Figure 4.

USP7 modulates histone H2B ubiquitylation by controlling the steady state levels of Mdm2. HeLa cells were grown on 10-cm dishes for 24 h to 30–50% confluency and then treated with Lipofectamine transfection reagent (10 µl) in the absence or presence of (A and B) USP7 siRNA or (C) Mdm2 siRNA and incubated for a further 72 h (an additional transfection with Lipofectamine and Mdm2 siRNA was performed 36 h after the first treatment). Cells were harvested, pelleted by centrifugation, whole-cell extracts were prepared and analysed by 10% SDS-PAGE and western blotting with the antibodies indicated.