Gene Summary

Gene:SUZ12; SUZ12 polycomb repressive complex 2 subunit
Aliases: CHET9, JJAZ1
Summary:This zinc finger gene has been identified at the breakpoints of a recurrent chromosomal translocation reported in endometrial stromal sarcoma. Recombination of these breakpoints results in the fusion of this gene and JAZF1. The protein encoded by this gene contains a zinc finger domain in the C terminus of the coding region. [provided by RefSeq, Jul 2009]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:polycomb protein SUZ12
Source:NCBIAccessed: 11 March, 2017


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Breast Cancer
  • Tumor Suppressor Proteins
  • Polycomb-Group Proteins
  • Chromosome 17
  • Histones
  • Transcriptome
  • Precursor T-Cell Lymphoblastic Leukemia-Lymphoma
  • SUZ12
  • MicroRNAs
  • DNA Sequence Analysis
  • Carrier Proteins
  • Promoter Regions
  • Cell Proliferation
  • Cancer Stem Cells
  • Sequence Homology, Nucleic Acid
  • Transfection
  • Prostate Cancer
  • Up-Regulation
  • Polycomb Repressive Complex 2
  • Transcription Factor RelA
  • Gene Expression Profiling
  • Apoptosis
  • Sequence Homology
  • Translocation
  • rho-Associated Kinases
  • Stomach Cancer
  • S-Adenosylmethionine
  • Epigenetics
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Enhancer of Zeste Homolog 2 Protein
  • DNA Methylation
  • Neoplasm Proteins
  • Reproducibility of Results
  • DNA-Binding Proteins
  • Ubiquitin-Protein Ligases
  • Cancer Gene Expression Regulation
  • Telomere
  • Endometrial Cancer
  • Sex Characteristics
  • Nuclear Proteins
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: SUZ12 (cancer-related)

Schäfer V, Ernst J, Rinke J, et al.
EZH2 mutations and promoter hypermethylation in childhood acute lymphoblastic leukemia.
J Cancer Res Clin Oncol. 2016; 142(7):1641-50 [PubMed] Related Publications
PURPOSE: Acute lymphoblastic leukemia (ALL) is the most common malignancy in children and young adults. The polycomb repressive complex 2 (PRC2) has been identified as one of the most frequently mutated epigenetic protein complexes in hematologic cancers. PRC2 acts as an epigenetic repressor through histone H3 lysine 27 trimethylation (H3K27me3), catalyzed by the histone methyltransferase enhancer of zeste homolog 2 protein (EZH2).
METHODS: To study the prevalence and clinical impact of PRC2 aberrations in an unselected childhood ALL cohort (n = 152), we performed PRC2 mutational screenings by Sanger sequencing and promoter methylation analyses by quantitative pyrosequencing for the three PRC2 core component genes EZH2, suppressor of zeste 12 (SUZ12), and embryonic ectoderm development (EED). Targeted deep next-generation sequencing of 30 frequently mutated genes in leukemia was performed to search for cooperating mutations in patients harboring PRC2 aberrations. Finally, the functional consequence of EZH2 promoter hypermethylation on H3K27me3 was studied by Western blot analyses of primary cells.
RESULTS: Loss-of-function EZH2 mutations were detected in 2/152 (1.3 %) patients with common-ALL and early T-cell precursor (ETP)-ALL, respectively. In one patient, targeted deep sequencing identified cooperating mutations in ASXL1 and TET2. EZH2 promoter hypermethylation was found in one patient with ETP-ALL which led to reduced H3K27me3. In comparison with healthy children, the EZH2 promoter was significantly higher methylated in T-ALL patients. No mutations or promoter methylation changes were identified for SUZ12 or EED genes, respectively.
CONCLUSIONS: Although PRC2 aberrations seem to be rare in childhood ALL, our findings indicate that EZH2 aberrations might contribute to the disease in specific cases. Hereby, EZH2 promoter hypermethylation might have functionally similar consequences as loss-of-function mutations.

Lv J, Qiu M, Xia W, et al.
High expression of long non-coding RNA SBF2-AS1 promotes proliferation in non-small cell lung cancer.
J Exp Clin Cancer Res. 2016; 35:75 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Recent evidence has proven that long noncoding RNAs (lncRNAs) play important roles in cancer biology, while few lncRNAs have been characterized in NSCLC. Here, we characterized a novel lncRNA, SBF2 antisense RNA 1 (SBF2-AS1), in non-small cell lung cancer (NSCLC).
METHODS: Quantitative real-time PCR was used to quantify SBF2-AS1 expression in NSCLC tissues and cell lines. The correlation of SBF2-AS1 expression with clinicopathologic features was analyzed in a cohort NSCLC patient. Loss of function and gain of function studies were performed to determine the effects of SBF2-AS1 on proliferation and metastasis of NSCLC cells. RNA immunoprecipitation and chromosome immunoprecipitation assay was performed to confirm the interaction between SBF2-AS1 with protein and chromosome.
RESULTS: We confirmed that SBF2-AS1 was significantly upregulated in NSCLC compared with corresponding non-tumor tissues, and a high expression level of SBF2-AS1 was correlated with lymph node metastasis and advanced TNM stage. Using siRNAs specifically targeting SBF2-AS1 and plasmid vector, we successfully silenced and overexpressed SBF2-AS1 in NSCCLC cell lines and investigated its biological function both in vitro and in vivo. After the silencing of SBF2-AS1, the metastasis of NSCLC cells was significantly inhibited, the silencing of SBF2-AS1 decreased the proliferation of NSCLC cells, and the cell cycle was arrested at the G1 phase; while overexpression promoted proliferation ability. Xenograft tumor models revealed that the silencing of SBF2-AS1 inhibited tumor growth in vivo. We speculated that SBF2-AS1 might negatively regulate P21. RNA immunoprecipitation discovered that SBF2-AS2 could bind with a core component of polycomb repressive complex2, SUZ12. Additionally chromatin immunoprecipitation assay demonstrated that, after silencing SBF2-AS1, the enrichment of SUZ12 and trimethylation of histone 3 lysine 27 decreased at the promoter region of P21.
CONCLUSIONS: We demonstrated that SBF2-AS1 is upregulated in NSCLC and promotes proliferation of NSCLC tumor cells. SBF2-AS1 may serve as a novel biomarker and potential therapeutic target for NSCLC patients.

Jain P, Di Croce L
Mutations and deletions of PRC2 in prostate cancer.
Bioessays. 2016; 38(5):446-54 [PubMed] Related Publications
The Polycomb group of proteins (PcGs) are transcriptional repressor complexes that regulate important biological processes and play critical roles in cancer. Mutating or deleting EZH2 can have both oncogenic and tumor suppressive functions by increasing or decreasing H3K27me3. In contrast, mutations of SUZ12 and EED are reported to have tumor suppressive functions. EZH2 is overexpressed in many cancers, including prostate cancer, which can lead to silencing of tumor suppressors, genes regulating epithelial to mesenchymal transition (EMT), and interferon signaling. In some cases, EZH2 overexpression also leads to its use of non-histone substrates. Lastly, PRC2 associated factors can influence the progression of cancer through progressive mutations or by specific binding to certain target genes. Here, we discuss which mutations and deletions of the PRC2 complex have been detected in different cancers, with a specific focus on the overexpression of EZH2 in prostate cancer.

Danis E, Yamauchi T, Echanique K, et al.
Ezh2 Controls an Early Hematopoietic Program and Growth and Survival Signaling in Early T Cell Precursor Acute Lymphoblastic Leukemia.
Cell Rep. 2016; 14(8):1953-65 [PubMed] Free Access to Full Article Related Publications
Early T cell precursor acute lymphoblastic leukemia (ETP-ALL) is an aggressive subtype of ALL distinguished by stem-cell-associated and myeloid transcriptional programs. Inactivating alterations of Polycomb repressive complex 2 components are frequent in human ETP-ALL, but their functional role is largely undefined. We have studied the involvement of Ezh2 in a murine model of NRASQ61K-driven leukemia that recapitulates phenotypic and transcriptional features of ETP-ALL. Homozygous inactivation of Ezh2 cooperated with oncogenic NRASQ61K to accelerate leukemia onset. Inactivation of Ezh2 accentuated expression of genes highly expressed in human ETP-ALL and in normal murine early thymic progenitors. Moreover, we found that Ezh2 contributes to the silencing of stem-cell- and early-progenitor-cell-associated genes. Loss of Ezh2 also resulted in increased activation of STAT3 by tyrosine 705 phosphorylation. Our data mechanistically link Ezh2 inactivation to stem-cell-associated transcriptional programs and increased growth/survival signaling, features that convey an adverse prognosis in patients.

Yeh CH, Bai XT, Moles R, et al.
Mutation of epigenetic regulators TET2 and MLL3 in patients with HTLV-I-induced acute adult T-cell leukemia.
Mol Cancer. 2016; 15:15 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Epigenetic regulators play a critical role in the maintenance of specific chromatin domains in an active or repressed state. Disruption of epigenetic regulatory mechanisms is widespread in cancer cells and largely contributes to the transformation process through active repression of tumor suppressor genes. While mutations of epigenetic regulators have been reported in various lymphoid malignancies and solid cancers, mutation of these genes in HTLV-I-associated T-cell leukemia has not been investigated.
METHOD: Here we used whole genome next generation sequencing (NGS) of uncultured freshly isolated ATL samples and identified the presence of mutations in SUZ12, DNMT1, DNMT3A, DNMT3B, TET1, TET2, IDH1, IDH2, MLL, MLL2, MLL3 and MLL4.
RESULTS: TET2 was the most frequently mutated gene, occurring in 32 % (10/31) of ATL samples analyzed. Interestingly, NGS revealed nonsense mutations accompanied by loss of heterozygosity (LOH) in TET2 and MLL3, which was further confirmed by cloning and direct sequencing of DNA from uncultured cells. Finally, direct sequencing of matched control and tumor samples revealed that TET2 mutation was present only in ATL tumor cells.
CONCLUSIONS: Our results suggest that inactivation of MLL3 and TET2 may play an important role in the tumorigenesis process of HTLV-I-induced ATL.

Hrzenjak A
JAZF1/SUZ12 gene fusion in endometrial stromal sarcomas.
Orphanet J Rare Dis. 2016; 11:15 [PubMed] Free Access to Full Article Related Publications
Endometrial stromal sarcomas (ESSs) belong to the rarest uterine malignancies (prevalence category <1-9/1,000,000). According to the new 2014 World Health Organisation (WHO) classification, they are separated into four categories; benign endometrial stromal nodules (ESNs), low grade endometrial stromal sarcomas (LG-ESSs), high-grade endometrial stromal sarcomas (HG-ESSs) and undifferentiated uterine sarcomas (UUSs). Due to heterogeneous histopathologic appearance these tumors still represent diagnostic challenge, even for experienced pathologists. ESSs are genetically very heterogeneous and several chromosomal translocations and gene fusions have so far been identified in these malignancies. To date the JAZF1/SUZ12 gene fusion is by far the most frequent and seems to be the cytogenetic hallmark of ESN and LG-ESS. Based on present literature data this gene fusion is present in approximately 75% of ESN, 50% of LG-ESS and 15% of HG-ESS cases. The frequency of JAZF1/SUZ12 appearance varies between classic ESS and different morphologic variants. This gene fusion is suggested to become a specific diagnostic tool, especially in difficult borderline cases. In combination with the recently described YWHAE/FAM22 gene fusion the JAZF1/SUZ12 fusion could be used to differentiate between LG-ESS and HG-ESS. The purpose of this review is to summarize literature data published in last two and a half decades about this gene fusion, as a contribution to our understanding of ESS genetics and pathogenesis.

Ghalandary M, Behmanesh M, Sadeghizadeh M
Evaluating of suppressor of zeste 12 and chromobox homolog 8 genes expression showed two possible origins for gastric cancer development.
Indian J Cancer. 2015 Jan-Mar; 52(1):27-31 [PubMed] Related Publications
CONTEXT: Changes in genome, made by multiple genetic and epigenetic alterations result to the cancer initiation and progression. Suppressor of zeste 12 (SUZ12) and chromobox homolog 8 (CBX8) proteins are two components of epigenetic regulators that their function in the initiation and progression of cancers are not well-understood.
AIMS: The role of SUZ12 and its target CBX8 is examined.
SETTINGS AND DESIGN: Comparing the expression levels of SUZ12 and CBX8 between 30 gastric tumor and their marginal tissues.
MATERIALS AND METHODS: Quantitative reverse transcription polymerase chain reaction technique was performed.
STATISTICAL ANALYSIS: Statistical comparison was carried out using Statistical Program for Social Sciences software 16.0 (Released 2007, SPSS for Windows. SPSS Inc., Chicago, IL, USA) and (GraphPad Prism version 5 for Windows, GraphPad Software, La Jolla, California USA,
RESULTS: Despite the obvious differences in the expression of these genes in each sample for tumor and its marginal tissue, statistical analysis did not show significant differences in the mean of expression for SUZ12 and CBX8 genes in total. Due to the variation in expression levels, the samples could be divided into two groups for each gene; group 1, in which the genes were overexpressed in tumor and group 2, in which the genes were down regulated in tumor samples.
CONCLUSION: We found that in each group, the difference in the SUZ12 and CBX8 genes expression were significantly divergent between tumors and their marginal tissues. It means that the regulatory mechanisms involved in developing and controlling the process of gastric cancer pathogenesis is more complex than it thought. These results also bring new evidence on the possible double origin for gastric cancer development, bone-marrow-derived cells and tissue stem cells.

Prieto-Granada CN, Wiesner T, Messina JL, et al.
Loss of H3K27me3 Expression Is a Highly Sensitive Marker for Sporadic and Radiation-induced MPNST.
Am J Surg Pathol. 2016; 40(4):479-89 [PubMed] Free Access to Full Article Related Publications
Most malignant peripheral nerve sheath tumors (MPNSTs) exhibit combined inactivation of NF1, CDKN2A, and polycomb repressive complex 2 component genes (Embryonic Ectoderm Development [EED] and Suppressor of Zeste 12 [SUZ12]). Mutations in EED and SUZ12 induce loss of trimethylation at lysine 27 of histone 3 (H3K27me3), with subsequent aberrant transcriptional activation of polycomb repressive complex 2-repressed homeobox master regulators. These findings prompted us to investigate the performance of an anti-H3K27me3 monoclonal antibody clone C36B11 as an immunohistochemical marker for MPNSTs. We assessed the C36B11 reactivity pattern in a pathologically and genetically well-characterized cohort of 68 MPNSTs, spanning various clinical presentations, such as type 1 neurofibromatosis (NF1), radiotherapy, and sporadic MPNSTs. We found that 69% (n=47) of all MPNSTs demonstrated loss of H3K27me3 expression, with 42 (61%) showing complete loss and 5 (7%) showing partial loss, whereas 31% (n=21) retained H3K27me3 expression. Among the NF1-related high-grade MPNSTs, 60% demonstrated loss of expression. In contrast, the majority of both sporadic (95%) and radiotherapy-related (91%) MPNSTs showed loss of H3K27me3 expression. Two of the 3 low-grade MPNSTs and all neurofibromas showed retained expression. Furthermore, all 5 epithelioid MPNSTs retained H3K27me3 labeling. The specificity of H3K27me3 loss as a marker for MPNSTs was studied by testing a large spectrum of lesions included in MPNST differential diagnosis, such as spindle/desmoplastic melanomas, synovial sarcomas, myoepithelial tumors, and other mesenchymal neoplasms, all of which retained expression of H3K27me3. We conclude that immunohistochemical analysis of H3K27me3 has good sensitivity and robust specificity for the diagnosis of MPNST, particularly outside of NF1 clinical history, which represents the most challenging diagnostic setting.

Hatta M, Naganuma K, Kato K, Yamazaki J
3-Deazaneplanocin A suppresses aggressive phenotype-related gene expression in an oral squamous cell carcinoma cell line.
Biochem Biophys Res Commun. 2015 Dec 4-11; 468(1-2):269-73 [PubMed] Related Publications
In tumor tissues, alterations of gene expression caused by aberrant epigenetic modifications confer phenotypic diversity on malignant cells. Although 3-deazaneplanocin A (DZNep) has been shown to reactivate tumor suppressor genes in several cancer cells, it remains unclear whether DZNep attenuates the malignant phenotypes of oral squamous cell carcinoma (OSCC) cells. In this study, we investigated the effect of DZNep on the expression of genes related to aggressive phenotypes, such as epithelial-mesenchymal transition, in OSCC cells. We found that DZNep reduced the cellular levels of polycomb group proteins (EZH2, SUZ12, BMI1, and RING1A) and the associated trimethylation of Lys27 on histone H3 and monoubiquitination of Lys119 on histone H2A in the poorly differentiated OSCC cell line SAS. Immunocytochemical staining demonstrated that DZNep induced the reorganization of filamentous actin and the membrane localization of E-cadherin associated with cell-cell adhesions. We also found an inhibitory effect of DZNep on cell proliferation using a WST assay. Finally, quantitative RT-PCR analysis demonstrated that genes involved in the aggressive phenotypes (TWIST2, EGFR, ACTA2, TGFB1, WNT5B, and APLIN) were down-regulated, whereas epithelial phenotype genes (CDH1, CLDN4, IVL, and TGM1) were up-regulated in SAS cells treated with DZNep. Collectively, our findings suggest that DZNep reverses the aggressive characteristics of OSCC cells through the dynamic regulation of epithelial plasticity via the reprogramming of gene expression patterns.

Conway E, Healy E, Bracken AP
PRC2 mediated H3K27 methylations in cellular identity and cancer.
Curr Opin Cell Biol. 2015; 37:42-8 [PubMed] Related Publications
The Polycomb Repressive Complex 2 (PRC2) is a multiprotein chromatin modifying complex that is essential for vertebrate development and differentiation. It is composed of a trimeric core of SUZ12, EED and EZH1/2 and is responsible for catalysing both di-methylation and tri-methylation of Histone H3 at lysine 27 (H3K27me2/3). Both H3K27 methylations contribute to the role of PRC2 in maintaining cellular identity. In all cell types, the H3K27me3 modification is associated with repression of genes encoding regulators of alternative lineages. The less well-characterised H3K27me2 modification is ubiquitous throughout the genome and is thought to act like a protective blanket to maintain the repression of non-H3K27me3 associated genes and cell-type-specific enhancers of alternative lineages. Recent cancer genome sequencing studies highlighted that several genes encoding PRC2 components as well as Histone H3 are mutated in multiple cancer types. Intriguingly, these cancers have changes in the global levels of the H3K27me2 and H3K27me3 modifications as well as genome-wide redistributions. Exciting new studies suggest that these changes confer context dependent blocks in cellular differentiation and increased vulnerability to aberrant cancer signalling pathways.

Jiao L, Liu X
Structural basis of histone H3K27 trimethylation by an active polycomb repressive complex 2.
Science. 2015; 350(6258):aac4383 [PubMed] Free Access to Full Article Related Publications
Polycomb repressive complex 2 (PRC2) catalyzes histone H3K27 trimethylation (H3K27me3), a hallmark of gene silencing. Here we report the crystal structures of an active PRC2 complex of 170 kilodaltons from the yeast Chaetomium thermophilum in both basal and stimulated states, which contain Ezh2, Eed, and the VEFS domain of Suz12 and are bound to a cancer-associated inhibiting H3K27M peptide and a S-adenosyl-l-homocysteine cofactor. The stimulated complex also contains an additional stimulating H3K27me3 peptide. Eed is engulfed by a belt-like structure of Ezh2, and Suz12(VEFS) contacts both of these two subunits to confer an unusual split active SET domain for catalysis. Comparison of PRC2 in the basal and stimulated states reveals a mobile Ezh2 motif that responds to stimulation to allosterically regulate the active site.

Liu W, Liu Y, Liu H, et al.
Tumor Suppressive Function of p21-activated Kinase 6 in Hepatocellular Carcinoma.
J Biol Chem. 2015; 290(47):28489-501 [PubMed] Free Access to Full Article Related Publications
Our previous studies identified the oncogenic role of p21-activated kinase 1 (PAK1) in hepatocellular carcinoma (HCC) and renal cell carcinoma (RCC). Contrarily, PAK6 was found to predict a favorable prognosis in RCC patients. Nevertheless, the ambiguous tumor suppressive function of PAK6 in hepatocarcinogenesis remains obscure. Herein, decreased PAK6 expression was found to be associated with tumor node metastasis stage progression and unfavorable overall survival in HCC patients. Additionally, overexpression and silence of PAK6 experiments showed that PAK6 inhibited xenografted tumor growth in vivo, and restricted cell proliferation, colony formation, migration, and invasion and promoted cell apoptosis and anoikis in vitro. Moreover, overexpression of kinase dead and nuclear localization signal deletion mutants of PAK6 experiments indicated the tumor suppressive function of PAK6 was partially dependent on its kinase activity and nuclear translocation. Furthermore, gain or loss of function in polycomb repressive complex 2 (PRC2) components, including EZH2, SUZ12, and EED, elucidated epigenetic control of H3K27me3-arbitrated PAK6 down-regulation in hepatoma cells. More importantly, negative correlation between PAK6 and EZH2 expression was observed in hepatoma tissues from HCC patients. These data identified the tumor suppressive role and potential underlying mechanism of PAK6 in hepatocarcinogenesis.

Choi YJ, Jung SH, Kim MS, et al.
Genomic landscape of endometrial stromal sarcoma of uterus.
Oncotarget. 2015; 6(32):33319-28 [PubMed] Free Access to Full Article Related Publications
Although recurrent gene fusions such as JAZF1-JJAZ1 are considered driver events for endometrial stromal sarcoma (ESS) development, other genomic alterations remain largely unknown. In this study, we performed whole-exome sequencing, transcriptome sequencing and copy number profiling for five ESSs (three low-grade ESS (LG-ESS) and two undifferentiated uterine sarcomas (UUSs)). All three LG-ESSs exhibited either one of JAZF1-SUZ12, JAZF1-PHF1 and MEAF6-PHF1 fusions, whereas the two UUSs did not. All ESSs except one LG-ESS exhibited copy number alterations (CNAs), many of which encompassed cancer-related genes. In UUSs, five CNAs encompassing cancer-related genes (EZR, CDH1, RB1, TP53 and PRKAR1A) accompanied their expressional changes, suggesting that they might stimulate UUS development. We found 81 non-silent mutations (35 from LG-ESSs and 46 from UUSs) that included 15 putative cancer genes catalogued in cancer-related databases, including PPARG and IRF4 mutations. However, they were non-recurrent and did not include any well-known mutations, indicating that point mutations may not be a major driver for ESS development. Our data show that gene fusions and CNAs are the principal drivers for LG-ESS and USS, respectively, but both may require additional genomic alterations including point mutations. These differences may explain the different biologic behaviors between LG-ESS and UUS. Our findings suggest that ESS development requires point mutations and CNAs as well as the gene fusions.

Wang H, Ge S, Qian G, et al.
Restoration of IGF2 imprinting by polycomb repressive complex 2 docking factor SUZ12 in colon cancer cells.
Exp Cell Res. 2015; 338(2):214-21 [PubMed] Related Publications
The insulin-like growth factor II (IGF2) gene is aberrantly expressed in tumors as a result of loss of imprinting (LOI). Reactivation of the normally-suppressed maternal allele may lead to IGF2 upregulation and increased tumor growth, particularly in colon cancer. However, the mechanisms underlying IGF2 LOI in tumors are poorly defined. In this report, we identified polycomb repressive complex 2 (PRC2) docking factor SUZ12 as a critical factor in regulating IGF2 imprinting in tumors. Human colon cancer cell lines (HRT18 and HT29) show loss of IGF2 imprinting. Ectopic expression of SUZ12 restored normal monoallelic expression of IGF2 in these two colon cancer cell lines. Using chromatin immunoprecipitation (ChIP) and chromatin conformation capture (3C), we found that the virally-expressed SUZ12 bound to IGF2 promoters, coordinating with endogenous CTCF to orchestrate a long range intrachromosomal loop between the imprinting control region (ICR) and the IGF2 promoters. The histone methyltransferase EZH2 was recruited to the IGF2 promoters, where it induced H3K27 hypermethylation, suppressing one allele, leading to the restoration of IGF2 imprinting. These data demonstrate that SUZ12 is a key molecule in the regulation of monoallelic expression of IGF2, suggesting a novel epigenetic therapeutic strategy for modulating IGF2 production in human tumors.

Kim SH, Yang WI, Min YH, et al.
The role of the polycomb repressive complex pathway in T and NK cell lymphoma: biological and prognostic implications.
Tumour Biol. 2016; 37(2):2037-47 [PubMed] Related Publications
Polycomb repressive complex 2 (PRC2; formed by EZH2, SUZ12, and EED protein subunits) and PRC1 (BMI1 protein) induce gene silencing through histone modification, primarily H3K27me3, and deregulation of PRC pathways leads to tumorigenesis. In the present study, activation of PRC2, H3K27me3, and BMI1 was investigated by immunohistochemistry in 175 cases of T and natural killer (NK) cell lymphoma. Activation of PRC proteins was analyzed according to c-MYC activation, Epstein-Barr virus (EBV) infection, CD30 activation, and survival. Among all T and NK cell lymphomas, high expression rates of 54.7 % for EZH2, 33.3 % for SUZ12, 85.7 % for EED, 40.5 % for H3K27me3, and 30.9 % for BMI1 were discovered. Activation of PRC2, H3K27me3, and BMI1 showed positive correlations (P < 0.05). Activation of c-MYC was associated with activation of SUZ12 and triple coactivation of all PRC2 protein subunits (EZH2(high)/SUZ12(high)/EED(high)) (P < 0.05). In EBV-positive tumors, activation of EZH2 and H3K27me3 showed greater association (P < 0.05). H3K27me3 and BMI1 showed a negative association in tumors expressing CD30 (P < 0.05). With respect to survival, BMI1 activation was independently associated with poor prognosis in T and NK cell lymphomas (P = 0.002). In conclusion, T and NK cell lymphomas were associated with activation of PRC pathway markers, for which c-MYC activation and EBV infection could be suggested as possible causes. PRC pathway markers may be potential therapeutic targets and prognostic markers in T and NK cell lymphoma.

Reardon ES, Hong JA, Straughan DM, et al.
Pulmonary Metastases Exhibit Epigenetic Clonality: Implications for Precision Cancer Therapy.
Ann Thorac Surg. 2015; 100(5):1839-48; discussion 1848 [PubMed] Related Publications
BACKGROUND: Development of effective cancer therapies may be limited by intratumoral heterogeneity, which facilitates outgrowth and organ-specific dissemination of treatment resistant clones. At present, limited information is available regarding epigenetic landscapes of pulmonary metastases. This study was undertaken to characterize epigenetic signatures of pulmonary metastases and to identify potential therapeutic targets.
METHODS: RNA and DNA were extracted from 65 pulmonary metastases resected from 12 patients (5 with sarcoma, 7 with adrenocortical carcinoma). Quantitative reverse transcription polymerase chain reaction techniques were used to evaluate expression levels of cancer-testis (CT) genes (NY-ESO-1, MAGE-A3, MAGE-A9, MAGE-A12, GAGE1, CT-45, SSX-1, and SSX-2), tumor suppressor (TS) genes (p16 and RASSF1A), and genes encoding epigenetic modifiers (DNMT1, DNMT3A, DNMT3B, EZH2, EED, and SUZ12), aberrantly expressed in human malignant diseases. Pyrosequencing techniques were used to quantitate DNA methylation levels in LINE1, NBL2, and D4Z4 repetitive sequences and promoter methylation status of differentially regulated genes. Results of these analyses were compared with a standardized panel of normal lung tissues.
RESULTS: Pulmonary metastases exhibited histologically related and patient-specific global DNA demethylation. Significant interpatient heterogeneity of gene expression was observed even among patients with similar tumor histologic features. Epigenetic signatures appeared consistent among metastases from the same patient, irrespective of the time of resection (synchronous/metachronous) or the anatomic location. EZH2, EED, and SUZ12 (core components of Polycomb repressive complex-2 [PRC-2]) were upregulated in the majority of metastases.
CONCLUSIONS: Pulmonary metastases exhibit patient-specific epigenetic clonality, which may be exploited for precision therapies targeting aberrant CT or TS gene expression. PRC-2 may be a shared target for epigenetic therapy of pulmonary metastases.

Kunz JB, Rausch T, Bandapalli OR, et al.
Pediatric T-cell lymphoblastic leukemia evolves into relapse by clonal selection, acquisition of mutations and promoter hypomethylation.
Haematologica. 2015; 100(11):1442-50 [PubMed] Free Access to Full Article Related Publications
Relapsed precursor T-cell acute lymphoblastic leukemia is characterized by resistance against chemotherapy and is frequently fatal. We aimed at understanding the molecular mechanisms resulting in relapse of T-cell acute lymphoblastic leukemia and analyzed 13 patients at first diagnosis, remission and relapse by whole exome sequencing, targeted ultra-deep sequencing, multiplex ligation dependent probe amplification and DNA methylation array. Compared to primary T-cell acute lymphoblastic leukemia, in relapse the number of single nucleotide variants and small insertions and deletions approximately doubled from 11.5 to 26. Targeted ultra-deep sequencing sensitively detected subclones that were selected for in relapse. The mutational pattern defined two types of relapses. While both are characterized by selection of subclones and acquisition of novel mutations, 'type 1' relapse derives from the primary leukemia whereas 'type 2' relapse originates from a common pre-leukemic ancestor. Relapse-specific changes included activation of the nucleotidase NT5C2 resulting in resistance to chemotherapy and mutations of epigenetic modulators, exemplified by SUZ12, WHSC1 and SMARCA4. While mutations present in primary leukemia and in relapse were enriched for known drivers of leukemia, relapse-specific changes revealed an association with general cancer-promoting mechanisms. This study thus identifies mechanisms that drive progression of pediatric T-cell acute lymphoblastic leukemia to relapse and may explain the characteristic treatment resistance of this condition.

Qiu M, Xu Y, Wang J, et al.
A novel lncRNA, LUADT1, promotes lung adenocarcinoma proliferation via the epigenetic suppression of p27.
Cell Death Dis. 2015; 6:e1858 [PubMed] Free Access to Full Article Related Publications
Long noncoding RNAs (lncRNAs) are known to regulate the development and progression of various cancers. However, few lncRNAs have been well characterized in lung adenocarcinoma (LUAD). Here, we identified the expression profile of lncRNAs and protein-coding genes via microarrays analysis of paired LUAD tissues and adjacent non-tumor tissues from five female non-smokes with LUAD. A total of 498 lncRNAs and 1691 protein-coding genes were differentially expressed between LUAD tissues and paired adjacent normal tissues. A novel lncRNA, LUAD transcript 1 (LUADT1), which is highly expressed in LUAD and correlates with T stage, was characterized. Both in vitro and in vivo data showed that LUADT1 knockdown significantly inhibited proliferation of LUAD cells and induced cell cycle arrest at the G0-G1 phase. Further analysis indicated that LUADT1 may regulate cell cycle progression by epigenetically inhibiting the expression of p27. RNA immunoprecipitation and chromatin immunoprecipitation assays confirmed that LUADT1 binds to SUZ12, a core component of polycomb repressive complex 2, and mediates the trimethylation of H3K27 at the promoter region of p27. The negative correlation between LUADT1 and p27 expression was confirmed in LUAD tissue samples. These data suggested that a set of lncRNAs and protein-coding genes were differentially expressed in LUAD. LUADT1 is an oncogenic lncRNA that regulates LUAD progression, suggesting that dysregulated lncRNAs may serve as key regulatory factors in LUAD progression.

D'Angelo V, Iannotta A, Ramaglia M, et al.
EZH2 is increased in paediatric T-cell acute lymphoblastic leukemia and is a suitable molecular target in combination treatment approaches.
J Exp Clin Cancer Res. 2015; 34:83 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: T-cell Acute Lymphoblastic Leukemia (ALL) represents about 10-15 % of pediatric ALL cases. EZH2, one of the components of Polycomb group proteins (PRC2) complex, catalyzes the trimethylation of histone H3 lysine 27 that is associated with transcriptional repression and tumor development.
METHODS: We examined the expression levels of PRC2 complex in primary samples of T cells ALL at diagnosis by western blotting and real time PCR. We evaluated the effect of 3-deazaneplanocin-A (DZNep), an EZH2 inhibitor, alone and in combination with Daunoblastine on cell viability, apoptotic death and cell cycle distribution of T cell established Jurkat cell line.
RESULTS: EZH2 was expressed in 75 % samples at different extents mainly with high expression level. SUZ12 was expressed in 60 % samples and EED in all samples, respectively. The Kaplan-Meier analysis shows that T-ALL expressing EZH2 had a lower probability of disease-free survival (DFS) compared to T-ALL negative for EZH2 (23 % vs 100 %) (p = 0.01). The EZH2 inhibitor DZNep used in combination with Daunoblastine was synergistic in inducing growth inhibition and increasing the apoptosis in T-ALL Jurkat cells at 48 and 72 h paralleled by EZH2 decreased expression. Moreover, the combination decreased the activity of Erk-1/2 proliferation enzymes with no effects on Akt survival pathway.
CONCLUSIONS: The evaluation of EZH2 expression in pediatric T-ALL can be useful in predict the clinical outcome of the patients and EZH2 can be a useful target to improve the efficacy of conventional chemotherapy in this subset of patients with bad prognosis.

Lee SR, Roh YG, Kim SK, et al.
Activation of EZH2 and SUZ12 Regulated by E2F1 Predicts the Disease Progression and Aggressive Characteristics of Bladder Cancer.
Clin Cancer Res. 2015; 21(23):5391-403 [PubMed] Related Publications
PURPOSE: Previous study identified E2F1 as a key mediator of non-muscle-invasive bladder cancer (NMIBC) progression. The aim of this study was to identify the E2F1-related genes associated with poor prognosis and aggressive characteristics of bladder cancer.
EXPERIMENTAL DESIGN: Microarray analysis was performed to find E2F1-related genes associated with tumor progression and aggressiveness in the gene expression data from 165 primary patients with bladder cancer. The biologic activity of E2F1-related genes in tumor progression and aggressiveness was confirmed with experimental assays using bladder cancer cells and tumor xenograft assay.
RESULTS: The expression of E2F1 was significantly associated with EZH2 and SUZ12. The overexpression of E2F1, EZH2, and SUZ12 enhanced cancer progression including cell colony formation, migration, and invasiveness. Knockdown of these genes reduced motility, blocked invasion, and decreased tumor size in vivo. E2F1 bound the proximal EZH2 and SUZ12 promoter to activate transcription, suggesting that E2F1 and its downstream effectors, EZH2 and SUZ12, could be important mediators for the cancer progression. In addition, we confirmed an association between these genes and aggressive characteristics. Interestingly, the treatment of anticancer drugs to the cells overexpressing E2F1, EZH2, and SUZ12 induced the expression of CD44, KLF4, OCT4, and ABCG2 known as cancer stem cell (CSC)-related genes.
CONCLUSIONS: The link between E2F1, EZH2, and/or SUZ12 revealed that E2f1 directly regulates transcription of the EZH2 and SUZ12 genes. The signature of E2F1-EZH2-SUZ12 shows a predictive value for prognosis in bladder tumors and the E2F1-EZH2-SUZ12-driven transcriptional events may regulate the cancer aggressiveness and chemo-resistance, which may provide opportunity for development of new treatment modalities.

Sharma S, Mandal P, Sadhukhan T, et al.
Bridging Links between Long Noncoding RNA HOTAIR and HPV Oncoprotein E7 in Cervical Cancer Pathogenesis.
Sci Rep. 2015; 5:11724 [PubMed] Free Access to Full Article Related Publications
Human Papillomavirus (HPV) type 16 oncoprotein E7 plays a major role in cervical carcinogenesis by interacting with and functionally inactivating various host regulatory molecules. Long noncoding RNA (lncRNA) HOTAIR is one such regulator that recruits chromatin remodelling complex PRC2, creating gene silencing H3K27 me3 marks. Hence, we hypothesized that HOTAIR could be a potential target of E7, in HPV16 related cervical cancers (CaCx). We identified significant linear trend of progressive HOTAIR down-regulation through HPV negative controls, HPV16 positive non-malignants and CaCx samples. Majority of CaCx cases portrayed HOTAIR down-regulation in comparison to HPV negative controls, with corresponding up-regulation of HOTAIR target, HOXD10, and enrichment of cancer related pathways. However, a small subset had significantly higher HOTAIR expression, concomitant with high E7 expression and enrichment of metastatic pathways. Expression of HOTAIR and PRC2-complex members (EZH2 and SUZ12), showed significant positive correlation with E7 expression in CaCx cases and E7 transfected C33A cell line, suggestive of interplay between E7 and HOTAIR. Functional inactivation of HOTAIR by direct interaction with E7 could also be predicted by in silico analysis and confirmed by RNA-Immunoprecipitation. Our study depicts one of the causal mechanisms of cervical carcinogenesis by HPV16 E7, through modulation of HOTAIR expression and function.

Liu YW, Sun M, Xia R, et al.
LincHOTAIR epigenetically silences miR34a by binding to PRC2 to promote the epithelial-to-mesenchymal transition in human gastric cancer.
Cell Death Dis. 2015; 6:e1802 [PubMed] Free Access to Full Article Related Publications
lncRNAs play important roles in the epigenetic regulation of carcinogenesis and progression. Previous studies suggest that HOTAIR contributes to gastric cancer (GC) development, and the overexpression of HOTAIR predicts a poor prognosis. In this study, we found that HOTAIR was more highly expressed in diffuse-type GC than in intestinal type (P=0.048). In the diffuse type, there is significant relationship between HOTAIR expression and DFS (P<0.001). CDH1 was downregulated in diffuse-type GC tissues (P=0.0007) and showed a negative relationship with HOTAIR (r(2)=0.154, P=0.0354). In addition, HOTAIR knockdown significantly repressed migration, invasion and metastasis both in vitro and vivo and reversed the epithelial-to-mesenchymal transition in GC cells. We also showed that HOTAIR recruiting and binding to PRC2 epigenetically represses miR34a, which controls the targets C-Met (HGF/C-Met/Snail pathway) and Snail, thus contributing to GC cell-EMT process and accelerating tumor metastasis. Moreover, it is demonstrated that HOTAIR crosstalk with microRNAs during epigenetic regulation. Our results suggest that HOTAIR acts as an EMT regulator and may be a candidate prognostic biomarker and a target for new therapies in GC patients.

Liu C, Li S, Dai X, et al.
PRC2 regulates RNA polymerase III transcribed non-translated RNA gene transcription through EZH2 and SUZ12 interaction with TFIIIC complex.
Nucleic Acids Res. 2015; 43(13):6270-84 [PubMed] Free Access to Full Article Related Publications
Polycomb repression complex 2 (PRC2) component EZH2 tri-methylates H3K27 and exerts epigenetic repression on target gene expression. EZH2-mediated epigenetic control of RNA polymerase II (Pol II) transcribed coding gene transcription has been well established. However, little is known about EZH2-mediated epigenetic regulation of RNA polymerase III (Pol III) transcription. Here we present a paradigm that EZH2 is involved in the repression of Pol III transcription via interaction with transcriptional factor complex IIIC (TFIIIC). EZH2 and H3K27me3 co-occupy the promoter of tRNA(Tyr), 5S rRNA and 7SL RNA genes. Depletion of EZH2 or inhibition of EZH2 methyltransferase activity led to upregulation of Pol III target gene transcription. EZH2-mediated repression of Pol III transcribed gene expression requires presence of SUZ12. SUZ12 was able to interact with TFIIIC complex and knockdown of SUZ12 decreased occupancy of EZH2 and H3K27me3 at the promoter of Pol III target genes. Our findings pointed out a previously unidentified role of PRC2 complex in suppressing transcription of Pol III transcribed non-translated RNA genes, putting Pol III on a new layer of epigenetic regulation.

Abou El Hassan M, Huang K, Eswara MB, et al.
Cancer Cells Hijack PRC2 to Modify Multiple Cytokine Pathways.
PLoS One. 2015; 10(6):e0126466 [PubMed] Free Access to Full Article Related Publications
Polycomb Repressive Complex 2 (PRC2) is an epigenetic regulator induced in many cancers. It is thought to drive tumorigenesis by repressing division, stemness, and/or developmental regulators. Cancers evade immune detection, and diverse immune regulators are perturbed in different tumors. It is unclear how such cell-specific effects are coordinated. Here, we show a profound and cancer-selective role for PRC2 in repressing multiple cytokine pathways. We find that PRC2 represses hundreds of IFNγ stimulated genes (ISGs), cytokines and cytokine receptors. This target repertoire is significantly broadened in cancer vs non-cancer cells, and is distinct in different cancer types. PRC2 is therefore a higher order regulator of the immune program in cancer cells. Inhibiting PRC2 with either RNAi or EZH2 inhibitors activates cytokine/cytokine receptor promoters marked with bivalent H3K27me3/H3K4me3 chromatin, and augments responsiveness to diverse immune signals. PRC2 inhibition rescues immune gene induction even in the absence of SWI/SNF, a tumor suppressor defective in ~20% of human cancers. This novel PRC2 function in tumor cells could profoundly impact the mechanism of action and efficacy of EZH2 inhibitors in cancer treatment.

Zu B, Shi Y, Xu M, et al.
ARE/SUZ12 dual specifically-regulated adenoviral TK/GCV system for CML blast crisis cells.
J Exp Clin Cancer Res. 2015; 34:56 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Treatment of blast phase chronic myeloid leukemia (BP-CML) remains a challenge, and the median survival is less than 6 months. Because effective treatments are lacking, we studied tight targeting of blast crisis CML cells using adenoviral (Ad) vectors expressing a HSV-TK system under dual control of a specific SUZ12 promoter and an antioxidant response element (ARE).
METHODS: A potential SUZ12 promoter fragment was designed with bioinformatics databases and identified with a luciferase assay. Next, we cloned the ARE element of the NQO1 gene and developed Ad vectors expressing TK kinase or luciferase under the dual control of a specific SUZ12 promoter and an ARE element. An in vitro transfection assay with Ad-ARE/SUZ12-Luc was used to determine promoter activity of ARE/SUZ12 regulatory element in blast crisis CML cells. After incubating human BP-CML-derived cells with Ad-ARE/SUZ12-TK and ganciclovir, Western blot, CCK8, Immunofluorescent assays and Annexin V assays were conducted to assess the efficacy of an ARE/SUZ12 dual-specific TK/GCV system for BP-CML cell lines.
RESULTS: Here, luciferase data confirmed significantly higher and specificer promoter activity of the ARE/SUZ12 composite component in CML blast crisis-derived cell lines (K562, KCL22, and K562/G01) compared to HepG2 cells, and Ad-AS-TK/GCV system could exhibit enhanced apoptotic effects and decreased cell viability for BP-CML cell lines. Additionally, Ad-AS-TK/GCV system altered expression of cycle-related and apoptosis-related proteins in BP-CML cell lines.
CONCLUSIONS: Thus, ARE/SUZ12 dual targeting TK/GCV system was effective in killing BP-CML cells. Moreover, efficacy and specificity of CML cell eradication were enhanced by synergistic effects of ARE/SUZ12 dual-specific regulation. We conclude that suicide gene-targeted therapy might hold promise for BP-CML treatment.

O'Leary VB, Ovsepian SV, Carrascosa LG, et al.
PARTICLE, a Triplex-Forming Long ncRNA, Regulates Locus-Specific Methylation in Response to Low-Dose Irradiation.
Cell Rep. 2015; 11(3):474-85 [PubMed] Related Publications
Exposure to low-dose irradiation causes transiently elevated expression of the long ncRNA PARTICLE (gene PARTICLE, promoter of MAT2A-antisense radiation-induced circulating lncRNA). PARTICLE affords both a cytosolic scaffold for the tumor suppressor methionine adenosyltransferase (MAT2A) and a nuclear genetic platform for transcriptional repression. In situ hybridization discloses that PARTICLE and MAT2A associate together following irradiation. Bromouridine tracing and presence in exosomes indicate intercellular transport, and this is supported by ex vivo data from radiotherapy-treated patients. Surface plasmon resonance indicates that PARTICLE forms a DNA-lncRNA triplex upstream of a MAT2A promoter CpG island. We show that PARTICLE represses MAT2A via methylation and demonstrate that the radiation-induced PARTICLE interacts with the transcription-repressive complex proteins G9a and SUZ12 (subunit of PRC2). The interplay of PARTICLE with MAT2A implicates this lncRNA in intercellular communication and as a recruitment platform for gene-silencing machineries through triplex formation in response to irradiation.

Fan H, Zhang H, Pascuzzi PE, Andrisani O
Hepatitis B virus X protein induces EpCAM expression via active DNA demethylation directed by RelA in complex with EZH2 and TET2.
Oncogene. 2016; 35(6):715-26 [PubMed] Free Access to Full Article Related Publications
Chronic hepatitis B virus (HBV) infection is a major risk factor for developing hepatocellular carcinoma (HCC), and HBV X protein (HBx) acts as cofactor in hepatocarcinogenesis. In liver tumors from animals modeling HBx- and HBV-mediated hepatocarcinogenesis, downregulation of chromatin regulating proteins SUZ12 and ZNF198 induces expression of several genes, including epithelial cell adhesion molecule (EpCAM). EpCAM upregulation occurs in HBV-mediated HCCs and hepatic cancer stem cells, by a mechanism not understood. Herein we demonstrate HBx induces EpCAM expression via active DNA demethylation. In hepatocytes, EpCAM is silenced by polycomb repressive complex 2 (PRC2) and ZNF198/LSD1/Co-REST/HDAC1 chromatin-modifying complexes. Cells with stable knockdown of SUZ12, an essential PRC2 subunit, upon HBx expression demethylate a CpG dinucleotide located adjacent to NF-κB/RelA half-site. This NF-κB/RelA site is in a CpG island downstream from EpCAM transcriptional start site (TSS). Chromatin immunoprecipitation (ChIP) assays demonstrate HBx-dependent RelA occupancy of NF-κB half-site, whereas RelA knockdown suppresses CpG demethylation and EpCAM expression. Tumor necrosis factor-α activates RelA, propagating demethylation to nearby CpG sites, shown by sodium bisulfite sequencing. RelA-dependent demethylation occurring upon HBx expression requires methyltrasferase EZH2, TET2 a key factor in cytosine demethylation and inactive DNMT3L, shown by knockdown assays and sodium bisulfite sequencing. Co-immunoprecipitations and sequential ChIP assays demonstrate that RelA in the presence of HBx forms a complex with EZH2, TET2 and DNMT3L, although the role of DNMT3L remains to be understood. Interestingly, the human EpCAM gene also has a CpG island downstream from its TSS, and a NF-κB-binding site flanked by CpGs. HepG2 cells derived from human HCC exhibit demethylation of these NF-κB-flanking CpG sites, and HBV replication propagates demethylation to nearby CpG sites. DLK1, another PRC2 target gene, also upregulated in HBV-mediated HCCs, is demethylated in liver tumors at CpG dinucleotides flanking the NF-κB-binding sequence, supporting that this active DNA demethylation mechanism functions during oncogenic transformation.

Abou El Hassan M, Yu T, Song L, Bremner R
Polycomb Repressive Complex 2 Confers BRG1 Dependency on the CIITA Locus.
J Immunol. 2015; 194(10):5007-13 [PubMed] Related Publications
CIITA (or MHC2TA) coordinates constitutive and IFN-γ-induced expression of MHC class II genes. IFN-γ responsiveness of CIITA requires BRG1 (SMARCA4), the ATPase engine of the chromatin remodeling SWI/SNF complex (also called BAF). SWI/SNF is defective in many human cancers, providing a mechanism to explain IFN-γ resistance. BRG1 dependency is mediated through remote elements. Short CIITA reporters lacking these elements respond to IFN-γ, even in BRG1-deficient cells, suggesting that BRG1 counters a remote repressive influence. The nature of this distal repressor is unknown, but it would represent a valuable therapeutic target to reactivate IFN-γ responsiveness in cancer. In this article, we show that the polycomb repressive complex 2 (PRC2) components EZH2 and SUZ12, as well as the associated histone mark H3K27me3, are codetected at interenhancer regions across the CIITA locus. IFN-γ caused a BRG1-dependent reduction in H3K27me3, associated with nucleosome displacement. SUZ12 knockdown restored IFN-γ responsiveness in BRG1-null cells, and it mimicked the ability of BRG1 to induce active histone modifications (H3K27ac, H3K4me) at the -50-kb enhancer. Thus, PRC2 confers BRG1 dependency on the CIITA locus. Our data suggest that, in addition to its known roles in promoting stemness and proliferation, PRC2 may inhibit immune surveillance, and it could be targeted to reactivate CIITA expression in SWI/SNF deficient cancers.

Zhang H, Diab A, Fan H, et al.
PLK1 and HOTAIR Accelerate Proteasomal Degradation of SUZ12 and ZNF198 during Hepatitis B Virus-Induced Liver Carcinogenesis.
Cancer Res. 2015; 75(11):2363-74 [PubMed] Free Access to Full Article Related Publications
Elucidating mechanisms of hepatitis B virus (HBV)-mediated hepatocarcinogenesis is needed to gain insights into the etiology and treatment of liver cancer. Cells where HBV is replicating exhibit increased expression of Plk1 kinase and reduced levels of two transcription repression factors, SUZ12 and ZNF198. SUZ12 is an essential subunit of the transcription repressive complex PRC2. ZNF198 stabilizes the transcription repressive complex composed of LSD1, Co-REST, and HDAC1. These two transcription repressive complexes are held together by binding the long noncoding RNA HOTAIR. In this study, we linked these regulatory events mechanistically by showing that Plk1 induces proteasomal degradation of SUZ12 and ZNF198 by site-specific phosphorylation. Plk1-dependent ubiquitination of SUZ12 and ZNF198 was enhanced by expression of HOTAIR, significantly reducing SUZ12 and ZNF198 stability. In cells expressing the HBV X protein (HBx), downregulation of SUZ12 and ZNF198 mediated global changes in histone modifications. In turn, HBx-expressing cells propagated an altered chromatin landscape after cell division, as exemplified by changes in histone modifications of the EpCAM promoter, a target of PRC2 and LSD1/Co-REST/HDAC1 complexes. Notably, liver tumors from X/c-myc bitransgenic mice exhibited downregulation of SUZ12 and ZNF198 along with elevated expression of Plk1, HOTAIR, and EpCAM. Clinically, similar effects were documented in a set of HBV-related liver tumors consistent with the likelihood that downregulation of SUZ12 and ZNF198 leads to epigenetic reprogramming of infected hepatocytes. Because both Plk1 and HOTAIR are elevated in many human cancers, we propose that their combined effects are involved in epigenetic reprogramming associated broadly with oncogenic transformation.

Xie Z, Cai L, Li R, et al.
Down-regulation of miR-489 contributes into NSCLC cell invasion through targeting SUZ12.
Tumour Biol. 2015; 36(8):6497-505 [PubMed] Related Publications
microRNAs are small, non-coding RNAs that contribute into various biological processes during cancer progression. However, the potential role of miR-489 in the development of Non-Small Cell Lung Cancer (NSCLC) is not demonstrated. In present study, miR-489 was down-regulated both in tumor tissues and cells. Inhibition of miR-489 promoted cells invasion by using an invasion assay. Furthermore, miR-489 could regulate SUZ12 as shown by luciferase reporter and Western blot assays. Aberrant miR-489 expression could regulate the molecular changes (E-cadherin, N-cadherin, and Vimentin) of epithelial mesenchymal transition (EMT). In conclusion, our study revealed that miR-489 may play an essential role in the progression of NSCLC.

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