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Expression of PILOT, a putative transcription factor, requires two signals and is cyclosporin A sensitive in T cells
H W Mages1, T Stamminger, O Rilke
1Max-Planck-Society Research Unit for Immunology/Rheumatology, Erlangen University, Germany.
Abstract:
Few known genes (IL-2, members of the IL-8 family, interferon-gamma) are induced in T cells only through the combined effect of phorbol myristic acetate (PMA) and a Ca(2+)-ionophore, and expression of only these genes can be fully suppressed by Cyclosporin A (CyA). We have identified a putative transcription factor, designated PILOT, with an identical dual signal requirement for expression. Induction of the PILOT gene is detectable in human T cells 20 min following activation in the presence of cycloheximide and is fully suppressed by CyA. The PILOT protein has a calculated M(r) of 42.6 kDa and contains three zinc fingers of the C2H2-type at the carboxyl-terminus which are highly homologous to the zinc finger regions of the transcription factors EGR1, EGR2, and pAT 133. In contrast to T cells, in fibroblasts PILOT gene expression requires only one signal (PMA) and is not affected by CyA. This observation directly demonstrates the existence of a Ca2+ signal-dependent regulatory element obligatory for expression of some genes in T cells but not in fibroblasts. This differential expression model will be valuable in the dissection of the dual signal pathway in T cells and the effects of CyA upon it.
Insights
Researchers discovered PILOT, a transcription factor requiring dual signals for T cell activation, unlike in fibroblasts. This finding aids understanding T cell signaling pathways and Cyclosporin A effects.
Area of Science:
- Molecular Biology
- Immunology
- Gene Regulation
Background:
- Certain genes in T cells require combined phorbol myristic acetate (PMA) and Ca(2+)-ionophore signals for induction.
- Cyclosporin A (CyA) can suppress the expression of these T cell-specific genes.
Purpose of the Study:
- To identify novel transcription factors with dual signal requirements for T cell gene expression.
- To investigate the differential gene regulation mechanisms between T cells and fibroblasts.
Main Methods:
- Human T cells were activated with PMA and Ca(2+)-ionophore in the presence of cycloheximide.
- PILOT gene expression was analyzed under various conditions, including CyA treatment.
- PILOT protein's structural homology to known transcription factors was assessed.
Main Results:
- A new transcription factor, PILOT, was identified, exhibiting dual signal dependency for T cell expression, similar to IL-2 and interferon-gamma.
- PILOT gene induction in T cells was observed within 20 minutes and fully suppressed by CyA.
- In contrast, PILOT expression in fibroblasts required only PMA and was unaffected by CyA.
Conclusions:
- The study demonstrates a Ca(2+) signal-dependent regulatory element essential for specific gene expression in T cells but absent in fibroblasts.
- PILOT serves as a model for dissecting the dual signal pathway in T cells and understanding CyA's regulatory effects.