DEVELOPMENTAL-CHANGES OF GM-CSF GENE INDUCIBILITY IN EMBRYONAL CARCINOMA-CELLS

Murine embryonal carcinoma (EC) P19 cells, a tissue culture model of e arly embryonic development, failed to produce cytokines, such as inter leukin-3 (IL-3), IL-4, granulocyte-macrophage colony stimulating facto r (GM-CSF) and interferon-beta (IFN-beta) at the mRNA level. Different iation induced by retinoic acid (RA) released this repression to produ ce some cytokines. GM-CSF and IFN-P genes were expressed in response t o PMA/A23187, poly(I):poly(C), IL-1 alpha, forskolin, or LPS stimulati on in differentiated P19 cells, whereas IL-3 and IL-4 genes were not e xpressed. To elucidate the mechanism of the GM-CSF gene induction afte r differentiation, we transfected a series of 5' deletion mutants of t he mouse GM-CSF promoter fused to the bacterial CAT gene. The 740-bp f ragment of the 5'-flanking region mediated the positive response. Dele tion analysis revealed that the 5' boundary region of the DNA element required for activation lies between positions -95 and -84 and the reg ion upstream of position -95 appears inhibitory. These results indicat e that the maturation of the transcriptional machinery after different iation results in the activation of the GM-CSF gene.