The spatial organization of the cell nucleus into separated domains with a specific macromolecular composition seems to be the fundamental principle that regulates its functioning. Because of the importance of regulation at the nuclear level, the cell nucleus and its domains have been intensively studied. This review is focused on the nuclear domain termed the Polycomb (PcG) body. We summarize and discuss data reported in the literature on different components of the PcG body that could form its structural basis. First, we describe the protein nature of the PcG body and the gene silencing factory model. Second, we review the target genes of Polycomb-mediated silencing and discuss their essentiality for the structural nature of the PcG body. In this respect, two different schematic models are presented. Third, we mention new data on the importance of RNAs, insulator elements and insulator proteins for the structure of PcG bodies. With this review, we hope to illustrate the importance of understanding the nature of the PcG subcompartment. The structural basis of a subcompartment directly reflects its status in the cell nucleus and the mechanism of its function.

• MeSH
• lidé MeSH
• polycomb proteiny chemie   MeSH
• struktury buněčného jádra metabolismus   ultrastruktura   MeSH
• subcelulární frakce metabolismus   MeSH
• umlčování genů MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• polycomb proteiny MeSH

BACKGROUND INFORMATION: A Polycomb (PcG) body is an orphan nuclear subcompartment characterised by accumulations of Polycomb repressive complex 1 (PRC1) proteins. However, seemingly contradictory reports have appeared that describe the PcG bodies either as protein-based bodies in the interchromatin compartment or chromatin domains. In this respect, molecular crowding is an important factor for the assembly and stability of nuclear subcompartments. In order to settle this contradiction, crowding experiments, that represent a convenient model distinguishing between interchromatin and chromatin compartments, were carried out. RESULTS: In sucrose-hypertonically induced crowding, we observed in U-2 OS cells that PcG bodies disappeared, but persisted as nuclear domains characterised by accumulations of DNA. This phenomenon was also observed in cells hypertonically treated with sorbitol and NaCl. Importantly, the observed changes were quickly reversible after re-incubation of cells in normal medium. We found that the PcG foci disappearance and the dissociation of PRC1 proteins (BMI1 and RING1a proteins) from chromatin were associated with their hyper-phosphorylation. In addition, under hyper- and hypotonic conditions, the behaviour of the PcG bodies differed from that of the typical nucleoplasmic body. CONCLUSION: PRC1 proteins accumulations do not represent a genuine nuclear subcompartment. The PcG body is a chromosomal domain, rather than a nucleoplasmic body.

• Klíčová slova
• Molecular crowding, Nuclear subcompartments, Polycomb body, Polycomb group proteins, Post-translational chromatin modifications,
• MeSH
• anthrachinony metabolismus   MeSH
• barvení a značení MeSH
• chromatin metabolismus   MeSH
• fluorescence MeSH
• fosforylace účinky léků   MeSH
• genetická transkripce účinky léků   MeSH
• hypertonické roztoky farmakologie   MeSH
• lidé MeSH
• makromolekulární látky metabolismus   MeSH
• nádorové buněčné linie MeSH
• polycomb proteiny metabolismus   MeSH
• PRC1 metabolismus   MeSH
• RNA genetika   metabolismus   MeSH
• sacharosa farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 1,5-bis((2-(methylamino)ethyl)amino)-4,8-dihydroxyanthracene-9,10-dione MeSH Prohlížeč
• anthrachinony MeSH
• BMI1 protein, human MeSH Prohlížeč
• chromatin MeSH
• hypertonické roztoky MeSH
• makromolekulární látky MeSH
• polycomb proteiny MeSH
• PRC1 MeSH
• RING1 protein, human MeSH Prohlížeč
• RNA MeSH
• sacharosa MeSH

BACKGROUND: Polycomb repressive complexes 1 and 2 play important roles in epigenetic gene regulation by posttranslationally modifying specific histone residues. Polycomb repressive complex 2 is responsible for the trimethylation of lysine 27 on histone H3; Polycomb repressive complex 1 catalyzes the monoubiquitination of histone H2A at lysine 119. Both complexes have been thoroughly studied in Arabidopsis, but the evolution of polycomb group gene families in monocots, particularly those with complex allopolyploid origins, is unknown. RESULTS: Here, we present the in silico identification of the Polycomb repressive complex 1 and 2 (PRC2, PRC1) subunits in allohexaploid bread wheat, the reconstruction of their evolutionary history and a transcriptional analysis over a series of 33 developmental stages. We identified four main subunits of PRC2 [E(z), Su(z), FIE and MSI] and three main subunits of PRC1 (Pc, Psc and Sce) and determined their chromosomal locations. We found that most of the genes coding for subunit proteins are present as paralogs in bread wheat. Using bread wheat RNA-seq data from different tissues and developmental stages throughout plant ontogenesis revealed variable transcriptional activity for individual paralogs. Phylogenetic analysis showed a high level of protein conservation among temperate cereals. CONCLUSIONS: The identification and chromosomal location of the Polycomb repressive complex 1 and 2 core components in bread wheat may enable a deeper understanding of developmental processes, including vernalization, in commonly grown winter wheat.

• Klíčová slova
• Epigenetics, Histone methylation, PRC2, Polycomb repressive complex, Wheat,
• MeSH
• chromozomy rostlin MeSH
• fylogeneze MeSH
• mapování chromozomů MeSH
• molekulární evoluce MeSH
• počítačová simulace MeSH
• PRC1 genetika   MeSH
• PRC2 genetika   MeSH
• pšenice genetika   MeSH
• RNA rostlin MeSH
• sekvenování transkriptomu MeSH
• stanovení celkové genové exprese MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• PRC1 MeSH
• PRC2 MeSH
• RNA rostlin MeSH

Polycomb repressive complexes maintain transcriptional repression of genes encoding crucial developmental regulators through chromatin modification. Here we investigated the role of Polycomb repressive complex 2 (PRC2) in retinal development by inactivating its key components Eed and Ezh2. Conditional deletion of Ezh2 resulted in a partial loss of PRC2 function and accelerated differentiation of Müller glial cells. In contrast, inactivation of Eed led to the ablation of PRC2 function at early postnatal stage. Cell proliferation was reduced and retinal progenitor cells were significantly decreased in this mutant, which subsequently caused depletion of Müller glia, bipolar, and rod photoreceptor cells, primarily generated from postnatal retinal progenitor cells. Interestingly, the proportion of amacrine cells was dramatically increased at postnatal stages in the Eed-deficient retina. In accordance, multiple transcription factors controlling amacrine cell differentiation were upregulated. Furthermore, ChIP-seq analysis showed that these deregulated genes contained bivalent chromatin (H3K27me3+ H3K4me3+). Our results suggest that PRC2 is required for proliferation in order to maintain the retinal progenitor cells at postnatal stages and for retinal differentiation by controlling amacrine cell generation.

• Klíčová slova
• Differentiation, Eed, Polycomb, Retina,
• MeSH
• buněčná diferenciace fyziologie   MeSH
• chromatin metabolismus   MeSH
• EZH2 protein metabolismus   MeSH
• histony metabolismus   MeSH
• kmenové buňky cytologie   metabolismus   MeSH
• metylace MeSH
• myši MeSH
• neurogeneze MeSH
• neuroglie metabolismus   MeSH
• PRC2 metabolismus   MeSH
• proliferace buněk MeSH
• retina metabolismus   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• Eed protein, mouse MeSH Prohlížeč
• Ezh2 protein, mouse MeSH Prohlížeč
• EZH2 protein MeSH
• histony MeSH
• PRC2 MeSH

Polycomb repressive complex 2 (PRC2) represents a group of evolutionarily conserved multi-subunit complexes that repress gene transcription by introducing trimethylation of lysine 27 on histone 3 (H3K27me3). PRC2 activity is of key importance for cell identity specification and developmental phase transitions in animals and plants. The composition, biochemistry, and developmental function of PRC2 in animal and flowering plant model species are relatively well described. Recent evidence demonstrates the presence of PRC2 complexes in various eukaryotic supergroups, suggesting conservation of the complex and its function. Here, we provide an overview of the current understanding of PRC2-mediated repression in different representatives of eukaryotic supergroups with a focus on the green lineage. By comparison of PRC2 in different eukaryotes, we highlight the possible common and diverged features suggesting evolutionary implications and outline emerging questions and directions for future research of polycomb repression and its evolution.

• Klíčová slova
• H3K27me3, PRC2, SAR, algae, animal, evolution, fungi, green lineage, plant, polycomb,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Polycomb group (PcG) proteins of the Polycomb repressive complex 1 (PRC1) are found to be diffusely distributed in nuclei of cells from various species. However they can also be localized in intensely fluorescent foci, whether imaged using GFP fusions to proteins of PRC1 complex, or by conventional immunofluorescence microscopy. Such foci are termed PcG bodies, and are believed to be situated in the nuclear intechromatin compartment. However, an ultrastructural description of the PcG body has not been reported to date. To establish the ultrastructure of PcG bodies in human U-2 OS cells stably expressing recombinant polycomb BMI1-GFP protein, we used correlative light-electron microscopy (CLEM) implemented with high-pressure freezing, cryosubstitution and on-section labeling of BMI1 protein with immunogold. This approach allowed us to clearly identify fluorescent PcG bodies, not as distinct nuclear bodies, but as nuclear domains enriched in separated heterochromatin fascicles. Importantly, high-pressure freezing and cryosubstitution allowed for a high and clear-cut immunogold BMI1 labeling of heterochromatin structures throughout the nucleus. The density of immunogold labeled BMI1 in the heterochromatin fascicles corresponding to fluorescent "PcG bodies" did not differ from the density of labeling of heterochromatin fascicles outside of the "PcG bodies". Accordingly, an appearance of the fluorescent "PcG bodies" seems to reflect a local accumulation of the labeled heterochromatin structures in the investigated cells. The results of this study should allow expansion of the knowledge about the biological relevance of the "PcG bodies" in human cells.

• Klíčová slova
• BMI1 protein, PcG body, Polycomb group proteins, correlative light-electron microscopy, heterochromatin, high-pressure freezing, immunogold labeling,
• MeSH
• elektronová mikroskopie * MeSH
• heterochromatin metabolismus   MeSH
• imunohistochemie MeSH
• kryoprezervace MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• polycomb proteiny MeSH
• represorové proteiny chemie   metabolismus   MeSH
• světlo * MeSH
• tlak MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• heterochromatin MeSH
• polycomb proteiny MeSH
• represorové proteiny MeSH

The seed-to-seedling transition represents a key developmental and metabolic switch in plants. Catabolism of seed storage reserves fuels germination and early seedling emergence until photosynthesis is established. The seed-to-seedling developmental transition is controlled by Polycomb repressive complex 2 (PRC2). However, the coordination of PRC2 activity and its contribution to transcriptional reprogramming during seedling establishment remain unknown. By analyzing H3K27me3 re-distribution and changes in gene transcription in the shoot and root tissues of heterotrophic and photoautotrophic Arabidopsis (Arabidopsis thaliana) seedlings, we reveal 2 phases of PRC2-mediated gene repression. The first phase is independent of light and photosynthesis and results in the irreversible repression of the embryo maturation program, marked by heterotrophy and reserve storage molecule biosynthesis. The second phase is associated with the repression of metabolic pathways related to germination and early seedling emergence, and H3K27me3 deposition in this phase is sensitive to photosynthesis inhibition. We show that preventing the transcription of the PRC2-repressed glyoxylate cycle gene ISOCITRATE LYASE promotes the vegetative phase transition in PRC2-depleted plants. Our findings underscore a key role of PRC2-mediated transcriptional repression in the coordinated metabolic and developmental switches that occur during seedling emergence and emphasize the close connection between metabolic and developmental identities.

• MeSH
• Arabidopsis * genetika   metabolismus   růst a vývoj   fyziologie   MeSH
• autotrofní procesy MeSH
• fotosyntéza genetika   MeSH
• heterotrofní procesy genetika   MeSH
• histony metabolismus   MeSH
• klíčení genetika   MeSH
• PRC2 * metabolismus   genetika   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• regulace genové exprese u rostlin MeSH
• semena rostlinná genetika   růst a vývoj   metabolismus   MeSH
• semenáček * genetika   růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• histony MeSH
• PRC2 * MeSH
• proteiny huseníčku * MeSH

Polycomb group (PcG) proteins, organized into Polycomb bodies, are important regulatory components of epigenetic processes involved in the heritable transcriptional repression of target genes. Here, we asked whether acetylation can influence the nuclear arrangement and function of the BMI1 protein, a core component of the Polycomb group complex, PRC1. We used time-lapse confocal microscopy, micro-irradiation by UV laser (355 nm) and GFP technology to study the dynamics and function of the BMI1 protein. We observed that BMI1 was recruited to UV-damaged chromatin simultaneously with decreased lysine acetylation, followed by the recruitment of heterochromatin protein HP1β to micro-irradiated regions. Pronounced recruitment of BMI1 was rapid, with half-time τ = 15 sec; thus, BMI1 is likely involved in the initiation step leading to the recognition of UV-damaged sites. Histone hyperacetylation, stimulated by HDAC inhibitor TSA, suppression of transcription by actinomycin D, and ATP-depletion prevented increased accumulation of BMI1 to γH2AX-positive irradiated chromatin. Moreover, BMI1 had slight ability to recognize spontaneously occurring DNA breaks caused by other pathophysiological processes. Taken together, our data indicate that the dynamics of recognition of UV-damaged chromatin, and the nuclear arrangement of BMI1 protein can be influenced by acetylation and occur as an early event prior to the recruitment of HPβ to UV-irradiated chromatin.

• MeSH
• acetylace MeSH
• buněčné linie MeSH
• buňky 3T3 MeSH
• časosběrné zobrazování MeSH
• chromatin metabolismus   účinky záření   MeSH
• chromozomální proteiny, nehistonové genetika   metabolismus   MeSH
• FRAP MeSH
• histony metabolismus   MeSH
• homolog proteinu s chromoboxem 5 MeSH
• inhibitory histondeacetylas metabolismus   MeSH
• jaderné proteiny genetika   metabolismus   MeSH
• konfokální mikroskopie metody   MeSH
• kyseliny hydroxamové metabolismus   MeSH
• lidé MeSH
• myši MeSH
• polycomb proteiny MeSH
• poškození DNA MeSH
• PRC1 MeSH
• protoonkogenní proteiny genetika   metabolismus   MeSH
• rekombinantní fúzní proteiny genetika   metabolismus   MeSH
• represorové proteiny genetika   metabolismus   MeSH
• ultrafialové záření MeSH
• zelené fluorescenční proteiny genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• BMI1 protein, human MeSH Prohlížeč
• CBX1 protein, human MeSH Prohlížeč
• chromatin MeSH
• chromozomální proteiny, nehistonové MeSH
• histony MeSH
• homolog proteinu s chromoboxem 5 MeSH
• inhibitory histondeacetylas MeSH
• jaderné proteiny MeSH
• kyseliny hydroxamové MeSH
• polycomb proteiny MeSH
• PRC1 MeSH
• protoonkogenní proteiny MeSH
• rekombinantní fúzní proteiny MeSH
• represorové proteiny MeSH
• trichostatin A MeSH Prohlížeč
• zelené fluorescenční proteiny MeSH

Mutation of SMARCA4 (BRG1), the ATPase of BAF (mSWI/SNF) and PBAF complexes, contributes to a range of malignancies and neurologic disorders. Unfortunately, the effects of SMARCA4 missense mutations have remained uncertain. Here we show that SMARCA4 cancer missense mutations target conserved ATPase surfaces and disrupt the mechanochemical cycle of remodeling. We find that heterozygous expression of mutants alters the open chromatin landscape at thousands of sites across the genome. Loss of DNA accessibility does not directly overlap with Polycomb accumulation, but is enriched in 'A compartments' at active enhancers, which lose H3K27ac but not H3K4me1. Affected positions include hundreds of sites identified as superenhancers in many tissues. Dominant-negative mutation induces pro-oncogenic expression changes, including increased expression of Myc and its target genes. Together, our data suggest that disruption of enhancer accessibility represents a key source of altered function in disorders with SMARCA4 mutations in a wide variety of tissues.

• MeSH
• adenosintrifosfatasy metabolismus   MeSH
• chromatin chemie   MeSH
• DNA-helikasy genetika   MeSH
• dominantní geny * MeSH
• epigenomika MeSH
• genotyp MeSH
• heterozygot MeSH
• jaderné proteiny genetika   MeSH
• kultivační média MeSH
• lidé MeSH
• missense mutace MeSH
• multivariační analýza MeSH
• mutace * MeSH
• myší embryonální kmenové buňky cytologie   MeSH
• myši transgenní MeSH
• myši MeSH
• nádory genetika   MeSH
• polycomb proteiny genetika   MeSH
• restrukturace chromatinu MeSH
• sekvenční analýza RNA MeSH
• transkripční faktory genetika   MeSH
• zesilovače transkripce MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• adenosintrifosfatasy MeSH
• chromatin MeSH
• DNA-helikasy MeSH
• jaderné proteiny MeSH
• kultivační média MeSH
• polycomb proteiny MeSH
• SMARCA4 protein, human MeSH Prohlížeč
• transkripční faktory MeSH

While the pivotal role of linker histone H1 in shaping nucleosome organization is well established, its functional interplays with chromatin factors along the epigenome are just starting to emerge. Here we show that, in Arabidopsis, as in mammals, H1 occupies Polycomb Repressive Complex 2 (PRC2) target genes where it favors chromatin condensation and H3K27me3 deposition. We further show that, contrasting with its conserved function in PRC2 activation at genes, H1 selectively prevents H3K27me3 accumulation at telomeres and large pericentromeric interstitial telomeric repeat (ITR) domains by restricting DNA accessibility to Telomere Repeat Binding (TRB) proteins, a group of H1-related Myb factors mediating PRC2 cis recruitment. This study provides a mechanistic framework by which H1 avoids the formation of gigantic H3K27me3-rich domains at telomeric sequences and contributes to safeguard nucleus architecture.

• Klíčová slova
• 3D chromosome organization, Arabidopsis, CP: Molecular biology, CP: Plants, H3K27me3, Polycomb, TRB, Telomere Repeat Binding protein, chromatin accessibility, linker histone H1, telomere,
• MeSH
• Arabidopsis * genetika   metabolismus   MeSH
• chromatin MeSH
• histony metabolismus   MeSH
• PRC2 metabolismus   MeSH
• proteiny huseníčku * genetika   metabolismus   MeSH
• proteiny vázající telomery metabolismus   MeSH
• savci metabolismus   MeSH
• telomery genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• histony MeSH
• PRC2 MeSH
• proteiny huseníčku * MeSH
• proteiny vázající telomery MeSH