Similar Datasets
Project description:The non-proteolytic role of the proteasome in heterochromatin regulation
2019-06-16 | GSE103336 | GEO
Project description:Cumulative evidence suggests that non-proteolytic functions of the proteasome are involved in transcriptional regulation, mRNA export, and ubiquitin-dependent histone modification and thereby modulate the intracellular levels of regulatory proteins implicated in controlling key cellular functions. To date, the non-proteolytic roles of the proteasome have been mainly investigated in euchromatin; their effects on heterochromatin are largely unknown. Here, using fission yeast as a model, we randomly mutagenized the subunits of the 19S proteasome subcomplex and sought to uncover a direct role of the proteasome in heterochromatin regulation. We identified a mutant allele, rpt4-1, that disrupts a non-proteolytic function of the proteasome, also known as a non-proteolytic allele. Experiments performed using rpt4-1 cells revealed that the proteasome is involved in the regulation of heterochromatin spreading to prevent its uncontrolled invasion into neighboring euchromatin regions. Intriguingly, the phenotype of the non-proteolytic rpt4-1 mutant resembled that of epe1? cells, which lack the Epe1 protein that counteracts heterochromatin spreading. Both mutants exhibited variegated gene-silencing phenotypes across yeast colonies, spreading of heterochromatin, bypassing of the requirement for RNAi in heterochromatin formation at the outer repeat region (otr), and up-regulation of RNA polymerase II. Further analysis revealed Mst2, another factor that antagonizes heterochromatin spreading, may function redundantly with Rpt4. These observations suggest that the 19S proteasome may be involved in modulating the activities of Epe1 and Mst2. In conclusion, our findings indicate that the proteasome appears to have a heterochromatin-regulating function that is independent of its canonical function in proteolysis.
| S-EPMC5641893 | biostudies-literature
Project description:Domains of heterochromatin play important roles in the maintenance and regulation of eukaryotic genomes. However, the repressive nature of heterochromatin combined with its propensity to self-propagate necessitates the existence of robust mechanisms that limit heterochromatin spreading and thereby avoid silencing of expressed genes. A number of specific sequence elements have been found to serve as barriers to heterochromatin spreading; however, the mechanisms by which spreading is curtailed are generally not well understood. Here we uncover a role for PAF complex component Leo1 in regulating heterochromatin cis-spreading. A genetic screen revealed that loss of Leo1 results in spreading of heterochromatin across a centromeric (IRC) boundary element in fission yeast. Similar heterochromatin spreading was seen upon deletion of other components of the PAF complex, but not other factors involved in transcription-coupled chromatin modification, indicating a specific role for the PAF complex in heterochromatin regulation. Loss of Leo1 is associated with reduced levels of H4K16 acetylation at the boundary, while tethering of the H4K16 acetyltransferase Mst1 to boundary chromatin suppresses heterochromatin spreading in leo1? cells, suggesting that Leo1 antagonises heterochromatin spreading by facilitating H4K16 acetylation. Interestingly, Leo1 also regulates heterochromatin spreading independently of boundaries, and loss of Leo1 causes redistribution of heterochromatin, in particular resulting in substantial expansion of telomeric heterochromatin domains. The PAF complex is known to be an important regulator of transcription-related chromatin modifications; our findings reveal a previously undescribed role for this complex in global regulation of heterochromatin spreading in cis. 8 samples: input (whole cell extract) and IP from H3K9me2 ChIP in wild-type and leo1? cells, in duplicate
2015-05-22 | E-GEOD-61688 | biostudies-arrayexpress
Project description:The objective of this study is to identify the genes that are up-regulated amid proteasome dysfunction to facilitate the discovery of proteolytic pathways that are activated as a compensatory response to proteasome inhibition. Proteasome is a large multi-component proteolytic complex in the cell. It is responsible for the constitutive turn-over of many cellular proteins as well as the degradation of oxidized and/or unfolded proteins. With such a fundamental role in the cell, disruption of proteasome understandably can lead to disastrous outcome. Oxidative stress has been postulated as the driving mechanism for aging. Oxidatively modified proteins, which usually have lost their activity, require immediate removal by proteasome to maintain normal cellular function. Dysfunction of proteasome has also been linked to neuro-degenerative diseases such as Alzheimer?¢¬Ä¬ôs and Parkinson?¢¬Ä¬ôs diseases, those that are most commonly seen in aged population. There is more than one proteolytic pathway in the cell, and it has been reported that obstruction of any one of these pathways may enhance the activity of the others. Proteasomal function has been found to have decreased during aging, prompting researchers to hypothesize that failure to remove oxidized proteins may play an important role in aging. It would be interesting to determine the other proteolytic pathways that are activated after proteasome inhibition by a relatively specific inhibitor epoxomicin to help understand their roles in aging processes. Experiment Overall Design: Human embryonic kidney cells (HEK293) were untreated or treated with 1 uM epoxomicin for 1 and 6 hours. Total RNA was extracted for gene expression profiling using Affymetrix human genome U133 2.0 plus chip. A quadrupliate was prepared for each treatment. Experiment Overall Design: contributor: NHLBI Gene Expression Core Facility
2009-01-27 | E-GEOD-14429 | biostudies-arrayexpress
Project description:The objective of this study is to identify the genes that are up-regulated amid proteasome dysfunction to facilitate the discovery of proteolytic pathways that are activated as a compensatory response to proteasome inhibition. Proteasome is a large multi-component proteolytic complex in the cell. It is responsible for the constitutive turn-over of many cellular proteins as well as the degradation of oxidized and/or unfolded proteins. With such a fundamental role in the cell, disruption of proteasome understandably can lead to disastrous outcome. Oxidative stress has been postulated as the driving mechanism for aging. Oxidatively modified proteins, which usually have lost their activity, require immediate removal by proteasome to maintain normal cellular function. Dysfunction of proteasome has also been linked to neuro-degenerative diseases such as Alzheimer’s and Parkinson’s diseases, those that are most commonly seen in aged population. There is more than one proteolytic pathway in the cell, and it has been reported that obstruction of any one of these pathways may enhance the activity of the others. Proteasomal function has been found to have decreased during aging, prompting researchers to hypothesize that failure to remove oxidized proteins may play an important role in aging. It would be interesting to determine the other proteolytic pathways that are activated after proteasome inhibition by a relatively specific inhibitor epoxomicin to help understand their roles in aging processes. Keywords: time course, proteasome, inhibitor, oxidative stress, epoxomicin
2009-01-15 | GSE14429 | GEO
Project description:Heterochromatin, a highly compact chromatin state characterized by histone H3 lysine 9 methylation (H3K9me) and HP1 protein binding, epigenetically silences the underlying DNA and influences the expression of neighboring genes. Therefore the sites of heterochromatin assembly and its subsequent spreading are generally precisely determined. Here we show that in fission yeast, the combined absence of anti-silencing factors Mst2 and Epe1 results in uncontrolled heterochromatin spreading and severe growth defects. Interestingly, these cells quickly recover by accumulating H3K9me at the clr4+ locus, which encodes the H3K9 methyltransferase essential for heterochromatin assembly, thereby leading to reduced expression of Clr4 to restrain heterochromatin spreading. Preventing H3K9me at the clr4+ locus resulted in the accumulation of H3K9me at the rik1+ locus, which encodes another component of the Clr4 complex essential for H3K9me. Our results demonstrate that promiscuous heterochromatin assembly enables fast adaptation in response to changes in chromatin landscape and illustrate a negative feedback mechanism by which cells counteract toxic heterochromatin accumulation.
2015-03-13 | GSE60521 | GEO
Project description:The proteasome can regulate transcription through proteolytic processing of transcription factors and via gene locus binding, but few targets of proteasomal regulation have been identified. Using genome-wide location analysis and transcriptional profiling in Saccharomyces cerevisiae, we have established which genes are bound and regulated by the proteasome, and by Spt23 and Mga2, transcription factors activated by the proteasome. We observed proteasome association with gene sets that are highly transcribed, controlled by the mating-type loci, and involved in lipid metabolism. At ribosomal protein genes, proteasome and RNA polymerase II binding was enriched in a proteasome mutant, indicating a role for the proteasome in dissociating elongation complexes. The genomic occupancies of Spt23 and Mga2 overlapped significantly with the genes bound by the proteasome. Finally, the proteasome acts in two distinct ways, one dependent and one independent of Spt23/Mga2 cleavage, providing evidence for cooperative gene regulation by the proteasome and its substrates. Keywords: ChIP-chip; genetic modification transcriptional profiling Six genomic localization analysis (GLA, ChIP2) experiments are represented by 18 samples. Six transcriptional profiling experiments (prof) are also represented. Experiments were generally done in triplicate, with fluors swapped on the third replicate.
2006-02-28 | E-GEOD-4272 | biostudies-arrayexpress
Project description:Epe1 histone demethylase restricts H3K9-methylation-dependent heterochromatin, preventing it from spreading over, and silencing, gene-containing regions in fission yeast. External stress induces an adaptive response allowing heterochromatin island formation that confers resistance on surviving wild-type lineages. Here we investigate the mechanism by which Epe1 is regulated in response to stress. Exposure to caffeine or antifungals results in Epe1 ubiquitylation and proteasome-dependent removal of the N-terminal 150 residues from Epe1, generating truncated tEpe1 which accumulates in the cytoplasm. Constitutive tEpe1 expression increases H3K9 methylation over several chromosomal regions, reducing expression of underlying genes and enhancing resistance. Reciprocally, constitutive non-cleavable Epe1 expression decreases resistance. tEpe1-mediated resistance requires a functional JmjC demethylase domain. Moreover, caffeine-induced Epe1-to-tEpe1 cleavage is dependent on an intact cell-integrity MAP kinase stress signalling pathway, mutations in which alter resistance. Thus, environmental changes provoke a mechanism that curtails the function of this key epigenetic modifier, allowing heterochromatin to reprogram gene expression, thereby bestowing resistance to some cells within a population. H3K9me-heterochromatin components are conserved in human and crop plant fungal pathogens for which a limited number of antifungals exist. Our findings reveal how transient heterochromatin-dependent antifungal resistant epimutations develop and thus inform on how they might be countered.
2022-05-04 | GSE190267 | GEO
Project description:Epe1 histone demethylase restricts H3K9-methylation-dependent heterochromatin, preventing it from spreading over, and silencing, gene-containing regions in fission yeast. External stress induces an adaptive response allowing heterochromatin island formation that confers resistance on surviving wild-type lineages. Here we investigate the mechanism by which Epe1 is regulated in response to stress. Exposure to caffeine or antifungals results in Epe1 ubiquitylation and proteasome-dependent removal of the N-terminal 150 residues from Epe1, generating truncated tEpe1 which accumulates in the cytoplasm. Constitutive tEpe1 expression increases H3K9 methylation over several chromosomal regions, reducing expression of underlying genes and enhancing resistance. Reciprocally, constitutive non-cleavable Epe1 expression decreases resistance. tEpe1-mediated resistance requires a functional JmjC demethylase domain. Moreover, caffeine-induced Epe1-to-tEpe1 cleavage is dependent on an intact cell-integrity MAP kinase stress signalling pathway, mutations in which alter resistance. Thus, environmental changes provoke a mechanism that curtails the function of this key epigenetic modifier, allowing heterochromatin to reprogram gene expression, thereby bestowing resistance to some cells within a population. H3K9me-heterochromatin components are conserved in human and crop plant fungal pathogens for which a limited number of antifungals exist. Our findings reveal how transient heterochromatin-dependent antifungal resistant epimutations develop and thus inform on how they might be countered.
2022-10-13 | PXD030205 | Pride
Project description:Heterochromatin plays important roles in eukaryotic genome regulation. However, the repressive nature of heterochromatin combined with its propensity to self-propagate necessitates robust mechanisms to contain heterochromatin within defined boundaries and thus prevent silencing of expressed genes. Here we show that loss of the PAF complex (PAFc) component Leo1 compromises chromatin boundaries, resulting in invasion of heterochromatin into flanking euchromatin domains. Similar effects are seen upon deletion of other PAFc components, but not other factors with related functions in transcription-associated chromatin modification, indicating a specific role for PAFc in heterochromatin regulation. Loss of Leo1 results in reduced levels of H4K16 acetylation at boundary regions, while tethering of the H4K16 acetyltransferase Mst1 to boundary chromatin suppresses heterochromatin spreading in leo1? cells, suggesting that Leo1 antagonises heterochromatin spreading by promoting H4K16 acetylation. Our findings reveal a previously undescribed role for PAFc in regulating global heterochromatin distribution.
| S-EPMC4450266 | biostudies-literature