Terry Fox Molecular Oncology Group and the Bloomfield Center for Research on Aging, Sir Mortimer B. Davis Jewish General Hospital, Lady Davis Institute for Medical Research, Montréal, Québec, Canada.
EMBO J. 2012 Apr 18;31(8):1865-78. doi: 10.1038/emboj.2012.47. Epub 2012 Feb 28.
In response to DNA damage, cells initiate complex signalling cascades leading to growth arrest and DNA repair. The recruitment of 53BP1 to damaged sites requires the activation of the ubiquitination cascade controlled by the E3 ubiquitin ligases RNF8 and RNF168, and methylation of histone H4 on lysine 20. However, molecular events that regulate the accessibility of methylated histones, to allow the recruitment of 53BP1 to DNA breaks, are unclear. Here, we show that like 53BP1, the JMJD2A (also known as KDM4A) tandem tudor domain binds dimethylated histone H4K20; however, JMJD2A is degraded by the proteasome following the DNA damage in an RNF8-dependent manner. We demonstrate that JMJD2A is ubiquitinated by RNF8 and RNF168. Moreover, ectopic expression of JMJD2A abrogates 53BP1 recruitment to DNA damage sites, indicating a role in antagonizing 53BP1 for methylated histone marks. The combined knockdown of JMJD2A and JMJD2B significantly rescued the ability of RNF8- and RNF168-deficient cells to form 53BP1 foci. We propose that the RNF8-dependent degradation of JMJD2A regulates DNA repair by controlling the recruitment of 53BP1 at DNA damage sites.
针对 DNA 损伤，细胞会启动复杂的信号级联反应，导致生长停滞和 DNA 修复。53BP1 招募到损伤部位需要由 E3 泛素连接酶 RNF8 和 RNF168 控制的泛素化级联反应的激活，以及组蛋白 H4 赖氨酸 20 位的甲基化。然而，调控组蛋白甲基化的可及性，以允许 53BP1 招募到 DNA 断裂的分子事件尚不清楚。在这里，我们发现与 53BP1 类似，JMJD2A（也称为 KDM4A）串联结构域与二甲基化组蛋白 H4K20 结合；然而，JMJD2A 在 DNA 损伤后会被蛋白酶体降解，这种降解依赖于 RNF8。我们证明 JMJD2A 被 RNF8 和 RNF168 泛素化。此外，JMJD2A 的异位表达会阻止 53BP1 招募到 DNA 损伤部位，表明其在拮抗 53BP1 对甲基化组蛋白标记物方面发挥作用。JMJD2A 和 JMJD2B 的联合敲低显著挽救了 RNF8 和 RNF168 缺陷细胞形成 53BP1 焦点的能力。我们提出，RNF8 依赖性 JMJD2A 降解通过控制 53BP1 在 DNA 损伤部位的募集来调节 DNA 修复。
