DNA topoisimerase

 DNA topoisomerase plays an impotant role in breaking the phosophodiester bond by binding covalently onto the DNA backbone phosphate. It acst as a reversible nuclease. This whole process is a reversible one, whereby before the protein leaves, the phosophodiester bonds are re-made. There are two types of DNA topoisomerase, topoisomerase I and topoismerase II.