StaR Is a Positive Regulator of Topoisomerase I Activity Involved in Supercoiling Maintenance in .

The DNA topoisomerases gyrase and topoisomerase I as well as the nucleoid-associated protein HU maintain supercoiling levels in , a main human pathogen. Here, we characterized, for the first time, a topoisomerase I regulator protein (StaR). In the presence of sub-inhibitory novobiocin concentrations, which inhibit gyrase activity, higher doubling times were observed in a strain lacking , and in two strains in which StaR was over-expressed either under the control of the ZnSO-inducible P promoter (strain ΔP) or of the maltose-inducible P promoter (strain ΔpLS1ROM.