ABSTRACT
The induction of the atrial natriuretic factor (ANF) gene during alpha 1-adrenergic stimulation of neonatal rat ventricular myocytes has served as a model for gene expression during cardiac muscle cell hypertrophy. This study describes and identifies a single regulatory element that mediates expression of the ANF gene. Deletional mutations were generated in a 639-bp fragment of the ANF promoter that confers alpha 1-adrenergic inducibility to a luciferase reporter gene in transient transfection assays in ventricular myocytes. The results of gel mobility shift and diethylpyrocarbonate (DEPC) interference studies with nuclear cardiac cell extracts identified the nucleotide contract points for a novel A/T-rich element (ANF-AT) at positions -582/-575 that partially mediates alpha 1-adrenergic inducibility. Mutations in the ANF-AT element reduced alpha-adrenergic inducibility of an ANF-TK-luciferase fusion gene in cardiac cells by 35% but had no effect on expression in other muscle and non-muscle cells tested. Gel mobility supershift assays with antibodies directed against the MEF-2 protein, the homeobox protein MHox, or the zinc finger protein HF-1b, document that these factors are not major components of the endogenous ANF-AT binding activity in cardiac muscle cells. The current study provides evidence for a role for a novel A/T-rich element in the regulation of ANF gene expression in cardiac ventricular myocytes.
