Identification of cis-acting DNA elements required for expression of the human cardiac troponin I gene promoter.
The human cardiac troponin I (TnIc) gene exhibits both cardiac-specific and developmentally regulated expression. The structure and expression of this gene as well as the identification of putative regulatory elements have been described previously. This study shows that a minimal promoter containing 98 bp of sequence is sufficient to drive transcription in neonatal rat cardiac myocytes. This region contains several putative cis -regulatory elements including an Initiator element surrounding the start site of transcription, an A/T-rich (TATA/MEF-2) element, two GATA elements and a cytosine-rich region containing overlapping CACC box and Sp1 elements. Using electrophoretic mobility shift assays (EMSAs) this study demonstrates the binding of MEF-2, Oct-1, and recombinant TBP to the A/T-rich element and of GATA-4 to both GATA elements. The CACC/Sp element binds the zinc finger transcription factors Sp1 and Sp3 in addition to an unidentified complex present in neonatal rat cardiac myocytes. Mutation of each of these sites has a deleterious effect on promoter activity as assayed by transient transfection into cardiac myocytes. The data suggest that transcriptional activity of the human TnIc gene can be driven by a compact promoter region and that within this region GATA, MEF-2 Sp1 and CACC box-binding factors are required for optimal activity. Furthermore, a comparison with data obtained for identical elements in the promoters of rodent TnIc genes identifies differences between species which may be of consequence for species-specific promoter function.
Bhavsar
P K
PK
National Heart and Lung Institute, Imperial College School of Medicine, Dovehouse Street, London, SW3 6LY, UK.
Dellow
K A
KA
Yacoub
M H
MH
Brand
N J
NJ
Barton
P J
PJ
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D003596:Cytosine; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D019210:Troponin I / Q000235:genetics*
D019210:Troponin I; D003596:Cytosine