A NOVEL E-BOX AT-RICH ELEMENT IS REQUIRED FOR MUSCLE-SPECIFIC EXPRESSION OF THE SARCOPLASMIC-RETICULUM CA2-ATPASE (SERCA2) GENE()

The cardiac/slow twitch sarcoplasmic reticulum (SR) Ca2+-ATPase gene ( SERCA2) encodes a calcium transport pump whose expression is regulated in a tissue-and development-specific manner. Previously we have ident ified two distinct positive regulatory regions (bp -284 to -72 and -18 15 to -1105) as important for SERCA2 promoter activity. Here we demons trate that the SERCA2 distal promoter region functions like an enhance r by activating a heterologous promoter (TK) in a muscle cell-specific manner. Through deletion analysis a core enhancer region was delimite d to the -1467 to -1105 bp fragment. We identified the E box/AT-rich e lement located at -1115 bp as critical for maximal enhancer activity. Gel mobility shift studies revealed that this E box/AT-rich element sp ecifically binds a protein which is induced during Sol8 myogenesis. Th is region includes two other cis-acting elements, CArG and MCAT, which also bind specific nuclear protein complexes from Sol8 myotubes. Muta genesis of each of these sites resulted in decreased SERCA/TK-CAT prom oter activity, Based on these data, we propose that the E box/AT-rich element may contribute along with CArG and MCAT elements to the overal l activation and regulation of the SERCA2 gene promoter.