Sp1 binding is critical for promoter assembly and activation of the MCP-1 gene by tumor necrosis factor

The monocyte chemoattractant protein-1 gene (MCP-1) is induced by the inflammatory cytokine tumor necrosis factor through the coordinate assembly of an NF-kappa B-dependent distal regulatory region and a proximal region that has been suggested to bind Spl as well as other factors. To provide a genetic correlation for Spl activity in this system, a cell line homozygous for a targeted truncation of the Spl gene was derived and examined. We found that the lack of Spl binding activity resulted in the inability of both the distal and proximal regions to assemble in vivo even though the binding of NF-kappa B to distal region DNA was unaffected in vitro. We also found that Spl and NF-kappa B were the minimal mammalian transcription factors required for efficient activity when transfected into Drosophila Schneider cells. Additionally, Sp3 was able to compensate for Spl in the Drosophila tissue cell system but not in the Sp1(-/-) cell line suggesting that Spl usage is site-specific and is likely to depend on the context of the binding site. Together, these data provide genetic and biochemical proof for Spl in regulating the MCP-I gene.