Figure 7. Binding of SDS22 to PP1 inhibits dephosphorylation of Aurora B in vitro.

A PP1 specifically dephosphorylates Aurora B pT232. Recombinant, autophosphorylated Aurora B (left panel) or in vitro phosphorylated GST-Survivin (right panel) was incubated either alone or with purified PP1 at indicated concentrations. Lambda phosphatase (λPP) was used as a positive control. Phosphorylation at T232 (Aurora B) and T34 (Survivin) was detected by Western blot with phospho-specific antibodies and equal loading confirmed by Ponceau S staining. Note PP1-mediated dephosphorylation of Aurora B, but not of Survivin.

B, C SDS22 inhibits PP1-mediated dephosphorylation of Aurora B at T232 in a dose-dependent manner. Phosphorylated GST-Aurora B was incubated with purified PP1 without or with the indicated concentration of purified SDS22 and phosphorylation monitored as in (A). Equal loading was monitored with GST antibodies. Western blot signals from three independent experiments were quantified (C) and normalized to maximum and minimum values. Error bars represent s.e.m.

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