Winter Melanie, Sombroek Dirk, Dauth Ilka, Moehlenbrink Jutta, Scheuermann Karin, Crone Johanna, Hofmann Thomas G
Cellular Senescence Group, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 242, 69120 Heidelberg, Germany.
Nat Cell Biol. 2008 Jul;10(7):812-24. doi: 10.1038/ncb1743. Epub 2008 Jun 8.
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.
肿瘤抑制因子HIPK2是DNA损伤诱导的细胞死亡的重要调节因子，但其活性是如何被调节的在很大程度上仍不清楚。在这里，我们证明HIPK2是一种不稳定的蛋白质，在未受应激的细胞中与E3泛素连接酶Siah-1共定位并相互作用。敲低Siah-1可增加HIPK2的稳定性和稳态水平，而Siah-1的表达则促进HIPK2的多聚泛素化、降解，从而使其失活。在从亚致死性DNA损伤中恢复的过程中，在DNA损伤时稳定的HIPK2通过一条依赖Siah-1、受p53控制的途径被降解。下调Siah-1可抑制HIPK2的降解和损伤恢复，促使细胞凋亡。我们还证明，DNA损伤会触发HIPK2-Siah-1复合物的解离，导致HIPK2的稳定和激活。HIPK2-Siah-1复合物的解离由ATM/ATR途径介导，涉及ATM/ATR依赖的Siah-1在丝氨酸19处的磷酸化。我们的结果为未受应激和受损细胞中HIPK2的调节提供了一个分子框架。
