Figure 3. Highly condensed chromatin body devoid of known chromatin markers.

Single optical sections with 3DSIM of immunostained nuclei using antibodies recognizing the indicated epitopes. The arrowheads point to the most condensed chromatin body. The bar in (a) indicates 500 nm for all panels. (a) A region or two of very high DNA concentration (‘knob') stained with DAPI (white in the right panel). In the merged image (left), telomere (Taz1-GFP; green) and silent H3K9me3 foci (red) are superimposed on the DAPI image (blue). (b) RNA polymerases or histone modifications are shown in green superimposed on DAPI staining (magenta in the left panels or white in the middle panels). In the right panels, knob regions are indicated by the red contours superimposed on the RNA polymerase or histone modification images as indicated. Markers of euchromatin are absent in knob regions. (c) Core histones C-terminally fused with GFP are present in knobs at about the same intensity as DNA stained with DAPI.