CONSTITUTIVE BINDING OF THE TRANSCRIPTION FACTOR INTERLEUKIN-2 (IL-2)ENHANCER-BINDING FACTOR TO THE IL-2 PROMOTER

A positive regulatory element in the interleukin-2 (IL-2) promoter, de signated the antigen receptor response element-2, is essential for the induction of IL-2 gene expression upon the binding of an inducible mu ltiprotein complex of proteins known as nuclear factor of activated T cells, In the current study, we demonstrated that the winged helix tra nscription factor IL-2 enhancer binding factor (ILF) is constitutively expressed in both resting and activated Jurkat cells and binds to two adjacent sequence motifs immediately downstream of the binding site f or NFAT. One of these elements has a high degree of homology with cons ensus binding sites for a variety of winged-helix DNA binding proteins , and the second site functions to modulate ILF binding, Mutagenesis o f each of the two sequence elements required for ILF binding decreased IL-2 promoter activity when assayed in transfection assays, Although ILF bound constitutively to the IL-2 promoter, it was not detected as a component of the NFAT complex, These results suggest that important regulatory sequences in the IL-2 promoter are bound by ILF and that th is binding may be involved in the control of IL-2 gene expression.