DamID for Cid14 in wild-type and swi6∆
Ontology highlight
ABSTRACT:
ORGANISM(S): Schizosaccharomyces pombe
PROVIDER: GSE36956 | GEO | 2012/06/12
SECONDARY ACCESSION(S): PRJNA157505
REPOSITORIES: GEO
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Project description:Proteins of the conserved HP1 family are elementary components of heterochromatin and are generally assumed to play a central role in creating a rigid heterochromatic network that is densely packed and inaccessible to the transcription machinery. In this study we demonstrate that the fission yeast HP1 protein Swi6 exists as a single highly dynamic population and rapidly exchanges in cis and in trans between different heterochromatic regions. Binding to methylated H3K9 or to heterochromatic RNA decelerates Swi6 mobility. We further show that Swi6 is largely dispensable to maintain heterochromatin domains. In contrast, our results disclose an unexpected role of Swi6 in demarcating constitutive heterochromatin from neighboring euchromatin. Our results are consistent with a stochastic model of heterochromatin and imply that heterochromatin is permissive for transcription throughout the cell cycle. Rather than promoting maintenance and spreading of heterochromatin, Swi6 appears to limit these processes to ensure that heterochromatin is appropriately confined.
2015-10-07 | GSE70945 | GEO
Project description:Heterochromatin is important for the maintenance of genome stability and regulation of gene expression, yet our knowledge of heterochromatin structure and function is incomplete. We identified four novel Drosophila heterochromatin proteins. Three of these proteins (HP3, HP4, and HP5) interact directly with HP1, while HP6 in turn binds to each of these three proteins. Immunofluorescence microscopy and genome-wide mapping of in vivo binding sites shows that all four proteins are components of heterochromatin. Depletion of HP1 causes redistribution of all four proteins, indicating that HP1 is essential for their heterochromatic targeting. Finally, mutants of HP4 and HP5 are dominant suppressors of position effect variegation, demonstrating their importance in heterochromatic gene silencing. These results indicate that HP1 acts as a docking platform for several mediator proteins that contribute to heterochromatin function. Keywords: DamID knock-down
2007-02-02 | GSE6411 | GEO
Project description:Proteins of the conserved HP1 family are elementary components of heterochromatin and are generally assumed to play a central role in creating a rigid heterochromatic network that is densely packed and inaccessible to the transcription machinery. In this study we demonstrate that the fission yeast HP1 protein Swi6 exists as a single highly dynamic population and rapidly exchanges in cis and in trans between different heterochromatic regions. Binding to methylated H3K9 or to heterochromatic RNA decelerates Swi6 mobility. We further show that Swi6 is largely dispensable to maintain heterochromatin domains. In contrast, our results disclose an unexpected role of Swi6 in demarcating constitutive heterochromatin from neighboring euchromatin. Our results are consistent with a stochastic model of heterochromatin and imply that heterochromatin is permissive for transcription throughout the cell cycle. Rather than promoting maintenance and spreading of heterochromatin, Swi6 appears to limit these processes to ensure that heterochromatin is appropriately confined.
2015-10-07 | GSE61136 | GEO
Project description:HP1 proteins bind dynamically to H3K9 methylation and are essential for establishing and maintaining transcriptionally silent epigenetic states, known as heterochromatin. HP1 proteins can dimerize, forming a binding interface that interacts with and recruits diverse chromatin-associated factors. HP1 proteins rapidly evolve through sequence changes and gene duplications, but the extent of variation required to achieve functional specialization is unknown. To investigate how changes in amino acid sequence impact epigenetic inheritance, we performed a targeted mutagenesis screen of the dimerization and protein interaction domain of the S.pombe HP1 homolog Swi6. We discovered that substitutions mapping to an auxiliary motif in Swi6 outside the dimerization interface can lead to complete functional divergence. Specifically, we identified point mutations at a single amino acid residue that resulted in either persistent gain or loss of function in epigenetic inheritance without affecting heterochromatin establishment. These substitutions increase Swi6 chromatin occupancy in vivo and alter Swi6-protein interactions that selectively affect H3K9me inheritance. Based on our findings, we propose that relatively minor changes in Swi6 amino acid composition can lead to profound changes in epigenetic inheritance, underscoring the remarkable plasticity associated with HP1 proteins and their ability to evolve new functions.
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Project description:Both RNAi-dependent and -independent mechanisms have been implicated in the establishment of heterochromatin domains, which may be stabilized by feedback loops involving chromatin proteins and modifications of histones and DNA. Neurospora crassa sports features of heterochromatin found in higher eukaryotes, namely cytosine methylation (5mC), methylation of histone H3 lysine9 (H3K9me) and HETEROCHROMATIN PROTEIN-1 (HP1), and provides a model to investigate heterochromatin establishment and maintenance. We mapped the distribution of HP1, 5mC, H3K9me3 and H3K4me2 at 100bp-resolution and explored their interplay. HP1, H3K9me3 and DNA methylation were extensively colocalized and defined 44 heterochromatic domains on linkage group VII, all relics of repeat-induced point mutation (RIP). Interestingly, the centromere was found in a striking ~350kb heterochromatic domain with no detectable H3K4me2. 5mC was not found in genes, in contrast to the situation in plants and animals. H3K9me3 is required for HP1 localization and DNA methylation. Here, we show that localization of H3K9me3 is independent of 5mC or HP1 at virtually all heterochromatin regions. In addition, we observed complete restoration of DNA methylation patterns after depletion and reintroduction of the H3K9 methylation machinery, indicating that the signals for de novo heterochromatin formation lie upstream of H3K9 methylation. These data show that A:T rich RIPâd DNA efficently directs methylation of H3K9, which in turn, directs methylation of associated cytosines. Immunoprecipitation experiments using antibodies to 5mC, H3K9me3, epitope-tagged HP1, and H3K4me2 were performed. The immunoprecipitate fraction was labeled with Cy5 and the total input was labeled with Cy3. Samples were hybridized to a N. crassa LGVII tiling path microarray.
2010-05-15 | E-GEOD-12690 | biostudies-arrayexpress
Project description:The highly conserved multienzyme Rix1-containing complex (hereafter referred to as the rixosome), is required for ribosomal RNA (rRNA) processing and also localizes to heterochromatin in fission yeast, but its role in heterochromatin formation is unknown. Here we report the isolation of separation of function mutations in subunits of the rixosome that abolish its physical association with Swi6/HP1 and localization to heterochromatin, but do not affect growth or rRNA processing. These mutations abolish the epigenetic inheritance of silencing and histone H3 lysine 9 methylation (H3K9me), accumulate heterochromatic RNAs, and cannot spread H3K9me and silencing away from nucleation sites into an inserted transgene. We further show that the rixosome acts upstream of the conserved 5’-3’ exoribonuclease Dhp1/XRN2 to promote heterochromatic RNA degradation. These findings reveal a new RNA degradation pathway that specifically localizes to heterochromatin to degrade nascent transcripts and enable heterochromatin spreading and inheritance.
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Project description:Histone H3 trimethylation of lysine 9 (H3K9me3) and heterochromatin proteins 1 (HP1) are hallmarks of heterochromatin, a state of compacted DNA essential for genome stability and long-term transcriptional silencing. The mechanisms by which H3K9me3 and HP1 contribute to chromatin compaction have been speculative and controversial. We demonstrate that mammalian HP1β is a prototypic HP1 protein exemplifying most basal chromatin binding and effects. These are caused by dimeric and dynamic interaction with highly enriched H3K9me3 and are modulated by various electrostatic interfaces. Via internucleosomal bridging HP1β specifically interacts with condensed chromatin, which we postulate stabilizes the compacted state. In agreement, HP1β genome-wide localization follows enrichment of H3K9me3 and bridging of chromatin fibers in a cellular context is sufficient for maintaining heterochromatic conformation. Overall, our findings define a fundamental mechanism for chromatin higher order structural changes caused by HP1 proteins, which may contribute to the plastic nature of condensed chromatin.
2017-02-10 | GSE71114 | GEO
Project description:Both RNAi-dependent and -independent mechanisms have been implicated in the establishment of heterochromatin domains, which may be stabilized by feedback loops involving chromatin proteins and modifications of histones and DNA. Neurospora crassa sports features of heterochromatin found in higher eukaryotes, namely cytosine methylation (5mC), methylation of histone H3 lysine9 (H3K9me) and HETEROCHROMATIN PROTEIN-1 (HP1), and provides a model to investigate heterochromatin establishment and maintenance. We mapped the distribution of HP1, 5mC, H3K9me3 and H3K4me2 at 100bp-resolution and explored their interplay. HP1, H3K9me3 and DNA methylation were extensively colocalized and defined 44 heterochromatic domains on linkage group VII, all relics of repeat-induced point mutation (RIP). Interestingly, the centromere was found in a striking ~350kb heterochromatic domain with no detectable H3K4me2. 5mC was not found in genes, in contrast to the situation in plants and animals. H3K9me3 is required for HP1 localization and DNA methylation. Here, we show that localization of H3K9me3 is independent of 5mC or HP1 at virtually all heterochromatin regions. In addition, we observed complete restoration of DNA methylation patterns after depletion and reintroduction of the H3K9 methylation machinery, indicating that the signals for de novo heterochromatin formation lie upstream of H3K9 methylation. These data show that A:T rich RIP’d DNA efficently directs methylation of H3K9, which in turn, directs methylation of associated cytosines.
2008-12-01 | GSE12690 | GEO
Project description:Gene silencing via heterochromatin formation plays a major role in cell differentiation and maintenance of homeostasis. Here, we report the identification and characterization of a novel heterochromatinization factor in vertebrates, Bromo Adjacent Homology Domain-containing protein 1 (BAHD1). BAHD1 interacts with HP1, MBD1, HDAC5 and with several transcription factors. Through electron and immunofluorescence microscopy studies, we show that BAHD1 overexpression directs HP1 to specific nuclear sites and promotes formation of large heterochromatic domains, which lack acetyl histone H3 and are enriched in H3 trimethylated at lysine 27. Furthermore, ectopically expressed BAHD1 colocalizes with the heterochromatic X inactive chromosome. As highlighted by whole genome microarray analysis of BAHD1 knock down cells, BAHD1 represses several proliferation and survival genes and in particular, the insulin-like growth factor II gene (IGF2). BAHD1 specifically binds the CpG-rich P3 promoter of IGF2. This region contains DNA binding sequences for the transcription factor SP1, with which BAHD1 co-immunoprecipitates. Collectively, these findings provide evidence that BAHD1 acts as a silencer by recruiting proteins that coordinate heterochromatin assembly at specific sites in the genome. We used microarrays to identify BAHD1 gene targets. We compared the transcriptome profile of BAHD1 depleted cells with siRNA to that of cells treated with control siRNA. Experiment Overall Design: Six samples were analysed, including three biological replicates of control cells and three biological replicates of BAHD1 KD cells.
2009-08-07 | E-GEOD-16097 | biostudies-arrayexpress
Project description:Heterochromatin is a tightly packaged form of DNA that leads to permanent or temporal gene silencing. In P. falciparum heterochromatin is formed after trimethylation of lysine 9 on histone H3 and consequent binding of heterochromatin protein 1 (HP1). Genome-wide profiling studies established that in P. falciparum blood stage schizonts heterochromatin is formed at subtelomeres and some intra-chromosomal islands. Reversible silencing of genes located in these regions has been shown to be key to, among others, antigenic variation, invasion pathway selection or commitment to gametocytogenesis. However, heterochromatic gene silencing has not been investigated in many other Plasmodium species, strains or life cycle stages, yet. Here, we used ChIP-seq to profile HP1 occupancy in asexual parasites of six different species (P. falciparum, P. knowlesi, P. vivax, P. berghei, P. yoelii, and P. chabaudi) and of four different P. falciparum strains (3D7, PF2004, NF54, NF135) as well as two different P. knowlesi clones (A1C1, A1H1). Additionally, we performed HP1 ChIP-seq on three asexual stages (ring, trophozoite and schizont stage) and two sexual stages of P. falciparum parasites. Collectively, the generated HP1 profiles provide a detailed catalog of heterochromatic genes and reveal conserved and specialized features of epigenetic control at different life cycle stages, strains and species across the genus Plasmodium.
2018-01-16 | GSE102695 | GEO