Cardiac expression of the Na(+)/Ca(2+) exchanger NCX1 is GATA factor dependent.
The cardiac sarcolemmal Na(+)/Ca(2+) exchanger plays a primary role in Ca(2+) efflux and is important in regulating intracellular Ca(2+) and beat-to-beat contractility. Of the three Na(+)/Ca(2+) exchanger genes cloned (NCX1, NCX2, and NCX3), only NCX1 is expressed in cardiac myocytes. NCX1 has alternative promoters for heart, kidney, and brain tissue-specific transcripts. Analysis of the cardiac NCX1 promoter (at -336 bp) identified a cardiac-specific minimum promoter (at -137) and two GATA sites (at -75 and -145). In this study, gel shift and supershift analyses identified GATA-4 in primary neonatal cardiac myocytes. Site-directed mutagenesis of the GATA-4 site at -75 abolishes binding and reduces activity of the minimum and full-length promoters by >90 and approximately 60%, respectively. Mutation of the GATA site at -145 reduces activity of the full-length promoter by approximately 30%. Mutation of an E-box at -175 does not alter promoter activity.
Departments of Physiology and Medicine and the Cardiovascular Research Laboratories, University of California, Los Angeles, School of Medicine, Los Angeles, California 90095-1760, USA. snichola@med1.medsch.ucla.edu
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Nicholas
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Philipson
D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D050991:GATA4 Transcription Factor; D009206:Myocardium / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D019831:Sodium-Calcium Exchanger / Q000096:biosynthesis*; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D016335:Zinc Fingers / Q000235:genetics / Q000502:physiology*
D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D019831:Sodium-Calcium Exchanger; D014157:Transcription Factors; C110374:sodium-calcium exchanger 1