3 INDIVIDUAL REGULATORY ELEMENTS OF THE PROMOTER POSITIVELY ACTIVATE THE TRANSCRIPTION OF THE MURINE GENE ENCODING GRANULOCYTE COLONY-STIMULATING FACTOR

At least three regulatory elements GPE1, GPE2 and GPE3 (G-CSF promoter elements) controlling the gene (G-CSF) encoding granulocyte colony-stimulating factor (G-CSF) are indispensable for the constitutive expression of the G-CSF gene in human CHU-2 cells and for its lipopolysaccharide(LPS)-inducible expression in macrophages. The enhancer activities of each regulatory element were examined with or without the SV40 enhancer element placed downstream from the reporter gene. A GPE1 tetramer mediated the constitutive expression in CHU-2 cells, and the LPS-inducible expression in macrophage cell lines, while the GPE2 element was active in CHU-2 and LPS-treated macrophage cell lines only in combination with the SV40 enhancer. A GPE3 tetramer had efficient enhancer activity in CHU-2 cells but not in macrophage cell lines without the SV40 enhancer. In combination with the SV40 enhancer, GPE3 worked as an LPS-inducible enhancer element in macrophage BAM3 cells. Gel retardation assay indicated that the CHU-2 and the macrophage cells contained nuclear factors which specifically bound to each GPE sequence.