EVOLUTIONARILY CONSERVED PROMOTER MOTIFS AND ENHANCER ORGANIZATION IN THE MOUSE GENE ENCODING THE IIB MYOSIN HEAVY-CHAIN ISOFORM EXPRESSED IN ADULT FAST SKELETAL-MUSCLE

We have isolated the mouse gene for the MHC isoform expressed in adult type IIB (fast-contracting, glycolytic) skeletal muscle fibers, and determined the DNA sequence of the promoter region. This sequence represents the first example of a promoter for a gene encoding an adult-specific isoform of a mammalian skeletal MHC. The proximal 200 bp of the promoter contains several sequence motifs which are identical or very similar to homologous motifs found in the promoters of a family of chicken skeletal MHC genes. Of these two novel AT-rich sequences may be important for regulation of the promoter. A second feature of the mouse IIB MHC promoter sequence concerns a number of sequence motifs located at ca. - 1.000 bp which are organized in a similar fashion in the IIB MHC promoter and a homologous region of promoter of the mouse muscle creatine kinase gene.