Transcription-driven DNA supercoiling activates bacterial chromatin at a distance - Archive ouverte HAL
Article Dans Une Revue BioRxiv Année : 2023

Transcription-driven DNA supercoiling activates bacterial chromatin at a distance

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Abstract In all living cells, genomic DNA is compacted through interactions with dedicated proteins and/or the formation of plectonemic coils. In bacteria, DNA compaction is achieved dynamically, coordinated with dense and constantly changing transcriptional activity. H-NS, a major bacterial nucleoid structuring protein, is of special interest due to its interplay with RNA polymerase. H-NS:DNA nucleoprotein filaments inhibit transcription initiation by RNA polymerase. However, the discovery that genes silenced by H-NS can be activated by transcription originating from neighboring regions has suggested that elongating RNA polymerases can disassemble H-NS:DNA filaments. In this study, we present evidence that transcription-induced counter-silencing does not require transcription to reach the silenced gene; rather, it exerts its effect at a distance. Counter-silencing is suppressed by introducing a DNA gyrase binding site within the intervening segment, suggesting that the long-range effect results from transcription-driven positive DNA supercoils diffusing toward the silenced gene. We propose a model wherein H-NS:DNA complexes form in vivo on negaXvely supercoiled DNA, with H-NS bridging the two arms of the plectoneme. Rotational diffusion of positive supercoils generated by neighbouring transcription will cause the H-NS-bound negatively-supercoiled plectoneme to “unroll” disrupting the H-NS bridges and releasing H-NS.

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hal-04770237 , version 1 (06-11-2024)

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Nara Figueroa-Bossi, Rocío Fernández-Fernández, Patricia Kerboriou, Philippe Bouloc, Josep Casadesús, et al.. Transcription-driven DNA supercoiling activates bacterial chromatin at a distance. BioRxiv, 2023, ⟨10.1101/2023.10.26.564199⟩. ⟨hal-04770237⟩
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