Ontario Cancer Institute, University Health Network and Department of Medical Biophysics, University of Toronto, Toronto, M5G 2M9 ON, Canada.
Proc Natl Acad Sci U S A. 2013 Dec 24;110(52):20982-7. doi: 10.1073/pnas.1320302111. Epub 2013 Dec 9.
Defective signaling or repair of DNA double-strand breaks has been associated with developmental defects and human diseases. The E3 ligase RING finger 168 (RNF168), mutated in the human radiosensitivity, immunodeficiency, dysmorphic features, and learning difficulties syndrome, was shown to ubiquitylate H2A-type histones, and this ubiquitylation was proposed to facilitate the recruitment of p53-binding protein 1 (53BP1) to the sites of DNA double-strand breaks. In contrast to more upstream proteins signaling DNA double-strand breaks (e.g., RNF8), deficiency of RNF168 fully prevents both the initial recruitment to and retention of 53BP1 at sites of DNA damage; however, the mechanism for this difference has remained unclear. Here, we identify mechanisms that regulate 53BP1 recruitment to the sites of DNA double-strand breaks and provide evidence that RNF168 plays a central role in the regulation of 53BP1 functions. RNF168 mediates K63-linked ubiquitylation of 53BP1 which is required for the initial recruitment of 53BP1 to sites of DNA double-strand breaks and for its function in DNA damage repair, checkpoint activation, and genomic integrity. Our findings highlight the multistep roles of RNF168 in signaling DNA damage.
DNA 双链断裂的信号转导或修复缺陷与发育缺陷和人类疾病有关。E3 连接酶 RING 指蛋白 168（RNF168）在人类辐射敏感性、免疫缺陷、畸形特征和学习困难综合征中发生突变，被证明可以泛素化 H2A 型组蛋白，并且这种泛素化被认为有助于 p53 结合蛋白 1（53BP1）募集到 DNA 双链断裂部位。与更上游的 DNA 双链断裂信号转导蛋白（如 RNF8）不同，RNF168 的缺乏完全阻止了 53BP1 在 DNA 损伤部位的初始募集和保留；然而，这种差异的机制仍不清楚。在这里，我们确定了调节 53BP1 募集到 DNA 双链断裂部位的机制，并提供了证据表明 RNF168 在调节 53BP1 功能中发挥着核心作用。RNF168 介导 53BP1 的 K63 连接泛素化，这对于 53BP1 最初募集到 DNA 双链断裂部位以及其在 DNA 损伤修复、检查点激活和基因组完整性中的功能是必需的。我们的发现强调了 RNF168 在 DNA 损伤信号转导中的多步骤作用。
