Figure 4. HuR regulates mitochondrial morphology through Bcl_xL. (A) U2OS were transiently transfected with HuR-targeting, non-silencing (Ctrl), or a combination of HuR- and Bcl_xL -targeting siRNA and the cells were prepared for immunofluorescent microscopy 72 h later. Mitochondrial morphology was visualized by staining with anti-Tom20 antibody. (B) The fraction of cells with fragmented mitochondria from (A) were determined by two blind observers and is plotted for each treatment (* p < 0.05; n = 83 cells for each treatment) (C) Expression levels of Bcl_xL and HuR in lysates from cells treated as in (A) were determined by western blot analysis.