Annexin A1 is a member of a phospholipid and calcium binding family of proteins; it is involved in anti-inflammation and in the regulation of differentiation, proliferation, and apoptosis. Here, we show the existence of a functional binding site for the tumor suppressor p53 near the proximal CCAAT box and the fact that the basal expression of annexin A1 in human colon adenocarcinoma cells is driven by p53 at the transcriptional level. Posttranscriptional mechanisms may also play an important role in maintaining constitutive annexin A1 expression. In addition, a p53/NF-Y complex is detected bound to the p53 binding site on its promoter. Butyrate is a natural product of fiber degradation in the colon and a key regulator of colonic epithelium homeostasis. We show that butyrate, a class I and II histone deacetylase inhibitor, induces transcriptional activation of annexin A1 expression correlated with differentiation. The effect of butyrate is mediated through a release of NF-Y from the proximal CCAAT box and an enhancement of p53 binding. The interaction of p53 with the promoter is dependent on p38 MAPK activity either in the absence or in the presence of butyrate. Further, activation of p38 MAPK by this agent is required to increase annexin A1 promoter activity and to increase protein expression.