Hsf1 yeast

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...

Morphological plasticity is a key virulence trait for many fungal pathogens. For the opportunistic fungal pathogen Candida albicans, transitions among yeast, pseudohyphal, and hyphal forms are critical for virulence, because the morphotypes play distinct roles in the infection process. C. albicans morphogenesis is induced in response to many host-relevant conditions and is regulated by complex signaling pathways and cellular processes. Perturbation of either cell-cycle progression or protein homeostasis induces C...

Ogataea parapolymorpha (Hansenula polymorpha DL-1) is a thermotolerant methylotrophic yeast with biotechnological applications. Here, O. parapolymorpha genes whose expression is induced in response to heat shock were identified by transcriptome analysis and shown to possess heat shock elements (HSEs) in their promoters. The function of O. parapolymorpha HSF1 encoding a putative heat shock transcription factor 1 (OpHsf1) was characterized in the context of heat stress response. Despite exhibiting low sequence identity (26%) to its Saccharomyces cerevisiae homolog, OpHsf1 harbors conserved domains including a DNA binding domain (DBD), domains involved in trimerization (TRI), transcriptional activation (AR1, AR2), transcriptional repression (CE2), and a C-terminal modulator (CTM) domain...

Under thermal stress, different protein quality control (PQC) strategies are activated to maintain an intact proteome, which may vary from one model system to another. Hence thermo-sensitive proteins that lose their active conformation might be refolded with the aid of chaperones or removed by the ubiquitin-proteasome system or the process of autophagy. We have recently developed thermo-sensitive reporters to study PQC in fission yeast and shown the relevance of a third adaptation strategy: the sequestration of misfolded proteins into inclusions which will prevent a rapid degradation and allow the refolding once stress ends...

Cells exposed to heat shock induce a conserved gene expression program, the heat shock response (HSR), encoding protein homeostasis (proteostasis) factors. Heat shock also triggers proteostasis factors to form subcellular quality control bodies, but the relationship between these spatial structures and the HSR is unclear. Here we show that localization of the J-protein Sis1, a cofactor for the chaperone Hsp70, controls HSR activation in yeast. Under nonstress conditions, Sis1 is concentrated in the nucleoplasm, where it promotes Hsp70 binding to the transcription factor Hsf1, repressing the HSR...

Cells adapt to conditions that compromise protein conformational stability by activating various stress response pathways, but the mechanisms used in sensing misfolded proteins remain unclear. Moreover, aggregates of disease proteins often fail to induce a productive stress response. Here, using a yeast model of polyQ protein aggregation, we identified Sis1, an essential Hsp40 co-chaperone of Hsp70, as a critical sensor of proteotoxic stress. At elevated levels, Sis1 prevented the formation of dense polyQ inclusions and directed soluble polyQ oligomers towards the formation of permeable condensates...

Upon acute heat stress (HS), overall mRNA transcription, processing, and export are inhibited, leading to cell growth arrest. However, how cells turn off mRNA metabolism is not fully understood. Here, we show that acute HS results in the segregation and aggregation of multiple nuclear and nucleolar proteins into ring-like structures located at the nucleolar periphery (nucleolar rings [NuRs]). NuRs sequester essential factors required for nuclear mRNA metabolism and nuclear pore complex function, as well as cell-cycle regulators...

Heat shock induces a conserved transcriptional program regulated by heat shock factor 1 (Hsf1) in eukaryotic cells. Activation of this heat shock response is triggered by heat-induced misfolding of newly synthesized polypeptides, and so has been thought to depend on ongoing protein synthesis. Here, using the budding yeast Saccharomyces cerevisiae, we report the discovery that Hsf1 can be robustly activated when protein synthesis is inhibited, so long as cells undergo cytosolic acidification. Heat shock has long been known to cause transient intracellular acidification which, for reasons which have remained unclear, is associated with increased stress resistance in eukaryotes...

Hsp70 is a highly conserved molecular chaperone critical for the folding of new and denatured proteins. While traditional models state that cells respond to stress by upregulating inducible HSPs, this response is relatively slow and is limited by transcriptional and translational machinery. Recent studies have identified a number of post-translational modifications (PTMs) on Hsp70 that act to fine-tune its function. We utilized mass spectrometry to determine whether yeast Hsp70 (Ssa1) is differentially modified upon heat shock...

Hsf1 is an ancient transcription factor that responds to protein folding stress by inducing the heat-shock response (HSR) that restore perturbed proteostasis. Hsp70 chaperones negatively regulate the activity of Hsf1 via stress-responsive mechanisms that are poorly understood. Here we have reconstituted budding yeast Hsf1-Hsp70 activation complexes and find that surplus Hsp70 inhibits Hsf1 DNA-binding activity. Hsp70 binds Hsf1 via its canonical substrate binding domain and Hsp70 regulates Hsf1 DNA binding activity...

Protein homeostasis and cellular fitness in the presence of proteotoxic stress is promoted by heat shock factor 1 (Hsf1), which controls basal and stress-induced expression of molecular chaperones and other targets. The major heat shock proteins and molecular chaperones Hsp70  and Hsp90, in turn, participate in a negative feedback loop that ensures appropriate coordination of the heat shock response with environmental conditions. Features of this regulatory circuit in the budding yeast Saccharomyces cerevisiae have been recently defined, most notably regarding direct interaction between Hsf1 and the constitutively expressed Hsp70 protein Ssa1...

Ribosome biogenesis is a complex and energy-demanding process requiring tight coordination of ribosomal RNA (rRNA) and ribosomal protein (RP) production. Given the extremely high level of RP synthesis in rapidly growing cells, alteration of any step in the ribosome assembly process may impact growth by leading to proteotoxic stress. Although the transcription factor Hsf1 has emerged as a central regulator of proteostasis, how its activity is coordinated with ribosome biogenesis is unknown. Here we show that arrest of ribosome biogenesis in the budding yeast S...

While sexual reproduction is pervasive in eukaryotic cells, the strategies employed by fungal species to achieve and complete sexual cycles is highly diverse and complex. Many fungi, including Saccharomyces cerevisiae and Schizosaccharomyces pombe, are homothallic (able to mate with their own mitotic descendants) because of homothallic switching (HO) endonuclease-mediated mating-type switching. Under laboratory conditions, the human fungal pathogen Candida albicans can undergo both heterothallic and homothallic (opposite- and same-sex) mating...

Transcriptional induction of heat shock protein (HSP) genes is accompanied by dynamic changes in their 3D structure and spatial organization, yet the molecular basis for these phenomena remains unknown. Using chromosome conformation capture and single-cell imaging, we show that genes transcriptionally activated by Hsf1 specifically interact across chromosomes and coalesce into diffraction-limited intranuclear foci. Genes activated by the alternative stress regulators Msn2/Msn4, in contrast, do not interact among themselves nor with Hsf1 targets...

Heat Shock Factor 1 is the master transcriptional regulator of molecular chaperones and binds to the same cis-acting Heat Shock Element (HSE) across the eukaryotic lineage. In budding yeast, Hsf1 drives the transcription of ∼20 genes essential to maintain proteostasis under basal conditions, yet its specific targets and extent of inducible binding during heat shock remain unclear. Here, we combine Hsf1 ChIP-seq, nascent RNA-seq and Hsf1 nuclear depletion to quantify Hsf1 binding and transcription across the yeast genome...

Sulfide-quinone oxidoreductase (SQR) is a key enzyme of sulfide metabolism in metazoans, and responsible for oxidizing sulfide into thiosulfate and transmitting the generated electrons to the ubiquinone. It has been revealed that the sqr mRNA level increases significantly in echiuran worm Urechis unicinctus exposed to sulfide, and HSF1, NF1 and Sp1 have been verified to participate in its transcriptional regulation. In this study, we obtained 23 potential transcription factors interacting possibly with the proximal region (-391 to +50) of sqr promoter, and focused on the RWD domain-containing 1 (Rwdd1), a protein with the maximum number of clones in yeast one-hybrid (Y1H) screening, to investigate its transcriptional regulation to U...

The master regulator of thermal stress response, Hsf1, is also an essential determinant for viability and virulence in Candida albicans. Our recent studies highlighted that apart from ubiquitous roles of Hsf1 at higher temperatures, it also has myriad non-heat shock responsive roles essential under iron deprivation and drug defense. Here, we further explored its implications in the normal cellular functioning, by profiling its genome-wide occupancy using chromatin immuno-precipitation coupled to high-density tiling arrays under basal and iron deprived conditions...

The impact of fungal pathogens on human health is devastating. For fungi and other pathogens, a key determinant of virulence is the capacity to thrive at host temperatures, with elevated temperature in the form of fever as a ubiquitous host response to defend against infection. A prominent feature of cells experiencing heat stress is the increased expression of heat shock proteins (Hsps) that play pivotal roles in the refolding of misfolded proteins in order to restore cellular homeostasis. Transcriptional activation of this heat shock response is orchestrated by the essential heat shock transcription factor, Hsf1...

Over 40% of proteins in any eukaryotic genome encode intrinsically disordered regions (IDRs) that do not adopt defined tertiary structures. Certain IDRs perform critical functions, but discovering them is non-trivial as the biological context determines their function. We present IDR-Screen, a framework to discover functional IDRs in a high-throughput manner by simultaneously assaying large numbers of DNA sequences that code for short disordered sequences. Functionality-conferring patterns in their protein sequence are inferred through statistical learning...

Response mechanisms to external stress rely on networks of proteins able to activate specific signaling pathways to ensure the maintenance of cell proteostasis. Many of the proteins mediating this kind of response contain intrinsically disordered regions, which lack a defined structure, but still are able to interact with a wide range of clients that modulate the protein function. Some of these interactions are mediated by specific short sequences embedded in the longer disordered regions. Because the physicochemical properties that promote functional and abnormal interactions are similar, it has been shown that, in globular proteins, aggregation-prone and binding regions tend to overlap...