The toxicity of CUG/CCUG repeats in DM is mediated by following mechanisms: a) reduction of MBNL1 in nuclei of DM1 and DM2; b) elevation of CUGBP1 in DM1 and DM2; c) alteration of splicing; d) increase of CUGBP1 translational targets; e) alteration of RNA stability; f) reduction of the rate of protein translation; g) reduction of TFs; h) increase of protein stability; i) increase of Akt and PKC kinases and k) the reduction of cyclin D3. The gene discussed is MBNL1; the disease is myotonic dystrophy type 1.