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Mammalian Heat Shock Response and Mechanisms Underlying Its Genome-wide Transcriptional Regulation.

ABSTRACT: The heat shock response (HSR) is critical for survival of all organisms. However, its scope, extent, and the molecular mechanism of regulation are poorly understood. Here we show that the genome-wide transcriptional response to heat shock in mammals is rapid and dynamic and results in induction of several hundred and repression of several thousand genes. Heat shock factor 1 (HSF1), the "master regulator" of the HSR, controls only a fraction of heat shock-induced genes and does so by increasing RNA polymerase II release from promoter-proximal pause. Notably, HSF2 does not compensate for the lack of HSF1. However, serum response factor appears to transiently induce cytoskeletal genes independently of HSF1. The pervasive repression of transcription is predominantly HSF1-independent and is mediated through reduction of RNA polymerase II pause release. Overall, mammalian cells orchestrate rapid, dynamic, and extensive changes in transcription upon heat shock that are largely modulated at pause release, and HSF1 plays a limited and specialized role.

SUBMITTER: Mahat DB

PROVIDER: S-EPMC4826300 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Mammalian Heat Shock Response and Mechanisms Underlying Its Genome-wide Transcriptional Regulation.

Mahat Dig B DB Salamanca H Hans HH Duarte Fabiana M FM Danko Charles G CG Lis John T JT

Molecular cell 20160324 1

The heat shock response (HSR) is critical for survival of all organisms. However, its scope, extent, and the molecular mechanism of regulation are poorly understood. Here we show that the genome-wide transcriptional response to heat shock in mammals is rapid and dynamic and results in induction of several hundred and repression of several thousand genes. Heat shock factor 1 (HSF1), the "master regulator" of the HSR, controls only a fraction of heat shock-induced genes and does so by increasing R ...[more]

PMID: 27052732

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Project description:Heat shock response (HSR) is critical for survival of organisms undergoing proteotoxic stress. Heat shock factor 1 (HSF1) is widely believed to be the master regulator of this response. Here, we examined the kinetics of the transcriptional response and HSF1 binding changes genome-wide after heat shock (HS) with high sensitivity and high spatial and temporal resolution using PRO-seq and ChIP-seq assays respectively in wild type and in hsf1-deletion mouse embryonic fibroblasts. The transcriptional response is rapid, dynamic, and extensive with activation of several hundred genes and repression of several thousands of genes. Although HSF1 is critically required for classical inducible Heat Shock Protein (HSP) genes, it is not required for the majority of gene activation. HSF1 acts mechanistically to promote RNA polymerase II (Pol II) release from the promoter-proximal pause, while recruitment and initiation of Pol II are predominantly HSF1-independent. Surprisingly, a major class of cytoskeleton genes is immediately (within 2.5 minutes) and transiently activated in an HSF1-independent manner. A second wave of regulation is characterized by robust activation or repression of new sets of genes. The broad repression of thousands of genes, a quarter of which are repressed immediately upon HS and the rest are repressed in the second wave of regulation, is mediated at the level of decreasing Pol II pause release and not at prior steps of Pol II recruitment or initiation. Notably, heat shock does not induce transcription of some previously defined HSP genes, and HSF2 â a homolog of HSF1 â does not compensate for the lack of HSF1. Together, these findings indicate that mammalian cells cope with stress by rapidly inducing pervasive and dramatic changes in transcription that are largely modulated at the step of pause release, and only a fraction of this regulation is HSF1-dependent. Examination of transcriptional regulation before and after heat shock in WT, HSF1-/-, and HSF1&2-/- MEFs

Project description:High-temperature stress is critical for all organisms and induces a profound cellular response. For Crenarchaeota, little information is available on how heat shock affects cellular processes and on how this response is regulated. We set out to study heat shock response in the thermoacidophilic model crenarchaeon Sulfolobus acidocaldarius, which thrives in volcanic hot springs and has an optimal growth temperature of 75°C. Pulse-labeling experiments demonstrated that a temperature shift to 86°C induces a drastic reduction of the transcriptional and translational activity, but that RNA and protein neosynthesis still occurs. By combining RNA sequencing and mass spectrometry, an integrated mapping of the transcriptome and proteome was performed. This revealed that heat shock causes an immediate change in the gene expression profile, with RNA levels of half of the genes being affected, followed by a more subtle reprogramming of the protein landscape. Functional enrichment analysis indicated that nearly all cellular processes are affected by heat shock. A limited correlation was observed in the differential expression on the RNA and protein level, suggesting a prevalence of post-transcriptional and post-translational regulation. Furthermore, promoter sequence analysis of heat shock regulon genes demonstrated the conservation of strong transcription initiation elements for highly induced genes, but an absence of a conserved protein-binding motif. It is, therefore, hypothesized that histone-lacking archaea such as Sulfolobales use an evolutionarily ancient regulatory mechanism that relies on temperature-responsive changes in DNA organization and compaction induced by the action of nucleoid-associated proteins, as well as on enhanced recruitment of initiation factors. IMPORTANCE Heat shock response is the ability to respond adequately to sudden temperature increases that could be harmful for cellular survival and fitness. It is crucial for microorganisms living in volcanic hot springs that are characterized by high temperatures and large temperature fluctuations. In this study, we investigated how S. acidocaldarius, which grows optimally at 75°C, responds to heat shock by altering its gene expression and protein production processes. We shed light on which cellular processes are affected by heat shock and propose a hypothesis on underlying regulatory mechanisms. This work is not only relevant for the organism's lifestyle, but also with regard to its evolutionary status. Indeed, S. acidocaldarius belongs to the archaea, an ancient group of microbes that is more closely related to eukaryotes than to bacteria. Our study thus also contributes to a better understanding of the early evolution of heat shock response.

Dataset Information

Mammalian Heat Shock Response and Mechanisms Underlying Its Genome-wide Transcriptional Regulation.

Publications

Mammalian Heat Shock Response and Mechanisms Underlying Its Genome-wide Transcriptional Regulation.

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