Figure 1

UbcH7 levels control the entry and exit from S phase. (A) Cells were treated with siRNA to deplete UbcH7 (U7) or a non silencing siRNA (NS) for 72 h. The cell cycle profile was determined by propidium iodide staining. (B) HeLa cells were treated for 48 h with UbcH7 specific siRNA (U7) or a non silencing siRNA (NS) as indicated. Cells were then synchronized at the G1/S boundary by treatment with 2 mM hydroxyurea for 18 h. Cells were allowed to enter cycle after removal of hydroxyurea and culture in drug-free medium. The cell cycle profile at each time point after drug removal was determined. (C) COS cells were transiently transfected with plasmids containing UbcH7 or an empty vector. After 48 h of expression, the cell cycle profile was determined as above.