Convergent evolution of chromatin modification by structurally distinct enzymes: comparative enzymology of histone H3 Lys27 methylation by human polycomb repressive complex 2 and vSET

2013 ◽  
Vol 453 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Brooke M. Swalm ◽  
Kenneth K. Hallenbeck ◽  
Christina R. Majer ◽  
Lei Jin ◽  
Margaret Porter Scott ◽  
...  

H3K27 (histone H3 Lys27) methylation is an important epigenetic modification that regulates gene transcription. In humans, EZH (enhancer of zeste homologue) 1 and EZH2 are the only enzymes capable of catalysing methylation of H3K27. There is great interest in understanding structure–function relationships for EZH2, as genetic alterations in this enzyme are thought to play a causal role in a number of human cancers. EZH2 is challenging to study because it is only active in the context of the multi-subunit PRC2 (polycomb repressive complex 2). vSET is a viral lysine methyltransferase that represents the smallest protein unit capable of catalysing H3K27 methylation. The crystal structure of this minimal catalytic protein has been solved and researchers have suggested that vSET might prove useful as an EZH2 surrogate for the development of active site-directed inhibitors. To test this proposition, we conducted comparative enzymatic analysis of human EZH2 and vSET and report that, although both enzymes share similar preferences for methylation of H3K27, they diverge in terms of their permissiveness for catalysing methylation of alternative histone lysine sites, their relative preferences for utilization of multimeric macromolecular substrates, their active site primary sequences and, most importantly, their sensitivity to inhibition by drug-like small molecules. The cumulative data led us to suggest that EZH2 and vSET have very distinct active site structures, despite the commonality of the reaction catalysed by the two enzymes. Hence, the EZH2 and vSET pair of enzymes represent an example of convergent evolution in which distinct structural solutions have developed to solve a common catalytic need.

Cancers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 796 ◽  
Author(s):  
Ratnakar Singh ◽  
Zeeshan Fazal ◽  
Andrea K. Corbet ◽  
Emmanuel Bikorimana ◽  
Jennifer C. Rodriguez ◽  
...  

A greater understanding of the hypersensitivity and curability of testicular germ cell tumors (TGCTs) has the potential to inform strategies to sensitize other solid tumors to conventional chemotherapies. The mechanisms of cisplatin hypersensitivity and resistance in embryonal carcinoma (EC), the stem cells of TGCTs, remain largely undefined. To study the mechanisms of cisplatin resistance we generated a large panel of independently derived, acquired resistant clones from three distinct parental EC models employing a protocol designed to match standard of care regimens of TGCT patients. Transcriptomics revealed highly significant expression changes shared between resistant cells regardless of their parental origin. This was dominated by a highly significant enrichment of genes normally repressed by H3K27 methylation and the polycomb repressive complex 2 (PRC2) which correlated with a substantial decrease in global H3K27me3, H2AK119 ubiquitination, and expression of BMI1. Importantly, repression of H3K27 methylation with the EZH2 inhibitor GSK-126 conferred cisplatin resistance to parental cells while induction of H3K27 methylation with the histone lysine demethylase inhibitor GSK-J4 resulted in increased cisplatin sensitivity to resistant cells. A gene signature based on H3K27me gene enrichment was associated with an increased rate of recurrent/progressive disease in testicular cancer patients. Our data indicates that repression of H3K27 methylation is a mechanism of cisplatin acquired resistance in TGCTs and that restoration of PRC2 complex function is a viable approach to overcome treatment failure.


2019 ◽  
Vol 5 (7) ◽  
pp. eaax2887 ◽  
Author(s):  
Andrea Piunti ◽  
Edwin R. Smith ◽  
Marc A. J. Morgan ◽  
Michal Ugarenko ◽  
Natalia Khaltyan ◽  
...  

Using biochemical characterization of fusion proteins associated with endometrial stromal sarcoma, we identified JAZF1 as a new subunit of the NuA4 acetyltransferase complex and CXORF67 as a subunit of the Polycomb Repressive Complex 2 (PRC2). Since CXORF67’s interaction with PRC2 leads to decreased PRC2-dependent H3K27me2/3 deposition, we propose a new name for this gene:CATACOMB(catalytic antagonist of Polycomb; official gene name:EZHIP). We mapCATACOMB’sinhibitory function to a short highly conserved region and identify a single methionine residue essential for diminution of H3K27me2/3 levels. Remarkably, the amino acid sequence surrounding this critical methionine resembles the oncogenic histone H3 Lys27-to-methionine (H3K27M) mutation found in high-grade pediatric gliomas. AsCATACOMBexpression is regulated through DNA methylation/demethylation, we proposeCATACOMBas the potential interlocutor between DNA methylation and PRC2 activity. We raise the possibility that similar regulatory mechanisms could exist for other methyltransferase complexes such as Trithorax/COMPASS.


Author(s):  
Abigail J. Courtney ◽  
Masayuki Kamei ◽  
Aileen R. Ferraro ◽  
Kexin Gai ◽  
Qun He ◽  
...  

ABSTRACTNeurospora crassa contains a minimal Polycomb repression system, which provides rich opportunities to explore Polycomb-mediated repression across eukaryotes and enables genetic studies that can be difficult in plant and animal systems. Polycomb Repressive Complex 2 is a multi-subunit complex that deposits mono-, di-, and tri-methyl groups on lysine 27 of histone H3, and tri-methyl H3K27 is a molecular marker of transcriptionally repressed facultative heterochromatin. In mouse embryonic stem cells and multiple plant species, H2A.Z has been found to be co-localized with H3K27 methylation. H2A.Z is required for normal H3K27 methylation in these experimental systems, though the regulatory mechanisms are not well understood. We report here that Neurospora crassa mutants lacking H2A.Z or SWR-1, the ATP-dependent histone variant exchanger, exhibit a striking reduction in levels of H3K27 methylation. RNA-sequencing revealed downregulation of eed, encoding a subunit of PRC2, in an hH2Az mutant compared to wild type and overexpression of EED in a ΔhH2Az;Δeed background restored most H3K27 methylation. Reduced eed expression leads to region-specific losses of H3K27 methylation suggesting that EED-dependent mechanisms are critical for normal H3K27 methylation at certain regions in the genome.AUTHOR SUMMARYEukaryotic DNA is packaged with histone proteins to form a DNA-protein complex called chromatin. Inside the nucleus, chromatin can be assembled into a variety of higher-order structures that profoundly impact gene expression. Polycomb Group proteins are important chromatin regulators that control assembly of a highly condensed form of chromatin. The functions of Polycomb Group proteins are critical for maintaining stable gene repression during development of multicellular organisms, and defects in Polycomb proteins are linked to disease. There is significant interest in elucidating the molecular mechanisms that regulate the activities of Polycomb Group proteins and the assembly of transcriptionally repressed chromatin domains. In this study, we used a model fungus to investigate the regulatory relationship between a histone variant, H2A.Z, and a conserved histone modifying enzyme complex, Polycomb Repressive Complex 2 (PRC2). We found that H2A.Z is required for normal expression of a PRC2 component. Mutants that lack H2A.Z have defects in chromatin structure at some parts of the genome, but not others. Identification of PRC2-target domains that are differentially dependent on EED provides insights into the diverse mechanisms that regulate assembly and maintenance of facultative heterochromatin in a simple model system.Data Reference NumbersGSE146611


2021 ◽  
Author(s):  
Kai-Lu Liu ◽  
KongKai Zhu ◽  
Hua Zhang

The polycomb repressive complex 2 (PRC2) catalyzes the methylation of histone H3 lysine 27 (H3K27) and the enrichment of its catalytic product H3K27me3 is responsible for the silencing of tumor...


2021 ◽  
Author(s):  
Weipeng Mu ◽  
Noel S Murcia ◽  
Keriayn N. Smith ◽  
Debashish U Menon ◽  
Della Yee ◽  
...  

AbstractRBBP4 is a core subunit of polycomb repressive complex 2 (PRC2) and HDAC1/2-containing complexes, which are responsible for histone H3 lysine 27 (H3K27) methylation and deacetylation respectively. However, the mechanisms by which RBBP4 modulates the functions of these complexes remain largely unknown. We generated viable mouse embryonic stem cell lines with RBBP4 mutations that disturbed methylation and acetylation of H3K27 on target chromatin and found that RBBP4 is required for PRC2 assembly and H3K27me3 establishment on target chromatin. Moreover, in the absence of EED and SUZ12, RBBP4 maintained chromatin binding on PRC2 loci, suggesting that the pre-existence of RBBP4 on nucleosomes serves to recruit PRC2 to restore H3K27me3 on newly synthesized histones. As such, disruption of RBBP4 function led to dramatic changes in transcriptional profiles. In spite of the PRC2 association, we found that transcriptional changes were more closely tied to the deregulation of H3K27ac rather than H3K27me3 where increased levels of H3K27ac were found on numerous cis-regulatory elements, especially putative enhancers. These data suggest that RBBP4 controls acetylation levels by adjusting the activity of HDAC complexes. As histone methylation and acetylation have been implicated in cancer and neural disease, RBBP4 could serve as a potential target for disease treatment.


2019 ◽  
Author(s):  
Elizabeth T. Wiles ◽  
Kevin J. McNaught ◽  
Saumya M. De Silva ◽  
Gurmeet Kaur ◽  
Jeanne M. Selker ◽  
...  

AbstractMethylation of histone H3 lysine 27 (H3K27) is widely recognized as a transcriptionally repressive chromatin modification but the mechanism of repression remains unclear. We devised and implemented a forward genetic scheme to identify factors required for H3K27 methylation-mediated silencing in the filamentous fungus Neurospora crassa and identified a bromo-adjacent homology (BAH)-plant homeodomain (PHD)-containing protein, EPR-1 (Effector of Polycomb Repression 1; NCU07505). EPR-1 associates with H3K27 methylation in vivo and in vitro, and loss of EPR-1 de-represses H3K27-methylated genes without loss of H3K27 methylation. EPR-1 is not fungal-specific; orthologs of EPR-1 are present in a diverse array of eukaryotic lineages, suggesting an ancestral EPR-1 was a component of a primitive Polycomb repression pathway.SignificancePolycomb group (PcG) proteins are employed by a wide variety of eukaryotes for the maintenance of gene repression. Polycomb repressive complex 2 (PRC2), a multimeric complex of PcG proteins, catalyzes the methylation of histone H3 lysine 27 (H3K27). In the filamentous fungus, Neurospora crassa, H3K27 methylation represses scores of genes, despite the absence of canonical H3K27 methylation effectors that are present in plants and animals. We report the identification and characterization of an H3K27 methylation effector, EPR-1, in N. crassa and demonstrate its widespread presence and early eukaryotic origins with phylogenetic analyses. These findings indicate that an ancient EPR-1 may have been part of a nascent Polycomb repression system in eukaryotes.


2020 ◽  
Author(s):  
Hikaru Sato ◽  
Juan Santos-González ◽  
Claudia Köhler

AbstractPolycomb Repressive Complex 2 (PRC2)-mediated trimethylation of histone H3 on lysine 27 (H3K27me3) and methylation of histone 3 on lysine 9 (H3K9me) are two repressive epigenetic modifications that are typically localized in distinct regions of the genome. For reasons unknown, however, they co-occur in some organisms and special tissue types. In this study, we show that maternal alleles marked by H3K27me3 in the Arabidopsis endosperm were targeted by the H3K27me3 demethylase REF6 and became activated during germination. In contrast, maternal alleles marked by H3K27me3, H3K9me2, and CHGm were protected from REF6 targeting and remained silenced. Our study unveils that combinations of different repressive epigenetic modifications time a key adaptive trait by modulating access of REF6.


2014 ◽  
Vol 53 (2) ◽  
pp. 277-289 ◽  
Author(s):  
Chiara Mozzetta ◽  
Julien Pontis ◽  
Lauriane Fritsch ◽  
Philippe Robin ◽  
Manuela Portoso ◽  
...  

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