Molecular dissection of the mouse interleukin-4 promoter

Association of IL-4 Polymorphisms with Allergic Rhinitis in Jordanian Population

Background and objectives: Allergic rhinitis has complex patterns of inheritance, and single nucleotide polymorphisms, a common genetic variation in a population, exert a significant role in allergic rhinitis pathology. The current study aimed to investigate the association of Interleukin-4 (IL-4) polymorphisms with allergic rhinitis. Materials and Methods: Our study included 158 patients with allergic rhinitis and 140 healthy controls from Jordan that were genotyped for IL-4 single nucleotide polymorphisms (SNPs) C-589T (rs2243250) and T-2979G (rs2227284) using restriction fragment length polymorphism-polymerase chain reaction. Statistical analysis was conducted using IBM SPSS Statistics version 24 software. Results: The results showed that the allelic frequency of the minor alleles was 0.19 and 0.67 for C-589T (rs2243250) and T-2979G (rs2227284) in the allergic rhinitis patients, respectively, while it was 0.18 for C-589T (rs2243250) and 0.64 T-2979G (rs2227284) in the control group. The homozygous (TT) genotype of C-589T (rs2243250) was significantly associated with allergic rhinitis (p < 0.05), while there was no association of any of T-2979G (rs2227284) genotypes with allergic rhinitis. Conclusions: The results of this study indicate that genetic inter-population variation precipitates the differences in the percentages of many diseases among populations, including allergic rhinitis.

The receptor NLRP3 is a transcriptional regulator of TH2 differentiation

The receptor NLRP3 is involved in the formation of the NLRP3 inflammasome that activates caspase-1 and mediates the release of interleukin 1β (IL-1β) and IL-18. Whether NLRP3 can shape immunological function independently of inflammasomes is unclear. We found that NLRP3 expression in CD4(+) T cells specifically supported a T helper type 2 (TH2) transcriptional program in a cell-intrinsic manner. NLRP3, but not the inflammasome adaptor ASC or caspase-1, positively regulated a TH2 program. In TH2 cells, NLRP3 bound the Il4 promoter and transactivated it in conjunction with the transcription factor IRF4. Nlrp3-deficient TH2 cells supported melanoma tumor growth in an IL-4-dependent manner and also promoted asthma-like symptoms. Our results demonstrate the ability of NLRP3 to act as a key transcription factor in TH2 differentiation.

Early growth response protein-1 (Egr-1) is preferentially expressed in T helper type 2 (Th2) cells and is involved in acute transcription of the Th2 cytokine interleukin-4

The early growth response gene product Egr-1 has been shown to have great impact on growth, proliferation, and differentiation in a wide variety of cells, including T cells. In this study, we show that Egr-1 is rapidly induced upon T cell stimulation and is expressed predominantly in T helper type 2 (Th2) compared with type 1 (Th1) cells. We further investigate the role of Egr-1 in regulation of the Th2 cytokine interleukin-4 (IL-4) expression. IL-4 is a key Th2 cytokine that regulates humoral immunity and also causes allergic inflammation. Regulation of IL-4 gene transcription in Th2 cells has been shown to be controlled by multiple T cell receptor (TCR)-induced transcription factors. However, only a few transcription factors were shown to be selectively induced in differentiated Th2 cells in response to TCR stimulation. Chromatin immunoprecipitation analysis demonstrates that Egr-1 binds to the IL-4 promoter in vivo upon T cell stimulation. Ectopic expression of Egr-1 enhances endogenous IL-4 mRNA expression and elevates IL-4 promoter activity. We also show that Egr-1, nuclear factor of activated T cell, and NF-kappaB cooperatively bind to an NFAT/NF-kappaB-overlapping IL-4 enhancer element and activate the IL-4 promoter synergistically. Furthermore, we show that antisense oligonucleotides that knock down Egr-1 expression attenuate IL-4 transcription. Our study provides the first evidence that Egr-1 protein is differentially expressed in Th1 and Th2 cells and is involved in the acute phase of the IL-4 transcription in response to TCR stimulation.

Mina, an Il4 repressor, controls T helper type 2 bias

T helper type 2 (T(H)2) bias, which is the propensity of naive CD4(+) T cells to differentiate into interleukin 4 (IL-4)-secreting T(H)2 cells, is a genetic trait that affects susceptibility to infectious, autoimmune and allergic diseases. T(H)2 bias correlates with the amount of IL-4 initially secreted by newly activated helper T cells that feeds back positively through the pathway of the IL-4 receptor and the transcription factors STAT6 and GATA-3 to drive T(H)2 development. Here we identify Mina, a member of the jumonji C (JmjC) protein family, as a genetic determinant of T(H)2 bias. Mina specifically bound to and repressed the Il4 promoter. Mina overexpression in transgenic mice impaired Il4 expression, whereas its knockdown in primary CD4(+) T cells led to Il4 derepression. Our findings collectively provide mechanistic insight into an Il4-regulatory pathway that controls helper T cell differentiation and genetic variation in T(H)2 bias.

Yin-Yang 1 regulates effector cytokine gene expression and T(H)2 immune responses

BACKGROUND

The transcription factor Yin-Yang 1 (YY-1) binds to the promoter regions of several T-cell cytokine genes, but the expression and contribution of this factor to cytokine gene expression and T-cell activation in vivo is not clear.

OBJECTIVE

We sought to better define the role of YY-1 in T-cell gene regulation and allergic immune responses.

METHODS

We studied cytokine gene expression in T lymphocytes isolated from wild-type mice and heterozygous littermates bearing 1 targeted yy-1 allele (yy-1(+/-) mice). T cells were stimulated with anti-T-cell receptor (anti-TCR) plus CD28 antibodies or with peptide antigen plus antigen-presenting cells by using newly generated yy-1(+/-) TCR transgenic mice. We also studied ovalbumin-driven allergic immune responses in a mouse model of asthma and YY-1 expression in lung tissue from human asthmatic subjects.

RESULTS

CD4(+) T cells from yy-1(+/-) mice secreted significantly less IL-4 and IFN-gamma compared with wild-type littermates after TCR-dependent activation, whereas IL-2 production was not significantly affected. Both airway inflammation and recall splenocyte IL-4 production were inhibited in yy-1(+/-) mice, as was antigen-driven T-cell proliferation. YY-1 expression was higher in airway biopsy specimens from asthmatic compared with control subjects.

CONCLUSION

These data indicate that YY-1 regulates T-cell cytokine gene expression and allergic immune responses in a gene dose-dependent manner.

Phosphoinositide-dependent kinase 1 targets protein kinase A in a pathway that regulates interleukin 4

CD28 plays a critical role in T cell immune responses. Although the kinase Akt has been shown to act downstream of CD28 in T helper (Th)1 cytokine induction, it does not induce Th2 cytokines such as interleukin 4 (IL-4). We recently reported that phosphoinositide-dependent kinase 1 (PDK1) partially corrects the defect in IL-4 production present in CD28-deficient T cells, suggesting that PDK1 regulates IL-4 independently of Akt. We now describe a signaling pathway in which PDK1 targets IL-4 in the murine Th2 cell line D10. PDK1-mediated activation of this pathway is dependent on protein kinase A (PKA) and the nuclear factor of activated T cells (NFAT) P1 transcriptional element in the IL-4 promoter. PDK1 localizes to the immune synapse in a phosphatidylinositol 3-kinase–dependent manner, partially colocalizes with PKA at the synapse, and physically interacts with PKA. In RNA interference knockdown experiments, PDK1 is necessary for phosphorylation of PKA in T cells, as well as for activation of the IL-4 NFAT P1 element by the T cell receptor (TCR) and CD28. Phosphorylation of the critical PKA threonine residue is stimulated by engagement of TCR/CD28 via a PDK1-dependent mechanism. These findings together define a pathway linking the kinases PDK1 and PKA in the induction of the Th2 cytokine IL-4.

c-Jun N-terminal kinase is involved in mercuric ions-mediated interleukin-4 secretion in mast cells

BACKGROUND

Interleukin (IL)-4 plays a prominent role in immune response. Mercuric compounds upregulate IL-4 expression in animal tissues, and this upregulation plays a role in mercuric-mediated immunomodulation. Mercuric ions-mediated IL-4 expression was observed in vitro in T lymphocytes and mast cells. In the present study, we investigated molecular mechanisms responsible for this effect of mercuric ions in mast cells.

METHODS

C1.MC/C57.1 mouse mast cells were exposed in vitro to increasing concentrations of Hg(2+) in the absence or presence of the specific c-Jun N-terminal kinase (JNK) inhibitor SP600125. The level of phosphorylated c-Jun in mast cells was determined by Western blotting, JNK activity assessed with in vitro kinase assay and the amount of secreted IL-4 determined by ELISA.

RESULTS

We observed that Hg(2+) upregulated c-Jun phosphorylation on Ser 73 at concentrations which overlapped concentrations mediating IL-4 secretion. Phosphorylation of c-Jun in mast cells was associated with an increase in JNK activity. The specific JNK inhibitor SP600125 abolished both mercuric-induced c-Jun phosphorylation and IL-4 secretion in mast cells.

CONCLUSIONS

These observations are consistent with the hypothesis that JNK is one of the signaling proteins mediating the effect of Hg(2+) on IL-4 expression in mast cells and is engaged in environmentally mediated immunomodulation.

A complete screening of the IL4 gene: novel polymorphisms and their association with asthma and IgE in childhood

BACKGROUND

IL-4, a cytokine with immunomodulatory functions, is involved in the upregulation of IgE production characteristic of asthma and allergy. Thus far, 2 single nucleotide polymorphisms (SNPs) in the promoter (C-589T) and 5' untranslated region (C-33T) of the IL4 gene have been identified. Polymorphism C-589T was reported to influence total serum IgE levels and bronchial hyperresponsiveness. However, no study has investigated the putative existence of further SNPs in exons, introns, and flanking regions of the IL4 gene.

OBJECTIVE

A complete screening of the IL4 gene and its flanking regions for new polymorphisms was performed. Large-scale association studies in 1120 German schoolchildren were conducted to determine the effect of all polymorphisms present in the IL4 gene on the phenotypic expression of atopic diseases.

METHODS

Denaturing HPLC and standard sequencing techniques were performed to detect novel polymorphisms in 33 unrelated subjects unselected for atopic diseases. Linkage disequilibrium was assessed for all polymorphisms in the IL4 gene, and association studies were performed.

RESULTS

A total of 16 polymorphisms were identified in the IL4 gene, 14 of which were not reported previously. The pattern of linkage disequilibrium observed in IL4 could not be explained by physical distance. A significant association between a cluster of polymorphisms in strong linkage disequilibrium with each other and a physician's diagnosis of asthma and total serum IgE levels was found.

CONCLUSION

These results indicate a possible involvement of SNPs in the IL4 gene in the development of asthma and the regulation of total serum IgE.

Stretch-induced IL-8 depends on c-Jun NH2-terminal and nuclear factor-kappaB-inducing kinases

Positive pressure ventilation with large tidal volumes has been shown to cause release of cytokines, including interleukin (IL)-8. The mechanisms regulating lung stretch-induced cytokine production are unclear. We hypothesized that stretch-induced IL-8 production is dependent on the activation of the mitogen-activated protein kinases, c-Jun NH2-terminal kinases (JNK), p38, and/or extracellular signal-regulated kinase (ERK) 1/2. We exposed A549 cells, a type II-like alveolar epithelial cell line, to cyclic stretch at 20 cycles/min for 5 min-2 h. Cyclic stretch induced IL-8 protein production, IL-8 mRNA expression, and JNK activation, but only transient activation of p38 and ERK1/2. Inhibition of stretch-induced JNK activation by adenovirus-mediated gene transfer of stress-activated protein kinase (SEK-1), a dominant-negative mutant of SEK-1, the immediate upstream activator of the JNKs, and pharmacological JNK inhibitor II SP-600125 blocked IL-8 mRNA expression and attenuated IL-8 production. Inhibition of p38 and ERK1/2 did not affect stretch-induced IL-8 production. Stretch-induced activation NF-kappaB and activator protein (AP)-1 was blocked by NF-kappaB inhibitor and JNK inhibitor, respectively. An NF-IL-6 site was not essential for cyclic stretch-induced IL-8 promoter activity. Stretch also induced NF-kappaB-inducing kinase (NIK) activation, and inhibition of NF-kappaB attenuated IL-8 mRNA expression and IL-8 production. We conclude that stretch-induced transcriptional regulation of IL-8 mRNA and IL-8 production was via activation of AP-1 and NF-kappaB and was dependent on JNK and NIK activation, respectively.

Deletion of a coordinate regulator of type 2 cytokine expression in mice

Mechanisms that underlie the patterning of cytokine expression in T helper (T(H)) cell subsets remain incompletely defined. An evolutionarily conserved approximately 400-bp noncoding sequence in the intergenic region between the genes Il4 and Il13, designated conserved noncoding sequence 1 (CNS-1), was deleted in mice. The capacity to develop T(H)2 cells was compromised in vitro and in vivo in the absence of CNS-1. Despite the profound effect in T cells, mast cells from CNS-1(-/-) mice maintained their capacity to produce interleukin 4. A T cell-specific element critical for the optimal expression of type 2 cytokines may represent the evolution of a regulatory sequence exploited by adaptive immunity.

Leukocyte-specific expression of the pp52 (LSP1) promoter is controlled by the cis -acting pp52 silencer and anti-silencer elements

pp52 (LSP1) is a leukocyte-specific phosphoprotein that binds the cytoskeleton and has been implicated in affecting cytoskeletal remodeling in a variety of leukocyte functions, including cell motility and chemotaxis. The expression of pp52 is restricted to leukocytes by a 549 bp tissue-specific promoter. Here, we show that promoter fragments smaller than the 549 bp pp52 promoter have activity in fibroblasts where pp52 is not normally expressed. Specifically, a truncated construct (+1 to -99) functioned as a basal promoter active in leukocytes and fibroblasts. We identified two upstream regions within the 549 bp pp52 promoter responsible for restricting pp52 promoter activity in fibroblasts. These two regions contained a silencer (pp52 NRE) and an anti-silencer (pp52 anti-NRE) with opposing activities controlling pp52 gene expression. The pp52 NRE was active in both leukocytes and fibroblasts while the pp52 anti-NRE was only active in leukocytes, thereby allowing pp52 gene transcription in leukocytes but not in fibroblasts. The pp52 NRE was localized to an 89 bp DNA segment between -324 and -235 in the 549 bp pp52 promoter and functioned as an active silencer element in a position and orientation independent manner. The pp52 anti-NRE was localized to a 33 bp segment between -383 and -350 of the 549 bp pp52 promoter and acted as an anti-silencer element against the pp52 NRE, but lacked any intrinsic enhancing activity on its own. These findings indicate that the tissue specificity of the pp52 promoter is determined by the pp52 anti-NRE anti-silencer which over-rides the general inhibitory activity of the pp52 NRE silencer.

Enhancement of T helper2 response in the absence of interleukin (IL-)6; an inhibition of IL-4-mediated T helper2 cell differentiation by IL-6

Functional roles of interleukin (IL-)6 in T cell response were investigated. Mice deficient in IL-6 and wild mice were immunized with antigens (myelin oligodendrocyte glycoprotein or methylated BSA) and production of IL-4 and interferon (IFN)-gamma by regional lymph nodes was measured. IL-6 deficiency led to an enhancement of IL-4 and an inhibition of IFN-gamma production. Moreover, polyclonal stimulation of spleen T cells from unimmunized IL-6-deficient mice with anti-CD3 plus anti-CD28 antibodies (Abs) demonstrated an enhancement of T helper (Th)(2)responses. The presence of IL-6, however, augmented IL-4 production but it inhibited IFN-gamma expression by spleen T cells in response to polyclonal stimulation and by antigen-primed spleen T cells in response to re-challenge with the antigen. In contrast, the induction of spleen CD4-positive T cells into Th(2)cells in vitro by the anti-CD3 plus IL-4 was completely suppressed by exogenously added IL-6, whereas Th(1)differentiation of T cells by the anti-CD3 plus IL-12 was not inhibited by the presence of IL-6. Thus, these results indicate that IL-6 physiologically could modulate qualitative T cell response and suggest that it augments Th(1)responses partly through its inhibitory capability of IL-4-induced Th(2)differentiation of naive T cells.

Vav synergizes with protein kinase C theta to mediate IL-4 gene expression in response to CD28 costimulation in T cells

The secretion of IL-4, which displays many important immunoregulatory functions, is restricted to cells of the Th2 subtype. In this study, we investigated the early signaling events leading to the activation of IL-4 transcription. Vav, the protein kinase C (PKC) isoform theta, and the adaptor protein SLP76 (SH2-domain-containing leukocyte protein of 76 kDa), induced transcription from the IL-4 promoter. Vav and PKC theta synergistically activated human IL-4 promoter transcription and IL-4 mRNA production and were found to be constitutively associated in vivo. CD3/CD28-induced IL-4 transcription was inhibited upon coexpression of dominant negative forms of Vav, the adaptor proteins LAT (linker for activation of T cells) and SLP76, PKC theta, and components of the pathways leading to the activation of c-Jun N-terminal kinase (mitogen-activated protein kinase kinase 7 (MKK7), mixed lineage kinase 3 (MLK3)) and NF-kappa B (I kappa B kinase alpha and I kappa B kinase beta). The Vav/PKC theta-mediated synergistic activation of IL-4 transcription was not inhibited by cyclosporin A. Three independent experimental approaches revealed that Vav/PKC theta-derived signals selectively target the P1 and positive regulatory element (PRE)-I elements contained within the human IL-4 promoter. Vav/PKC theta strongly activated a luciferase reporter construct controlled by trimerized P1 or PRE-I elements and furthermore stimulated DNA binding of nuclear proteins to the P1 and PRE-I elements. Vav/PKC theta-induced transcription from the IL-4 promoter was almost completely abrogated by mutation of either the P1 or the PRE-I element within the entire IL-4 promoter.

Characterization of a novel negative regulatory element in the human interleukin 4 promoter

Interleukin 4 (IL-4) is a multifunctional cytokine that plays an important role in hematopoiesis, tumor cell growth, and cellular immune responses. Expression of the IL-4 gene is tightly controlled at the level of gene transcription, and many positive regulatory cis-elements have been identified in the proximal IL-4 promoter region. Relatively little is known about factors that downregulate IL-4 transcription. We performed a detailed deletional analysis of the proximal human IL-4 promoter and studied reporter gene activity in transiently transfected Jurkat T lymphoblasts. In this report, we characterize a novel negative regulatory element (termed P2 NRE) that is adjacent to a binding site for nuclear factor of activated T cells. Mutation of P2 NRE significantly enhanced the activity of a 175 base pair IL-4 promoter construct in transiently transfected Jurkat T lymphoblasts. Using nuclear extracts from Jurkat cells, we identify a candidate factor (termed Rep-1) that binds uniquely to the P2 NRE in DNA-binding assays. Rep-1 is not related to other factors previously shown to interact with the IL-4 promoter, and by UV cross-linking and SDS-PAGE analysis, we found that it migrates with a molecular mass of approximately 150 kDa. Characterizing the molecular mechanisms responsible for downregulating the IL-4 promoter should enhance our understanding of IL-4-gene dysregulation in disease states.

Gene expressions of lipopolysaccharide receptors, toll-like receptors 2 and 4, are differently regulated in mouse T lymphocytes

Toll-like receptors (TLRs) are a family of mammalian proteins homologous to Drosophila Toll. Human TLR2 was shown to mediate the responsiveness to lipopolysaccharide (LPS). On the other hand, gene mutations of mouse TLR4 (mTLR4) in LPS-hyporesponsive strains have suggested that mTLR4 is essential for LPS-signaling in mice, but the role of mTLR2 has not been explored. This report describes molecular cloning of the mTLR2 cDNA. Overexpression of mTLR2 and mouse CD14 conferred LPS-inducibility of c-Jun N-terminal kinase phosphorylation and nuclear factor-κB activation to COS7 cells, suggesting that mTLR2 is a signaling receptor for LPS. BothmTLR2 and mTLR4 genes were expressed in T cells. Treatment with anti-CD3ɛ, PMA plus ionomycin, or interleukin-2 (IL-2)/IL-15 increased mTLR2 but not mTLR4 messenger RNA (mRNA) in some T cell lines. Specific inhibitors of mitogen-activated extracellular signal-regulated kinase and fusion protein 38 (p38) kinase inhibited mTLR2 mRNA up-regulation by PMA plus ionomycin. This suggests that extracellular signal-regulated kinase and p38 kinase pathways were involved. Additionally, LPS treatment of EL-4 cell line decreasedIL-4 gene expression. Our results indicate that both mTLR2 and mTLR4 are involved in LPS signaling, but their expressions are regulated differently in T cells, and that LPS may directly affect T-cell functions by binding to TLRs.

Role of nuclear factor of activated T cells (NFAT) in the expression of interleukin-5 and other cytokines involved in the regulation of hemopoetic cells

NFAT (nuclear factor of activated T cells) is a transcription factor that plays a role in the regulation of various cytokines, including those involved in the regulation of hemopoetic cells such as granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-4 (IL4), interleukin-3 (IL3), interleukin-13 (IL13) and interleukin-5 (IL5). In this report we provide a summary of the various locations in the promoters of each of these cytokines where NFAT has been shown or suggested to bind, and at which sites NFAT has been shown to be involved in transcriptional regulation. We also provide experimental data to show that the binding of NFAT to the nucleotides GAA at positions -113 to -111 of the human IL5 promoter is associated with functional activity in human T cells.

T Cell Priming Enhances IL-4 Gene Expression by Increasing Nuclear Factor of Activated T Cells

The repetitive activation of T cells (priming) enhances the expression of many cytokines, such as IL-4, but not others, such as IL-2. Molecular mechanisms underlying selective expression of cytokines by T cells remain poorly understood. Here we show that priming of CD4 T cells selectively enhances IL-4 expression relative to IL-2 expression by a transcriptional mechanism involving nuclear factor of activated T cells (NFAT) proteins. As detected by in vivo footprinting, priming markedly increases the activation-dependent engagement of the P0 and P1 NFAT-binding elements of the IL-4 promoter. Moreover, each proximal P element is essential for optimal IL-4 promoter activity. Activated primed CD4 T cells contain more NFAT1 and support greater NFAT-directed transcription than unprimed CD4 T cells, while activator protein 1 binding and activator protein 1-mediated transcription by both cell types is similar. Increased expression of wild-type NFAT1 substantially increases IL-4 promoter activity in unprimed CD4 T cells, suggesting NFAT1 may be limiting for IL-4 gene expression in this cell type. Furthermore, a truncated form of NFAT1 acts as a dominant-negative, reducing IL-4 promoter activity in primed CD4 T cells and confirming the importance of endogenous NFAT to increased IL-4 gene expression by effector T cells. NFAT1 appears to be the major NFAT family member responsible for the initial increased expression of IL-4 by primed CD4 T cells.

Regulation of IL-4 expression by the transcription factor JunB during T helper cell differentiation

The molecular basis for restricted cytokine expression by T helper 1 (Th1) and T helper 2 (Th2) cells is unclear. Previous studies found that P1, an element of the interleukin 4 (IL-4) promoter that binds AP-1, is important for Th2-restricted IL-4 expression. Here we show that JunB, but not the other Jun family members, was selectively induced in Th2 cells and not in Th1 cells during differentiation. JunB has previously been considered to be a negative regulator of transcription. However, we show that JunB binds directly to the P1 site and synergizes with c-Maf to activate an IL-4 luciferase reporter gene. JunB-control of IL-4 expression is mediated by the phosphorylation of JunB at Thr102 and -104 by JNK MAP kinase. The synergy between c-Maf and JunB can be attributed to cooperative DNA binding, which is facilitated by JunB phosphorylation. In transgenic mice, elevated JunB levels caused increased expression of several Th2 cytokines in developing Th1 cells. JunB also upregulated IL-4 expression in response to immunization. Thus, the early increase of JunB protein in Th2 cells can provide the specificity for c-Maf in IL-4 expression during T cell development and directs thereby Th2 differentiation.

Cutting Edge: GATA-3-Dependent Enhancer Activity in IL-4 Gene Regulation

Previously, we analyzed the proximal IL-4 promoter in directing Th2-specific activity. An 800-base pair proximal promoter conferred some Th2-selective expression in transgenic mice. However, this region directed extremely low reporter mRNA levels relative to endogenous IL-4 mRNA, suggesting that full gene activity requires additional enhancer elements. Here, we analyzed large genomic IL-4 regions for enhancer activity and interaction with transcription factors. The proximal IL-4 promoter is only moderately augmented by GATA-3, but certain genomic regions significantly enhanced GATA-3 promoter transactivation. Some enhancing regions contained consensus GATA sites that bound Th2-specific complexes. However, retroviral transduction of GATA-3 into developing T cells induced IL-5 to full Th2 levels, but only partially restored IL-4 production. Thus, we propose that GATA-3 is permissive, but not sufficient, for full IL-4 enhancement and may act through GATA elements surrounding the IL-13/IL-4 gene locus.

Th2-Specific Protein/DNA Interactions at the Proximal Nuclear Factor-AT Site Contribute to the Functional Activity of the Human IL-4 Promoter

IL-4 is a pleiotropic immunoregulatory cytokine secreted by activated Th2, but not Th1, cells. The proximal IL-4 promoter contains MARE, C/EBP, P0, octamer-like, P1, and activating protein-1 elements. The half c-Maf binding site (MARE), P0, and P1 sites were previously shown to be involved in Th2-specific transcriptional activity. Except the MARE and P1 site, the molecular basis for Th2 specificity of the P0 site has not been analyzed. Here, we provide the first detailed analysis of the P0 binding factors and show that in Th2, but not in Th1, cells, NF-AT and proteins of the activating protein-1 family are involved in cooperative binding to the P0 and the adjacent octamer-like site. In the mouse Th2 D10 cells, Oct-1/Oct-2 are also found to participate in formation of the P0-binding complexes. Mutation, deletion, and methylation interference analysis demonstrate that both the P0 and the octamer-like sequence are required for inducible binding. Furthermore, we provide the first report of the functional relevance of each site in the human IL-4 promoter by mutagenesis/transfection analysis and demonstrate that the octamer-like, P0 and P1 sites are important for the biologic function of the IL-4 promoter. The MARE site, although it was shown to be critical for the function of the murine IL-4 promoter, does not appear essential for human IL-4 promoter activity in Jurkat T cells. These findings suggest that besides c-Maf, another Th2-specific factor(s) may be involved in tissue-specific expression of the IL-4 gene.

Transient transfection of primary T helper cells by particle-mediated gene transfer

The study of the molecular basis of normal CD4+ T cell function, such as the control of commitment to the TH1 or TH2 phenotypes has been difficult due to the resistance of these cells to transfection by conventional methods. We used antibodies specific to T cell surface molecules to immobilize these cells and optimized conditions for transiently transfecting them by means of particle-mediated gene transfer. Using this technique, a construct encompassing - 577 to +1 of the IL-4 promoter allowed transcription of a luciferase reporter gene in recently-differentiated TH2 cells stimulated by anti-CD3, consistent with regulation of endogenous IL-4 gene expression.

Impaired interleukin 4 signaling in T helper type 1 cells

Cluster of differentation (CD)4+ T helper cells (Th)1s fail to produce interleukin (IL)-4. Even if restimulated in the presence of IL-4, a condition that induces IL-4-producing capacity in naive CD4+ T cells, Th1s fail to become IL-4 producers. We report that Th1 cells have a major impairment in IL-4 signaling. When compared to both Th2s and naive T cells, they display a striking diminution in phosphorylation of Stat6. They also show reduced phosphorylation of Janus kinase (JAK)-3 and insulin receptor substrate (IRS)-2 when compared to Th2s. Stat6 and JAK-3 are present in equivalent amounts in Th1s and Th2s, but IRS-2 protein levels are much lower in Th1s than in Th2s. Altered sensitivity to IL-4, the major inducer of the Th2 phenotype, may explain the stability of the Th1 state.

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.

Interaction of NF-kappaB and NFAT with the interferon-gamma promoter

Interferon-gamma (IFN-gamma) is a pleiotropic lymphokine whose production is restricted to activated T cells and NK cells. Along with other cytokines, IFN-gamma gene expression is inhibited by the immunosuppressant cyclosporin A. We have previously identified an intronic enhancer region (C3) of the IFN-gamma gene that binds the NF-kappaB protein c-Rel and that shows partial DNA sequence homology with the cyclosporin A-sensitive NFAT binding site and the 3'-half of the NF-kappaB consensus site. Sequence analysis of the IFN-gamma promoter revealed the presence of two additional C3-related elements (C3-1P and C3-3P). In addition, an NF-kappaB site (IFN-gamma kappaB) was identified within the promoter region. Based on this observation, we have analyzed the potential role of NF-kappaB and NFAT family members in regulating IFN-gamma transcription. Electrophoretic mobility shift assay analysis demonstrated that after T cell activation, the p50 and p65 NF-kappaB subunits bind specifically to the newly identified IFN-gamma kappaB and C3-related sites. In addition, we identified the NFAT proteins as a component of the inducible complexes that bind to the C3-3P site. Site-directed mutagenesis and transfection studies demonstrate that calcineurin-inducible transcriptional factors enhance the transcriptional activity of the IFN-gamma promoter through the cyclosporin-sensitive C3-3P site, whereas NF-kappaB proteins functionally interact with the C3-related sites. In addition, when located downstream to the beta-galactosidase gene driven by the IFN-gamma promoter, the intronic C3 site worked in concert with both the IFN-gamma kappaB and the C3-3P site to enhance gene transcription. These results demonstrate that the coordinate activities of NFAT and NF-kappaB proteins are involved in the molecular mechanisms controlling IFN-gamma gene transcription.

Transcription factors in immune-mediated disease

A large amount of detailed information about the intracellular proteins regulating NF-kappa B activation and the cellular response to NF-kappa B activation has emerged recently. Several small molecules, an antisense oligonucleotide, and gene therapeutic agents that inhibit NF-kappa b activation have been described. Despite this, there are still significant gaps in our understanding of this process and its consequences. In contrast, the characterization of transcription factors selectively regulating cytokine production by CD4+ T cell subsets is at a very early stage. Three interacting proteins have recently been shown to contribute to subset-restricted expression of the IL-4 gene. There are other elements regulating IL-4 gene expression, however, and the relative importance of these recently identified proteins has yet to be determined.

Characterization of constitutive and inducible transcription factors binding to the P2 NF-AT site in the human interleukin-4 promoter

Interleukin-4 (IL-4) is a pleiotropic immunomodulatory cytokine secreted by T helper 2 cells. The IL-4 promoter contains multiple sites with DNA sequences homologous to the IL-2 NF-AT binding site. One of these sites--the P2 site--located between -173 and -150 was previously found to be flanked by two octamer-like motifs. NF-ATp/c and octamer proteins were suggested to bind to this region and to cooperatively activate the promoter activity (Chuvpilo et al., 1993). To precisely analyze the P2-binding factors we used antibodies against NF-ATp, NF-ATc, Fos, Jun, Oct-1 and Oct-2 in EMSA. We show here that nuclear extracts from T-cells form two P2-binding complexes--a PMA/ionomycin-inducible and a constitutive one. The PMA/ionomycin-inducible complex contains NF-ATp/c, Fos and Jun. No octamer binding factors could be detected in either of the two complexes. Analysis of the precise DNA contact points of the two complexes showed that both complexes are formed in the center of the NF-AT consensus site. No DNA contact points could be detected in the octamer-like motif site. Furthermore, purified recombinant POU domains of Oct-1 and Oct-2 failed to bind to the P2 site, suggesting that this site is not an independent octamer-binding site. Therefore, the DNA sequence at -173 to -150 of the IL-4 promoter is a binding site for NF-ATp/c and AP-1. Octamer proteins are unlikely to cooperate with NF-ATp/c at this site.

Transcription mediated by NFAT is highly inducible in effector CD4+ T helper 2 (Th2) cells but not in Th1 cells

Transcriptional factors of the NFAT family play an important role in regulating the expression of several cytokine genes during the immune response, such as the genes for interleukin 2 (IL-2) and IL-4, among others. Upon antigen stimulation, precursor CD4+ T helper (pTh) cells proliferate and differentiate into two populations of effector cells (eTh1 and eTh2), each one expressing a specific pattern of cytokines that distinguishes them from their precursors. eTh2 cells are the major source of IL-4, while gamma interferon is produced by eTh1 cells. Here we have used reporter transgenic mice to show that DNA binding and transcriptional activities of NFAT are transiently induced during the differentiation of pTh cells into either eTh1 or eTh2 cells to mediate the expression of IL-2 as a common growth factor in both pathways. However, although NFAT DNA binding is similarly induced in both eTh1 and eTh2 cells upon antigen stimulation, only the NFAT complexes present in eTh2 cells are able to mediate high-level transcription, and relatively little NFAT transcriptional activity was induced in eTh1 cells. In contrast to activated pTh cells, neither eTh1 nor eTh2 cells produced significant IL-2 upon stimulation, but the high levels of NFAT transcriptional activities directly correlate with the IL-4 production induced in response to antigen stimulation in eTh2 cells. These data suggest that activated NFAT is involved in the effector function of eTh2 cells and that the failure of eTh1 cells to produce IL-4 in response to an antigen is due, at least partially, to a failure to induce high-level transcription of the IL-4 gene by NFAT. Regulation of NFAT could be therefore a critical element in the polarization to eTh1 or eTh2.

Interleukin (IL)-6 directs the differentiation of IL-4-producing CD4+ T cells

Interleukin (IL)-4 is the most potent factor that causes naive CD4+ T cells to differentiate to the T helper cell (Th) 2 phenotype, while IL-12 and interferon gamma trigger the differentiation of Th1 cells. However, the source of the initial polarizing IL-4 remains unclear. Here, we show that IL-6, probably secreted by antigen-presenting cells, is able to polarize naive CD4+ T cells to effector Th2 cells by inducing the initial production of IL-4 in CD4+ T cells. These results show that the nature of the cytokine (IL-12 or IL-6), which is produced by antigen-presenting cells in response to a particular pathogen, is a key factor in determining the nature of the immune response.

HMG I(Y) interferes with the DNA binding of NF-AT factors and the induction of the interleukin 4 promoter in T cells

HMG I(Y) proteins bind to double-stranded A + T oligonucleotides longer than three base pairs. Such motifs form part of numerous NF-AT-binding sites of lymphokine promoters, including the interleukin 4 (IL-4) promoter. NF-AT factors share short homologous peptide sequences in their DNA-binding domain with NF-kappa B factors and bind to certain NF-kappa B sites. It has been shown that HMG I(Y) proteins enhance NF-kappa B binding to the interferon beta promoter and virus-mediated interferon beta promoter induction. We show that HMG I(Y) proteins exert an opposite effect on the DNA binding of NF-AT factors and the induction of the IL-4 promoter in T lymphocytes. Introduction of mutations into a high-affinity HMG I(Y)-binding site of the IL-4 promoter, which decreased HMG I(Y)-binding to a NF-AT-binding sequence, the Pu-bB (or P) site, distinctly increased the induction of the IL-4 promoter in Jurkat T leukemia cells. High concentrations of HMG I(Y) proteins are able to displace NF-ATp from its binding to the Pu-bB site. High HMG I(Y) concentrations are typical for Jurkat cells and peripheral blood T lymphocytes, whereas E14 T lymphoma cells and certain T helper type 2 cell clones contain relatively low HMG I(Y) concentrations. Our results indicate that HMG I(Y) proteins do not cooperate, but instead compete with NF-AT factors for the binding to DNA even though NF-AT factors share some DNA-binding to DNA even though NF-AT factors share some DNA-binding properties with NF-kB factors. This competition between HMG I(Y) and NF-AT proteins for DNA binding might be due to common contacts with minor groove nucleotides of DNA and may be one mechanism contributing to the selective IL-4 expression in certain T lymphocyte populations, such as T helper type 2 cells.

The proto-oncogene c-maf is responsible for tissue-specific expression of interleukin-4

The molecular basis for the distinctive cytokine expression of CD4+ T helper 1 (Th1) and T helper 2 (Th2) subsets remains elusive. Here, we report that the proto-oncogene c-maf, a basic region/leucine zipper transcription factor, controls tissue-specific expression of IL-4. c-Maf is expressed in Th2 but not Th1 clones and is induced during normal precursor cell differentiation along a Th2 but not Th1 lineage. c-Maf binds to a c-Maf response element (MARE) in the proximal IL-4 promoter adjacent to a site footprinted by extracts from Th2 but not Th1 clones. Ectopic expression of c-Maf transactivates the IL-4 promoter in Th1 cells, B cells, and nonlymphoid cells, a function that maps to the MARE and Th2-specific footprint. Furthermore, c-Maf acts in synergy with the nuclear factor of activated T cells (NF-ATp) to initiate endogeneous IL-4 production by B cells. Manipulation of c-Maf may alter Th subset ratios in human disease.

Abnormal IL-4 gene expression by atopic dermatitis T lymphocytes is reflected in altered nuclear protein interactions with IL-4 transcriptional regulatory element

Among the atopic disease, atopic dermatitis is characterized by the highest levels of serum IgE and by increased peripheral blood T-cell interleukin-4 (IL-4) production. IL-4 promotes IgE synthesis by B cells and stimulates the growth of IL-4-producing T cells and may contribute to the pathogenesis of this disease. In this study, in situ hybridization established that atopic dermatitis patients have a higher frequency of IL-4-producing peripheral blood T cell when compared to normal subjects. These in vivo-derived T cells were used to examine the signaling requirements of IL-4 production and the nuclear factors that associate with a critical IL-4 transcriptional regulatory element between -88 and -60 relative to the IL-4 transcription initiation site, the activation responsive element. We demonstrate that, as in T-cell lines, proteins belonging to the NF-AT and AP-1 family of transcription factors are present in stimulated cell extracts and specifically associate with the activation responsive element. Dysregulated IL-4 production is reflected in the nuclear proteins that associated this element. Using gel shift assays, we found that 12 of 12 nuclear extracts from stimulated atopic T cells formed the activation-dependent protein-DNA complex, compared to only 2 of 12 normal T-cell extracts. Activation complex formation correlated with the relative level of IL-4 mRNA and protein produced in stimulated T cells, suggesting that abnormal IL-4 gene expression in atopic disease may be linked to alterations in nuclear protein interactions with these promoter elements.

Identification of a calcium-inducible, cyclosporine sensitive element in the IFN-gamma promoter that is a potential NFAT binding site

Cyclosporine (CsA) inhibits cytokine transcription by preventing the activation of key promoter sites, in particular the binding of nuclear factor of activated T cells (NFAT) to the IL-2 NFAT site and the "P" site in IL-4. To identify potential NFAT-like sites in the IFN-gamma promoter, we sought areas of homology with the known sites in other promoters. In the promoter region of the mouse and human IFN-gamma gene, we identified two repeats of a consensus sequence ATTTCCnnT, designated P1 and P2 because of their homology to the calcium-inducible and CsA-sensitive "P" sequences in the IL-4 promoter. In electrophoretic mobility shift assay (EMSA), a probe containing the second P sequence "P2" in the human IFN-gamma gene bound nuclear proteins from stimulated, but not unstimulated, humans T cells. The cytosol of unstimulated cells contained similar binding activity that decreased after stimulation, indicating that this binding activity translocated to the nucleus after stimulation. CsA inhibited nuclear translocation. Competition studies demonstrated that oligomers containing the sequences P1 and P2 in IFN-gamma gene, the NFAT site in the IL-2 gene, and the IL-4 P site competed with the P2 probe for protein binding, whereas an oligomer containing mutations in the P2 site did not. Addition of anti-NFAT antiserum altered protein binding to P2, indicating that the proteins were either identical or related to NFAT. Stimulation of T cells transfected with constructs containing three copies of the P2 sequence enhanced CAT activity in response to ionomycin, and this effect was blocked by CsA. These results suggest that the P2 sequence, and probably the P1 sequence, in the IFN-gamma promoter are NFAT binding sites and contribute to the calcium inducibility and CsA sensitivity of IFN-gamma production.

Nuclear factor of activated T cells is associated with a mast cell interleukin 4 transcription complex

Interleukin 4 (IL-4), an immunoregulatory cytokine, is produced only by a subset of activated T cells and cells of the mast cell-basophil lineage. The production of IL-4 by mast cells likely represents a significant source of this protein in local immune-inflammatory responses in the skin, brain, gastrointestinal, and respiratory tracts, in which mast cells are prevalent. In the present study, the cis- and trans-acting elements that control inducible mast cell IL-4 gene transcription were examined and compared with those that function in T cells. We demonstrate that, as in T cells, sequences between bp -87 and -70 are critical for protein association and activation-dependent gene transcription and that this region (termed the activation-responsive element region) is the target of an inducible, cyclosporin A-sensitive, DNA-protein interaction. When assessed by electrophoretic mobility shift assays and UV cross-linking analyses, multiple proteins in both T- and mast cell nuclear extracts associate with the activation-responsive element in vitro, and some of these appear identical. However, distinct proteins are associated with each of the complexes as well. AP-1 family members are unique to the T-cell-stimulation-dependent complex, whereas mast cell complexes contain factors that are reactive with anti-nuclear factor of activated T cells p (NF-ATp) and anti-NF-ATc antibodies but have distinct molecular masses compared with those of T-cell-derived NF-AT. Furthermore, an anti-NF-ATp-reactive factor with a molecular mass of approximately 41 kDa is present in the nuclei of unstimulated cells and binds independently of cell activation, unlike the previously described NF-AT family members. These data support the idea that there are uniquely regulated, cell lineage-specific transcription factors related to T-cell-derived NF-AT that mediate inducible IL-4 transcription in mast cells. These differences likely reflect the distinct cell surface signaling requirements for IL-4 production in T and mast cells.

Transcription of the murine interleukin 5 gene is regulated by multiple promoter elements

Cis-acting regions in the 5'-flank of the mouse interleukin 5 (IL-5) gene involved in the specific and inducible regulation of IL-5 transcription in an untransformed mouse T cell clone, D10.G4.1, have been identified. Transient transfection assays with a series of deletion IL-5 promoter reporter constructs indicate that multiple regulatory elements in the 5'-flanking region of the IL-5 promoter play a role in regulating IL-5 transcription in Th2 cells. Negatively acting elements, NRE I and NRE II, map to the regions between positions -431 and -392 and positions -300 and -261. A positive regulatory element has been mapped to the region between positions -224 and -81. The activity of these elements is dependent on activation of the cells. A 40-bp sequence within this region, termed the IL-5 PRE, has been shown to bind at least two specific nuclear protein complexes from unstimulated and stimulated D10.G4.1 cells. An additional protein complex specific for this site has been identified in nuclear fractions from cells stimulated in the presence of the protein synthesis inhibitor, cycloheximide. Proteins that bind to these elements are likely to be important inducible and specific factors essential for control of IL-5 transcription in response to T cell receptor-mediated signaling events.

Definition of cis-regulatory elements of the mouse interleukin-5 gene promoter. Involvement of nuclear factor of activated T cell-related factors in interleukin-5 expression

We have previously reported that the promoter region of the mouse interleukin-5 (IL-5) gene, extending from a nucleotide position about -1,200 to +33 relative to the transcription initiation site, can mediate transcriptional stimulation by phorbol 12-myristate 13-acetate and dibutyryl cAMP (Bt2cAMP) in mouse thymoma EL-4 cells. Here, we describe identification of four cis-regulatory elements necessary for full activity of the IL-5 promoter, using deletion and mutation analyses. We designated these elements as IL-5A (-948 approximately -933), IL-5P (-117 approximately -92), IL-5C (-74 approximately -56), and IL-5CLE0 (-55 approximately -38). We found that IL-5P bears homology to the binding site for the nuclear factor of activated T cells (NF-AT) and interacted with protein factors in nuclear extracts prepared from EL-4 cells stimulated with phorbol 12-myristate 13-acetate and Bt2cAMP (designated NFIL-5P). NFIL-5P complex was inhibited in the presence of an excess NF-AT and AP1 oligonucleotides and super-shifted by antisera raised against NF-ATp, c-Fos, and c-Jun. It thus seems likely that an NF-AT-related factor is involved in the regulation of IL-5 gene transcription.