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 infla mmatory cytokine tumor necrosis factor through the coordinate assembly of a n 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 genet ic 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 th at the lack of Spl binding activity resulted in the inability of both the d istal and proximal regions to assemble in vivo even though the binding of N F-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 require d for efficient activity when transfected into Drosophila Schneider cells. Additionally, Sp3 was able to compensate for Spl in the Drosophila tissue c ell system but not in the Sp1(-/-) cell line suggesting that Spl usage is s ite-specific and is likely to depend on the context of the binding site. To gether, these data provide genetic and biochemical proof for Spl in regulat ing the MCP-I gene.