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

Association of interleukin-4 promoter polymorphisms in Taiwanese patients with type 2 diabetes mellitus

Many factors have been implicated in the onset of type 2 diabetes mellitus (T2DM). Recently, immune response and inflammation were suggested to play certain roles in the development and complications of T2DM. The aim of this study is to investigate the putative correlation between the promoter polymorphisms of interleukin-4 (IL-4), one of the immune-regulatory type 2 helper T-cell cytokines, and T2DM. Genomic DNA from 425 Taiwanese T2DM patients and 148 nondiabetic control study subjects were extracted, and their IL-4 promoter polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Both of the distribution of IL-4 C-589T (P = .013) and C-34T (P = .05) genotypes were significantly different between T2DM patients and control subjects. Significant association between IL-4 C-589T alleles (P = .002) and T2DM, as well as C-34T alleles and T2DM (P =.024), was also identified. In addition, a statistically significant association between homologous IL-4 -589 C/C genotype and lower circulatory high-density lipoprotein cholesterol levels was observed. Our results suggested that IL-4 promoter polymorphisms are associated with T2DM. A significant association between IL-4 -589 C/C genotype and lower circulatory high-density lipoprotein cholesterol level was observed as well. The above results suggested that IL-4 may participate in lipid metabolism and diabetic susceptibility.

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.

Histone deacetylation inhibits IL4 gene expression in T cells

BACKGROUND

Dysregulated expression of IL-4 has been linked with allergic diseases. IL-4 expression is controlled at the level of gene transcription by the coordinated action of multiple factors that bind regulatory promoter elements. In addition, alterations in chromatin structure are thought to play a role in regulating the expression of cytokines in the T(H)2 gene cluster, although the biochemical basis for these alterations in human T cells is not well understood.

OBJECTIVE

We sought to define the role of histone acetylation in the regulation of IL4 gene expression in human T cells.

METHODS

IL-4 protein production was measured by means of ELISA. IL-4 promoter activity was measured with luciferase-based reporter constructs transiently transfected into Jurkat T cells. The acetylation status of histones associated with the IL4 gene was analyzed with chromatin immunoprecipitation assays.

RESULTS

IL-4 production from activated peripheral blood T cells was enhanced by the histone deacetylase inhibitor trichostatin A. Overexpression of the type 1 histone deacetylases 1, 2, and 3 inhibited transcription driven by the IL-4 promoter in Jurkat T cells, whereas cotransfection of the histone acetyltransferase CREB-binding protein potentiated IL-4 promoter activity. Using chromatin immunoprecipitation assays, we show that nucleosomes in the proximal IL-4 promoter are acetylated on T-cell activation.

CONCLUSION

Our results demonstrate that the acetylation state of histones associated with the IL-4 promoter is a key regulator of IL4 gene expression.

Yin-Yang 1 activates interleukin-4 gene expression in T cells

Interleukin-4 (IL-4) is a multifunctional cytokine that plays an important role in immune and inflammatory responses. Expression of the IL-4 gene is tightly controlled at the level of gene transcription by both positive and negative regulatory elements in the IL-4 promoter. Several constitutive nuclear factors have been identified that can interact with IL-4 promoter elements in DNA binding assays. Here we report that the zinc-finger protein YY-1 (Yin-Yang 1) can bind to multiple elements within the human IL-4 promoter. Cotransfection of Jurkat T cells with different IL-4 promoter/reporter constructs together with expression vectors encoding antisense, wild-type, or zinc finger-deleted mutant YY-1 suggested that YY-1 enhanced IL-4 promoter activity in a DNA-binding domain-dependent manner. Site-directed mutagenesis revealed that a proximal YY-1-binding site, termed Y0 ((-59)TCATTTT(-53)), was essential for YY-1-driven IL-4 promoter activity. In addition, cotransfected YY-1 enhanced both IL-4 promoter activity and endogenous IL-4 gene expression in nontransformed peripheral blood T cells. Thus, YY-1 positively regulates IL-4 gene expression in lymphocytes.

Selective inhibition of interleukin-4 gene expression in human T cells by aspirin

Previous studies indicated that aspirin (acetylsalicylic acid [ASA]) can have profound immunomodulatory effects by regulating cytokine gene expression in several types of cells. This study is the first in which concentrations of ASA in the therapeutic range were found to significantly reduce interleukin (IL)-4 secretion and RNA expression in freshly isolated and mitogen-primed human CD4+ T cells. In contrast, ASA did not affect IL-13, interferon-gamma, and IL-2 expression. ASA inhibited IL-4, but not IL-2, promoter-driven chloramphenicol acetyltransferase expression in transiently transfected Jurkat T cells. The structurally unrelated nonsteroidal anti-inflammatory drugs indomethacin and flurbiprofen did not affect cytokine gene expression in T cells, whereas the weak cyclo-oxygenase inhibitor salicylic acid was at least as effective as ASA in inhibiting IL-4 expression and promoter activity. The inhibitory effect of ASA on IL-4 transcription was not mediated by decreased nuclear expression of the known salicylate target nuclear factor (NF)-kappaB and was accompanied by reduced binding of an inducible factor to an IL-4 promoter region upstream of, but not overlapping, the NF of activated T cells- and NF-kappaB-binding P1 element. It is concluded that anti-inflammatory salicylates, by means of a previously unrecognized mechanism of action, can influence the nature of adaptive immune responses by selectively inhibiting the expression of IL-4, a critical effector of these responses, in CD4+ T cells.

Preferential activation of nuclear factor of activated T cells c correlates with mouse strain susceptibility to allergic responses and interleukin-4 gene expression

Dysregulated expression of the T helper 2 cytokine interleukin (IL)-4 is thought to play a fundamental role in the pathogenesis of allergic asthma. The molecular basis for dysregulated IL-4 production is not well understood. We analyzed in detail the molecular factors involved in regulating IL-4 transcription in a well-characterized mouse model. In this model, A/J mice developed allergen-induced IL-4 cytokine gene expression, airway inflammation, and hyperresponsiveness, whereas C3H/HeJ (C3H) mice did not. Here we report that isolated splenocytes from A/J and C3H mice stimulated ex vivo with concanavalin A reproduced the cytokine phenotype observed in the airway after antigen challenge. We hypothesized that differences in splenocyte IL-4 production involved either polymorphisms in regulatory IL-4 promoter regions, or the expression and activation of transcription factors necessary for promoter transactivation in a strain-dependent manner. To address these questions, we first sequenced ~ 700 base pairs containing well-characterized IL-4 promoter regulatory elements using genomic DNA obtained from C3H and A/J mice. Next, we used electrophoretic mobility shift assays with relevant IL-4 promoter sequences to screen nuclear extracts isolated from A/J and C3H splenocytes for functional transcriptional factor complexes. Here we show that susceptibility to antigen-induced airway hyperresponsiveness is not due to polymorphisms in the IL-4 promoter, but is associated with preferential expression of nuclear factor of activated T cells c in splenocyte nuclear extracts obtained from A/J mice. In conclusion, our data link dysregulated activation of a specific transcription factor with susceptibility to allergic airway inflammation.

Identification and characterization of a critical CP2-binding element in the human interleukin-4 promoter

Expression of cytokine genes in T cells is thought to result from a complex network of antigen- and mitogen-activated transcriptional regulators. CP2, a factor homologous to Drosophila Elf-1 and previously found to be a critical regulator of several viral and cellular genes in response to developmental signals, is rapidly activated in T helper (Th) cells in response to mitogenic stimulation. Here we show that overexpression of CP2 enhances interleukin (IL)-4 promoter-driven chloramphenicol acetyltransferase expression, while repressing IL-2 promoter activity, in transiently transfected Jurkat cells. A CP2-protected element, partially overlapping the nuclear factor of activated T cell-binding P2 sequence, was required for IL-4 promoter activation in CP2-overexpressing Jurkat cells. This CP2-response element is the site of a cooperative interaction between CP2 and an inducible heteromeric co-factor(s). Mutation of conserved nucleotide contacts within the CP2-response element prevented CP2 binding and significantly reduced constitutive and induced IL-4 promoter activity. Expression of a CP2 mutant lacking the Elf-1-homology region of the DNA-binding domain inhibited IL-4 promoter activity in a dominant negative fashion in transiently transfected Jurkat cells. Moreover, overexpressed CP2 markedly enhanced, while its dominant negative mutant consistently suppressed, expression of the endogenous IL-4 gene in the murine Th2 cell line D10. Taken together, these findings point to CP2 as a critical IL-4 transactivator in Th cells.