The role of CDP in the negative regulation of CXCL1 gene expression

The CXC chemokine, melanoma growth stimulatory activity/growth-regulated pr otein, CXCL1 is an important modulator of inflammation, wound healing, angi ogenesis, and tumorigenesis, Transcription of CXCL1 is regulated through se veral cia-acting elements including Spl, NF-kappaB, and an element that lie s immediately upstream of the NF-kappaB element, the immediate upstream reg ion (IUR), A transcription element data base search indicated that the IUR element contains a binding site for the transcriptional repressor, human CU T homeodomain protein/CCAAT displacement protein (CDP), It is shown here th at in electrophoretic mobility shift assays, complexes obtained with the IU R oligonucleotide probe are supershifted by anti-CDP antibodies and that a CDP polypeptide containing a high affinity DNA binding domain binds to the sequence GGGATCGATC in the IUR element. In Southwestern blot analyses, olig onucleotides containing the wild-type IUR sequence, but not a mutant oligon ucleotide with substitutions in the GGGATCGATC sequence, bind a 170-180-kDa protein. Furthermore, overexpression of the CDP protein blocks CXCL1 promo ter activity in reporter gene assays, whereas overexpression of an antisens e CDP construct leads to a significant increase in CXCL1 promoter activity. Mutations in the IUR element, which map in the putative CUP-binding site, inhibit the binding of CDP to the IUR element and favor increased transcrip tion from the CXCL1 promoter. Based on these results, we propose that trans criptional regulation of the CXCL1 gene is mediated in part by CDP, which c ould play an important role in inflammatory processes and tumorigenesis.