Because examination of DM1 cells revealed that both cyclin D3 and cdk4 levels did not increase in DM1 differentiating cells, reduction in formation of the translational complex CUG-BP1-eIF2 provides a reasonable explanation for the reduction in p21 and Mef2A translation in DM1 myoblasts. The gene discussed is CDK4; the disease is myotonic dystrophy type 1.