McIlwraith Michael J, Vaisman Alexandra, Liu Yilun, Fanning Ellen, Woodgate Roger, West Stephen C
Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Herts, EN6 3LD, United Kingdom.
Mol Cell. 2005 Dec 9;20(5):783-92. doi: 10.1016/j.molcel.2005.10.001.
Stalled replication forks pose a serious threat to genome integrity. To overcome the catastrophic consequences associated with fork demise, translesion synthesis (TLS) polymerases such as poleta promote DNA synthesis past lesions. Alternatively, a stalled fork may collapse and undergo repair by homologous recombination. By using fractionated cell extracts and purified recombinant proteins, we show that poleta extends DNA synthesis from D loop recombination intermediates in which an invading strand serves as the primer. Extracts from XP-V cells, which are defective in poleta, exhibit severely reduced D loop extension activity. The D loop extension activity of poleta is unusual, as this reaction cannot be promoted by the replicative DNA polymerase delta or by other TLS polymerases such as poliota. Moreover, we find that poleta interacts with RAD51 recombinase and RAD51 stimulates poleta-mediated D loop extension. Our results indicate a dual function for poleta at stalled replication forks: the promotion of translesion synthesis and the reinitiation of DNA synthesis by homologous recombination repair.
停滞的复制叉对基因组完整性构成严重威胁。为了克服与复制叉消亡相关的灾难性后果，诸如聚合酶η等跨损伤合成（TLS）聚合酶促进越过损伤的DNA合成。另外，停滞的复制叉可能会崩溃并通过同源重组进行修复。通过使用分级分离的细胞提取物和纯化的重组蛋白，我们发现聚合酶η从D环重组中间体延伸DNA合成，其中侵入链作为引物。来自聚合酶η有缺陷的着色性干皮病变种（XP-V）细胞的提取物表现出严重降低的D环延伸活性。聚合酶η的D环延伸活性是不同寻常的，因为这种反应不能由复制性DNA聚合酶δ或其他TLS聚合酶如聚合酶ι来促进。此外，我们发现聚合酶η与RAD51重组酶相互作用，并且RAD51刺激聚合酶η介导的D环延伸。我们的结果表明聚合酶η在停滞的复制叉处具有双重功能：促进跨损伤合成以及通过同源重组修复重新启动DNA合成。
