Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada.
Mol Cell. 2012 Aug 10;47(3):383-95. doi: 10.1016/j.molcel.2012.05.045. Epub 2012 Jun 27.
The response to DNA double-strand breaks (DSBs) entails the hierarchical recruitment of proteins orchestrated by ATM-dependent phosphorylation and RNF8-mediated chromatin ubiquitylation. As in most ubiquitin-dependent processes, the ordered accumulation of DNA repair factors at the break site relies on ubiquitin-binding domains (UBDs). However, how UBDs select their ligands is poorly understood, and therefore we sought to uncover the basis for selectivity in the ubiquitin-dependent DSB response. We show that RNF168, its paralog RNF169, RAD18, and the BRCA1-interacting RAP80 protein accumulate at DSB sites through the use of bipartite modules composed of UBDs juxtaposed to peptide motifs that provide specificity. These sequences, named LR motifs (LRMs), are transferable, and we show that the RNF169 LRM2 binds to nucleosomes, the substrates of RNF168. The LRM-based selection of ligands is a parsimonious means to build a highly discrete ubiquitin-based signaling pathway such as the DNA damage response.
DNA 双链断裂（DSBs）的反应需要 ATM 依赖性磷酸化和 RNF8 介导的染色质泛素化协调的蛋白质的分层招募。与大多数依赖泛素的过程一样，断裂部位 DNA 修复因子的有序积累依赖于泛素结合结构域（UBD）。然而，UBD 如何选择其配体尚不清楚，因此我们试图揭示依赖泛素的 DSB 反应中选择性的基础。我们表明，RNF168、其同源物 RNF169、RAD18 和与 BRCA1 相互作用的 RAP80 蛋白通过使用由 UBD 与提供特异性的肽基序并列组成的二聚体模块积累在 DSB 部位。这些序列被命名为 LR 基序（LRMs），是可转移的，我们表明 RNF169 的 LRM2 结合核小体，即 RNF168 的底物。基于 LRM 的配体选择是构建高度离散的基于泛素的信号通路（如 DNA 损伤反应）的一种简约方法。
