The E3 ligase PIRH2 polyubiquitylates CHK2 and regulates its turnover
The E3 ligase PIRH2 polyubiquitylates CHK2 and regulates its turnover
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DOI：
10.1038/cdd.2013.7
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发表时间：
2013-06-01
影响因子：
12.4
通讯作者：
Hakem, R.
中科院分区：
文献类型：
--
作者：
Bohgaki, M.;Hakem, A.;Hakem, R.
丝氨酸苏氨酸激酶检查点蛋白2(Chk2)是一种DNA损伤检查点蛋白，在ATM-P53信号通路中起重要作用。除了它的磷酸化，Chk2也是泛素化的，两种翻译后修饰对它的功能都很重要。然而，尽管调控Chk2磷酸化的机制已被很好地建立，但那些控制其泛素化的机制还不完全清楚。在这项研究中，我们证明了泛素E3连接酶PIRH2(P53诱导的蛋白带环(真正有趣的新基因)-H2结构域)与Chk2相互作用，并介导其多泛素化和蛋白酶体降解。我们发现，去泛素化酶USP28与PIRH2和Chk2形成一个复合体，并拮抗PIRH2介导的Chk2的多泛素化和蛋白酶体降解。我们还提供了PIRH2泛素化Chk2依赖于其磷酸化状态的证据。Pirh2基因缺失的细胞表现出Chk2的积聚和G1/S和G2/M细胞周期检查点的过度激活。然而，在Pirh2(-/-)Chk2(-/-)细胞中不再观察到这种过度激活，这为Pirh2调节Chk2的重要性提供了证据。这些发现表明，PIRH2在Chk2的泛素化及其周转和其功能的调节中起着核心作用。
The serine threonine kinase checkpoint kinase 2 (CHK2) is a DNA damage checkpoint protein important for the ATM-p53 signaling pathway. In addition to its phosphorylation, CHK2 is also ubiquitylated, and both post-translational modifications are important for its function. However, although the mechanisms that regulate CHK2 phosphorylation are well established, those that control its ubiquitylation are not fully understood. In this study, we demonstrate that the ubiquitin E3 ligase PIRH2 (p53-induced protein with a RING (Really Interesting New Gene)-H2 domain) interacts with CHK2 and mediates its polyubiquitylation and proteasomal degradation. We show that the deubiquitylating enzyme USP28 forms a complex with PIRH2 and CHK2 and antagonizes PIRH2-mediated polyubiquitylation and proteasomal degradation of CHK2. We also provide evidence that CHK2 ubiquitylation by PIRH2 is dependent on its phosphorylation status. Cells deficient in Pirh2 displayed accumulation of Chk2 and enhanced hyperactivation of G1/S and G2/M cell-cycle checkpoints. This hyperactivation was, however, no longer observed in Pirh2(-/-) Chk2(-/-) cells, providing evidence for the importance of Chk2 regulation by Pirh2. These findings indicate that PIRH2 has central roles in the ubiquitylation of Chk2 and its turnover and in the regulation of its function.