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Molecular and Cellular Biology, December 1998, p. 7157-7165, Vol. 18, No. 12
Molecular Immunology, Robert Koch-Institute,
D-13353 Berlin, Germany
Received 17 June 1998/Returned for modification 12 August
1998/Accepted 9 September 1998
Cyclosporin A (CsA) mainly exerts its immunosuppressive action by
selectively inhibiting Ca2+/calcineurin-dependent gene
transcription in lymphoid cells. A model explaining the tissue-specific
effect of this drug on gene expression has not been established to
date, since none of the known intracellular targets of CsA (e.g.,
cyclophilins, calcineurin, and NF-AT) is lymphoid cell specific. To
investigate this issue, we performed a detailed comparative analysis of
the promoter regulating the two-signal-dependent (Ca2+
ionophore plus phorbol myristate acetate [PMA]), CsA-sensitive expression of EGR3 in T cells and the one-signal-dependent (PMA), CsA-insensitive expression of EGR3 in fibroblasts. As a result, we
identified a 27-bp promoter element functionally interacting with
transcription factors NF-ATp and NF-ATc that is crucial for the
CsA-sensitive expression of the EGR3 gene in T cells. In contrast, the
same element was without function in fibroblasts, and other, CsA-insensitive promoter regions were found to be responsible for EGR3
gene expression in these cells. The inactivity of the 27-bp element in
fibroblasts was apparently due to insufficient expression levels of
NF-ATp, since overexpression of NF-ATp, but not NF-ATc, restored the
two-signal phenotype and CsA sensitivity of EGR3 promoter induction in
these cells. The differential usage of an NF-AT binding site explains
the selective effect of CsA on EGR3 gene expression in T cells versus
fibroblasts and may represent one of the basic mechanisms underlying
the tissue specificity of CsA.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Utilization of an NF-ATp Binding Promoter Element
for EGR3 Expression in T Cells but Not Fibroblasts Provides a
Molecular Model for the Lymphoid Cell-Specific Effect of
Cyclosporin A
*
Corresponding author. Mailing address: Molecular
Immunology, Robert Koch-Institute, Nordufer 20, D-13353 Berlin,
Germany. Phone: 49-30-4547-2400. Fax: 49-30-4547-2603. E-mail:
magesh{at}rki.de.
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