Project description:Environmental stress, such as oxidative or heat stress, induces the activation of the heat shock response
(HSR) and leads to an increase in the heat shock proteins (HSPs) level. These HSPs act as molecular
chaperones to maintain cellular proteostasis. Controlled by highly intricate regulatory mechanisms,
having stress-induced activation and feedback regulations with multiple partners, the HSR is still
incompletely understood. In this context, we propose a minimal molecular model for the gene
regulatory network of the HSR that reproduces quantitatively different heat shock experiments both
on heat shock factor 1 (HSF1) and HSPs activities. This model, which is based on chemical kinetics
laws, is kept with a low dimensionality without altering the biological interpretation of the model
dynamics. This simplistic model highlights the titration of HSF1 by chaperones as the guiding line of
the network. Moreover, by a steady states analysis of the network, three different temperature stress
regimes appear: normal, acute, and chronic, where normal stress corresponds to pseudo thermal
adaption. The protein triage that governs the fate of damaged proteins or the different stress regimes
are consequences of the titration mechanism. The simplicity of the present model is of interest in
order to study detailed modelling of cross regulation between the HSR and other major genetic
networks like the cell cycle or the circadian clock.
Sivéry, A., Courtade, E., Thommen, Q. (2016). A minimal titration model of the mammalian dynamical heat shock response. Physical biology, 13(6), 066008.
Project description:We utilize ribosome profiling to directly monitor translation in E. coli at 30 °C and investigate how this changes after 10-20 minutes of heat shock at 42 °C. Translation is controlled by the interplay of several RNA hybridization processes, which are expected to be temperature sensitive. We observe that translation efficiencies are robustly maintained after thermal heat shock and after mimicking the heat shock response transcriptional program at 30 °C.
Project description:PFJ (4 ml for a final concentration of 19,000 mg gallic acid equivalent (GAE) per kg diet or 0.86 mg GAE per kcal diet) was supplemented to larvae of fruit flies (Drosophila melanogaster) given a semi-purified diet to observe for possible effects on energy metabolism and lifespan. Fat bodies extracted from these larvae were used five days since the egg stage for gene expression studies. Results from the microarray data analysis carried out show that fruit fly larva fat bodies given PFJ had up-regulated heat shock protein genes, while cell cycle and growth genes were down-regulated.
Project description:Heat shock transcription factors HSF1 and HSF2 both are necessary for proper spermatogenesis, which is disrupted at elevated temperatures. We studied how HSF1 and HSF2 cooperate during the heat shock response in mouse spermatocytes. For this purpose we used ChIP-sequencing. ChIP-Seq analyses revealed that the temperature elevation induces remodeling of HSF1 and HSF2 binding to chromatin. The highest HSF1-chromatin binding was observed at 43°C, when HSF2-chromatin binding was reduced. Many promoters (mainly Hsp genes) were occupied by both heat shock factors at physiological temperature of testes and/or at 38°C. In contrary at 43°C only HSF1 was bound. Obtained results suggest that HSF1 and HSF2 could cooperate in regulation of the transcription of some genes only at physiological temperatures and/or at 38°C. Alteration in HSFs interactions and their binding to chromatin could be one of the reason of increased spermatogenic cell death observed after heat shock.
Project description:This is a mathematical model of Hsp70 induction. To model heat shock effects, the model incorporates temperature dependencies in transcirption to Hsp70 mRNA and in dissociation of transcriptional complexes, in addition to a formal expression relating temperature to protein denaturation.
Project description:In Drosophila larvae, acquired synaptic thermotolerance following heat shock has previously been shown to correlate with the induction of heat shock proteins (Hsps) including HSP70. We tested the hypothesis that synaptic thermotolerance would be significantly diminished in a temperature-sensitive strain (hsf4) which has been reported not to be able to produce inducible Hsps in response to heat shock. Contrary to our hypothesis, considerable thermoprotection was still observed at hsf4 larval synapses following heat shock. To investigate the cause of this thermoprotection, we conducted DNA microarray experiments to identify heat-induced transcript changes in these organisms. Transcripts of the hsp83, dnaJ-1(hsp40) and gstE1 genes were significantly up-regulated in hsf4 larvae after heat shock. In addition, increases in the levels of Hsp83 and DnaJ-1 proteins but not in the inducible form of Hsp70 were detected by Western blotting. The mode of heat shock administration differentially affected the relative transcript and translational changes for these chaperones. These results indicate that the compensatory up-regulation of constitutively expressed Hsps, in the absence of the synthesis of inducible Hsps including HSP70, could still provide substantial thermoprotection to both synapses and the whole organism. Keywords: heat shock response
Project description:Metazoan chromosomes in interphase nucleus are partitioned into discrete three dimensional physical domains which confine epigenetically modified chromatin and are relative stable across different cell types even species1-4. Physical domains are segregated preferentially at DNase I hypersensitive sequences of high density of active gene and insulator proteins which are hypothesized contributing together to domain border formation3,4. However, whether physical domain structure can be maintained without insulator proteins and transcription is unknown5-8. Transcription of most genes and the insulator proteins binding can be severely impaired in heat shocked (HS) fruit fly nuclei9. Here we show that chromatin contact frequency increases within and decreases beyond ~100kb after HS respectively accompanied by repartitioning of the Drosophila chromosomes into a different array of physical domain. Prominently, domains tend to merge because borders disappeared are more than borders newly emerged which are located more frequently in repressive chromatin. In contrast to previous hypothesis1,3,4, changes in insulator proteins enrichment and RNAPII show no noticeable difference at lost or emerged borders. Our results show a metazoan genome can be quickly reconfigured as cells undergo brief physiological stress. In addition to insulator proteins and transcription, we speculate that extra trans-factors binding and various biological activities are required for the establishment and maintenance of physical domains. Moreover, we found long-range chromatin interaction network is reshaped after HS implying long-range chromatin interactions can be formed due to domain level reorganization of chromosomes despite functional relevance. We anticipate our analysis to be a starting point for more intensive experimental investigation into the elusive mechanisms behind the physical domain partition and dynamic reconfiguration of metazoan genomes.
Project description:Whole-genome analysis of heat shock factor binding sites in Drosophila melanogaster. Heat shock factor IP DNA from non-shock (room temperature) Kc 167 cells compared to whole cell extract on Agilent 2x244k tiling arrays.
Project description:A transcriptome analysis was applied on two peach (Prunus persica L.) cultivars with different sensitivity to low temperature regimes to identify cold-responsive genes that might be involved in tolerance to long low temperature storage. Peach fruit from ‘Morettini No2’ and ‘Royal Glory’, a sensitive and a tolerant, to chilling injury cultivars, respectively, were harvested at commercial maturity stage and allowed to ripen at room temperature (25°C) or subjected to 4 and 6-weeks of cold storage (0°C, 95% R.H.) followed by ripening at room temperature. Microarray experiments, employing the peach microarray platform (μ PEACH 1.0), were carried out by comparing harvested fruit against 4- and 6-week cold-stored fruit. The analysis identified 173 and 313 genes that were differentially expressed in ‘Morettini No2’ and ‘Royal Glory’ fruit after 4 weeks, respectively. However, the 6 weeks cold storage provoked a decrease in the total number of genes differentially expressed in both cultivars. RNA blot analysis validated the differential expression of certain genes showed in microarray data. Among these genes, two heat shock proteins (hsps), a putative β-D-xylosidase, an expansin, a dehydrin and a pathogenesis-related protein PR-4B precursor were induced during cold storage in both cultivars. The induction of hsps and the putative β-D-xylosidase appeared to be independent on the duration of postharvest treatment. On the other hand, transcript levels of lipoxygenase were quite constant during postharvest ripening, while a strong reduction or disappearance was observed after cold storage. A dehydration-induced RD22-like protein showed a reduction in the accumulation of transcripts during postharvest ripening independently on the temperature conditions. Overall, the current study shed some light on the molecular aspects of cold stress in peach fruit quality and identified some ripening and/or cold-induced genes which function need further elucidation.