Fig. 4. Nucleolar localization of XCAPE and topoII in an interphase nucleus. XL-2 cells were grown and fixed as described in Materials and Methods. Cell were then processed for double immunofluorescence staining (A-E) with anti-XCAP-E affinity-purified polyclonal antibody (C) and anti-human topoII monoclonal antibody (D). Double staining is shown in e. Cells were observed by phase contrast microscopy (A) and stained with DAPI (B). For electron microscopy (F-H), cells were fixed as described under Materials and Methods and then labeled for double immunogold electron microscopy with an anti-XCAP-E affinity-purified polyclonal antibody and an anti-human topoII monoclonal antibody. Anti-XCAP-E and anti-topoII antibodies were revealed with a secondary anti-rabbit antibody conjugated to 5 nm gold particle (for XCAP-E) and an anti-mouse antibody conjugated to a 10 nm gold particles (for topoII, arrows), respectively. Bar, 5 µm (A-E), 1 µm (F) and 0.2 µm (G,H).