Figure 2.

Mus81 is a nuclear protein that is retained in nucleoli after in situ extraction. Indirect immune fluorescence analysis of HeLa cells using affinity purified antibody to Mus81 revealed a predominantly nuclear pattern of staining with increased intensity in subnuclear bodies. (A) Samples on the left-hand side were fixed after a brief wash in PBS to remove extracellular proteins only. (B) Samples on the righthand side were extracted with detergent containing buffers to remove soluble proteins before fixation (Mirzoeva and Petrini, 2001). Samples were costained with DAPI to reveal DNA. Treatment of cells with UV-light, HU, or CTP before fixation had little effect on the localization of Mus81.