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Circadian rhythmicity of gene expression is a conserved feature of cell physiology. This involves fine-tuning between transcriptional and post-transcriptional mechanisms and strongly depends on the metabolic state of the cell. Together these processes guarantee an adaptive plasticity of tissue-specific genetic programs. However, it is unclear how the epigenome and RNA Pol II rhythmicity are integrated. Here we show that the PcG protein EZH1 has a gateway bridging function in postmitotic skeletal muscle cells. On the one hand, the circadian clock master regulator BMAL1 directly controls oscillatory behavior and periodic assembly of core components of the PRC2-EZH1 complex. On the other hand, EZH1 is essential for circadian gene expression at alternate Zeitgeber times, through stabilization of RNA Polymerase II preinitiation complexes, thereby controlling nascent transcription. Collectively, our data show that PRC2-EZH1 regulates circadian transcription both negatively and positively by modulating chromatin states and basal transcription complex stability.

Isoform 1 of DNA methyltransferase DNMT3A (DNMT3A1) specifically recognizes nucleosome monoubiquitylated at histone H2A lysine-119 (H2AK119ub1) for establishment of DNA methylation. Mis-regulation of this process may cause aberrant DNA methylation and pathogenesis. However, the molecular basis underlying DNMT3A1-nucleosome interaction remains elusive. Here we report the cryo-EM structure of DNMT3A1s ubiquitin-dependent recruitment (UDR) fragment complexed with H2AK119ub1-modified nucleosome. DNMT3A1 UDR occupies an extensive nucleosome surface, involving the H2A-H2B acidic patch, a surface groove formed by H2A and H3, nucleosomal DNA, and H2AK119ub1. The DNMT3A1 UDRs interaction with H2AK119ub1 affects the functionality of DNMT3A1 in cells in a context-dependent manner. Our structural and biochemical analysis also reveals competition between DNMT3A1 and JARID2, a cofactor of polycomb repression complex 2 (PRC2), for nucleosome binding, suggesting the interplay between different epigenetic pathways. Together, this study reports a molecular basis for H2AK119ub1-dependent DNMT3A1-nucleosome association, with important implications in DNMT3A1-mediated DNA methylation in development.

Spermatogonial stem cells functionality reside in the slow-cycling and heterogeneous undifferentiated spermatogonia cell population. This pool of cells supports lifelong fertility in adult males by balancing self-renewal and differentiation to produce haploid gametes. However, the molecular mechanisms underpinning long-term stemness of undifferentiated spermatogonia during adulthood remain unclear. Here, we discover that an epigenetic regulator, Polycomb repressive complex 1 (PRC1), shields adult undifferentiated spermatogonia from differentiation, maintains slow cycling, and directs commitment to differentiation during steady-state spermatogenesis in adults. We show that PRC2-mediated H3K27me3 is an epigenetic hallmark of adult undifferentiated spermatogonia. Indeed, spermatogonial differentiation is accompanied by a global loss of H3K27me3. Disruption of PRC1 impairs global H3K27me3 deposition, leading to precocious spermatogonial differentiation. Therefore, PRC1 directs PRC2-H3K27me3 deposition to maintain the self-renewing state of undifferentiated spermatogonia. Importantly, in contrast to its role in other tissue stem cells, PRC1 negatively regulates the cell cycle to maintain slow cycling of undifferentiated spermatogonia. Our findings have implications for how epigenetic regulators can be tuned to regulate the stem cell potential, cell cycle and differentiation to ensure lifelong fertility in adult males.

RNA helicase DDX5 is a host restriction factor for hepatitis B virus (HBV) biosynthesis. Mass spectrometry (LC‐MS/MS) identified significant DDX5‐interacting partners, including interferon‐inducible protein 16 (IFI16) and RBBP4/7, an auxiliary subunit of polycomb repressive complex 2 (PRC2). DDX5 co‐eluted with IFI16, RBBP4/7, and core PRC2 subunits in size exclusion chromatography fractions derived from native nuclear extracts. Native gel electrophoresis of DDX5 immunoprecipitants revealed a 750 kDa DDX5/IFI16/PRC2 complex, validated by nanoscale co‐localization via super‐resolution microscopy. Prior studies demonstrated that IFI16 suppresses HBV transcription by binding to the interferon‐sensitive response element of covalently closed circular DNA (cccDNA), reducing H3 acetylation and increasing H3K27me3 levels by an unknown mechanism. Herein, we demonstrate that ectopic expression of IFI16 inhibited HBV transcription from recombinant rcccDNA, correlating with increased IFI16 binding to rcccDNA, reduced H3 acetylation, and elevated H3K27me3, determined by chromatin immunoprecipitation. Importantly, the inhibitory effect of ectopic IFI16 on HBV transcription was reversed by siRNA‐mediated knockdown of DDX5 and EZH2, the methyltransferase subunit of PRC2. This reversal was associated with decreased IFI16 binding to rcccDNA, enhanced H3 acetylation, and reduced H3K27me3. Similarly, endogenous IFI16 induced by interferon‐α inhibited HBV rcccDNA transcription in a DDX5‐ and PRC2‐dependent manner. In HBV‐infected HepG2‐NTCP cells, the antiviral effect of interferon‐α was abrogated upon knockdown of DDX5 and EZH2, underscoring the crucial role of the DDX5 complex in IFI16‐mediated antiviral response. In conclusion, in response to interferon, DDX5 partners with IFI16 to bind cccDNA, directing PRC2 to epigenetically silence cccDNA chromatin, thereby regulating immune signaling and HBV transcription. [ABSTRACT FROM AUTHOR]

Lowered muscle regenerative capacity in the elderly greatly contributes to the development of multiple diseases. The specific roles of long noncoding RNAs (lncRNAs) in muscle regenerative capacity during aging remain unknown. Here, we identify an elevated lncRNA (lncRNA-3), in association with reduced MyoD expression and suppressed muscle regenerative capacity, in the skeletal muscle of aged mice. LncRNA-3 could interact with both the MyoD1 promoter and RbAp46/48, a subunit of Polycomb repressive complex 2 (PRC2). LncRNA-3 could recruit PRC2 to the MyoD1 promoter and enhance the MyoD1 silencing, which, in turn, suppressed the muscle regenerative capacity. Muscle-specific lncRNA-3 knockdown could restore the muscle regenerative capacity in the aged mice. Exogenous RbAp46/48 binding motif (Rb-motif-2) treatment in skeletal muscle could compete for the lncRNA-3 binding, and therefore, enhance the muscle regenerative capacity in the aged mice. Taken together, lncRNA-3 requires PRC2 for MyoD1 silencing to suppress muscle regenerative capacity during aging. These findings provide a novel therapeutic target and a new strategy to elevate the muscle regenerative capacity in the aged population. [ABSTRACT FROM AUTHOR]

Background: SUZ12 is one of the core members of the polycomb repressive complex 2 (PRC2), but its expression and role in lung adenocarcinoma (LUAD) are unclear. We aimed to explore the expression, prognosis, biological functions and roles of SUZ12 in LUAD. Methods: The expression of SUZ12 was detected by immunohistochemical staining, qRT‐PCR, and western blotting in LUAD tissues and cells. The biological functions and molecular mechanisms of SUZ12 were characterized by a range of in vitro and in vivo experiments. Results: SUZ12 was overexpressed in LUAD tissues, and high SUZ12 expression was correlated with worse clinicopathological features and a poorer prognosis. Knockdown of SUZ12 significantly inhibited cell growth, colony formation, invasion, and migration, and induced apoptosis and G1/S phase arrest, while overexpression of SUZ12 had the opposite effects. Knockdown of SUZ12 decreased the tumorigenic capacity of A549 cells in vivo. The expression of key signaling molecules related to the cell cycle, apoptosis, migration, and immunity were altered by the knockdown or overexpression of SUZ12. SUZ12 can directly bind to the Bax promoter region, EZH2 and H3K27me3 levels dependents on SUZ12. The expression levels of SUZ12 and Bax were negatively correlated in LUAD tissues. Conclusions: SUZ12 is a new oncogene related to the poor prognosis of LUAD. SUZ12 regulates LUAD progression by regulating the expression of related signaling molecules, and as a part of the PRC2 complex, it may bind to the Bax promoter to silence Bax expression. [ABSTRACT FROM AUTHOR]

Prostate cancer starts as a treatable hormone-dependent disease, but often ends in a drug-resistant form called castration-resistant prostate cancer (CRPC). Despite the development of the antiandrogens enzalutamide and abiraterone for CRPC, which target the androgen receptor (AR), drug resistance usually develops within 6 months and metastatic CRPC (mCRPC) leads to lethality. EZH2, found with SUZ12, EED, and RbAP48 in Polycomb repressive complex 2 (PRC2), has emerged as an alternative target for the treatment of deadly mCRPC. Unfortunately, drugs targeting EZH2 have shown limited efficacy in mCRPC. To address these failures, we have developed novel, dual-acting peptide inhibitors of PRC2 that uniquely target the SUZ12 protein component, resulting in the inhibition of both PRC2 canonical and noncanonical functions in prostate cancer. These peptides were found to inhibit not only the EZH2 methylation activity, but also block its positive effect on AR gene expression in prostate cancer cells. Since the peptide effect on AR levels is transcriptional, the inhibitory peptides can block the expression of both full-length AR and its splicing variants including AR-V7, which plays a significant role in the development of drug resistance. This dual-mode action provides the peptides with the capability to kill enzalutamide-resistant CRPC cells. These peptides are also more cytotoxic to prostate cancer cells than the combination of enzalutamide and an EZH2 inhibitory drug, which was recently suggested to be an effective treatment of mCRPC disease. Our data show that such a dual-acting therapeutic approach can be more effective than the existing front-line drug therapies for treating deadly mCRPC. [ABSTRACT FROM AUTHOR]

Plants have the fascinating ability to regulate their genetic expression through epigenetic mechanisms. Polycomb group (PcG) proteins in Polycomb repressive complexes (PRC1 and PRC2) especially regulate cellular and developmental processes in eukaryotes through epigenetic mechanisms. Arabidopsis thaliana has a fascinating name, LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), called TERMINAL FLOWER 2 (TFL2). This protein was initially recognized as the plant equivalent of animal HP1 due to the presence of a chromo domain and a chromo shadow domain. It can bind to the trimethylated lysine 27 of histone H3 (H3K27me3) mark spread throughout the genome and regulate gene expression. This is crucial for the plant PcG system, which PRC2 establishes for epigenetic control. Although LHP1 has been found to perform diverse functions, it is still unclear whether these functions are carried out through similar mechanisms and whether it regulates the same target genes. This highlights the need for further research on LHP1 to better understand its mechanisms and functions. The following review provides detailed information about LHP1, which is closely linked to histone marks and the regulation of gene expression and explores how LHP1 influences flower timing and root development to improve crop traits. Recent progress in tomato and soybean production highlights the crucial role of LHP1 in shaping crop characteristics. The review suggests that LHP1 may control H3K27me3 in different plant species by regulating specific genes through epigenetic mechanisms. In summary, it emphasizes the importance of understanding LHP1's role in plant development for breeding purposes. [ABSTRACT FROM AUTHOR]

Gonadal sex determination and differentiation are controlled by somatic support cells of testes (Sertoli cells) and ovaries (granulosa cells). In testes, the epigenetic mechanism that maintains chromatin states responsible for suppressing female sexual differentiation remains unclear. Here, we show that Polycomb repressive complex 1 (PRC1) suppresses a female gene regulatory network in postnatal Sertoli cells. We genetically disrupted PRC1 function in embryonic Sertoli cells after sex determination, and we found that PRC1-depleted postnatal Sertoli cells exhibited defective proliferation and cell death, leading to the degeneration of adult testes. In adult Sertoli cells, PRC1 suppressed specific genes required for granulosa cells, thereby inactivating the female gene regulatory network. Chromatin regions associated with female-specific genes were marked by Polycomb-mediated repressive modifications: PRC1-mediated H2AK119ub and PRC2-mediated H3K27me3. Taken together, this study identifies a critical Polycomb-based mechanism that suppresses ovarian differentiation and maintains Sertoli cell fate in adult testes.

Arabidopsis telomeric repeat binding factors (TRBs) can bind telomeric DNA sequences to protect telomeres from degradation. TRBs can also recruit Polycomb Repressive Complex 2 (PRC2) to deposit tri-methylation of H3 lysine 27 (H3K27me3) over certain target loci. Here, we demonstrate that TRBs also associate and colocalize with JUMONJI14 (JMJ14) and trigger H3K4me3 demethylation at some loci. The trb1/2/3 triple mutant and the jmj14-1 mutant show an increased level of H3K4me3 over TRB and JMJ14 binding sites, resulting in up-regulation of their target genes. Furthermore, tethering TRBs to the promoter region of genes with an artificial zinc finger (TRB-ZF) successfully triggers target gene silencing, as well as H3K27me3 deposition, and H3K4me3 removal. Interestingly, JMJ14 is predominantly recruited to ZF off-target sites with low levels of H3K4me3, which is accompanied with TRB-ZFs triggered H3K4me3 removal at these loci. These results suggest that TRB proteins coordinate PRC2 and JMJ14 activities to repress target genes via H3K27me3 deposition and H3K4me3 removal.

Efficient asexual reproduction techniques are crucial for the expansion of larch; however, the process of adventitious roots (ARs) regeneration has hindered its development. Through comprehensive root development proteomics and transcriptomics analysis, we have identified key epigenetic modifying enzymes involved in the organogenesis of Larix kaempferi. Subsequently, we cloned the enhancer of zeste homolog CURLY LEAF (CLF) from L. kaempferi and performed molecular modeling. The molecular docking results between LkCLF and the histone H3 lysine 27 trimethylation (H3K27me3) inhibitor GSK126 revealed the affinity value is –9 kcal/mol, indicating strong binding interaction between the two. Adding inhibitor GSK126 to the ARs induction medium, morphologically clear primordia appeared between 20 and 25 days after cutting, which was 7–10 d earlier than in the control group, accompanied by an 18.17% increase in rooting rate. Besides, western blot analysis demonstrated the effective inhibition of H3K27me3 levels in stem bases treated with GSK126. Real-time quantitative reverse transcription polymerase chain reaction results showed a significantly elevated expression of BABY BOOM2 compared with 0 μM GSK126 or dimethyl sulfoxide treated groups. Our findings suggest that treating stem bases with 0.01 μM GSK126 during early-stage AR regeneration expedites the developmental process and enhances the rooting rate. This study lays the foundation for a deeper understanding of the roles by H3K27me3 and polycomb repressive complex 2 in the AR regeneration of larch cuttings.Key message: The inhibitor GSK126 effectively reduces H3K27me3 levels and enhances the expression of LkBBM2, thereby expediting the AR regeneration process and improving rooting rate in Larix. kaempferi. [ABSTRACT FROM AUTHOR]

Development of primordial germ cells (PGCs) is required for reproduction. During PGC development in mammals, major epigenetic remodeling occurs, which is hypothesized to establish an epigenetic landscape for sex-specific germ cell differentiation and gametogenesis. In order to address the role of embryonic ectoderm development (EED) and histone 3 lysine 27 trimethylation (H3K27me3) in this process, we created an EED conditional knockout mouse and show that EED is essential for regulating the timing of sex-specific PGC differentiation in both ovaries and testes, as well as X chromosome dosage decompensation in testes. Integrating chromatin and whole genome bisulfite sequencing of epiblast and PGCs, we identified a poised repressive signature of H3K27me3/DNA methylation that we propose is established in the epiblast where EED and DNMT1 interact. Thus, EED joins DNMT1 in regulating the timing of sex-specific PGC differentiation during the critical window when the gonadal niche cells specialize into an ovary or testis.

Polycomb-group proteins play critical roles in gene silencing through the deposition of histone H3 lysine 27 trimethylation (H3K27me3) and chromatin compaction. This process is essential for embryonic stem cell (ESC) pluripotency, differentiation, and development. Polycomb repressive complex 2 (PRC2) can both read and write H3K27me3, enabling progressive spreading of H3K27me3 on the linear genome. Long-range Polycomb-associated DNA contacts have also been described, but their regulation and role in gene silencing remain unclear. Here, we apply H3K27me3 HiChIP, a protein-directed chromosome conformation method, and optical reconstruction of chromatin architecture to profile long-range Polycomb-associated DNA loops that span tens to hundreds of megabases across multiple topological associated domains in mouse ESCs and human induced pluripotent stem cells. We find that H3K27me3 loop anchors are enriched for Polycomb nucleation points and coincide with key developmental genes. Genetic deletion of H3K27me3 loop anchors results in disruption of spatial contact between distant loci and altered H3K27me3 in cis, both locally and megabases away on the same chromosome. In mouse embryos, loop anchor deletion leads to ectopic activation of the partner gene, suggesting that Polycomb-associated loops control gene silencing during development. Further, we find that alterations in PRC2 occupancy resulting from an RNA binding–deficient EZH2 mutant are accompanied by loss of Polycomb-associated DNA looping. Together, these results suggest PRC2 uses RNA binding to enhance long-range chromosome folding and H3K27me3 spreading. Developmental gene loci have unique roles in Polycomb spreading, emerging as important architectural elements of the epigenome.

Two epigenetic pathways of transcriptional repression, DNA methylation and polycomb repressive complex 2 (PRC2), are known to regulate neuronal development and function. However, their respective contributions to brain maturation are unknown. We found that conditional loss of the de novo DNA methyltransferase Dnmt3a in mouse excitatory neurons altered expression of synapse-related genes, stunted synapse maturation, and impaired working memory and social interest. At the genomic level, loss of Dnmt3a abolished postnatal accumulation of CG and non-CG DNA methylation, leaving adult neurons with an unmethylated, fetal-like epigenomic pattern at ~222,000 genomic regions. The PRC2-associated histone modification, H3K27me3, increased at many of these sites. Our data support a dynamic interaction between two fundamental modes of epigenetic repression during postnatal maturation of excitatory neurons, which together confer robustness on neuronal regulation.

Noncoding transcription induces chromatin changes that can mediate environmental responsiveness, but the causes and consequences of these mechanisms are still unclear. Here, we investigate how antisense transcription (termed COOLAIR) interfaces with Polycomb Repressive Complex 2 (PRC2) silencing during winter-induced epigenetic regulation ofArabidopsis FLOWERING LOCUS C (FLC). We use genetic and chromatin analyses on lines ineffective or hyperactive for the antisense pathway in combination with computational modeling to define the mechanisms underlying FLC repression. Our results show that FLC is silenced through pathways that function with different dynamics: a COOLAIR transcription-mediated pathway capable of fast response and in parallel a slow PRC2 switching mechanism that maintains each allele in an epigenetically silenced state. Components of both the COOLAIR and PRC2 pathways are regulated by a common transcriptional regulator (NTL8), which accumulates by reduced dilution due to slow growth at low temperature. The parallel activities of the regulatory steps, and their control by temperature-dependent growth dynamics, create a flexible system for registering widely fluctuating natural temperature conditions that change year on year, and yet ensure robust epigenetic silencing of FLC. [ABSTRACT FROM AUTHOR]

Introduction: Due to its highly aggressiveness and malignancy, glioblastoma (GBM) urgently requires a safe and effective treatment strategy. Zeylenone, a natural polyoxygenated cyclohexenes compound isolated from Uvaria grandiflora, has exhibited potential biological activities in various human diseases, including tumors. Methods: We designed and synthesized a series of (+)-Zeylenone analogues and evaluated their anti-GBM roles through structural-activity analysis. Cell Counting Kit-8, TUNEL, transwell and flow cytometry were employed for investigating the anticancer effects of CA on GBM cells. Western blotting, molecular docking, qRTPCR and ChIP assays were performed to reveal the underlying mechanisms by which CA regulates the GBM cell cycle. The nude mouse xenograft model, HE staining, immunohistochemistry and was used to evaluate the anticancer effect of CA in vivo. Results: We identified CA ((1R, 2R, 3S)-3-p-fluorobenzoyl-zeylenone) as having the lowest IC50 value in GBM cells. CA treatment significantly inhibited the malignant behaviors of GBM cells and induced G0/G1 phase arrest in vitro. Furthermore, we validated the molecular mechanism by which CA interferes with EZH2, attenuating the down-regulation of cyclin-dependent kinase inhibitors p27 and p16 by the PRC2 complex. By establishing orthotopic nude mice models, we further validated the inhibitory role of CA on tumorigenesis of GBM cells in vivo and its potential values to synergistically potentiate the antitumor effects of EZH2 inhibitors. Conclusion: Overall, this paper elucidated the anti-GBM effects and potential mechanisms of CA, and may provide a therapeutic drug candidate for GBM treatment. [ABSTRACT FROM AUTHOR]

Estrogen (E2) is the main contributor to the progression of endometrial cancer (EC). The long noncoding RNA HOX antisense intergenic RNA (HOTAIR) is emerging as a new regulator in several cancer types. This study aimed to investigate the role of HOTAIR in EC development and identify the underlying molecular mechanisms. HOTAIR expression levels in human EC tissues and the corresponding adjacent tissues and human EC Ishikawa cells were determined by quantitative PCR. Ishikawa cells were treated with E2 or estrogen receptor (ER) inhibitor ICI182780, transfected with siHOTAIR oligo, or infected with lentivirus expressing shHOTAIR/shNC, alone or in combinations. The protein expression of polycomb repressive complex 2 (PRC2) was evaluated by western blotting, and cell migration was measured by transwell assays. A xenograft tumorigenic model was established by inoculating control or stable shHOTAIR-infected Ishikawa cells into nude mice and implanting 17β-estradiol release pellets. HOTAIR expression was significantly elevated in human EC tissues. E2 exposure markedly increased HOTAIR levels in Ishikawa cells. Notably, E2 increased the protein expression of PRC2 and promoted EC cell migration, which were dependent on HOTAIR expression, as HOTAIR knockdown abolished these effects of E2. Similarly, E2 promoted the in vivo proliferation of grafted Ishikawa cells via upregulated HOTAIR expression in nude mice. Human EC tissues highly express HOTAIR, and E2-induced EC progression depends on HOTAIR expression. This work suggests that the E2-HOTAIR axis is a potential therapeutic target in EC therapy. [ABSTRACT FROM AUTHOR]

Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) cooperate to determine cell identity by epigenetic gene expression regulation. However, the mechanism of PRC2 recruitment by means of recognition of PRC1-mediated H2AK119ub1 remains poorly understood. Our PRC2 cryo-electron microscopy structure with cofactors JARID2 and AEBP2 bound to a H2AK119ub1-containing nucleosome reveals a bridge helix in EZH2 that connects the SET domain, H3 tail, and nucleosomal DNA. JARID2 and AEBP2 each interact with one ubiquitin and the H2A-H2B surface. JARID2 stimulates PRC2 through interactions with both the polycomb protein EED and the H2AK119-ubiquitin, whereas AEBP2 has an additional scaffolding role. The presence of these cofactors partially overcomes the inhibitory effect that H3K4me3 and H3K36me3 exert on core PRC2 (in the absence of cofactors). Our results support a key role for JARID2 and AEBP2 in the cross-talk between histone modifications and PRC2 activity.

Polycomb Group (PcG) proteins are part of an epigenetic cell memory system that plays essential roles in multicellular development, stem cell biology, X chromosome inactivation, and cancer. In animals, plants, and many fungi, Polycomb Repressive Complex 2 (PRC2) catalyzes trimethylation of histone H3 lysine 27 (H3K27me3) to assemble transcriptionally repressed facultative heterochromatin. PRC2 is structurally and functionally conserved in the model fungus Neurospora crassa, and recent work in this organism has generated insights into PRC2 control and function. To identify components of the facultative heterochromatin pathway, we performed a targeted screen of Neurospora deletion strains lacking individual ATP-dependent chromatin remodeling enzymes. We found the Neurospora homolog of IMITATION SWITCH (ISW) is critical for normal transcriptional repression, nucleosome organization, and establishment of typical histone methylation patterns in facultative heterochromatin domains. We also found that stable interaction between PRC2 and chromatin depends on ISW. A functional ISW ATPase domain is required for gene repression and normal H3K27 methylation. ISW homologs interact with accessory proteins to form multiple complexes with distinct functions. Using proteomics and molecular approaches, we identified three distinct Neurospora ISW-containing complexes. A triple mutant lacking three ISW accessory factors and disrupting multiple ISW complexes led to widespread up-regulation of PRC2 target genes and altered H3K27 methylation patterns, similar to an ISW-deficient strain. Taken together, our data show that ISW is a key component of the facultative heterochromatin pathway in Neurospora, and that distinct ISW complexes perform an apparently overlapping role to regulate chromatin structure and gene repression at PRC2 target domains.

The Polycomb repressive complex 2 (PRC2) is a conserved chromatin-remodelling complex that catalyses the trimethylation of histone H3 lysine 27 (H3K27me3), a mark associated with gene silencing. PRC2 regulates chromatin structure and gene expression during organismal and tissue development and tissue homeostasis in the adult. PRC2 core subunits are associated with various accessory proteins that modulate its function and recruitment to target genes. The multimeric composition of accessory proteins results in two distinct variant complexes of PRC2, PRC2.1 and PRC2.2. Metal response element-binding transcription factor 2 (MTF2) is one of the Polycomb-like proteins (PCLs) that forms the PRC2.1 complex. MTF2 is highly conserved, and as an accessory subunit of PRC2, it has important roles in embryonic stem cell self-renewal and differentiation, development, and cancer progression. Here, we review the impact of MTF2 in PRC2 complex assembly, catalytic activity, and spatiotemporal function. The emerging paradoxical evidence suggesting that MTF2 has divergent roles as either a tumour suppressor or an oncogene in different tissues merits further investigations. Altogether, our review illuminates the context-dependent roles of MTF2 in Polycomb group (PcG) protein-mediated epigenetic regulation. Its impact on disease paves the way for a deeper understanding of epigenetic regulation and novel therapeutic strategies. [ABSTRACT FROM AUTHOR]

Weaver syndrome (WS), an overgrowth/intellectual disability syndrome (OGID), is caused by pathogenic variants in the histone methyltransferase EZH2, which encodes a core component of the Polycomb repressive complex-2 (PRC2). Using genome-wide DNA methylation (DNAm) data for 187 individuals with OGID and 969 control subjects, we show that pathogenic variants in EZH2 generate a highly specific and sensitive DNAm signature reflecting the phenotype of WS. This signature can be used to distinguish loss-of-function from gain-of-function missense variants and to detect somatic mosaicism. We also show that the signature can accurately classify sequence variants in EED and SUZ12, which encode two other core components of PRC2, and predict the presence of pathogenic variants in undiagnosed individuals with OGID. The discovery of a functionally relevant signature with utility for diagnostic classification of sequence variants in EZH2, EED, and SUZ12 supports the emerging paradigm shift for implementation of DNAm signatures into diagnostics and translational research.

In cancer cells, the long non-coding RNA (lncRNA) MALAT1 has arisen as a key partner for the Polycomb Repressive Complex 2 (PRC2), an epigenetic modifier. However, it is unknown whether this partnership occurs genome-wide at the chromatin level, as most of the studies focus on single genes that are usually repressed. Due to the genomic binding properties of both macromolecules, we wondered whether there are binding sites shared by PRC2 and MALAT1. Using public genome-binding datasets for PRC2 and MALAT1 derived from independent ChIP- and CHART-seq experiments performed with the breast cancer cell line MCF7, we searched for regions containing PRC2 and MALAT1 overlapping peaks. Peak calls for each molecule were performed using MACS2 and then overlapping peaks were identified by bedtools intersect. Using this approach, we identified 1293 genomic sites where PRC2 and MALAT1 concur. Interestingly, 54.75% of those sites are within gene promoter regions (

EZH1, a polycomb repressive complex-2 component, is involved in a myriad of cellular processes. EZH1 represses transcription of downstream target genes through histone 3 lysine27 (H3K27) trimethylation (H3K27me3). Genetic variants in histone modifiers have been associated with developmental disorders, while EZH1 has not yet been linked to any human disease. However, the paralog EZH2 is associated with Weaver syndrome. Here we report a previously undiagnosed individual with a novel neurodevelopmental phenotype identified to have a de novo missense variant in EZH1 through exome sequencing. The individual presented in infancy with neurodevelopmental delay and hypotonia and was later noted to have proximal muscle weakness. The variant, p.A678G, is in the SET domain, known for its methyltransferase activity, and an analogous somatic or germline mutation in EZH2 has been reported in patients with B-cell lymphoma or Weaver syndrome, respectively. Human EZH1/2 are homologous to fly Enhancer of zeste (E(z)), an essential gene in Drosophila, and the affected residue (p.A678 in humans, p.A691 in flies) is conserved. To further study this variant, we obtained null alleles and generated transgenic flies expressing wildtype [E(z)WT] and the variant [E(z)A691G]. When expressed ubiquitously the variant rescues null-lethality similar to the wildtype. Overexpression of E(z)WT induces homeotic patterning defects but notably the E(z)A691G variant leads to dramatically stronger morphological phenotypes. We also note a dramatic loss of H3K27me2 and a corresponding increase in H3K27me3 in flies expressing E(z)A691G, suggesting this acts as a gain-of-function allele. In conclusion, here we present a novel EZH1 de novo variant associated with a neurodevelopmental disorder. Furthermore, we found that this variant has a functional impact in Drosophila. [ABSTRACT FROM AUTHOR]

Neurofibromatosis type I (NF1) microdeletion syndrome, accounting for 5–11% of NF1 patients, is caused by the heterozygous deletion of NF1 and a variable number of flanking genes in the 17q11.2 region. This syndrome is characterized by more severe symptoms than those shown by patients with intragenic NF1 mutation and by variable expressivity, which is not fully explained by the haploinsufficiency of the genes included in the deletions. We here reevaluate an 8-year-old NF1 patient, who carries an atypical deletion generating the RNF135-SUZ12 chimeric gene, previously described when he was 3 years old. As the patient has developed multiple cutaneous/subcutaneous neurofibromas over the past 5 years, we hypothesized a role of RNF135-SUZ12 chimeric gene in the onset of the patient's tumor phenotype. Interestingly, SUZ12 is generally lost or disrupted in NF1 microdeletion syndrome and frequently associated to cancer as RNF135. Expression analysis confirmed the presence of the chimeric gene transcript and revealed hypo-expression of five out of the seven analyzed target genes of the polycomb repressive complex 2 (PRC2), to which SUZ12 belongs, in the patient's peripheral blood, indicating a higher transcriptional repression activity mediated by PRC2. Furthermore, decreased expression of tumor suppressor gene TP53, which is targeted by RNF135, was detected. These results suggest that RNF135-SUZ12 chimera may acquire a gain of function, compared with SUZ12 wild type in the PRC2 complex, and a loss of function relative to RNF135 wild type. Both events may have a role in the early onset of the patient's neurofibromas. [ABSTRACT FROM AUTHOR]

Coordinated regulation of gene activity by transcriptional and translational mechanisms poise stem cells for a timely cell-state transition during differentiation. Although important for all stemness-to-differentiation transitions, mechanistic understanding of the fine-tuning of gene transcription is lacking due to the compensatory effect of translational control. We used intermediate neural progenitor (INP) identity commitment to define the mechanisms that fine-tune stemness gene transcription in fly neural stem cells (neuroblasts). We demonstrate that the transcription factor FruitlessC (FruC) binds cis-regulatory elements of most genes uniquely transcribed in neuroblasts. Loss of fruC function alone has no effect on INP commitment but drives INP dedifferentiation when translational control is reduced. FruC negatively regulates gene expression by promoting low-level enrichment of the repressive histone mark H3K27me3 in gene cis-regulatory regions. Identical to fruC loss-of-function, reducing Polycomb Repressive Complex 2 activity increases stemness gene activity. We propose low-level H3K27me3 enrichment fine-tunes gene transcription in stem cells, a mechanism likely conserved from flies to humans.

The SUZ12 gene encodes a subunit of polycomb repressive complex 2 (PRC2) that is essential for development by silencing the expression of multiple genes. Germline heterozygous variants in SUZ12 have been found in Imagawa–Matsumoto syndrome (IMMAS) characterized by overgrowth and multiple dysmorphic features. Similarly, both EZH2 and EED also encode a subunit of PRC2 each and their pathogenic variants cause Weaver syndrome and Cohen–Gibson syndrome, respectively. Clinical manifestations of these syndromes significantly overlap, although their different prevalence rates have recently been noted: generalized overgrowth, intellectual disability, scoliosis, and excessive loose skin appear to be less prevalent in IMMAS than in the other two syndromes. We could not determine any apparent genotype–phenotype correlation in IMMAS. The phenotype of neurofibromatosis type 1 arising from NF1 deletion was also shown to be modified by the deletion of SUZ12, 560 kb away. This review deepens our understanding of the clinical and genetic characteristics of IMMAS together with other overgrowth syndromes related to PRC2. We also report on a novel IMMAS patient carrying a splicing variant (c.1023+1G>C) in SUZ12. This patient had a milder phenotype than other previously reported IMMAS cases, with no macrocephaly or overgrowth phenotypes, highlighting the clinical variation in IMMAS. [ABSTRACT FROM AUTHOR]

Today, human organoids are becoming an integrated part of genomics and epigenomics, as they provide a platform that can be used for the definite study of molecular and cellular mechanisms occurring at different stages of development, particularly organogenesis, within the human body. Airway development is a complex process heavily influenced by epigenetic regulatory mechanisms in response to environmental changes, and as such, human lung organoids are an indispensable asset for further exploration of these mechanisms as a mode of transition from human in vitro to human ex vivo studies. Cultured primarily in compounds mimicking the extracellular matrix, such as Matrigel, these lung organoids have helped us to come to a better understanding of the role of polycomb repressive complex 2 (PRC2) and enhancer of zeste homolog 2 (EZH2) in lung epithelial cell differentiation and airway development, which was first reported in the FASEB journal in 2019. The following is an extended account of how the histone methylation‐regulating PRC2 comes to play in the molding of the human bronchial tree, along with further epigenetic insights based on more recently developed human lung organoids. [ABSTRACT FROM AUTHOR]

Polycomb-like proteins (PCLs) are a crucial group of proteins associated with the Polycomb repressive complex 2 (PRC2) and are responsible for setting up the PRC2.1 subcomplex. In the vertebrate system, three homologous PCLs exist: PHF1 (PCL1), MTF2 (PCL2), and PHF19 (PCL3). Although the PCLs share a similar domain composition, they differ significantly in their primary sequence. PCLs play a critical role in targeting PRC2.1 to its genomic targets and regulating the functionality of PRC2. However, they also have PRC2-independent functions. In addition to their physiological roles, their dysregulation has been associated with various human cancers. In this review, we summarize the current understanding of the molecular mechanisms of the PCLs and how alterations in their functionality contribute to cancer development. We particularly highlight the nonoverlapping and partially opposing roles of the three PCLs in human cancer. Our review provides important insights into the biological significance of the PCLs and their potential as therapeutic targets for cancer treatment. [ABSTRACT FROM AUTHOR]

Despite the development of effective targeted therapies and a significant understanding of carcinogenesis and cancer progression, treatment resistance is a major obstacle in achieving durable long-term control in many types of cancers. Emerging evidence supports that nongenetic mechanisms could play an underappreciated role in therapy resistance. These mechanisms include phenotypic plasticity, which is recognized as a hallmark of cancer and translates to epigenetic and transcriptional control of gene expression. Alterations in the expression and activity of the epigenetic modifier enhancer of zeste homolog 2 (EZH2) support prostate cancer lineage plasticity and progression. EZH2 expression and activity is elevated in castration-resistant prostate cancer treated with androgen receptor pathway inhibitors and in treatment-resistant prostate cancer. Moreover, 17 known residues of EZH2 are phosphorylated on by multiple kinases that modulate its activity, localization, stability, and polycomb repressive complex (PRC2) assembly. In this review, we explore the contribution of EZH2 phosphorylation in regulating canonical PRC2 in a methylation-dependent manner as an epigenetic repressor and in a noncanonical manner independent of PRC2 as a transcription activator. Apart from the contribution of EZH2 phosphorylation at serine 21, threonine 350, and threonine 311 in prostate cancer progression and treatment resistance, we discuss how other EZH2 phosphorylated residues with unknown functions could contribute to prostate cancer based on their upstream regulators and potential therapeutic utility. [ABSTRACT FROM AUTHOR]

Changes in ambient temperature immensely affect developmental programs in many species. Plants adapt to high ambient growth temperature in part by vegetative and reproductive developmental reprogramming, known as thermo-morphogenesis. Thermomorphogenesis is accompanied by massive changes in the transcriptome upon temperature change. Here, we show that transcriptome changes induced by warm ambient temperature require VERNALIZATION INSENSITIVE 3-LIKE 1 (VIL1), a facultative component of the Polycomb repressive complex PRC2, in Arabidopsis. Warm growth temperature elicits genome-wide accumulation of H3K27me3 and VIL1 is necessary for the warm temperature-mediated accumulation of H3K27me3. Consistent with its role as a mediator of thermo-morphogenesis, loss of function of VIL1 results in hypo-responsiveness to warm ambient temperature. Our results show that VIL1 is a major chromatin regulator in responses to high ambient temperature. [ABSTRACT FROM AUTHOR]

Polycomb repressive complex 2 (PRC2) contributes to catalyze the methylation of histone H3 at lysine 27 and plays vital roles in transcriptional silencing and growth development in various organisms. In Magnaporthe oryzae, histone H3K27 is found to associate with altered transcription of in planta induced genes. However, it is still unknown whether and how H3K27me3 modification is involved in pathogenicity to rice and stress response. In this study, we found that core subunits of PRC2, Kmt6-Suz12-Eed, were required for fungal pathogenicity to rice in M. oryzae. Kmt6-Suz12-Eed localized in the nuclei and was necessary for the establishment of H3K27me3 modification. With ChIP-seq analysis, 9.0% of genome regions enriched with H3K27me3 occupancy, which corresponded to 1033 genes in M. oryzae. Furthermore, deletion of Kmt6, Suz12 or Eed altered genome-wide transcriptional expression, while the de-repression genes in the Δkmt6 strain were highly associated with H3K27me3 occupancy. Notably, plenty of genes which encode effectors and secreted enzymes, secondary metabolite synthesis genes, and cell wall stress-responsive genes were directly occupied with H3K27me3 modification and de-repression in the Δkmt6 strain. These results elaborately explained how PRC2 was required for pathogenicity, which is closely related to effector modulated host immunity and host environment adaption.

Polycomb group proteins are transcriptional repressors controlling gene expression patterns and maintaining cell type identity. The chemical modifications of histones and DNA caused by the regulated activity of chromatin-modifying enzymes such as Polycomb help establish and maintain such expression patterns. Polycomb repressive complex 2 (PRC2) is the only known methyltransferase specific for histone H3 lysine 27 (H3K27) and catalyzes its trimethylation leading to the repressive H3K27me3 mark. Structural biology has made important contributions to our understanding of the molecular mechanisms that ensure the spatiotemporal regulation of PRC2 activity and the establishment of inactive chromatin domains marked by H3K27me3. In this review, we discuss the recent structural studies that have advanced our understanding of PRC2 function, in particular the roles of intersubunit interactions in complex assembly and the regulation of methyltransferase activity, as well as the mechanism of local H3K27me3 spreading leading to repressive domains.

BAF complexes are composed of different subunits with varying functional and developmental roles, although many subunits have not been examined in depth. Here we show that the Baf45 subunit Dpf2 maintains pluripotency and ESC differentiation potential. Dpf2 co-occupies enhancers with Oct4, Sox2, p300, and the BAF subunit Brg1, and deleting Dpf2 perturbs ESC self-renewal, induces repression of Tbx3, and impairs mesendodermal differentiation without dramatically altering Brg1 localization. Mesendodermal differentiation can be rescued by restoring Tbx3 expression, whose distal enhancer is positively regulated by Dpf2-dependent H3K27ac maintenance and recruitment of pluripotency TFs and Brg1. In contrast, the PRC2 subunit Eed binds an intragenic Tbx3 enhancer to oppose Dpf2-dependent Tbx3 expression and mesendodermal differentiation. The PRC2 subunit Ezh2 likewise opposes Dpf2-dependent differentiation through a distinct mechanism involving Nanog repression. Together, these findings delineate distinct mechanistic roles for specific BAF and PRC2 subunits during ESC differentiation.

The tendency of mitochondria to undergo or resist BCL2-controlled apoptosis (so-called mitochondrial priming) is a powerful predictor of response to cytotoxic chemotherapy. Fully exploiting this finding will require unraveling the molecular genetics underlying phenotypic variability in mitochondrial priming. Here, we report that mitochondrial apoptosis resistance in T cell acute lymphoblastic leukemia (T-ALL) is mediated by inactivation of polycomb repressive complex 2 (PRC2). In T-ALL clinical specimens, loss-of-function mutations of PRC2 core components (EZH2, EED, or SUZ12) were associated with mitochondrial apoptosis resistance. In T-ALL cells, PRC2 depletion induced resistance to apoptosis induction by multiple chemotherapeutics with distinct mechanisms of action. PRC2 loss induced apoptosis resistance via transcriptional up-regulation of the LIM domain transcription factor CRIP2 and downstream up-regulation of the mitochondrial chaperone TRAP1 These findings demonstrate the importance of mitochondrial apoptotic priming as a prognostic factor in T-ALL and implicate mitochondrial chaperone function as a molecular determinant of chemotherapy response.

Prostate cancer starts as a treatable hormone-dependent disease, but often ends in a drug-resistant form called castration-resistant prostate cancer (CRPC). Despite the development of the antiandrogens enzalutamide and abiraterone for CRPC, which target the androgen receptor (AR), drug resistance usually develops within 6 months and metastatic CRPC (mCRPC) leads to lethality. EZH2, found with SUZ12, EED, and RbAP48 in Polycomb repressive complex 2 (PRC2), has emerged as an alternative target for the treatment of deadly mCRPC. Unfortunately, drugs targeting EZH2 have shown limited efficacy in mCRPC. To address these failures, we have developed novel, dual-acting peptide inhibitors of PRC2 that uniquely target the SUZ12 protein component, resulting in the inhibition of both PRC2 canonical and noncanonical functions in prostate cancer. These peptides were found to inhibit not only the EZH2 methylation activity, but also block its positive effect on AR gene expression in prostate cancer cells. Since the peptide effect on AR levels is transcriptional, the inhibitory peptides can block the expression of both full-length AR and its splicing variants including AR-V7, which plays a significant role in the development of drug resistance. This dual-mode action provides the peptides with the capability to kill enzalutamide-resistant CRPC cells. These peptides are also more cytotoxic to prostate cancer cells than the combination of enzalutamide and an EZH2 inhibitory drug, which was recently suggested to be an effective treatment of mCRPC disease. Our data show that such a dual-acting therapeutic approach can be more effective than the existing front-line drug therapies for treating deadly mCRPC. [ABSTRACT FROM AUTHOR]

Abstract Despite improvements in outcome, 15-25% of newly diagnosed multiple myeloma (MM) patients have treatment resistant high-risk (HR) disease with a poor survival. The lack of a genetic basis for HR has focused attention on the role played by epigenetic changes. Aberrant expression and somatic mutations affecting genes involved in the regulation of tri-methylation of the lysine (K) 27 on histone 3 H3 (H3K27me3) are common in cancer. H3K27me3 is catalyzed by EZH2, the catalytic subunit of the Polycomb Repressive Complex 2 (PRC2). The deregulation of H3K27me3 has been shown to be involved in oncogenic transformation and tumor progression in a variety of hematological malignancies including MM. Recently we have shown that aberrant overexpression of the PRC2 subunit PHD Finger Protein 19 (PHF19) is the most significant overall contributor to HR status further focusing attention on the role played by epigenetic change in MM. By modulating both the PRC2/EZH2 catalytic activity and recruitment, PHF19 regulates the expression of key genes involved in cell growth and differentiation. Here we review the expression, regulation and function of PHF19 both in normal and the pathological contexts of solid cancers and MM. We present evidence that strongly implicates PHF19 in the regulation of genes important in cell cycle and the genetic stability of MM cells making it highly relevant to HR MM behavior. A detailed understanding of the normal and pathological functions of PHF19 will allow us to design therapeutic strategies able to target aggressive subsets of MM.

Transcriptionally repressive histone H3 lysine 27 methylation by Polycomb repressive complex 2 (PRC2) is essential for cellular differentiation and development. Here we report cryo-electron microscopy structures of human PRC2 in a basal state and two distinct active states while in complex with its cofactors JARID2 and AEBP2. Both cofactors mimic the binding of histone H3 tails. JARID2, methylated by PRC2, mimics a methylated H3 tail to stimulate PRC2 activity, whereas AEBP2 interacts with the RBAP48 subunit, mimicking an unmodified H3 tail. SUZ12 interacts with all other subunits within the assembly and thus contributes to the stability of the complex. Our analysis defines the complete architecture of a functionally relevant PRC2 and provides a structural framework to understand its regulation by cofactors, histone tails, and RNA.

Epigenetic regulation is mediated by protein complexes that couple recognition of chromatin marks to activity or recruitment of chromatin-modifying enzymes. Polycomb repressive complex 2 (PRC2), a gene silencer that methylates lysine 27 of histone H3, is stimulated upon recognition of its own catalytic product and has been shown to be more active on dinucleosomes than H3 tails or single nucleosomes. These properties probably facilitate local H3K27me2/3 spreading, causing heterochromatin formation and gene repression. Here, cryo-EM reconstructions of human PRC2 bound to bifunctional dinucleosomes show how a single PRC2, via interactions with nucleosomal DNA, positions the H3 tails of the activating and substrate nucleosome to interact with the EED subunit and the SET domain of EZH2, respectively. We show how the geometry of the PRC2-DNA interactions allows PRC2 to accommodate varying lengths of the linker DNA between nucleosomes. Our structures illustrate how an epigenetic regulator engages with a complex chromatin substrate.

The long noncoding RNAs (lncRNAs), which constitute a large portion of the transcriptome, have gained intense research interest because of their roles in regulating physiological and pathophysiological functions in the cell. We identified from RNA-Seq profiling a set of lncRNAs in cultured human umbilical vein endothelial cells (HUVECs) that are differentially regulated by atheroprotective vs. atheroprone shear flows. Among the comprehensively annotated lncRNAs, including both known and novel transcripts, LINC00341 is one of the most abundant lncRNAs in endothelial cells. Moreover, its expression level is enhanced by atheroprotective pulsatile shear flow and atorvastatin. Overexpression of LINC00341 suppresses the expression of vascular cell adhesion molecule 1 (VCAM1) and the adhesion of monocytes induced by atheroprone flow and tumor necrosis factor-alpha. Underlying this anti-inflammatory role, LINC00341 guides enhancer of zest homolog 2, a core histone methyltransferase of polycomb repressive complex 2, to the promoter region of the VCAM1 gene to suppress VCAM1. Network analysis reveals that the key signaling pathways (e.g., Rho and PI3K/AKT) are co-regulated with LINC00341 in endothelial cells in response to pulsatile shear. Together, these findings suggest that LINC00341, as an example of lncRNAs, plays important roles in modulating endothelial function in health and disease.

Polycomb repressive complex 2 (PRC2) is a multicomponent complex with methyltransferase activity that catalyzes trimethylation of histone H3 at lysine 27 (H3K27me3). Interaction of the epigenetic reader protein EED with EZH2, a catalytic unit of PRC, allosterically stimulates PRC2 activity. In this study, we investigated the role and underlying mechanism of the PRC2 in acute kidney injury (AKI) by using EED226, a highly selective PRC2 inhibitor, to target EED. Administration of EED226 improved renal function, attenuated renal pathological changes, and reduced renal tubular cell apoptosis in a murine model of cisplatin‐induced AKI. In cultured renal epithelial cells, treatment with either EED226 or EED siRNA also ameliorated cisplatin‐induced apoptosis. Mechanistically, EED226 treatment inhibited cisplatin‐induced phosphorylation of p53 and FOXO3a, two transcriptional factors contributing to apoptosis, and preserved expression of Sirtuin 3 and PGC1α, two proteins associated with mitochondrial protection in vivo and in vitro. EED226 was also effective in enhancing renal tubular cell proliferation, suppressing expression of multiple inflammatory cytokines, and reducing infiltration of macrophages to the injured kidney. These data suggest that inhibition of the PRC2 activity by targeting EED can protect against cisplatin‐induced AKI by promoting the survival and proliferation of renal tubular cells and inhibiting inflammatory response. [ABSTRACT FROM AUTHOR]

Polycomb repressive complex 2 (PRC2) contributes to catalyze the methylation of histone H3 at lysine 27 and plays vital roles in transcriptional silencing and growth development in various organisms. In Magnaporthe oryzae , histone H3K27 is found to associate with altered transcription of in planta induced genes. However, it is still unknown whether and how H3K27me3 modification is involved in pathogenicity to rice and stress response. In this study, we found that core subunits of PRC2, Kmt6-Suz12-Eed, were required for fungal pathogenicity to rice in M. oryzae. Kmt6-Suz12-Eed localized in the nuclei and was necessary for the establishment of H3K27me3 modification. With ChIP-seq analysis, 9.0% of genome regions enriched with H3K27me3 occupancy, which corresponded to 1033 genes in M. oryzae. Furthermore, deletion of Kmt6 , Suz12 or Eed altered genome-wide transcriptional expression, while the de-repression genes in the Δ kmt6 strain were highly associated with H3K27me3 occupancy. Notably, plenty of genes which encode effectors and secreted enzymes, secondary metabolite synthesis genes, and cell wall stress-responsive genes were directly occupied with H3K27me3 modification and de-repression in the Δ kmt6 strain. These results elaborately explained how PRC2 was required for pathogenicity, which is closely related to effector modulated host immunity and host environment adaption. [ABSTRACT FROM AUTHOR]

Summary: Transposons significantly contribute to genome fractions in many plants. Although numerous transposon‐related mutations have been identified, the evidence regarding transposon‐derived genes regulating crop yield and other agronomic traits is very limited. In this study, we characterized a rice Harbinger transposon‐derived gene called PANICLE NUMBER AND GRAIN SIZE (PANDA), which epigenetically coordinates panicle number and grain size. Mutation of PANDA caused reduced panicle number but increased grain size in rice, while transgenic plants overexpressing this gene showed the opposite phenotypic change. The PANDA‐encoding protein can bind to the core polycomb repressive complex 2 (PRC2) components OsMSI1 and OsFIE2, and regulates the deposition of H3K27me3 in the target genes, thereby epigenetically repressing their expression. Among the target genes, both OsMADS55 and OsEMF1 were negative regulators of panicle number but positive regulators of grain size, partly explaining the involvement of PANDA in balancing panicle number and grain size. Moreover, moderate overexpression of PANDA driven by its own promoter in the indica rice cultivar can increase grain yield. Thus, our findings present a novel insight into the epigenetic control of rice yield traits by a Harbinger transposon‐derived gene and provide its potential application for rice yield improvement. [ABSTRACT FROM AUTHOR]

BackgroundThe genetic origins of chemotherapy resistance are well established; however, the role of epigenetics in drug resistance is less well understood. To investigate mechanisms of drug resistance, we performed systematic genetic, epigenetic, and transcriptomic analyses of an alkylating agent-sensitive murine lymphoma cell line and a series of resistant lines derived by drug dose escalation.MethodsDose escalation of the alkylating agent mafosfamide was used to create a series of increasingly drug-resistant mouse Burkitt's lymphoma cell lines. Whole genome sequencing, DNA microarrays, reduced representation bisulfite sequencing, and chromatin immunoprecipitation sequencing were used to identify alterations in DNA sequence, mRNA expression, CpG methylation, and H3K27me3 occupancy, respectively, that were associated with increased resistance.ResultsOur data suggest that acquired resistance cannot be explained by genetic alterations. Based on integration of transcriptional profiles with transcription factor binding data, we hypothesize that resistance is driven by epigenetic plasticity. We observed that the resistant cells had H3K27me3 and DNA methylation profiles distinct from those of the parental lines. Moreover, we observed DNA methylation changes in the promoters of genes regulated by E2a and members of the polycomb repressor complex 2 (PRC2) and differentially expressed genes were enriched for targets of E2a. The integrative analysis considering H3K27me3 further supported a role for PRC2 in mediating resistance. By integrating our results with data from the Immunological Genome Project (Immgen.org), we showed that these transcriptional changes track the B-cell maturation axis.ConclusionsOur data suggest a novel mechanism of drug resistance in which E2a and PRC2 drive changes in the B-cell epigenome; these alterations attenuate alkylating agent treatment-induced apoptosis.

Polycomb response elements (PREs) are specific DNA sequences that stably maintain the developmental pattern of gene expression. Drosophila PREs are well characterized, whereas the existence of PREs in mammals remains debated. Accumulating evidence supports a model in which CpG islands recruit Polycomb group (PcG) complexes; however, which subset of CGIs is selected to serve as PREs is unclear. Trithorax (Trx) positively regulates gene expression in Drosophila and co-occupies PREs to antagonize Polycomb-dependent silencing. Here we demonstrate that Trx-dependent H3K4 dimethylation (H3K4me2) marks Drosophila PREs and maintains the developmental expression pattern of nearby genes. Similarly, the mammalian Trx homolog, MLL1, deposits H3K4me2 at CpG-dense regions that could serve as PREs. In the absence of MLL1 and H3K4me2, H3K27me3 levels, a mark of Polycomb repressive complex 2 (PRC2), increase at these loci. By inhibiting PRC2-dependent H3K27me3 in the absence of MLL1, we can rescue expression of these loci, demonstrating a functional balance between MLL1 and PRC2 activities at these sites. Thus, our study provides rules for identifying cell-type-specific functional mammalian PREs within the human genome.

Initially described as a highly specific immunohistochemical marker for carcinomas of mammary origin, trichorhinophalangeal syndrome type 1 (TRPS1) has subsequently been detected in a variety of other non-mammary tumors. In this study, we examined the immunohistochemical expression of TRPS1 in 114 peripheral nerve sheath tumors, including 43 malignant peripheral nerve sheath tumors (MPNSTs), 58 schwannomas, including 9 cellular neurofibromas, and 13 neurofibromas, including 1 atypical neurofibroma. Notably, TRPS1 was expressed in 49% of MPNSTs and was absent in all schwannomas and neurofibromas. All MPNSTs showed TRPS1 labeling in >50% of nuclei, with 95% of cases demonstrating diffuse labeling. Most cases (67%) showed weak TRPS1 immunoreactivity, while a smaller subset showed moderate (24%) or strong (9%) intensity staining. Analysis of publicly available gene expression datasets revealed higher levels of TRPS1 mRNA in MPNSTs with PRC2 inactivation. In keeping with this finding, TRPS1 expression was more commonly observed in MPNSTs with loss of H3K27me3, suggesting a potential relationship between TRPS1 and the PRC2 complex. This study further broadens the spectrum of TRPS1-expressing tumors to include MPNST., Competing Interests: Declaration of competing interest No., (Copyright © 2024 Elsevier Inc. All rights reserved.)