FIG. 9.

Effect of MEKK1 on TR3 mitogenic activity. (A) GFP-TR3 or GFP control expression vector (5 μg) and/or MEKK1-DA expression vector (5 μg) were transfected into H460 or Calu-6 cells, which were seeded in 9-mm-diameter dishes and then maintained in medium containing 0.5% FBS. The transfected and GFP-expressing subpopulations of cells were identified by their high level of green fluorescence compared to nontransfected cells using flow cytometry (24). The cell cycle distribution of the transfected cells was then determined as described for Fig. 2. The increase in S-G₂ phase population was calculated by comparing the S-G₂-phase cells from transfected cells to those from nontransfected cells in the same culture dish. (B) BrdU-positive cells were identified by immunostaining as described for Fig. 3, except that H460 cells were pulsed with BrdU for 6 h. The bars in panels A and B represent the averages ± mean from two experiments.