Fig. 5. Snail-induced repression of the promoter activities of claudin genes and occludin. Luciferase reporter constructs carrying mouse claudin-3, claudin-4 or claudin-7 promoter were transfected into Eph4 epithelial cells or NIH/3T3 fibroblasts singly or together with the Snail expression vector. In Eph4 cells, the claudin promoters induced a three- to tenfold increase in relative luciferase activity above that observed in NIH/3T3 cells, indicating that the claudin promoters are activated in an epithelium-specific manner (A). When mouse Snail was coexpressed in Eph4 cells, the activities of claudin promoters were remarkably repressed (B), and the repression of claudin-7 promoter was depended on the dose of Snail (C). The Snail mutant lacking its N-terminal SNAG domain showed no repressor activity for the claudin-7 promoter (D). Similarly, luciferase reporter construct carrying human occludin promoter was transfected into human HT29 epithelial cells (or Eph4 cells) singly or together with the Snail expression vector. The human occludin promoter was repressed by Snail in both HT29 cells (E) and Eph4 cells (data not shown). All results correspond to the average of three independent experiments.

Return to article