scholarly journals KLF4 Interacts with β-Catenin/TCF4 and Blocks p300/CBP Recruitment by β-Catenin

2009 ◽  
Vol 30 (2) ◽  
pp. 372-381 ◽  
Author(s):  
Paul M. Evans ◽  
Xi Chen ◽  
Wen Zhang ◽  
Chunming Liu
Keyword(s):  
Transcription Factor ◽  
Wnt Signaling ◽  
Molecular Mechanisms ◽  
Somatic Mutations ◽  
Target Genes ◽  
Early Event ◽  
Transactivation Domain ◽  
Epithelial Surface ◽  
Intestinal Differentiation ◽  
Human Intestinal Epithelium

ABSTRACT Wnt signaling is crucial in the organization and maintenance of the human intestinal epithelium, and somatic mutations that result in deregulated Wnt signaling are an early event in the development of colorectal cancer. The Wnt ligand ultimately results in the stabilization of cytoplasmic β-catenin, which is then free to enter the nucleus and activate transcription through its interaction with the transcription factor TCF4. Our laboratory recently found that KLF4, a transcription factor highly expressed in the adult intestine and critical for intestinal differentiation, interacts with β-catenin and inhibits Wnt signaling. In this study, we characterize the molecular mechanisms of KLF4-mediated inhibition of Wnt/β-catenin signaling. We find that the KLF4 directly interacts with the C-terminal transactivation domain of β-catenin and inhibits p300/CBP recruitment by β-catenin. KLF4 inhibits p300/CBP-mediated β-catenin acetylation as well as histone acetylation on Wnt target genes. In addition, we observe that KLF4 directly interacts with TCF4 independently of β-catenin and that KLF4 and TCF4 are expressed in similar patterns within the large intestine, with greatest staining near the epithelial surface. These results provide a deeper understanding of the regulation of β-catenin in the intestine and will have important implications in cancer and stem cell research.

scholarly journals Control of mitotic chromosome condensation by the fission yeast transcription factor Zas1

2018 ◽  
Vol 217 (7) ◽  
pp. 2383-2401 ◽  
Author(s):  
Christoph Schiklenk ◽  
Boryana Petrova ◽  
Marc Kschonsak ◽  
Markus Hassler ◽  
Carlo Klein ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Fission Yeast ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Chromosome Condensation ◽  
Condensation Process ◽  
Transactivation Domain ◽  
Promoter Regions ◽  
Live Cell Microscopy ◽  
Mitotic Chromosome Condensation

Although the formation of rod-shaped chromosomes is vital for the correct segregation of eukaryotic genomes during cell divisions, the molecular mechanisms that control the chromosome condensation process have remained largely unknown. Here, we identify the C2H2 zinc-finger transcription factor Zas1 as a key regulator of mitotic condensation dynamics in a quantitative live-cell microscopy screen of the fission yeast Schizosaccharomyces pombe. By binding to specific DNA target sequences in their promoter regions, Zas1 controls expression of the Cnd1 subunit of the condensin protein complex and several other target genes, whose combined misregulation in zas1 mutants results in defects in chromosome condensation and segregation. Genetic and biochemical analysis reveals an evolutionarily conserved transactivation domain motif in Zas1 that is pivotal to its function in gene regulation. Our results suggest that this motif, together with the Zas1 C-terminal helical domain to which it binds, creates a cis/trans switch module for transcriptional regulation of genes that control chromosome condensation.

scholarly journals Activation of the Transcription Factor GLI1 by WNT Signaling Underlies the Role of SULFATASE 2 as a Regulator of Tissue Regeneration

2013 ◽  
Vol 288 (29) ◽  
pp. 21389-21398 ◽  
Author(s):  
Ikuo Nakamura ◽  
Maite G. Fernandez-Barrena ◽  
Maria C. Ortiz-Ruiz ◽  
Luciana L. Almada ◽  
Chunling Hu ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Wnt Signaling ◽  
Cyclin D1 ◽  
Signaling Pathways ◽  
Tissue Regeneration ◽  
Molecular Mechanisms ◽  
Nuclear Translocation ◽  
Hepatocyte Proliferation ◽  
Dependent Manner ◽  
Gli1 Expression

Tissue regeneration requires the activation of a set of specific growth signaling pathways. The identity of these cascades and their biological roles are known; however, the molecular mechanisms regulating the interplay between these pathways remain poorly understood. Here, we define a new role for SULFATASE 2 (SULF2) in regulating tissue regeneration and define the WNT-GLI1 axis as a novel downstream effector for this sulfatase in a liver model of tissue regeneration. SULF2 is a heparan sulfate 6-O-endosulfatase, which releases growth factors from extracellular storage sites turning active multiple signaling pathways. We demonstrate that SULF2-KO mice display delayed regeneration after partial hepatectomy (PH). Mechanistic analysis of the SULF2-KO phenotype showed a decrease in WNT signaling pathway activity in vivo. In isolated hepatocytes, SULF2 deficiency blocked WNT-induced β-CATENIN nuclear translocation, TCF activation, and proliferation. Furthermore, we identified the transcription factor GLI1 as a novel target of the SULF2-WNT cascade. WNT induces GLI1 expression in a SULF2- and β-CATENIN-dependent manner. GLI1-KO mice phenocopied the SULF2-KO, showing delayed regeneration and decreased hepatocyte proliferation. Moreover, we identified CYCLIN D1, a key mediator of cell growth during tissue regeneration, as a GLI1 transcriptional target. GLI1 binds to the cyclin d1 promoter and regulates its activity and expression. Finally, restoring GLI1 expression in the liver of SULF2-KO mice after PH rescues CYCLIN D1 expression and hepatocyte proliferation to wild-type levels. Thus, together these findings define a novel pathway in which SULF2 regulates tissue regeneration in part via the activation of a novel WNT-GLI1-CYCLIN D1 pathway.

GA Binding Protein (GABP) Is Required for Development and Maturation of Myeloid Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 776-776
Author(s):  
Zhongfa Yang ◽  
Alan G. Rosmarin
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Target Genes ◽  
Embryonic Stem ◽  
Myeloid Cells ◽  
Transactivation Domain ◽  
Wild Type ◽  
Floxed Allele

Abstract GABP is an ets transcription factor that regulates transcription of key myeloid genes, including CD18 (beta2 leukocyte integrin), neutrophil elastase, lysozyme, and other key mediators of the inflammatory response; it is also known to regulate important cell cycle control genes. GABP consists of two distinct and unrelated proteins that, together, form a functional transcription factor complex. GABPalpha (GABPa) is an ets protein that binds to DNA; it forms a tetrameric complex by recruiting its partner, GABPbeta (GABPb), which contains the transactivation domain. GABPa is a single copy gene in both the human and murine genomes and it is the only protein that can recruit GABPb to DNA. We cloned GABPa from a murine genomic BAC library and prepared a targeting vector in which exon 9 (which encodes the GABPa ets domain) was flanked by loxP (floxed) recombination sites. The targeting construct was electroporated into embryonic stem cells, homologous recombinants were implanted into pseudopregnant mice, heterozygous floxed GABPa mice were identified, and intercrossing yielded expected Mendelian ratios of wild type, heterozygous, and homozygous floxed GABPa mice. Breeding of heterozygous floxed GABPa mice to CMV-Cre mice (which express Cre recombinase in all tissues) yielded expected numbers of hemizygous mice (only one intact GABPa allele), but no nullizygous (GABPa−/−) mice among 64 pups; we conclude that homozygous deletion of GABPa causes an embryonic lethal defect. To determine the effect of GABPa deletion on myeloid cell development, we bred heterozygous and homozygous floxed mice to LysMCre mice, which express Cre only in myeloid cells. These mice had a normal complement of myeloid cells but, unexpectedly, PCR indicated that their Gr1+ myeloid cells retained an intact (undeleted) floxed GABPa allele. We detected similar numbers of in vitro myeloid colonies from bone marrow of wild type, heterozygous floxed, and homozygous floxed progeny of LysMCre matings. However, PCR of twenty individual in vitro colonies from homozygous floxed mice indicated that they all retained an intact floxed allele. Breeding of floxed GABPa/LysMCre mice with hemizygous mice indicated that retention of a floxed allele was not due to incomplete deletion by LysMCre; rather, it appears that only myeloid cells that retain an intact GABPa allele can survive to mature in vitro or in vivo. We prepared murine embryonic fibroblasts from homozygous floxed mice and efficiently deleted GABPa in vitro. We found striking abnormalities in proliferation and G1/S phase arrest. We used quantitative RT-PCR to identify mechanisms that account for the altered growth of GABPa null cells. We found dramatically reduced expression of known GABP target genes that regulate DNA synthesis and cell cycle that appear to account for the proliferative defect. We conclude that GABPa is required for growth and maturation of myeloid cells and we identified downstream targets that may account for their failure to proliferate and mature in vitro and in vivo.

Genomic landscape of HBV-related hepatocellular carcinoma in south China patients with high mutational frequency of TP53 and TERT promoter.

2019 ◽  
Vol 37 (15_suppl) ◽  
pp. e15670-e15670
Author(s):  
Jiazhou Ye ◽  
Yinguang Wang ◽  
Rong Liang ◽  
Xue Wu ◽  
Yang Shao ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Cycle ◽  
Wnt Signaling ◽  
South China ◽  
Molecular Mechanisms ◽  
Somatic Mutations ◽  
Biological Effects ◽  
Cell Cycle Control ◽  
Tert Promoter ◽  
Genomic Landscape

e15670 Background: Development of hepatocellular carcinoma (HCC) is a complex process with accumulations of polygene abnormalities and multi-pathway misregulation. Hepatitis B virus (HBV) exposure can cause liver damage and promote hepatocarcinogenesis via various biological effects. We aimed to investigate the molecular mechanisms underlying the etiology of HBV-related HCC development, and provide new insights into novel molecular targets. Methods: 84 HBV-positive HCC patients from Guangxi Province, South China, who underwent hepatic resection, were enrolled in this study. Genomic alterations were analyzed in pair-matched tumor and adjacent normal tissue using a hybridization capture-based next-generation sequencing (NGS) assay targeting 422 cancer-relevant genes. Results: In total, 691 somatic mutations, 166 copy number variations and 10 gene fusions were detected in 81 (96.4%) of 84 tumor samples. The most commonly mutated gene is TP53 in this cohort (84% of the patients), which is much higher than its frequency in the reported overall HCC patients. TERT promoter has somatic mutations in 32% of the patients, reactivation of which has been implicated in multiple cancer types. Dysfunction in the cell cycle control pathway (TP53, RB1, CCND1, CDKN2A and CCNE1) was dominant, followed by PI3K/AKT cascade (PIK3CA, AKT3, MTOR, TSC1 and TSC2), while genes of WNT signaling pathway (CTNNB1, APC and AXIN2) were mutated at a lower frequency. In addition, 69 variants in 25 DNA damage repair (DDR) genes were identified in 37 (45.7%) patients. Patients with DDR mutations had a higher tumor mutation burden (TMB) than those without DDR mutations. Conclusions: This study revealed a unique genomic landscape of HBV-related HCC. Besides TP53 being the highest mutated gene, a significant fraction of patients was identified with TERT promoter mutations, suggesting that TERT may play a role in HBV-related hepatocarcinogenesis as a novel molecular marker. Furthermore, the most common biological processes affected by HBV status in HCC were cell cycle control, PI3K/AKT and WNT signaling pathways. The possible synergistic effects of HBV in hepatocarcinogenesis warrant further investigations.

scholarly journals Hepatocyte nuclear factor-1β regulates Wnt signaling through genome-wide competition with β-catenin/lymphoid enhancer binding factor

2019 ◽  
Vol 116 (48) ◽  
pp. 24133-24142 ◽  
Author(s):  
Siu Chiu Chan ◽  
Ying Zhang ◽  
Marco Pontoglio ◽  
Peter Igarashi
Keyword(s):  
Transcription Factor ◽  
Wnt Signaling ◽  
Target Genes ◽  
Cystic Kidney ◽  
Nuclear Factor ◽  
Hepatocyte Nuclear Factor ◽  
Wild Type ◽  
Genome Wide ◽  
Binding Factor ◽  
Mutant Cells

Hepatocyte nuclear factor-1β (HNF-1β) is a tissue-specific transcription factor that is essential for normal kidney development and renal tubular function. Mutations of HNF-1β produce cystic kidney disease, a phenotype associated with deregulation of canonical (β-catenin–dependent) Wnt signaling. Here, we show that ablation of HNF-1β in mIMCD3 renal epithelial cells produces hyperresponsiveness to Wnt ligands and increases expression of Wnt target genes, including Axin2, Ccdc80, and Rnf43. Levels of β-catenin and expression of Wnt target genes are also increased in HNF-1β mutant mouse kidneys. Genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) in wild-type and mutant cells showed that ablation of HNF-1β increases by 6-fold the number of sites on chromatin that are occupied by β-catenin. Remarkably, 50% of the sites that are occupied by β-catenin in HNF-1β mutant cells colocalize with HNF-1β–occupied sites in wild-type cells, indicating widespread reciprocal binding. We found that the Wnt target genes Ccdc80 and Rnf43 contain a composite DNA element comprising a β-catenin/lymphoid enhancer binding factor (LEF) site overlapping with an HNF-1β half-site. HNF-1β and β-catenin/LEF compete for binding to this element, and thereby HNF-1β inhibits β-catenin–dependent transcription. Collectively, these studies reveal a mechanism whereby a transcription factor constrains canonical Wnt signaling through direct inhibition of β-catenin/LEF chromatin binding.

Large-Scale Integration of Gene Profiling Identifies TCF7L2/TCF4 as the Most Frequently Dysregulated Wnt Signaling Component In AML

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2480-2480
Author(s):  
Siti Sarah Daud ◽  
Alan K Burnett ◽  
Richard L Darley ◽  
Alex Tonks
Keyword(s):  
Transcription Factor ◽  
Wnt Signaling ◽  
Large Scale ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Function Analysis ◽  
Genetic Models ◽  
Nuclear Accumulation ◽  
Functional Relationships ◽  
Linear Contrasts

Abstract Abstract 2480 Acute myeloid leukemia (AML) represents one of the most genetically heterogeneous malignancies; however, some processes are commonly dysregulated. One of the most frequently dysregulated processes in AML is Wnt signaling. In solid cancers, aberrant Wnt signaling has been shown to promote cancer by increasing nuclear accumulation of β-catenin and with consequent activation of target genes. In AML, overexpression of β-catenin is also common; in addition however, patient studies and genetic models indicate that other components of the Wnt pathway are also commonly dysregulated and may mediate transcriptional changes independently of β-catenin. The aim of this study was to identify aberrantly regulated Wnt components and target genes in AML by interactome analysis of the AML Affymetrix GeneChip® 3` expression microarray datasets; a network building algorithm used to understand relationships between genes. Analysis and interpretation of microarray data is still both biologically and computationally challenging. To address this, we performed batch adjustment to the large scale AML dataset by merging gene expression profile (GEP) data derived from different database sources (including different array platforms). GEPs data were generated from our AML patients enrolled in two different AML NCRI-MRC UK clinical trials using two different Affymetrix platforms, HG-U133A (n=216) and HG-U133Plus2.0 (n=139). GEPs from normal CD34+ bone marrow samples were downloaded from ArrayExpress (n=26). In order to compare AML vs. normal haematopoietic GEP, all data were merged into a single dataset. Individual. CEL files were imported into Partek® Genomics Suite™ and GC-RMA normalization was applied. Linear contrasts, mixed model analysis of variance with false discovery rate correction (P<0.05) and threshold analysis (>1.5 or <1.5 fold-change) were applied to the adjusted data followed by gene enrichment analysis using MetaCore™ (GeneGo Inc). Batch adjustment was performed using Distance Weight Discrimination (DWD) method to the merged GEPs. Prior to further inferential and gene ontology testing, the DWD merged datasets showed significant reduction in the source of data bias with GEP clustered according to their biological variation rather than technical variation. As a result, we present a final list of 58 significant changes in the expression of Wnt related genes in AML. Enrichment by protein function analysis highlighted 8 Wnt transcription factors to be dysregulated (TCF7L2/TCF4, MYC, NANOG, WT1, RUNX2, p300, TCF7, SMAD2), along with 5 receptors (CD44, FZD3, FZD4, FZD5, LDLR), 3 types of phosphatases (B56G, PR61-β, PPP2R5A) and other categories of Wnt related objects (n=33). Consistent findings were seen with previously established Wnt-associated genes specific to AML (CD44, WT1, MYC) showing that data sources from DWD adjustment was effective. We sought to evaluate the significant biological and functional relationships within the genes in the final dataset by transcription factor target modeling using MetaCore™ Interactome tools. Direct network interaction uncovered TCF7L2/TCF4 as the most significantly upregulated Wnt transcription factor with concurrent high expression of its downstream Wnt responsive genes CD44, AXIN1, ID2 that were also present in the final list. Importantly, β-catenin is unlikely to contribute to this transcriptional activation due to the fact that our data showed increased transcription of β-catenin degradation complexes (or negative regulation of Wnt signalling). Specifically, RUVBL1, that directly increases β-catenin activity was significantly downregulated, whereas the other significantly overexpressed upstream genes (APC, CSNK1E, AXIN1, WT1) are known to have inhibitory effect on β-catenin-mediated transcription. In summary, by using multiple GEP data from a large AML cohort in conjunction with robust statistical adjustments, we have identified TCF7L2/TCF4 mediated transcription as the most significant Wnt-regulated process to be altered in AML compared with normal blasts. We also predict that transcription of TCF7L2/TCF4 regulated genes is likely to be independent of β-catenin, supporting observations in genetic models which indicate that β-catenin (and γ-catenin) are redundant for normal haematopoiesis and are not required for TCF-mediated transcription. Disclosures: No relevant conflicts of interest to declare.

Detection and functional characterization of a novel MEF2A variation responsible for familial dilated cardiomyopathy

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Qi Qiao ◽  
Cui-Mei Zhao ◽  
Chen-Xi Yang ◽  
Jia-Ning Gu ◽  
Yu-Han Guo ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Dilated Cardiomyopathy ◽  
Sanger Sequencing ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Functional Characterization ◽  
Luciferase Assay ◽  
Chinese Family ◽  
Sequencing Analysis ◽  
Loss Of Function

AbstractObjectivesDilated cardiomyopathy (DCM) represents the most frequent form of cardiomyopathy, leading to heart failure, cardiac arrhythmias and death. Accumulating evidence convincingly demonstrates the crucial role of genetic defects in the pathogenesis of DCM, and over 100 culprit genes have been implicated with DCM. However, DCM is of substantial genetic heterogeneity, and the genetic determinants underpinning DCM remain largely elusive.MethodsWhole-exome sequencing and bioinformatical analyses were implemented in a consanguineous Chinese family with DCM. A total of 380 clinically annotated control individuals and 166 more DCM index cases then underwent Sanger sequencing analysis for the identified genetic variation. The functional characteristics of the variant were delineated by utilizing a dual-luciferase assay system.ResultsA heterozygous variation in the MEF2A gene (encoding myocyte enhancer factor 2A, a transcription factor pivotal for embryonic cardiogenesis and postnatal cardiac adaptation), NM_001365204.1: c.718G>T; p. (Gly240*), was identified, and verified by Sanger sequencing to segregate with autosome-dominant DCM in the family with complete penetrance. The nonsense variation was neither detected in 760 control chromosomes nor found in 166 more DCM probands. Functional analyses revealed that the variant lost transactivation on the validated target genes MYH6 and FHL2, both causally linked to DCM. Furthermore, the variation nullified the synergistic activation between MEF2A and GATA4, another key transcription factor involved in DCM.ConclusionsThe findings firstly indicate that MEF2A loss-of-function variation predisposes to DCM in humans, providing novel insight into the molecular mechanisms of DCM and suggesting potential implications for genetic testing and prognostic evaluation of DCM patients.

scholarly journals Cleidocranial dysplasia. A molecular and clinical review.

2018 ◽  
Vol 8 (1) ◽  
pp. 35-38
Author(s):  
Andrea Avendaño ◽  
Francisco Cammarata-Scalisi ◽  
Mochamad Fahlevi Rizal ◽  
Sarworini Bagio Budiardjo ◽  
Margaretha Suharsini ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Autosomal Dominant ◽  
Cleidocranial Dysplasia ◽  
Supernumerary Teeth ◽  
Phenotypic Characteristics ◽  
Autosomal Dominant Disorder ◽  
Dental Abnormalities ◽  
Related Transcription Factor

Cleidocranial dysplasia (CCD) is a rare autosomal dominant disorder characterized by skeletal and dental abnormalities primarily, short stature, aplasia or hypoplasia of clavicles, open fontanelles and supernumerary teeth. Heterozygous mutations of the runt related transcription factor 2 (RUNX2) gene have been found in approximately 60-70% of cases leaving a large number of cases with no defined genetic cause which led us to delve into molecular mechanisms underlying CCD and thus to detect potential target genes to be explored in these patients. In this review we also highlight very broadly the phenotypic characteristics of previously reported patients with CCD.

scholarly journals Heterogeneity in the transcriptional response of the human pathogen Aspergillus fumigatus to the antifungal agent caspofungin

Genetics ◽  
2021 ◽  
Author(s):  
Ana Cristina Colabardini ◽  
Fang Wang ◽  
Zhiqiang Dong ◽  
Lakhansing Pardeshi ◽  
Marina Campos Rocha ◽  
...  
Keyword(s):  
Cell Wall ◽  
Transcription Factor ◽  
Aspergillus Fumigatus ◽  
Antifungal Agent ◽  
Iron Homeostasis ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Invasive Pulmonary Aspergillosis ◽  
Transcriptional Response ◽  
Cell Wall Remodeling

Abstract Aspergillus fumigatus is the main causative agent of invasive pulmonary aspergillosis (IPA), a severe disease that affects immunosuppressed patients worldwide. The fungistatic drug caspofungin is the second line of therapy against IPA but has increasingly been used against clinical strains that are resistant to azoles, the first line antifungal therapy. In high concentrations, caspofungin induces a tolerance phenotype with partial reestablishment of fungal growth called caspofungin paradoxical effect (CPE), resulting from a change in the composition of the cell wall. An increasing number of studies has shown that different isolates of A. fumigatus exhibit phenotypic heterogeneity, including heterogeneity in their CPE response. To gain insights into the underlying molecular mechanisms of CPE response heterogeneity, we analyzed the transcriptomes of two A. fumigatus reference strains, Af293 and CEA17, exposed to low and high caspofungin concentrations. We found that there is a core transcriptional response that involves genes related to cell wall remodeling processes, mitochondrial function, transmembrane transport, and amino acid and ergosterol metabolism, and a variable response related to secondary metabolite (SM) biosynthesis and iron homeostasis. Specifically, we show here that the overexpression of a SM pathway that works as an iron chelator extinguishes the CPE in both backgrounds, whereas iron depletion is detrimental for the CPE in Af293 but not in CEA17. We next investigated the function of the transcription factor CrzA, whose deletion was previously shown to result in heterogeneity in the CPE response of the Af293 and CEA17 strains. We found that CrzA constitutively binds to and modulates the expression of several genes related to processes involved in caspofungin tolerance, and that crzA deletion differentially impacts the SM production and growth of Af293 and CEA17. As opposed to the ΔcrzACEA17 mutant, the ΔcrzA Af293 mutant fails to activate cell wall remodeling genes upon caspofungin exposure, which most likely severely affects its macrostructure and extinguishes its CPE. This work describes how heterogeneity in the response to an antifungal agent between A. fumigatus strains stems from heterogeneity in the function of a transcription factor and its downstream target genes.

scholarly journals Klf4 Cooperates with Oct3/4 and Sox2 To Activate the Lefty1 Core Promoter in Embryonic Stem Cells

2006 ◽  
Vol 26 (20) ◽  
pp. 7772-7782 ◽  
Author(s):  
Yuhki Nakatake ◽  
Nobutaka Fukui ◽  
Yuko Iwamatsu ◽  
Shinji Masui ◽  
Kadue Takahashi ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Target Genes ◽  
Core Promoter ◽  
Es Cells ◽  
Embryonic Stem ◽  
Functional Screening ◽  
Transactivation Domain ◽  
Enhancer Element ◽  
Differentiated Cells ◽  
Promoter Dna

ABSTRACT Although the POU transcription factor Oct3/4 is pivotal in maintaining self renewal of embryonic stem (ES) cells, little is known of its molecular mechanisms. We previously reported that the N-terminal transactivation domain of Oct3/4 is required for activation of Lefty1 expression (H. Niwa, S. Masui, I. Chambers, A. G. Smith, and J. Miyazaki, Mol. Cell. Biol. 22:1526-1536, 2002). Here we test whether Lefty1 is a direct target of Oct3/4. We identified an ES cell-specific enhancer upstream of the Lefty1 promoter that contains binding sites for Oct3/4 and Sox2. Unlike other known Oct3/4-Sox2-dependent enhancers, however, this enhancer element could not be activated by Oct3/4 and Sox2 in differentiated cells. By functional screening of ES-specific transcription factors, we found that Krüppel-like factor 4 (Klf4) cooperates with Oct3/4 and Sox2 to activate Lefty1 expression, and that Klf4 acts as a mediating factor that specifically binds to the proximal element of the Lefty1 promoter. DNA microarray analysis revealed that a subset of putative Oct3/4 target genes may be regulated in the same manner. Our findings shed light on a novel function of Oct3/4 in ES cells.

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