Dmitry Sutormin, Alina Galivondzhyan, Olga Musharova, Dmitrii Travin and Konstantin Severinov published a preprint “Interaction Between Transcribing RNA Polymerase and Topoisomerase I Prevents R-loop Formation in E. coli” at bioRxiv. The researchers show that topoisomerase I (TopoI) of Escherichia coli (EcTopoI) is co-localized, genome-wide, with RNA polymerase (RNAP) in transcription units. Pull-down experiments directly show that the two enzymes interact in vivo. Using ChIP-Seq and Topo-Seq, the researchers demonstrate that EcTopoI is enriched and in and upstream of highly-active transcription units, indicating that EcTopoI relaxes negative supercoiling generated by transcription. Moreover, uncoupling of the RNAP-EcTopoI interaction is toxic for cells and leads to excessive negative plasmid supercoiling. Furthermore, the overexpression of C-terminal domain (CTD) of RNAP leads to R-loops accumulation genome-wide, indicating that the RNAP-EcTopoI interaction is required for prevention of R-loops formation. Full text of the preprint is available here.