Characterization of nuclear factors that bind to a critical positive regulatory element of the human granulocyte-macrophage colony- stimulating factor promoter

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor that stimulates the proliferation, maturation, and functional activity of myeloid cells in peripheral blood and bone marrow. Expression of GM-CSF is tightly regulated and is limited to cells stimulated directly (T cells, macrophages) or indirectly (fibroblasts, endothelial cells) by immune challenge. Several studies of the transcriptional control of GM-CSF expression have elucidated a region of the GM-CSF promoter that mediates positive regulatory activity in a number of cell types. This region contains a direct repeat of the sequence CATTA/T that extends from nucleotides -37 to -48 upstream of the start of mRNA synthesis. Although specific DNA:protein interactions have been shown within this region, neither the nature nor the number of nuclear factors responsible for these interactions have been characterized. In this study, we use DNase I footprinting analysis to demonstrate that point mutations, which inactivate the GM-CSF promoter, disrupt DNA:protein interactions within this region. By combined electrophoretic mobility shift and ultraviolet cross-linking analysis, we have detected several protein species that bind specifically to the positive regulatory sequence.