2 ADJACENT MYOD1-BINDING SITES REGULATE EXPRESSION OF THE ACETYLCHOLINE-RECEPTOR ALPHA-SUBUNIT GENE

SEVERAL genes encoding putative myogenic regulatory factors have been isolated on the basis of their ability to convert non-muscle cells into myoblasts1-6. Four of these genes code for nuclear proteins that belong to a larger family characterized by a conserved helix-loop-helix motif required for DNA-binding and dimerization7. At least one protein, MyoD1, can function as a transcription factor and activate muscle-specific genes during differentiation8. But the promoter of the δ-subunit gene of the mouse acetylcholine receptor (AChR) was recently reported to be functional in the absence of MyoDl binding sites and it has been suggested that the genes coding for the AChR could be regulated independently of MyoDl protein9. Here, we identify two functional MyoDl-binding sites in the muscle-specific enhancer of the chicken AChR α-subunit gene that are essential for full activity in transfected myotubes. © 1990 Nature Publishing Group.