Nucleoid remodeling is a common stress response strategy in bacteria to protect their genetic material. This process is regulated by small proteins, known as NAPs or Nucleoid-Associated Proteins, which interact with DNA and play a key role in the organisation and regulation of the bacterial genome.
Using advanced conventional and single-molecule localization microscopy approaches, the I2SR group, in collaboration with F. Confalonieri’s team at I2BC, recently demonstrated that exposure to UV-C radiation or entry into stationary phase induces profound changes in the morphology and size of Deinococcus radiodurans nucleoids, as well as modifications in the mobility of the HU protein, the main NAP in this bacterium. Although both stresses cause rapid nucleoid compaction, HU diffusion decreases in stationary phase while it increases following UV-C, suggesting distinct underlying mechanisms.
In addition, they show that nucleoid remodeling following exposure to UV-C occurs in three distinct stages : rapid condensation associated with an increase in HU diffusion (most likely caused by release of HU from the genomic DNA), followed by a slower decompaction phase to restore normal nucleoid morphology accompanied by a return of HU mobility to normal values (as a result of reassembly of HU on the genomic DNA), before cell growth and division resume. These observations illustrate the diversity and complexity of nucleoid remodeling processes in bacteria and represent a first step towards understanding the mechanisms involved and notably the role of HU in this process.
Stress-induced nucleoid remodeling in Deinococcus radiodurans is associated with major changes in Heat Unstable (HU) protein dynamics. Vauclare P, Wulffelé J, Lacroix F, Servant P, Confalonieri F, Kleman JP, Bourgeois D, Timmins J. Nucleic Acids Res. 2024 ; 52(11):6406-6423.doi : 10.1093/nar/gkae379.
Contact : Pierre Vauclare & Joanna Timins, Integrated Imaging of Stress Response Group (IBS/I2SR)