FIGURE 7.

High N/C ratio nuclei contain lower amounts of PP2A. A and B, nuclei were isolated from extracts containing either 1,000 or 10,000 nuclei/μl and analyzed by immunoblot for PP2A components and ORC2. For 10,000 nuclei/μl, two different isolations were performed. In the first, an equal number of nuclei were isolated relative to the 1,000 nuclei/μl sample. In the second, nuclei were isolated from an equal volume of extract relative to the 1,000 nuclei/μl sample. A sample containing no nuclei is included to control for residual cytoplasmic protein. The results from two independent experiments are shown. C, after the removal of nuclei, cytoplasm from the samples in B was analyzed for PP2A C content. D, extracts were prepared with either 1,000 or 10,000 nuclei/μl and supplemented with either control buffer or 478 nm rPP2A C (Xenopus). An equal number of nuclei were isolated from each condition and blotted for the indicated proteins.