Selection of DNA binding sites for human transcriptional regulator GATA-6

Helicoverpa armigera GATAe transcriptional factor regulates the expression of Bacillus thuringiensis Cry1Ac receptor gene ABCC2 by its interplay with additional transcription factors

Helicoverpa armigera is a worldwide pest that has been efficiently controlled by transgenic plants expressing Bt Cry toxins. To exert toxicity, Cry toxins bind to different receptors located in larval midgut cells. Previously, we reported that GATA transcription factor GATAe activates the expression of multiple H. armigera Cry1Ac receptors in different insect cell lines. Here, the mechanism involved in GATAe regulation of HaABCC2 gene expression, a key receptor of Cry1Ac, was analyzed. HaGATAe gene silencing by RNAi in H. armigera larvae confirmed the activation role of HaGATAe on the expression of HaABCC2 in the midgut. The contribution of all potential GATAe-binding sites was analyzed by site-directed mutagenesis using Hi5 cells expressing a reporter gene under regulation of different modified HaABCC2 promoters. DNA pull-down assays revealed that GATAe bound to different predicted GATA-binding sites and mutations of the different GATAe-binding sites identified two binding sites responsible for the promoter activity. The binding site B9, which is located near the transcription initiator site, has a major contribution on HaABCC2 expression. Also, DNA pull-down assays revealed that all other members of GATA TF family in H. armigera, besides GATAe, HaGATAa, HaGATAb, HaGATAc and HaGATAd also bound to the HaABCC2 promoter and decreased the GATAe dependent promoter activity. Finally, the potential participation in the regulation of HaABCC2 promoter of several TFs other than GATA TFs expressed in the midgut cells was analyzed. HaHR3 inhibited the GATAe dependent activity of the HaABCC2 promoter, while two other midgut-related TFs, HaCDX and HaSox21, also bound to the HaABCC2 promoter region and increased the GATAe dependent promoter activity. All these data showed that GATAe induces HaABCC2 expression by binding to HaGATAe binding sites in the promoter region and that additional TFs participate in modulating the HaGATAe-driven expression of HaABCC2.

Dimorphic glioblastoma with glial and epithelioid phenotypes: Clonal evolution and immune selection

Purpose

Epithelioid glioblastoma is an unusual histologic variant of malignant glioma. The present study investigates both the genomic and transcriptomic determinants that may promote the development of this tumor.

Methods

Whole-exome sequencing (WES) and whole-transcriptome sequencing (WTS) were performed on an epithelioid glioblastoma, along with a specific bioinformatic pipeline to generate electronic karyotyping and investigate the tumor immune microenvironment. Microdissected sections containing typical glioblastoma features and epithelioid morphology were analyzed separately using the same methodologies.

Results

An epithelioid glioblastoma, with immunopositivity for GFAP, Olig-2, and ATRX but negative for IDH-1 and p53, was identified. The tumor cell content from microdissection was estimated to be 85-90% for both histologic tumor components. WES revealed that both glioma and epithelioid sections contained identical point mutations in PTEN, RB1, TERT promoter, and TP53. Electronic karyotype analysis also revealed similar chromosomal copy number alterations, but the epithelioid component showed additional abnormalities that were not found in the glioblastoma component. The tumor immune microenvironments were strikingly different and WTS revealed high levels of transcripts from myeloid cells as well as M1 and M2 macrophages in the glioma section, while transcripts from CD4+ lymphocytes and NK cells predominated in the epithelioid section.

Conclusion

Epithelioid glioblastoma may be genomically more unstable and oncogenically more advanced, harboring an increased number of mutations and karyotype abnormalities, compared to typical glioblastomas. The tumor immune microenvironment is also different.

GATAe transcription factor is involved in Bacillus thuringiensis Cry1Ac toxin receptor gene expression inducing toxin susceptibility

The insecticidal Cry toxins produced by Bacillus thuringiensis (Bt) are powerful tools for insect control. Cry toxin receptors such as cadherin (CAD), ABCC2 transporter and alkaline phosphatase (ALP), located on insect midgut cells, are needed for Cry toxicity. Although insect cell lines are useful experimental models for elucidating toxin action mechanism, most of them show low expression of Cry-receptors genes. The GATA transcription factor family plays important roles in regulating development and differentiation of intestine stem cells. Here, we investigated whether GATAs transcription factors are involved in the expression of Cry1Ac-receptors genes, using multiple insect cell lines. Four GATA genes were identified in the transcriptome of the midgut tissue from the lepidopteran larvae Helicoverpa armigera. These HaGATA genes were transiently expressed in three lepidopteran cell lines, Spodoptera frugiperda Sf9, H. armigera QB-Ha-E5 and Trichoplusia ni Hi5. Analysis of transcription activity using transcriptional gene-fusions showed that only H. armigera GATAe (HaGATAe) significantly increased the transcription of CAD, ABCC2 and ALP receptors genes in all insect cell lines. Key DNA regions for HaGATAe regulation were identified in the promoter sequence of these Cry-receptors genes by using promoter deletion mapping. The transient expression of HaGATAe in these cell lines, conferred sensitivity to Cry1Ac toxin, although in Hi5 cells the susceptibility to Cry1Ac was lower than in other two cell lines. High sensitivity to Cry1Ac correlated with simultaneous transcription of ABCC2 and CAD genes in Sf9 and QB-Ha-E5 cells. Our results reveal that HaGATAe enhances transcription of several lepidopteran Cry1Ac receptor genes in cultured insect cells.

Material basis research for Huangqi Jianzhong Tang against chronic atrophic gastritis rats through integration of urinary metabonomics and SystemsDock

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqi Jianzhong Tang (HQJZ), a celebrated traditional Chinese medicine (TCM), is commonly used for treatment of chronic atrophic gastritis (CAG) in China.

AIM OF THE STUDY

We aimed to screen out the material basis of HQJZ against CAG.

MATERIALS AND METHODS

CAG rat model was constructed by alternant administrations of ammonia solution and sodium deoxycholate, and the hunger disorder method. Body weight, biochemical indexes and histopathological exam were used to evaluate the efficacy of HQJZ. ¹H NMR-based metabonomics was employed to analyze the urine metabolic features of HQJZ deviated from CAG rats. SystemsDock analysis was utilized to explore the active compounds involved into the efficacy of HQJZ against CAG based on the targeted metabolic biomarkers.

RESULTS

The metabonomic results indicated that HQJZ could significantly improve 16 urinary perturbed metabolites in CAG rats, which were involved into the metabolism of energy and amino acids. And then 28 related proteins and genes were selected out to be the potential targets of HQJZ against CAG based on the six key metabolites closely correlating with biochemical indexes (α-ketoglutarate, valine, sarcosine, glycine, malonate and fumarate). 71 previous identified compounds were docked through systemsDock-aided molecular docking experiments. And the constructed herb-component-protein-metabolite interaction network (HCPMN) revealed the associations between the herbal formulae and CAG. At last, 51 compounds of them were screened as promising active constitutes for the inhibition of CAG, which could act on various targeted proteins.

CONCLUSIONS

he results showed that the approach integrating of metabonomics and systemsDock is a powerful tool to obtain the material basis and regulatory mechanism of TCM formula.

GATA6 phosphorylation by Erk1/2 propels exit from pluripotency and commitment to primitive endoderm

The transcription factor GATA6 and the Fgf/Ras/MAPK signaling pathway are essential for the development of the primitive endoderm (PrE), one of the two lineages derived from the pluripotent inner cell mass (ICM) of mammalian blastocysts. A mutant mouse line in which Gata6-coding exons are replaced with H2BGFP (histone H2B Green Fluorescence Protein fusion protein) was developed to monitor Gata6 promoter activity. In the Gata6-H2BGFP heterozygous blastocysts, the ICM cells that initially had uniform GFP fluorescence signal at E3.5 diverged into two populations by the 64-cell stage, either as the GFP-high PrE or the GFP-low epiblasts (Epi). However in the GATA6-null blastocysts, the originally moderate GFP expression subsided in all ICM cells, indicating that the GATA6 protein is required to maintain its own promoter activity during PrE linage commitment. In embryonic stem cells, expressed GATA6 was shown to bind and activate the Gata6 promoter in PrE differentiation. Mutations of a conserved serine residue (S264) for Erk1/2 phosphorylation in GATA6 protein drastically impacted its ability to activate its own promoter. We conclude that phosphorylation of GATA6 by Erk1/2 compels exit from pluripotent state, and the phosphorylation propels a GATA6 positive feedback regulatory circuit to compel PrE differentiation. Our findings resolve the longstanding question on the dual requirements of GATA6 and Ras/MAPK pathway for PrE commitment of the pluripotent ICM.

Amino-terminal extension of 146 residues of L-type GATA-6 is required for transcriptional activation but not for self-association

Transcription factor GATA-6 plays essential roles in developmental processes and tissue specific functions through regulation of gene expression. GATA-6 mRNA utilizes two Met-codons in frame as translational initiation codons. Deletion of the nucleotide sequence encoding the PEST sequence (Glu(31)-Cys(46)) between the two initiation codons unusually reduced the protein molecular size on SDS-polyacrylamide gel-electrophoresis, and re-introduction of this sequence reversed this change. The long-type (L-type) GATA-6 containing this PEST sequence self-associated similarly to the short-type (S-type) GATA-6, as determined on co-immunoprecipitation of Myc-tagged GATA-6 with HA-tagged GATA-6. The L-type and S-type GATA-6 also interacted mutually. The L-type GATA-6 without the PEST sequence also self-associated and interacted with the S-type GATA-6. The transcriptional activation potential of L-type GATA-6 is higher than that of S-type GATA-6. When the PEST sequence (Glu(31)-Cys(46)) was inserted into the L-type GATA-6 without Arg(13)-Gly(101), the resultant recombinant protein showed significantly higher transcriptional activity, while the construct with an unrelated sequence exhibited lower activity. These results suggest that the Glu(31)-Cys(46) segment plays an important role in the transcriptional activation, although it does not participate in the self-association.

Mechanical stretch upregulates proteins involved in Ca2+ sensitization in urinary bladder smooth muscle hypertrophy

Partial bladder outlet obstruction (pBOO)-induced remodeling of bladder detrusor smooth muscle (DSM) is associated with the modulation of cell signals regulating contraction. We analyzed the DSM from obstructed murine urinary bladders for the temporal regulation of RhoA GTPase and Rho-activated kinase (ROCK), which are linked to Ca(2+) sensitization. In addition, the effects of equibiaxial cell stretch, a condition thought to be associated with pBOO-induced bladder wall smooth muscle hypertrophy and voiding frequency, on the expression of RhoA, ROCK, and C-kinase-activated protein phosphatase I inhibitor (CPI-17) were investigated. DSM from 1-, 3-, 7-, and 14-day obstructed male mice bladders and benign prostatic hyperplasia (BPH)-induced obstructed human bladders revealed overexpression of RhoA and ROCK-β at the mRNA and protein levels compared with control. Primary human bladder myocytes seeded onto type I collagen-coated elastic silicone membranes were subjected to cyclic equibiaxial stretch, mimicking the cellular mechanical stretch in the bladder in vivo, and analyzed for the expression of RhoA, ROCK-β, and CPI-17. Stretch caused a significant increase of RhoA, ROCKβ, and CPI-17 expression. The stretch-induced increase in CPI-17 expression occurs at the transcriptional level and is associated with CPI-17 promoter binding by GATA-6 and NF-κB, the transcription factors responsible for CPI-17 gene transcription. Cell stretch caused by bladder overdistension in pBOO is the likely mechanism for initiating overexpression of the signaling proteins regulating DSM tone.

The transcription factor GATA6 enables self-renewal of colon adenoma stem cells by repressing BMP gene expression

Aberrant activation of WNT signalling and loss of BMP signals represent the two main alterations leading to the initiation of colorectal cancer (CRC). Here we screen for genes required for maintaining the tumour stem cell phenotype and identify the zinc-finger transcription factor GATA6 as a key regulator of the WNT and BMP pathways in CRC. GATA6 directly drives the expression of LGR5 in adenoma stem cells whereas it restricts BMP signalling to differentiated tumour cells. Genetic deletion of Gata6 from mouse colon adenomas increases the levels of BMP factors, which signal to block self-renewal of tumour stem cells. In human tumours, GATA6 competes with β-catenin/TCF4 for binding to a distal regulatory region of the BMP4 locus that has been linked to increased susceptibility to development of CRC. Hence, GATA6 creates an environment permissive for CRC initiation by lowering the threshold of BMP signalling required for tumour stem cell expansion.

Transcription factors GATA-4 and GATA-6: molecular characterization, expression patterns and possible functions during goose (Anser cygnoides) follicle development

The transcription factors GATA-4 and GATA-6, members of the GATA family, play an important role in ovarian cell proliferation, differentiation and apoptosis. In this study, the full-length coding sequences of goose GATA-4 and GATA-6 were cloned and characterized. GATA-4 and GATA-6 consist of 1236 and 1104 nucleotides encoding proteins with 411 and 367 amino acids, respectively. The deduced amino acid sequences of both proteins include two adjacent zinc finger domains with the distinctive form (CVNC-X17-CNAC)-X29-(CANC-X17-CNAC) and share 84.76% identity within this domain. In silico prediction together with matching of the high affinity RRXS(T)Y motif revealed that the GATA-4 protein might be phosphorylated predominantly at S(233), but no phosphorylation site was found in the GATA-6 protein. Real-time quantitative PCR analysis showed that GATA-4 and GATA-6 mRNAs were co-expressed in goose follicles, moderately expressed in granulosa cells and weakly expressed in theca cells. The expression level of GATA-4 mRNA in healthy follicles was significantly higher than in atretic follicles or postovulatory follicles (P<0.01), and the expression level of GATA-6 mRNA in healthy follicles was significantly lower than in atretic follicles or postovulatory follicles (P<0.01). The expression level of GATA-4 mRNA in granulosa cells was downregulated during follicle development; the peak of expression occurred in the 8-10 mm follicles, and the lowest expression was in the F1 follicles. GATA-6 was upregulated and reached its peak expression in the F1 follicles. These results indicate that the molecular structural differences in goose GATA-4 and GATA-6 may be related to their different roles during follicle development.

GATA6 is a crucial regulator of Shh in the limb bud

In the limb bud, patterning along the anterior-posterior (A-P) axis is controlled by Sonic Hedgehog (Shh), a signaling molecule secreted by the “Zone of Polarizing Activity”, an organizer tissue located in the posterior margin of the limb bud. We have found that the transcription factors GATA4 and GATA6, which are key regulators of cell identity, are expressed in an anterior to posterior gradient in the early limb bud, raising the possibility that GATA transcription factors may play an additional role in patterning this tissue. While both GATA4 and GATA6 are expressed in an A-P gradient in the forelimb buds, the hindlimb buds principally express GATA6 in an A-P gradient. Thus, to specifically examine the role of GATA6 in limb patterning we generated Prx1-Cre; GATA6^fl/fl mice, which conditionally delete GATA6 from their developing limb buds. We found that these animals display ectopic expression of both Shh and its transcriptional targets specifically in the anterior mesenchyme of the hindlimb buds. Loss of GATA6 in the developing limbs results in the formation of preaxial polydactyly in the hindlimbs. Conversely, forced expression of GATA6 throughout the limb bud represses expression of Shh and results in hypomorphic limbs. We have found that GATA6 can bind to chromatin (isolated from limb buds) encoding either Shh or Gli1 regulatory elements that drive expression of these genes in this tissue, and demonstrated that GATA6 works synergistically with FOG co-factors to repress expression of luciferase reporters driven by these sequences. Most significantly, we have found that conditional loss of Shh in limb buds lacking GATA6 prevents development of hindlimb polydactyly in these compound mutant embryos, indicating that GATA6 expression in the anterior region of the limb bud blocks hindlimb polydactyly by repressing ectopic expression of Shh.

Sonic Hedgehog (Shh) is a crucial regulator of the growth and anterior-posterior patterning of the developing limb bud, and is produced in the “Zone of Polarizing Activity” in the posterior of the limb bud. Here, we demonstrate that GATA4 and GATA6 (members of the GATA family of transcription factors) are expressed in the anterior mesenchyme of mouse limb buds and that limb bud-specific deletion of GATA6 results in ectopic expression of Shh and its target genes (such as Gli1) in the anterior limb bud mesenchyme, resulting in preaxial polydactyly. Conversely, over-expression of GATA6 in limb buds causes down-regulation of Shh and its target genes, resulting in a decreased number of digits. We also show that GATA6 binds to the sequences that regulate expression of either Shh or Gli1, and that simultaneous deletion of both GATA6 and Shh genes in developing limb buds rescues the polydactylous hindlimb phenotype of GATA6 mutants. Our findings indicate that GATA6 is necessary to repress ectopic expression of both Shh and hedgehog transcriptional targets in the anterior region of the mouse hindlimb bud, and thus demonstrate that GATA transcription factors, in addition to being regulators of cell identity, are important negative regulators of ectopic Shh expression in the limb bud.

Genome-wide screens for in vivo Tinman binding sites identify cardiac enhancers with diverse functional architectures

The NK homeodomain factor Tinman is a crucial regulator of early mesoderm patterning and, together with the GATA factor Pannier and the Dorsocross T-box factors, serves as one of the key cardiogenic factors during specification and differentiation of heart cells. Although the basic framework of regulatory interactions driving heart development has been worked out, only about a dozen genes involved in heart development have been designated as direct Tinman target genes to date, and detailed information about the functional architectures of their cardiac enhancers is lacking. We have used immunoprecipitation of chromatin (ChIP) from embryos at two different stages of early cardiogenesis to obtain a global overview of the sequences bound by Tinman in vivo and their linked genes. Our data from the analysis of ∼50 sequences with high Tinman occupancy show that the majority of such sequences act as enhancers in various mesodermal tissues in which Tinman is active. All of the dorsal mesodermal and cardiac enhancers, but not some of the others, require tinman function. The cardiac enhancers feature diverse arrangements of binding motifs for Tinman, Pannier, and Dorsocross. By employing these cardiac and non-cardiac enhancers in machine learning approaches, we identify a novel motif, termed CEE, as a classifier for cardiac enhancers. In vivo assays for the requirement of the binding motifs of Tinman, Pannier, and Dorsocross, as well as the CEE motifs in a set of cardiac enhancers, show that the Tinman sites are essential in all but one of the tested enhancers; although on occasion they can be functionally redundant with Dorsocross sites. The enhancers differ widely with respect to their requirement for Pannier, Dorsocross, and CEE sites, which we ascribe to their different position in the regulatory circuitry, their distinct temporal and spatial activities during cardiogenesis, and functional redundancies among different factor binding sites.

The Drosophila homeodomain protein Tinman was the first transcription factor found to control the development and differentiation of the heart in any species. In spite of that, our knowledge of the number, identities, and mode of regulation of the downstream target genes of Tinman that are necessary to exert its cardiogenic functions is still very incomplete. To address these issues, we have performed a genome-wide analysis of DNA regions associated with Tinman-binding in embryos and the genes linked to them. The combined data from our in-depth in vivo assays of sequence elements with high Tinman occupancy allow the following general conclusions: (1) The majority of such sequences are active as regulatory elements (called enhancers) in mesodermal tissues that include Tinman-expressing cells. (2) The enhancers active in the heart progenitor cells and the heart generally are dependent on tinman gene activity, whereas those active in non-cardiac mesoderm are often bound neutrally by Tinman. (3) Tinman binding motifs in most cases are essential for cardiac enhancer activity, but in some cases they can be functionally-redundant with those of other cardiogenic factors. (4) Tinman-occupied cardiac enhancers are enriched for a newly discovered binding motif for an unknown factor that is functional in vivo.

GATA-6 and NF-κB activate CPI-17 gene transcription and regulate Ca2+ sensitization of smooth muscle contraction

Protein kinase C (PKC)-potentiated inhibitory protein of 17 kDa (CPI-17) inhibits myosin light chain phosphatase, altering the levels of myosin light chain phosphorylation and Ca(2+) sensitivity in smooth muscle. In this study, we characterized the CPI-17 promoter and identified binding sites for GATA-6 and nuclear factor kappa B (NF-κB). GATA-6 and NF-κB upregulated CPI-17 expression in cultured human and mouse bladder smooth muscle (BSM) cells in an additive manner. CPI-17 expression was decreased upon GATA-6 silencing in cultured BSM cells and in BSM from NF-κB knockout (KO) mice. Moreover, force maintenance by BSM strips from KO mice was decreased compared with the force maintenance of BSM strips from wild-type mice. GATA-6 and NF-κB overexpression was associated with CPI-17 overexpression in BSM from men with benign prostatic hyperplasia (BPH)-induced bladder hypertrophy and in a mouse model of bladder outlet obstruction. Thus, aberrant expression of NF-κB and GATA-6 deregulates CPI-17 expression and the contractile function of smooth muscle. Our data provide insight into how GATA-6 and NF-κB mediate CPI-17 transcription, PKC-mediated signaling, and BSM remodeling associated with lower urinary tract symptoms in patients with BPH.

Regulation of GATA4 transcriptional activity in cardiovascular development and disease

Transcription factors regulate formation and function of the heart, and perturbation of transcription factor expression and regulation disrupts normal heart structure and function. Multiple mechanisms regulate the level and locus-specific activity of transcription factors, including transcription, translation, subcellular localization, posttranslational modifications, and context-dependent interactions with other transcription factors, chromatin remodeling enzymes, and epigenetic regulators. The zinc finger transcription factor GATA4 is among the best-studied cardiac transcriptional factors. This review focuses on molecular mechanisms that regulate GATA4 transcriptional activity in the cardiovascular system, providing a framework to investigate and understand the molecular regulation of cardiac gene transcription by other transcription factors.

Transcriptional repression of Caveolin-1 (CAV1) gene expression by GATA-6 in bladder smooth muscle hypertrophy in mice and human beings

Hypertrophy occurs in urinary bladder wall smooth muscle (BSM) in men with partial bladder outlet obstruction (PBOO) caused by benign prostatic hyperplasia (BPH) and in animal models of PBOO. Hypertrophied BSM from the rabbit model exhibits down-regulation of caveolin-1, a structural and functional protein of caveolae that function as signaling platforms to mediate interaction between receptor proteins and adaptor and effector molecules to regulate signal generation, amplification, and diversification. Caveolin-1 expression is diminished in PBOO-induced BSM hypertrophy in mice and in men with BPH. The proximal promoter of the human and mouse caveolin-1 (CAV1) gene was characterized, and it was observed that the transcription factor GATA-6 binds this promoter, causing reduced expression of caveolin-1. Furthermore, caveolin-1 expression levels inversely correlate with the abundance of GATA-6 in BSM hypertrophy in mice and human beings. Silencing of GATA6 gene expression up-regulates caveolin-1 expression, whereas overexpression of GATA-6 protein sustains the transcriptional repression of caveolin-1 in bladder smooth muscle cells. Together, these data suggest that GATA-6 acts as a transcriptional repressor of CAV1 gene expression in PBOO-induced BSM hypertrophy in men and mice. GATA-6-induced transcriptional repression represents a new regulatory mechanism of CAV1 gene expression in pathologic BSM, and may serve as a target for new therapy for BPH-induced bladder dysfunction in aging men.

The Caenorhabditis elegans GATA factor ELT-1 works through the cell proliferation regulator BRO-1 and the Fusogen EFF-1 to maintain the seam stem-like fate

Seam cells in Caenorhabditis elegans provide a paradigm for the stem cell mode of division, with the ability to both self-renew and produce daughters that differentiate. The transcription factor RNT-1 and its DNA binding partner BRO-1 (homologues of the mammalian cancer-associated stem cell regulators RUNX and CBFβ, respectively) are known rate-limiting regulators of seam cell proliferation. Here, we show, using a combination of comparative genomics and DNA binding assays, that bro-1 expression is directly regulated by the GATA factor ELT-1. elt-1(RNAi) animals display similar seam cell lineage defects to bro-1 mutants, but have an additional phenotype in which seam cells lose their stem cell-like properties and differentiate inappropriately by fusing with the hyp7 epidermal syncytium. This phenotype is dependent on the fusogen EFF-1, which we show is repressed by ELT-1 in seam cells. Overall, our data suggest that ELT-1 has dual roles in the stem-like seam cells, acting both to promote proliferation and prevent differentiation.

Stem cells can both produce differentiated cells and self-renew, producing more stem cells. Choosing between these opposing options is critical for development. Here, we have investigated the molecular genetics underlying this choice in the nematode worm, C. elegans, using the seam cells as a model of stem cell divisions. The transcription factor RNT-1 works together with BRO-1 (homologues of mammalian RUNX and CBFβ genes, respectively) to regulate proliferation of the seam cells, reflecting the roles of RUNX/CBFβ in mammalian stem cells. To better understand how bro-1 is regulated, we looked for conserved regions of non-coding DNA, likely to be of functional importance. We identified a 122 bp conserved non-coding element that is necessary and sufficient for bro-1 expression. Subsequent analysis suggested that the GATA transcription factor ELT-1 directly regulates bro-1. We have found that ELT-1 actually performs two distinct roles, promoting proliferation of seam cells while also preventing them from inappropriately fusing with surrounding tissue and losing their stem-like properties. Furthermore, we propose a link between the retention of stem cell properties and the maintenance of seam cells in a distinct compartment, in which they are protected from differentiation.

Wnt/beta-catenin signalling regulates cardiomyogenesis via GATA transcription factors

A functioning heart muscle is required continuously throughout life. During embryonic development the heart muscle tissue differentiates from mesoderm that has heart-forming potential. Heart-forming potential in the embryonic mesoderm is regulated by pro-cardiogenic transcription factors, such as members of the GATA and NK-2 transcription factor families. Subsequent heart muscle differentiation involves the expression of cytoskeletal proteins, including myosins and troponins. Different Wnt signalling pathways have various functions in heart development. So-called 'canonical' (Wnt/beta-catenin-mediated) signalling has a conserved role in vertebrate heart development, regulating and restricting heart development and subsequent heart muscle differentiation. Here we investigated the way in which Wnt/beta-catenin signalling functionally interacts with the GATA family of pro-cardiogenic transcription factors to regulate subsequent heart muscle differentiation. We used whole Xenopus embryos as an accessible experimental model system for vertebrate heart development. Our experiments confirmed that activation of Wnt signalling results in reduced gata gene expression, as well as reduced gene expression of other pro-cardiogenic transcription factors and heart muscle differentiation markers. Remarkably, we discovered that when GATA function is experimentally restored, the expression of other pro-cardiogenic transcription factors and heart muscle differentiation markers is rescued. These findings, obtained from whole-embryo experiments, show that Wnt signalling regulates heart development at the level of GATA factors, confirming earlier results from tissue-culture experiments. Furthermore, our rescue experiments in Xenopus embryos revealed differences in functional activity between the various GATA transcription factors involved in heart development. We discovered that GATA4 is more efficient at reinstating the gene expression of other pro-cardiogenic transcription factors, whereas GATA6 is more potent at promoting the expression of genes associated with terminal heart muscle differentiation. In conclusion, our findings show that the inhibition of heart development by Wnt/beta-catenin signalling during organogenesis is mediated by the loss of expression of GATA pro-cardiogenic transcription factors and reveal functional differences between those GATA factors in heart development.

Gata3-deficient mice develop parathyroid abnormalities due to dysregulation of the parathyroid-specific transcription factor Gcm2

Heterozygous mutations of GATA3, which encodes a dual zinc-finger transcription factor, cause hypoparathyroidism with sensorineural deafness and renal dysplasia. Here, we have investigated the role of GATA3 in parathyroid function by challenging Gata3+/- mice with a diet low in calcium and vitamin D so as to expose any defects in parathyroid function. This led to a higher mortality among Gata3+/- mice compared with Gata3+/+ mice. Compared with their wild-type littermates, Gata3+/- mice had lower plasma concentrations of calcium and parathyroid hormone (PTH) and smaller parathyroid glands with a reduced Ki-67 proliferation rate. At E11.5, Gata3+/- embryos had smaller parathyroid-thymus primordia with fewer cells expressing the parathyroid-specific gene glial cells missing 2 (Gcm2), the homolog of human GCMB. In contrast, E11.5 Gata3-/- embryos had no Gcm2 expression and by E12.5 had gross defects in the third and fourth pharyngeal pouches, including absent parathyroid-thymus primordia. Electrophoretic mobility shift, luciferase reporter, and chromatin immunoprecipitation assays showed that GATA3 binds specifically to a functional double-GATA motif within the GCMB promoter. Thus, GATA3 is critical for the differentiation and survival of parathyroid progenitor cells and, with GCM2/B, forms part of a transcriptional cascade in parathyroid development and function.

GATA-6 mediates transcriptional activation of aquaporin-5 through interactions with Sp1

We investigated mechanisms underlying GATA-6-mediated transcriptional activation of the alveolar epithelial type I cell-enriched gene aquaporin-5 (AQP5). GATA-6 expression increases in alveolar epithelial cells in primary culture, concurrent with upregulation of AQP5 and transition to a type I cell-like phenotype. Cotransfections in MLE-15 and NIH 3T3 cells demonstrated trans-activation by GATA-6 of a rat 1,716-bp-AQP5-luciferase (-1716-AQP5-Luc) reporter. Electrophoretic mobility shift assay and chromatin immunoprecipitation identified an interaction between GATA-6 and putative binding sites in the AQP5 promoter. However, mutation of these sites did not reduce GATA-6-mediated activation, implicating mechanisms in addition to direct binding of GATA-6 to DNA. A 5'-deletion construct, -358-AQP5-Luc, that does not encompass GATA motifs was still activated by GATA-6 by as much as 50% relative to -1716-AQP5-Luc. Internal deletion of the -358/-173 GC-rich domain, which includes several putative Sp1 consensus sites, reduced trans-activation by approximately 60%, suggesting importance of this region for GATA-mediated activity. -358-AQP5-Luc was similarly activated by both GATA-6 and a GATA DNA-binding defective mutant, whereas cotransfections in Schneider S2 cells demonstrated dose-dependent trans-activation of -358-AQP5-Luc by Sp1. Activation of -358-AQP5-Luc by GATA-6 was dramatically reduced by Sp1 small-interfering RNA, and -358-AQP5-Luc was activated synergistically by GATA-6 and Sp1 in NIH 3T3 cells. Furthermore, association between endogenous GATA-6 and Sp1 was demonstrated by coimmunoprecipitation. These results suggest that transcriptional activation of AQP5 by GATA-6 is mediated at least in part through cooperative interactions with Sp1 occurring at the proximal promoter.

GATA-6 is a novel transcriptional repressor of the human Tenascin-C gene expression in fibroblasts

In this study we show that GATA-6 is a novel repressor of TN-C gene expression. We demonstrated that overexpression of GATA-6 in fibroblasts inhibited basal levels, as well as markedly decreased IL-4- and TGF-beta-induced TN-C mRNA and protein levels. A GATA-6 response element was mapped to position -467 to -460 of the TN-C promoter. In addition, we showed that GATA-6 binds this site both in vitro and in vivo.

Redundancy and evolution of GATA factor requirements in development of the myocardium

The transcription factors, GATA4, 5 and 6, recognize the same DNA sequence and are all expressed in the developing myocardium. However, knockout studies in the mouse have indicated that none of them are absolutely required for the specification of the myocardium. Here we present evidence for redundancy in this family for the first time. Using morpholinos in both Xenopus and zebrafish embryos, we show that GATA4 knockdown, for example, only affects cardiac marker expression in the absence of either GATA5 or GATA6. A similar situation pertains for GATA5 in Xenopus whereas, in zebrafish, GATA5 (faust) plays a major role in driving the myocardial programme. This requirement for GATA5 in zebrafish is for induction of the myocardium, in contrast to the GATA6 requirement in both species, which is for differentiation. This early role for GATA5 in zebrafish correlates with its earlier expression and with an earlier requirement for BMP signalling, suggesting that a mutual maintenance loop for GATA, BMP and Nkx expression is the evolutionarily conserved entity.

CardioSignal: a database of transcriptional regulation in cardiac development and hypertrophy

BACKGROUND

Although extensive research has characterized intricate genetic programs in heart system, the information generated is highly fragmented. Here we have developed a new database called CardioSignal, which was designed for integration of regulatory information on the transcriptional regulation involved in heart development and cardiac hypertrophy.

METHODS

Data about sequences, positions and functional annotation of transcription binding sites, cis-regulatory modules as well as promoters were collected from scientific literature. Genes involved in both processes were also manually gathered, particularly those preferentially expressed in the heart. Data was stored in MySQL database and Perl was used as the server-side programming language.

RESULTS

Currently, CardioSignal contains 677 cardiac genes from twenty species. Among them are 128 cardiac transcription factors. Of the approximately 179 individual promoters from six species, the database also documented 247 experimentally verified binding sites and 64 cis-regulatory modules. CardioSignal may be searched for the promoter of a specific gene by specifying a gene name, Entrez geneID, swissProt accession number and so on. Downstream targets of transcriptional factors and cardiac regulatory modules can also be retrieved through a user-friendly web interface. Also available is experimental supporting evidence. Computational analysis tools were implemented for on-the-fly motif finding and comparative genomic analysis respectively.

CONCLUSIONS

CardioSignal offers a unique resource as it contains simultaneously the promoter collected while correlating the information of transcription factor binding sites and cis-regulatory modules from heart system. We are hopeful that its implementation will contribute toward the elucidation of the complex processes in cardiac development and hypertrophy.

GATA-4 Gene Organization and Analysis of Its Promoter

The mouse GATA-4 gene is separated by six introns, and this gene organization is conserved in rodents and man. The transcriptional start site of the GATA-4 gene is essentially the same in rat heart, stomach and testis, and in cultured cells expressing GATA-4 such as TM3, TM4, I-10 and P19.CL6 cells. The 5'-upstream of the GATA-4 gene is also conserved in rodents and man. We examined its promoter activity by means of luciferase reporter gene assay using testis-derived TM3 and TM4 cells. The GC-boxes and E-box located in the several tens of base pairs upstream of the transcriptional start sites of the GATA-4 gene were found to be critical for its promoter activity in these cells, consistent with the mode of transcription characteristics of the TATA-less promoter. P19.CL6 cells differentiate into beating cardiomyocytes upon induction by DMSO, accompanied by stimulation of the transcription of heart-specific genes including GATA-4. Interestingly, they exhibit increased luciferase reporter gene activity upon induction by DMSO. Both proximal tandem GC-boxes and the E-box are also contributed to the reporter gene activity in P19.CL6 cells.

Further extension of mammalian GATA-6

Mammalian GATA-6, which has conserved tandem zinc fingers (CVNC-X(17)-CNAC)-X(29)-(CXNC-X(17)-CNAC), is essential for the development and specific gene regulation of the heart, gastrointestinal tract and other tissues. GATA-6 recognizes the (A/T/C)GAT(A/T)(A) sequence, and interacts with other transcriptional regulators through its zinc-finger region. The mRNA of GATA-6 uses two Met codons in frame as translational initiation codons, and produces L- and S-type GATA-6 through leaky ribosome scanning. GATA-6 is subjected to cAMP-dependent proteolysis by a proteasome in a heterologous expression system. These protein-based characteristics of GATA-6 will be helpful for the identification of target genes, together with determination of the in vivo binding sites for GATA-6 and understanding of the complex network of gene regulation mediated by GATA-6.

Synergistic induction of DOC-2/DAB2 gene expression in transitional cell carcinoma in the presence of GATA6 and histone deacetylase inhibitor

The down-regulation of DOC-2/DAB2 gene, which encodes a unique phosphoprotein modulating signal pathways elicited by exogenous stimuli, is often associated with several cancer types; however, the underlying mechanism is still unknown. Dramatically different expression levels of DOC-2/DAB2 mRNA and protein are observed among several human transitional cell carcinoma (TCC) cell lines, suggesting that transcriptional regulation may play a role in these cells. In this study, we have shown that the histone acetylation status associated with the 5' upstream regulatory sequence of DOC-2/DAB2 gene is one of the key determinants for its gene expression. In addition, GATA6 but not other GATA family members, such as GATA2 and GATA4, can specifically induce DOC-2/DAB2 promoter activity, although GATA transcription factors share a very similar DNA-binding sequence. We also show that increased histone acetylation and the presence of GATA6 have a synergistic effect on DOC-2/DAB2 promoter activity, which results in the elevation of DOC-2/DAB2 protein expression. Thus, we conclude that transcriptional regulation of DOC-2/DAB2 gene in human TCC is determined by histone acetylation and a specific transcription factor (i.e., GATA6), which underlie the reduced DOC-2/DAB2 protein expression in TCC cells.

Isolation of CHO-K1 clones defective in cAMP-dependent proteolysis, as determined by the stability of exogenously expressed GATA-6

Degradation of the GATA-6(Delta50) protein expressed in a CHO-K1 clone (tc1-17a) is stimulated in the presence of dbcAMP through proteasome without new protein synthesis [FEBS Lett. 408 (1997) 301], whereas the intrinsic GC-box-binding protein was stable. To examine the cellular mechanism responsible for this specific degradation of GATA-6(Delta50), we initially introduced the blasticidin-S deaminase gene carrying a promoter with GATA motifs that are recognized by GATA-6. The resulting cell line (tc2G2) grew in the presence of blasticidin S. However, the presence of both blasticidin S and dbcAMP was lethal due to degradation of GATA-6. Cells resistant to such lethality were isolated by chemical mutagenesis. The GATA-6(Delta50) in these resistant cells was stable in the presence of dbcAMP in contrast to that in the parent tc2G2 cells, as determined by gel-mobility shift analysis and Western blotting. These clones could be beneficial for identification and characterization of the components participating in the signaling pathway for both protein degradation and cAMP-dependent biological processes.

Using the zebrafish model to study GATA transcription factors

The zebrafish is an established animal model system that profits from the availability of strong experimental approaches in both genetics and embryology. As a vertebrate, zebrafish can be used to model many aspects of human development and disease. GATA transcription factors play important roles in the development of many organ systems, including those for hematopoietic, cardiovascular, reproductive, and gut-endoderm derived tissues. The six vertebrate GATA factors are highly conserved in zebrafish at the level of sequence, expression pattern, and function. The identification of mutants, establishment of transgenic GFP reporter fish, and the ease of performing loss- and gain-of-function experiments have all contributed new insight into our understanding of the regulation and function of GATA factors. We review recent advances toward this goal using the zebrafish system with a focus on hematopoiesis and cardiogenesis, and suggest how comparative genetics using the zebrafish genes might reveal core conserved properties, as well as changes in gene function that reflect different morphogenetic programs utilized by various vertebrate embryos.

Regulation of human microsomal epoxide hydrolase gene (EPHX1) expression by the transcription factor GATA-4

Microsomal epoxide hydrolase (mEH) is a bifunctional protein that plays a crucial role in the metabolism of numerous xenobiotics as well as in mediating the hepatic sodium-dependent uptake of bile acids that are involved in numerous physiological processes including the regulation of cholesterol metabolism. The transcription factors and nuclear receptors that control the constitutive and inducible expression of the mEH gene (EPHX1), however, have not been described. To characterize these factors, a series of 5'-deletion constructs have been transfected into human liver-derived HepG2 cells as well as non-hepatic HeLa cells. Promoter activity analysis indicated the presence of a positive regulatory element in the -80/-70 bp region. Sequence analysis revealed a putative GATA site at -79/-74 bp as well as an additional site at -31/-26 bp. Electrophoretic mobility shift assays with an anti-GATA-4 antibody confirmed that GATA-4 bound to these two sites with a dissociation constant of 1.56 nM (-79 site) and 0.65 nM (-31 site). Coexpression of GATA-4 stimulated EPHX1 promoter activity up to 7.5-fold in a dose-dependent manner. Endogenous EPHX1 message in HepG2 cells was also significantly increased by overexpression of GATA-4. Mutating the -79 element resulted in a 65% loss of promoter activity, while mutating the -31 element had no effect on basal activity but greatly reduced the response to additional GATA-4. In HeLa cells, which do not express GATA-4, EPHX1 activity was negligible; however, activity could be reconstituted by the addition of exogenous GATA-4. These results demonstrate that GATA-4 plays a critical role in regulating EPHX1 expression.

A modified sensor chip for surface plasmon resonance enables a rapid determination of sequence specificity of DNA-binding proteins

A novel method is described which rapidly determines specificity of DNA-binding proteins using a surface plasmon resonance (SPR) sensor chip. An oligohistidine-tagged DNA-binding domain of a transcription factor, NtERF2, was immobilised via nitrilotriacetic acid ligands to a sensor chip with an attenuated degree of carboxymethylation. DNA molecules were selected from a pool of randomised oligomers through binding to the immobilised protein and amplified by PCR. After several cycles of selection, during which binding was monitored by SPR, DNA sequences containing a consensus sequence were determined. The time necessary for one cycle is approximately 50 min, which is shorter than existing methods.

GATA-4 interacts distinctively with negative and positive regulatory elements in the Fgf-3 promoter

GATA-4 binds two sites in the Fgf-3 promoter, PS4A and PS13, which function as positive and negative regulatory elements, respectively. In spite of their opposite functions, both PS4A and PS13 acted as potent enhancer elements when three copies of each were appended to a minimal tk promoter. Mutational analysis showed that the negative regulatory activity of PS13 was dependent on its close proximity to the major transcription initiation site (P3), since it was a stronger repressor when moved closer to P3, but had no significant activity when moved to more distal positions. While only the C-terminal zinc finger and the basic domain of GATA-4 were required for binding to PS13, this was insufficient for binding at PS4A. In addition to the PS4A GATA site, the presence of sequences located 10-12 bp distant was required for efficient binding. Both the sequence and location of this second site was crucial for binding and enhancer activity. Truncation deletions of GATA-4 showed that efficient binding to PS4A was dependent on both zinc fingers and the basic domain, suggesting a direct interaction between one zinc finger domain and a possible second site (AGACAA) that shows some similarity to a GATA motif. GATA-4 binding to PS4A through both zinc finger domains was essential for Fgf-3 promoter activity. The substitution in PS4A of a GATA-binding sequence similar to PS13, which only requires a single zinc finger domain, bound GATA-4 efficiently but did not activate the Fgf-3 promoter. These differences in GATA-4 binding were also reflected in DNA bending assays that suggested clear conformational differences between complexes formed on PS4A and PS13.

GATA DNA-binding protein expressed in mouse I-10 Leydig testicular tumor cells

A nuclear extract of the mouse I-10 Leydig tumor cell line was analyzed by gel mobility shift assay with a combination of antibodies for various mammalian GATA proteins. Antibodies for GATA-4 caused a super-shift of the DNA-protein complex, which is formed through GATA-4 binding to an oligonucleotide with a typical GATA motif, while ones for GATA-1, GATA-2, GATA-3, and GATA-6 did not. These results indicated that I-10 cells express GATA-4 protein. Western blotting analysis of cellular proteins also demonstrated the presence of GATA-4 protein, the size of which corresponds to that of the rat orthologous protein transiently expressed in Cos-1 cells. A significant level of GATA-4 expression in I-10 cells would be advantageous for studying the roles of this protein, especially in view of gonadal function. We further examined the binding site preference of GATA-4 expressed in I-10 cells. GATA-4 showed broad sequence specificity similar to GATA-6, the order of binding core site preference being GATA > GATT > GATC, and adenine was favored on both sides of the core for strong binding. Thus the conserved zinc finger domain of GATA proteins is suggested to contribute to the binding sequence preference. GATA-4 expressed in I-10 cells was not susceptible to proteolysis coupled with cAMP signaling.

Characterization of the mouse TFF1 (pS2) gene promoter region

Trefoil peptides (TFFs) with a unique trefoil domain(s) are presumed to function in protection and repair of the gastrointestinal epithelial layer. Three peptide family members are differently distributed in the mouse gastrointestinal tract: TFF1/pS2 specifically in stomach, TFF2/SP mainly in stomach, pancreas and duodenum, and TFF3/ITF in intestine. We cloned and sequenced the mouse TFF1 gene 5'-upstream region by means of the genomic walking procedure. The cloned region was ligated to the luciferase reporter gene and then introduced into mouse gastric surface mucous GSM10 cells which express TFF1 and TFF2. The minimum promoter was located in the region containing the TATA-box between -39 and the transcriptional start site. Further upstream regions stimulated (-2192-- -1630bp, -641-- -243bp, -137-- -39bp) and inhibited (-1630-- -641bp, -243-- -137 bp) luciferase gene expression. These regions as well as short segments conserved in the mouse and human 5'-upstream sequences may be important for modulation of the mRNA level of the TFF1 gene.

Zinc and the immune system

Zn is an essential trace element for all organisms. In human subjects body growth and development is strictly dependent on Zn. The nervous, reproductive and immune systems are particularly influenced by Zn deficiency, as well as by increased levels of Zn. The relationship between Zn and the immune system is complex, since there are four different types of influence associated with Zn. (1) The dietary intake and the resorption of Zn depends on the composition of the diet and also on age and disease status. (2) Zn is a cofactor in more than 300 enzymes influencing various organ functions having a secondary effect on the immune system. (3) Direct effects of Zn on the production, maturation and function of leucocytes. (4) Zn influences the function of immunostimulants used in the experimental systems. Here we summarize all four types of influence on the immune function. Nutritional aspects of Zn, the physiology of Zn, the influence of Zn on enzymes and cellular functions, direct effects of Zn on leucocytes at the cellular and molecular level, Zn-altered function of immunostimulants and the therapeutic use of Zn will be discussed in detail.

HNF3beta and GATA-4 transactivate the liver-enriched homeobox gene, Hex

The orphan homeobox gene, Hex, has a limited domain of expression which includes the developing and adult mouse liver. Hex is expressed in the developing liver coincident with the forkhead/winged helix transcription factor, Hepatocyte Nuclear Factor 3beta (HNF3beta). Although preliminary characterization of the mouse Hex promoter has recently been reported, the identity of the molecular regulators that drive liver expression is not known. We hypothesized that putative HNF3beta and GATA-4 elements within the Hex promoter would confer liver-enriched expression. A series of Hex promoter-driven luciferase reporter constructs were transfected in liver-derived HepG2 and fibroblast-like Cos cells+/-HNF3beta or GATA expression plasmids. The Hex promoter region from nt -235/+22 conferred basal activity in both HepG2 and Cos cells, with the region from -103/+22 conferring liver-enriched activity. HNF3beta and GATA-4 transactivated the promoter via response elements located within nt -103/+22, whereas Sp1 activated the -235/+22 construct. Mutation of the HNF3 element significantly reduced promoter activity in HepG2 cells, whereas this element in isolation conferred HNF3beta responsiveness to a heterologous promoter. Electrophoretic mobility shift assays were performed to confirm transcription factor:DNA binding. We conclude that HNF3beta and GATA-4 contribute to liver-enriched expression of Hex.

Transcription factor GATA-6 activates expression of gastroprotective trefoil genes TFF1 and TFF2

One of the early events in inflammation and epithelial restitution of the gastrointestinal tract is the up-regulation of secretory peptides belonging to the trefoil factor family (TFF) that promote cell migration, protect and heal the mucosa. Their major expression site is stomach (TFF1, TFF2) and intestine (TFF3). Located in the 5'-flanking region of the genes are several consensus sites for members of the GATA transcription factors known to control gut-specific gene expression. By reverse transcription-PCR (RT-PCR), GATA-6 was shown to be expressed in a variety of tumor cell lines of gastric, intestinal and pancreatic origin. In MKN45, KATOIII and LS174T, cotransfection with TFF reporter genes and GATA-6 expression vectors revealed that GATA-6 activates TFF1 and TFF2 4-6-fold, without an effect on TFF3. The functional contribution of GATA binding sequences in the reverse orientation was further characterized by reporter gene assays using TFF2 deletion constructs and by gel shift experiments.

A GATA binding site is involved in the regulation of 15-lipoxygenase-1 expression in human colorectal carcinoma cell line, caco-2

The data presented implicate a GATA binding site in the transcriptional regulation of 15-lipoxygenase-1 (15-LO-1) gene expression in human colorectal carcinoma Caco-2 cells. High expression of GATA-6 mRNA and protein was observed, while GATA-4 mRNA was expressed at a very low level in Caco-2 cells. The expression of GATA-6 was down-regulated, while 15-LO-1 expression was dramatically up-regulated after treatment with sodium butyrate (NaBT). A study using an electrophoretic mobility shift assay indicated that a GATA binding site of the 15-LO-1 promoter region binds to GATA proteins present in both undifferentiated and, to a lesser extent, NaBT-treated (differentiated) Caco-2 cells. Moreover, that DNA binding shift band was disrupted after the addition of GATA-6 antibody in a supershift assay in the absence of NaBT, suggesting that GATA-6 is bound to the GATA binding site of the 15-LO-1 promoter in undifferentiated cells. In contrast, the addition of GATA-6 antibody did not affect the DNA binding ability in NaBT-induced differentiated cells. On the other hand, mutation of the GATA site of the 15-LO-1 promoter decreased the transactivation of the 15-LO-1 promoter as measured by luciferase activity in both FBS and NaBT cultured cells, indicating an unknown GATA binding protein to up-regulate 15-LO-1 expression. These implicate the GATA site at -240 of the proximal region of the 15-LO-1 promoter in the basic transcription of 15-LO-1 gene expression in Caco-2 cells, with GATA-6 acting to repress 15-LO-1 expression.

Characterization of the c-specific promoter of the gene encoding human endothelin-converting enzyme-1 (ECE-1)

Human ECE-1 is expressed in four isoforms with different tissue distribution and its mRNA and protein levels are altered under certain pathophysiological conditions. To investigate the transcriptional regulation of ECE-1, we studied the regulatory region of ECE-1c, the major ECE-1 isoform. A genomic clone comprising the complete human ECE-1 gene including the putative ECE-1c-specific promoter was obtained. Up to 968 bp upstream of the putative c-specific translation initiation start codon and several serial deletion mutants were subcloned into a reporter vector and transfected into endothelial (BAEC, EA.hy926, ECV304) and epithelial (MDA MB435S, MCF7) cells, showing very strong promoter activity in comparison to the SV40 promoter and to the previously described ECE-1a and 1b promoters. Transfection of serial deletion mutants indicated two positive regulatory regions within the promoter (-142/-240 and -240/490) likely involved in binding GATA and ETS transcription factors. RNase protection assay (RPA) and 5'-RACE revealed multiple transcriptional start sites located at about -110, -140 and -350 bp. Site-directed mutagenesis demonstrated a crucial role for the E2F cis-element for basal ECE-1c promoter activity. Additionally, we found a correlation between isoform-specific ECE-1 mRNA levels and corresponding ECE-1a, 1b, 1c promoter activities.