Pax3-3′UTR is a target for miR-1 and miR-206. (A) CMV promoter driving Luc reporter gene was used for creating Luc-3′UTR, which contains the longer Pax3-3′UTR fragment downstream of the Luc reporter gene. Two putative miR-1/miR-206–binding sites (M1 and M2) were mutated in Luc-3′UTRM. (B) Relative Luc activity was measured in wild-type and MyoD^−/− myoblasts after transfection with control Luc reporter gene + empty expression vector, Luc-3′UTR + empty expression vector, Luc-3′UTR + MyoD expression vector, and Luc-3′UTRM + MyoD expression vector. (C) Relative Luc activity was measured in wild-type and MyoD^−/− myoblasts after transfection with Luc-3′UTR + control pre-miRNA, Luc-3′UTR + pre–miR-1, Luc-3′UTR + pre–miR-206, Luc-3′UTRM + control pre-miRNA, Luc-3′UTRM + pre–miR-1, and Luc-3′UTRM + pre–miR-206. (D) Under differentiation conditions from day 0 to 3 or after UV exposure or treatment with thapsigargin (Thap) for 1 d, cell death was compared between wild-type myoblasts transfected with the control pre-miRNA, pre–miR-1, and pre–miR-206. (E) After UV exposure or treatment with thapsigargin for 1 d, cell death was compared between wild-type myoblasts or MyoD^−/− myoblasts expressing ectopic MyoD transfected with the control miRNA or anti–miR-1 + anti–miR-206. *, P < 0.05; **, P < 0.01. Error bars indicate SEM.