Similar Datasets
Project description:Rewriting of the epigenome has risen as a promising alternative to gene editing for precision medicine. In nature, epigenetic silencing can result in complete attenuation of target gene expression over multiple mitotic divisions. However, persistent repression has been difficult to achieve using targeted systems. Here, we report that robust and persistent epigenetic memory required both a DNA methyltransferase (DNMT3A-dCas9) and a histone methyltransferase (Ezh2-dCas9 or KRAB-dCas9). DNMT3A-dCas9 was dependent on full-length DNMT3L for maximal activity. Co-targeting with Ezh2-dCas9, DNMT3A-dCas9 and DNMT3L induced long-term HER2 repression over at least 50 days and maintained a heterochromatic environment. Interestingly, substitution of Ezh2-dCas9 for KRAB-dCas9 enabled long-term repression at some target genes (e.g., SNURF) but not at HER2, at which H3K9me3 and DNA methylation were transiently acquired and subsequently lost. Off-target DNA hypermethylation occurred at many individual CpG sites but rarely at multiple CpGs in a single promoter, consistent with no detectable effect on transcription at the loci tested. Conversely, robust hypermethylation was observed at HER2. These data demonstrate that targeting different combinations of histone and DNA methyltransferases is required to achieve maximal repression at different loci in the same cell, or the same locus in different cells.
2019-05-07 | GSE123830 | GEO
Project description:Rewriting of the epigenome has risen as a promising alternative to gene editing for precision medicine. In nature, epigenetic silencing can result in complete attenuation of target gene expression over multiple mitotic divisions. However, persistent repression has been difficult to achieve using targeted systems. Here, we report that robust and persistent epigenetic memory required both a DNA methyltransferase (DNMT3A-dCas9) and a histone methyltransferase (Ezh2-dCas9 or KRAB-dCas9). DNMT3A-dCas9 was dependent on full-length DNMT3L for maximal activity. Co-targeting with Ezh2-dCas9, DNMT3A-dCas9 and DNMT3L induced long-term HER2 repression over at least 50 days and maintained a heterochromatic environment. Interestingly, substitution of Ezh2-dCas9 for KRAB-dCas9 enabled long-term repression at some target genes (e.g., SNURF) but not at HER2, at which H3K9me3 and DNA methylation were transiently acquired and subsequently lost. Off-target DNA hypermethylation occurred at many individual CpG sites but rarely at multiple CpGs in a single promoter, consistent with no detectable effect on transcription at the loci tested. Conversely, robust hypermethylation was observed at HER2. These data demonstrate that targeting different combinations of histone and DNA methyltransferases is required to achieve maximal repression at different loci in the same cell, or the same locus in different cells.
2019-05-07 | GSE123882 | GEO
Project description:Engineering epigenetic memory requires co-targeting of histone methylatransferases and DNA methylatransferases
| PRJNA510116 | ENA
Project description:Engineering epigenetic memory requires co-targeting of histone methylatransferases and DNA methylatransferases [Methylation]
| PRJNA510108 | ENA
Project description:Engineering epigenetic memory requires co-targeting of histone methylatransferases and DNA methylatransferases [ChIP-seq]
| PRJNA510113 | ENA
Project description:Heterochromatic gene silencing is an important form of gene regulation that usually requires specific histone modifications. A popular model posits that inheritance of modified histones, especially in the form of H3-H4 tetramers, underlies inheritance of heterochromatin. Because H3-H4 tetramers are randomly distributed between daughter chromatids during DNA replication, rare occurrences of asymmetric tetramer inheritance within a heterochromatic domain would have the potential to destabilize heterochromatin. This model makes a prediction that shorter heterochromatic domains would experience unbalanced tetramer inheritance more frequently, and thereby be less stable. In contrast to this prediction, we found that shortening a heterochromatic domain in Saccharomyces had no impact on the strength of silencing nor its heritability. Additionally, we found that replisome mutations that disrupt inheritance of H3-H4 tetramers had only minor effects on heterochromatin stability. These findings suggest that histones carry little or no memory of the heterochromatin state through DNA replication.
| S-EPMC6850775 | biostudies-literature
Project description:Synthetic lethality strategies are likely to be integrated in effective and specific cancer treatments. These strategies combine different specific targets, either in similar or cooperating pathways. Chromatin remodeling underlies, directly or indirectly, all processes of tumor biology. In this context, the combined targeting of proteins associated with different aspects of chromatin remodeling can be exploited to find new alternative targets or to improve treatment for specific individual tumors or patients. There are two major types of proteins, epigenetic modifiers of histones and nuclear or chromatin kinases, all of which are druggable targets. Among epigenetic enzymes, there are four major families: histones acetylases, deacetylases, methylases and demethylases. All these enzymes are druggable. Among chromatin kinases are those associated with DNA damage responses, such as Aurora A/B, Haspin, ATM, ATR, DNA-PK and VRK1-a nucleosomal histone kinase. All these proteins converge on the dynamic regulation chromatin organization, and its functions condition the tumor cell viability. Therefore, the combined targeting of these epigenetic enzymes, in synthetic lethality strategies, can sensitize tumor cells to toxic DNA-damage-based treatments, reducing their toxicity and the selective pressure for tumor resistance and increasing their immunogenicity, which will lead to an improvement in disease-free survival and quality of life.
| S-EPMC9406467 | biostudies-literature
Project description:Eukaryotic genomes must maintain stable inheritance of epigenetic states. In plants, DNA methylation patterns are faithfully inherited over many generations but it is unknown how the dynamic activities of cytosine DNA methyltransferases and 5-methylcytosine DNA glycosylases, which remove 5-methylcytosine by base excision repair, interact to maintain epigenetic homeostasis. Here we show that a methylation-sensing gene regulatory circuit centered on a 5-methylcytosine DNA glycosylase gene is required for long-term epigenetic fidelity in Arabidopsis. Disrupting this circuit causes widespread methylation losses and abnormal phenotypes that progressively worsen over generations. In heterochromatin, these losses are counteracted such that methylation returns to a normal level over four generations. However, thousands of loci in euchromatin progressively lose DNA methylation between generations and remain unmethylated. We conclude that actively maintained equilibrium between methylation and demethylation activities is required to ensure long-term stable inheritance of epigenetic information.
2017-12-01 | GSE104240 | GEO
Project description:Pathogens have developed sophisticated strategies to evade the immune response, among which manipulation of host cellular epigenetic mechanisms plays a prominent role. In the last decade, modulation of histone acetylation in host cells has emerged as an efficient strategy of bacterial immune evasion. Virulence factors and metabolic products of pathogenic microorganisms alter expression and activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs) to suppress transcription of host defense genes through epigenetic changes in histone acetylation marks. This new avenue of pathogen-host interactions is particularly important in light of introduction of HDAC inhibitors into clinical practice. Considerable effort is currently being applied to better understand the effects of HDAC inhibitors on the quality of immune responses to pathogens and to characterize the therapeutic potential of these compounds in microbial infections. In this review, we will discuss the recently discovered mechanisms utilized by bacteria to facilitate their survival within infected hosts through subversion of the host acetylation system and the effects of acetylation modulators, including HDAC inhibitors and bromodomain-containing BET protein inhibitors, on innate immune responses against microbial pathogens. Integration of these two lines of experimental evidence provides critical information on the perspectives of epigenetic therapies targeting protein acetylation in infectious diseases.
| S-EPMC6109591 | biostudies-literature
Project description:Human kinetochores are transcriptionally active, producing very low levels of transcripts of the underlying alpha-satellite DNA. However, it is not known whether kinetochores can tolerate acetylated chromatin and the levels of transcription that are characteristic of housekeeping genes, or whether kinetochore-associated 'centrochromatin', despite being transcribed at a low level, is essentially a form of repressive chromatin. Here, we have engineered two types of acetylated chromatin within the centromere of a synthetic human artificial chromosome. Tethering a minimal NF-?B p65 activation domain within kinetochore-associated chromatin produced chromatin with high levels of histone H3 acetylated on lysine 9 (H3K9ac) and an ~10-fold elevation in transcript levels, but had no substantial effect on kinetochore assembly or function. By contrast, tethering the herpes virus VP16 activation domain produced similar modifications in the chromatin but resulted in an ~150-fold elevation in transcripts, approaching the level of transcription of an endogenous housekeeping gene. This rapidly inactivated kinetochores, causing a loss of assembled CENP-A and blocking further CENP-A assembly. Our data reveal that functional centromeres in vivo show a remarkable plasticity--kinetochores tolerate profound changes to their chromatin environment, but appear to be critically sensitive to the level of centromeric transcription.
| S-EPMC3283876 | biostudies-other