A, C6 cells were grown on chamber slides and were either incubated in amino acid-depleted medium (Starved) for 4 h or heat shocked at 45 °C for 2 h. Nuclei are marked by arrows. The margin of one starved cell is marked by arrowheads. B, cells were incubated for the indicated times in either amino acid-containing (Control) or amino acid-depleted medium (S). Cells were also treated with actinomycin D (1 μg/ml) for 4 h. One sample was starved for 6 h followed by 3 h incubation in medium containing amino acids (S6h/F3h). Cells were fixed, permeabilized, and prepared for confocal microscopy (A) or immunofluorescence microscopy (B) using an anti-HuR antibody, as described under “Experimental Procedures.”