The role of BRCT domain in DNA damage response

基因组DNA受到电离辐射和DV等几种压力的DNA损伤。一旦DNA损伤进入基因组DNA，它们的细胞就会检测到这种损伤，并通过细胞周期检查点系统诱导生长停止来修复受损的DNA，由于DNA损伤在基因组DNA中的残留可能导致基因不稳定、肿瘤发生或细胞凋亡，因此阐明DNA损伤反应的机制非常重要。近年来，BRCT （BRCA1 C-Terminal）结构域在DNA损伤应答中得到了广泛的关注，因为一些DNA损伤应答因子通过其BRCT结构域实现蛋白-蛋白相互作用。然而，大多数BRCT结构域蛋白在DNA损伤应答中的作用尚不清楚，因此，我们通过蛋白质组学分析确定了与BRCT结构域相互作用的蛋白，并研究了它们在DNA损伤应答中的作用。Nijmegen综合征的相关基因产物NBS1通过FHA/BRCT结构域与γ - h2ax相互作用，这种相互作用是焦点形成不可或缺的。此外，FHA/BRCT结构域对于DNA修复的同源重组（Homologous Recombination， HR）活性也很重要。具有BRCT结构域的TopBP1依赖于DSB的产生与NBS1相互作用，这种相互作用对于TopBP1依赖DSB的焦点形成至关重要。此外，敲低TopBP1降低了HR活性和HR的姐妹染色单体交换，这表明TopBP1对HR有作用。此外，我们发现核蛋白与H2AX相互作用，而H2AX与NBS1的BRCT结构域相互作用。核蛋白与γ - h2ax在DNA损伤后相互作用。此外，siRNA敲低核蛋白会增加γ - h2ax和ATM底物的磷酸化，并增加对喜树碱（DNA损伤剂）的敏感性。此外，核仁蛋白敲除细胞的HR活性降低。因此，核蛋白也可能是HR的一个重要因素。因此，通过BRCT结构域的蛋白-蛋白相互作用可能对DNA损伤反应，特别是HR修复非常重要。由于DNA损伤反应机制被认为是肿瘤发生的屏障，我们有必要更详细地研究BRCT结构域在DNA损伤反应中的作用。少

Genome DNA suffers DNA damage by several stresses such as ionizing radiation and DV. Once DNA damage is generated into genome DNA, their cells detects this damage and induce growth arrest by cell cycle checkpoint system to repair damaged DNA, As the remain of DNA damage in genome DNA might lead to gene instability, tumorigenesis or apoptosis, it is much important to clarify the mechanism of DNA damage response. Recently, BRCT (BRCA1 C-Terminal) domain has been noticed in DNA damage response, bemuse some DNA damare response factors function by protein-protein interaction through their BRCT domain. However, the role of most BRCT domain proteins in DNA damage response is unknown Therefore, we identified interaction proteins with BRCT domain by proteomics analysis and investigated their the role of proteins in DNA damage response.NBS1, the responsible gene product for Nijmegen syndrome, interact with gamma-H2AX through FHA/BRCT domain, and this interaction is indispensable for focus format … More ion of NBS1/MRE11/RAD50 complex at DSB (DNA double-strand break) sites. Moreover, FHA/BRCT domain is also important for Homologous Recombination (HR) activity for DNA repair. TopBP1, which possesses BRCT domains, interacts with NBS1 dependently on the generation of DSB, and this interaction is essential to the DSB-dependent focus formation of TopBP1. Further, knockdown of TopBP1 reduced HR activity and sister chromatid exchange by HR, which suggests that TopBP1 function for HR. Furthermore, we identified nucleolin as a protein interacting with H2AX, which interact with BRCT domain of NBS1. Nucleolin interact with gamma-H2AX following generation of DNA damage. And, knockdown of nucleolin by siRNA increased gamma-H2AX and phosphorylation of ATM substrates and sensitivity to campthotecin (DNA damaging agent). Moreover, nucleolin knockdown cells showed decreases in HR activity. Thus, nuceloin might also be an important factor for HR. Therefore, the protein-protein interaction through BRCT domain could be much important for DNA damage response, particularly HR repair. As the mechanism of DNA damage response is suggested to be indispensable for barrier to tumorigenesis, we have to investigate more detailed role of BRCT domain in DNA damage response. Less