Interaction of a protein factor within a thyroid hormone-sensitive region of rat alpha-myosin heavy chain gene

Using a gel mobility-shift assay, a nuclear protein factor was identified in cardiac myocyte which binds specifically to a DNA fragment from the 5' region of the alpha-myosin heavy chain gene shown previously to contain a thyroid hormone-sensitive element. Methylation interference experiments located the binding site within a 24-base pair sequence from positions -599 to -576. A double-stranded synthetic oligonucleotide containing this 24-base pair sequence bound to the factor and effectively competed with the natural binding site for factor binding. The factor was present in rat and human fibroblasts, and rat GH1 cells as well as L6E9 myoblasts and myotubes. The specificity with which this factor binds to DNA suggests that it could be involved in regulation of the alpha-myosin heavy chain gene.