Center of Integrated Medical Research, School of Medicine, Keio University, 35 Shinano-machi, Shinjuku-ku, Tokyo, 160-8582, Japan.
Nature. 2010 Aug 19;466(7309):941-6. doi: 10.1038/nature09297.
DNA double-strand breaks (DSBs) pose a potent threat to genome integrity. These lesions also contribute to the efficacy of radiotherapy and many cancer chemotherapeutics. DSBs elicit a signalling cascade that modifies the chromatin surrounding the break, first by ATM-dependent phosphorylation and then by RNF8-, RNF168- and BRCA1-dependent regulatory ubiquitination. Here we report that OTUB1, a deubiquitinating enzyme, is an inhibitor of DSB-induced chromatin ubiquitination. Surprisingly, we found that OTUB1 suppresses RNF168-dependent poly-ubiquitination independently of its catalytic activity. OTUB1 does so by binding to and inhibiting UBC13 (also known as UBE2N), the cognate E2 enzyme for RNF168. This unusual mode of regulation is unlikely to be limited to UBC13 because analysis of OTUB1-associated proteins revealed that OTUB1 binds to E2s of the UBE2D and UBE2E subfamilies. Finally, OTUB1 depletion mitigates the DSB repair defect associated with defective ATM signalling, indicating that pharmacological targeting of the OTUB1-UBC13 interaction might enhance the DNA damage response.
DNA 双链断裂 (DSBs) 对基因组完整性构成严重威胁。这些损伤也有助于放射治疗和许多癌症化疗药物的疗效。DSBs 引发了一个信号级联反应，改变了断裂周围的染色质，首先是 ATM 依赖性磷酸化，然后是 RNF8、RNF168 和 BRCA1 依赖性调节泛素化。在这里，我们报告说去泛素化酶 OTUB1 是 DSB 诱导的染色质泛素化的抑制剂。令人惊讶的是，我们发现 OTUB1 通过与 RNF168 的同源 E2 酶 UBC13（也称为 UBE2N）结合并抑制其，从而独立于其催化活性抑制 RNF168 依赖性多泛素化。这种不寻常的调节模式不太可能仅限于 UBC13，因为对 OTUB1 相关蛋白的分析表明，OTUB1 与 UBE2D 和 UBE2E 亚家族的 E2 酶结合。最后，OTUB1 的耗竭减轻了与 ATM 信号缺陷相关的 DSB 修复缺陷，表明药理学靶向 OTUB1-UBC13 相互作用可能增强 DNA 损伤反应。
