Silencing of the Novel p53 Target Gene Snk/Plk2 Leads to Mitotic Catastrophe in Paclitaxel (Taxol)-Exposed Cells

Abstract

Loss of p53 sensitizes to antimicrotubule agents in human tumor cells, but little is known about its role during mitosis. We have identified the Polo-like kinase family member serum inducible kinase (Snk/Plk2) as a novel p53 target gene. Snk/Plk2 mutagenesis demonstrated that its kinase activity is negatively regulated by its C terminus. Small interfering RNA (siRNA)-mediated Snk/Plk2 silencing in the presence of the mitotic poisons paclitaxel (Taxol) or nocodazole significantly increased apoptosis, similar to p53 mutations, which confer paclitaxel sensitivity. Furthermore, we have demonstrated that the apoptosis due to silencing of Snk/Plk2 in the face of spindle damage occurs in mitotic cells and not in cells that have progressed to a G₁-like state without dividing. Since siRNA directed against Snk/Plk2 promoted death of paclitaxel-treated cells in mitosis, we envision a mitotic checkpoint wherein p53-dependent activation of Snk/Plk2 prevents mitotic catastrophe following spindle damage. Finally, these studies suggest that disruption of Snk/Plk2 may be of therapeutic value in sensitizing paclitaxel-resistant tumors.

ACKNOWLEDGMENTS

We thank Eric Bernhard for assistance with mouse irradiation and thank the Morphology Core in the Center for Molecular Studies of Digestive and Liver Diseases for their expert assistance.

This work was supported by NIH grant T32 CA09677 (T.F.B.), NIH grant PO1 CA75138 (W.S.E.-D.), and funds from the Howard Hughes Medical Institute (W.S.E.-D.). W.S.E.-D. is an Assistant Investigator of the Howard Hughes Medical Institute.