Montecucco A, Rossi R, Ferrari G, Scovassi A I, Prosperi E, Biamonti G
Istituto di Genetica Biochimica ed Evoluzionistica, Consiglio Nazionale delle Ricerche, 27100 Pavia, Italy.
Mol Biol Cell. 2001 Jul;12(7):2109-18. doi: 10.1091/mbc.12.7.2109.
In eukaryotic cells DNA replication occurs in specific nuclear compartments, called replication factories, that undergo complex rearrangements during S-phase. The molecular mechanisms underlying the dynamics of replication factories are still poorly defined. Here we show that etoposide, an anticancer drug that induces double-strand breaks, triggers the redistribution of DNA ligase I and proliferating cell nuclear antigen from replicative patterns and the ensuing dephosphorylation of DNA ligase I. Moreover, etoposide triggers the formation of RPA foci, distinct from replication factories. The effect of etoposide on DNA ligase I localization is prevented by aphidicolin, an inhibitor of DNA replication, and by staurosporine, a protein kinase inhibitor and checkpoints' abrogator. We suggest that dispersal of DNA ligase I is triggered by an intra-S-phase checkpoint activated when replicative forks meet topoisomerase II-DNA--cleavable complexes. However, etoposide treatment of ataxia telangiectasia cells demonstrated that ataxia-telangiectasia-mutated activity is not required for the disassembly of replication factories and the formation of replication protein A foci.
在真核细胞中，DNA复制发生在特定的核区室，即所谓的复制工厂，这些复制工厂在S期会经历复杂的重排。复制工厂动态变化背后的分子机制仍不清楚。在此我们表明，依托泊苷，一种诱导双链断裂的抗癌药物，会引发DNA连接酶I和增殖细胞核抗原从复制模式的重新分布以及随之而来的DNA连接酶I的去磷酸化。此外，依托泊苷会引发RPA焦点的形成，这与复制工厂不同。DNA复制抑制剂阿非科林以及蛋白激酶抑制剂和检查点消除剂星形孢菌素可阻止依托泊苷对DNA连接酶I定位的影响。我们认为，当复制叉遇到拓扑异构酶II-DNA可切割复合物时激活的S期内检查点会触发DNA连接酶I的分散。然而，依托泊苷处理共济失调毛细血管扩张症细胞表明，共济失调毛细血管扩张症突变活性对于复制工厂的解体和复制蛋白A焦点的形成并非必需。
