IN-VITRO AND IN-VIVO PROMOTER ANALYSES OF THE MOUSE PHOSPHOLAMBAN GENE

To determine the mechanisms responsible for regulation of the phosphol amban (PLB) gene expression, a critical regulatory phosphoprotein in c ardiac muscle, the mouse PLB gene was isolated and promoter analysis w as performed in vitro and in vivo. The PLB gene consists of two exons separated by a single large intron. Deletion analysis revealed that a 7-kb 5' flanking fragment (including exon 1, the entire intron and par t of exon 2) was necessary for maximal transcriptional activity in H9c 2 and L6 cell lines. Interestingly, deletion of a 2.4-kb intronic regi on, which contained repetitive elements, caused a dramatic increase in CAT activity in both these cell lines. In vivo analysis indicated tha t the PLB fusion gene containing 7 kb of the 5'-flanking region was ca pable of cardiac specific gene expression in transgenic mice. Furtherm ore, these mice exhibited 3-fold higher levels of CAT activity in the ventricles compared with the atria, mimicking endogenous PLB mRNA expr ession. Our findings suggest that: (a) PLB gene expression may be regu lated by the interplay of cis-acting regulatory elements located withi n the 5' flanking and intronic regions; and (b) the 7-kb upstream regi on is capable of directing cardiac-specific and compartment-specific e xpression in vivo. (C) 1997 Elsevier Science B.V.