JMJD6在DNA双链损伤修复中的作用研究

DNA double-strand breaks (DSBs) can trigger genome rearrangements that have oncogenic potential, therefore cellular pathways that repair and signal DNA damage must be highly sensitive and accurate. The integration of positive and negative control is essential for building fast and effective responses to DNA damage and for limiting the impact of DNA lesions on genome integrity. JMJD6 was reported to be an arginine demethylase or a hydroxylase, which is highly expressed in lung cancer samples. However, the exact role of JMJD6 in tumorigenesis has not been fully elucidated. Our preliminary work found that JMJD6 participates in DSB repair. Our results showed that JMJD6 is recruited to the DSB sites after IR, and abnormal expression of JMJD6 affects the binding of DSB repair proteins to the damaged chromatin as well as the efficiency of DSB repair. We have identified the protein complex interacting with JMJD6, and found that JMJD6 regulates the cellular level of H4K16ac. We are going to investigate the mechanism underlying JMJD6-regulated DSB repair, the substrates of JMJD6 as a demethylase or a hydroxylase, and the role of JMJD6 in chromatin remodeling. We will analyze the relationship between the level of JMJD6 and the malignancy of lung cancer, as well as the survival period of lung cancer patients. At last, Crispr/Cas9 viruses library and high content imaging system will be used to screen other histone methylases or demethylases involved in DSB repair. Our work will uncover an important role for JMJD6 in DSB repair, and support JMJD6 as a potential target for therapeutic intervention of lung cancer.

DNA双链损伤（DSB）可以破坏基因组的稳定性进而诱发肿瘤。细胞内的正、负调节机制协同作用，调控细胞对DSB的准确应答及修复，可有效的维护基因组的稳定并阻止肿瘤的发生。JMJD6具有精氨酸去甲基化酶以及羟化酶的活性，在肺癌组织中高表达，而其在肿瘤发生发展中的作用尚不完全清楚。我们的初步结果表明JMJD6在DSB发生时与损伤位点直接结合，其异常表达影响DSB修复蛋白的募集以及细胞DNA双链损伤修复的能力；我们鉴定了与JMJD6相互作用的蛋白复合体，并发现JMJD6调控细胞内H4K16ac的水平。本课题拟在前期工作基础上，详细阐述JMJD6参与DSB修复的分子机制，探讨JMJD6对染色质结构的影响；分析JMJD6的表达水平与肺癌恶性程度之间的关系；最后我们将利用Crispr/Cas9病毒库筛选其它参与DSB修复的组蛋白修饰酶。我们的研究丰富了DSB修复调控机制，并为肺癌的治疗提供新的靶点。

DNA双链损伤（DSBs，DNA double-strand breaks）在所有DNA损伤中是危害最大的，因为它会引发恶性肿瘤。DSBs的检测和修复对于维护基因组的稳定性至关重要。DNA损伤应答信号通路的起始和传递都是在染色质结构中进行的，因此染色质修饰以及染色质结构是DDR信号通路中非常关键的因素，且DSBs周围组蛋白修饰的程度以及spreading需要受到严格的调控。我们的研究发现JMJD6在DNA损伤发生后会被募集到DNA损伤位点附近。JMJD6控制DSBs附近组蛋白泛素化的spreading，以及下游DNA修复相关蛋白的募集和DSBs附近的转录抑制程度。JMJD6基因敲低会提高HR（homologous recombination）以及NHEJ（nonhomologous end joining）的效率，促进细胞周期检验点恢复，增加IR之后细胞存活。在分子机制方面，我们的研究发现含有JMJC结构域的JMJD6，尽管被报道具有组蛋白精氨酸去甲基化酶和羟化酶的活性，在参与DNA损伤应答调控时并不依赖于其酶活性。JMJD6通过招募SIRT1到染色质上降低DSBs附近的H4K16ac水平实现对DNA损伤应答的调控。我们的研究揭示了JMJD6是一个新的参与DNA损伤位点附近epigenome调控的表观遗传学因子，为更好的理解表观遗传学因子在DNA损伤应答中的作用提供基础。