Université de Strasbourg, CNRS, INSERM, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), Illkirch, France.
Department of Integrated Structural Biology, IGBMC, Illkirch, France.
Nat Commun. 2021 May 20;12(1):2962. doi: 10.1038/s41467-021-23136-6.
The human type IIA topoisomerases (Top2) are essential enzymes that regulate DNA topology and chromosome organization. The Topo IIα isoform is a prime target for antineoplastic compounds used in cancer therapy that form ternary cleavage complexes with the DNA. Despite extensive studies, structural information on this large dimeric assembly is limited to the catalytic domains, hindering the exploration of allosteric mechanism governing the enzyme activities and the contribution of its non-conserved C-terminal domain (CTD). Herein we present cryo-EM structures of the entire human Topo IIα nucleoprotein complex in different conformations solved at subnanometer resolutions (3.6-7.4 Å). Our data unveils the molecular determinants that fine tune the allosteric connections between the ATPase domain and the DNA binding/cleavage domain. Strikingly, the reconstruction of the DNA-binding/cleavage domain uncovers a linker leading to the CTD, which plays a critical role in modulating the enzyme's activities and opens perspective for the analysis of post-translational modifications.
人类 IIA 拓扑异构酶（Top2）是调节 DNA 拓扑结构和染色体组织的必需酶。Topo IIα 同工酶是癌症治疗中使用的抗肿瘤化合物的主要靶点，这些化合物与 DNA 形成三元切割复合物。尽管进行了广泛的研究，但关于这种大型二聚体组装体的结构信息仅限于催化结构域，这阻碍了对调控酶活性的变构机制以及其非保守 C 端结构域（CTD）的贡献的探索。在此，我们展示了不同构象下的全长人 Topo IIα 核蛋白复合物的 cryo-EM 结构，分辨率达到亚纳米级（3.6-7.4Å）。我们的数据揭示了精细调节 ATP 酶结构域和 DNA 结合/切割结构域之间变构连接的分子决定因素。引人注目的是，DNA 结合/切割结构域的重建揭示了一条通向 CTD 的连接链，该连接链在调节酶活性方面起着关键作用，并为分析翻译后修饰开辟了前景。
