부산대학교 도서관

Carbonic anhydrase I (CA I ) is an abundant enzyme in colon epithelia. In the gastrointestinal icier. carbonic anhydrase is vital for NaCI resorption. alkalinization of gut contents, and absorption of short-chain fatty acids. The CA/ gene has two promoters, one of which is specifically active in colon epithelia and the other in erythroid cells. We arc investigating the factors that regulate CA/ expression from the colon-specific promoter, Colon -specific deoxyribonuclease I hypersensitive sites (DHS) have been mapped close to the colon transcription initiation site (DHS6c) and in the upstream intron (DHS5c). Using electrophoretic mability-shift assays to search the 650-bp region which contains DHS6c, we have identified sequences that bind a colon-specific factor (COF1 ) and by deletion analysis we have narrowed down the COFI -binding motif to a 17-hp sequence. A comparison of this motif with a protein-binding motif in the sucrase-isomultase gene promoter. competition assays, and antibody studies indicate that COFI is identical in the homeodomain protein Cdx-2. We propose that Cdx-2 plays an important role in the intestine-specific pression of CA /. [ABSTRACT FROM AUTHOR]