Abstract：
Coordination of enzymatic activities in the course of base excision repair (BER) is essential to ensure complete repair of damaged bases. Two major mechanisms underlying the coordination of BER are known today: the \"passing the baton\" model and a model of preassembled stable multiprotein repair complexes called \"repairosomes.\" In this work, we aimed to elucidate the coordination between human apurinic/apyrimidinic (AP) endonuclease APE1 and DNA polymerase Polβ in BER through studying an impact of APE1 on Polβ-catalyzed nucleotide incorporation into different model substrates that mimic different single-strand break (SSB) intermediates arising along the BER pathway. It was found that APE1\'s impact on separate stages of Polβ\'s catalysis depends on the nature of a DNA substrate. In this complex, APE1 removed 3\' blocking groups and corrected Polβ-catalyzed DNA synthesis in a coordinated manner. Our findings support the hypothesis that Polβ not only can displace APE1 from damaged DNA within the \"passing the baton\" model but also performs the gap-filling reaction in the ternary complex with APE1 according to the \"repairosome\" model. Taken together, our results provide new insights into coordination between APE1 and Polβ during the BER process.
摘要：
碱基切除修复（BER）过程中酶活性的协调对于确保受损碱基的完全修复至关重要。目前已知BER协调的两种主要机制：“传递指挥棒”模型和预组装的稳定多蛋白修复复合物模型，称为“repairosomes”。“在这项工作中，我们旨在通过研究APE1对Polβ催化的核苷酸掺入不同模型底物的影响来阐明BER中人嘌呤/嘧啶（AP）内切核酸酶APE1与DNA聚合酶Polβ之间的协同作用，这些底物模拟了沿着BER途径产生的不同单链断裂（SSB）中间体。发现APE1对Polβ催化的不同阶段的影响取决于DNA底物的性质。在这个复杂的，APE1去除了3个封闭基团，并以协调的方式校正了Polβ催化的DNA合成。我们的发现支持以下假设：Polβ不仅可以在“通过指挥棒”模型中从受损DNA中置换APE1，而且还可以根据“repairosome”模型在与APE1的三元复合物中进行间隙填充反应。一起来看,我们的结果为BER过程中APE1和Polβ之间的协调提供了新的见解。
