Rapid, direct detection of bacterial Topoisomerase 1-DNA adducts by RADAR/ELISA

Abstract

1 Topoisomerases are proven drug targets, but antibiotics that poison bacterial 2 Topoisomerase 1 (Top1) have yet to be discovered. We have developed a rapid and 3 direct assay for quantification of Top1-DNA adducts that is suitable for high throughput 4assays. Adducts are recovered by "RADAR fractionation", a quick, convenient 5 approach in which cells are lysed in chaotropic salts and detergent and nucleic acids 6and covalently bound adducts then precipitated with alcohol. Here we show that 7 RADAR fractionation followed by ELISA immunodetection can quantify adducts formed 8 by wild-type and mutant Top1 derivatives encoded by two different bacterial pathogens, 9Y. pestis and M. tuberculosis, expressed in E. coli or M. smegmatis, respectively. For 10 both enzymes, quantification of adducts by RADAR/ELISA produces results comparable 11to the more cumbersome classical approach of CsCl density gradient fractionation. The 12experiments reported here establish that RADAR/ELISA assay offers a simple way to 13 characterize Top1 mutants and analyze kinetics of adduct formation and repair. They 14 also provide a foundation for discovery and optimization of drugs that poison bacterial 15Top1 using standard high-throughput approaches. 16 17

Topoisomerase Assays

“…Efforts to identify potent small molecule inhibitors of bacterial Type IA enzymes have met with only limited success (Nagaraja, Godbole, Henderson, & Maxwell, 2017). Screens of large compound libraries using high‐throughput RADAR assays may enable identification of such compounds in the relatively near future (Sinha et al., 2020).…”