MOLECULAR MECHANISM OF TRANSCRIPTIONAL ACTIVATION OF ANGIOTENSINOGEN GENE BY PROXIMAL PROMOTER

Angiotensinogen is shown to be produced by the liver and the hepatoma cell line HepG2. As a first step for understanding the molecular relat ionship between the transcriptional regulation of the angiotensinogen gene and the pathogenesis of hypertension, we have analyzed the basal promoter of the angiotensinogen gene. Chloramphenicol acetyltransferas e (CAT) assays with 5'-deleted constructs showed that the proximal pro moter region from -96 to +22 of the transcriptional start site was eno ugh to express HepG2-specific CAT activity. Electrophoretic mobility s hift assay and DNase I footprinting demonstrated that the liver- and H epG2-specific nuclear factor (angiotensinogen gene-activating factor [ AGF2]) and ubiquitous nuclear factor (AGF3) bound to the proximal prom oter element from -96 to -52 (angiotensinogen gene-activating element [AGE2]) and to the core promoter element from -6 to +22 (AGE3), respec tively. The site-directed disruption of either AGE2 or AGE3 decreased CAT expression, and the sequential titration of AGF3 binding by in viv o competition remarkably suppressed HepG2-specific CAT activity. Final ly, the heterologous thymidine kinase promoter assay showed that AGE2 and AGE3 synergistically conferred HepG2-specific CAT expression. Thes e results suggest that the synergistic interplay between AGF2 and AGF3 is important for the angiotensinogen promoter activation.