Figure 3.

DNA halos and replication sites in relationship to chromosome territory disruption in NHF-1 cells. A and D, intact cells; B and E, DNA-rich nuclear matrix 1 (RNase + 0.65 M (NH₄)₂SO₄); C, F, G, H, and I, DNA-rich nuclear matrix 2 (2.0 M NaCl following RNase A digestion). The presence of a DNA halo was evaluated by dual staining of the nuclear periphery with nuclear lamin antibodies (green) and total DNA with propidium iodide (red). All preparations of DNA-rich nuclear matrix were devoid of DNA halos (E), as were control cells (D), except under conditions that led to chromosome territory disruption (F, see arrow). H and I show the single channel images of DNA and lamin staining, respectively, that correspond to the image in F. G shows portions of a disrupted chromosome territory (chromosome 1, green) extending into the faint DNA halo (see arrows). DNA replication sites are labeled in vivo with BrdU (A, B, and C; see Materials and Methods) followed by extraction for DNA-rich nuclear matrix. Boxed inserts show replication sites at higher magnification (see arrows for individual sites). The replication sites are identical to those of control cells (A) in all DNA-rich nuclear matrix preparations (e.g., B), except where chromosome territories are disrupted (C). Bars (A–G, 5 μm; H and I, 4 μm).