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.

中文翻译：

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组蛋白H2A变体alpha1扩展螺旋指导RNF168介导的泛素化。

组蛋白泛素化在DNA损伤反应（DDR）途径中起重要作用。RNF168在DNA受损时催化赖氨酸13/15（K13 / K15）上的H2A和H2AX泛素化，并促进在受损染色质上产生下游修复因子。在这里，我们报告RNF168遍在N端尾赖氨酸残基的非规范H2A变体H2AZ和macroH2A1 / 2。除了其进化上保守的核小体酸性补丁外，我们确定带正电荷的alpha1延伸螺旋对于RNF168介导的H2A变体泛素化至关重要。此外，RNF168 UMI（UIM和与MIU相关的UBD）亲水酸性残基的突变消除了RNF168介导的泛素化以及53BP1和BRCA1电离辐射诱导的病灶形成。