IL-2R alpha transcription is developmentally restricted to T cells and physiologically dependent on specific stimuli such as antigen recognition. To analyse the mechanisms used to activate IL-2R alpha transcription as well as those used to block it in non-expressing cells, we determined the protein-DNA interactions at the IL-2R alpha locus in three different cell types using the DMS/LMPCR genomic footprinting method. CD25/IL-2R alpha can be efficiently induced in primary human T cells since similar to 100% express this gene when receiving an appropriate combination of mitogenic stimuli. To understand why IL-2R alpha is not expressed in other haematopoietic cell types, we analysed BJAB B lymphoma cells which do not express the IL-2R alpha gene and contain constitutively active nuclear NF-kappa B. Primary fibroblasts from embryo and adult skin were selected to examine the mechanisms that may be used to keep the IL-2R alpha gene inactive in non-haematopoietic cells. The three main results are: (i) the stable in vivo occupancy of IL-2R alpha kappa B element in resting T cells, most probably by constitutive NF kappa B p50 homodimer that could impair SRF binding to the flanking SRE/CArG box; (ii) its inducible occupancy by NF-kappa B p50-p65 associated with the binding of an SRE/CArG box DNA-binding factor upon mitogenic stimulation; and (iii) a correlation between the precommitment of T cells to activation and the presence of stable preassembled protein-DNA complexes in contrast with the bare IL-2R alpha locus in non-T cells.
In-Vivo Regulation of Interleukin-2 Receptor-Alpha Gene-Transcription by the Coordinated Binding of Constitutive and Inducible Factors in Human Primary T-Cells
Algarte, M.; Lecine, P.; Costello, R.; Plet, A.; Olive, D.; Imbert, J.
1995-10-16 / vol 14 / pages 5060-5072
activation; expression; transcription; monoclonal-antibodies; serum response element; nf-kappa-b; chain gene; DNA-binding; lymphocytes-t; cd28 adhesion molecules; il-2r-alpha; ligation-mediated pcr; primary t cells; srf