GROWTH AND GENE-EXPRESSION ARE PREDOMINANTLY CONTROLLED BY DISTINCT REGIONS OF THE HUMAN IL-4 RECEPTOR

IL-4 causes hematopoietic cells to proliferate and express a series of genes, including CD23. We examined whether IL-4-mediated growth, as m easured by 4PS phosphorylation, and gene induction were similarly cont rolled. Studies of M12.4.1 cells expressing human IL-4R truncation mut ants indicated that the region between amino acids 557-657 is necessar y for full gene expression, which correlated with State DNA binding ac tivity. This region was not required for 4PS phosphorylation. Tyrosine -to-phenylalanine mutations in the interval between amino acids 557-65 7 revealed that as long as one tyrosine remained unmutated, CD23 was f ully induced. When all three tyrosines were mutated, the receptor was unable to induce CD23. The results indicate that growth regulation and gene expression are principally controlled by distinct regions of IL- 4R.