Chromatin modulation and gene regulation in plants: insight about PRC1 function

2018 ◽  
Vol 46 (4) ◽  
pp. 957-966 ◽  
Author(s):  
Qiannan Wang ◽  
Wen-Hui Shen
Keyword(s):  
Current Knowledge ◽  
Protein Complexes ◽  
Histone H3 ◽  
Short Review ◽  
Polycomb Group ◽  
Trithorax Group ◽  
The Core ◽  
Evolutionarily Conserved ◽  
Trithorax Group Proteins ◽  
Polycomb Repressive Complex 1

In plant and metazoan, Polycomb Group (PcG) proteins play key roles in regulating developmental processes by repression of gene expression. PcG proteins function as multi-protein complexes; among them the best characterized ones are Polycomb Repressive Complex 1 (PRC1) and PRC2. PRC2 catalyzes histone H3 lysine 27 trimethylation (H3K27me3), and PRC1 can bind H3K27me3 and catalyzes H2A monoubiquitination. While the PRC2 components and molecular functions are evolutionarily conserved, varied PRC1 complexes are found and they show high divergences between animals and plants. In addition to the core subunits, an exponentially increasing number of PRC1-associated factors have been identified in Arabidopsis thaliana. Recent studies have also unraveled cross-component interactions and intertwined roles of PRC1 and PRC2 in chromatin modulation. In addition, complexities of interactions and functions between PcG and Trithorax Group proteins have been observed. This short review summarizes up current knowledge to provide insight about repressive functional mechanism of PRC1 and its interplay with other factors.

Current understanding of plant Polycomb group proteins and the repressive histone H3 Lysine 27 trimethylation

2020 ◽  
Vol 48 (4) ◽  
pp. 1697-1706
Author(s):  
Huijun Jiao ◽  
Yuanyuan Xie ◽  
Zicong Li
Keyword(s):  
Gene Expression ◽  
Noncoding Rna ◽  
Molecular Mechanisms ◽  
Protein Complexes ◽  
Close Association ◽  
Histone H3 ◽  
Polycomb Group ◽  
Dynamic Regulation ◽  
Trithorax Group ◽  
Repressive Mark

Polycomb group (PcG) proteins are highly conserved chromatin-modifying complexes that implement gene silencing in higher eukaryotes. Thousands of genes and multiple developmental processes are regulated by PcG proteins. As the first chromatin modifier been identified in model plant Arabidopsis thaliana, the methyltransferase CURLY LEAF (CLF) and its catalyzed histone H3 Lysine 27 trimethylation (H3K27me3) have already become well-established paradigm in plant epigenetic study. Like in animals, PcG proteins mediate plant development and repress homeotic gene expression by antagonizing with trithorax group proteins. Recent researches have advanced our understanding on plant PcG proteins, including the plant-specific components of these well-conserved protein complexes, the close association with transcription factors and noncoding RNA for the spatial and temporal specificity, the dynamic regulation of the repressive mark H3K27me3 and the PcG-mediated chromatin conformation alterations in gene expression. In this review, we will summarize the molecular mechanisms of PcG-implemented gene repression and the relationship between H3K27me3 and another repressive mark histone H2A Lysine 121 mono-ubiquitination (H2A121ub) will also be discussed.

scholarly journals Polycomb and Trithorax Group Proteins: The Long Road from Mutations in Drosophila to Use in Medicine

Acta Naturae ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 66-85
Author(s):  
D. A. Chetverina ◽  
D. V. Lomaev ◽  
M. M. Erokhin
Keyword(s):  
Small Molecule ◽  
Small Molecule Inhibitors ◽  
Polycomb Group ◽  
Trithorax Group ◽  
Diagnosis And Therapy ◽  
Pathological Conditions ◽  
Multiple Genes ◽  
Number Of Factors ◽  
Evolutionarily Conserved ◽  
Trithorax Group Proteins

Polycomb group (PcG) and Trithorax group (TrxG) proteins are evolutionarily conserved factors responsible for the repression and activation of the transcription of multiple genes in Drosophila and mammals. Disruption of the PcG/TrxG expression is associated with many pathological conditions, including cancer, which makes them suitable targets for diagnosis and therapy in medicine. In this review, we focus on the major PcG and TrxG complexes, the mechanisms of PcG/TrxG action, and their recruitment to chromatin. We discuss the alterations associated with the dysfunction of a number of factors of these groups in oncology and the current strategies used to develop drugs based on small-molecule inhibitors.

Maintenance of the active and inactive states

2019 ◽  
pp. 80-92
Author(s):  
John C. Lucchesi
Keyword(s):  
Transcriptional Repression ◽  
Homologous Chromosome ◽  
Regulatory Region ◽  
Histone H3 ◽  
Epigenetic Modifications ◽  
Polycomb Group ◽  
Histone H2a ◽  
Trithorax Group ◽  
Non Coding Rnas ◽  
Somatic Pairing

The maintenance of a gene in an active or inactive state is carried out by epigenetic modifications of the histones and of the DNA itself. Two major classes of complexes (PRC1 and PRC2), containing Polycomb group (PcG) proteins mediate transcriptional repression. PRC2 trimethylates histone H3 at lysine 27, a modification that attracts PRC1 leading to the ubiquitination of histone H2A. Variant PRC1 complexes can be targeted first, and mono-ubiquitinated histone H2A recruits PRC2 complexes that serve as the target for canonical PRC1 complexes. PRC2 can be targeted to sites of repression by associating with long non-coding RNAs. Trithorax group (TrxG) proteins form complexes that counteract PcG-mediated repression. Some subunits of these complexes maintain and enhance transcription by carrying out different lysine methylations (H3K4me, H3K36me and H3K79me) that are associated with active gene function; other subunits remodel chromatin by displacing and repositioning nucleosomes. Additional effects on transcription are transvections, whereby somatic pairing allows the regulatory region of one allele of a gene to influence the activity of the promoter of the allele on the homologous chromosome

scholarly journals Functional characterization of human Polycomb-like 3 isoforms identifies them as components of distinct EZH2 protein complexes

2011 ◽  
Vol 434 (2) ◽  
pp. 333-342 ◽  
Author(s):  
Gaylor Boulay ◽  
Claire Rosnoblet ◽  
Cateline Guérardel ◽  
Pierre-Olivier Angrand ◽  
Dominique Leprince
Keyword(s):  
Cell Fate ◽  
Target Genes ◽  
Protein Complexes ◽  
Functional Characterization ◽  
Polycomb Group ◽  
Phd Finger ◽  
Reverse Transcription Pcr ◽  
Tudor Domain ◽  
Self Association ◽  
Polycomb Repressive Complex 1

PcG (Polycomb group) proteins are conserved transcriptional repressors essential to regulate cell fate and to maintain epigenetic cellular memory. They work in concert through two main families of chromatin-modifying complexes, PRC1 (Polycomb repressive complex 1) and PRC2–4. In Drosophila, PRC2 contains the H3K27 histone methyltransferase E(Z) whose trimethylation activity towards PcG target genes is stimulated by PCL (Polycomb-like). In the present study, we have examined hPCL3, one of its three human paralogues. Through alternative splicing, hPCL3 encodes a long isoform, hPCL3L, containing an N-terminal TUDOR domain and two PHDs (plant homeodomains) and a smaller isoform, hPCL3S, lacking the second PHD finger (PHD2). By quantitative reverse transcription–PCR analyses, we showed that both isoforms are widely co-expressed at high levels in medulloblastoma. By co-immunoprecipitation analyses, we demonstrated that both isoforms interact with EZH2 through their common TUDOR domain. However, the hPCL3L-specific PHD2 domain, which is better conserved than PHD1 in the PCL family, is also involved in this interaction and implicated in the self-association of hPCL3L. Finally, we have demonstrated that both hPCL3 isoforms are physically associated with EZH2, but in different complexes. Our results provide the first evidence that the two hPCL3 isoforms belong to different complexes and raise important questions about their relative functions, particularly in tumorigenesis.

scholarly journals Developmentally regulated alterations in Polycomb repressive complex 1 proteins on the inactive X chromosome

2004 ◽  
Vol 167 (6) ◽  
pp. 1025-1035 ◽  
Author(s):  
Kathrin Plath ◽  
Dale Talbot ◽  
Karien M. Hamer ◽  
Arie P. Otte ◽  
Thomas P. Yang ◽  
...  
Keyword(s):  
X Chromosome ◽  
Protein Complexes ◽  
Histone H3 ◽  
X Inactivation ◽  
Polycomb Group ◽  
Epigenetic Mark ◽  
Embryonic Cells ◽  
Developmentally Regulated ◽  
Inactive X Chromosome ◽  
Multistep Process

Polycomb group (PcG) proteins belonging to the polycomb (Pc) repressive complexes 1 and 2 (PRC1 and PRC2) maintain homeotic gene silencing. In Drosophila, PRC2 methylates histone H3 on lysine 27, and this epigenetic mark facilitates recruitment of PRC1. Mouse PRC2 (mPRC2) has been implicated in X inactivation, as mPRC2 proteins transiently accumulate on the inactive X chromosome (Xi) at the onset of X inactivation to methylate histone H3 lysine 27 (H3-K27). In this study, we demonstrate that mPRC1 proteins localize to the Xi, and that different mPRC1 proteins accumulate on the Xi during initiation and maintenance of X inactivation in embryonic cells. The Xi accumulation of mPRC1 proteins requires Xist RNA and is not solely regulated by the presence of H3-K27 methylation, as not all cells that exhibit this epigenetic mark on the Xi show Xi enrichment of mPRC1 proteins. Our results implicate mPRC1 in X inactivation and suggest that the regulated assembly of PcG protein complexes on the Xi contributes to this multistep process.

scholarly journals SMC proteins and chromosome mechanics: from bacteria to humans

2005 ◽  
Vol 360 (1455) ◽  
pp. 507-514 ◽  
Author(s):  
Tatsuya Hirano
Keyword(s):  
Protein Interactions ◽  
Protein Complexes ◽  
Related Protein ◽  
Protein Protein Interactions ◽  
The Core ◽  
Archaeal Species ◽  
Evolutionarily Conserved ◽  
Structural Maintenance Of Chromosomes ◽  
Mitosis And Meiosis ◽  
Smc Proteins

Chromosome cohesion and condensation are essential prerequisites of proper segregation of genomes during mitosis and meiosis, and are supported by two structurally related protein complexes, cohesin and condensin, respectively. At the core of the two complexes lie members of the structural maintenance of chromosomes (SMC) family of ATPases. SMC proteins are also found in most bacterial and archaeal species, implicating the existence of an evolutionarily conserved theme of higher-order chromosome organization and dynamics. SMC dimers adopt a two-armed structure with an ATP-binding cassette (ABC)-like domain at the distal end of each arm. This article reviews recent work on the bacterial and eukaryotic SMC protein complexes, and discusses current understanding of how these uniquely designed protein machines may work at a mechanistic level. It seems most likely that the action of SMC proteins is highly dynamic and plastic, possibly involving a diverse array of intramolecular and intermolecular protein–protein interactions.

scholarly journals PTE, a novel module to target Polycomb Repressive Complex 1 to the Cyclin D2 oncogene

2017 ◽  
Author(s):  
Sarina R. Cameron ◽  
Soumyadeep Nandi ◽  
Tatyana G. Kahn ◽  
Juan I. Barrasa ◽  
Per Stenberg ◽  
...  
Keyword(s):  
Cpg Island ◽  
Protein Complexes ◽  
Cpg Islands ◽  
Biochemical Properties ◽  
Polycomb Group ◽  
Cyclin D2 ◽  
Polycomb Response Element ◽  
Multiple Protein ◽  
Polycomb Repression ◽  
Polycomb Repressive Complex 1

AbstractPolycomb Group proteins are essential epigenetic repressors. They form multiple protein complexes of which two kinds, PRC1 and PRC2, are indispensable for repression. Although much is known about their biochemical properties, how PRC1 and PRC2 are targeted to specific genes is poorly understood. Here we establish the Cyclin D2 (CCND2) oncogene as a simple model to address this question. We provide the evidence that coordinated recruitment of PRC1 and PRC2 complexes to CCND2 involves a combination of a specialized PRC1 targeting element (PTE) and an adjacent CpG-island, which together act as a human Polycomb Response Element. Chromatin immunoprecipitation analysis of CCND2 in different transcriptional states indicates that histone modifications produced by PRC1 and PRC2 are not sufficient to recruit either of the complexes. However, catalytic activity of PRC2 helps to anchor PRC1 at the PTE. Our analyses suggest that coordinated targeting of PRC1 and PRC2 complexes by juxtaposed AT-rich PTEs and CpG-islands may be a general feature of Polycomb repression in mammals.

The Drosophila trithorax group proteins BRM, ASH1 and ASH2 are subunits of distinct protein complexes

Development ◽  
1998 ◽  
Vol 125 (20) ◽  
pp. 3955-3966 ◽  
Author(s):  
O. Papoulas ◽  
S.J. Beek ◽  
S.L. Moseley ◽  
C.M. McCallum ◽  
M. Sarte ◽  
...  
Keyword(s):  
Chromatin Remodeling ◽  
Protein Complexes ◽  
Dominant Negative ◽  
Homeotic Genes ◽  
Atpase Subunit ◽  
Trithorax Group ◽  
Chromatin Remodeling Complexes ◽  
Trithorax Group Proteins ◽  
Drosophila Embryos

The trithorax group gene brahma (brm) encodes an activator of Drosophila homeotic genes that functions as the ATPase subunit of a large protein complex. To determine if BRM physically interacts with other trithorax group proteins, we purified the BRM complex from Drosophila embryos and analyzed its subunit composition. The BRM complex contains at least seven major polypeptides. Surprisingly, the majority of the subunits of the BRM complex are not encoded by trithorax group genes. Furthermore, a screen for enhancers of a dominant-negative brm mutation identified only one trithorax group gene, moira (mor), that appears to be essential for brm function in vivo. Four of the subunits of the BRM complex are related to subunits of the yeast chromatin remodeling complexes SWI/SNF and RSC. The BRM complex is even more highly related to the human BRG1 and hBRM complexes, but lacks the subunit heterogeneity characteristic of these complexes. We present biochemical evidence for the existence of two additional complexes containing trithorax group proteins: a 2 MDa ASH1 complex and a 500 kDa ASH2 complex. These findings suggest that BRM plays a role in chromatin remodeling that is distinct from the function of most other trithorax group proteins.

Polycomb and Trithorax group protein-mediated control of stress responses in plants

2014 ◽  
Vol 395 (11) ◽  
pp. 1291-1300 ◽  
Author(s):  
Julia Anna Kleinmanns ◽  
Daniel Schubert
Keyword(s):  
Stress Responses ◽  
Current Knowledge ◽  
Epigenetic Inheritance ◽  
Polycomb Group ◽  
Gene Repression ◽  
Stable Gene ◽  
Trithorax Group ◽  
Stress Memory ◽  
Group Protein

Abstract A plant’s experience of abiotic or biotic stress can lead to stress memory in order to react faster and more efficiently to subsequent stresses. Molecularly, the memory of a stress can rely on stable inheritance through mitotic and meiotic cell divisions, thus epigenetic inheritance. The key epigenetic regulators are DNA cytosine methyltransferases and the Polycomb group (PcG) and Trithorax group (TrxG) proteins, which control numerous developmental processes. PcG and TrxG proteins act antagonistically on stable gene repression through mediating trimethylation of histone H3 lysine 27 (H3K27me3) and H3K4me3, respectively, and target thousands of genes in plants, including many genes responsive to stress. The role of PcG/TrxG proteins in regulating stress responses and memory, however, is just emerging. While it is well investigated that stress can induce changes of histone modifications at genes regulated by stress, it is largely unclear whether these changes are mitotically and/or meiotically heritable, hence confer somatic and/or transgenerational stress memory. As the literature on the role of DNA methylation in regulating stress responses has recently been extensively summarized, we focus this review on the current knowledge on the role of PcG and TrxG in stress responses and memory.

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