In vivo regulation of interleukin-2 receptor alpha gene transcription by the coordinated binding of constitutive and inducible factors in human primary T cells.

Abstract

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 approximately 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.

Relief of cyclin A gene transcriptional inhibition during activation of human primary T lymphocytes via CD2 and CD28 adhesion molecules

“…As a control that lymphocytes have already evolved towards proliferation, changes in proteins binding to the NF-kB site present in the promoter of the early gene coding for IL-2Ra was examined on the same DNA preparations (Figure 4). A clear protection was observed as soon as 6 h post costimulation which corresponded to nuclear translocation of NF-kB as detected by gel shift experiments (data not shown) (Algarte et al, 1995).…”

Binding of HMG-I(Y) Imparts Architectural Specificity to a Positioned Nucleosome on the Promoter of the Human Interleukin-2 Receptor α Gene

“…Cooperative binding of disparate transcriptional activators to nucleosomal DNA has been suggested as one solution to this biological problem (1,42). Transcriptional induction of the IL-2R␣ gene, which occurs only in stimulated T lymphocytes, is known to involve the coordinate binding of both constitutive and inducible factors to the gene's promoter (2). Given the present findings, it is appealing to suggest that the initial directional binding of the constitutively expressed architectural factor HMG-I(Y) to the positioned nucleosome on the PRRII enhancer in vivo may facilitate cooperative binding of the lymphoid-myeloid cell-specific transcription factor Elf-1 to this same core particle, thus targeting it for subsequent disruption during in vivo activation of the IL-2R␣ promoter.…”

Growth Inhibition of Multiple Myeloma Cells by a Novel IκB Kinase Inhibitor

“…U266 cells produce IL-6 in an autocrine fashion. Although U266 and BJAB cells are known to have constitutively activated NF-nB (24,25), constitutive activation of NF-nB has not been definitively reported in other cell lines.…”