Novel DNA damage responses and repair regulated by poly-ADP ribosylation and chromatin remodeling

利用激光微照射人体活细胞和蛋白质组学方法鉴定DNA损伤位点募集的蛋白质复合物，分析和鉴定了人体细胞内蛋白质对DNA损伤的反应。对于DNA单链断裂，我们已经鉴定出两种具有DNA末端和外核酸酶活性的新型人类蛋白质，它们通过在DNA缺口处产生间隙来激活聚adp核糖聚合酶1 （PARP1）。对于DNA双链断裂（DSB），我们发现了一个属于ISWI家族的atp依赖性染色质重塑复合体，CHRAC，这是在DSB上加载KU复合体所必需的。特别是，通过产生DSB的化学试剂处理细胞，ACF1与KU70的结合更加紧密，并启动DSB的非同源末端连接。因此，我们发现染色质重塑对于DNA链断裂修复的开始是必不可少的。

Using laser micro-irradiation of living human cell and identification of protein complexes recruited to DNA damaged site by proteomics, we have analyzed and identified DNA damage response of proteins within human cell. For DNA single-strand breaks we have identified two novel human proteins with DNA end-and exo-nuclease activities, which activate poly(ADP-ribose polymerase 1 (PARP1)by creating gap at a nick in DNA. For DNA double-strand breaks (DSB)we identified an ATP-dependent chromatin remodeling complex belonging to ISWI family, CHRAC, which is required for the loading of KU complex at DSB. Especially, ACF1 becomes bound to KU70 more tightly by treatment of cells with chemical agents creating DSB and initiates non-homologous end joining of DSB. Thus, we showed that chromatin remodeling is essential for the initiation of repair of DNA strand breaks.