A REGULATORY ELEMENT IN THE PROMOTER OF THE HUMAN GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR GENE THAT HAS RELATED SEQUENCES IN OTHERT-CELL-EXPRESSED CYTOKINE GENES

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokin e with a broad spectrum of cell differentiating and colony-stimulating activities, It is expressed by several undifferentiated (bone marrow stromal cells, fibroblasts) and fully differentiated (T cells, macroph ages, and endothelial cells) cells. Its expression in T cells is activ ation dependent, We have found a regulatory element in the promoter of the GM-CSF gene which contains two symmetrically nested inverted repe ats (-192 CTTGGAAAGGTTCATTAATGAAAACCCCCAAG -161). In transfection assa ys with the human GM-CSF promoter, this element has a strong positive effect on the expression of a reporter gene by the human T-cell line J urkat J6 upon stimulation with phorbol dibutyrate and ionomycin or ant i-CD3 antibody. This element also acts as an enhancer when inserted in to a minimal promoter vector. In DNA band retardation assays this sequ ence produces six specific bands that involve one or the other of the inverted repeats. We have also shown that a DNA-protein complex can be formed involving both repeats and probably more than one protein. The external inverted repeat contains a core sequence CTTGG...CCAAG, whic h is also present in the promoters of several other T-cell-expressed h uman cytokines (interleukins 4, 5, and 13). The corresponding elements in GM CSF and interleukin 5 promoters compete for the same proteins i n band-retardation assays. The palindromic elements in these genes are larger than the core sequence, suggesting that some of the interactin g proteins may be different for different genes. Considering the stron g positive regulatory effect and their presence in several T-cell-expr essed cytokine genes, these elements may be involved in the coordinate d expression of these cytokines in T-helper cells.