(Verbatim from the application): Hypertension is a serious health problem for African-American women. The octapeptide, angiotensin-Il, is one of the most potent vasoactive substances and is produced from its precursor molecule, angiotensinogen (AG), by successive proteolytic action of renin and angiotensin converting enzyme. Recent linkage analysis has suggested that AG gene locus is involved in human essential hypertension. Human AG gene contains an AIG polymorphism at -6 and hypertensive patients containing nucleoside A at -6 have increased plasma AG level. In addition, reporter constructs containing AG gene promoter with nucleoside A at -6 have increased promoter activity on transient transfection in RepG2 cells. African-American population has increased frequency of nucleoside A(-6) in their AG gene and this polymorphism may pose a greater risk factor for hypertension in this population. Previous tissue culture and animal studies have shown that estrogen treatment increases AG gene expression. Although, 1.2 Kb promoter of the human AG gene does not contain a palindromic estrogen receptor-binding element (ERE), there is a C/A polymorphism at -20 (located between the TATA box and transcriptional initiation site) in the human AG gene. The presence of nucleoside A at -20 creates a ERE in the human AG gene promoter. Our studies have shown that estrogen receptor-a (ER-a) binds to this sequence when nucleoside A is present at -20. Our transient co-transfection studies have shown that an expression vector containing ER coding region increases the expression of reporter constructs containing human AG gene promoter with nucleoside A at -20. In addition, our studies with genomic DNA have suggested that African-American women with nucleoside A at -20 have increased incidence of hypertension. Based on these observations, our hypothesis is that African-American female subjects containing AG gene with nucleoside A at -6 and at -20 (that creates an ERE) are at double jeopardy and have increased risk of hypertension The human AG gene is primarily expressed in the liver and we have shown that liver enriched transcription factors HNF4 and DBP, and ubiquitous transcription factors SP1 and CREB play important role in liver specific expression of this gene. Recent studies have suggested that co-activator CBP (CREB binding protein) binds to the ligand-binding domain of ER and due to its inherent histone acetylase activity plays an important role in estrogen-induced expression of a gene. CBP also binds to a number of other transcription factors including CREB and HNF4 and these factors may modulate estrogen-induced expression of the human AG gene. On the other hand SP1 co-operatively interacts with ER and increases estrogen induced promoter activity of a number of genes. We therefore propose that CREB, HNF4, and SP1 modulate estrogen-induced expression of the human AG gene when nucleoside A is present at -20. Therefore, in this project we will study: (a) molecular mechanism involved in estrogen induced expression of the human AG gene in liver cells and (b) role of polymorphisms at nucleoside -20 and -6 in the promoter of AG gene in hypertension in African-American women.
