Figure 4. Downregulation of the p27^Kip1 gene following PKC_α activation. A: PKC_α mRNA level is downregulated at the 3 h point following 24 h of siRNA-PKC_α (lane 2) treatment, but not upregulated following PMA (lane 4) and thymeleatoxi (lane 3) treatment. lane 1, control. B: p27^kip1 mRNA level is downregulated following 3 h of PMA (lane 4) and thymeleatoxi (lane 3) treatment and upregulated following siRNA-PKC_α (lane 2) treatment. lane 1, control. Five micrograms of RNA was used for each reaction. C: RT–PCR analysis of RPE cells stimulated with 24 h PMA and thymeleatoxin treatment shows a strong downregulation of the p27 mRNA at 1, 2, and 6 h following PMA, or at 1 and 2 h following thymeleatoxin treatment. D: Optical density of P27 mRNA determined by densitometric imaging is shown (Mean±SD, n=4). The GAPDH band is used for quantitation.