MatP delays the segregation of chromosome termini independently of cell division and tetramer formation inVibrio cholerae

Abstract

AbstractThe cellular arrangement and segregation choreography of the genetic material is involved in the timing of assembly and cellular positioning of the cell division apparatus in bacteria. Key to this mode of regulation is the positioning of sister copies of the replication terminus zone (ter) of the chromosomes at the end of the replication cycle. TheVibrio choleraegenome is distributed on two chromosomes, ChrI and ChrII. ChrI is derived from the ancestor of the Vibrionales and Enterobacterales. ChrII is derived from a megaplasmid. ChrI encodes for a homologue of MatP, a protein that tethers sister copies of theterof theEscherichia colichromosome together at mid-cell at the time of cell division. MatP structures theterby binding to ater-specific DNA motif,matS. It forms tetramers that can bridge DNA segments together and it connects sistertercopies to the divisome via an interaction with a cell division protein, ZapB. We find that MatP structures theterof ChrI and ChrII,ter1andter2, and ensures the cohesion and mid-cell position of sisterter1andter2copies at the time of cell division, demonstrating that ChrII is organised and behaves as abona fidechromosome. We show that cohesion and positioning are independent of cell division and tetramer formation, but are linked to the local density ofmatSsites, with sisterter2separating earlier than sisterter1because of a lower number ofmatSsites. Overall, our results suggest that the primary mechanism of action of MatP is to slow down the decatenation of newly replicated molecules.