STUDIES ON 17-1A-ANTIGEN GENE-REGULATION IN NONEXPRESSING A549 AND A431 CELLS, AS COMPARED TO EXPRESSING PANCREATIC-CARCINOMA (CAPAN-2) CELLS, REVEAL A COMPLEX MECHANISM OF REPRESSION OF THIS GENE

Elements controlling high expression of the 17-1A antigen gene in panc reatic carcinoma cells (Capan 2) reside within the two regions: proxim al (-193 to +3) and distal (-877 to -518). We demonstrate here that so me factors present in nuclear extracts from nonexpressing cells bind s pecifically to the control elements, important for gene expression. Ou r results suggest that nonexpressing cells may either lack at least on e of the factors necessary for activation or may contain their modifie d forms. A major difference between expressing and nonexpressing cells was found in the region containing core enhancer sequence. Moreover, nonexpressing cells display a complex pattern of DNA-protein interacti ons in this region, suggesting that these cells contain factors acting negatively mainly on the enhancer sequence. Our results however, indi cate that the mechanism of repression is much more complicated than ex pected.