Article ID Journal Published Year Pages File Type
2048645 FEBS Letters 2011 7 Pages PDF
Abstract

Type II topoisomerases (Topo II) are unique enzymes that change the DNA topology by catalyzing the passage of two double-strands across each other by using the energy from ATP hydrolysis. In vitro, human Topo II relaxes positive supercoiled DNA around 10-fold faster than negative supercoiled DNA. By using atomic force microscopy (AFM) we found that human Topo II binds preferentially to DNA cross-overs. Around 50% of the DNA crossings, where Topo II was bound to, presented an angle in the range of 80–90°, suggesting a favored binding geometry in the chiral discrimination by Topo II. Our studies with AFM also helped us visualize the dynamics of the unknotting action of Topo II in knotted molecules.

► Human Topo II binds preferentially to DNA cross-overs. ► 50% of the DNA crossings where Topo II was bound had an angle in the range of 80–90°. ► We observed the untangling action of human Topo II on knotted DNA molecules.

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