Cytidine triphosphate promotes efficient ParB-dependent DNA condensation by facilitating one-dimensional spreading from parS

• Published in: bioRxiv
• Main Authors: Francisco De Asis Balaguer, Aicart-Ramos, Clara, Fisher, Gemma Lm, De Bragança, Sara, Pastrana, Cesar L, Dillingham, Mark S, Moreno-Herrero, Fernando
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 11.02.2021
• Subjects: CTP; Cytidine triphosphate; Deoxyribonucleic acid; DNA; Magnesium; Nucleotide sequence; Protein interaction; Proteins
• DOI: 10.1101/2021.02.11.430778

parS DNA sequences and the ParB CTPase. Using a combined dual optical tweezers confocal microscope, we observe the specific interaction of ParB with parS directly. Binding around parS is enhanced 4-fold by the presence of CTP or the non-hydrolysable analogue CTPγS. However, ParB proteins are also detected at a lower density in distal non-specific regions of DNA. This requires the presence of a parS loading site and is prevented by roadblocks on DNA, consistent with one dimensional diffusion by a sliding clamp. Magnetic tweezers experiments show that the spreading activity, which has an absolute requirement for CTP binding but not hydrolysis, results in the condensation of parS-containing DNA molecules at low nanomolar protein concentrations. We propose a model in which ParB-CTP-Mg2+ complexes move along DNA following loading at parS sites and protein:protein interactions result in the localised condensation of DNA within ParB networks. Competing Interest Statement The authors have declared no competing interest.