Control of HIPK2 stability by ubiquitin ligase Siah-1 and checkpoint kinases ATM and ATR


The tumour suppressor HIPK2 is an important regulator of cell death induced by DNA damage, but how its activity is regulated remains largely unclear. Here we demonstrate that HIPK2 is an unstable protein that colocalizes and interacts with the E3 ubiquitin ligase Siah-1 in unstressed cells. Siah-1 knockdown increases HIPK2 stability and steady-state levels, whereas Siah-1 expression facilitates HIPK2 polyubiquitination, degradation and thereby inactivation. During recovery from sublethal DNA damage, HIPK2, which is stabilized on DNA damage, is degraded through a Siah-1-dependent, p53-controlled pathway. Downregulation of Siah-1 inhibits HIPK2 degradation and recovery from damage, driving the cells into apoptosis. We have also demonstrated that DNA damage triggers disruption of the HIPK2–Siah-1 complex, resulting in HIPK2 stabilization and activation. Disruption of the HIPK2–Siah-1 complex is mediated by the ATM/ATR pathway and involves ATM/ATR-dependent phosphorylation of Siah-1 at Ser 19. Our results provide a molecular framework for HIPK2 regulation in unstressed and damaged cells.

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Figure 1: HIPK2, an unstable protein, is stabilized when DNA is damaged and its stability is regulated by Siah-1.
Figure 2: Siah-1 mediates HIPK2 polyubiquitination and degradation.
Figure 3: Colocalization and in vitro and in vivo interaction of Siah-1 and HIPK2.
Figure 4: Siah-1 controls HIPK2 degradation during recovery from damage and regulates DNA damage-induced apoptosis.
Figure 5: p53 regulates Siah-1-dependent HIPK2 degradation.
Figure 6: ATM and ATR regulate HIPK2 stability and HIPK2–Siah-1 interaction.
Figure 7: ATM and ATR phosphorylate Siah-1 at Ser 19 and regulate HIPK2–Siah-1 interaction.
Figure 8: A model for HIPK2 regulation in unstressed and DNA-damaged cells.


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We are grateful to the following colleagues for providing expression plasmids, cell lines or antibodies: L. Susini, P. Matthias, G. Rohaly, T. Wirth, R. Marschalek, R.T. Abraham, M.B. Kastan, B. Vogelstein and G. Lozano. We thank E. Krieghoff-Henning for comments on the manuscript and B. Haas for technical assistance. This study was supported by grants from the Deutsche Krebshilfe (10-2211-Ho1), the Deutsche Forschungsgemeinschaft (HO2438/3-1) and the Landesstiftung Baden-Württemberg to T.G.H.

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Correspondence to Thomas G. Hofmann.

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Winter, M., Sombroek, D., Dauth, I. et al. Control of HIPK2 stability by ubiquitin ligase Siah-1 and checkpoint kinases ATM and ATR. Nat Cell Biol 10, 812–824 (2008) doi:10.1038/ncb1743

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