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DNA topoisomerase I acts as supercoiling sensor for transcription elongation in E. coli

ABSTRACT: During DNA transcription, RNA polymerase (RNAP) continuously unwinds and rewinds DNA, generating negative and positive supercoils upstream and downstream, respectively. Using single-particle cryo-EM, we elucidated how bacterial RNAP and DNA Topoisomerase I (TopoI), which relaxes negative supercoils, operate in close spatial proximity. TopoI binds to relaxed DNA upstream of RNAP and this involves a conformational switch in the functional domains. This suggests a sensory role awaiting the formation of negative supercoils. On DNA substrates mimicking negatively supercoiled DNA, TopoI threads one strand into the active site for cleavage and binds the complementary strand with an auxiliary domain. Transcriptomic and phenotypic analysis suggest that mutations affecting the conformational changes in TopoI impact gene expression control and operon polarity in bacteria. We propose a comprehensive model for DNA relaxation in proximity of active transcription.

ORGANISM(S): Escherichia coli

PROVIDER: GSE273976 | GEO | 2025/08/27

REPOSITORIES: GEO

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