Constitutive and inducible factors bind to regulatory element 3 in the promoter of the gene encoding mouse granulocyte colony-stimulating factor.

The expression of the mouse gene (G-CSF) encoding granulocyte colony-stimulating factor is controlled by at least three regulatory elements, GPE1, GPE2 and GPE3 (G-CSF promoter elements). A set of 30-mer oligodeoxyribonucleotides (oligos) scanning the GPE3 region (-104 to -51) of the G-CSF promoter was synthesized, and the tetramer of each oligo was inserted upstream from the cat gene with the simian virus 40 enhancer element. By introducing these hybrid genes into human squamous carcinoma CHU-2 and mouse macrophage BAM3 cells, the enhancer core element of the GPE3 was localized to the region from -98 to -79 in the promoter. A nuclear factor which specifically binds to the core element of the GPE3 was constitutively detected in human CHU-2 cells, whereas the expression of a similar, but distinctly different, factor was significantly induced in BAM3 cells by lipopolysaccharide. The results suggest that these nuclear factors play important roles in the constitutive expression of G-CSF in CHU-2 cells and its inducible expression in macrophages.