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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.

Background: Eosinophils are now known to produce a variety of proinflammatory cytokines, although the molecular factors that regulate their production are poorly understood. The expression of almost all of the cytokines produced by eosinophils, including the proallergic cytokine IL-4, is now known to be regulated at the level of transcription by members of the nuclear factor of activated T cells (NFAT) family of transcription factors., Objective: We sought to characterize the expression of different NFAT proteins in resting and activated eosinophils., Methods: Nuclear and whole cell extracts were obtained from both peripheral blood eosinophils and those obtained from bronchoalveolar lavage fluid of asthmatic subjects after endobronchial allergen challenge. NFAT expression was determined by using immunoprecipitation and Western blot analysis, DNA-binding assays, and RT-PCR analysis of eosinophil mRNA., Results: Both peripheral blood and bronchoalveolar lavage fluid eosinophils expressed NFATp and NFATc protein. Unlike activated T cells, which express multiple NFATc isoforms, eosinophils preferentially express the approximately 85-kd isoform. In addition, eosinophils were found to constitutively express NFATc mRNA. A brief incubation with the T(H)2 cytokines IL-4 and IL-5 was sufficient to induce the nuclear translocation of NFATc. Eosinophil nuclear extracts contain multiple factors that can specifically recognize the IL-4 promoter P1 NFAT site in DNA-binding assays, including NFATp., Conclusion: NFATp and NFATc can regulate the expression of cytokines and other genes in eosinophils but appear to be regulated by a novel signal transduction mechanism in these cells.