Analysis of the promoter elements necessary for IL-4 and anti-CD40 antibody induction of murine Fc epsilon RII (CD23): comparison with the germline epsilon promoter

IL-4 and CD40 ligand stimulate transcription of CD23 (Fc epsilonRII) in B cells and are necessary for the expression of germline epsilon mRNA and production of IgE. Because in vivo studies have shown that the Fc epsilonRII is involved in the regulation of IgE, a study was initiated to compare how IL-4 and engagement of CD40 up-regulate the Fc epsilonRII and epsilon genes. Herein, we describe the preparation of a series of linker-scanning mutants that cover the IL-4 response region in the murine Fc epsilonRII promoter, and their function when transfected into M12.4.5 and M12.4.1 B lymphoma cell lines. Several discrete elements were found to be necessary for IL-4 induction of the Fc epsilonRII gene, some of which have homology with the binding sites of known transcription factors, including NF-IL-4 and NF-kappaB. In contrast, the response element for anti-CD40 (plus IL-4) mapped to a single discrete sequence, a NF-kappaB-like site. Aligning the Fc epsilonRII and germline epsilon promoters in the region that is highly conserved between the human and mouse homologues of both genes reveals a high degree of identity, particularly within discrete clusters. Comparing the function of linker-scanning mutants of the Fc epsilonRII promoter with a similar report for germline epsilon shows that both genes require at least two homologous and similarly located DNA elements in their promoters for a full IL-4 induction. Moreover, the similar response of Fc epsilonRII and epsilon promoter-driven chloramphenicol acetyl transferase plasmids to several cytokines and other agents suggests that the two proximal promoter regions are activated by a similar cassette of factors.