Finger L David, Atack John M, Tsutakawa Susan, Classen Scott, Tainer John, Grasby Jane, Shen Binghui
Department of Chemistry, Centre for Chemical Biology, Krebs Institute, University of Sheffield, Sheffield, S3 7HF, UK,
Subcell Biochem. 2012;62:301-26. doi: 10.1007/978-94-007-4572-8_16.
Processing of Okazaki fragments to complete lagging strand DNA synthesis requires coordination among several proteins. RNA primers and DNA synthesised by DNA polymerase α are displaced by DNA polymerase δ to create bifurcated nucleic acid structures known as 5'-flaps. These 5'-flaps are removed by Flap Endonuclease 1 (FEN), a structure-specific nuclease whose divalent metal ion-dependent phosphodiesterase activity cleaves 5'-flaps with exquisite specificity. FENs are paradigms for the 5' nuclease superfamily, whose members perform a wide variety of roles in nucleic acid metabolism using a similar nuclease core domain that displays common biochemical properties and structural features. A detailed review of FEN structure is undertaken to show how DNA substrate recognition occurs and how FEN achieves cleavage at a single phosphate diester. A proposed double nucleotide unpairing trap (DoNUT) is discussed with regards to FEN and has relevance to the wider 5' nuclease superfamily. The homotrimeric proliferating cell nuclear antigen protein (PCNA) coordinates the actions of DNA polymerase, FEN and DNA ligase by facilitating the hand-off intermediates between each protein during Okazaki fragment maturation to maximise through-put and minimise consequences of intermediates being released into the wider cellular environment. FEN has numerous partner proteins that modulate and control its action during DNA replication and is also controlled by several post-translational modification events, all acting in concert to maintain precise and appropriate cleavage of Okazaki fragment intermediates during DNA replication.
冈崎片段的加工以完成滞后链DNA合成需要几种蛋白质之间的协调。由DNA聚合酶α合成的RNA引物和DNA被DNA聚合酶δ取代，以形成被称为5'-翼片的分叉核酸结构。这些5'-翼片由翼片内切核酸酶1（FEN）去除，FEN是一种结构特异性核酸酶，其依赖二价金属离子的磷酸二酯酶活性以极高的特异性切割5'-翼片。FEN是5'核酸酶超家族的范例，其成员在核酸代谢中发挥多种作用，使用具有共同生化特性和结构特征的相似核酸酶核心结构域。对FEN结构进行了详细综述，以展示DNA底物识别是如何发生的，以及FEN如何在单个磷酸二酯处实现切割。关于FEN讨论了一种提出的双核苷酸解配对陷阱（DoNUT），它与更广泛的5'核酸酶超家族相关。同三聚体增殖细胞核抗原蛋白（PCNA）通过在冈崎片段成熟过程中促进每种蛋白质之间的交接中间体来协调DNA聚合酶、FEN和DNA连接酶的作用，以最大化通量并最小化中间体释放到更广泛细胞环境中的后果。FEN有许多伴侣蛋白，它们在DNA复制过程中调节和控制其作用，并且还受几种翻译后修饰事件的控制，所有这些共同作用以在DNA复制过程中维持冈崎片段中间体的精确和适当切割。
