Fig. 5. Change in the localization of YY1 from cytoplasmic to nuclear upon entry into S phase. Synchronized CHO cells were fixed at the times indicated (top, hours after shake-off) and subjected to indirect immunofluorescence for visualization of the distribution of YY1 (E-H) and BrdU (I-L). 3D multiple-wavelength images were collected and are displayed as described in Fig. 4, and representative cells (one cell per column) are shown. Dashed lines indicate the cell periphery. YY1 signals appear mainly cytoplasmic at 1 hour (E), mainly nuclear at 3 (F) and 5 (G) hours, and then mainly cytoplasmic again at 7.5 hours (H). BrdU labeling of nuclei appears at 3 hours (J) and is strong throughout the nuclear volume at 5 (K) and 7.5 (L) hours. At the bottom (M-P), all three wavelengths are shown as a three-color (pseudo) merged images (blue for DAPI, green for Rhod/YY1, red for FITC/BrdU). Scale bars: 2 µm.