Two essential regulatory elements in the human interferon gamma promoter confer activation specific expression in T cells.

Abstract

SummaryLike interleukin 2 (IL-2), interferon 'y (IFN-'y) is an early response gene in T cells and both are prototypical T helper cell type 1 (Th-1) lymphokines. Yet IL-2 and IFN-3, production are independently regulated, as demonstrated by their differential expression in certain T cell subsets, suggesting that the regulatory elements in these two genes must differ. To explore this possibility, the 5' flank of the human IFN-q/ gene was analyzed. Expression of IFN-y promoter-driven fl-galactosidase reporter constructs containing 538 bp of 5' flank was similar to that by constructs driven by the IL-2 promoter in activated Jurkat T cells; expression nearly as great was observed with the construct containing only 108 bp of IFN-~/5' flank. These IFN-'y promoter constructs faithfully mirrored expression of the endogenous gene, in that expression required activation both with ionomycin and PMA, was inhibited by cyclosporin A, and was not observed in U937 or THP-1 cells. The region between -108 and -40 bp in the IFN-'y promoter was required for promoter function and contained two elements that are conserved across species. Deletion of 10 bp within either element reduced promoter function by 70%, whereas deletions in nonconserved portions of this region had little effect on promoter function. The distal conserved element (-96 to -80 bp) contained a consensus GATA motif and a potential regulatory motif found in the promoter regions of the GM-CSF and macrophage inflammatory protein (MIP) genes. Factors binding to this element, including GATA-3, were found in Jurkat nuclear extracts by electromobility shift assays and two of the three complexes observed were altered in response to activation. One or both of these motifs are present in the 5' flank of multiple, other lymphokine genes, including IL-3, IL-4, IL-5, and GM-CSF, but neither is present in the promoter of the IL-2 gene. The proximal conserved element (-73 to -48 bp) shares homology with the NFIL-2A element in the IL-2 promoter; these elements compete for binding of factors in Jurkat nuclear extracts, although the NFIL-2A element but not the IFN-3, element binds Oct-1. Factors binding to this element in the IFN-3, gene were present in extracts from resting and activated Jurkat T cells. However, by in vivo footprinting of intact cells, this element was protected from metbylation only with activation. The factors in Jurkat extracts that bound to the proximal and distal conserved elements were not detected in U937 or THP-1 extracts. Notably, the critical regions of the IFN-'y promoter do not contain sequences homologous to the NF-AT or AP-1 sites in the IL-2 promoter. The differences in essential c/s elements in the IFN-3, and IL-2 promoters, and the factors binding thereto, may play an important role in the differential expression of these genes in naive vs. memory T cells and in the relative preservation of IFN-'y as compared to IL-2 gene expression in anergic Th-1 T cell clones.

Reduced Expression of Nuclear Cyclic Adenosine 5′-Monophospate Response Element-Binding Proteins and IFN-γ Promoter Function in Disease Due to an Intracellular Pathogen

“…CREB also contributes to activation of the IL-2 promoter in T cells stimulated with CD28 and mitogen (30). IFN-␥ production is controlled at the transcriptional level, and the distal and proximal elements in the IFN-␥ promoter are essential for activation-specific production of IFN-␥ by T cells (10). CREB proteins bind to the IFN-␥ proximal element, but the resultant effects on transcription of the IFN-␥ gene remain controversial.…”

“…Transcription of the IFN-␥ gene in activated T cells is controlled by essential regulatory regions in the distal (Ϫ96 to Ϫ80 bp) and proximal (Ϫ73 to Ϫ48 bp) portions of the IFN-␥ promoter (10). Binding of specific proteins to these regulatory regions markedly affects IFN-␥ promoter activity (10 -14), and the proximal promoter element mediates the selective expression of IFN-␥ by T cells (12).…”

CD40 Ligand Trimer Enhances the Response of CD8+ T Cells to Mycobacterium tuberculosis

“…The control of IFN-␥ gene expression is complex and is mediated by binding of multiple transcription factors to several regulatory elements in the promoter region. Activationspecific expression of IFN-␥ by T cells is dependent on the proximal (Ϫ73 to Ϫ48 bp) element of the IFN-␥ promoter, the activity of which is controlled by binding of CREB/activating transcription factor (ATF)-1 and AP-1/ATF-2 (31,54). AP-1 is composed of dimers of the Jun and Fos family proteins, and c-Jun is essential for activation-induced transcription of IFN-␥ by T cells in several experimental systems (28,31).…”

Comparative study and expression analysis of the interferon gamma gene locus cytokines in Xenopus tropicalis

“…The predicted T-bet binding site was located closely to the TATA box in the IFN-γ and IL-22 gene while some distance away from the TATA box in IL-26 gene. Interestingly, GATA3, known to be the pivotal TF in regulating Th2 differentiation (Zheng and Flavell 1997) has an 11/14 identity with its chicken counterpart was also found in the IFN-γ (Kaiser et al 1998;Penix et al 1993). …”