Ajuba, a novel regulator of the ATR response in human cells.

ATR依赖的DNA损伤反应(DDR)对基因组完整性是必不可少的，并构成 一个重要的肿瘤抑制系统。DNA复制应激与细胞 转化，并代表了导致哺乳动物肿瘤发生的一些早期事件。我们的 研究的重点是属于LIM家族的蛋白质，其特征是存在 在其C端的串联LIM结构域，我们发现这些结构域对于抑制 人类细胞的DNA损伤反应。具体地说，我们发现阿朱巴对 在未受干扰的细胞中有效抑制ATR途径。Ajuba的耗尽导致激活 ATR，紧随其后的是强大的细胞凋亡反应。 我们发现Ajuba与RPA复合体有关，RPA复合体本身是ATR激活的核心 并在体外检测到Ajuba与RPA70亚基之间存在直接的相互作用。 RPA70由OB寡核苷酸/寡糖结合(OB)折叠组成，对单个 ATR激活复合体的链DNA结合和组装。基于这些观察，我们 假设阿朱巴是S期不适当激活ATR的重要阻滞物 与RPA70直接交互。我们建议详细研究阿朱巴之间的直接接触 和RPA，并分析这种相互作用在人类细胞中的意义。我们的结果在意料之中 为了提高我们对人类细胞DNA损伤反应本身的调控的理解 与细胞转化和癌症的早期事件有关。

The ATR-dependent DNA damage response (DDR) is essential for genome integrity and constitutes an important tumor suppressive system. DNA replication stress has been linked to cellular transformation, and represents some of the early events leading to tumorigenesis in mammals. Our work has centered on proteins that are part of the `Zyxin' LIM family, characterized by the presence of tandem LIM domains at their C terminus, which we found were important for the repression of the DNA damage response in human cells. Specifically, we have discovered that Ajuba is essential for efficient repression of the ATR pathway in unperturbed cells. Depletion of Ajuba leads to activation of ATR, followed by a potent apoptotic response. We have discovered that Ajuba associates with the RPA complex, itself central to the ATR activation pathway, and have detected a direct interaction in vitro between Ajuba and the RPA70 subunit. RPA70 is composed of OB oligonucleotide/oligosaccharide-binding (OB) folds essential for single strand DNA binding and assembly of the ATR activation complex. Based on these observations, we hypothesize that Ajuba is an important repressor of inappropriate ATR activation in S phase through a direct interaction with RPA70. We are proposing to study in detail the direct contacts between Ajuba and RPA, and to analyze the significance of this interaction in human cells. Our results are expected to improve our understanding of the regulation of the DNA damage response in human cells, itself implicated in early events in cellular transformation and cancer.