Figure 4.

Comparing Rates of Nucleolar Import and Export of RPL27-GFP

(A) Two daughter HeLa^RPL27-GFP cells from mitosis were chosen. The GFP fluorescence in the nucleus of the upper cell and the fluorescence in the cytoplasm of the lower cell were photobleached. The two photobleached cells were imaged every 5 min for the next 20 hr, and the fluorescence intensity in the nucleoli and cytoplasm was measured. Scale bars represent 5 μm.

(B) Quantitation of the nucleolar (red) and cytoplasmic (green) fluorescence recovery. All data were expressed relative to the fluorescence intensities before photobleaching.

(C) HeLa cells were labeled with ¹³C₆¹⁵N₄-arginine and ¹³C₆¹⁵N₂-lysine SILAC medium for 4, 8, and 20 hr (see Figures 1 and 2). Cytoplasmic ribosomes were purified and analyzed by LC-MS. Profiles of the fraction of labeling of rproteins were determined as described in the legend to Figure 2. The profile of nucleolar RPL27 is included as a reference.