Identification and characterization of a critical CP2-binding element in the human interleukin-4 promoter

Expression of cytokine genes in T cells is thought to result from a complex network of antigen- and mitogen-activated transcriptional regulators. CP2, a factor homologous to Drosophila Elf-1 and previously found to be a criti cal regulator of several viral and cellular genes in response to developmen tal signals, is rapidly activated in T helper (Th) cells in response to mit ogenic stimulation. Here we show that overexpression of CP2 enhances interl eukin (IL)-4 promoter-driven chloramphenicol acetyltransferase expression, while repressing IL-2 promoter activity, in transiently transfected Jurkat cells. A CP2-protected element, partially overlapping the nuclear factor of activated T cell-binding P2 sequence, was required for IL-4 promoter activ ation in CPS-overexpressing Jurkat cells. This CPS-response element is the site of a cooperative interaction between CP2 and an inducible heteromeric co-factor(s). Mutation of conserved nucleotide contacts within the CPa-resp onse element prevented CP2 binding and significantly reduced constitutive a nd induced IL-4 promoter activity. Expression of a CP2 mutant lacking the E lf-l-homology region of the DNA-binding domain inhibited IL-4 promoter acti vity in a dominant negative fashion in transiently transfected Jurkat cells . Moreover, overexpressed CP2 markedly enhanced, while its dominant negativ e mutant consistently suppressed, expression of the endogenous IL-4 gene in the murine Th2 cell line DIG. Taken together, these findings point to CP2 as a critical IL-4 transactivator in Th cells.