DNA cleavage and opening reactions of human topoisomerase IIα are regulated via Mg2+-mediated dynamic bending of gate-DNA.

Lee S, Jung SR, Heo K, Byl JA, Deweese JE, Osheroff N, Hohng S
Proc Natl Acad Sci U S A. 2012 109 (8): 2925-30

PMID: 22323612 · PMCID: PMC3286967 · DOI:10.1073/pnas.1115704109

Topoisomerase II resolves intrinsic topological problems of double-stranded DNA. As part of its essential cellular functions, the enzyme generates DNA breaks, but the regulation of this potentially dangerous process is not well understood. Here we report single-molecule fluorescence experiments that reveal a previously uncharacterized sequence of events during DNA cleavage by topoisomerase II: nonspecific DNA binding, sequence-specific DNA bending, and stochastic cleavage of DNA. We have identified unexpected structural roles of Mg(2+) ions coordinated in the TOPRIM (topoisomerase-primase) domain in inducing cleavage-competent DNA bending. A break at one scissile bond dramatically stabilized DNA bending, explaining how two scission events in opposing strands can be coordinated to achieve a high probability of double-stranded cleavage. Clamping of the protein N-gate greatly enhanced the rate and degree of DNA bending, resulting in a significant stimulation of the DNA cleavage and opening reactions. Our data strongly suggest that the accurate cleavage of DNA by topoisomerase II is regulated through a tight coordination with DNA bending.

MeSH Terms (13)

Amino Acids, Acidic Antigens, Neoplasm Base Sequence Cations, Divalent DNA DNA-Binding Proteins DNA Breaks, Double-Stranded DNA Cleavage DNA Topoisomerases, Type II Humans Magnesium Molecular Sequence Data Nucleic Acid Conformation

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