VARIATIONS IN SIGNAL-MEDIATED NUCLEAR TRANSPORT DURING THE CELL-CYCLEIN BALB C 3T3 CELLS/

Signal-mediated nuclear import was investigated in proliferating BALB/ c 3T3 cells 1, 2, 4, 6, 8, 12, 18, and 21 h after the onset of anaphas e. Using nucleoplasmin-coated colloidal gold particles to assay transp ort capacity, it was found that import was greatest at 1 h postanaphas e (after complete reformation of the nuclear envelope). At this time, both the relative rate of gold uptake and the functional size of the t ransport channels were significantly greater than in control cells, wh ich were randomly selected from nonsynchronized cultures. At 21 h, the re was a decrease in the size of the transport channel, but not the ra te of nuclear import. This suggests that these two factors are regulat ed independently. No changes in transport capacity, compared to contro ls, were detected at other times in the cell cycle. (C) 1994 Academic Press, Inc.