PP6 catalytic activity is required for normal nuclear morphology. (A) A schematic depicting the PP6 holoenzyme, PPP6C catalytic subunit, positions of siRNA duplexes used, and inactivating mutations. (B) HeLa cells stably expressing PPP6C si08–resistant wild-type (si08^ResPPP6C^WT) and phosphatase-dead mutant (si08^ResPPP6C^PD) forms of PPP6C tagged at the C terminus with a FLAG epitope were transfected with control (siCon) or si07 and si08 duplexes targeting PPP6C for 48 h. The cells were Western blotted or fixed and then stained with DAPI, tubulin (Tub), and CREST antibodies. Abnormal nuclear morphology was scored for each condition and is plotted in the graph (n = 3). Molecular mass is given in kilodaltons. Error bars indicate the standard error of the mean. Bars, 10 µm.