CELL CYCLE-DEPENDENT INHIBITION OF P34(CDC2) SYNTHESIS BY TRANSFORMING GROWTH-FACTOR BETA(1) IN CYCLING EPITHELIAL-CELLS

Cycling epithelial cells were shown to reversibly arrest in late G1 ph ase following treatment with transforming growth factor beta1. Associa ted with this G1-S phase arrest was a decrease in the synthesis and hi stone H1 kinase activity of p34cdc2. Transforming growth factor beta1 did not reduce p34cdc2 levels by modulating the turnover of newly synt hesized p34cdc2. The decrease in p34cdc2 synthesis preceded any detect able effect on DNA synthesis. Moreover, the action of transforming gro wth factor beta1 was regulated in a cell cycle-specific manner; epithe lial cells were sensitive to transforming growth factor beta1 only dur ing the G1 phase. The results suggest that p34cdc2 might be a useful b iochemical marker for investigating the mechanism(s) of transforming g rowth factor beta1 signaling.