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bioRxiv · 10.1101/2024.07.11.603076

DNA supercoiling enhances DNA condensation by ParB proteins

Martin Gonzalez, A.·Tisma, M.·Analikwu, B. T.·Barth, A.·Janissen, R.·Antar, H.·Kemps, G.·Gruber, S.·Dekker, C.
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Abstract

The ParABS system plays a critical role in bacterial chromosome segregation. The key component of this system, ParB, loads and spreads along DNA to form a local protein-DNA condensate known as a partition complex. As bacterial chromosomes are heavily supercoiled due to the continuous action of RNA polymerases, gyrases, and nucleoid-associated proteins, it is important to study the impact of DNA supercoiling on the ParB-DNA partition complex formation. Here, we use an in vitro single- molecule assay to visualize ParB on supercoiled DNA. Unlike most DNA-binding proteins, individual ParB proteins are found to not pin plectonemes on supercoiled DNA, but freely diffuse along supercoiled DNA. We find that DNA supercoiling enhances ParB-DNA condensation which initiates at lower ParB concentrations than on DNA that is torsionally relaxed. ParB proteins induce a DNA- protein condensate that strikingly absorbs all supercoiling writhe. Our findings provide mechanistic insights that have important implications for our understanding of bacterial chromosome organization and segregation.

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Martin Gonzalez, A., Tisma, M., Analikwu, B. T., Barth, A., Janissen, R., Antar, H., Kemps, G., Gruber, S., Dekker, C.. 2024-07-13. DNA supercoiling enhances DNA condensation by ParB proteins. https://doi.org/10.1101/2024.07.11.603076

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