DNA-Stimulated Liquid-Liquid phase separation by eukaryotic topoisomerase ii modulates catalytic function.

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Type II topoisomerases (topo IIs) are crucial enzymes that manage DNA topology.
• Their precise mechanisms for controlling DNA linking and unlinking remain incompletely understood.
• Understanding topo II function is vital for processes like replication, transcription, and chromosome condensation.

Purpose of the Study:

• To investigate the role of protein concentration and phase separation in eukaryotic type IIA topoisomerase activity.
• To elucidate how topo IIs switch between DNA unlinking and catenation.
• To identify structural determinants of topo II-mediated DNA topology modulation.

Main Methods:

• Observation of eukaryotic type IIA topoisomerase behavior at physiological concentrations.
• Analysis of DNA-induced condensation and fluidization of enzyme assemblies.
• Assessment of topological outcomes (catenation, decatenation, knotting) using wild-type and mutant topo IIs.

Main Results:

• Eukaryotic type IIA topoisomerases coalesce into condensed bodies at physiological concentrations.
• DNA stimulates this condensation, imparting liquid-like properties to the assemblies.
• Condensation triggers a switch from DNA unlinking to catenation, dependent on an unstructured C-terminal region.

Conclusions:

• Local protein concentration and phase separation are key regulators of type II topoisomerase activity.
• These mechanisms explain how topo IIs can both create and dissolve DNA links.
• Regulated phase separation by topo IIs contributes to their diverse roles in genome maintenance and organization.