FIGURE 5.

9HE has no detectable effect on rRNA processing in actively growing cells. A, shown is a schematic representation of the pulse-labeling cold-chase of cells with [³H]uridine to determine the effects 9HE on pre-rRNA processing in cells. HCT116 (p53^−/−) cells were grown to 70% confluence and incubated for 2 h with 10 μCi of [³H]uridine to label newly synthesized pre-rRNA (47/45 S). At time point 0 the cells were washed and incubated for 4 and 12 h in unlabeled medium without (no drug) or with 5 μm 9HE. B, total RNA was analyzed as described under “Experimental Procedures.” C, to determine the relative efficiencies of pre-rRNA processing, the data were quantitated (bar graphs: −, no 9HE, gray bars; +9HE, white bars). Transcript levels for 47S/45S pre-rRNA are shown on the left, and the 28S/18S rRNA ratio is shown on the right.