DNA super coiling describes a higher-order DNA structure. It plays a significant role for the osmotic regulation of gene expression in bacteria and it is known that transcription from many bacterial promoters is sensitive to the level of DNA super coiling. Enzymes that regulate DNA super coiling are known as ‘topoisomerases’. These catalyze and guide the unknotting or unlinking of DNA by creating transient breaks in the DNA using a conserved tyrosine as the catalytic residue. The insertion of (viral) DNA into chromosomes and other forms of recombination can also require the action of topoisomerases. In order to maintain genomic integrity during the enzyme-mediated DNA cleavage event, topoisomerases form covalent bonds between active site tyrosine residues and the newly generated DNA termini. Please have a look at the presentation on this topic.

Shashank Katariya

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