Jab1依赖结合蛋白和去泛素化功能在DNA损伤反应中的双重作用研究

Jab1 regulates cancer cell proliferation, cell cycle, apoptosis and DNA damage response (DDR) by interacting with several key regulatory proteins. However, the mechanism of Jab1 in DDR remains to be determined. RAP80 is an important molecule in DDR. Our previous studies demonstrated that Jab1 presents a binding protein domain (MPN) and a deubiquitinating enzymes domain (JAMM). Moreover, we found that Jab1 interact with RAP80 in the early stage of DDR, while depletion of Jab1 induced accumulated ubiquitin in the late stage of DDR. Based on these findings, we hypothesized that Jab1 plays dual roles in DDR. Our study will be divided into three parts: (1) to illuminate the binding protein activity of Jab1 in recruiting DNA repair protein in the early stage of DDR. (2) to reveal the deubiquitination enzyme properties of Jab1 in the late stage of DDR. (3) to demonstrate the clinical significance of Jab1 and its associated proteins in DNA damage based therapies resistance in head and neck cancer. With experiments on the cellular level, mouse model and clinical level, we intend to elucidate the role of Jab1 in DDR, which will make a significant contribution to the expansion of Jab1 function, as well as providing the theoretical and experimental basis for interpreting the treatment response of head and neck cancer.

Jab1与多种蛋白相互作用，参与调控细胞增殖、细胞周期、凋亡和DNA损伤反应（DDR），但Jab1参与DDR的具体机制尚未明确。RAP80是介导DDR的重要分子。本课题组前期研究表明，Jab1具有蛋白质间结合的结构域MPN和去泛素化酶结构域JAMM。预实验发现：在DDR早期，Jab1可与RAP80结合；在DDR晚期，抑制Jab1能延缓RAP80的泛素化降解。因此，推测Jab1依赖其结合蛋白质和去泛素化功能在DDR中发挥双重作用。本项目拟深入探讨：（1）Jab1在DDR早期通过其结合蛋白质特性招募DNA修复因子聚集于DNA损伤位点；（2）Jab1在DDR晚期通过其去泛素化酶特性终止修复信号；（3）探讨Jab1及其相互作用蛋白与头颈癌放化疗敏感性的关系。在体外、体内、临床三个层面阐明Jab1调控DDR的分子机制，有助于拓展Jab1功能，为头颈癌放化疗抵抗问题提供理论依据和实验基础。

Jab1与多种蛋白相互作用，参与调控细胞增殖、细胞周期、凋亡和DNA损伤反应（DDR），但Jab1参与DDR的具体机制尚未明确。放化疗可以直接损伤细胞DNA，或者间接造成DNA的破坏，从而杀伤肿瘤细胞。放化疗耐受表现为肿瘤微环境对外部的抵抗，从而保护肿瘤细胞免受外界影响。本项目探索了头颈癌/鼻咽癌细胞富集区域、免疫细胞富集区内肿瘤异质性。在鼻咽癌微环境中，肿瘤细胞和免疫细胞对不同药物的敏感性也有差异。在头颈癌患者中，随着Jab1表达量增高，Lapatinib 的IC50也增高，表明肿瘤内Jab1表达量调控了肿瘤治疗敏感性。Jab1在癌症中异常高表达，与生存预后相关。错义突变是Jab1的主要突变类型。Jab1的表达与肿瘤突变负担（TMB）和微卫星不稳定性（MSI）呈正相关。Jab1表达与CD8+ T细胞浸润正相关，与癌相关成纤维细胞浸润负相关。外周循环CD8、NK和MONO细胞内Jab1表达量在经历一定周期的放疗治疗后有所升高，表明放化疗治疗对外周血中不同淋巴亚群中Jab1表达量有一定积极影响。Jab1信号网络主要参与核苷酸切除修复、DNA损伤识别和Cullin去Eddylation等生物学过程，说明这些过程可能影响了肿瘤微环境中不同细胞的DNA修复能力，进而影响肿瘤治疗的反应性。研究表明Jab1可以稳定DDR相关靶点FUBP-1，延长其降解速度。Jab1与FUBP-1启动子的结合，表明在DDR过程中Jab1转录水平促进靶基因的表达。本项目系统地探讨了Jab1通过DDR机制调控肿瘤治疗耐受，将为肿瘤DDR研究提供关键靶点信息，同时为临床转化研究提供治疗新策略。