Bacterial H-NS forms nucleoprotein filaments that spread on DNA and bridge distant DNA sites. H-NS filaments co-localize with sites of Rho-dependent termination in Escherichia coli, but their direct effects on transcriptional pausing and termination are untested. In this study, we report that bridged H-NS filaments strongly increase pausing by E. coli RNA polymerase at a subset of pause sites with high potential for backtracking. Bridged but not linear H-NS filaments promoted Rho-dependent termination by increasing pause dwell times and the kinetic window for Rho action. By observing single H-NS filaments and elongating RNA polymerase molecules using atomic force microscopy, we established that bridged filaments surround paused complexes. Our results favor a model in which H-NS-constrained changes in DNA supercoiling driven by transcription promote pausing at backtracking-susceptible sites. Our findings provide a mechanistic rationale for H-NS stimulation of Rho-dependent termination in horizontally transferred genes and during pervasive antisense and noncoding transcription in bacteria.
Bacteria, Bacterial Proteins, Base Sequence, DNA-Binding Proteins, DNA-Directed RNA Polymerases, RNA, Bacterial, Transcription Termination, Genetic
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Kotlajich, Matthew V.; Hron, Daniel R.; Boudreau, Beth A.; Sun, Zhiqiang; Lyubchenko, Yuri L.; and Landick, Robert, "Bridged filaments of histone-like nucleoid structuring protein pause RNA polymerase and aid termination in bacteria." (2015). Journal Articles: Pharmaceutical Sciences. Paper 7.