THE DOWN-REGULATED IN ADENOMA (DRA) GENE ENCODES AN INTESTINE-SPECIFIC MEMBRANE GLYCOPROTEIN

The protein product of the DRA gene, a gene whose expression is down-r egulated in colon adenomas and adenocarcinomas, is a membrane glycopro tein and a member of a family of sulfate transporters. It is expressed in the intestinal tract (duodenum, ileum, cecum, distal colon), but n ot in the esophagus or stomach, DRA mRNA expression is restricted to t he mucosal epithelium, and DRA protein expression is further limited t o the columnar epithelial cells, particularly to the brush border, Con sistent with its expression in the differentiated columnar epithelium of the adult human colon, DRA is first expressed in the midgut of deve loping mouse embryos at day 16.5, corresponding with the time of diffe rentiation of the epithelium of the small intestine, A model for the s tructure of the DRA protein is proposed and its possible role in colon tumorigenesis is discussed.