Structural basis for allosteric regulation of Human Topoisomerase IIα

The human type IIA topoisomerases (Top2) are essential enzymes that regulate DNA topology and chromosome organization. The Topo II alpha 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 II alpha nucleoprotein complex in different conformations solved at subnanometer resolutions (3.6-7.4 angstrom). 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. Type 2 DNA topoisomerases (Top2) regulates DNA topology during DNA replication, transcription, and chromosome segregation. Here the authors describe a complete structure of the catalytic core of the human Topo II alpha bound to DNA and etoposide, providing insight into the regulation of Topo II alpha activities and how opening of the DNA-gate is spatially connected to the ATPase domain.

Automated summary

Human type IIA topoisomerases play a crucial role in regulating DNA topology and chromosome organization. The isoform Topo II alpha is a key target for anti-cancer compounds, forming ternary cleavage complexes with DNA. This study provides cryo-EM structures of the entire Topo II alpha nucleoprotein complex, shedding light on the allosteric connections between different domains and the role of the non-conserved C-terminal domain in regulating enzyme activities.