Cloning and Characterization of the Human Interleukin-3 (IL-3)/IL-5/ Granulocyte-Macrophage Colony-Stimulating Factor Receptor bc Gene: Regulation by Ets Family Members

Abstract

High-affinity receptors for interleukin-3 (IL-3), IL-5, and granu-locyte- macrophage colony-stimulating factor (GM-CSF) are composed of two distinct subunits, a ligand-specific a chain and a common ß chain (ßc). Whereas the mouse has two homologous ß subunits (ßc and bIL-3), in humans, only a single ß chain is identified. We describe here the isolation and characterization of the gene encoding the human IL-3/IL-5/ GM-CSF receptor ß subunit. The gene spans about 25 kb and is divided into 14 exons, a structure very similar to that of the murine ßc/ßIL-3 genes. Surprisingly, we also found the remnants of a second ßc chain gene directly downstream of ßc. We identified a functional promoter that is active in the myeloid cell lines U937 and HL-60, but not in HeLa cells. The proximal promoter region, located from -103 to +33 bp, contains two GGAA consensus binding sites for members of the Ets family. Single mutation of those sites reduces pro-moter activity by 70% to 90%. The 58 element specifically binds PU.1, whereas the 38 element binds a yet-unidentified protein. These findings, together with the observation that cotransfection of PU.1 and other Ets family members en-hances ßc promoter activity in fibroblasts, reinforce the notion that GGAA elements play an important role in myeloid-specific gene regulation.