Biology subjects

Martin Gonzalez, A.

Publications and source records attributed to Martin Gonzalez, A..

2 recordsLinked to original sources

bioRxiv2024

DNA supercoiling enhances DNA condensation by ParB proteins

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.

biophysics↗

bioRxiv2023

Dynamic ParB-DNA interactions initiate and maintain a partition condensate for bacterial chromosome segregation

In most bacteria, chromosome segregation is driven by the ParABS system where the CTPase protein ParB loads at the parS site to trigger the formation of a large partition complex. Here, we present in vitro studies of the partition complex for Bacillus subtilis ParB, using single-molecule fluorescence microscopy and AFM imaging to show that transient ParB-ParB bridges are essential for forming DNA condensates. Molecular Dynamics simulations confirm that condensation occurs abruptly at a critical concentration of ParB and show that multimerization is a prerequisite for forming the partition complex. Magnetic tweezer force spectroscopy on mutant ParB proteins demonstrates that CTP hydrolysis at the N-terminal domain is essential for DNA condensation. Finally, we show that transcribing RNA polymerases can steadily traverse the ParB-DNA partition complex. These findings uncover how ParB forms a stable yet dynamic partition complex for chromosome segregation that induces DNA condensation and segregation while enabling replication and transcription.

biophysics↗