Localization of the c-ets-2 transactivation domain

Whole Genome Sequencing of a Vietnamese Family from a Dioxin Contamination Hotspot Reveals Novel Variants in the Son with Undiagnosed Intellectual Disability

Although it has been a half-century since dioxin-contaminated herbicides were used to defoliate the landscape during the Vietnam War, dioxin contamination “hotspots” still remain in Vietnam. Environmental and health impacts of these hotspots need to be evaluated. Intellectual disability (ID) is one of the diseases found in the children of people exposed to the herbicides. This study aims to identify genetic alterations of a patient whose family lived in a dioxin hotspot. The patient’s father had a highly elevated dioxin concentration. He was affected with undiagnosed moderate ID. To analyze de novo mutations and genetic variations, and to identify causal gene(s) for ID, we performed whole genome sequencing (WGS) of the proband and his parents. Two de novo missense mutations were detected, each one in ETS2 and ZNF408 genes, respectively. Compound heterozygosity was identified in CENPF and TTN genes. Existing knowledge on the genes and bioinformatics analyses suggest that EST2, ZNF408, and CENPF might be promising candidates for ID causative genes.

Ets-1 promoter-associated noncoding RNA regulates the NONO/ERG/Ets-1 axis to drive gastric cancer progression

Emerging studies have indicated the essential functions of long noncoding RNAs (lncRNAs) during cancer progression. However, whether lncRNAs contribute to the upregulation of v-ets erythroblastosis virus E26 oncogene homolog 1 (Ets-1), an established oncogenic protein facilitating tumor invasion and metastasis, in gastric cancer remains elusive. Herein, we identified Ets-1 promoter-associated noncoding RNA (pancEts-1) as a novel lncRNA associated with the gastric cancer progression via mining of publicly available datasets and rapid amplification of cDNA ends. RNA pull-down, RNA immunoprecipitation, in vitro binding, and RNA electrophoretic mobility shift assays indicated the binding of pancEts-1 to non-POU domain containing octamer binding (NONO) protein. Mechanistically, pancEts-1 facilitated the physical interaction between NONO and Ets related gene (ERG), resulting in increased ERG transactivation and transcription of Ets-1 associated with gastric cancer progression. In addition, pancEts-1 facilitated the growth and aggressiveness of gastric cancer cells via interacting with NONO. In gastric cancer tissues, pancEts-1, NONO, and ERG were upregulated and significantly correlated with Ets-1 levels. High levels of pancEts-1, NONO, ERG, or Ets-1 were respectively associated with poor survival of gastric cancer patients, whereas simultaneous expression of all of them (HR = 3.012, P = 0.105) was not an independent prognostic factor for predicting clinical outcome. Overall, these results demonstrate that lncRNA pancEts-1 exhibits oncogenic properties that drive the progression of gastric cancer via regulating the NONO/ERG/Ets-1 axis.

Ets2 is not required for Ras or Neu/ErbB-2 mediated cellular transformation in vitro

Ets2 is a widely expressed Ets family transcription factor which is activated by Ras signaling and has been reported to transform fibroblasts. Expression of a dominant inhibitory Ets2 construct consisting of just the Ets2 DNA binding domain (Ets2DBD), reverses Ras transformation of NIH3T3 cells and the transformed characteristics of several human tumor cells. However, the Ets2DBD may interfere with multiple Ets family members. We have now utilized cell lines with a disrupted ets2 gene to determine whether Ets2 is required to mediate oncogenic signaling. Expression of the Ets2DBD in an Ets2-deficient cell line dramatically inhibited Ets-dependent (but not AP-1-dependent) reporter gene expression, revealing that the Ets2DBD does inhibit additional Ets family members. The transformation efficiency of Ets2-deficient cell lines by oncogenic Ras or Neu/ErbB-2 was similar to that of control cells in several in vitro assays, and was not enhanced by re-expression of Ets2. Finally, overexpression of Ets2 was not sufficient to induce focus formation in NIH3T3 cells, nor to enhance transformation by oncogenic Ras. Thus, Ets2 is not an essential mediator of Ras or Neu/ErbB-2 transformation in these cells. Our results illustrate the importance of utilizing specific approaches for analyzing the function of individual members of large gene families.

Protein kinase A and protein kinase C signaling pathway interaction in phenylethanolamine N-methyltransferase gene regulation

The protein kinase A (PKA) and protein kinase C (PKC) signaling pathways appear to interact in regulating phenylethanolamine N-methyltransferase (PNMT) promoter-driven gene transcription in PC12 cells. Forskolin treatment of cells transfected with the rat PNMT promoter-luciferase reporter gene construct pGL3RP893 increased promoter activity approximately two-fold whereas phorbol-12-myristate-13 acetate (PMA) treatment had no effect. However, simultaneous forskolin and PMA treatment synergistically activated the PNMT promoter approximately four-fold, suggesting that PKC stimulation requires prior induction of the PKA pathway. Consistent with this possibility the adenylate cyclase inhibitor MDL12,330A, and the PKA inhibitor H-89 prevented PNMT promoter stimulation by the combination of forskolin and PMA. PKA and PKC regulation seems to be mediated in part by Egr-1 and Sp1 through their consensus elements in the PNMT promoter. Forskolin and PMA treatment of PC12 cells increased Egr-1 protein and phosphorylated Egr-1/DNA-binding complex formation to the same extent but only increased phosphorylated Sp1/DNA binding complex formation without altering Sp1 protein levels. Mutation of the - 165 bp Egr-1 and - 48 bp Sp1 sites, respectively, attenuated and abolished combined forskolin and PMA-mediated promoter activation. PNMT promoter analysis further showed that synergistic stimulation by PKA and PKC involves DNA sequences between - 442 and - 392 bp, and potentially a GCM binding element lying within this region.

Characterization of monoclonal antibodies specific to the transcription factor ETS-2 protein

ETS-2 is a member of the ETS family of transcription factors. ETS-2 was initially characterized as a nuclear oncogene and has been shown to play a role in regulation of apoptosis and cell cycle progression. Members of the ETS family display high sequence homology, thus, there is considerable controversy concerning the specificity of existing ETS-2 polyclonal antibodies that have been used to define ETS-2 function. We therefore embarked on the production of ETS-2 specific monoclonal antibodies. In this report, we describe the production and characterization of six antibodies and the localization of their target epitopes to distinct domains of the ETS-2 protein. Four antibodies are ETS-2 specific and two antibodies cross-react with ETS-1, an ETS family member with the highest amino acid sequence homology to ETS-2. This report provides a comprehensive evaluation of ETS-2 specific monoclonal antibodies verified using ETS-2 null cells. These antibodies can be used for EMSA, Western blotting, immunoprecipitation and immunofluorescence staining experiments. Collectively, these reagents are invaluable molecular tools that should help better understand the biological function of ETS-2.

Functional dissection of the ETS transcription factor MEF

We previously indicated that myeloid elf-1-like factor (MEF) but not elf-1, specifically activated lysozyme gene expression in epithelial cells. MEF is highly homologous at the nucleotide and amino acid level, with elf-1 especially in the ETS domain. Here, we report the functional analysis of the nuclear localization and transactivation properties of MEF. To investigate the intracellular localization of MEF, we transiently transfected MEF-green fluorescence protein (GFP) fusion protein expression vector into HeLa cells. A region spanning residues 177-291 is required for nuclear localization. We produced deletion mutants of MEF to determine the transactivation domain. The data showed that the N-terminal region, encompassing amino acids 1-52 is a potent transactivation domain. The C-terminal region spanning residues 477-663 can also mediate transactivation but not as strongly as the N-terminal region. The activity of the amino acid residues 1-52 was confirmed by experiments with fused constructs of MEF to the DNA binding-domain of the yeast GAL4 protein. These results, which determined the localization of the functional domains of MEF, will provide us with new clues to its transactivation mechanisms to regulate lysozyme gene expression in epithelial cells.

Repression of Ets-2-induced transactivation of the tau interferon promoter by Oct-4

Oct-4 is a POU family transcription factor associated with potentially totipotent cells. Genes expressed in the trophectoderm but not in embryos prior to blastocyst formation may be targets for silencing by Oct-4. Here, we have tested this hypothesis with the tau interferon genes (IFNT genes), which are expressed exclusively in the trophectoderm of bovine embryos. IFNT promoters contain an Ets-2 enhancer, located at -79 to -70, and are up-regulated about 20-fold by the overexpression of Ets-2 in human JAr choriocarcinoma cells, which are permissive for IFNT expression. This enhancement was reversed in a dose-dependent manner by coexpression of Oct-4 but not either Oct-1 or Oct-2. When cells were transfected with truncated bovine IFNT promoters designed to eliminate potential octamer sites sequentially, luciferase reporter expression from each construct was still silenced by Oct-4. Full repression required both the N-terminal and POU domains of Oct-4, but neither domain used alone was an effective silencer. Oct-4 and Ets-2 formed a complex in vitro in the absence of DNA through binding of the POU domain of Oct-4 to a site located between the "pointed" and DNA binding domains of Ets-2. The two transcription factors were also coimmunoprecipitated after being expressed together in JAr cells. Oct-4, therefore, silences IFNT promoters by quenching Ets-2 transactivation. The POU domain most probably binds to Ets-2 directly, while the N-terminal domain inhibits transcription. These findings provide further evidence that the developmental switch to the trophectoderm is accompanied by the loss of Oct-4 silencing of key genes.

Cdk10, a Cdc2-related kinase, associates with the Ets2 transcription factor and modulates its transactivation activity

Cdk10 is a Cdc2-related kinase that may play a role in regulating the G2/M phase of the cell cycle. However little is known about the proteins that interact with this putative kinase and contribute to its function in the cell. We report in this study that Cdk10 interacts with the N-terminus of the Ets2 transcription factor, which contains the highly conserved Pointed domain and transactivation domain. The Pointed domain has been implicated in protein-protein interactions and we find that Ets2 requires an intact Pointed domain to bind Cdk10. The Pointed domain of Ets1 is highly similar to Ets2, however Cdk10 does not recognize Ets1 in a two-hybrid assay thereby demonstrating significant binding specificity on the part of Cdk10. We find that Cdk10 binds full length Ets2 in vitro and in vivo and inhibits Ets2 transactivation in mammalian cells.

p300/cAMP-responsive element-binding protein interactions with ets-1 and ets-2 in the transcriptional activation of the human stromelysin promoter

In this paper we show that transcription factors Ets-1 and Ets-2 recruit transcription adapter proteins p300 and CBP (cAMP-responsive element-binding protein) during the transcriptional activation of the human stromelysin promoter, which contains palindromic Ets-binding sites. Ets-2 and p300/CBP exist as a complex in vivo. Two regions of p300/CBP between amino acids (a.a.) 328 and 596 and a. a. 1678 and 2370 independently can interact with Ets-1 and Ets-2 in vitro and in vivo. Both these regions of p300/CBP bind to the transactivation domain of Ets-2, whereas the C-terminal region binds only to the DNA binding domain of Ets-2. The N- and the C-terminal regions of CBP (a.a. 1-1097 and 1678-2442, respectively) which lack histone acetylation activity independently are capable of coactivating Ets-2. Other Ets family transcription factors failed to cooperate with p300/CBP in stimulating the stromelysin promoter. The LXXLL sequence, reported to be important in receptor-coactivator interactions, does not appear to play a role in the interaction of Ets-2 with p300/CBP. Previous studies have shown that the stimulation of transcriptional activation activity of Ets-2 requires phosphorylation of threonine 72 by the Ras/mitogen-activated protein kinase signaling pathway. We show that mutation of this site does not affect its capacity to bind to and to cooperate with p300/CBP.

Identification of a neuregulin and protein-tyrosine phosphatase response element in the nicotinic acetylcholine receptor epsilon subunit gene: regulatory role of an Rts transcription factor

At the neuromuscular synapse, innervation induces endplate-specific expression of adult-type nicotinic acetylcholine receptors by selective expression of their subunit-encoding genes (alpha2betaepsilondelta) in endplate-associated myonuclei. These genes are specifically regulated by protein-tyrosine phosphatase (PTPase) activity. In addition, neuregulin/acetylcholine-receptor-inducing activity, a nerve-derived factor that stimulates nicotinic acetylcholine receptor synthesis, induces adult-type specific epsilon subunit gene expression via activation of a Ras/mitogen-activated protein kinase pathway. However, the DNA regulatory elements and the binding proteins that mediate PTPase and neuregulin-dependent gene expression remain unknown. Herein we report that PTPase, neuregulin, and Ras-dependent regulation of the epsilon subunit gene map to a 15-bp promoter sequence. Interestingly, this same 15-bp sequence appears to be necessary for low epsilon subunit gene expression in extrajunctional regions of the muscle fiber. Site-directed mutagenesis of a putative Ets binding site located within this 15-bp sequence, reduced PTPase, neuregulin, and Ras-dependent regulation. Overexpression of the rat muscle Ets-2 transcription factor resulted in a sequence-specific induction of epsilon subunit promoter activity. Further, a dominant negative mutant of Ets-2 abolished neuregulin-dependent induction of epsilon subunit gene expression. Thus, these results indicate a crucial role for the 15-bp element in determining synapse-specific and neuregulin-mediated motor neuron control of epsilon subunit gene expression and suggest the participation of Ets transcription factor(s) in this control.

The ETS family member ERM contains an alpha-helical acidic activation domain that contacts TAFII60

Transcription factors are modular entities built up of discrete domains, some devoted to DNA binding and others permitting transcriptional modulation. The structure of DNA binding domains has been thoroughly investigated and structural classes clearly defined. In sharp contrast, the structural constraints put on transactivating regions, if any, are mostly unknown. Our investigations focus on ERM, a eukaryotic transcription factor of the ETS family. We have previously shown that ERM harbours two transactivating domains (TADs) with distinct functional features: AD1 lies in the first 72 amino acids of ERM, while AD2 sits in the last 62. Here we show that AD1 is a bona fide acidic TAD, for it activated transcription in yeast cells, while AD2 did not. AD1 contains a 20 amino acid stretch predicted to form an alpha-helix that is found unchanged in the related PEA3 and ER81 transcription factors. Circular dichroism analysis revealed that a 32 amino acid peptide encompassing this region is unstructured in water but folds into a helix when the hydrophobic solvent trifluoroethanol is added. The isolated helix was sufficient to activate transcription and mutations predicted to disrupt it dramatically affected AD1-driven transactivation, whereas mutations decreasing its acidity had more gentle effects. A phenylalanine residue within the helix was particularly sensitive to mutations. Finally, we observed that ERM bound TAFII60 via AD1 and bound TBP and TAFII40, presumably via other activation domains.

Identification of a promoter-specific transactivation domain in the herpes simplex virus regulatory protein ICP4

ICP4 is expressed during the immediate-early phase of infection by herpes simplex virus (HSV) and activates transcription of viral genes during subsequent phases of productive infection. Several members of the alpha-herpesvirus family encode regulatory proteins that have extensive homology with ICP4 and exhibit a transactivation domain (TAD) at the N terminus. The portions of ICP4 required for nuclear localization, DNA binding, and dimerization have been defined, but a domain that is specifically required for transactivation has not been identified. We have defined a promoter-specific ICP4 TAD by analysis of the activity of GAL4-ICP4 fusion proteins cotransfected into HeLa cells with a luciferase reporter gene linked to a promoter with five GAL4 binding sites. The transactivation activity of GAL4-ICP4 hybrids is located entirely within the first 139 residues of ICP4 and is significantly less potent than the activity of GAL4-TAD hybrids derived from ICP4 homologs. ICP4 residues 97 to 109 are a critical component of this N-terminal TAD. Transient transfection assays performed with nonfusion forms of ICP4 and luciferase genes linked to the HSV glycoprotein D (gD) or thymidine kinase (tk) promoter revealed that ICP4 residues 97 to 109 are required for induction of the gD promoter but are not required for induction of the tk promoter. Comparative experiments with ICP4 homologs revealed that the pseudorabies virus TAD is a potent activator of the gD promoter and a weak activator of the tk promoter. Complementation assays revealed that loss of ICP4 residues 97 to 109 reduced the yield of virus from infected cells nearly 500-fold compared to wild-type ICP4. We conclude that ICP4 residues 97 to 109 are a core component of a promoter-specific transactivation domain that is required for efficient replication of herpes simplex virus.

Oncogenic Neu/ErbB-2 increases ets, AP-1, and NF-kappaB-dependent gene expression, and inhibiting ets activation blocks Neu-mediated cellular transformation

Overexpression of Neu (ErbB-2/HER2) is found in approximately 20% of breast tumors. Activation of Neu by a point mutation (NeuT) causes constitutive tyrosine kinase activity of this transmembrane receptor and transforming activity in fibroblasts. To identify downstream targets of Neu, we have analyzed the ability of Neu to activate gene expression. Expression of NeuT, but not normal Neu, caused transcriptional activation of Ets, AP-1, or NF-kappaB-dependent reporter genes. Dominant inhibitory Ras or Raf mutants blocked the Neu-mediated transcriptional activation, confirming that Ras signaling pathways were required for this activation. Analysis with Ets2 mutants indicated that activation of Ets2 transcriptional activity mediated by NeuT or oncogenic Ras required phosphorylation of the same Ets2 residue, threonine 72. Cotransfection of dominant inhibitory Ets2 mutants specifically blocked NeuT-mediated activation of Ets-dependent reporter genes. Furthermore, in focus formation assays using NIH 3T3 cells, the transforming activity of NeuT was inhibited 5-fold when NeuT was cotransfected with a dominant negative Ets2 mutant. However, parallel colony formation assays showed that the Ets2 dominant negative mutant did not inhibit the growth of normal cells. Together, these data show that NeuT activates a variety of transcription factor families via the Ras signaling pathway and that Ets activation is required for NeuT-mediated cellular transformation. Thus, downstream targets of Neu, including Ets transcription factors, may be useful points for therapeutic intervention in Neu/ErbB-2-associated cancers.

The t(12;21) translocation converts AML-1B from an activator to a repressor of transcription

The t(12;21) translocation is present in up to 30% of childhood B-cell acute lymphoblastic and fuses a potential dimerization motif from the ets-related factor TEL to the N terminus of AML1. The t(12;21) translocation encodes a 93-kDa fusion protein that localizes to a high-salt- and detergent-resistant nuclear compartment. This protein binds the enhancer core motif, TGTGGT, and interacts with the AML-1-binding protein, core-binding factor beta. Although TEL/AML-1B retains the C-terminal domain of AML-1B that is required for transactivation of the T-cell receptor beta enhancer, it fails to activate transcription but rather inhibits the basal activity of this enhancer. TEL/AML-1B efficiently interferes with AML-1B dependent transactivation of the T-cell receptor beta enhancer, and coexpression of wild-type TEL does not reverse this inhibition. The N-terminal TEL helix-loop-helix domain is essential for TEL/AML-1B-mediated repression. Thus, the t(12;21) fusion protein dominantly interferes with AML-1B-dependent transcription, suggesting that the inhibition of expression of AML-1 genes is critical for B-cell leukemogenesis.

Functional interaction of c-Ets-1 and GHF-1/Pit-1 mediates Ras activation of pituitary-specific gene expression: mapping of the essential c-Ets-1 domain

The mechanism by which activation of common signal transduction pathways can elicit cell-specific responses remains an important question in biology. To elucidate the molecular mechanism by which the Ras signaling pathway activates a cell-type-specific gene, we have used the pituitary-specific rat prolactin (rPRL) promoter as a target of oncogenic Ras and Raf in GH4 rat pituitary cells. Here we show that expression of either c-Ets-1 or the POU homeo-domain transcription factor GHF-1/Pit-1 enhance the Ras/Raf activation of the rPRL promoter and that coexpression of the two transcription factors results in an even greater synergistic Ras response. By contrast, the related GHF-1-dependent rat growth hormone promoter fails to respond to Ras or Raf, indicating that GHF-1 alone is insufficient to mediate the Ras/Raf effect. Using amino-terminal truncations of c-Ets-1, we have mapped the c-Ets-1 region required to mediate the optimal Ras response to a 40-amino-acid segment which contains a putative mitogen-activated protein kinase site. Finally, dominant-negative Ets and GHF constructs block Ras activation of the rPRL promoter, and each blocks the synergistic activation mediated by the other partner protein, further corroborating that a functional interaction between c-Ets-1 and GHF-1 is required for an optimal Ras response. Thus, the functional interaction of a pituitary-specific transcription factor, GHF-1, with a widely expressed nuclear proto-oncogene product, c-Ets-1, provides one important molecular mechanism by which the general Ras signaling cascade can be interpreted in a cell-type-specific manner.

Regulation of gene expression by transcription factors Ets-1 and Ets-2

The ETS family of transcription factors have a DNA-binding domain in common that binds a core GGA(A/T) DNA sequence. A large number of proteins have now been identified that contain an ETS DNA-binding domain (see review by Wasylyk et al., 1993). Ets-1 was first described as the cellular homolog of v-ets. which is translated as a 135-kDa gag-myb-ets fusion protein from the replication-deficient retrovirus E26 in chickens. Ets-2 was subsequently described as a closely related protein that contains the highly conserved ETS DNA-binding domain. This paper considers the manner by which the two closely related genes, Ets-1 and Ets-2, apparently play distinct roles in embryo development and in the immune system of adult mice. Although both Ets-1 and Ets-2 transform fibroblasts (Seth et al., 1989), the temporal and tissue-specific expression patterns suggest that these two proteins play distinct biological roles and consequently transactivate different downstream cellular target genes.

The Ewing's sarcoma EWS/FLI-1 fusion gene encodes a more potent transcriptional activator and is a more powerful transforming gene than FLI-1

EWS/FLI-1 is a chimeric protein formed by a tumor-specific 11;22 translocation found in both Ewing's sarcoma and primitive neuroectodermal tumor of childhood. EWS/FLI-1 has been shown to be a potent transforming gene, suggesting that it plays an important role in the genesis of these human tumors. We now demonstrate that EWS/FLI-1 has the characteristics of an aberrant transcription factor. Subcellular fractionation experiments localized the EWS/FLI-1 protein to the nucleus of primitive neuroectodermal tumor cells. EWS/FLI-1 specifically bound in vitro an ets-2 consensus sequence similarly to normal FLI-1. When coupled to a GAL4 DNA-binding domain, the amino-terminal EWS/FLI-1 region was a much more potent transcriptional activator than the corresponding amino-terminal domain of FLI-1. Finally, EWS/FLI-1 efficiently transformed NIH 3T3 cells, but FLI-1 did not. These data suggest that EWS/FLI-1, functioning as a transcription factor, leads to a phenotype dramatically different from that of cells expressing FLI-1. EWS/FLI-1 could disrupt normal growth and differentiation either by more efficiently activating FLI-1 target genes or by inappropriately modulating genes normally not responsive to FLI-1.

The Ewing's sarcoma EWS/FLI-1 fusion gene encodes a more potent transcriptional activator and is a more powerful transforming gene than FLI-1

EWS/FLI-1 is a chimeric protein formed by a tumor-specific 11;22 translocation found in both Ewing's sarcoma and primitive neuroectodermal tumor of childhood. EWS/FLI-1 has been shown to be a potent transforming gene, suggesting that it plays an important role in the genesis of these human tumors. We now demonstrate that EWS/FLI-1 has the characteristics of an aberrant transcription factor. Subcellular fractionation experiments localized the EWS/FLI-1 protein to the nucleus of primitive neuroectodermal tumor cells. EWS/FLI-1 specifically bound in vitro an ets-2 consensus sequence similarly to normal FLI-1. When coupled to a GAL4 DNA-binding domain, the amino-terminal EWS/FLI-1 region was a much more potent transcriptional activator than the corresponding amino-terminal domain of FLI-1. Finally, EWS/FLI-1 efficiently transformed NIH 3T3 cells, but FLI-1 did not. These data suggest that EWS/FLI-1, functioning as a transcription factor, leads to a phenotype dramatically different from that of cells expressing FLI-1. EWS/FLI-1 could disrupt normal growth and differentiation either by more efficiently activating FLI-1 target genes or by inappropriately modulating genes normally not responsive to FLI-1.