Department of Radiation Oncology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, United States.
Hefei National Laboratory for Physical Science at the Microscale, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, 230027, Hefei, Anhui, China.
Nat Commun. 2020 May 18;11(1):2462. doi: 10.1038/s41467-020-16307-4.
Histone ubiquitination plays an important role in the DNA damage response (DDR) pathway. RNF168 catalyzes H2A and H2AX ubiquitination on lysine 13/15 (K13/K15) upon DNA damage and promotes the accrual of downstream repair factors at damaged chromatin. Here, we report that RNF168 ubiquitinates the non-canonical H2A variants H2AZ and macroH2A1/2 at the divergent N-terminal tail lysine residue. In addition to their evolutionarily conserved nucleosome acidic patch, we identify the positively charged alpha1-extension helix as essential for RNF168-mediated ubiquitination of H2A variants. Moreover, mutation of the RNF168 UMI (UIM- and MIU-related UBD) hydrophilic acidic residues abolishes RNF168-mediated ubiquitination as well as 53BP1 and BRCA1 ionizing radiation-induced foci formation. Our results reveal a juxtaposed bipartite electrostatic interaction utilized by the nucleosome to direct RNF168 orientation towards the target lysine residues in proximity to the H2A alpha1-extension helix, which plays an important role in the DDR pathway.
组蛋白泛素化在 DNA 损伤反应 (DDR) 途径中发挥着重要作用。RNF168 在 DNA 损伤时催化 H2A 和 H2AX 在赖氨酸 13/15（K13/K15）上的泛素化，并促进下游修复因子在受损染色质上的积累。在这里，我们报告 RNF168 在分歧的 N 端尾部赖氨酸残基上泛素化非典型 H2A 变体 H2AZ 和 macroH2A1/2。除了它们进化上保守的核小体酸性斑，我们还确定带正电荷的α1-延伸螺旋对于 RNF168 介导的 H2A 变体泛素化是必不可少的。此外，RNF168 的 UMI（UIM 和 MIU 相关 UBD）亲水性酸性残基的突变会破坏 RNF168 介导的泛素化以及 53BP1 和 BRCA1 电离辐射诱导焦点的形成。我们的结果揭示了核小体利用毗邻的双部分静电相互作用来指导 RNF168 朝向靶赖氨酸残基的取向，这在 DDR 途径中起着重要作用。
