Increased expression of apolipoprotein genes accompanies differentiation in the intestinal cell line Caco-2

We have analyzed determinants of the synthesis and secretion of apolipoproteins including mRNA for apolipoproteins, in the human colon carcinoma cell line Caco-2 during differentiation in continuous culture. Significant increases in both cellular and secreted apolipoprotein A-I were observed early in the differentiation process. Increases in apolipoprotein B were limited to secreted protein and started later in the differentiation process. Levels of mRNA for apolipoproteins A-I, A-IV, B, C-III, and E increased significantly between the time cells reached confluence and 1 week postconfluence. The kinetics of mRNA accumulation were influenced by culture conditions. Nuclear extracts from postconfluent Caco-2 cells contained increased amounts of protein that bound to oligonucleotides containing the control regions of the apolipoprotein A-I and B genes. A competition experiment suggested that this protein recognized the control regions of both genes. We propose to name this protein DRIFT-1 (differentiation-related intestinal factor for transcription 1).