The granulocyte-macrophage colony-stimulating factor promoter cis-acting element CLE0 mediates induction signals in T cells and is recognized by factors related to AP1 and NFAT

Genetic variation in CSF2 (5q31.1) is associated with longitudinal susceptibility to pediatric malaria, severe malarial anemia, and all-cause mortality in a high-burden malaria and HIV region of Kenya

Plasmodium falciparum infections remain among the leading causes of morbidity and mortality in holoendemic transmission areas. Located within region 5q31.1, the colony-stimulating factor 2 gene (CSF2) encodes granulocyte–macrophage colony-stimulating factor (GM-CSF), a hematopoietic growth factor that mediates host immune responses. Since the effect of CSF2 variation on malaria pathogenesis remains unreported, we investigated the impact of two genetic variants in the 5q31.1 gene region flanking CSF2:g-7032 G > A (rs168681:G > A) and CSF2:g.64544T > C (rs246835:T > C) on the rate and timing of malaria and severe malarial anemia (SMA, Hb < 5.0 g/dL) episodes over 36 months of follow-up. Children (n = 1654, aged 2–70 months) were recruited from a holoendemic P. falciparum transmission area of western Kenya. Decreased incidence rate ratio (IRR) for malaria was conferred by inheritance of the CSF2:g.64544 TC genotype (P = 0.0277) and CSF2 AC/GC diplotype (P = 0.0015). Increased IRR for malaria was observed in carriers of the CSF2 AT/GC diplotype (P = 0.0237), while the inheritance of the CSF2 AT haplotype increased the IRR for SMA (P = 0.0166). A model estimating the longitudinal risk of malaria showed decreased hazard rates among CSF2 AC haplotype carriers (P = 0.0045). Investigation of all-cause mortality revealed that inheritance of the GA genotype at CSF2:g-7032 increased the risk of mortality (P = 0.0315). Higher risk of SMA and all-cause mortality were observed in younger children (P < 0.0001 and P = 0.0015), HIV-1(+) individuals (P < 0.0001 and P < 0.0001), and carriers of HbSS (P = 0.0342 and P = 0.0019). Results from this holoendemic P. falciparum area show that variation in gene region 5q31.1 influences susceptibility to malaria, SMA, and mortality, as does age, HIV-1 status, and inheritance of HbSS.

Cooperative Binding of ETS2 and NFAT Links Erk1/2 and Calcineurin Signaling in the Pathogenesis of Cardiac Hypertrophy

BACKGROUND

Cardiac hypertrophy is an independent risk factor for heart failure, a leading cause of morbidity and mortality globally. The calcineurin/NFAT (nuclear factor of activated T cells) pathway and the MAPK (mitogen-activated protein kinase)/Erk (extracellular signal-regulated kinase) pathway contribute to the pathogenesis of cardiac hypertrophy as an interdependent network of signaling cascades. How these pathways interact remains unclear and few direct targets responsible for the prohypertrophic role of NFAT have been described.

METHODS

By engineering cardiomyocyte-specific ETS2 (a member of the E26 transformation-specific sequence [ETS] domain family) knockout mice, we investigated the role of ETS2 in cardiac hypertrophy. Primary cardiomyocytes were used to evaluate ETS2 function in cell growth.

RESULTS

ETS2 is phosphorylated and activated by Erk1/2 on hypertrophic stimulation in both mouse (n=3) and human heart samples (n=8 to 19). Conditional deletion of ETS2 in mouse cardiomyocytes protects against pressure overload-induced cardiac hypertrophy (n=6 to 11). Silencing of ETS2 in the hearts of calcineurin transgenic mice significantly attenuates hypertrophic growth and contractile dysfunction (n=8). As a transcription factor, ETS2 is capable of binding to the promoters of hypertrophic marker genes, such as ANP, BNP, and Rcan1.4 (n=4). We report that ETS2 forms a complex with NFAT to stimulate transcriptional activity through increased NFAT binding to the promoters of at least 2 hypertrophy-stimulated genes: Rcan1.4 and microRNA-223 (=n4 to 6). Suppression of microRNA-223 in cardiomyocytes inhibits calcineurin-mediated cardiac hypertrophy (n=6), revealing microRNA-223 as a novel prohypertrophic target of the calcineurin/NFAT and Erk1/2-ETS2 pathways.

CONCLUSIONS

Our findings point to a critical role for ETS2 in calcineurin/NFAT pathway-driven cardiac hypertrophy and unveil a previously unknown molecular connection between the Erk1/2 activation of ETS2 and expression of NFAT/ETS2 target genes.

Eosinophils Modulate CD4(+) T Cell Responses via High Mobility Group Box-1 in the Pathogenesis of Asthma

Eosinophils have been reported to modulate T cell responses. Previously, we reported that high-mobility group box 1 protein (HMGB1) played a key role in the pathogenesis of asthma. This study was conducted to test our hypothesis that eosinophils could modulate T cell responses via HMGB1 in the pathogenesis of asthma characterized by eosinophilic airway inflammation. We performed in vitro experiments using eosinophils, dendritic cells (DCs), and CD4⁺ T cells obtained from a murine model of asthma. The supernatant of the eosinophil culture was found to significantly increase the levels of interleukin (IL)-4 and IL-5 in the supernatant of CD4⁺ T cells co-cultured with DCs. HMGB1 levels increased in the supernatant of the eosinophil culture stimulated with IL-5. Anti-HMGB1 antibodies significantly attenuated increases of IL-4 and IL-5 levels in the supernatant of CD4⁺ T cells co-cultured with DCs that were induced by the supernatant of the eosinophil culture. In addition, anti-HMGB1 antibodies significantly attenuated the expressions of activation markers (CD44 and CD69) on CD4⁺ T cells. Our data suggest that eosinophils modulate CD4⁺ T cell responses via HMGB1 in the pathogenesis of asthma.

Activation of liver X receptor induces macrophage interleukin-5 expression

IL-5 stimulates production of T15/EO6 IgM antibodies that can block the uptake of oxidized low density lipoprotein by macrophages, whereas a deficiency in macrophage IL-5 expression accelerates development of atherosclerosis. Liver X receptors (LXRs) are ligand-activated transcription factors that can induce macrophage ABCA1 expression and cholesterol efflux, thereby inhibiting the development of atherosclerosis. However, it remains unknown whether additional mechanisms, such as the regulation of macrophage IL-5 expression, are related to the anti-atherogenic properties of LXR. We initially defined IL-5 expression in macrophages where the LXR ligand (T0901317) induced macrophage IL-5 protein expression and secretion. The overexpression of LXR increased, whereas its knockdown inhibited IL-5 expression. Furthermore, we found that LXR activation increased IL-5 transcripts, promoter activity, formation of an LXR·LXR-responsive element complex, and IL-5 protein stability. In vivo, we found that T0901317 increased IL-5 and total IgM levels in plasma and IL-5 expression in multiple tissues in wild type mice. In LDL receptor knock-out (LDLR(-/-)) mice, T0901317 increased IL-5 expression in the aortic root area. Taken together, our studies demonstrate that macrophage IL-5 is a target gene for LXR activation, and the induction of macrophage IL-5 expression can be related to LXR-inhibited atherosclerosis.

Nuclear factor-kappaB does not mediate the inhibitory effects of dexamethasone on granulocyte-macrophage colony-stimulating factor expression

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) reporter constructs containing up to 3.3 kb of upstream promoter sequence were transiently transfected into both Jurkat and HUT78 human T-cell lines. In Jurkat cells, stimulation with phorbol 12-myristate 13-acetate (PMA) plus phytohemaglutinin (PHA) produced robust increases in reporter activity, whereas HUT78 cells showed low levels of reporter induction attributable to constitutive nuclear factor (NF)-kappaB activity. Following mutation of either the proximal NF-kappaB site (-85/-76) or the activator protein1 (AP-1) motif within the conserved lymphokine element 0 (CLE0) site (-54/-31), reporter activity was markedly reduced in both cell lines. Despite this dependence on NF-kappaB and CLE0/AP-1, GM-CSF reporter activity was unaffected by dexamethasone in either cell line. Similarly, an NF-kappaB-dependent reporter was also not repressed by dexamethasone, yet GM-CSF release from HUT78 T cells was inhibited. These data therefore confirm a critical role for both NF-kappaB and CLE0 sites in GM-CSF promoter activation and indicate that NF-kappaB may not mediate glucocorticoid-dependent repression of GM-CSF in these cells.

rVista for comparative sequence-based discovery of functional transcription factor binding sites

Identifying transcriptional regulatory elements represents a significant challenge in annotating the genomes of higher vertebrates. We have developed a computational tool, rVista, for high-throughput discovery of cis-regulatory elements that combines clustering of predicted transcription factor binding sites (TFBSs) and the analysis of interspecies sequence conservation to maximize the identification of functional sites. To assess the ability of rVista to discover true positive TFBSs while minimizing the prediction of false positives, we analyzed the distribution of several TFBSs across 1 Mb of the well-annotated cytokine gene cluster (Hs5q31; Mm11). Because a large number of AP-1, NFAT, and GATA-3 sites have been experimentally identified in this interval, we focused our analysis on the distribution of all binding sites specific for these transcription factors. The exploitation of the orthologous human-mouse dataset resulted in the elimination of > 95% of the approximately 58,000 binding sites predicted on analysis of the human sequence alone, whereas it identified 88% of the experimentally verified binding sites in this region.

Function and regulation of AP-1 subunits in skin physiology and pathology

The mouse skin has become the model of choice to study the regulation and function of AP-1 subunits in many physiological and pathological processes in vivo and in vitro. Genetically modified mice, in vitro reconstituted skin equivalents and epidermal cell lines were established, in which AP-1-regulated genetic programs of cell proliferation, differentiation and tumorigenesis can be analysed. Since the epidermis, as our interface with the environment, is subjected to radiation and injury, signal transduction pathways and critical AP-1 members regulating the mammalian stress response could be identified. Regulated expression of important components of the cytokine network, cell surface receptors and proteases, which orchestrate the process of wound healing has been found to rely on AP-1 activity. Here we review our current knowledge on the function of AP-1 subunits and AP-1 target genes in these fascinating fields of skin physiology and pathology.

DNase I footprinting of the human interleukin-5 gene promoter

A characteristic feature of allergic asthma is the overexpression of the T helper type 2 (Th2) cytokines interleukin-4 (IL-4), IL-5 and IL-13 by T lymphocytes. Of these cytokines, IL-5 is critical for the growth, survival and recruitment of eosinophils which are thought to be responsible for the tissue damage observed in asthmatic airways. The expression of human IL-5 is primarily regulated at the transcriptional level; however, little is known about the mechanisms that control its transcription. Using nuclear extracts from allergen-specific human T-cell clones we have performed DNase I footprinting of the human IL-5 promoter in order to establish sites occupied by transcription factors. We show footprints covering the conserved lymphokine element 0 ¿(CLE0) -60 to -44 base pairs (bp) and GATA (-73 to -62 bp) elements, which have previously been identified to be important in the regulation of the murine IL-5 promoter. We also describe a footprint covering a considerably extended Octamer binding site (-249 to -217 bp), which encompasses two hitherto unidentified CCAAT/enhancer binding protein consensus binding sites. We have also identified a previously unknown Ets binding site (-274 to -264 bp). These novel data on the regions of the human IL-5 promoter that are bound by transcription factors should allow dissection of the regulatory mechanisms involved in the transcription of IL-5 in the T-helper lymphocytes of asthmatics.

The human granulocyte-macrophage colony-stimulating factor gene is autonomously regulated in vivo by an inducible tissue-specific enhancer

The granulocyte-macrophage colony-stimulating factor (GM-CSF) gene is part of a cytokine gene cluster and is directly linked to a conserved upstream inducible enhancer. Here we examined the in vitro and in vivo functions of the human GM-CSF enhancer and found that it was required for the correctly regulated expression of the GM-CSF gene. An inducible DNase I-hypersensitive site appeared within the enhancer in cell types such as T cells, myeloid cells, and endothelial cells that express GM-CSF, but not in nonexpressing cells. In a panel of transfected cells the human GM-CSF enhancer was activated in a tissue-specific manner in parallel with the endogenous gene. The in vivo function of the enhancer was examined in a transgenic mouse model that also addressed the issue of whether the GM-CSF locus was correctly regulated in isolation from other segments of the cytokine gene cluster. After correction for copy number the mean level of human GM-CSF expression in splenocytes from 11 lines of transgenic mice containing a 10.5-kb human GM-CSF transgene was indistinguishable from mouse GM-CSF expression (99% +/- 56% SD). In contrast, a 9.8-kb transgene lacking just the enhancer had a significantly reduced (P = 0.004) and more variable level of activity (29% +/- 89% SD). From these studies we conclude that the GM-CSF enhancer is required for the correct copy number-dependent expression of the human GM-CSF gene and that the GM-CSF gene is regulated independently from DNA elements associated with the closely linked IL-3 gene or other members of the cytokine gene cluster.

Requirement for Distinct Janus Kinases and STAT Proteins in T Cell Proliferation Versus IFN-γ Production Following IL-12 Stimulation

While IL-12 is known to activate JAK2 and TYK2 and induce the phosphorylation of STAT4 and STAT3, little is known regarding how the activation of these signaling molecules is related to the biologic effects of IL-12. Using an IL-12-responsive T cell clone (2D6), we investigated their requirements for proliferation and IFN-γ production of 2D6 cells. 2D6 cells could be maintained with either IL-12 or IL-2. 2D6 lines maintained with IL-12 (2D6IL-12) or IL-2 (2D6IL-2) exhibited comparable levels of proliferation, but produced large or only small amounts of IFN-γ, respectively, when restimulated with IL-12 after starvation of either cytokine. 2D6IL-12 induced TYK2 and STAT4 phosphorylation. In contrast, their phosphorylation was marginally induced in 2D6IL-2. The reduced STAT4 phosphorylation was due to a progressive decrease in the amount of STAT4 protein along with the passages in IL-2-containing medium. 2D6IL-12 and 2D6IL-2 similarly proliferating in response to IL-12 induced comparable levels of JAK2 activation and STAT5 phosphorylation. JAK2 was associated with STAT5, and IL-12-induced STAT5 phosphorylation was elicited in the absence of JAK3 activation. These results indicate that IL-12 has the capacity to induce/maintain STAT4 and STAT5 proteins, and that TYK2 and JAK2 activation correlate with STAT4 phosphorylation/IFN-γ induction and STAT5 phosphorylation/cellular proliferation, respectively.

The Role of Ets-1 in Mast Cell Granulocyte-Macrophage Colony-Stimulating Factor Expression and Activation

Ets-1 is a transcription factor with restricted expression in lymphocytes, and it has been implicated in the regulation of T cell genes such as TCRα, TCRβ, CD4, IL-2, and TNF-α. We show in this study that Ets-1 is also expressed in some mast cells constitutively and can be induced in primary mast cells with stimuli that activate mast cells. We also show that Ets-1 plays a role in the regulation of granulocyte-macrophage CSF (GM-CSF), a cytokine expressed by activated mast cells. We have characterized a murine growth factor-independent mast cell line, FMP6−, derived from a factor-dependent cell line, FMP1.6. FMP6− has acquired a distinct connective tissue mast cell-like phenotype, as characterized by the expression of mast cell proteases MMCP-4 and MMCP-6, expression of IL-12, and the down-regulation of IL-4. The parental FMP1.6 cell line displays a mucosal mast cell-like phenotype. FMP6− cells have increased Ets-1 expression and achieve growth-factor independence by the autocrine production of GM-CSF and IL-3. Transient transfection of an Ets-1 expression construct in FMP6− cells results in transactivation of a GM-CSF reporter, while a point mutation in the consensus Ets binding site in the conserved lymphokine element, CLE0, abolishes Ets-1 transactivation. Importantly, antisense Ets-1 demonstrates an ability to repress the activity of the GM-CSF reporter. These data suggest a role for Ets-1 in mast cell growth regulation and activation, and because of the central role of mast cells in inflammatory processes, such as asthma and rheumatoid arthritis, they identify Ets-1 as potentially contributing to the pathophysiology of such diseases.

Carboxyl-Terminal 15-Amino Acid Sequence of NFATx1 Is Possibly Created by Tissue-Specific Splicing and Is Essential for Transactivation Activity in T Cells

NFAT regulates transcription of a number of cytokine and other immunoregulatory genes. We have isolated NFATx, which is one of four members of the NFAT family of transcription factors and is preferentially expressed in the thymus and peripheral blood leukocytes, and an isoform of NFATx, NFATx1. Here we provide evidence showing that 15 amino acids in the carboxyl-terminal end of NFATx1 are required for its maximum transactivation activity in Jurkat T cells. A fusion between these 15 amino acids and the GAL4 DNA binding domain was capable of transactivating reporters driven by the GAL4 DNA binding site. Interestingly, this 15-amino acid transactivation sequence is well conserved in NFAT family proteins, although the sequences contiguous to the carboxyl-terminal regions of the NFAT family are much less conserved. We also report three additional isoforms of NFATx, designated NFATx2, NFATx3, and NFATx4. This transactivation sequence is altered by tissue-specific alternative splicing in newly isolated NFATx isoforms, resulting in lower transactivation activity in Jurkat T cells. NFATx1 is expressed predominantly in the thymus and peripheral blood leukocyte, while the skeletal muscle expressed primarily NFATx2. In Jurkat cells, transcription from the NFAT site of the IL-2 promoter is activated strongly by NFATx1 but only weakly by NFATx2. These data demonstrate that the 15-amino acid sequence of NFATx1 is a major transactivation sequence required for induction of genes by NFATx1 in T cells and possibly regulates NFAT activity through tissue-specific alternative splicing.

Characterization of cis-Regulatory Elements and Nuclear Factors Conferring Th2-Specific Expression of the IL-5 Gene: A Role for a GATA-Binding Protein

Expression of the IL-5 gene is restricted to the Th2 subset of helper T cells. We have previously defined four cis-regulatory elements of the IL-5 promoter responding to PMA and cAMP in EL-4 cells. We now report that the 1.2-kb region of the IL-5 promoter directs expression of the IL-5 gene in a Th2 clone but not a Th1 clone, indicating that transcription from the IL-5 promoter is Th2 specific. For the functioning of the IL-5 promoter in a Th2 clone, IL-5C and IL-5CLE0 were critical. IL-5CLE0 interacted with both constitutive and inducible nuclear factors (designated NFIL-5CLE0), which existed in both Th1 and Th2 clones, whereas IL-5C interacted with a constitutive nuclear factor (designated NFIL-5C), which was found only in Th2 but not in Th1 clones. Th2 specificity of NFIL-5C was also confirmed using in vitro-differentiated Th1 and Th2 cells derived from TCR-transgenic mice. The sequence for NFIL-5C binding bears homology with GATA-binding sites. The NFIL-5C complex was supershifted by an anti-GATA-3 Ab and inhibited by an oligonucleotide containing GATA-binding sites. We showed preferential expression of GATA-3 in Th2 cells. Finally, we demonstrated that in vitro-translated GATA-3 bound to IL-5C and overexpression of GATA-3 augmented stimulation-dependent IL-5 promoter activity in EL-4 cells. Taken together, our results provide evidence that GATA-related factors may be involved in Th2-specific expression of the IL-5 gene.

Distinct NFAT Family Proteins Are Involved in the Nuclear NFAT-DNA Binding Complexes from Human Thymocyte Subsets

The nuclear factor of activated T cells (NFAT) is involved in the transcriptional induction of cytokine and other immunoregulatory genes during an immune response. Among four distinct NFAT family members identified to date, mRNAs of NFAT1, NFATc, and NFATx are expressed in the thymus. Here, we report the distribution of these three NFAT family members in human fetal thymocyte subsets and in peripheral mature T cells. We show that NFATx mRNA was expressed in all T lymphocyte subsets tested and was highest in CD4+CD8+ double positive (DP) thymocytes. Conversely, NFAT1 mRNA was preferentially expressed in the mature CD4+ single positive (SP) populations. NFATc mRNA was present at low levels in all subsets but strongly induced upon treatment with phorbol ester and calcium ionophore. Interestingly, we detected NFAT-DNA binding complexes in DP thymocytes, albeit at lower levels than in CD4 SP cells. Corresponding to the mRNA expression, we observed that NFATx was responsible for the NFAT-DNA binding in DP thymocytes. Moreover, this DNA binding was inhibited by cyclosporin A, indicating that NFATx nuclear translocation was regulated by the calcineurin phosphatase in DP thymocytes. For the CD4 SP populations, NFAT1 and NFATc, and to some extent NFATx, were responsible for the NFAT-DNA binding complexes. These results indicate that NFAT family members are differentially regulated during the development of T cells, and that NFATx may play a distinct role in calcineurin-dependent signaling in DP thymocytes.

Blockade of T-cell activation by dithiocarbamates involves novel mechanisms of inhibition of nuclear factor of activated T cells

Dithiocarbamates (DTCs) have recently been reported as powerful inhibitors of NF-kappaB activation in a number of cell types. Given the role of this transcription factor in the regulation of gene expression in the inflammatory response, NF-kappaB inhibitors have been suggested as potential therapeutic drugs for inflammatory diseases. We show here that DTCs inhibited both interleukin 2 (IL-2) synthesis and membrane expression of antigens which are induced during T-cell activation. This inhibition, which occurred with a parallel activation of c-Jun transactivating functions and expression, was reflected by transfection experiments at the IL-2 promoter level, and involved not only the inhibition of NF-kappaB-driven reporter activation but also that of nuclear factor of activated T cells (NFAT). Accordingly, electrophoretic mobility shift assays (EMSAs) indicated that pyrrolidine DTC (PDTC) prevented NF-kappaB, and NFAT DNA-binding activity in T cells stimulated with either phorbol myristate acetate plus ionophore or antibodies against the CD3-T-cell receptor complex and simultaneously activated the binding of AP-1. Furthermore, PDTC differentially targeted both NFATp and NFATc family members, inhibiting the transactivation functions of NFATp and mRNA induction of NFATc. Strikingly, Western blotting and immunocytochemical experiments indicated that PDTC promoted a transient and rapid shuttling of NFATp and NFATc, leading to their accelerated export from the nucleus of activated T cells. We propose that the activation of an NFAT kinase by PDTC could be responsible for the rapid shuttling of the NFAT, therefore transiently converting the sustained transactivation of this transcription factor that occurs during lymphocyte activation, and show that c-Jun NH2-terminal kinase (JNK) can act by directly phosphorylating NFATp. In addition, the combined inhibitory effects on NFAT and NF-KB support a potential use of DTCs as immunosuppressants.

Triple synergism of human T-lymphotropic virus type 1-encoded tax, GATA-binding protein, and AP-1 is required for constitutive expression of the interleukin-5 gene in adult T-cell leukemia cells

Accumulated evidence demonstrates that adult T-cell leukemia (ATL) is frequently associated with eosinophilia, and human T-lymphotropic virus type 1 (HTLV-1)-infected cells frequently express interleukin-5 (IL-5). However, the molecular mechanism of constitutive IL-5 expression in HTLV-1-infected cells remains unclear. To clarify the mechanism of aberrant IL-5 expression in HTLV-1-infected cells, we investigated the response of the human IL-5 promoter to the HTLV-1-encoded protein Tax. Cotransfection experiments using Jurkat cells revealed that Tax is incapable of activating the IL-5 promoter by itself but that it synergistically transactivates the promoter with GATA-binding protein (GATA-4) and 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulation. By introducing a series of mutations within the IL-5 promoter, we found that conserved lymphokine element 0 (CLE0) is responsible for mediating the signal induced by Tax-TPA. A deletion construct of the promoter indicated that the -75 GATA element and CLE0 are sufficient to mediate synergistic activation of the IL-5 promoter. Electrophoretic mobility shift assays using Jurkat cell nuclear extracts demonstrated that TPA induces a transcription factor to bind CLE0, and an experiment using JPX-9 cell nuclear extracts showed that Tax enhances this binding activity. An antibody supershift experiment revealed that this band consists of c-Jun and JunD. However, among the Jun family members, only c-Jun is able to cooperate with Tax and GATA-4 to activate the IL-5 promoter. We have determined the minimum factors required for IL-5 gene activation by reconstituting the IL-5 promoter activity in F9 cells. This is the first report to demonstrate the functional involvement of Tax protein in IL-5 gene regulation and to suggest the functional triple synergism among Tax, GATA-4, and AP-1, which disrupts regulated control of the gene and leads to constitutive expression of the IL-5 gene.

Expression of NFAT-family proteins in normal human T cells

NFAT proteins constitute a family of transcription factors involved in mediating signal transduction. Using a panel of specific antisera in immunoprecipitation assays, we found that NFATp (135 kDa) is constitutively expressed in normal human T cells, while synthesis of NFATc (predominant form of 86 kDa) is induced by ionomycin treatment. NFAT4/x was very weakly expressed in unstimulated cells, and its level did not increase upon treatment with activating agents. NFAT3 protein was not observed under any conditions. Higher-molecular-weight species of NFATc (of 110 and 140 kDa) were also detected. In addition, translation of NFATc mRNA apparently initiates at two different AUG codons, giving rise to proteins that differ in size by 36 amino acids. Additional size heterogeneity of both NFATc and NFATp results from phosphorylation. In contrast to ionomycin treatment, exposure of cells to phorbol myristate acetate (PMA) plus anti-CD28 did not induce NFATc, indicating that under these conditions, interleukin-2 synthesis by these cells is apparently independent of NFATc. In DNA binding assays, both PMA plus anti-CD28 and PMA plus ionomycin resulted in nuclear NFAT. Surprisingly, the PMA-ionomycin-induced synthesis of NFATc that was detected by immunoprecipitation was not mirrored in the DNA binding assays: nearly all of the activity was due to NFATp. This is the first study of expression of all family members at the protein level in normal human T cells.

Physical interactions between Ets and NF-kappaB/NFAT proteins play an important role in their cooperative activation of the human immunodeficiency virus enhancer in T cells

The transcriptional regulatory elements of many inducible T-cell genes contain adjacent or overlapping binding sites for the Ets and NF-kappaB/NFAT families of transcription factors. Similar arrays of functionally important NF-kappaB/NFAT and Ets binding sites are present in the transcriptional enhancers of human immunodeficiency viruses types 1 and 2 (HIV-1 and HIV-2), suggesting that this pattern of nuclear protein binding sites reflects an evolutionarily conserved mechanism for regulating inducible T-cell gene expression that has been co-opted during HIV evolution. Despite these findings, the molecular mechanisms by which Ets and NF-kappaB/NFAT proteins cooperatively regulate inducible T-cell gene expression remained unknown. In the studies described in this report, we demonstrated a physical interaction between multiple Ets and NF-kappaB/NFAT proteins both in vitro and in activated normal human T cells. This interaction is mediated by the Ets domain of Ets proteins and the C-terminal region of the Rel homology domains of NF-kappaB/NFAT proteins. In addition, the Ets-NF-kappaB/NFAT interaction requires the presence of DNA binding sites for both proteins, as it is abolished by the DNA intercalating agents propidium iodide and ethidium bromide and enhanced by the presence of synthetic oligonucleotides containing binding sites for Ets and NF-kappaB proteins. A dominant-negative mutant of NF-kappaB p50 that binds DNA but fails to interact with Ets proteins inhibits the synergistic activation of the HIV-1 and HIV-2 enhancers by NF-kappaB (p50 + p65) and Ets-1, suggesting that physical interaction between Ets and NF-kappaB proteins is required for the transcriptional activity of the HIV-1 and HIV-2 enhancers. Taken together, these findings suggest that evolutionarily conserved physical interactions between Ets and NF-kappaB/NFAT proteins are important in regulating the inducible expression of T-cell genes and viruses. These interactions represent a potential target for the development of novel immunosuppressive and antiviral therapies.

Calcineurin-dependent nuclear translocation of a murine transcription factor NFATx: molecular cloning and functional characterization

Members of the nuclear factor of activated T cells (NFAT) are involved in the induction of a number of cytokine genes. We report here cDNA cloning and chromosomal localization of a murine homologue of human NFATx, designated as mNFATx1, and its splicing variants mNFATx2 and m delta NFATx. Northern blot analysis showed mNFATx1 to be predominantly expressed in the thymus. mNFATx1, but not m delta NFATx, produced in COS-7 cells, bound to all NFAT-binding sites of the interleukin (IL)-2 and IL-4 promoters tested. Immunofluorescence assay showed that both mNFATx1 and m delta NFATx introduced into COS-7 cells localized predominantly to the cytoplasm, but did translocate to the nucleus, either by cotransfection with an active form of calcineurin or wild-type calcineurin followed by stimulation with calcium ionophore. Translocation of mNFATx1 correlated well with activation of the murine IL-2 promoter; mNFATx1 translocated under conditions described above, in combination with phorbol 12-myristate 13-acetate, activated the transiently transfected murine IL-2 promoter. Thus, nuclear-translocated mNFATx1 is involved in activation of the IL-2 promoter. These results provide the first evidence for the requirement of calcineurin in the control of mNFATx imported from the cytoplasm to the nucleus and implies that mNFATx may possibly be a substrate of calcineurin in vivo.

The nuclear factor YY1 suppresses the human gamma interferon promoter through two mechanisms: inhibition of AP1 binding and activation of a silencer element

Our group has previously reported that the nuclear factor Yin-Yang 1 (YY1), a ubiquitous DNA-binding protein, is able to interact with a silencer element (BE) in the gamma interferon (IFN-gamma) promoter region. In this study, we demonstrated that YY1 can directly inhibit the activity of the IFN-gamma promoter by interacting with multiple sites in the promoter. In cotransfection assays, a YY1 expression vector significantly inhibited IFN-gamma promoter activity. Mutation of the YY1 binding site in the native IFN-gamma promoter was associated with an increase in the IFN-gamma promoter activity. Analysis of the DNA sequences of the IFN-gamma promoter revealed a second functional YY1 binding site (BED) that overlaps with an AP1 binding site. In this element, AP1 enhancer activity was suppressed by YY1. Since the nuclear level of YY1 does not change upon cell activation, our data support a model that the nuclear factor YY1 acts to suppress basal IFN-gamma transcription by interacting with the promoter at multiple DNA binding sites. This repression can occur through two mechanisms: (i) cooperation with an as-yet-unidentified AP2-like repressor protein and (ii) competition for DNA binding with the transactivating factor AP1.

Recombinant NFAT1 (NFATp) is regulated by calcineurin in T cells and mediates transcription of several cytokine genes

Transcription factors of the NFAT family play a key role in the transcription of cytokine genes and other genes during the immune response. We have identified two new isoforms of the transcription factor NFAT1 (previously termed NFATp) that are the predominant isoforms expressed in murine and human T cells. When expressed in Jurkat T cells, recombinant NFAT1 is regulated, as expected, by the calmodulin-dependent phosphatase calcineurin, and its function is inhibited by the immunosuppressive agent cyclosporin A (CsA). Transactivation by recombinant NFAT1 in Jurkat T cells requires dual stimulation with ionomycin and phorbol 12-myristate 13-acetate; this activity is potentiated by coexpression of constitutively active calcineurin and is inhibited by CsA. Immunocytochemical analysis indicates that recombinant NFAT1 localizes in the cytoplasm of transiently transfected T cells and translocates into the nucleus in a CsA-sensitive manner following ionomycin stimulation. When expressed in COS cells, however, NFAT1 is capable of transactivation, but it is not regulated correctly: its subcellular localization and transcriptional function are not affected by stimulation of the COS cells with ionomycin and phorbol 12-myristate 13-acetate. Recombinant NFAT1 can mediate transcription of the interleukin-2, interleukin-4, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor promoters in T cells, suggesting that NFAT1 contributes to the CsA-sensitive transcription of these genes during the immune response.

T-cell receptor stimulation elicits an early phase of activation and a later phase of deactivation of the transcription factor NFAT1

We show here that NFAT1 is rapidly activated, then slowly deactivated, by stimulation of T cells through their antigen receptor. Within minutes of T-cell receptor stimulation, NFAT1 is dephosphorylated, translocates from the cytoplasm into the nucleus, and shows an increase in its ability to bind to DNA. These changes are dependent on calcium mobilization and calcineurin activation, since they are also elicited by ionomycin and are blocked by the immunosuppressive drug cyclosporin A. After several hours of T-cell receptor stimulation, the majority of the NFAT1 in the cell reverts to its original phosphorylated form, reappears in the cytoplasm, and again displays a low affinity for DNA. Deactivation of NFAT1 is facilitated by phorbol 12-myristate 13-acetate and inhibitors of capacitative calcium entry and most likely reflects the slow return of intracellular free calcium concentrations towards resting levels. Our results suggest that calcineurin-dependent signalling pathways mediate the early activation of NFAT1, while phorbol 12-myristate 13-acetate-dependent feedback pathways contribute to the late deactivation. Persistent NFAT-dependent cytokine gene transcription in activated T cells may be mediated by other NFAT family proteins in addition to NFAT1 during the immune response.

Cold shock domain proteins repress transcription from the GM-CSF promoter

The human granulocyte-macrophage colony stimulating factor (GM-CSF) gene promoter binds a sequence-specific single-strand DNA binding protein termed NF-GMb. We previously demonstrated that the NF-GMb binding sites were required for repression of tumor necrosis factor-alpha (TNF-alpha) induction of the proximal GM-CSF promoter sequences in fibroblasts. We now describe the isolation of two different cDNA clones that encode cold shock domain (CSD) proteins with NF-GMb binding characteristics. One is identical to the previously reported CSD protein dbpB and the other is a previously unreported variant of the dbpA CSD factor. This is the first report of CSD factors binding to a cytokine gene. Nuclear NF-GMb and expressed CSD proteins have the same binding specificity for the GM-CSF promoter and other CSD binding sites. We present evidence that CSD factors are components of the nuclear NF-GMb complex. We also demonstrate that overexpression of the CSD proteins leads to complete repression of the proximal GM-CSF promoter containing the NF-GMb/CSD binding sites. Surprisingly, we show that CSD overexpression can also directly repress a region of the promoter which apparently lacks NF-GMb/CSD binding sites. NF-GMb/CSD factors may hence be acting by two different mechanisms. We discuss the potential importance of CSD factors in maintaining strict regulation of the GM-CSF gene.

A novel interferon regulatory factor family transcription factor, ICSAT/Pip/LSIRF, that negatively regulates the activity of interferon-regulated genes

We have isolated a novel cDNA clone encoding interferon (IFN) consensus sequence-binding protein in adult T-cell leukemia cell line or activated T cells (ICSAT); this protein is the human homolog of the recently cloned Pip/LSIRF. ICSAT is structurally most closely related to the previously cloned ICSBP, a member of the IFN regulatory factor (IRF) family of proteins that binds to interferon consensus sequences (ICSs) found in many promoters of the IFN-regulated genes. Among T-cell lines investigated, ICSAT was abundantly expressed in human T-cell leukemia virus type 1 (HTLV-1)-infected T cells. When the HTLV-1 tax gene was expressed or phorbol myristake acetate-A23187 stimulation was used, ICSAT expression was induced in Jurkat cells which otherwise do not express ICSAT. When the binding of ICSAT to four different ICSs was tested, the relative differences in binding affinities for those ICSs were determined. To study the functional role of ICSAT, we performed cotransfection experiments with the human embryonal carcinoma cell line N-Tera2. ICSAT was demonstrated to possess repressive function over the gene activation induced by IFN stimulation or by IRF-1 cotransfection. Such repressive function is similar to that seen in IRF-2 or ICSBP. However, we have found that ICSAT has a different repressive effect from that of IRF-2 or ICSBP in some IFN-responsive reporter constructs. These results suggest that a novel mechanism of gene regulation by "differential repression" is used by multiple members of repressor proteins with different repressive effects on the IFN-responsive genes.

Characterization of the human granulocyte-macrophage colony-stimulating factor gene promoter: an AP1 complex and an Sp1-related complex transactivate the promoter activity that is suppressed by a YY1 complex

It is well documented that a repeated CATT element in the human granulocyte-macrophage colony-stimulating factor (GM-CSF) gene promoter is required for promoter activity. However, the transcription factors that are able to transactivate this enhancer element remain unidentified. Recently, we have found that nuclear factor YY1 can interact with the enhancer element. Here, we report that in addition to YY1, two other nuclear factors have been identified in the DNA-protein complexes formed by the CATT oligonucleotide and the Jurkat T-cell nuclear protein. One of these factors is AP1, and the other one is an Sp1-related protein. Results from transient transfection of Jurkat T cells have revealed that formation of both AP1 and the Sp1-related complex is required for the full enhancer activity of the CATT element. This result is supported by cotransfection of a c-jun expression vector and mutational analysis of the AP1 site or the Sp1-related protein binding site. In contrast, formation of the YY1 complex suppresses enhancer activity, since deletion of the YY1 complex induces an augmentation of the enhancer activity and overexpression of YY1 results in an attenuation of the enhancer activity. Results from the mechanism study have revealed that YY1 is able to inhibit transactivation mediated by either AP1 or the Sp1-related protein, and YY1 suppressive activity is DNA binding dependent. Taken together, these data support the ideas that AP1 and the Sp1-related nuclear protein are required for transactivation of the human GM-CSF gene promoter and that YY1 can suppress transactivation of the promoter even under inducible conditions.

Kinetics of transcription factors regulating the RANTES chemokine gene reveal a developmental switch in nuclear events during T-lymphocyte maturation

RANTES is a chemoattractant cytokine (chemokine) whose gene is expressed immediately after stimulation of several cell types but upregulated late (3 to 5 days) after activation in normal T lymphocytes. Here we describe two cis-acting elements in the human RANTES promoter that act in T lymphocytes. One site interacts with NFIL6, which is activated within the first 24 h after T-cell activation. The second site binds an apparently novel complex that is upregulated later, between days 3 and 5. These data provide an explanation for the immediate-early expression of RANTES in some cell types and identify apparently novel factors contributing to late RANTES transcription in T cells. The results reveal a developmental switch occurring during normal T-cell maturation coincident with the onset of terminal differentiation and the binding of late-acting factors to sequences of the RANTES promoter.

A compilation of composite regulatory elements affecting gene transcription in vertebrates

Over the past years, evidence has been accumulating for a fundamental role of protein-protein interactions between transcription factors in gene-specific transcription regulation. Many of these interactions run within composite elements containing binding sites for several factors. We have selected 101 composite regulatory elements identified experimentally in the regulatory regions of 64 genes of vertebrates and of their viruses and briefly described them in a compilation. Of these, 82 composite elements are of the synergistic type and 19 of the antagonistic type. Within the synergistic type composite elements, transcription factors bind to the corresponding sites simultaneously, thus cooperatively activating transcription. The factors, binding to their target sites within antagonistic type composite elements, produce opposing effects on transcription. The nucleotide sequence and localization in the genes, the names and brief description of transcription factors, are provided for each composite element, including a representation of experimental data on its functioning. Most of the composite elements (3/4) fall between -250 bp and the transcription start site. The distance between the binding sites within the composite elements described varies from complete overlapping to 80 bp. The compilation of composite elements is presented in the database COMPEL which is electronically accessible by anonymous ftp via internet.

Activation and expression of the nuclear factors of activated T cells, NFATp and NFATc, in human natural killer cells: regulation upon CD16 ligand binding

The putative factors that couple the signal transduction from surface receptors to the activation of cytokine synthesis in natural killer (NK) cells have not been elucidated. We report here that the nuclear factor of activated T cells (NFATp), a cyclosporin A (CsA)-sensitive factor that regulates the transcription of several cytokines, mediates CD16-induced activation of cytokine genes in human NK cells. CD16 (Fc gamma RIIIA)-induced expression of cytokine mRNA in NK cells occurs via a CsA-sensitive and Ca(2+)-dependent mechanism. Stimulation of NK cells with CD16 ligands induces NFAT-like DNA binding activity in the nuclear extracts from these cells, as detected in electrophoretic mobility shift assays. This occurs with fast kinetics after stimulation, via a CsA-sensitive and Ca(2+)-dependent mechanism that does not require de novo protein synthesis. NK cell NFAT is present in the cytosol of nonstimulated cells, migrates to the nucleus upon stimulation, and can associate with AP-1. Two distinct molecules, NFATp and NFATc, have been reported to mediate NFAT activity. The results of supershift assays using NFATp- and NFATc- specific antibodies indicate that NK cell activation early after CD16 ligand binding involves primarily, if not exclusively, NFATp, and Western blot analysis shows that this has the same electrophoretic mobility (approximately 120 kD) as that of T lymphocytes. NK cells do not express NFATc constitutively, but NFATc mRNA accumulation is induced in these cells within 2 h of stimulation with CD16 ligands. However, supershift assays using the available mAb recognizing the T cell NFATc revealed no detectable NFATc protein in nuclear and cytoplasmic extracts from CD16- or phorbol ester-stimulated cells at any time tested, up to 4 h. These results provide the first direct evidence that both CsA-sensitive transcription factors, NFATp and NFATc, are expressed in human NK cells, and that their activation and/or expression can be regulated in primary cells by a single stimulus, that, in the case of CD16 in NK cells, results in early activation of NFATp and subsequently induced expression of NFATc mRNA.

Of the GATA-binding proteins, only GATA-4 selectively regulates the human interleukin-5 gene promoter in interleukin-5-producing cells which express multiple GATA-binding proteins

Interleukin-5 (IL-5) is produced by T lymphocytes and known to support B-cell growth and eosinophilic differentiation of the progenitor cells. Using ATL-16T cells which express IL-5 mRNA, we have identified a region within the human IL-5 gene promoter that regulates IL-5 gene transcription. This cis-acting sequence contains the core binding motif, (A/T)GATA(A/G), for GATA-binding family proteins and thus suggests the involvement of this family members. In this report, we describe the cloning of human GATA-4 (hGATA-4) and show that hGATA-4 selectively interacts with the -70 GATA site within the IL-5 proximal promoter region. By promoter deletion and mutation analyses, we established this region as a positive regulatory element. Cotransfection experiments revealed that both hGATA-4 and phorbol-12-myristate-13-acetate (PMA)-A23187 stimulation are necessary for IL-5 promoter activation. The requirement for another regulatory element called CLE0, which lies downstream of the -70 GATA site, was also demonstrated. ATL-16T cells express mRNAs of three GATA-binding proteins, hGATA-2, hGATA-3, and hGATA-4, and each of them has a potential to bind to the consensus (A/T)GATA(G/A) motif. However, using ATL-16T nuclear extract, we demonstrated that GATA-4 is the only GATA-binding protein that forms a specific DNA-protein complex with the -70 GATA site. An electrophoretic mobility shift assay with extracts of COS cells expressing GATA-binding proteins showed that GATA-4 has the highest binding affinity for the -70 GATA site among the three GATA-binding proteins. When the transactivation abilities were compared among the three, GATA-4 showed the highest activity. These results demonstrate the selective role of GATA-4 in the transcriptional regulation of the IL-5 gene in a circumstance where multiple members of the GATA-binding proteins are expressed.

NFATx, a novel member of the nuclear factor of activated T cells family that is expressed predominantly in the thymus

The nuclear factor of activated T cells (NFAT) regulates cytokine gene expression in T cells through cis-acting elements located in the promoters of cytokine genes. Here, we report the cDNA cloning, chromosomal localization, and initial characterization of a transcription factor related to NFATp and NFATc. The novel molecule, designated NFATx, exhibits in its middle a region very similar to the Rel homology domain in NFATc and NFATp. The amino-terminal region of NFATx also shows significant similarities to corresponding sequences in NFATc and NFATp and contains three copies of a conspicuous 17-residue motif of unknown function. We provide evidence showing that NFATx can reconstitute binding to the NFAT-binding site from the interleukin 2 promoter when combined with AP1 (c-Fos/c-Jun) polypeptides and that NFATx is capable of activating transcription of the interleukin 2 promoter in COS-7 cells when stimulated with phorbol ester and calcium ionophore. NFATx mRNA is preferentially and remarkably found in the thymus and at lower levels in peripheral blood leukocytes. The expression pattern of NFATx, together with its functional activity, strongly suggests that NFATx plays a role in the regulation of gene expression in T cells and immature thymocytes.

Human granulocyte-macrophage colony-stimulating factor enhancer function is associated with cooperative interactions between AP-1 and NFATp/c

The promoter of the human granulocyte-macrophage colony-stimulating factor gene is regulated by an inducible upstream enhancer. The enhancer encompasses three previously defined binding sites for the transcription factor NFAT (GM170, GM330, and GM550) and a novel NFAT site defined here as the GM420 element. While there was considerable redundancy within the enhancer, the GM330, GM420, and GM550 motifs each functioned efficiently in isolation as enhancer elements and bound NFATp and AP-1 in a highly cooperative fashion. These three NFAT sites closely resembled the distal interleukin-2 NFAT site, and methylation interference assays further defined GGA(N)9TCA as a minimum consensus sequence for this family of NFAT sites. By contrast, the GM170 site, which also had conserved GGA and TCA motifs but in which these motifs were separated by 15 bases, supported strong independent but no cooperative binding of AP-1 and NFATp, and this site functioned poorly as an enhancer element. While both the GM330 and GM420 elements were closely associated with the inducible DNase I-hypersensitive site within the enhancer, the GM420 element was the only NFAT site located within a 160-bp HincII-BalI fragment defined by deletion analysis as the essential core of the enhancer. The GM420 element was unusual, however, in containing a high-affinity NFATp/c-binding sequence (TGGAAAGA) immediately upstream of the sequence TGACATCA which more closely resembled a cyclic AMP response-like element than an AP-1 site. We suggest that the cooperative binding of NFATp/c and AP-1 requires a particular spacing of sites and that their cooperativity and induction via independent pathways ensure very tight regulation of the granulocyte-macrophage colony-stimulating factor enhancer.

Identification of a DNA binding site for the nuclear factor YY1 in the human GM-CSF core promoter

It has been well documented that the repeated CATT(A/T) sequence, localized between -64 and -35 in the human GM-CSF promoter, is required for the promoter activity, and this region likely serves as a core recognition sequence for a cellular transcription factor. However, the transcription factor that interacts with this site was not identified. Here, we report that this element contains a binding site for the nuclear factor YY1, which has not been reported to play a role in the regulation of cytokine gene transcription. Results from transient transfection assays of the Jurkat T cell line revealed that this repeated CATT(A/T) element exhibited enhancer activity when linked to both the human IFN-gamma promoter and the TK promoter. Mutation of the YY1 binding site eliminated about 60% of the enhancer activity of the element. We have found that the YY1 binding site could form two specific DNA-protein complexes, A and B, with Jurkat nuclear proteins in the electrophoretic mobility shift assay and that the binding of these complexes correlates with the enhancer activity. UV cross-linking analysis revealed that the A complex is a multi-protein complex and in addition to YY1, other proteins are required for formation of the protein complex. Cotransfection assays with a YY1 expression vector revealed that overexpression of YY1 resulted in an inhibitory effect on the repeated CATT(A/T) element, indicating that in addition to YY1, cofactors also are required for the activator function of the A complex.

Immortalization-susceptible elements and their binding factors mediate rejuvenation of regulation of the type I collagenase gene in simian virus 40 large T antigen-transformed immortal human fibroblasts

Dramatic changes occur in expression of the type I collagenase gene during the process of immortalization in simian virus 40 large T antigen-transformed human fibroblasts (S. Imai and T. Takano, Biochem. Biophys. Res. Commun. 189:148-153, 1992). From transient transfection assays, it was determined that these changes involved the functions of two immortalization-susceptible cis-acting elements, ISE1 and ISE2, located in a 100-bp region about 1.7 kb upstream. The profiles of binding of an activator, Proserpine, to the enhancer ISE1 were similar in the extracts of young, senescent preimmortalized and immortalized cells. ISE2 contained both negative and positive regulatory elements located adjacent to each other. The positive regulatory element consisted of a tandem array of putative Ets family- and AP-1-binding sites. An activator, Pluto, interacted with this positive regulatory element and had an AP-1-related component as a complex. The binding activity of Pluto was predominantly detected only in the extract from senescent preimmortalized cells. In contrast, a repressor, Orpheus, which bound to the ATG-rich negative regulatory element of ISE2, was prominently detected in extracts from both young preimmortalized and immortalized cells and appeared to suppress transcription in an orientation-dependent manner. Thus, the interplay of Pluto and Orpheus was suggested to be crucial for regulation of the collagenase gene accompanying in vitro aging and immortalization. Proserpine seemed to interact with Pluto to mediate strong expression of the collagenase gene in cellular senescence. On the basis of these results, we propose a model for regulation of the collagenase gene during in vitro aging and immortalization.

Immortalization-susceptible elements and their binding factors mediate rejuvenation of regulation of the type I collagenase gene in simian virus 40 large T antigen-transformed immortal human fibroblasts

Dramatic changes occur in expression of the type I collagenase gene during the process of immortalization in simian virus 40 large T antigen-transformed human fibroblasts (S. Imai and T. Takano, Biochem. Biophys. Res. Commun. 189:148-153, 1992). From transient transfection assays, it was determined that these changes involved the functions of two immortalization-susceptible cis-acting elements, ISE1 and ISE2, located in a 100-bp region about 1.7 kb upstream. The profiles of binding of an activator, Proserpine, to the enhancer ISE1 were similar in the extracts of young, senescent preimmortalized and immortalized cells. ISE2 contained both negative and positive regulatory elements located adjacent to each other. The positive regulatory element consisted of a tandem array of putative Ets family- and AP-1-binding sites. An activator, Pluto, interacted with this positive regulatory element and had an AP-1-related component as a complex. The binding activity of Pluto was predominantly detected only in the extract from senescent preimmortalized cells. In contrast, a repressor, Orpheus, which bound to the ATG-rich negative regulatory element of ISE2, was prominently detected in extracts from both young preimmortalized and immortalized cells and appeared to suppress transcription in an orientation-dependent manner. Thus, the interplay of Pluto and Orpheus was suggested to be crucial for regulation of the collagenase gene accompanying in vitro aging and immortalization. Proserpine seemed to interact with Pluto to mediate strong expression of the collagenase gene in cellular senescence. On the basis of these results, we propose a model for regulation of the collagenase gene during in vitro aging and immortalization.

A sequence-specific single-strand DNA binding protein that contacts repressor sequences in the human GM-CSF promoter

NF-GMb is a nuclear factor that binds to the proximal promoter of the human granulocyte-macrophage colony stimulating factor (GM-CSF) gene. NF-GMb has a subunit molecular weight of 22 kDa, is constitutively expressed in embryonic fibroblasts and binds to sequences within the adjacent CK-1 and CK-2 elements (CK-1/CK-2 region), located at approximately -100 in the GM-CSF gene promoter. These elements are conserved in haemopoietic growth factor (HGF) genes. NF-GMb binding requires the presence of repeated 5'CAGG3' sequences that overlap the binding sites for positive activators. Surprisingly, NF-GMb was found to bind solely to single-strand DNA, namely the non-coding strand of the GM-CSF CK-1/CK-2 region. NF-GMb may belong to a family of single-strand DNA binding (ssdb) proteins that have 5'CAGG3' sequences within their binding sites. Functional analysis of the proximal GM-CSF promoter revealed that sequences in the -114 to -79 region of the promoter containing the NF-GMb binding sites had no intrinsic activity in fibroblasts but could, however, repress tumour necrosis factor-alpha (TNF-alpha) inducible expression directed by downstream promoter sequences (-65 to -31). Subsequent mutation analysis showed that sequences involved in repression correlated with those required for NF-GMb binding.

Calcineurin potentiates activation of the granulocyte-macrophage colony-stimulating factor gene in T cells: involvement of the conserved lymphokine element 0

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-2 (IL-2) are produced by stimulation with phorbol-12-myristate acetate (PMA) and calcium ionophore (A23187) in human T cell leukemia Jurkat cells. The expression of GM-CSF and IL-2 is inhibited by immunosuppressive drugs such as cyclosporin A (CsA) and FK506. Earlier studies on the IL-2 gene expression showed that overexpression of calcineurin (CN), a Ca2+/calmodulin-dependent protein phosphatase, can stimulate transcription from the IL-2 promoter through the NF-AT-binding site. In this study, we obtained evidence that transfection of the cDNAs for CN A (catalytic) and CN B (regulatory) subunits also augments transcription from the GM-CSF promoter and recovers the transcription inhibited by CsA. The constitutively active type of the CN A subunit, which lacks the auto-inhibitory and calmodulin-binding domains, acts in synergy with PMA to activate transcription from the GM-CSF promoter. We also found that the active CN partially replaces calcium ionophore in synergy with PMA to induce expression of endogenous GM-CSF and IL-2. By multimerizing the regulatory elements of the GM-CSF promoter, we found that one of the target sites for the CN action is the conserved lymphokine element 0 (CLE0), located at positions between -54 and -40. Mobility shift assays showed that the CLE0 sequence has an AP1-binding site and is associated with an NF-AT-like factor, termed NF-CLE0 gamma. NF-CLE0 gamma binding is induced by PMA/A23187 and is inhibited by treatment with CsA. These results suggest that CN is involved in the coordinated induction of the GM-CSF and IL-2 genes and that the CLE0 sequence of the GM-CSF gene is a functional analogue of the NF-AT-binding site in the IL-2 promoter, which mediates signals downstream of T cell activation.