Tudor-SN蛋白通过调控染色质的高级结构及周期阻滞促进DNA修复的机制

Tudor-SN is a multifunctional protein. We have been focusing on this protein over a decade. It has been identified as a co-activator taking part in gene transcription, involved in pre-mRNA splicing, and regulating cell cycle. Tumorigenesis is closely correlated with DNA damage and the repair disorder. Recently, we demonstrated that Tudor-SN is involved in tumorigenesis, meanwhile, it also potentially participated in DNA damage and repair. Based on these previous data, in the present study, we will investigate the underlying molecular mechanisms of Tudor-SN on enhancing the histone acetylation and causing chromatin remodeling. It is likely due to the recruitment of protein or H3.3/H2A.Z complex to the DNA strand break (DSB) sites, and facilitating the assembly of the protein complex taking part into the DNA repair. In addition, we noticed that Tudor-SN could cause G2/M arrest after X-ray irradiation, thus we will investigate the potential pathway of Tudor-SN caused cell cycle arrest. Furthermore, we will use Tudor-SN knockout mice and Tudor-SN transgenic mice, to illustrate the function of Tudor-SN on the resistance of radiation in vivo. Based on our study, The Tudor-SN protein is likely to be a potential target to reduce the clinical radiation resistance in cancer treatment.

Tudor-SN是多功能蛋白，本课题组对其进行了长期研究，已发现它参与调控基因转录、细胞周期调控等。辐射导致DNA损伤，是重要的致癌因素，我们前期研究发现Tudor-SN能与DNA修复蛋白，组蛋白H3.3/H2A.Z等结合，并可以促进受到X-ray辐射的细胞发生细胞周期阻滞，这提示Tudor-SN蛋白可通过多重调控作用，促进辐射后DNA修复能力，对细胞起到保护作用。本课题基于前期工作，1）深入探讨Tudor-SN如何通过调控染色质结构的改变，开放DNA损伤部位，促进DNA损伤修复；2）明确Tudor-SN蛋白诱导受到辐射损伤的细胞发生G2/M期周期阻滞，以及抗凋亡作用的信号通路和调控机制；3）利用Tudor-SN基因敲除小鼠（KO-小鼠）和Tudor-SN转基因小鼠（TG-小鼠），探讨Tudor-SN蛋白在小鼠体内抵抗辐射，促进DNA损伤修复的作用。

真核生物细胞中基因组的DNA损伤和修复时常发生，而DNA损伤应答过程的紊乱与肿瘤、衰老的发生、发展密切相关。高度致密的染色体结构妨碍了DNA损伤位点的识别和修复，而组蛋白乙酰化修饰在此发挥重要作用，通过染色体重塑形成松散开放的构象，使核小体处于松弛状态，进而暴露出DNA损伤部位，有利于DNA损伤修复。本研究集中探讨DNA损伤和修复过程中，Tudor-SN蛋白如何与其它蛋白相互作用，通过调控组蛋白乙酰化修饰等，影响核染色质的高级结构，促进DNA损伤后修复。.在我们的研究中发现IR诱导DNA发生损伤后Tudor-SN被PARP1激活并募集到损伤部位，通过与染色质重塑因子SMARCA5和组蛋白转移酶GCN5的共同作用，影响组蛋白的乙酰化促进染色质的松弛，利于修复蛋白在损伤部位聚集。染色质结构的改变也进一步激活ATM及其下游通路，促进G2/M期阻滞及DNA修复机制的进行。