Figure 4

Vpr has little or no effect on proteasome-mediated protein degradation of Cdc25A in contrast to HU/UV. (A) Synchronized G1/S HeLa cells treated with HU, UV or transduced with Adv-Vpr were collected at the indicated time, and then subjected to Western blot analysis using anti-Cdc25A and anti-Vpr antibodies (a). β-actin was used as a loading control. The relative intensity of the Cdc25A protein levels to β-actin was determined by densitometry and the Cdc25A protein level at 0 hour was set as 1.0. (b). The results presented are the average of three independent experiments. (B) Synchronized HeLa cells were treated with 50 μm MG132 at 0 hour and collected 5 hours after treatment. The protein level of Cdc25A was detected by Western blot analysis. (C) HeLa cells were pre-treated with specific siRNA against Chk1, which were then synchronized at G1/S boundary by the DT blocks. HU- or Vpr-treated cells were collected 5 hours after the DT release. The protein level of Cdc25A was detected by Western blot analysis using the indicated antibodies.