A NOVEL A T-RICH ELEMENT MEDIATES ANF GENE-EXPRESSION DURING CARDIAC MYOCYTE HYPERTROPHY/

The induction of the atrial natriuretic factor (ANP) gene during alpha (1)-adrenergic stimulation of neonatal rat ventricular myocytes has se rved as a model for gene expression during cardiac muscle cell hypertr ophy. This study describes and identifies a Single regulatory element that mediates expression of the ANF gene. Deletional mutations were ge nerated in a 639-bp fragment of the ANF promoter that confers alpha(1) -adrenergic inducibility to a luciferase reporter gene in transient tr ansfection assays in ventricular myocytes. The results of gel mobility shift and diethylpyrocarbonate (DEPC) interference studies with nucle ar cardiac cell extracts identified the nucleotide contract points for a novel A/T-rich element (ANF-AT) at positions -582/-575 that partial ly mediates alpha(1)-adrenergic inducibility. Mutations in the ANF-AT element reduced alpha(1)-adrenergic inducibility of an ANF-TK-lucifera se fusion gene in cardiac cells by 35%, but had no effect on expressio n in other muscle and non-muscle cells tested. Gel mobility supershift assays with antibodies directed against the MEF-2 protein, the homeob ox protein MHox, or the zinc finger protein HP-1b, document that these factors are not major components of the endogenous ANF-AT binding act ivity 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 exp ression in cardiac ventricular myocytes. (C) 1997 Academic Press Limit ed.