Department of Cancer Biology and Genetics, Cancer Research Institute, Queen's University, Kingston, ON, Canada.
Cell Cycle. 2010 Feb 1;9(3):548-56. doi: 10.4161/cc.9.3.10553.
The interaction between the 911 complex, via Rad9A, and Claspin is required for activation of the Chk1-mediated checkpoint response, along with ATR, TopBp1, and the 911 clamp loader complex Rad17/RFC. Despite the importance of the Rad9A-Claspin interaction in the cell cycle, this interaction has yet to be characterized. In this work we show this interaction persists in a variety of different conditions. During the course of this study we also determined the nuclear localization of Rad9A affected the localization of the Claspin protein, leading us to the conclusion that Rad9A is able to affect Claspin cellular localization. This was verified experimentally using a Rad9A-null cell line and reconstitution of Wt Rad9A. We also show that in meS cells the Rad9A paralog, Rad9B, is also capable of affecting Claspin localization. Together, these data suggest that Rad9 plays a role in locating Claspin to sites of DNA damage, facilitating its role during the Chk1-mediated checkpoint response. Since disruption of both Rad9A and Claspin has been shown to abolish Chk1 activation, we postulate that Rad9A-mediated Claspin localization is a vital step during checkpoint activation.
911 复合物通过 Rad9A 与 Claspin 的相互作用，与 ATR、TopBp1 和 911 夹子加载器复合物 Rad17/RFC 一起，是激活 Chk1 介导的检查点反应所必需的。尽管 Rad9A-Claspin 相互作用在细胞周期中非常重要，但这一相互作用尚未被描述。在这项工作中，我们证明了这种相互作用在各种不同的条件下都能持续存在。在研究过程中，我们还确定了 Rad9A 的核定位影响了 Claspin 蛋白的定位，这使我们得出结论，Rad9A 能够影响 Claspin 的细胞定位。这一点通过使用 Rad9A 缺失细胞系和 Wt Rad9A 的重建实验得到了验证。我们还表明，在 meS 细胞中，Rad9 的同源物 Rad9B 也能够影响 Claspin 的定位。这些数据表明，Rad9 在将 Claspin 定位到 DNA 损伤部位方面发挥作用，从而促进其在 Chk1 介导的检查点反应中的作用。由于破坏 Rad9A 和 Claspin 都已被证明会废除 Chk1 的激活，我们推测 Rad9A 介导的 Claspin 定位是检查点激活过程中的一个重要步骤。
