Gao Ying, Li Changling, Wei Leizhen, Teng Yaqun, Nakajima Satoshi, Chen Xiukai, Xu Jianquan, Leger Brittany, Ma Hongqiang, Spagnol Stephen T, Wan Yong, Dahl Kris Noel, Liu Yang, Levine Arthur S, Lan Li
School of Medicine, Tsinghua University, Beijing, China.
University of Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania.
Cancer Res. 2017 May 15;77(10):2674-2685. doi: 10.1158/0008-5472.CAN-16-3128. Epub 2017 Apr 17.
DNA single-strand breaks (SSB) are the most common form of DNA damage, requiring repair processes that to initiate must overcome chromatin barriers. The FACT complex comprised of the SSRP1 and SPT16 proteins is important for maintaining chromatin integrity, with SSRP1 acting as an histone H2A/H2B chaperone in chromatin disassembly during DNA transcription, replication, and repair. In this study, we show that SSRP1, but not SPT16, is critical for cell survival after ionizing radiation or methyl methanesulfonate-induced single-strand DNA damage. SSRP1 is recruited to SSB in a PARP-dependent manner and retained at DNA damage sites by N-terminal interactions with the DNA repair protein XRCC1. Mutational analyses showed how SSRP1 function is essential for chromatin decondensation and histone H2B exchange at sites of DNA strand breaks, which are both critical to prime chromatin for efficient SSB repair and cell survival. By establishing how SSRP1 facilitates SSB repair, our findings provide a mechanistic rationale to target SSRP1 as a general approach to selectively attack cancer cells. .
DNA单链断裂（SSB）是最常见的DNA损伤形式，其修复过程启动时必须克服染色质屏障。由SSRP1和SPT16蛋白组成的FACT复合物对于维持染色质完整性很重要，在DNA转录、复制和修复过程中，SSRP1在染色质解聚中作为组蛋白H2A/H2B伴侣发挥作用。在本研究中，我们发现，对于电离辐射或甲磺酸甲酯诱导的单链DNA损伤后的细胞存活，SSRP1而非SPT16至关重要。SSRP1以PARP依赖的方式被招募到SSB，并通过与DNA修复蛋白XRCC1的N端相互作用保留在DNA损伤位点。突变分析表明，SSRP1的功能对于染色质解聚和DNA链断裂位点的组蛋白H2B交换至关重要，这两者对于启动染色质进行有效的SSB修复和细胞存活都至关重要。通过确定SSRP1如何促进SSB修复，我们的研究结果为将SSRP1作为一种选择性攻击癌细胞的通用方法提供了机制依据。
