Muscle LIM protein promotes expression of the acetylcholine receptor γ-subunit gene cooperatively with the myogenin-E12 complex

Muscle LIM protein (MLP, also referred to as CRP3) is a muscle-specific LIM-only protein, which consists of two LIM motifs. MLP functions as a positive regulator during myogenesis. Here we report that MLP serves as a cofactor regulating the expression of the nicotinic acetylcholine receptor (AChR) γ-subunit gene in skeletal muscle cells. We found that MLP promoted the expression of the AChR γ-subunit gene in C2C12 myotubes, but not in C2C12 myoblasts or NIH3T3 fibroblasts. Furthermore, we showed that MLP interacted with myogenin in vivo and enhanced the binding ability of the myogenin-E12 heterodimer to the E boxes in the AChR γ-subunit gene promoter. Together, these results suggest that MLP promotes the specific expression of the AChR γ-subunit gene cooperatively with the myogenin-E12 complex during myogenesis.