Caco-2 cells undergo differentiation to an enterocytic-like cell when maintained in a post-confluent state for 1-2 weeks. During this period Caco-2 cells begin to express high levels brush border membrane associated enzymes such as dipeptidyl peptidase IV. Using the dipeptidyl peptidase IV gene promoter in electrophoretic mobility shift assays, we have shown for the first time that levels of hepatocyte nuclear factor 1 alpha increase three- to fourfold during Caco-2 cell differentiation. Transient cotransfection experiments with 3T3 cells using dipeptidyl peptidase IV promoter constructs and expression vectors containing hepatocyte nuclear factor 1 alpha and beta show that the ratio of alpha and beta modulates reporter gene expression. These results suggest that the increase in levels of hepatocyte nuclear factor 1 alpha that occur during intestinal cell differentiation, are important for expression of dipeptidyl peptidase IV and other intestinal proteins.