Kobayashi Junya
Department of Oral and Maxillofacial Radiology, Graduate School of Biomedical Sciences, Hiroshima University, Japan.
J Radiat Res. 2004 Dec;45(4):473-8. doi: 10.1269/jrr.45.473.
DNA double-strand breaks represent the most potentially serious damage to a genome, and hence, many repair proteins are recruited to DNA damage sites by as yet poorly characterized sensor mechanisms. We clarified that NBS1 physically interacts with gamma-H2AX to form nuclear foci at DNA damage sites. The fork-head associated (FHA) and the BRCA1 C-terminal domains (BRCT) of NBS1 are essential for this physical interaction and focus formation of NBS1 in response to DNA damage. The inhibition of this interaction by introduction of anti-gamma-H2AX antibody into cells abolishes NBS1 foci formation in response to DNA damage. Consequently, the FHA/BRCT domain is likely to have a crucial role for both binding to histone and for re-localization of the NBS1/hMRE11/hRAD50 complex to the vicinity of DNA damage. Moreover, the foci formation of DNA repair-related proteins containing BRCT domain, such as BRCA1, requires the interaction with gamma-H2AX in response to DNA damage. These findings indicate that the physical interaction between gamma-H2AX and DNA repair-related proteins is indispensable for the recruitment of these proteins. Further, it was recently reported that the NBS1/hMRE11/hRAD50 complex has a crucial role for both the recruitment of ATM to DNA damage sites and the subsequent activation of ATM. Therefore, both gamma-H2AX and the NBS1/hMRE11/hRAD50 complex might function for the initial recognition of DNA damage.
DNA双链断裂对基因组而言是最具潜在严重性的损伤，因此，许多修复蛋白通过目前尚未完全明确的传感机制被招募至DNA损伤位点。我们阐明了NBS1与γ-H2AX发生物理相互作用，从而在DNA损伤位点形成核灶。NBS1的叉头相关（FHA）结构域和BRCA1 C末端结构域（BRCT）对于这种物理相互作用以及NBS1响应DNA损伤时形成核灶至关重要。通过向细胞中引入抗γ-H2AX抗体来抑制这种相互作用，可消除NBS1响应DNA损伤时形成核灶的现象。因此，FHA/BRCT结构域可能对于结合组蛋白以及将NBS1/hMRE11/hRAD50复合物重新定位至DNA损伤附近均起着关键作用。此外，含有BRCT结构域的DNA修复相关蛋白（如BRCA1）形成核灶，在响应DNA损伤时需要与γ-H2AX相互作用。这些发现表明，γ-H2AX与DNA修复相关蛋白之间的物理相互作用对于这些蛋白的募集不可或缺。此外，最近有报道称，NBS1/hMRE11/hRAD50复合物对于将ATM募集至DNA损伤位点以及随后激活ATM均起着关键作用。因此，γ-H2AX和NBS1/hMRE11/hRAD50复合物可能在DNA损伤的初始识别中发挥作用。
