Figure 2.

The amount of nuclear xSAHH in XTC cells is dependent on the cell cycle. (A) XTC cells arrested in G0 by serum starvation were stimulated to exit G0 by addition of 10% serum. Cells were pulse labeled with BrdU 1 h before fixation, and parallel samples were immunostained for BrdU incorporated in DNA and for xSAHH. The percentage of significant nuclear staining is plotted against the time after serum stimulation (not drawn to scale). (B–D) Nonsynchronous XTC cells were pulse labeled for 1 h with BrdU, fixed, and double stained for de novo–synthesized DNA (B) and for xSAHH (C). Superposition of confocal images shows limited coincidence of both labels (D). The example shown was selected for maximal overlap of both labels. In the nucleus marked with an arrowhead, the peripheral BrdU label likely represents replicating heterochromatin. Bar, 10 μm.