The activity of interleukin-4 receptor alpha-chain promoter is regulated by a GT box element

Interleukin-4 receptor (IL-4R) is the cell surface complex through which interleukin-4 (IL-4) signals exert its critical biological effects. The alpha-chain of IL-4R is responsible for the high affinity binding of IL-4. In this report, is characterized, the 5' untranslated flanking region of murine IL-4Ralpha gene in the Th2 clone D10.G4.1. We have analyzed a DNA fragment spanning from -995 to +84 relative to the transcription start point. Mutagenesis analysis shows that, neither the previously described Stat6 (-395) nor the NFAT (-266) and NFkappaB (+25) sequences localized here, are involved in the IL-4Ralpha promoter activity. Reporter assays demonstrate that maximum transcriptional activity is achieved by the -89 to +84 sequence and this activity is independent of a TATA-like box located at -25. We have identified a GT box located at -45 as the critical element for the IL-4Ralpha promoter activity. Experiments in SL2 cells, which lack endogenous Sp proteins, show that IL-4Ralpha minimal promoter is transactivated by proteins of Sp family.