scholarly journals CSIG-27. PRC2-INDEPENDENT FUNCTION OF EZH2/HP1BP3 COMPLEX IN GLIOMA STEM CELLS

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi49-vi50
Author(s):  
Junxia Zhang ◽  
Tianfu Yu ◽  
Ning Liu
Keyword(s):  
Stem Cells ◽  
Transcriptional Repression ◽  
Glioma Stem Cells ◽  
Independent Function ◽  
Set Domain ◽  
Heterochromatin Protein 1 ◽  
Heterochromatin Protein ◽  
Histone Lysine Methyltransferase ◽  
Lysine Methyltransferase

Abstract Glioblastoma (GBM) displays cellular and genetical heterogeneity harboring a subpopulation of glioma stem cells (GSCs). Enhancer of zeste homolog 2 (EZH2), a histone lysine methyltransferase, is the core subunit of the polycomb repressor 2 (PRC2) complex, mediates gene transcriptional repression in both normal and tumor stem cells. An oncogenic role of EZH2 as a PRC2-dependent transcriptional silencer is well established; however, non-canonical functions of EZH2 are incompletely understood. Here we found a novel oncogenic mechanism for EZH2 in a PRC2-indenpend way in GSCs. Using HPLC-MS/MS and IP assay, EZH2 bound to HP1BP3 (heterochromatin protein 1 binding protein 3), a heterochromatin-related protein, with its pre-SET domain. Overexpression of H1P3B3 enhanced the proliferation, self-renewal and temozolomide (TMZ) resistance of GBM cells. Intriguingly, H1PBP3 was up-regulated in high grade gliomas with proneural (PN) subtypes and had a high predictive value on prognosis in patients with PN gliomas. Furthermore, EZH2 and HP1BP3 co-activated the expression of WNT7B by blocking the methylation of H3K9, thereby increasing TMZ resistance and tumorigenicity of glioblastoma cells. Interestingly, inhibition of WNT7B autocrine via LGK974, a specific porcupine inhibitor, effectively reversed the TMZ resistance of both GSCs and GBM glioma cells expressing HP1BP3. Hence, targeting the PRC2-independent function of EZH2 is an effective approach to enhance the efficacy of treating GBM.

scholarly journals The H3K9 Methylation Writer SETDB1 and its Reader MPP8 Cooperate to Silence Satellite DNA Repeats in Mouse Embryonic Stem Cells

Genes ◽  
2019 ◽  
Vol 10 (10) ◽  
pp. 750 ◽  
Author(s):  
Cruz-Tapias ◽  
Robin ◽  
Pontis ◽  
Maestro ◽  
Ait-Si-Ali
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Embryonic Stem ◽  
Dna Repeats ◽  
H3k9 Methylation ◽  
Set Domain ◽  
Histone Lysine Methyltransferase ◽  
Satellite Repeats ◽  
M Phase ◽  
Lysine Methyltransferase

SETDB1 (SET Domain Bifurcated histone lysine methyltransferase 1) is a key lysine methyltransferase (KMT) required in embryonic stem cells (ESCs), where it silences transposable elements and DNA repeats via histone H3 lysine 9 tri-methylation (H3K9me3), independently of DNA methylation. The H3K9 methylation reader M-Phase Phosphoprotein 8 (MPP8) is highly expressed in ESCs and germline cells. Although evidence of a cooperation between H3K9 KMTs and MPP8 in committed cells has emerged, the interplay between H3K9 methylation writers and MPP8 in ESCs remains elusive. Here, we show that MPP8 interacts physically and functionally with SETDB1 in ESCs. Indeed, combining biochemical, transcriptomic and genomic analyses, we found that MPP8 and SETDB1 co-regulate a significant number of common genomic targets, especially the DNA satellite repeats. Together, our data point to a model in which the silencing of a class of repeated sequences in ESCs involves the cooperation between the H3K9 methylation writer SETDB1 and its reader MPP8.

scholarly journals HAUSP Stabilizes SOX2 through Deubiquitination to Maintain Self-renewal and Tumorigenic Potential of Glioma Stem Cells

2021 ◽  
Author(s):  
Zhi Huang ◽  
Kui Zhai ◽  
Qiulian Wu ◽  
Xiaoguang Fang ◽  
Qian Huang ◽  
...  
Keyword(s):  
Stem Cells ◽  
Glioma Stem Cells ◽  
Posttranslational Regulation ◽  
Malignant Growth ◽  
Self Renewal ◽  
Animal Survival ◽  
Promising Target ◽  
Tumorigenic Potential ◽  
Therapeutic Opportunity

Glioblastoma (GBM) is the most lethal brain tumor containing glioma stem cells (GSCs) that promote malignant growth and therapeutic resistance. The self-renewal and tumorigenic potential of GSCs are maintained by core stem cell transcription factors including SOX2. Defining the posttranslational regulation of SOX2 may offer new insights into GSC biology and potential therapeutic opportunity. Here, we discover that HAUSP stabilizes SOX2 through deubiquitination to maintain GSC self-renewal and tumorigenic potential. HAUSP is preferentially expressed in GSCs in perivascular niches in GBMs. Disrupting HAUSP by shRNA or its inhibitor P22077 promoted SOX2 degradation, induced GSC differentiation, impaired GSC tumorigenic potential, and suppressed GBM tumor growth. Importantly, pharmacological inhibition of HAUSP synergized with radiation to inhibit GBM growth and extended animal survival, indicating that targeting HAUSP may overcome GSC-mediated radioresistance. Our findings reveal an unappreciated crucial role of HAUSP in the GSC maintenance and provide a promising target for developing effective anti-GSC therapeutics to improve GBM treatment.

scholarly journals SET‐domain bacterial effectors target heterochromatin protein 1 to activate host rDNA transcription

EMBO Reports ◽  
2013 ◽  
Vol 14 (8) ◽  
pp. 733-740 ◽  
Author(s):  
Ting Li ◽  
Qiuhe Lu ◽  
Guolun Wang ◽  
Hao Xu ◽  
Huanwei Huang ◽  
...  
Keyword(s):  
Set Domain ◽  
Rdna Transcription ◽  
Heterochromatin Protein 1 ◽  
Heterochromatin Protein ◽  
Bacterial Effectors

scholarly journals Protein lysine 43 methylation by EZH1 promotes AML1-ETO transcriptional repression in leukemia

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Liping Dou ◽  
Fei Yan ◽  
Jiuxia Pang ◽  
Dehua Zheng ◽  
Dandan Li ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Transcriptional Repression ◽  
Lysine Methylation ◽  
Post Translational Modification ◽  
Histone Lysine Methylation ◽  
Histone Lysine ◽  
Histone Lysine Methyltransferase ◽  
Lysine Methyltransferase

Abstract The oncogenic fusion protein AML1-ETO retains the ability of AML1 to interact with the enhancer core DNA sequences, but blocks AML1-dependent transcription. Previous studies have shown that post-translational modification of AML1-ETO may play a role in its regulation. Here we report that AML1-ETO-positive patients, with high histone lysine methyltransferase Enhancer of zeste homolog 1 (EZH1) expression, show a worse overall survival than those with lower EZH1 expression. EZH1 knockdown impairs survival and proliferation of AML1-ETO-expressing cells in vitro and in vivo. We find that EZH1 WD domain binds to the AML1-ETO NHR1 domain and methylates AML1-ETO at lysine 43 (Lys43). This requires the EZH1 SET domain, which augments AML1-ETO-dependent repression of tumor suppressor genes. Loss of Lys43 methylation by point mutation or domain deletion impairs AML1-ETO-repressive activity. These findings highlight the role of EZH1 in non-histone lysine methylation, indicating that cooperation between AML1-ETO and EZH1 and AML1-ETO site-specific lysine methylation promote AML1-ETO transcriptional repression in leukemia.

scholarly journals Identification of heterochromatin protein 1 (HP1) as a phosphorylation target by Pim-1 kinase and the effect of phosphorylation on the transcriptional repression function of HP11

FEBS Letters ◽  
2000 ◽  
Vol 467 (1) ◽  
pp. 17-21 ◽  
Author(s):  
Naoyuki Koike ◽  
Hiroshi Maita ◽  
Takahiro Taira ◽  
Hiroyoshi Ariga ◽  
Sanae M.M. Iguchi-Ariga
Keyword(s):  
Transcriptional Repression ◽  
Heterochromatin Protein 1 ◽  
Heterochromatin Protein

scholarly journals TMIC-01. THE DYSTROGLYCAN RECEPTOR MAINTAINS GLIOMA STEM CELLS IN THE VASCULAR NICHE

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi247-vi247
Author(s):  
Bryan Day ◽  
Justin Lathia ◽  
Zara Bruce ◽  
Kathleen Ensbey ◽  
Yi Chieh Lim ◽  
...  
Keyword(s):  
Stem Cells ◽  
Critical Factor ◽  
Glioma Stem Cells ◽  
Structural Element ◽  
Α Subunit ◽  
Vascular Niche ◽  
Cns Neoplasms ◽  
Tumour Initiation

Abstract Glioblastomas (GBMs) are malignant central nervous system (CNS) neoplasms with a very poor prognosis. They display cellular hierarchies containing self-renewing tumourigenic glioma stem cells (GSCs) in a complex heterogeneous microenvironment. One proposed GSC niche is the extracellular matrix (ECM)-rich perivascular bed of the tumour. Here, we report that the ECM binding alpha (α) subunit of the dystroglycan (DG) receptor is expressed and functionally glycosylated on GSCs residing in the vascular niche. Glycosylated αDG is also expressed highly on the most aggressive mesenchymal-like GBM tumour tissue. Furthermore, we found that DG acts to maintain a de-differentiated stem cell-like phenotype via tight control of MAPK activation. Antibody-based blockade of αDG induces robust ERK-mediated differentiation leading to reduced GSC potential. DG was shown to be required for tumour initiation, with constitutive loss significantly delaying or preventing tumourigenic potential in-vivo. These findings reveal a central role of the DG receptor not only as a structural element but also as a critical factor in the maintenance of GSCs in the GBM vascular niche.

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