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H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [RNA-seq]

ABSTRACT: Although it is well established that Polycomb Group (PcG) complexes maintain gene repression through the incorporation of H2AK121ub and H3K27me3, little is known about the effect of these modifications on chromatin, which is fundamental to understand PcG function. Here, by integrating chromatin accessibility, histone marks and expression analyses in different Arabidopsis PcG mutants, we show that H2AK121ub marking favors a less accessible but still permissive chromatin at transcriptional regulation hotspots, which can be further reduced by EMF1 and H3K27me3. We found that when acting concurrently, H2AK121ub and H3K27me3 establish an inaccessible but responsive chromatin to marks levels, allowing gene reprograming. Conversely, when H3K27me3 is alone, chromatin is less responsive, indicating that H2AK121ub-marked hotspots are required for transcriptional responses. Interestingly, despite the loss of H2AK121ub and H3K27me3 leads to increased chromatin accessibility, this is not necessarily accompanied by transcriptional activation, indicating that gene expression is not always predictive of accessible chromatin.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE154697 | GEO | 2020/12/02

REPOSITORIES: GEO

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H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [ChIP-seq]

Project description:Although it is well established that Polycomb Group (PcG) complexes maintain gene repression through the incorporation of H2AK121ub and H3K27me3, little is known about the effect of these modifications on chromatin, which is fundamental to understand PcG function. Here, by integrating chromatin accessibility, histone marks and expression analyses in different Arabidopsis PcG mutants, we show that H2AK121ub marking favors a less accessible but still permissive chromatin at transcriptional regulation hotspots, which can be further reduced by EMF1 and H3K27me3. We found that when acting concurrently, H2AK121ub and H3K27me3 establish an inaccessible but responsive chromatin to marks levels, allowing gene reprograming. Conversely, when H3K27me3 is alone, chromatin is less responsive, indicating that H2AK121ub-marked hotspots are required for transcriptional responses. Interestingly, despite the loss of H2AK121ub and H3K27me3 leads to increased chromatin accessibility, this is not necessarily accompanied by transcriptional activation, indicating that gene expression is not always predictive of accessible chromatin.

2020-12-02 | GSE154696 | GEO

H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [ATAC-seq]

2020-12-02 | GSE154695 | GEO

H2AK121ub and H3K27me3 marks have different effects on nucleosome organization in Arabidopsis

Project description:Background: Nucleosome organization within chromatin can be altered through the incorporation of histone modifications that in turn affects gene expression. Accordingly, the Polycomb Group (PcG) complexes PRC1 and PRC2 through the incorporation of H2AK121ub and H3K27me3 marks, respectively, maintain the repression of target genes; however, little is known about the exact function of these modifications in shaping nucleosome array at target genes, especially in plants. Results: By using two different MNase-seq datasets we analyzed the nucleosome occupancy profile of different PcG target genes in Arabidopsis. We found that PcG targets strongly differ in their nucleosome organization depending on the marks that they carry. Our data indicate that H2AK121ub marks play a role in fine-tuning +1 nucleosome position, while H3K27me3 marks impact nucleosome spacing and chromatin accessibility at both promoter and gene regions. Furthermore, analyzing the nucleosome profile of transcriptionally active PcG target genes in WT seedlings we found that their apparent activated state may be actually due to transcriptional heterogeneity across different cells. Conclusion: Our findings show that H2AK121ub and H3K27me3 marks differentially affect nucleosome organization in Arabidopsis, displaying additive effects when co-localizing at target genes.

2022-02-02 | GSE135978 | GEO

EMF1 and PRC2 Cooperate to Repress Key Regulators of Arabidopsis Development

Project description:EMBRYONIC FLOWER1 (EMF1) is a plant specific gene crucial to Arabidopsis vegetative development. Loss of function mutants in the EMF1 gene mimic the phenotype caused by mutations in Polycomb Group protein (PcG) genes, which encode epigenetic repressors that regulate many aspects of eukaryotic development. In Arabidopsis, Polycomb Repressor Complex 2 (PRC2), made of PcG proteins, catalyzes trimethylation of lysine 27 on histone H3 (H3K27me3) and PRC1-like proteins catalyze H2AK119 ubiquitination. Despite functional similarity to PcG proteins, EMF1 lacks sequence homology with known PcG proteins; thus its role in the PcG mechanism is unclear. To study the EMF1 functions and its mechanism of action, we performed genome-wide mapping of EMF1 binding and H3K27me3 modification sites in Arabidopsis seedlings. The EMF1 binding pattern is similar to that of H3K27me3 modification on the chromosomal and genic level. ChIPOTLe peak finding and clustering analyses both show that the highly trimethylated genes also have high enrichment level of EMF1 binding, termed EMF1_K27 genes. EMF1 interacts with regulatory genes, which are silenced to allow vegetative growth, and with genes specifying differentiated cell fates during vegetative development. H3K27me3 marks not only these genes but also some genes that are involved in endosperm development and maternal effects. Transcriptome analysis, coupled with the H3K27me3 pattern, of EMF1_K27 genes in emf1 and PRC2 mutants showed that EMF1 represses gene activities via diverse mechanisms and plays a novel role in the PcG mechanism. All experiments were done using two channels per chip, comparing DNA associated with immunoprecipitated EMF1 to control genomic DNA, DNA associated with immunoprecipitated histone H3 methylated at lysine 27 to control genomic DNA, or total RNA (converted to cDNA) to control genomic DNA. Two or three replicates per experiment are included.

2012-03-01 | E-GEOD-34689 | biostudies-arrayexpress

EMF1 and PRC2 Cooperate to Repress Key Regulators of Arabidopsis Development

2012-03-01 | GSE34689 | GEO

H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots

Project description:H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots

| PRJNA649545 | ENA

H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [ATAC-seq]

Project description:H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [ATAC-seq]

| PRJNA647212 | ENA

H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [RNA-seq]

Project description:H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [RNA-seq]

| PRJNA647214 | ENA

H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [ChIP-seq]

Project description:H2AK121ub in Arabidopsis favors a less accessible chromatin state at transcriptional regulation hotspots [ChIP-seq]

| PRJNA647213 | ENA

H2A monoubiquitination in Arabidopsis is generally independent of LHP1 and PRC2 activity [ChIP-seq]

Project description:BACKGROUND: Polycomb group complexes PRC1 and PRC2 repress gene expression at the chromatin level in eukaryotes. The classic recruitment model of Polycomb group complexes in which PRC2-mediated H3K27 trimethylation recruits PRC1 for H2A monoubiquitination was recently challenged by data showing that PRC1 activity can also recruit PRC2. However, the prevalence of these two mechanisms is unknown, especially in plants as H2AK121ub marks were examined at only a handful of Polycomb group targets. RESULTS: By using genome-wide analyses, we show that H2AK121ub marks are surprisingly widespread in Arabidopsis thaliana, often co-localizing with H3K27me3 but also occupying a set of transcriptionally active genes devoid of H3K27me3. Furthermore, by profiling H2AK121ub and H3K27me3 marks in atbmi1a/b/c, clf/swn, and lhp1 mutants we found that PRC2 activity is not required for H2AK121ub marking at most genes. In contrast, loss of AtBMI1 function impacts the incorporation of H3K27me3 marks at most Polycomb group targets. CONCLUSIONS: Our findings show the relationship between H2AK121ub and H3K27me3 marks across the A. thaliana genome and unveil that ubiquitination by PRC1 is largely independent of PRC2 activity in plants, while the inverse is true for H3K27 trimethylation.

2017-03-21 | GSE89357 | GEO

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