Figure 3.

Double-label immunofluorescence staining of HT1080 cells for hCAP-E and DNA ligase IV. (A–D) Interphase nuclei display significant colocalization of hCAP-E and DNA ligase IV. Although cytoplasmic staining by the hCAP-E antibody is prominent, DNA ligase IV is largely localized to the nucleus, although some sparse cytoplasmic staining is occasionally visible. (E–H) As cells enter mitosis, colocalization of hCAP-E and DNA ligase IV on condensing chromatin accompanies morphological changes in DNA visualized by DAPI staining. Negative controls in which the second primary antibody is preimmune serum reveal that the observed colocalization of hCAP-E and DNA ligase IV is not an artifact of the staining method (I–L).