SLOW TROPONIN-C GENE-EXPRESSION IN CHICKEN HEART AND LIVER IS REGULATED BY SIMILAR ENHANCERS

Two isoforms of troponin C (TnC) are encoded by distinct single copy g enes, Expression of fast TnC is restricted to the skeletal muscle, whe reas the slow isoform is expressed in both skeletal and cardiac muscle , Chicken slow TnC (cTnC) gene is also expressed in some non-muscle ti ssues like the liver and the brain, Expression of cTnC gene is regulat ed by two distinct enhancers in cardiac and skeletal muscles, The card iac specific enhancer is located in the immediate 5' flanking region ( bp -124 to -79) of the murine cTnC gene whereas the skeletal enhancer is located within the first intron (bp 997 to 1141), In the present st udy we have examined how cTnC gene expression is regulated in the chic ken liver, Transient transfection of liver cells with cTnC-CAT reporte r constructs containing various regions of the murine cTnC gene showed that its expression in chicken liver is regulated by the cardiac spec ific enhancer, Furthermore, electrophoretic mobility shift assays usin g synthetic oligonucleotides corresponding to both CEF-1 and CEF-2 reg ions of the murine cardiac enhancer revealed formation of specific DNA -protein complexes, Ultraviolet light induced covalent linking of nucl ear proteins to CEF-1 and CEF-2 oligomers were used to examine the nat ure of the cardiac enhancer binding polypeptides; one polypeptide of 4 8 kDa appeared to bind to both CEF-1 and CEF-2 sequences.