AI Insight
Type II topoisomerases manage DNA topology by passing one DNA strand through a break in another strand, but the precise geometry of this interaction has been difficult to capture. Researchers combined single-molecule experiments with computer simulations to determine the three-dimensional orientation and conformation that DNA strands must adopt for this strand-passage reaction to occur. They discovered that two different topoisomerases, one from E. coli and one from M. mazei, prefer distinct DNA crossing geometries, which explains their different biological activities and functions.
Why it matters
Understanding how topoisomerases select and process specific DNA structures provides insight into essential cellular processes like DNA replication and chromosome segregation. This knowledge could inform the development of better antibiotics and anticancer drugs, as topoisomerases are major therapeutic targets, and the methodology developed can be applied to study other enzyme-DNA interactions.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Type II topoisomerases (topo IIs) are essential enzymes that regulate DNA topology through a strand-passage mechanism in which a duplex DNA (transfer-segment) is passed through a transiently cleaved second duplex DNA (gate-segment). Biochemical and structural approaches have revealed critical details of the binding and cleavage of the gate-segment DNA. However, capture of the transfer-segment DNA has proven more difficult to resolve due to the transient nature of the interaction. Nonetheless, selection of the transfer segment with a specific conformation or orientation relative to the gate segment is predicted to govern aspects of topo II activity, including chiral discrimination and the ability to reduce topological complexity below equilibrium. To determine the conformation and orientation of the transfer-segment relative to the gate segment, we combined experimental single-molecule measurements of topo II unlinking a single DNA crossing with Brownian dynamics simulations of the DNA crossing. By correlating the unlinking rate with the geometric features of the DNA crossing, we obtain the complete three-dimensional preferred crossing geometry for strand passage. Strikingly, the preferred crossing geometries for Escherichia coli topoisomerase IV and Methanosarcina mazei topoisomerase VI are distinct and provide structural models of the DNA synapse selected for strand passage along with a mechanistic basis for their differing activities and biological functions. The approach we develop is generalizable, providing unique insights into the kinetic selection of DNA synapse structure.
Source: Type II topoisomerase substrate geometry revealed through combined experiment and computation.