Drexel University College of Medicine, Department of Pathology and Laboratory Medicine, Philadelphia, Pennsylvania, USA.
Cell Cycle. 2010 Sep 15;9(18):3798-806. doi: 10.4161/cc.9.18.13129. Epub 2010 Sep 25.
The Ku70/80 heterodimer is central to non-homologous end joining repair of DNA double-strand breaks and the Ku80 gene appears to be essential for human but not rodent cell survival. The Ku70/80 heterodimer is located at telomeres but its precise function in telomere maintenance is not known. In order to examine the role of Ku80 beyond DNA repair in more detail, we have taken a knockdown approach using a human fibroblast strain. Following targeted Ku80 knockdown, telomere defects are observed and the steady state levels of the TRF2 protein are reduced. Inhibitor studies indicate that this loss of TRF2 is mediated by the proteasome and degradation of TRF2 following Ku depletion appears to involve a decrease in chromatin binding of TRF2, suggesting that the Ku heterodimer enhances TRF2 chromatin association and that non-chromatin bound TRF2 is targeted to the proteasome.
Ku70/80 异二聚体是 DNA 双链断裂非同源末端连接修复的核心，Ku80 基因似乎对人类细胞而非啮齿动物细胞的存活至关重要。Ku70/80 异二聚体位于端粒，但它在端粒维持中的精确功能尚不清楚。为了更详细地研究 Ku80 在 DNA 修复之外的作用，我们使用人类成纤维细胞株进行了敲低研究。在靶向 Ku80 敲低后，观察到端粒缺陷，并且 TRF2 蛋白的稳态水平降低。抑制剂研究表明，TRF2 的这种丢失是由蛋白酶体介导的，并且 Ku 耗竭后 TRF2 的降解似乎涉及 TRF2 与染色质结合的减少，这表明 Ku 异二聚体增强了 TRF2 与染色质的结合，并且非染色质结合的 TRF2 被靶向蛋白酶体。
