We have previously shown that colonic epithelial cells are a major site of MIP-3α production in human colon and that enterocyte MIP-3α protein levels are elevated in inflammatory bowel disease. The aim of this study was to determine the molecular mechanisms regulating MIP-3α gene transcription in Caco-2 intestinal epithelial cells. We show that a κB element at nucleotides -82 to -93 of the MIP-3α promoter binds p50/p65 NF-κB heterodimers and is a major regulator of basal and interleukin-1β (IL-1β)-mediated gene activation. Scanning mutagenesis of the MIP-3α 5′-flanking region also identified two additional binding elements: Site X (nucleotides -63 to -69) and Site Y (nucleotides -143 to -154). Site X (CGCCTTC) bound Sp1 and regulated basal MIP-3α gene transcription. Overexpression of Sp1 increased basal luciferase activity, whereas, substitutions in the Sp1 element significantly reduced reporter activity. In contrast, Site Y (AAGCAGGAAGTT) regulated both basal and cytokine-induced gene activation and bound the Ets nuclear factor ESE-1. Substitutions in the Site Y element markedly reduced inducible MIP-3α reporter activity. Conversely, overexpression of ESE-1 significantly up-regulated MIP-3α luciferase levels. Taken together, our findings demonstrate that co-ordinate activation and binding of ESE-1, Sp1, and NF-κB to the MIP-3α promoter is required for maximal gene expression by cytokine-stimulated Caco-2 human intestinal epithelial cells.
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