggests that affl-2 may function downstream or parallel of hsf-1. Our characterization of affl-2 provides insights into the complex processes of transcriptional elongation and regulating heat shock induced gene expression to protect against heat stress.

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Conventional and novel PKC isoenzymes modify the heat-induced stress response but are not activated by heat shock

Journal of Cell Science ◽

10.1242/jcs.111.22.3357 ◽

1998 ◽

Vol 111 (22) ◽

pp. 3357-3365 ◽

Cited By ~ 1

Author(s):

C.I. Holmberg ◽

P.M. Roos ◽

J.M. Lord ◽

J.E. Eriksson ◽

L. Sistonen

Keyword(s):

Stress Response ◽

Heat Shock ◽

Heat Shock Response ◽

Mammalian Cells ◽

Elevated Temperatures ◽

Heat Shock Element ◽

Post Translational Modifications ◽

Induced Stress ◽

Shock Response

In mammalian cells, the heat-induced stress response is mediated by the constitutively expressed heat shock transcription factor 1 (HSF1). Upon exposure to elevated temperatures, HSF1 undergoes several post-translational modifications, including inducible phosphorylation or hyperphosphorylation. To date, neither the role of HSF1 hyperphosphorylation in regulation of the transcriptional activity of HSF1 nor the signaling pathways involved have been characterized. We have previously shown that the protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol 13-acetate (TPA), markedly enhances the heat-induced stress response, and in the present study we elucidate the mechanism by which PKC activation affects the heat shock response in human cells. Our results show that several conventional and novel PKC isoenzymes are activated during the TPA-mediated enhancement of the heat shock response and that the enhancement can be inhibited by the specific PKC inhibitor bisindolylmaleimide I. Furthermore, the potentiating effect of TPA on the heat-induced stress response requires an intact heat shock element in the hsp70 promoter, indicating that PKC-responsive pathways are able to modulate the activity of HSF1. We also demonstrate that PKC is not activated by heat stress per se. These results reveal that PKC exhibits a significant modulatory role of the heat-induced stress response, but is not directly involved in regulation of the heat shock response.

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Large organellar changes occur during mild heat shock in yeast

Journal of Cell Science ◽

10.1242/jcs.258325 ◽

2021 ◽

Author(s):

Katharina S Keuenhof ◽

Lisa Larsson Berglund ◽

Sandra Malmgren Hill ◽

Kara L Schneider ◽

Per O Widlund ◽

...

Keyword(s):

Electron Microscopy ◽

Heat Stress ◽

Heat Shock ◽

Heat Shock Response ◽

Multivesicular Bodies ◽

Heat Stress Response ◽

Cellular Environment ◽

Shock Response ◽

Continuous Heat ◽

Internal Architecture

When the temperature is increased, the heat shock response is activated to protect the cellular environment. The transcriptomics and proteomics of this process are intensively studied, while information about how the cell responds structurally to heat stress is mostly lacking. Here, Saccharomyces cerevisiae were subjected to a mild continuous heat shock (38°C) and intermittently cryo-immobilized for electron microscopy. Through measuring changes in all distinguishable organelle numbers, sizes, and morphologies in over 2100 electron micrographs a major restructuring of the cell's internal architecture during the progressive heat shock was revealed. The cell grew larger but most organelles within it expanded even more, shrinking the volume of the cytoplasm. Organelles responded to heat shock at different times, both in terms of size and number, and adaptations of certain organelles’ morphology (such as the vacuole), were observed. Multivesicular bodies grew to almost 170% in size, indicating a previously unknown involvement in the heat shock response. A previously undescribed electron translucent structure accumulated close to the plasma membrane. This all-encompassing approach provides a detailed chronological progression of organelle adaptation throughout the cellular heat-stress response.

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Genome-wide identification and analysis of the heat shock transcription factor family in moso bamboo (Phyllostachys edulis)

Scientific Reports ◽

10.1038/s41598-021-95899-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bin Huang ◽

Zhinuo Huang ◽

Ruifang Ma ◽

Jialu Chen ◽

Zhijun Zhang ◽

...

Keyword(s):

Heat Stress ◽

Stress Response ◽

Heat Shock ◽

Gene Family ◽

Regulatory Elements ◽

Moso Bamboo ◽

Naphthalene Acetic Acid ◽

Plant Responses ◽

Heat Stress Response ◽

Regulatory Pathways

AbstractHeat shock transcription factors (HSFs) are central elements in the regulatory network that controls plant heat stress response. They are involved in multiple transcriptional regulatory pathways and play important roles in heat stress signaling and responses to a variety of other stresses. We identified 41 members of the HSF gene family in moso bamboo, which were distributed non-uniformly across its 19 chromosomes. Phylogenetic analysis showed that the moso bamboo HSF genes could be divided into three major subfamilies; HSFs from the same subfamily shared relatively conserved gene structures and sequences and encoded similar amino acids. All HSF genes contained HSF signature domains. Subcellular localization prediction indicated that about 80% of the HSF proteins were located in the nucleus, consistent with the results of GO enrichment analysis. A large number of stress response–associated cis-regulatory elements were identified in the HSF upstream promoter sequences. Synteny analysis indicated that the HSFs in the moso bamboo genome had greater collinearity with those of rice and maize than with those of Arabidopsis and pepper. Numerous segmental duplicates were found in the moso bamboo HSF gene family. Transcriptome data indicated that the expression of a number of PeHsfs differed in response to exogenous gibberellin (GA) and naphthalene acetic acid (NAA). A number of HSF genes were highly expressed in the panicles and in young shoots, suggesting that they may have functions in reproductive growth and the early development of rapidly-growing shoots. This study provides fundamental information on members of the bamboo HSF gene family and lays a foundation for further study of their biological functions in the regulation of plant responses to adversity.

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Mitochondrial activity and heat-shock response during morphogenesis in the pathogenic fungus Histoplasma capsulatum

Biochemistry and Cell Biology ◽

10.1139/o92-031 ◽

1992 ◽

Vol 70 (3-4) ◽

pp. 207-214 ◽

Cited By ~ 17

Author(s):

Eduardo J. Patriarca ◽

George S. Kobayashi ◽

Bruno Maresca

Keyword(s):

Heat Shock ◽

Heat Shock Response ◽

Elevated Temperatures ◽

Histoplasma Capsulatum ◽

Pathogenic Fungus ◽

Temperature Shift ◽

Mitochondrial Activity ◽

Mitochondrial Atpase ◽

Heat Shock Genes ◽

Shock Response

Changes in temperature and a variety of other stimuli coordinately induce transcription of a specific set of heat-shock genes in all organisms. In the human fungal pathogen Histoplasma capsulatum, a temperature shift from 25 to 37 °C acts not only as a signal that causes transcription of heat-shock genes, but also triggers a morphological mycelium-to yeast-phase transition. The temperature-induced morphological transition may be viewed as a heat-shock response followed by cellular adaptation to a higher temperature. We have found that by inducing thermotolerance, i.e., an initial incubation at 34 °C, the thermosensitive attenuated Downs strain of H. capsulatum can be made to resemble those of the more temperature-tolerant G222B strain with respect to mitochondrial ATPase activity and electron transport efficiency at elevated temperatures. Furthermore, if the heat-shock response is first elicited by preincubation at milder temperatures or stress, transcription of heat-shock mRNA in mycelial cells of Downs strain that shifted to 37 °C proceeds at rates comparable to those of the virulent strains.Key words: heat shock, thermotolerance, ATPase, 70-kilodalton heat-shock protein, fungal morphogenesis.

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