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FasL promoter activation by IL-2 through SP1 and NFAT but not Egr-2 and Egr-3
1Department of Pathology, Boston University School of Medicine, Boston, USA.
Abstract:
Recently activated peripheral T cells treated with IL-2 for 4 days expressed Fas ligand (FasL)-mediated cytotoxicity. These IL-2-treated T cells had high nuclear expression of SP1 and NFAT, but lacked the Egr-2 and Egr-3 that could be induced by anti-CD3 stimulation and had been implicated in FasL gene activation. A minimal promoter region that responded to IL-2 was identified by transient transfection assays using deletion mutants. The data suggests that the GGGCGGAAA site present in the 5' end of the minimal FasL promoter is critical to IL-2-induced FasL gene activation. The GGGCGGAAA sequence contains an overlapping site used by two transcription factor families, one (GGGCGG) for the SP1 family and the other (GGAAA) for the NFAT family. FasL promoter activity was partially but statistically significantly reduced with constructs mutated at either site. More activity was lost with a construct mutated at both sites. In contrast, mutation at the Egr site had no effect on IL-2-induced FasL promoter activity. Our study identified a new FasL promoter site responding to IL-2-induced SP1 and NFAT factors. Furthermore, the nuclei of IL-2-treated cells express SP1 and NFAT, but not Egr-2 and Egr-3, for FasL gene activation.
Insights
Interleukin-2 (IL-2) treatment of T cells enhances Fas ligand (FasL) expression through SP1 and NFAT transcription factors. This study identifies a key promoter region critical for IL-2-induced FasL gene activation.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Activated peripheral T cells treated with Interleukin-2 (IL-2) exhibit Fas ligand (FasL)-mediated cytotoxicity.
- IL-2 treatment leads to high nuclear expression of SP1 and NFAT transcription factors in T cells.
- Egr-2 and Egr-3, previously implicated in FasL gene activation by anti-CD3 stimulation, were not detected in IL-2-treated cells.
Purpose of the Study:
- To identify the promoter region responsible for IL-2-induced FasL gene activation.
- To elucidate the role of transcription factors SP1, NFAT, Egr-2, and Egr-3 in IL-2-mediated FasL expression.
Main Methods:
- Transient transfection assays using deletion mutants of the FasL promoter.
- Site-directed mutagenesis of specific DNA sequences within the FasL promoter.
- Analysis of nuclear transcription factor expression (SP1, NFAT, Egr-2, Egr-3) in IL-2-treated T cells.
Main Results:
- A minimal promoter region responsive to IL-2 was identified.
- A critical site, GGGCGGAAA, within the FasL promoter was found to be essential for IL-2-induced activation.
- This site contains overlapping binding sites for SP1 (GGGCGG) and NFAT (GGAAA) transcription factors.
- Mutating either the SP1 or NFAT site reduced FasL promoter activity, with a greater reduction observed when both sites were mutated.
- Mutation of the Egr site had no significant effect on IL-2-induced FasL promoter activity.
Conclusions:
- A novel FasL promoter site regulated by IL-2-induced SP1 and NFAT factors has been identified.
- IL-2 treatment of T cells induces nuclear expression of SP1 and NFAT, which are crucial for FasL gene activation.
- Egr-2 and Egr-3 are not involved in IL-2-induced FasL gene activation in this context.