Heat stress induced Cup9 dependent transcriptional regulation of Sir2
15 Jan 2015-Molecular and Cellular Biology (American Society for Microbiology)-Vol. 35, Iss: 2, pp 437-450
TL;DR: The mechanism by which Sir2 is regulated under heat stress is demonstrated, which reveals that a transient heat shock causes a drastic reduction in the SIR2 transcript which results in sustained failure to initiate silencing for as long as 90 generations.
Abstract: The epigenetic writer Sir2 maintains the heterochromatin state of chromosome in three chromosomal regions, namely, the silent mating type loci, telomeres, and the ribosomal DNA (rDNA). In this study, we demonstrated the mechanism by which Sir2 is regulated under heat stress. Our study reveals that a transient heat shock causes a drastic reduction in the SIR2 transcript which results in sustained failure to initiate silencing for as long as 90 generations. Hsp82 overexpression, which is the usual outcome of heat shock treatment, leads to a similar downregulation of SIR2 transcription. Using a series of genetic experiments, we have established that heat shock or Hsp82 overexpression causes upregulation of CUP9 that, in turn, represses SIR2 transcription by binding to its upstream activator sequence. We have mapped the cis regulatory element of SIR2. Our study shows that the deletion of cup9 causes reversal of the Hsp82 overexpression phenotype and upregulation of SIR2 expression in heat-induced Hsp82-overexpressing cells. On the other hand, we found that Cup9 overexpression represses SIR2 transcription and leads to a failure in the establishment of heterochromatin. The results of our study highlight the mechanism by which environmental factors amend the epigenetic configuration of chromatin.
Citations
More filters
TL;DR: The role of Hsp90 is discussed in all the three aforementioned mechanisms of transcriptional control, taking examples from various model organisms with a special emphasis on cancer progression.
Abstract: In the last decade Hsp90 has emerged as a major regulator of cancer cell growth and proliferation In cancer cells, it assists in giving maturation to oncogenic proteins including several kinases and transcription factors Recent studies have shown that apart from its chaperone activity, it also imparts regulation of transcription machinery and thereby alters the cellular physiology Hsp90 and its co-chaperones modulate transcription at-least at three different levels In the first place, they alter the steady-state levels of certain transcription factors in response to various physiological cues Secondly, they modulate the activity of certain epigenetic modifiers, such as histone deacetylases or DNA methyl transferases, and thereby respond to the change in the environment Thirdly, they participate in the eviction of histones from the promoter region of certain genes and thereby turn on gene expression In this review, we discuss the role of Hsp90 in all the three aforementioned mechanisms of transcriptional control, taking examples from various model organisms with a special emphasis on cancer progression
54 citations
01 Aug 2012
TL;DR: The results establish HSP90 client recognition as a combinatorial process: CDC37 provides recognition of the kinase family, whereas thermodynamic parameters determine client binding within the family.
Abstract: National Institutes of Health (U.S.). Genomics Based Drug Discovery-Driving Medical Project (Grant UL1-DE019585)
28 citations
TL;DR: The recent advancements that for the first time provide a mechanistic understanding of how heterochromatin, dictated by histone modifications specifically, is preserved during S-phase are discussed.
Abstract: Saccharomyces cerevisiae (budding yeast) and Schizosaccharomyces pombe (fission yeast) are two of the most recognised and well-studied model systems for epigenetic regulation and the inheritance of chromatin states. Their silent loci serve as a proxy for heterochromatic chromatin in higher eukaryotes, and as such both species have provided a wealth of information on the mechanisms behind the establishment and maintenance of epigenetic states, not only in yeast, but in higher eukaryotes. This review focuses specifically on the role of histone modifications in governing telomeric silencing in S. cerevisiae and centromeric silencing in S. pombe as examples of genetic loci that exemplify epigenetic inheritance. We discuss the recent advancements that for the first time provide a mechanistic understanding of how heterochromatin, dictated by histone modifications specifically, is preserved during S-phase. We also discuss the current state of our understanding of yeast nucleosome dynamics during DNA replication, an essential component in delineating the contribution of histone modifications to epigenetic inheritance.
25 citations
TL;DR: The model organism Saccharomyces cerevisiae is used to establish that a transient heat shock and particularly the concomitant induction of Hsp90 lead to increased genomic instability via transcriptional regulation of the major checkpoint kinase Rad53.
Abstract: It is well documented that elevated body temperature causes tumors to regress upon radiotherapy. However, how hyperthermia induces DNA damage sensitivity is not clear. We show that a transient heat shock and particularly the concomitant induction of Hsp90 lead to increased genomic instability under DNA-damaging conditions. Using Saccharomyces cerevisiae as a model eukaryote, we demonstrate that elevated levels of Hsp90 attenuate efficient DNA damage signaling and dictate preferential use of the potentially mutagenic double-strand break repair pathway. We show that under normal physiological conditions, Hsp90 negatively regulates RAD53 transcription to suppress DNA damage checkpoint activation. However, under DNA damaging conditions, RAD53 is derepressed, and the increased level of Rad53p triggers an efficient DNA damage response. A higher abundance of Hsp90 causes increased transcriptional repression on RAD53 in a dose-dependent manner, which could not be fully derepressed even in the presence of DNA damage. Accordingly, cells behave like a rad53 loss-of-function mutant and show reduced NHEJ efficiency, with a drastic failure to up-regulate RAD51 expression and manifestly faster accumulation of CLN1 and CLN2 in DNA-damaged G1, cells leading to premature release from checkpoint arrest. We further demonstrate that Rad53 overexpression is able to rescue all of the aforementioned deleterious effects caused by Hsp90 overproduction.
12 citations
Cites background or methods from "Heat stress induced Cup9 dependent ..."
...was then cross-linked with 1% formaldehyde at 30C for 15 minutes and the experiment was performed as mentioned earlier (Laskar et al., 2014)....
[...]
...It modulates the activity of chromatin modifiers and thereby alters gene expression (Laskar et al., 2011; Laskar et al., 2014; Tariq et al., 2009; Khurana and Bhattacharyya, 2015)....
[...]
TL;DR: This work proposes a new model where the increase of entropy leads to the formation of double strand breaks, resulting in an aging phenotype, which not only offers a new perspective on aging research and facilitates experimental validation, but could also serve as a useful explanatory tool.
11 citations
References
More filters
TL;DR: The large conformational flexibility of HSp90 and a multitude of dynamic co-chaperone complexes contribute to generating functional diversity, and allow Hsp90 to assist a wide range of substrates.
Abstract: Heat-shock protein 90 (Hsp90) is an abundant and highly conserved molecular chaperone that is essential for viability in eukaryotes. Hsp90 fulfills a housekeeping function in contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. A remarkable proportion of its substrates are proteins involved in cell cycle control and signal transduction. Hsp90 acts with a cohort of Hsp90 co-chaperones that modulate its substrate recognition, ATPase cycle and chaperone function. The large conformational flexibility of Hsp90 and a multitude of dynamic co-chaperone complexes contribute to generating functional diversity, and allow Hsp90 to assist a wide range of substrates.
754 citations
"Heat stress induced Cup9 dependent ..." refers background in this paper
...Unlike the other chaperones, such as Hsp70 and Hsp40, which act early in the folding process, the Hsp90 family interacts with the substrates at the later stages of protein folding (24, 25)....
[...]
TL;DR: LUMIER (for luminescence-based mammalian interactome mapping), an automated high-throughput technology, is developed and applied to the transforming growth factor–β (TGFβ) pathway and it is shown that Occludin regulates TGFβ type I receptor localization for efficient TGF β-dependent dissolution of tight junctions during epithelial-to-mesenchymal transitions.
Abstract: Signaling pathways transmit information through protein interaction networks that are dynamically regulated by complex extracellular cues. We developed LUMIER (for luminescence-based mammalian interactome mapping), an automated high-throughput technology, to map protein-protein interaction networks systematically in mammalian cells and applied it to the transforming growth factor-beta (TGFbeta) pathway. Analysis using self-organizing maps and k-means clustering identified links of the TGFbeta pathway to the p21-activated kinase (PAK) network, to the polarity complex, and to Occludin, a structural component of tight junctions. We show that Occludin regulates TGFbeta type I receptor localization for efficient TGFbeta-dependent dissolution of tight junctions during epithelial-to-mesenchymal transitions.
746 citations
"Heat stress induced Cup9 dependent ..." refers methods in this paper
...uation by LUMIER assay (21) revealed that 60% of the Hsp90...
[...]
TL;DR: In this paper, the authors systematically and quantitatively surveyed most human kinases, transcription factors, and E3 ligases for interaction with HSP90 and its cochaperone CDC37.
732 citations
TL;DR: JASPAR is a popular open-access database for matrix models describing DNA-binding preferences for transcription factors and other DNA patterns that has been expanded and equipped with additional functions aimed at both casual and power users.
Abstract: JASPAR is a popular open-access database for matrix models describing DNA-binding preferences for transcription factors and other DNA patterns. With its third major release, JASPAR has been expanded and equipped with additional functions aimed at both casual and power users. The heart of the JASPAR database—the JASPAR CORE sub-database—has increased by 12% in size, and three new specialized sub-databases have been added. New functions include clustering of matrix models by similarity, generation of random matrices by sampling from selected sets of existing models and a language-independent Web Service applications programming interface for matrix retrieval. JASPAR is available at http://jaspar.genereg.net.
725 citations
"Heat stress induced Cup9 dependent ..." refers methods in this paper
...The transcription factors from both the databases TRANSFAC (36) and JASPAR (37), with their ranks, are shown in Table 3....
[...]
TL;DR: Results reveal that the repression of heat shock gene transcription, which occurs during attenuation, is due to the association of Hsp70 with the HSF1 transactivation domain, thus providing a plausible explanation for the role of molecular chaperones in at least one key step in the autoregulation of the heat shock response.
Abstract: The rapid yet transient transcriptional activation of heat shock genes is mediated by the reversible conversion of HSF1 from an inert negatively regulated monomer to a transcriptionally active DNA-binding trimer. During attenuation of the heat shock response, transcription of heat shock genes returns to basal levels and HSF1 reverts to an inert monomer. These events coincide with elevated levels of Hsp70 and other heat shock proteins (molecular chaperones). Here, we show that the molecular chaperone Hsp70 and the cochaperone Hdj1 interact directly with the transactivation domain of HSF1 and repress heat shock gene transcription. Overexpression of either chaperone represses the transcriptional activity of a transfected GAL4-HSF1 activation domain fusion protein and endogenous HSF1. As neither the activation of HSF1 DNA binding nor inducible phosphorylation of HSF1 was affected, the primary autoregulatory role of Hsp70 is to negatively regulate HSF1 transcriptional activity. These results reveal that the repression of heat shock gene transcription, which occurs during attenuation, is due to the association of Hsp70 with the HSF1 transactivation domain, thus providing a plausible explanation for the role of molecular chaperones in at least one key step in the autoregulation of the heat shock response.
653 citations