Department of Medical Biophysics, University of Toronto, Toronto, Canada.
Centre for Genomic and Experimental Medicine, MRC Institute of Genetics and Molecular Medicine, The University of Edinburgh, Edinburgh, UK.
Cell Cycle. 2020 Jan;19(1):15-23. doi: 10.1080/15384101.2019.1690231. Epub 2019 Nov 24.
The DNA damage response (DDR) associated post-translational modifications recruit chromatin remodelers, signaling proteins such as 53BP1 and repair factors to chromatin flanking DNA double strand breaks (DSBs) to promote its repair. Although localization of both RNF168 ubiquitin ligase and SET8 methyltransferase at DSBs is essential for 53BP1's recruitment to DSBs, it is unclear if they do so via the same pathways. Here we report that RNF168 mediates SET8's recruitment to DSBs. Depletion of cellular pool of ubiquitin through proteasome inhibition abolished RNF168 and SET8's localization to DNA damage. Knockdown of RNF8 or RNF168 abolished SET8's recruitment to DNA damage. Moreover, RNF168 and SET8 form stable complexes . Based on these results we propose a model in which SET8, which despite being a pan-chromatin binding protein, can accumulate several folds at chromatin flanking DSBs through tethering to other proteins that specifically localize to chromatin regions with specific modifications.
DNA 损伤反应 (DDR) 相关的翻译后修饰可招募染色质重塑酶、信号蛋白（如 53BP1）和修复因子到 DNA 双链断裂 (DSB) 周围的染色质，以促进其修复。尽管 RNF168 泛素连接酶和 SET8 甲基转移酶在 DSB 处的定位对于 53BP1 募集到 DSB 是必不可少的，但尚不清楚它们是否通过相同的途径实现。在这里，我们报告 RNF168 介导 SET8 募集到 DSB。通过蛋白酶体抑制耗尽细胞内泛素池会消除 RNF168 和 SET8 到 DNA 损伤的定位。敲低 RNF8 或 RNF168 会消除 SET8 募集到 DNA 损伤。此外，RNF168 和 SET8 形成稳定的复合物。基于这些结果，我们提出了一个模型，其中 SET8 尽管是一种全染色质结合蛋白，但可以通过与其他专门定位于具有特定修饰的染色质区域的蛋白质连接，在 DSB 周围的染色质上积累数倍。
