Fig. 4. Both Nuf2 and Hec1 are essential for normal progression of the cell cycle. (A) Representative growth curves for the indicated cell cultures. Tet was added at time 0 to the Nuf2- or Hec1-deficient cell tet (+) cultures, and the number of cells not stained with trypan blue was counted. Each experiment was performed twice, and each time point was examined in duplicate. (B) Cell-cycle distribution of Nuf23-63 and Hec25-1 in cells following inhibition of transgene expression due to addition of tet at time 0. Cells were stained with FITC-anti-BrdU (y-axis, log scale) to detect BrdU incorporation (DNA replication), and with propidium iodide to detect total DNA (x axis, linear scale). The lower-left box represents G1-phase cells, the upper box represents S-phase cells, and the lower-right box represents G2/M-phase cells. The numbers given in the boxes specify the percentage of gated events.