T-cell-specific expression of interleukin 2: evidence for a negative regulatory site.

Abstract

To understand the basis for T-cell-specific induction of interleukin 2 (IL-2), we have analyzed nuclear factors from the Jurkat T-lymphoid leukemia cell, which can be induced to secrete IL-2. We have used an electrophoretic mobility shift assay to examine binding of proteins to the upstream regulatory region, before and after activation with mitogens. We find two types of binding sites. One resembles an inducible enhancer element, but the protein that recognizes it is found in non-T cells and is unlikely to determine T-cellspecific expression of IL-2. A second site negatively regulates expression in resting T cells. A complex that binds to a DNA fragment containing this site is modified only when IL-2 is expressed, and it lies near a specific inducible DNase hypersensitive region. We suggest that negative regulation at this site, mediated by its associated protein(s), may contribute to the cell-specific expression of IL-2.

The interleukin 2 gene is expressed in the syncytiotrophoblast of the human placenta.

“…IL-2 has generally been believed to be an antigen-or mitogen-induced T-lymphocyte-or T-cell line-specific product (34,35). Besides the detection of human placental (syncytiotrophoblastic) IL-2 RNA transcripts reported here and the detection of immunoreactive IL-2 in human syncytiotrophoblast and amnion (27) T-cell IL-2 production is a transient event, triggered by antigen or mitogen stimulation (38)(39)(40).…”

“…2 imity to or within these enhancer-like sequences have been demonstrated (45). Recently, Nabel et al (35), in an effort to determine the mechanism(s) responsible for T-cell-specific IL-2 gene transcription, examined the binding of proteins from nuclear extracts of resting and activated Jurkat cells (and IL-2 nonproducing, non-T cells) to radiolabeled DNA probes derived from the upstream IL-2 genomic regulatory region in electrophoretic mobility shift assays. They identified a site [near one ofthe previously identified T-cell-specific DNase-hypersensitive sites (45)] that negatively regulates IL-2 gene expression in resting T cells.…”

“…Alternatively, these regions of the IL-2 gene may be no different than those described from T cells, and other regulatory regions may be present in the placental gene or its flanking regions. It is also possible that, ifthe placental gene and its regulatory sequences are identical to those of the T cell, the IL-2 gene negative regulation site binding protein complex, identified by Nabel et al (35), that is modified in activated T cells, would only be present in its modified form in placental nuclei. By using placental or, preferably, syncytiotrophoblast nuclear protein extracts in the system of Nabel et al (35), one could address this latter speculation.…”

The Nuclear Factor YY1 Suppresses the Human Gamma Interferon Promoter through Two Mechanisms: Inhibition of AP1 Binding and Activation of a Silencer Element

“…It has been reported that in the cytokine genes, transcriptional initiation is affected by both silencer and enhancer elements (5,10,11,19,23,27,30,33,48). In the IFN-␥ gene, multiple enhancer elements (5)(6)(7)45) and silencer elements (5,49) Further studies demonstrated that this silencer activity is promoter specific and dependent upon the formation of a DNA-AP2-like protein complex (49).…”

EGFR‐targeted Chimeras of Pseudomonas ToxA released into the extracellular milieu by attenuated Salmonella selectively kill tumor cells

“…When the wild type gene for ToxA has been expressed by Escherichia coli , various results have been achieved ranging from no secretion (Gray et al, 1984), periplasmic secretion (Lory et al, 1988) to extracellular secretion using an OmpA signal sequence substituted for that of the ToxA signal sequence (Chaudhary et al, 1988). Among the different chimeric proteins, TGFα-PE40 can be recovered from inclusion bodies, the periplasm, and supernatant when used with the OmpA signal sequence (Kondo et al, 1988), while PE35/TGFαKDEL was only found in inclusion bodies.…”