FIG. 3.

Silencing of EGFP expression reveals stochastic and graded responses to TPA treatment. Clone HS2γEGFP-1 was grown for the indicated times with or without hygromycin (hygro) and then treated with 5 nM TPA (shaded) or vehicle (unshaded) for 20 h before each analysis. (A) Flow cytometric analysis was used to measure the percentage of EGFP-positive cells in the viable cell population. (B) The percentage of EGFP-positive cells determined in panel A is expressed as a function of culture time. (C) EGFP was quantitated in cell lysates by fluorometry and normalized by protein concentration and copy number of the integrated reporter construct.