Fig. 4. Equal partitioning of Sp1 and Sp3 between daughter nuclei. MCF-7 cells grown on coverslips were treated with 0.06 µg/ml colcemid for 16 hours, cultured for 3 more hours in fresh medium and immunolabeled with anti-Sp1 and anti-Sp3 while co-stained with DAPI. Bar, 5 µm. A quantitative image analysis was performed to determine the relative levels of Sp1 and Sp3 in the telophase cells. The partition coefficient (PC) indicates the ratio of integrated signal intensities between two daughter nuclei. Student's t-test was applied to assess the significance of observed differences.