Identification of Escherichia coli processing activities for covalent topoisomerase‐DNA complexes

DNA topoisomerases are ubiquitous enzymes that modify the topological state of the DNA by introducing single‐ or double‐strand DNA breaks, passing another DNA strand or a double helix through the break, and resealing the break. In the DNA cleavage step, a transient covalent phosphotyrosine linkage is formed between the enzyme and the cleaved DNA. Many anti‐cancer and anti‐bacterial drugs currently used in therapy target topoisomerases stabilizing the covalent enzyme‐DNA intermediate (cleavage complex). Stabilization of topoisomerase cleavage complexes triggers cellular DNA damage responses. These responses include the repair of strand breaks by homologous recombination and may also involve the processing of protein covalently bound to the DNA by endonuclease and phosphodiesterase activities. These endonuclease and phosphodiesterase activities have been identified in human and yeast, but not in bacteria. This work aims to identify Escherichia coli gene products that can process the topoisomerase protein covalently bound to cleaved DNA by genetic and biochemical experiments. As human tyrosyl‐DNA‐phosphodiesterases have been proposed as a cotarget for anticancer therapy, E. coli processing activities for topoisomerase‐DNA covalent complex may potentially serve as cotargets for combination therapy with topoisomerase targeting antibacterial drugs. Research was funded by NIH grant R01 AI069313.