Yang Yang, Gao Yanzhe, Mutter-Rottmayer Liz, Zlatanou Anastasia, Durando Michael, Ding Weimin, Wyatt David, Ramsden Dale, Tanoue Yuki, Tateishi Satoshi, Vaziri Cyrus
Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC.
Oncology Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China.
J Cell Biol. 2017 Oct 2;216(10):3097-3115. doi: 10.1083/jcb.201702006. Epub 2017 Aug 23.
The mechanisms by which neoplastic cells tolerate oncogene-induced DNA replication stress are poorly understood. Cyclin-dependent kinase 2 (CDK2) is a major mediator of oncogenic DNA replication stress. In this study, we show that CDK2-inducing stimuli (including Cyclin E overexpression, oncogenic RAS, and WEE1 inhibition) activate the DNA repair protein RAD18. CDK2-induced RAD18 activation required initiation of DNA synthesis and was repressed by p53. RAD18 and its effector, DNA polymerase κ (Polκ), sustained ongoing DNA synthesis in cells harboring elevated CDK2 activity. RAD18-deficient cells aberrantly accumulated single-stranded DNA (ssDNA) after CDK2 activation. In RAD18-depleted cells, the G2/M checkpoint was necessary to prevent mitotic entry with persistent ssDNA. and cells were highly sensitive to the WEE1 inhibitor MK-1775 (which simultaneously activates CDK2 and abrogates the G2/M checkpoint). Collectively, our results show that the RAD18-Polκ signaling axis allows tolerance of CDK2-mediated oncogenic stress and may allow neoplastic cells to breach tumorigenic barriers.
肿瘤细胞耐受致癌基因诱导的DNA复制应激的机制目前尚不清楚。细胞周期蛋白依赖性激酶2（CDK2）是致癌性DNA复制应激的主要介质。在本研究中，我们发现诱导CDK2的刺激因素（包括细胞周期蛋白E过表达、致癌性RAS和WEE1抑制）可激活DNA修复蛋白RAD18。CDK2诱导的RAD18激活需要DNA合成的起始，并受到p53的抑制。RAD18及其效应因子DNA聚合酶κ（Polκ）在CDK2活性升高的细胞中维持正在进行的DNA合成。CDK2激活后，RAD18缺陷细胞异常积累单链DNA（ssDNA）。在RAD18缺失的细胞中，G2/M期检查点对于防止携带持续性ssDNA进入有丝分裂是必要的。而且，这些细胞对WEE1抑制剂MK-1775（其同时激活CDK2并消除G2/M期检查点）高度敏感。总之，我们的结果表明，RAD18-Polκ信号轴使细胞能够耐受CDK2介导的致癌应激，并可能使肿瘤细胞突破致瘤屏障。
