ETS2

Gene Summary

Gene:ETS2; ETS proto-oncogene 2, transcription factor
Aliases: ETS2IT1
Location:21q22.2
Summary:This gene encodes a transcription factor which regulates genes involved in development and apoptosis. The encoded protein is also a protooncogene and shown to be involved in regulation of telomerase. A pseudogene of this gene is located on the X chromosome. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2012]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:protein C-ets-2
Source:NCBIAccessed: 13 March, 2017

Ontology:

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 13 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.

  • RTPCR
  • Gene Dosage
  • Breast Cancer
  • ETS2
  • Chromosome 21
  • Messenger RNA
  • Viral Structural Proteins
  • Mutation
  • Cervical Cancer
  • Western Blotting
  • Transcription
  • Proto-Oncogene Proteins c-ets
  • Trans-Activators
  • Promoter Regions
  • beta-Galactosidase
  • Cell Proliferation
  • Telomere
  • Transfection
  • Prostate Cancer
  • Chromosome Aberrations
  • Neoplasm Invasiveness
  • Base Sequence
  • Acute Myeloid Leukaemia
  • Oligonucleotide Array Sequence Analysis
  • Trisomy
  • Proto-Oncogene Protein c-ets-1
  • Transcriptional Regulator ERG
  • Signal Transduction
  • Leukaemia
  • Proto-Oncogene Protein c-ets-2
  • Telomerase
  • Down Syndrome
  • Molecular Sequence Data
  • DNA-Binding Proteins
  • ets-Domain Protein Elk-1
  • Transcription Factors
  • Lung Cancer
  • Repressor Proteins
  • Cancer Gene Expression Regulation
  • Proto-Oncogene Proteins
  • Single Nucleotide Polymorphism
  • Gene Expression Profiling
Tag cloud generated 13 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

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: ETS2 (cancer-related)

Chang H, Liu Y, Xue M, et al.
Synergistic action of master transcription factors controls epithelial-to-mesenchymal transition.
Nucleic Acids Res. 2016; 44(6):2514-27 [PubMed] Free Access to Full Article Related Publications
Epithelial-to-mesenchymal transition (EMT) is a complex multistep process in which phenotype switches are mediated by a network of transcription factors (TFs). Systematic characterization of all dynamic TFs controlling EMT state transitions, especially for the intermediate partial-EMT state, represents a highly relevant yet largely unexplored task. Here, we performed a computational analysis that integrated time-course EMT transcriptomic data with public cistromic data and identified three synergistic master TFs (ETS2, HNF4A and JUNB) that regulate the transition through the partial-EMT state. Overexpression of these regulators predicted a poor clinical outcome, and their elimination readily abolished TGF-β-induced EMT. Importantly, these factors utilized a clique motif, physically interact and their cumulative binding generally characterized EMT-associated genes. Furthermore, analyses of H3K27ac ChIP-seq data revealed that ETS2, HNF4A and JUNB are associated with super-enhancers and the administration of BRD4 inhibitor readily abolished TGF-β-induced EMT. These findings have implications for systematic discovery of master EMT regulators and super-enhancers as novel targets for controlling metastasis.

Yang H, Schramek D, Adam RC, et al.
ETS family transcriptional regulators drive chromatin dynamics and malignancy in squamous cell carcinomas.
Elife. 2015; 4:e10870 [PubMed] Free Access to Full Article Related Publications
Tumor-initiating stem cells (SCs) exhibit distinct patterns of transcription factors and gene expression compared to healthy counterparts. Here, we show that dramatic shifts in large open-chromatin domain (super-enhancer) landscapes underlie these differences and reflect tumor microenvironment. By in vivo super-enhancer and transcriptional profiling, we uncover a dynamic cancer-specific epigenetic network selectively enriched for binding motifs of a transcription factor cohort expressed in squamous cell carcinoma SCs (SCC-SCs). Many of their genes, including Ets2 and Elk3, are themselves regulated by SCC-SC super-enhancers suggesting a cooperative feed-forward loop. Malignant progression requires these genes, whose knockdown severely impairs tumor growth and prohibits progression from benign papillomas to SCCs. ETS2-deficiency disrupts the SCC-SC super-enhancer landscape and downstream cancer genes while ETS2-overactivation in epidermal-SCs induces hyperproliferation and SCC super-enhancer-associated genes Fos, Junb and Klf5. Together, our findings unearth an essential regulatory network required for the SCC-SC chromatin landscape and unveil its importance in malignant progression.

Capaldo BJ, Roller D, Axelrod MJ, et al.
Systems Analysis of Adaptive Responses to MAP Kinase Pathway Blockade in BRAF Mutant Melanoma.
PLoS One. 2015; 10(9):e0138210 [PubMed] Free Access to Full Article Related Publications
Fifty percent of cutaneous melanomas are driven by activated BRAFV600E, but tumors treated with RAF inhibitors, even when they respond dramatically, rapidly adapt and develop resistance. Thus, there is a pressing need to identify the major mechanisms of intrinsic and adaptive resistance and develop drug combinations that target these resistance mechanisms. In a combinatorial drug screen on a panel of 12 treatment-naïve BRAFV600E mutant melanoma cell lines of varying levels of resistance to mitogen-activated protein kinase (MAPK) pathway inhibition, we identified the combination of PLX4720, a targeted inhibitor of mutated BRaf, and lapatinib, an inhibitor of the ErbB family of receptor tyrosine kinases, as synergistically cytotoxic in the subset of cell lines that displayed the most resistance to PLX4720. To identify potential mechanisms of resistance to PLX4720 treatment and synergy with lapatinib treatment, we performed a multi-platform functional genomics analysis to profile the genome as well as the transcriptional and proteomic responses of these cell lines to treatment with PLX4720. We found modest levels of resistance correlated with the zygosity of the BRAF V600E allele and receptor tyrosine kinase (RTK) mutational status. Layered over base-line resistance was substantial upregulation of many ErbB pathway genes in response to BRaf inhibition, thus generating the vulnerability to combination with lapatinib. The transcriptional responses of ErbB pathway genes are associated with a number of transcription factors, including ETS2 and its associated cofactors that represent a convergent regulatory mechanism conferring synergistic drug susceptibility in the context of diverse mutational landscapes.

Li Y, Zhou QL, Sun W, et al.
Non-canonical NF-κB signalling and ETS1/2 cooperatively drive C250T mutant TERT promoter activation.
Nat Cell Biol. 2015; 17(10):1327-38 [PubMed] Free Access to Full Article Related Publications
Transcriptional reactivation of TERT, the catalytic subunit of telomerase, is necessary for cancer progression in about 90% of human cancers. The recent discovery of two prevalent somatic mutations-C250T and C228T-in the TERT promoter in various cancers has provided insight into a plausible mechanism of TERT reactivation. Although the two hotspot mutations create a similar binding motif for E-twenty-six (ETS) transcription factors, we show that they are functionally distinct, in that the C250T unlike the C228T TERT promoter is driven by non-canonical NF-κB signalling. We demonstrate that binding of ETS to the mutant TERT promoter is insufficient in driving its transcription but this process requires non-canonical NF-κB signalling for stimulus responsiveness, sustained telomerase activity and hence cancer progression. Our findings highlight a previously unrecognized role of non-canonical NF-κB signalling in tumorigenesis and elucidate a fundamental mechanism for TERT reactivation in cancers, which if targeted could have immense therapeutic implications.

Hannafon BN, Carpenter KJ, Berry WL, et al.
Exosome-mediated microRNA signaling from breast cancer cells is altered by the anti-angiogenesis agent docosahexaenoic acid (DHA).
Mol Cancer. 2015; 14:133 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Docosahexaenoic acid (DHA) is a natural compound with anticancer and anti-angiogenesis activity that is currently under investigation as both a preventative agent and an adjuvant to breast cancer therapy. However, the precise mechanisms of DHA's anticancer activities are unclear. It is understood that the intercommunication between cancer cells and their microenvironment is essential to tumor angiogenesis. Exosomes are extracellular vesicles that are important mediators of intercellular communication and play a role in promoting angiogenesis. However, very little is known about the contribution of breast cancer exosomes to tumor angiogenesis or whether exosomes can mediate DHA's anticancer action.
RESULTS: Exosomes were collected from MCF7 and MDA-MB-231 breast cancer cells after treatment with DHA. We observed an increase in exosome secretion and exosome microRNA contents from the DHA-treated cells. The expression of 83 microRNAs in the MCF7 exosomes was altered by DHA (>2-fold). The most abundant exosome microRNAs (let-7a, miR-23b, miR-27a/b, miR-21, let-7, and miR-320b) are known to have anti-cancer and/or anti-angiogenic activity. These microRNAs were also increased by DHA treatment in the exosomes from other breast cancer lines (MDA-MB-231, ZR751 and BT20), but not in exosomes from normal breast cells (MCF10A). When DHA-treated MCF7 cells were co-cultured with or their exosomes were directly applied to endothelial cell cultures, we observed an increase in the expression of these microRNAs in the endothelial cells. Furthermore, overexpression of miR-23b and miR-320b in endothelial cells decreased the expression of their pro-angiogenic target genes (PLAU, AMOTL1, NRP1 and ETS2) and significantly inhibited tube formation by endothelial cells, suggesting that the microRNAs transferred by exosomes mediate DHA's anti-angiogenic action. These effects could be reversed by knockdown of the Rab GTPase, Rab27A, which controls exosome release.
CONCLUSIONS: We conclude that DHA alters breast cancer exosome secretion and microRNA contents, which leads to the inhibition of angiogenesis. Our data demonstrate that breast cancer exosome signaling can be targeted to inhibit tumor angiogenesis and provide new insight into DHA's anticancer action, further supporting its use in cancer therapy.

Kotake Y, Naemura M, Murasaki C, et al.
Transcriptional Regulation of the p16 Tumor Suppressor Gene.
Anticancer Res. 2015; 35(8):4397-401 [PubMed] Related Publications
The p16 tumor suppressor gene encodes a specific inhibitor of cyclin-dependent kinase (CDK) 4 and 6 and is found altered in a wide range of human cancers. p16 plays a pivotal role in tumor suppressor networks through inducing cellular senescence that acts as a barrier to cellular transformation by oncogenic signals. p16 protein is relatively stable and its expression is primary regulated by transcriptional control. Polycomb group (PcG) proteins associate with the p16 locus in a long non-coding RNA, ANRIL-dependent manner, leading to repression of p16 transcription. YB1, a transcription factor, also represses the p16 transcription through direct association with its promoter region. Conversely, the transcription factors Ets1/2 and histone H3K4 methyltransferase MLL1 directly bind to the p16 locus and mediate p16 induction during replicative and premature senescence. In the present review, we discuss the molecular mechanisms by which these factors regulate p16 transcription.

Mosrati MA, Malmström A, Lysiak M, et al.
TERT promoter mutations and polymorphisms as prognostic factors in primary glioblastoma.
Oncotarget. 2015; 6(18):16663-73 [PubMed] Free Access to Full Article Related Publications
Telomerase reverse transcriptase (TERT) activity is up-regulated in several types of tumors including glioblastoma (GBM). In the present study, 128 primary glioblastoma patients were examined for single nucleotide polymorphisms of TERT in blood and in 92 cases for TERT promoter mutations in tumors. TERT promoter mutations were observed in 86% of the tumors and of these, C228T (-124 bp upstream start codon) was detected in 75% and C250T (-146 bp) in 25% of cases. TERT promoter mutations were associated with shorter overall survival (11 vs. 20 months p = 0.002 and 12 vs. 20, p = 0.04 for C228T and C250T, respectively). The minor alleles of rs2736100 and rs10069690 SNP's, located in intron 2 and the promotor regions, respectively, were associated with an increased risk of developing GBM (p = 0.004 and 0.001). GBM patients having both TERT promoter mutations and being homozygous carriers of the rs2853669 C-allele displayed significantly shorter overall survival than those with the wild type allele. The rs2853669 SNP is located in a putative Ets2 binding site in the promoter (-246 bp upstream start codon) close to the C228T and C250T mutation hot spots. Interleukin-6 (IL-6) expression regulated by TERT promoter status and polymorphism, what leads us to think that TERT and IL-6 plays a significant role in GBM, where specific SNPs increase the risk of developing GBM while the rs2853669 SNP and specific mutations in the TERT promoter of the tumor lead to shorter survival.

Ding X, Zhou X, Jiang B, et al.
Triptolide suppresses proliferation, hypoxia-inducible factor-1α and c-Myc expression in pancreatic cancer cells.
Mol Med Rep. 2015; 12(3):4508-13 [PubMed] Related Publications
Triptolide (TL) is known to suppress the proliferation of a number of pancreatic cancer cell lines in vitro. Marked antitumor effects were also observed in a xenograft model of pancreatic cancer. Hypoxia‑inducible factor‑1α (HIF‑1α) is highly expressed in pancreatic cancer cells lines. The present study therefore tested the hypothesis that suppression of HIF‑1α is associated with the antitumor activity of TL. Quantitative polymerase chain reaction and western blot analysis were used to determine the level of gene expression. A xenograft tumor model of pancreatic cancer was established in athymic nude mice and the tumor size was measured to evaluate the outcome of TL treatment. Immunohistochemistry was used to detect the expression of HIF‑1α and vascular endothelial growth factor (VEGF), and to assess microvessel density. Microarray was used to investigate gene expression in pancreatic cancer cells following TL treatment. The expression of HIF‑1α was shown to be reduced in pancreatic cell lines following treatment with TL, and this effect occurred in a dose‑dependent manner. In a xenograft model of pancreatic cancer, reduced levels of HIF‑1α were also observed in mice that were treated with TL. Furthermore, the expression of VEGF, which is a direct target of HIF‑1α, was also suppressed, and the microvessel density of tumor tissues was consequently reduced. A microarray analysis of gene expression was performed in order to investigate the potential mechanisms underlying the antitumor activity of TL. The results showed that 11 genes, including c‑Myc, SOX9 and Ets2, were downregulated at an early stage following treatment with TL. A recent study indicated that overexpression of c‑Myc in colon cancer cells promotes increased expression of HIF‑1α and VEGF. Therefore, TL may suppress HIF‑1α through a c‑Myc‑dependent mechanism, which is involved in antitumor effects in mouse models of pancreatic cancer.

Shen XB, Huang L, Zhang SH, et al.
Transcriptional regulation of the apolipoprotein F (ApoF) gene by ETS and C/EBPα in hepatoma cells.
Biochimie. 2015; 112:1-9 [PubMed] Related Publications
Apolipoprotein F (ApoF) inhibits cholesteryl ester transfer protein (CETP) activity and plays an important role in lipid metabolism. In the present study, the full-length human ApoF promoter was cloned, and the molecular mechanism of the regulation of ApoF was investigated. The ApoF promoter displayed higher activities in hepatoma cell lines, and the -198 nt to +79 nt promoter region contained the maximum promoter activity. In the promoter region of -198 nt to -2 nt there were four putative binding sites for transcription factors ETS-1/ETS-2 (named EBS-1 to EBS-4) and one for C/EBP. Mutation of EBS-2, EBS4 and the C/EBP binding site abolished the promoter activity, and ETS-1/ETS-2 and C/EBPα could interact with corresponding binding sites. In addition, overexpression of ETS-1/2 or C/EBPα enhanced, while dominant-negative mutants of ETS-1/2 and knockdown of C/EBPα decreased, ApoF promoter activities. ETS-1 and C/EBPα associated physically, and acted synergistically to activate ApoF transcription. These results demonstrated combined activation of the ApoF promoter by liver-enriched and ubiquitous transcription factors. Direct interactions between C/EBPα and ETS-1 were important for high liver-specific expression of ApoF.

Spiegl-Kreinecker S, Lötsch D, Ghanim B, et al.
Prognostic quality of activating TERT promoter mutations in glioblastoma: interaction with the rs2853669 polymorphism and patient age at diagnosis.
Neuro Oncol. 2015; 17(9):1231-40 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Expression of the telomerase reverse transcriptase (TERT) might be altered by activating mutations of the rs2853669 polymorphism within the promoter region. Here we investigate the impact of these genomic alterations on telomerase activation and dissect their prognostic potential in glioblastoma (GBM).
METHODS: The respective TERT promoter region was sequenced in 126 GBM tissues and compared with clinical parameters and glioma biomarkers MGMT promoter methylation and IDH1 mutation. TERT mRNA expression, telomerase activity, and telomere lengths were determined by reverse transcriptase PCR, TRAP assay, and real-time PCR, respectively.
RESULTS: Seventy-three percent of GBM patients harbored TERT promoter mutations associated with enhanced telomerase activity and TERT mRNA expression but reduced telomere lengths (P < .001 for all). Patients with mutated tumors exhibited significantly shorter overall survival in the entire cohort (11.5 vs 23.1 months; P < .0001) and in the primary GBM patient subgroup lacking IDH1 mutations (n = 120; P = .0084). This prognostic impact was confined to younger patients (aged <65 years), while the negative prognostic power of enhanced age at diagnosis was limited to those patients lacking TERT promoter mutations. Presence of the common single nucleotide polymorphism rs2853669, disrupting an endogenous Ets2 transcription factor-binding site, was associated with improved survival exclusively in patients with a wild-type TERT promoter. On the contrary, the shortest mean overall survival was detected in those patients harboring both an activating TERT promoter mutation and homozygous rs2853669 alleles.
CONCLUSION: In summary, TERT promoter mutations are powerful prognosticators for worse course of disease in human GBM patients but their prognostic value is influenced by the rs2853669 polymorphism and age at diagnosis.

Mathsyaraja H, Thies K, Taffany DA, et al.
CSF1-ETS2-induced microRNA in myeloid cells promote metastatic tumor growth.
Oncogene. 2015; 34(28):3651-61 [PubMed] Free Access to Full Article Related Publications
Metastasis of solid tumors is associated with poor prognosis and bleak survival rates. Tumor-infiltrating myeloid cells (TIMs) are known to promote metastasis, but the mechanisms underlying their collaboration with tumor cells remain unknown. Here, we report an oncogenic role for microRNA (miR) in driving M2 reprogramming in TIMs, characterized by the acquisition of pro-tumor and pro-angiogenic properties. The expression of miR-21, miR-29a, miR-142-3p and miR-223 increased in myeloid cells during tumor progression in mouse models of breast cancer and melanoma metastasis. Further, we show that these miRs are regulated by the CSF1-ETS2 pathway in macrophages. A loss-of-function approach utilizing selective depletion of the miR-processing enzyme Dicer in mature myeloid cells blocks angiogenesis and metastatic tumor growth. Ectopic expression of miR-21 and miR-29a promotes angiogenesis and tumor cell proliferation through the downregulation of anti-angiogenic genes such as Col4a2, Spry1 and Timp3, whereas knockdown of the miRs impedes these processes. miR-21 and miR-29a are expressed in Csf1r+ myeloid cells associated with human metastatic breast cancer, and levels of these miRs in CD115+ non-classical monocytes correlates with metastatic tumor burden in patients. Taken together, our results suggest that miR-21 and miR-29a are essential for the pro-tumor functions of myeloid cells and the CSF1-ETS2 pathway upstream of the miRs serves as an attractive therapeutic target for the inhibition of M2 remodeling of macrophages during malignancy. In addition, miR-21 and miR-29a in circulating myeloid cells may potentially serve as biomarkers to measure therapeutic efficacy of targeted therapies for CSF1 signaling.

Xiong S, Tu H, Kollareddy M, et al.
Pla2g16 phospholipase mediates gain-of-function activities of mutant p53.
Proc Natl Acad Sci U S A. 2014; 111(30):11145-50 [PubMed] Free Access to Full Article Related Publications
p53(R172H/+) mice inherit a p53 mutation found in Li-Fraumeni syndrome and develop metastatic tumors at much higher frequency than p53(+/-) mice. To explore the mutant p53 metastatic phenotype, we used expression arrays to compare primary osteosarcomas from p53(R172H/+) mice with metastasis to osteosarcomas from p53(+/-) mice lacking metastasis. For this study, 213 genes were differentially expressed with a P value <0.05. Of particular interest, Pla2g16, which encodes a phospholipase that catalyzes phosphatidic acid into lysophosphatidic acid and free fatty acid (both implicated in metastasis), was increased in p53(R172H/+) osteosarcomas. Functional analyses showed that Pla2g16 knockdown decreased migration and invasion in mutant p53-expressing cells, and vice versa: overexpression of Pla2g16 increased the invasion of p53-null cells. Furthermore, Pla2g16 levels were increased upon expression of mutant p53 in both mouse and human osteosarcoma cell lines, indicating that Pla2g16 is a downstream target of the mutant p53 protein. ChIP analysis revealed that several mutant p53 proteins bind the Pla2g16 promoter at E26 transformation-specific (ETS) binding motifs and knockdown of ETS2 suppressed mutant p53 induction of Pla2g16. Thus, our study identifies a phospholipase as a transcriptional target of mutant p53 that is required for metastasis.

Kabbout M, Dakhlallah D, Sharma S, et al.
MicroRNA 17-92 cluster mediates ETS1 and ETS2-dependent RAS-oncogenic transformation.
PLoS One. 2014; 9(6):e100693 [PubMed] Free Access to Full Article Related Publications
The ETS-family transcription factors Ets1 and Ets2 are evolutionarily conserved effectors of the RAS/ERK signaling pathway, but their function in Ras cellular transformation and biology remains unclear. Taking advantage of Ets1 and Ets2 mouse models to generate Ets1/Ets2 double knockout mouse embryonic fibroblasts, we demonstrate that deletion of both Ets1 and Ets2 was necessary to inhibit HrasG12V induced transformation both in vitro and in vivo. HrasG12V expression in mouse embryonic fibroblasts increased ETS1 and ETS2 expression and binding to cis-regulatory elements on the c-Myc proximal promoter, and consequently induced a robust increase in MYC expression. The expression of the oncogenic microRNA 17-92 cluster was increased in HrasG12V transformed cells, but was significantly reduced when ETS1 and ETS2 were absent. MYC and ETS1 or ETS2 collaborated to increase expression of the oncogenic microRNA 17-92 cluster in HrasG12V transformed cells. Enforced expression of exogenous MYC or microRNA 17-92 rescued HrasG12V transformation in Ets1/Ets2-null cells, revealing a direct function for MYC and microRNA 17-92 in ETS1/ETS2-dependent HrasG12V transformation.

Fancy SP, Harrington EP, Baranzini SE, et al.
Parallel states of pathological Wnt signaling in neonatal brain injury and colon cancer.
Nat Neurosci. 2014; 17(4):506-12 [PubMed] Free Access to Full Article Related Publications
In colon cancer, mutation of the Wnt repressor APC (encoding adenomatous polyposis coli) leads to a state of aberrant and unrestricted high-activity signaling. However, the relevance of high Wnt tone in non-genetic human disease is unknown. Here we demonstrate that distinct functional states of Wnt activity determine oligodendrocyte precursor cell (OPC) differentiation and myelination. Mouse OPCs with genetic Wnt dysregulation (high tone) express multiple genes in common with colon cancer, including Lef1, Sp5, Ets2, Rnf43 and Dusp4. Surprisingly, we found that OPCs in lesions of hypoxic human neonatal white matter injury upregulated markers of high Wnt activity and lacked expression of APC. We also found that lack of Wnt repressor tone promoted permanent white matter injury after mild hypoxic insult. These findings suggest a state of pathological high-activity Wnt signaling in human disease tissues that lack predisposing genetic mutation.

Bilsland AE, Stevenson K, Liu Y, et al.
Mathematical model of a telomerase transcriptional regulatory network developed by cell-based screening: analysis of inhibitor effects and telomerase expression mechanisms.
PLoS Comput Biol. 2014; 10(2):e1003448 [PubMed] Free Access to Full Article Related Publications
Cancer cells depend on transcription of telomerase reverse transcriptase (TERT). Many transcription factors affect TERT, though regulation occurs in context of a broader network. Network effects on telomerase regulation have not been investigated, though deeper understanding of TERT transcription requires a systems view. However, control over individual interactions in complex networks is not easily achievable. Mathematical modelling provides an attractive approach for analysis of complex systems and some models may prove useful in systems pharmacology approaches to drug discovery. In this report, we used transfection screening to test interactions among 14 TERT regulatory transcription factors and their respective promoters in ovarian cancer cells. The results were used to generate a network model of TERT transcription and to implement a dynamic Boolean model whose steady states were analysed. Modelled effects of signal transduction inhibitors successfully predicted TERT repression by Src-family inhibitor SU6656 and lack of repression by ERK inhibitor FR180204, results confirmed by RT-QPCR analysis of endogenous TERT expression in treated cells. Modelled effects of GSK3 inhibitor 6-bromoindirubin-3'-oxime (BIO) predicted unstable TERT repression dependent on noise and expression of JUN, corresponding with observations from a previous study. MYC expression is critical in TERT activation in the model, consistent with its well known function in endogenous TERT regulation. Loss of MYC caused complete TERT suppression in our model, substantially rescued only by co-suppression of AR. Interestingly expression was easily rescued under modelled Ets-factor gain of function, as occurs in TERT promoter mutation. RNAi targeting AR, JUN, MXD1, SP3, or TP53, showed that AR suppression does rescue endogenous TERT expression following MYC knockdown in these cells and SP3 or TP53 siRNA also cause partial recovery. The model therefore successfully predicted several aspects of TERT regulation including previously unknown mechanisms. An extrapolation suggests that a dominant stimulatory system may programme TERT for transcriptional stability.

Rachakonda PS, Hosen I, de Verdier PJ, et al.
TERT promoter mutations in bladder cancer affect patient survival and disease recurrence through modification by a common polymorphism.
Proc Natl Acad Sci U S A. 2013; 110(43):17426-31 [PubMed] Free Access to Full Article Related Publications
The telomerase reverse transcriptase (TERT) promoter, an important element of telomerase expression, has emerged as a target of cancer-specific mutations. Originally described in melanoma, the mutations in TERT promoter have been shown to be common in certain other tumor types that include glioblastoma, hepatocellular carcinoma, and bladder cancer. To fully define the occurrence and effect of the TERT promoter mutations, we investigated tumors from a well-characterized series of 327 patients with urothelial cell carcinoma of bladder. The somatic mutations, mainly at positions -124 and -146 bp from ATG start site that create binding motifs for E-twenty six/ternary complex factors (Ets/TCF), affected 65.4% of the tumors, with even distribution across different stages and grades. Our data showed that a common polymorphism rs2853669, within a preexisting Ets2 binding site in the TERT promoter, acts as a modifier of the effect of the mutations on survival and tumor recurrence. The patients with the mutations showed poor survival in the absence [hazard ratio (HR) 2.19, 95% confidence interval (CI) 1.02-4.70] but not in the presence (HR 0.42, 95% CI 0.18-1.01) of the variant allele of the polymorphism. The mutations in the absence of the variant allele were highly associated with the disease recurrence in patients with Tis, Ta, and T1 tumors (HR 1.85, 95% CI 1.11-3.08). The TERT promoter mutations are the most common somatic lesions in bladder cancer with clinical implications. The association of the mutations with patient survival and disease recurrence, subject to modification by a common polymorphism, can be a unique putative marker with individualized prognostic potential.

Wallace JA, Li F, Balakrishnan S, et al.
Ets2 in tumor fibroblasts promotes angiogenesis in breast cancer.
PLoS One. 2013; 8(8):e71533 [PubMed] Free Access to Full Article Related Publications
Tumor fibroblasts are active partners in tumor progression, but the genes and pathways that mediate this collaboration are ill-defined. Previous work demonstrates that Ets2 function in stromal cells significantly contributes to breast tumor progression. Conditional mouse models were used to study the function of Ets2 in both mammary stromal fibroblasts and epithelial cells. Conditional inactivation of Ets2 in stromal fibroblasts in PyMT and ErbB2 driven tumors significantly reduced tumor growth, however deletion of Ets2 in epithelial cells in the PyMT model had no significant effect. Analysis of gene expression in fibroblasts revealed a tumor- and Ets2-dependent gene signature that was enriched in genes important for ECM remodeling, cell migration, and angiogenesis in both PyMT and ErbB2 driven-tumors. Consistent with these results, PyMT and ErbB2 tumors lacking Ets2 in fibroblasts had fewer functional blood vessels, and Ets2 in fibroblasts elicited changes in gene expression in tumor endothelial cells consistent with this phenotype. An in vivo angiogenesis assay revealed the ability of Ets2 in fibroblasts to promote blood vessel formation in the absence of tumor cells. Importantly, the Ets2-dependent gene expression signatures from both mouse models were able to distinguish human breast tumor stroma from normal stroma, and correlated with patient outcomes in two whole tumor breast cancer data sets. The data reveals a key function for Ets2 in tumor fibroblasts in signaling to endothelial cells to promote tumor angiogenesis. The results highlight the collaborative networks that orchestrate communication between stromal cells and tumor cells, and suggest that targeting tumor fibroblasts may be an effective strategy for developing novel anti-angiogenic therapies.

Takeda S, Liu H, Sasagawa S, et al.
HGF-MET signals via the MLL-ETS2 complex in hepatocellular carcinoma.
J Clin Invest. 2013; 123(7):3154-65 [PubMed] Free Access to Full Article Related Publications
HGF signals through its cognate receptor, MET, to orchestrate diverse biological processes, including cell proliferation, cell fate specification, organogenesis, and epithelial-mesenchymal transition. Mixed-lineage leukemia (MLL), an epigenetic regulator, plays critical roles in cell fate, stem cell, and cell cycle decisions. Here, we describe a role for MLL in the HGF-MET signaling pathway. We found a shared phenotype among Mll(-/-), Hgf(-/-), and Met(-/-) mice with common cranial nerve XII (CNXII) outgrowth and myoblast migration defects. Phenotypic analysis demonstrated that MLL was required for HGF-induced invasion and metastatic growth of hepatocellular carcinoma cell lines. HGF-MET signaling resulted in the accumulation of ETS2, which interacted with MLL to transactivate MMP1 and MMP3. ChIP assays demonstrated that activation of the HGF-MET pathway resulted in increased occupancy of the MLL-ETS2 complex on MMP1 and MMP3 promoters, where MLL trimethylated histone H3 lysine 4 (H3K4), activating transcription. Our results present an epigenetic link between MLL and the HGF-MET signaling pathway, which may suggest new strategies for therapeutic intervention.

Marquardt JU, Thorgeirsson SS
Linking MLL and the HGF-MET signaling pathway in liver cancer.
J Clin Invest. 2013; 123(7):2780-3 [PubMed] Free Access to Full Article Related Publications
Mixed-lineage leukemia (MLL; also known as myeloid/lymphoid), the human homolog of trithorax in Drosophila, is a transcriptional coactivator that plays an essential role during early development and hematopoiesis. Furthermore, MLL is critically involved in the epigenetic regulation of cell cycle, senescence, DNA damage, and stem cell self-renewal. Chromosomal aberrations of MLL in acute leukemias are well documented, but the role of this gene in solid malignancies remains unclear. In this issue of the JCI, Takeda et al. describe a novel epigenetic link between MLL and the HGF-MET signaling pathway conferring invasive and metastatic properties to hepatocellular carcinoma cells.

Kabbout M, Garcia MM, Fujimoto J, et al.
ETS2 mediated tumor suppressive function and MET oncogene inhibition in human non-small cell lung cancer.
Clin Cancer Res. 2013; 19(13):3383-95 [PubMed] Free Access to Full Article Related Publications
PURPOSE: The ETS2 transcription factor is an evolutionarily conserved gene that is deregulated in cancer. We analyzed the transcriptome of lung adenocarcinomas and normal lung tissue by expression profiling and found that ETS2 was significantly downregulated in adenocarcinomas. In this study, we probed the yet unknown functional role of ETS2 in lung cancer pathogenesis.
EXPERIMENTAL DESIGN: Lung adenocarcinomas (n = 80) and normal lung tissues (n = 30) were profiled using the Affymetrix Human Gene 1.0 ST platform. Immunohistochemical (IHC) analysis was conducted to determine ETS2 protein expression in non-small cell lung cancer (NSCLC) histologic tissue specimens (n = 201). Patient clinical outcome, based on ETS2 IHC expression, was statistically assessed using the log-rank and Kaplan-Meier tests. RNA interference and overexpression strategies were used to assess the effects of ETS2 expression on the transcriptome and on various malignant phenotypes.
RESULTS: ETS2 expression was significantly reduced in lung adenocarcinomas compared with normal lung (P < 0.001). Low ETS2 IHC expression was a significant predictor of shorter time to recurrence in NSCLC (P = 0.009, HR = 1.89) and adenocarcinoma (P = 0.03, HR = 1.86). Moreover, ETS2 was found to significantly inhibit lung cancer cell growth, migration, and invasion (P < 0.05), and microarray and pathways analysis revealed significant (P < 0.001) activation of the HGF pathway following ETS2 knockdown. In addition, ETS2 was found to suppress MET phosphorylation and knockdown of MET expression significantly attenuated (P < 0.05) cell invasion mediated by ETS2-specific siRNA. Furthermore, knockdown of ETS2 augmented HGF-induced MET phosphorylation, cell migration, and invasion.
CONCLUSION(S): Our findings point to a tumor suppressor role for ETS2 in human NSCLC pathogenesis through inhibition of the MET proto-oncogene.

Gai X, Zhao P, Pan Y, et al.
Hepatitis B virus core protein enhances human telomerase reverse transcriptase expression and hepatocellular carcinoma cell proliferation in a c-Ets2-dependent manner.
Int J Biochem Cell Biol. 2013; 45(7):1174-85 [PubMed] Related Publications
Hepatitis B virus core protein can regulate viral replication and host gene expression. However, it is unclear whether and how hepatitis B virus core protein regulates hepatocellular carcinoma cell proliferation. Induction of hepatitis B virus core protein over-expression significantly enhanced the proliferation of hepatocellular carcinoma cells, while knockdown of hepatitis B virus core protein expression inhibited the proliferation of hepatocellular carcinoma cells. Altered hepatitis B virus core protein expression significantly changed the growth of implanted hepatocellular carcinoma in vivo. Microarray analysis indicated that hepatitis B virus core protein up-regulated human telomerase reverse transcriptase expression, which was further validated by over-expression and knockdown assays in vitro. Furthermore, knockdown of human telomerase reverse transcriptase expression mitigated the hepatitis B virus core protein-enhanced hepatocellular carcinoma cell proliferation and clone formation in vitro. Luciferase assays indicated that hepatitis B virus core protein enhanced the promoter activity of human telomerase reverse transcriptase, which was dependent on the binding of c-Ets2 to the promoter region between -192 and -187. In addition, hepatitis B virus core protein enhanced human telomerase reverse transcriptase transcription in HepG2 cells, but not in the c-Ets2-silencing HepG2 cells. Moreover, hepatitis B virus core protein promoted c-Ets2 nuclear translocation. Finally, significantly higher levels of human telomerase reverse transcriptase expression and nuclear c-Ets2 accumulation were detected in hepatitis B virus core protein-positive hepatocellular carcinoma samples. Our findings demonstrate that hepatitis B virus core protein promotes hepatocellular carcinoma cell proliferation by up-regulating the c-Ets2-dependent expression of human telomerase reverse transcriptase.

Zhu X, Zhang J, Fan W, et al.
The rs391957 variant cis-regulating oncogene GRP78 expression contributes to the risk of hepatocellular carcinoma.
Carcinogenesis. 2013; 34(6):1273-80 [PubMed] Related Publications
Glucose-regulated protein 78 (GRP78) is one of the most important responders to disease-related stress. We assessed the association of the promoter polymorphisms of GRP78 with risk of hepatocellular carcinoma (HCC) and GRP78 expression in a Chinese population. We examined 1007 patients undergoing diagnostic HCC and 810 unrelated healthy controls. Mechanisms by which the GRP78 promoter polymorphism modulates HCC risk and GRP78 levels were analyzed. The promoter haplotype and diplotype carrying rs391957 (-415bp) allele G and genotype GG was strongly associated with HCC risk. Luciferase reporter assays indicated that the promoter carrying rs391957 allele G (haplotype GCCd) showed increased activity in HepG2 cells and Hela cells. rs391957 was also shown to increase the affinity of the transcriptional activator Ets-2, the resistance to apoptosis, as well as cell instability in stressful microenvironment. Furthermore, compared with allele A, rs391957 allele G was associated with higher levels of GRP78 mRNA and protein in HCC tissues. These findings provided new insights into the pathogenesis of HCC and an unexpected effect of the interaction between rs391957 and Ets-2 on hepatocarcinogenesis, and especially supported the hypothesis that stress-related and evolutionarily conserved genetic variant(s) influencing transcriptional regulation could predict susceptibilities.

Chatterjee A, Dutta S, Mukherjee S, et al.
Potential contribution of SIM2 and ETS2 functional polymorphisms in Down syndrome associated malignancies.
BMC Med Genet. 2013; 14:12 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Proper expression and functioning of transcription factors (TFs) are essential for regulation of different traits and thus could be crucial for the development of complex diseases. Subjects with Down syndrome (DS) have a higher incidence of acute lymphoblastic leukemia (ALL) while solid tumors, like breast cancer (BC) and oral cancer (OC), show rare incidences. Triplication of the human chromosome 21 in DS is associated with altered genetic dosage of different TFs. V-ets erythroblastosis virus E26 oncogene homolog 2 (ETS2) and Single Minded 2 (SIM2) are two such TFs that regulate several downstream genes involved in developmental and neurological pathways. Here we studied functional genetic polymorphisms (fSNP) in ETS2 and SIM2 encoding genes in a group of patients and control subjects to better understand association of these variants with DS phenotypes.
METHODS: We employed an in silico approach to identify potential target pathways of ETS2 and SIM2. fSNPs in genes encoding for these two TFs were identified using available databases. Selected sites were genotyped in individuals with DS, their parents, ALL, BC, OC as well as ethnically matched control individuals. We further analyzed these data by population-based statistical methods.
RESULTS: Allelic/genotypic association analysis showed significant (P < 0.03) differences of rs2070530, rs1051476, rs11254, rs711 for DS subjects compared to control. rs711 also exhibited significantly different genotypic distribution pattern in parents of DS probands (P < 0.02) and BC patients (P < 0.02). Interaction analysis revealed independent main effect of rs711 in all the groups, while rs11254 exhibited independent main effect in DS subjects only. High entropy values were noticed for rs461155 in the solid tumor groups. Significant interactive effects of rs2070531 with rs1051475, rs1051476, rs11254 were observed in all the groups except DS.
CONCLUSIONS: We infer from the present investigation that the difference in frequencies of fSNPs and their independent as well as interactive effects may be the cause for altered expression of SIM2 and ETS2 in DS and malignant groups, which affects different downstream biological pathways. Thus, altered expression of SIM2 and ETS2 could be one of the reasons for variable occurrence of different malignant conditions in DS.

Rueda N, Flórez J, Martínez-Cué C
Apoptosis in Down's syndrome: lessons from studies of human and mouse models.
Apoptosis. 2013; 18(2):121-34 [PubMed] Related Publications
Down syndrome (DS) is the most common chromosomal abnormality in humans. DS is characterized by a number of phenotypes, including the development of Alzheimer's disease-like pathology and immunological, hematological and cardiovascular alterations. Apoptosis or programmed cell death is physiologically involved in development and aging, as well as in numerous pathological processes. Altered apoptosis has been proposed as a putative mechanism underlying many DS phenotypes. Evidence from human and animal studies indicates that apoptosis does not have a prominent role in the disturbances found in brain development in trisomy 21. However, alterations in apoptosis have been associated with neurodegeneration in the aging DS brain, with impairments in general growth and with immunological, cardiovascular and oncological alterations. Altered apoptosis in DS is likely to be the result of the interplay between several chromosome 21 (Hsa21) and non-Hsa21 genes. The interplay between these genes may affect physiological programmed cell death either directly, by modifying the activity of the apoptotic pathways, or indirectly, by inducing degeneration and rendering the cell more vulnerable to apoptosis-inducing factors.

Kaushal M, Mishra AK, Sharma J, et al.
Genomic alterations in breast cancer patients in betel quid and non betel quid chewers.
PLoS One. 2012; 7(8):e43789 [PubMed] Free Access to Full Article Related Publications
Betel Quid (BQ) chewing independently contributes to oral, hepatic and esophageal carcinomas. Strong association of breast cancer risk with BQ chewing in Northeast Indian population has been reported where this habit is prodigal. We investigated genomic alterations in breast cancer patients with and without BQ chewing exposure. Twenty six BQ chewers (BQC) and 17 non BQ chewer (NBQC) breast cancer patients from Northeast India were analyzed for genomic alterations and pathway networks using SNP array and IPA. BQC tumors showed significantly (P<0.01) higher total number of alterations, as compared with NBQC tumors, 48 ± 17% versus 32 ± 25 respectively. Incidence of gain in fragile sites in BQC tumors were significantly (P<0.001) higher as compared with NBQC tumors, 34 versus 23% respectively. Two chromosomal regions (7q33 and 21q22.13) were significantly (p<0.05) associated with BQC tumors while two regions (19p13.3-19p12 and 20q11.22) were significantly associated with NBQC tumors. GO terms oxidoreductase and aldo-keto reductase activity in BQC tumors in contrast to G-protein coupled receptor protein signaling pathway and cell surface receptor linked signal transduction in NBQC tumors were enriched in DAVID. One network "Drug Metabolism, Molecular Transport, Nucleic Acid Metabolism" including genes AKR1B1, AKR1B10, ETS2 etc in BQC and two networks "Molecular Transport, Nucleic Acid Metabolism, Small Molecule Biochemistry" and "Cellular Development, Embryonic Development, Organismal Development" including genes RPN2, EMR3, VAV1, NNAT and MUC16 etc were seen in NBQC. Common alterations (>30%) were seen in 27 regions. Three networks were significant in common regions with key roles of PTK2, RPN2, EMR3, VAV1, NNAT, MUC16, MYC and YWHAZ genes. These data show that breast cancer arising by environmental carcinogens exemplifies genetic alterations differing from those observed in the non exposed ones. A number of genetic changes are shared in both tumor groups considered as crucial in breast cancer progression.

Shaikhibrahim Z, Ochsenfahrt J, Fuchs K, et al.
ERG is specifically associated with ETS-2 and ETV-4, but not with ETS-1, in prostate cancer.
Int J Mol Med. 2012; 30(5):1029-33 [PubMed] Free Access to Full Article Related Publications
The erythroblast transformation-specific (ETS) family of transcription factors plays important roles in both physiological and pathological conditions. Even though many studies have focused on single ETS factors within a single tissue and within the context of specific promoters, the functional impact of multiple ETS members present within a specific cell type has not yet been investigated, especially in prostate cancer (PCa). As the most prominent gene rearrangement in PCa leads to the overexpression of the ETS-related gene (ERG), the aim of this study was to investigate whether ERG is part of a complex integrated transcriptional network that involves other ETS factors. More specifically, as the ETS family consists of 27 members, we focused our efforts initially on investigating whether ERG is associated with the three family members, ETS-1, ETS-2 and ETS variant gene‑4 (ETV‑4), in PCa as a proof of principle. Using western blot analysis, we show that ERG, ETS-1, ETS-2 and ETV-4 are expressed in PC3 cell nuclear extracts and in protein lysates prepared from human PCa prostatectomy specimens. Immunoprecipitations using an anti-ERG antibody were used with PC3 cell nuclear extracts as well as with a pooled protein lysate sample prepared from the PCa tissue samples of five patients. Importantly, our results revealed that ERG is specifically associated with ETS-2 and ETV-4, but not with ETS-1, in PC3 cell nuclear extracts and PCa tissue protein lysates. Our findings strongly support the notion that ERG is part of a complex integrated transcriptional network that involves other ETS factors, which are likely to cooperate or influence the activity of ERG in PCa. The functional impact of multiple ETS factors being associated with ERG in PCa requires further study, as it may provide insights into the mechanism by which ERG exerts its influence in PCa and may subsequently contribute to our understanding of the molecular basis of PCa.

Grasso CS, Wu YM, Robinson DR, et al.
The mutational landscape of lethal castration-resistant prostate cancer.
Nature. 2012; 487(7406):239-43 [PubMed] Free Access to Full Article Related Publications
Characterization of the prostate cancer transcriptome and genome has identified chromosomal rearrangements and copy number gains and losses, including ETS gene family fusions, PTEN loss and androgen receptor (AR) amplification, which drive prostate cancer development and progression to lethal, metastatic castration-resistant prostate cancer (CRPC). However, less is known about the role of mutations. Here we sequenced the exomes of 50 lethal, heavily pre-treated metastatic CRPCs obtained at rapid autopsy (including three different foci from the same patient) and 11 treatment-naive, high-grade localized prostate cancers. We identified low overall mutation rates even in heavily treated CRPCs (2.00 per megabase) and confirmed the monoclonal origin of lethal CRPC. Integrating exome copy number analysis identified disruptions of CHD1 that define a subtype of ETS gene family fusion-negative prostate cancer. Similarly, we demonstrate that ETS2, which is deleted in approximately one-third of CRPCs (commonly through TMPRSS2:ERG fusions), is also deregulated through mutation. Furthermore, we identified recurrent mutations in multiple chromatin- and histone-modifying genes, including MLL2 (mutated in 8.6% of prostate cancers), and demonstrate interaction of the MLL complex with the AR, which is required for AR-mediated signalling. We also identified novel recurrent mutations in the AR collaborating factor FOXA1, which is mutated in 5 of 147 (3.4%) prostate cancers (both untreated localized prostate cancer and CRPC), and showed that mutated FOXA1 represses androgen signalling and increases tumour growth. Proteins that physically interact with the AR, such as the ERG gene fusion product, FOXA1, MLL2, UTX (also known as KDM6A) and ASXL1 were found to be mutated in CRPC. In summary, we describe the mutational landscape of a heavily treated metastatic cancer, identify novel mechanisms of AR signalling deregulated in prostate cancer, and prioritize candidates for future study.

Piazza R, Pirola A, Spinelli R, et al.
FusionAnalyser: a new graphical, event-driven tool for fusion rearrangements discovery.
Nucleic Acids Res. 2012; 40(16):e123 [PubMed] Free Access to Full Article Related Publications
Gene fusions are common driver events in leukaemias and solid tumours; here we present FusionAnalyser, a tool dedicated to the identification of driver fusion rearrangements in human cancer through the analysis of paired-end high-throughput transcriptome sequencing data. We initially tested FusionAnalyser by using a set of in silico randomly generated sequencing data from 20 known human translocations occurring in cancer and subsequently using transcriptome data from three chronic and three acute myeloid leukaemia samples. in all the cases our tool was invariably able to detect the presence of the correct driver fusion event(s) with high specificity. In one of the acute myeloid leukaemia samples, FusionAnalyser identified a novel, cryptic, in-frame ETS2-ERG fusion. A fully event-driven graphical interface and a flexible filtering system allow complex analyses to be run in the absence of any a priori programming or scripting knowledge. Therefore, we propose FusionAnalyser as an efficient and robust graphical tool for the identification of functional rearrangements in the context of high-throughput transcriptome sequencing data.

Do PM, Varanasi L, Fan S, et al.
Mutant p53 cooperates with ETS2 to promote etoposide resistance.
Genes Dev. 2012; 26(8):830-45 [PubMed] Free Access to Full Article Related Publications
Mutant p53 (mtp53) promotes chemotherapy resistance through multiple mechanisms, including disabling proapoptotic proteins and regulating gene expression. Comparison of genome wide analysis of mtp53 binding revealed that the ETS-binding site motif (EBS) is prevalent within predicted mtp53-binding sites. We demonstrate that mtp53 regulates gene expression through EBS in promoters and that ETS2 mediates the interaction with this motif. Importantly, we identified TDP2, a 5'-tyrosyl DNA phosphodiesterase involved in the repair of DNA damage caused by etoposide, as a transcriptional target of mtp53. We demonstrate that suppression of TDP2 sensitizes mtp53-expressing cells to etoposide and that mtp53 and TDP2 are frequently overexpressed in human lung cancer; thus, our analysis identifies a potentially "druggable" component of mtp53's gain-of-function activity.

Gupta R, Ezashi T, Roberts RM
Squelching of ETS2 transactivation by POU5F1 silences the human chorionic gonadotropin CGA subunit gene in human choriocarcinoma and embryonic stem cells.
Mol Endocrinol. 2012; 26(5):859-72 [PubMed] Free Access to Full Article Related Publications
The subunit genes encoding human chorionic gonadotropin, CGA, and CGB, are up-regulated in human trophoblast. However, they are effectively silenced in choriocarcinoma cells by ectopically expressed POU domain class 5 transcription factor 1 (POU5F1). Here we show that POU5F1 represses activity of the CGA promoter through its interactions with ETS2, a transcription factor required for both placental development and human chorionic gonadotropin subunit gene expression, by forming a complex that precludes ETS2 from interacting with the CGA promoter. Mutation of a POU5F1 binding site proximal to the ETS2 binding site does not alter the ability of POU5F1 to act as a repressor but causes a drop in basal promoter activity due to overlap with the binding site for DLX3. DLX3 has only a modest ability to raise basal CGA promoter activity, but its coexpression with ETS2 can up-regulate it 100-fold or more. The two factors form a complex, and both must bind to the promoter for the combination to be transcriptionally effective, a synergy compromised by POU5F1. Similarly, in human embryonic stem cells, which express ETS2 but not CGA, ETS2 does not occupy its binding site on the CGA promoter but is found instead as a soluble complex with POU5F1. When human embryonic stem cells differentiate in response to bone morphogenetic protein-4 and concentrations of POU5F1 fall and hCG and DLX3 rise, ETS2 then occupies its binding site on the CGA promoter. Hence, a squelching mechanism underpins the transcriptional silencing of CGA by POU5F1 and could have general relevance to how pluripotency is maintained and how the trophoblast lineage emerges from pluripotent precursor cells.

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