Department of Biochemistry and Molecular Medicine, Faculty of Medicine, Université de Montréal, Québec H3T 1J4, Canada.
Departments of Internal Medicine, Molecular Genetics and Microbiology, and University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, NM 87131, USA.
Structure. 2022 Mar 3;30(3):371-385.e5. doi: 10.1016/j.str.2021.11.002. Epub 2021 Nov 26.
DNA ligases act in the final step of many DNA repair pathways and are commonly regulated by the DNA sliding clamp proliferating cell nuclear antigen (PCNA), but there are limited insights into the physical basis for this regulation. Here, we use single-particle cryoelectron microscopy (cryo-EM) to analyze an archaeal DNA ligase and heterotrimeric PCNA in complex with a single-strand DNA break. The cryo-EM structures highlight a continuous DNA-binding surface formed between DNA ligase and PCNA that supports the distorted conformation of the DNA break undergoing repair and contributes to PCNA stimulation of DNA ligation. DNA ligase is conformationally flexible within the complex, with its domains fully ordered only when encircling the repaired DNA to form a stacked ring structure with PCNA. The structures highlight DNA ligase structural transitions while docked on PCNA, changes in DNA conformation during ligation, and the potential for DNA ligase domains to regulate PCNA accessibility to other repair factors.
DNA 连接酶在许多 DNA 修复途径的最后一步发挥作用，通常受 DNA 滑动夹增殖细胞核抗原 (PCNA) 调控，但对于这种调控的物理基础了解有限。在这里，我们使用单颗粒冷冻电子显微镜 (cryo-EM) 分析了一种古细菌 DNA 连接酶和三聚体 PCNA 与单链 DNA 断裂的复合物。cryo-EM 结构突出了 DNA 连接酶和 PCNA 之间形成的连续 DNA 结合表面，该表面支持正在修复的 DNA 断裂的扭曲构象，并有助于 PCNA 对 DNA 连接的刺激。在复合物中，DNA 连接酶具有构象灵活性，只有当其环绕修复后的 DNA 以与 PCNA 形成堆叠环结构时，其结构域才完全有序。这些结构突出了 DNA 连接酶在与 PCNA 对接时的结构转变、连接过程中 DNA 构象的变化，以及 DNA 连接酶结构域调节 PCNA 对其他修复因子的可及性的潜力。
