The -250/-40 bp mouse Myl2 regulatory region sequence, containing enhancer Rr315, is placed upstream of the 230/+126 bp Tnni3 promoter sequence (and the chimeric enhancer-promoter is flanked by chicken beta-globin locus insulator sequence), followed by a beta-globin/IgG chimeric intron, nls sequence, the lacZ beta-galactosidase gene and bovine GH poly(A) signal sequence. (J:76656)