Nuclear retention of SHARP in DM1 myoblasts treated with leptomycin B. Localization of endogenous NF-κB and SHARP proteins in normal and DM1 myoblasts treated with leptomycin B (10 ng/ml for 24 h) is shown in green. NF-κB (A–C, G–I) and SHARP (D–F, J–L) localize predominantly in the nucleus of normal and DM1 myoblasts after leptomycin B treatment. Scale bar, 10 μM. DAPI, 4,6-diamidino-2-phenylindole; DM1, myotonic dystrophy; LMB, leptomycin B; NF-κB, nuclear factor-κB; SHARP, SMART/HDAC1-associated repressor protein.