Figure 3.

ZPR1 is not an integral component of the fibrillar or granular components of the nucleolus. Proliferating HEp-2 cells were treated (4 h) with 0.1 μg/ml actinomycin D or with 25 μg/ml of the adenosine analogue DRB, fixed, and processed for immunofluorescence microscopy using antibodies to ZPR1 (FITC, green) and antibodies that stain the fibrillar component (fibrillarin; rhodamine, red) and the granular component (B23; rhodamine, red) of the nucleolus. Cells treated with actinomycin D were stained with ZPR1 and fibrillarin (A). Cells treated with DRB were stained with antibodies to ZPR1 and fibrillarin (B) or ZPR1 and B23 (C). A photomicrograph of the differential interference contrast (DIC) image is presented in each panel.