Identification of two novel palindromic regulatory elements in the murine interleukin-5 promoter

Interleukin-5 has remarkable specificity for the eosinophil lineage. This fact, combined with the biological specificity of eosinophilia suggests tight and independent regulation of IL-5 expression. Here we report two novel palindromic regulatory elements (PRE) which contain positive regulatory motifs (PRM) that control transcription of the murine IL-5 gene. The first element, mPRE1-IL5 (-79 to -90) contains the mPRM1 at positions -87 to -89 which operates as a positive regulatory element with mutation of this motif resulting in a 64% decrease in gene activity. Gene expression was reduced by 67% when a similar mutation was introduced into the mPRM2 (-467 to -469) of mPRE2-IL5 (-459 to -470). Both elements specifically bind proteins from EL4-23 cell nuclear extracts forming constitutive DNA-protein complexes. EMSA experiments utilising mutated mPRE-IL5 oligonucleotides indicate that in both elements, the mPRMs are essential for protein binding.