Wang Y, Sun H, Wang J, Wang H, Meng L, Xu C, Jin M, Wang B, Zhang Y, Zhang Y, Zhu T
Shanghai Public Health Clinical Center and Shanghai Key Laboratory of Organ Transplantation, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences & Shanghai Jiao Tong University School of Medicine (SJTUSM) and Shanghai Institute of Immunology, Institutes of Medical Sciences, SJTUSM, Shanghai 200031, China.
Cell Death Dis. 2016 Jul 28;7(7):e2316. doi: 10.1038/cddis.2016.198.
EZH2 is a histone methyltransferase whose functions in stem cells and tumor cells are well established. Accumulating evidence shows that EZH2 has critical roles in T cells and could be a promising therapeutic target for several immune diseases. To further reveal the novel functions of EZH2 in human T cells, protein co-immunoprecipitation combined mass spectrometry was conducted and several previous unknown EZH2-interacting proteins were identified. Of them, we focused on a DNA damage responsive protein, Ku80, because of the limited knowledge regarding EZH2 in the DNA damage response. Then, we demonstrated that instead of being methylated by EZH2, Ku80 bridges the interaction between the DNA-dependent protein kinase (DNA-PK) complex and EZH2, thus facilitating EZH2 phosphorylation. Moreover, EZH2 histone methyltransferase activity was enhanced when Ku80 was knocked down or DNA-PK activity was inhibited, suggesting DNA-PK-mediated EZH2 phosphorylation impairs EZH2 histone methyltransferase activity. On the other hand, EZH2 inhibition increased the DNA damage level at the late phase of T-cell activation, suggesting EZH2 involved in genomic integrity maintenance. In conclusion, our study is the first to demonstrate that EZH2 is phosphorylated by the DNA damage responsive complex DNA-PK and regulates DNA damage-mediated T-cell apoptosis, which reveals a novel functional crosstalk between epigenetic regulation and genomic integrity.
EZH2是一种组蛋白甲基转移酶，其在干细胞和肿瘤细胞中的功能已得到充分证实。越来越多的证据表明，EZH2在T细胞中起关键作用，可能是几种免疫疾病的一个有前景的治疗靶点。为了进一步揭示EZH2在人类T细胞中的新功能，我们进行了蛋白质免疫共沉淀结合质谱分析，并鉴定了几种以前未知的与EZH2相互作用的蛋白质。其中，我们重点关注一种DNA损伤反应蛋白Ku80，因为关于EZH2在DNA损伤反应中的知识有限。然后，我们证明Ku80并非被EZH2甲基化，而是在DNA依赖性蛋白激酶（DNA-PK）复合物和EZH2之间架起相互作用的桥梁，从而促进EZH2磷酸化。此外，当Ku80被敲低或DNA-PK活性被抑制时，EZH2组蛋白甲基转移酶活性增强，这表明DNA-PK介导的EZH2磷酸化损害了EZH2组蛋白甲基转移酶活性。另一方面，EZH2抑制在T细胞激活后期增加了DNA损伤水平，这表明EZH2参与基因组完整性的维持。总之，我们的研究首次证明EZH2被DNA损伤反应复合物DNA-PK磷酸化，并调节DNA损伤介导的T细胞凋亡，这揭示了表观遗传调控与基因组完整性之间一种新的功能相互作用。
