Expression of 4EBP-1-5A enhances expression of p27Kip1 and inhibits expression of cyclin D1. (A) MCF7-4EBP-1-5A cells were treated with or without pon A and harvested 1, 2 or 3 days after treatment for analysis of cellular proteins by Western blotting. Each lane represents proteins from 2 × 105 cells. The same membrane was used to detect p27Kip1, cyclin D1, CDK2, CDK4 and β-actin. (B) MCF7-4EBP-1-5A (left) or MCF7-pERV3 (right) cells treated with ponA (gray bars) or left untreated (open bars) for 3 days were analyzed as described in A. After Western blotting, protein levels were estimated by densitometry and normalized using β-actin as a standard.