Characterization of the Mouse Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) Gene Promoter: Nuclear Factors That Interact with an Element Shared by Three Lymphokine Genes—Those for GM-CSF, Interleukin-4 (IL-4), and IL-5

Abstract

The region extending from -40 to -54 of the 5'-flanking region of the mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) gene shows homology to sequences found in the 5'-flanking regions of other cytokine genes, those encoding interleukin-4 (IL-4), IL-5, and granulocyte colony-stimulating factor (G-CSF). This sequence element is referred to as conserved lymphokine element 0 (CLEO). Saturation mutagenesis of the CLEO element indicates that in addition to the previously mapped region between -73 and -91 (CLE2+GC box), the CLEO element is necessary for induction of the mouse GM-CSF gene by phorbol myristate acetate/Ca ionophore (A23187) stimulation in Τ cells. The presence of the CLEO element is necessary to observe stimulation of the transcription activity of the mouse GM-CSF promoter in vitro. Mobility shift assays revealed that this region forms an inducible DNA-protein complex, NF-CLEO, which consists of two complexes of similar mobility, NF-CLEOa and NF-CLEOb. NF-CLEOa and NF-CLEOb recognize the 3' half and 5' half of the CLEO element, respectively, with an overlapping region recognized by both proteins. The recognition sequence of NF-CLEOa corresponds to the region required for induction by phorbol myristate acetate/A23187, while the recognition sequence of NF-CLEOb contains bases that have inhibitory activity. The CLEO elements of the IL-4 and IL-5 genes but not the G-CSF gene are also recognized by NF-CLEOa and -b, suggesting that the NF-CLEOa and -b proteins play an important role in the coordinate induction of these genes in activated Τ cells. The nuclear factor that recognizes the G-CSF CLEO element seems to be different from NF-CLEOa and NF-CLEOb; however, it weakly recognizes the DNA sequence for the NF-CLEOa.