Different localization of SeqA-bound nascent DNA clusters and MukF-MukE-MukB complex in Escherichia coli cells

MukF, MukE and MukB proteins form a complex that may participate in the org anization of folded sister chromosomes in Escherichia coli, We have found t hat a MukB-GFPuv4 fusion protein is observed as discrete fluorescent foci, which are localized within cellular spaces occupied by nucleoids, but not a t the constriction site of cell division in living cells. In contrast, MukB -GFPuv4 is distributed throughout the whole cell when either MukF or MukE i s absent. Statistical analysis revealed that most newborn cells have two fo ci of mukB-gfpUV4 at one-quarter and three-quarter positions in the cell le ngth and one focus of SeqA-bound nascent DNA at or near the middle of the c ell. Subsequently, the single SeqA focus divides into two foci, and then th ese migrate to the one-quarter and three-quarter positions. Before cell div ision, most long cells have two SeqA foci and four MukB-GFPuv4 foci, In ear ly stationary phase, SeqA foci disappear, but one or two foci of MukB-GFPuv 4 remain. We discuss the reorganization and proper arrangement of folded si ster chromosome in the cell quarter positions, which are performed after re lease from the long-time cohesion of sister chromosomes.