Fig. 6. DPY-21 is not recruited to her-1 regulatory regions in XX animals, unlike other components of the dosage compensation complex. (A,B) False-color confocal immunofluorescence images of wild-type embryos (A) or gut cell nuclei (B) carrying her-1 extrachromosomal arrays that contain multiple copies of her-1 regulatory regions, lac operator repeats (lacO) and a transgene encoding a LacI-GFP fusion protein. LacI-GFP repressor binding to lacO permits array detection by GFP antibodies. For each embryo or gut cell nucleus, a single z-section is shown. Embryos and gut cell nuclei were stained with DAPI (gray) and antibodies to DPY-21 (green), SDC-3 (red) and GFP (blue). The fourth column shows the superimposition of the DPY-21 and SDC-3 images. (A) In embryos that have activated dosage compensation, both DPY-21 and SDC-3 co-localize with the X chromosome, which is denoted by an asterisk in the inset. By contrast, SDC-3, but not DPY-21, localizes to her-1 regulatory regions on the arrays. (B) In adult gut cell nuclei, DPY-21 co-localizes with SDC-3 on X chromosomes, but does not co-localize with SDC-3 on her-1 regulatory regions. Thus, DPY-21 participates directly in the chromosome-wide repression of X but not in the gene-specific repression of her-1. Scale bars: 5 µm.