BUTYRATE ACTIVATES THE WAF1 CIP1 GENE PROMOTER THROUGH SP1 SITES IN AP53-NEGATIVE HUMAN COLON-CANCER CELL-LINE/

Butyrate is a well known colonic luminal short chain fatty acid, which arrests cell growth and induces differentiation in various cell types . We examined the effect of butyrate on the expression of WAF1/Cip1, a potent inhibitor of cyclin-dependent kinases, and its relation to gro wth arrest in a p53-mutated human colon cancer cell line WiDr, Five mi llimolar butyrate completely inhibited the growth of WiDr and caused G (1)-phase arrest. WAF1/Cip1 mRNA was rapidly induced within 3 h by tre atment with 5.0 mM butyrate, and drastic WAF1/Cip1 protein induction w as detected. Using several mutant WAF1/Cip1 promoter fragments, we fou nd that the butyrate responsive elements are two Spl sites at -82 and -69 relative to the transcription start site. We also found that a TAT A element at -46 and two overlapping consensus Spl sites at -60 and -5 5 are essential for the basal promoter activity of WAF1/Cip1. These fi ndings suggest that butyrate arrests the growth of WiDr by activating the WAF1/Cip1 promoter through specific Sp1 sites in a p53-independent fashion.