MYPT1/PP1-Mediated EZH2 Dephosphorylation at S21 Promotes Epithelial-Mesenchymal Transition in Fibrosis through Control of Multiple Families of Genes

The methyltransferase EZH2 plays an important role in regulating chromatin conformation and gene transcription. Phosphorylation of EZH2 at S21 by AKT kinase suppresses its function. However, protein phosphatases responsible for the dephosphorylation of EZH2-S21 remain elusive. Here, it is demonstrated that EZH2 is highly expressed in the ocular lens, and AKT-EZH2 axis is important in TGFβ-induced epithelial-mesenchymal transition (EMT). More importantly, it is identified that MYPT1/PP1 dephosphorylates EZH2-S21 and thus modulates its functions. MYPT1 knockout accelerates EMT, but expression of the EZH2-S21A mutant suppresses EMT through control of multiple families of genes. Furthermore, the phosphorylation status and gene expression modulation of EZH2 are implicated in control of anterior subcapsular cataracts (ASC) in human and mouse eyes. Together, the results identify the specific phosphatase for EZH2-S21 and reveal EZH2 dephosphorylation control of several families of genes implicated in lens EMT and ASC pathogenesis. These results provide important novel information in EZH2 function and regulation.

The Haoqin-Huaban formula alleviates UVB-induced skin damage through HOXA11-AS-mediated stabilization of EZH2

Exposure of skin to ultraviolet B (UVB) irradiation induces oxidative damage, immune suppression, inflammation, and skin cancer. Recently, an increase in the use of traditional Chinese medicine decoction with antioxidant properties has emerged as protection for skin tissues against UVB-induced damage. The aim of this study was to investigate mechanisms of the protective effect of the Haoqin-Huaban formula (HQHB) on UVB-induced skin damage. First, cell survival, apoptosis, and oxidative stress were evaluated upon UVB irradiation in the presence of HQHB using HaCaT cells and mice as model systems. Subsequently, bioinformatic analyses, RNA pulldown assays, RNA immunoprecipitation, luciferase reporter assays, and chromatin immunoprecipitation were conducted to verify the regulation among HQHB, hypoxia-inducible factor 1α (HIF-1α), HOXA11-AS and enhancer of zeste homolog 2 (EZH2) in HaCaT cells. In this study, we found that administration of HQHB inhibited, in a dose-dependent manner, UVB-induced skin damage by eliminating oxidative stress. HQHB was found to upregulate HOXA11-AS expression by activating HIF-1α. Furthermore, HOXA11-AS stabilized the EZH2 protein by inhibiting its ubiquitination and proteasomal degradation. Consequently, rescue assays demonstrated that HOXA11-AS promoted proliferation and inhibited apoptosis in HaCaT cells by reducing oxidative stress. Taken together, our results help to elucidate the function and regulatory mechanism of HQHB in reducing UVB-induced skin damage.

Application of enhancer of zeste homolog 2 immunocytochemistry to bile cytology

BACKGROUND

Bile cytology has low diagnostic sensitivity and requires ancillary techniques. This study assessed the utility of enhancer of zeste homolog 2 (EZH2) immunocytochemistry (ICC) in bile cytology.

METHODS

A total of 141 bile cytology specimens from 141 patients were evaluated retrospectively. Papanicolaou-stained slides were immunostained with an antibody to EZH2. After calculation of the EZH2 labeling index (LI), the cutoff value was determined via receiver operating characteristic curve analysis. Cytological performance with and without EZH2 ICC was evaluated with reference to the final diagnosis.

RESULTS

The area under the curve for the EZH2 LI was 0.955, and the cutoff value for identifying benign bile samples versus malignant ones was 24.0%. The sensitivity and specificity values for malignancy were 53.4% and 100% for routine cytology only, 89.0% and 95.7% for EZH2 ICC only, and 89.8% and 95.7% for a combination of routine cytology and EZH2 ICC. The sensitivities of EZH2 ICC only and a combination of routine cytology and EZH2 ICC were significantly improved in comparison with routine cytology only (P < .001). EZH2 ICC alone had a sensitivity of 68.0% and a specificity of 85.7% in bile samples with atypical cytology, a sensitivity of 87.0% in samples that were suspicious for malignancy, and a sensitivity of 85.7% and a specificity of 100% in samples that were negative for malignancy.

CONCLUSIONS

EZH2 ICC improved the diagnostic sensitivity for pancreatobiliary adenocarcinoma in bile cytology. This method is particularly meaningful in samples of indeterminate cytology and may be useful as an initial assessment to ensure that no cancer cells are missed.

Histone Methyltransferase EZH2: A Potential Therapeutic Target for Kidney Diseases

Enhancer of zeste homolog 2 (EZH2) is a histone-lysine N-methyltransferase enzyme that catalyzes the addition of methyl groups to histone H3 at lysine 27, leading to gene silencing. Mutation or over-expression of EZH2 has been linked to many cancers including renal carcinoma. Recent studies have shown that EZH2 expression and activity are also increased in several animal models of kidney injury, such as acute kidney injury (AKI), renal fibrosis, diabetic nephropathy, lupus nephritis (LN), and renal transplantation rejection. The pharmacological and/or genetic inhibition of EZH2 can alleviate AKI, renal fibrosis, and LN, but potentiate podocyte injury in animal models, suggesting that the functional role of EZH2 varies with renal cell type and disease model. In this article, we summarize the role of EZH2 in the pathology of renal injury and relevant mechanisms and highlight EZH2 as a potential therapeutic target for kidney diseases.

LncRNA UCA1 Antagonizes Arsenic-Induced Cell Cycle Arrest through Destabilizing EZH2 and Facilitating NFATc2 Expression

Arsenic (As) is a widespread metalloid contaminant, and its internal exposure is demonstrated to cause serious detrimental health problems. Albeit considerable studies are performed to interrogate the molecular mechanisms responsible for As-induced toxicities, the exact mechanisms are not fully understood yet, especially at the epigenetic regulation level. In the present study, it is identified that long non-coding RNA (lncRNA) urothelial cancer associated 1 (UCA1) alleviates As-induced G2/M phase arrest in human liver cells. Intensive mechanistic investigations illustrate that UCA1 interacts with enhancer of zeste homolog 2 (EZH2) and accelerates the latter's protein turnover rate under normal and As-exposure conditions. The phosphorylation of EZH2 at the Thr-487 site by cyclin dependent kinase 1 (CDK1) is responsible for As-induced EZH2 protein degradation, and UCA1 enhances this process through increasing the interaction between CDK1 and EZH2. As a consequence, the cell cycle regulator nuclear factor of activated T cells 2 (NFATc2), a downstream target of EZH2, is upregulated to resist As-blocked cell cycle progress and cytotoxicity. In conclusion, the findings decipher a novel prosurvival signaling pathway underlying As toxicity from the perspective of epigenetic regulation: UCA1 facilitates the ubiquitination of EZH2 to upregulate NFATc2 and further antagonizes As-induced cell cycle arrest.

Degradation of Polycomb Repressive Complex 2 with an EED-Targeted Bivalent Chemical Degrader

Protein degradation via the use of bivalent chemical degraders provides an alternative strategy to block protein function and assess the biological roles of putative drug targets. This approach capitalizes on the advantages of small-molecule inhibitors while moving beyond the restrictions of traditional pharmacology. Here, we report a chemical degrader (UNC6852) that targets polycomb repressive complex 2 (PRC2). UNC6852 contains an EED226-derived ligand and a ligand for VHL which bind to the WD40 aromatic cage of EED and CRL2^VHL, respectively, to induce proteasomal degradation of PRC2 components, EED, EZH2, and SUZ12. Degradation of PRC2 with UNC6852 blocks the histone methyltransferase activity of EZH2, decreasing H3K27me3 levels in HeLa cells and diffuse large B cell lymphoma (DLBCL) cells containing EZH2 gain-of-function mutations. UNC6852 degrades both wild-type and mutant EZH2, and additionally displays anti-proliferative effects in this cancer model system.

LncRNA SNHG6 promotes the migration, invasion, and epithelial-mesenchymal transition of colorectal cancer cells by miR-26a/EZH2 axis

Objective: Colorectal cancer (CRC) is a leading cause of cancer-related deaths worldwide. Small nucleolar RNA host gene 6 (SNHG6) was reported to function as an oncogene in a number of cancers. Here, we aimed to further explore the roles and molecular mechanism of SNHG6 in CRC metastasis.

Methods: The expression levels of SNHG6, miR-26a, and enhancer of zeste homolog 2 (EZH2) mRNA were assessed by quantification real-time PCR in CRC tissues and cell lines. Western blot analysis was performed to determine the levels of E-cadherin, Snail, Vimentin, N-cadherin, and EZH2. Cell migration and invasion capacities were detected by transwell assay. Dual-luciferase reporter assay or RNA Immunoprecipitation assay was employed to verify the interaction between SNHG6 and miR-26a, or EZH2 and miR-26a.

Results: Our data indicated that SNHG6 and EZH2 mRNA were upregulated, and miR-26a was downregulated in CRC tissues and cell lines. SNHG6 knockdown suppressed the migration, invasion, and epithelial-mesenchymal transition (EMT) of CRC cells. Moreover, SNHG6 binded to miR-26a and repressed miR-26a expression. EZH2 was a direct target of miR-26a, and it was regulated by SNHG6/miR-26a. MiR-26a inhibitor undermined the effect of SNHG6 knockdown on cell migration, invasion, and EMT. Additionally, EZH2 antagonized the effect of miR-26a on cell migration, invasion, and EMT in CRC cells.

Conclusion: SNHG6 knockdown suppressed cell migration, invasion, and EMT at least partly by sponging miR-26a and regulating EZH2 expression in CRC cells, providing a strategy for blocking CRC metastasis.

LncRNA SNHG17 promotes gastric cancer progression by epigenetically silencing of p15 and p57

Long noncoding RNAs (lncRNA) are attractive biomarkers and therapeutic targets because of their disease- and stage-restricted expression. Small nucleolar RNA host gene 17 (SNHG17) belongs to a large family of noncoding genes hosting small RNAs, with its expression pattern and biological function not clarified in gastric cancer (GC). Thus, we conducted this study to investigate the functional significance and the underlying mechanisms of SNHG17 in GC progression. Our results showed that SNHG17 expression was upregulated in GC tissues and cells, and its high expression was significantly correlated with increased invasion depth, lymphatic metastasis, and advanced TNM stage. The expression of plasma SNHG17 was also found upregulated in patients with GC compared with healthy controls, with a moderate accuracy for diagnosis of GC (area under the receiver operating characteristic curve = 0.748; 95% CI, 0.666-0.830). Gain- and loss-of-function of SNHG17 revealed that SNHG17 promoted GC cell proliferation, cell cycle progression, invasion, and migration and inhibited apoptosis. Mechanistic investigations showed that SNHG17 was associated with polycomb repressive complex 2 and that this association was required for epigenetic repression of cyclin-dependent protein kinase inhibitors, including p15 and p57, thus contributing to the regulation of GC cell cycle and proliferation. Furthermore, rescue experiments indicated that SNHG17 functioned as an oncogene via activating enhancer of zeste homolog 2 in GC cells. Our study provides a new perspective for SNHG17 acting as a noncoding oncogene in GC tumorigenesis, and it may serve as a novel early diagnostic marker and potential target for the treatment of GC.

Region specific knock-out reveals distinct roles of chromatin modifiers in adult neurogenic niches

Histone methyltransferases (HMTs) are present in heterogeneous cell populations within the adult brain including neurogenic niches. Yet the question remains whether loss of HMTs and the resulting changes in histone methylation alter cell fate in a region-specific manner. We utilized stereotaxic injection of Cre recombinant protein into the adult neurogenic niches, the subventricular zone (SVZ) adjacent to the lateral ventricle and the subgranular zone (SGZ) of the dentate gyrus. We confirmed that Cre protein was enzymatically active in vivo and recombination events were restricted to the vicinity of injection areas. In this study, we focus on using Cre mediated recombination in mice harboring floxed HMT: enhancer of zeste homolog 2 (EZH2) or suppressor of variegation homolog (Suv4-20h). Injectable Cre protein successfully knocked out either EZH2 or Suv4-20h, allowing assessment of long-term effects in a region-specific fashion. We performed meso-scale imaging and flow cytometry for phenotype analysis and unbiased quantification. We demonstrated that regional loss of EZH2 affects the differentiation paradigm of neural stem progenitor cells as well as the maintenance of stem cell population. We further demonstrated that regional loss of Suv4-20h influences the cell cycle but does not affect stem cell differentiation patterns. Therefore, Cre protein mediated knock-out a given HMT unravel their distinguishable and important roles in adult neurogenic niches. This Cre protein-based approach offers tightly-controlled knockouts in multiple cell types simultaneously for studying diverse regulatory mechanisms and is optimal for region-specific manipulation within complex, heterogeneous brain architectures.

Regulation and role of post-translational modifications of enhancer of zeste homologue 2 in cancer development

Post-translational modifications (PTMs) are critical molecular events which alter protein conformation after their synthesis and diversity protein properties by modulating their stability, localization, interacting partners or the activity of their substrates, consequently exerting pivotal roles in regulating the functions of many important eukaryotic proteins. It has been well acknowledged that PTMs are of great importance in a broad range of biological processes such as gene regulation, cell proliferation, differentiation and apoptosis, tissue development, diseases, tumor progression and drug resistance. As the core and contributing catalytic subunit of Polycomb repressive complex 2(PRC2), Enhancer of zeste homolog 2 (EZH2) is a master epigenetic regulator, often serving as a highly conserved histone methyltransferase (HMTase) to induce histone H3 lysine 27 trimethylation (H3K27me3) and repress gene transcription and expression. Dysregulated EZH2 expression is frequently associated with cancer development and poor prognosis in a wide variety of cancers. Considered its essential role in carcinogenesis, EZH2 is a potential candidate for cancer targeted therapy. Remarkably, mounting evidence highlights that EZH2 expression, activity and stability can be regulated by PTMs including phosphorylation, acetylation, ubiquitination, sumoylation and GlcNAcylation aside from its well-validated modifications in transcriptional and post-transcriptional levels. However, the precise regulatory mechanisms underlying EZH2 PTMs and whether other types of PTMs orchestrate in EZH2 remain largely unclear. In this review, we summarize current advances in the understanding of EZH2 regulation by PTMs and their associated biological functions during tumorigenesis.