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The Na(+)-Ca(2+) exchanger (NCX) regulates intracellular calcium homeostasis. We report on an upstream region of the rat NCX1 multipartite promoter that is active in cardiac myocytes. Although inactive in most non-cardiac cell lines, its activity can be rescued by cotransfection with GATA-4 and -6, but not GATA-5 transcription factors. In transgenic mice and similar to endogenous NCX1 mRNA expression, the upstream promoter region directs uniform beta-galactosidase expression in cardiac myocytes from approximately 7.75dpc. In adult mouse hearts, promoter activity is, however, significantly reduced and heterogeneous, except in the conduction system (sinoatrial and atrioventricular node, atrioventricular bundles). The upstream NCX1 promoter region thus directs appropriate spatial and temporal control of cardiac expression throughout development.

3-Deazaadenosine analogs can function as inhibitors and also as alternative substrates of S-adenosylhomocysteine (AdoHcy) hydrolase. In cells treated with the analogs, AdoHcy invariably accumulates, leading to inhibition of cellular methylation. F9 teratocarcinoma cells, stably transfected with two collagen (IV) promoter-enhancer-CAT constructs and treated with 10 microM 3-deazaadenosine, 3-deaza-(+-)-aristeromycin or 3-deazaneplanocin, showed a strong induction of CAT activities without affecting differentiation. In comparison, the same 3-deaza analogs did not affect the CAT activity in F9 cells transfected with the beta-actin promoter-CAT construct. Furthermore, Northern blot analysis of endogenous mRNA from wild-type F9 cells treated with the 3-deaza nucleosides all showed an induction of the collagen alpha 1(IV) chain mRNA. Thus, the 3-deaza analogs most likely affect DNA methylation because their results are consistent with the previous observation that the integrated collagen alpha 1(IV) promoter-enhancer constructs were activated with 5-azacytidine.